KR100711374B1 - Durability-reinforced security documents and method for manufacturing the same - Google Patents

Abstract

Treating the base paper with a surface treatment solution containing polyvinyl alcohol, a modified urea resin and a catalyst, treating the base paper treated with the surface treatment solution with a curing solution, and drying the base paper treated with the curing solution. Disclosed is a method of manufacturing a security paper having enhanced durability, including. The surface treatment process is performed with a new surface treatment solution in which a modified urea resin and a catalyst are added to a polyvinyl alcohol aqueous solution, which is a conventional surface treatment solution, to enhance fiber-polymer bonding strength to improve physical resistance. The surface treatment liquid used in the present invention may further include a water and oil repellent agent, thereby improving contamination resistance by performing a surface treatment process with a surface treatment liquid further containing a water and oil repellent agent. The method according to the present invention can increase the shelf life of the security paper by improving the physical resistance and contamination resistance of the security paper such as banknotes without deterioration of printability.

Durability, pollution resistance, modified urea resin, water and oil repellent

Description

Durable-reinforced security documents and method for manufacturing the same

The present invention is a durable security paper and a method of manufacturing the same, more specifically, by using a surface treatment liquid containing polyvinyl alcohol, modified urea resin and catalyst to form a strong bonding structure between the fibers and polymers to wet with water No strong physical deformation even when strong external force is applied, and optional surface water repellent agent is added to the surface treatment solution to improve the resistance to contaminants such as oil and dirt. It relates to a paper and a manufacturing method thereof.

As a way to improve the shelf life of security papers such as banknotes, in Switzerland and the Netherlands, varnish is applied to the surface of banknotes to improve the shelf life of security papers by 10-30% .In Australia, banknotes are made of plastic polymer. By manufacturing, the shelf life of four times the paper banknote is improved.

The prior art for improving the shelf life of a general paper banknote is as follows.

U.S. Patent No. 5,660,919 discloses a method for producing a paper having excellent printability and distribution durability, including fillers such as bentonite and clay, water-soluble polyurethanes, acrylate copolymers, and optionally carboxylated S / B ( A method of treating at least one side of a paper with a coating liquid containing an elastomeric binder such as a styrene-butadiene copolymer is disclosed. This method relates to the surface treatment and the composition of the impregnating liquid for simultaneously providing print aptitude and distribution durability such as offset printing and intaglio printing in the production of security papers with improved quality of printing as well as high quality printing. The binder disclosed in the US patent may be used alone or in combination with a general paper binder. Coating methods can be reverse roll, champion, bill-blade, air knife coater, etc. The coating amount is about 10 g / m ² at the time of drying. Since the US patent has a pigment, there is a problem that security elements such as silver or silver wire present in the security paper become opaque.

WO0220902 discloses a method for producing a security paper having excellent printability and durability, and, unlike the US patent, relates to a technique for treating a transparent coating liquid, not a pigment coating liquid, on at least one side of the paper. The transparent coating solution is composed of colloidal silica and polyurethane. This method has the disadvantage of requiring a separate coating equipment.

Korean Patent Laid-Open Publication No. 1998-7002528 describes a method of improving the durability of a security paper requiring tear resistance, sewage resistance, physical resistance and washing resistance by treating transparent coating liquid on both sides of the paper. The transparent coating solution is composed of a polyurethane or urethane-acryl blend or a mixture of these and a crosslinking agent such as polyaziridine. The most suitable time for treating the transparent coating liquid is when the paper is treated after the surface treatment and before reaching the after-drying part, when the paper is still wet, and it is disclosed that it is possible even after the paper is completely dried. The paper thus produced reduces the surface porosity and roughness, thereby increasing the paper's sewage resistance, significantly improving the wet and dry durability and washing resistance, and having no effect on printability.

Korean Patent Laid-Open Publication No. 2001-0071507 describes that the main factor determining the life span of banknotes is contamination on the surface of banknotes due to porosity, and for the improvement thereof, polyamide lacquer, acrylate or binder with high acrylate content is used. The technique which improved the contamination resistance by forming a transparent protective layer on the surface by apply | coating alone or with a crosslinking agent is disclosed. The transparent protective layer is processed during the paper making process in the paper machine, or by printing or coating after making the paper.

Korean Patent Laid-Open Publication No. 2004-0040478 relates to a technique for improving the distribution cycle through the edge reinforcement method, which regards the main cause of the limited circulation cycle of the banknote as the initial tearing at the edge of the banknote. The edge reinforcement method is a hardened or treated with a lacquer, such as S / B latex, two-component polyurethane and acrylic latex on the edge by knife coating, screen printing or flexographic printing method, or a transparent foil made of polyester It is a method of purchasing a synthetic fiber such as cotton fiber or polypropylene fiber, which is specially treated or placed on the edge of the bar after cutting.

Prior arts related to improving the shelf life of the security paper (bank note) mentioned above are mostly intended to improve the stain resistance on the surface rather than the physical resistance of the security paper. However, in order to improve the shelf life of the security paper, not only the stain resistance on the surface should be improved, but also the physical resistance to damage such as wrinkles, friction, and tearing of the security paper is basically required.

In addition, the prior art requires additional equipment such as coating apparatus. Therefore, there is a need for the development of a method that can obtain the aforementioned characteristics by using existing equipment without the investment of additional equipment such as coating equipment.

The present invention has been made to solve the above problems, and an object of the present invention is to perform a surface treatment process using a new surface treatment solution in which a modified urea resin and a catalyst are added to a polyvinyl alcohol aqueous solution which is a conventional surface treatment solution. It is to provide a method for manufacturing a security paper that can produce a durable security paper without deterioration of printability without additional coating equipment.

Another object of the present invention is to provide a security paper produced by the above method.

In order to achieve the object of the present invention, a method of manufacturing a security paper having enhanced durability includes treating a raw paper with a surface treatment liquid containing polyvinyl alcohol, a modified urea resin, and a catalyst, and treating the base paper with the surface treatment liquid. Treating with a curing liquid, and drying the base paper treated with the curing liquid.

A broad surface treatment process is divided into a narrow surface treatment process and a hardening process. The surface treatment liquid used in the narrow surface treatment process includes polyvinyl alcohol, modified urea resins, and a catalyst.

The modified urea resin used in the present invention is a modified urea resin that does not produce free formaldehyde. Urea resin refers to various compounds having an N-methylol group obtained by reacting cyclic urea formed with the reaction of urea and glyoxal with formaldehyde. The urea resin can be crosslinked with cellulose and is widely used to impart washing resistance in the textile industry. Since the urea resin enters formaldehyde during the production of the urea resin, free formaldehyde may be generated when combined with cellulose. However, free formaldehyde should not be detected in the security sheet according to the present invention. Therefore, in the present invention, a modified urea resin which does not generate free formaldehyde is used without using urea resin such as dimethylol dihydroxy ethylene urea which produces free formaldehyde. Any modified urea resin that does not produce free formaldehyde can be used in the present invention without any limitation. For example, there is dimethyl dihydroxy ethylene urea (trade name Fixapret NF) manufactured by BASF.

The content of the modified urea resin in the total surface treatment liquid is 1 to 10% by weight, preferably 3 to 5% by weight. The content of the modified urea resin is excellent in durability enhancement effect within the above range.

In the present invention, an ammonium salt such as NH ₄ HSO ₄ or the like, an amine salt such as HOCH ₂ CH ₂ NH ₂ · HCL or the like, or a metal salt such as MgCl ₂ or ZnCl ₂ may be used as a catalyst. The catalysts are characterized in that they dissolve and appear acidic on their own or by heat. The content of the catalyst is 0.1 to 1 of the content of the modified urea resin.

The temperature of the surface treatment liquid used for surface treatment of the base paper is preferably 60 to 70 ° C. In the above temperature range, the surface treatment liquid can easily penetrate into the paper.

After the surface treatment step for the base paper is finished, the base paper is treated with a curing liquid.

At this time, examples of the curing liquid that can be used include borax and boric acid. The reason for carrying out the curing step is to improve the strength such as tensile strength, and to prevent the surface treatment liquid from melting when the paper is wet with water.

After the curing liquid treatment step, the base paper is dried. As for a drying temperature, 100 minutes or more and 3 minutes or more of drying time are preferable.

As a dryer which can be used for a drying process, there are a cylinder dryer and a short wavelength infrared (IR) dryer, etc., It is preferable to use a short wavelength infrared (IR) dryer from the point that drying is performed within a short time.

The surface treatment liquid may further include a water and oil repellent agent. The content of the water and oil repellent agent in the total surface treatment liquid is preferably 0.5 to 3% by weight. As the content of the water and oil repellent is less than 0.5% by weight, the effect of fouling resistance is insignificant, and as more than 3% by weight, there is a problem of impairing the printability. Usable water and oil repellents include fluorine-based water and oil repellents.

The fiber length of the base paper used for this invention is 1.2-1.3 mm in length. This is longer than 0.8 to 1.0 mm, which is the length of ordinary fibers, and is an appropriate value that does not impair deterioration or process conditions.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited thereto.

Production example of the base paper

The bleached cotton fiber was beaten with a beaker at a concentration of 3.5% by weight up to 28 ° SR, and then refined with a refiner to 55 ° SR to prepare a stock. At this time, the fiber length was 1.23 mm. Wetland was prepared after diluting to 0.2% by weight by adding water to the stock. The wetland was subjected to a compression and drying process to prepare a base paper.

Example 1

To the aqueous polyvinyl alcohol solution dissolved at 6% by weight, 5% by weight of modified urea resin (BASF, Fixapret NF) and 0.5% by weight of MgCl ₂ metal salt catalyst (BASF, Condensol N) were added to prepare a surface treatment solution. While maintaining the surface treatment solution at 65 ± 3 ° C., the base paper produced in the preparation example was impregnated in the surface treatment solution for 10 seconds, and then the excess was removed using a compression press. Thereafter, the base paper was impregnated in a borax solution having a concentration of 5% by weight for 5 seconds, and then the excess was removed by using a compression press. The coating amount was set to about 6 g / m ² on a dry basis. The treated base was dried for 3 minutes at a surface temperature of 100 ° C. using a cylinder dryer.

Example 2

In aqueous polyvinyl alcohol solution dissolved in 7% by weight, 5% by weight of modified urea resin (BASF, Fixapret NF), 0.5% by weight of MgCl ₂ metal salt catalyst (BASF, Condensol N), water and oil repellent (ACECEM, fluorine-based water repellent) A water treatment oil) was added 1% by weight to prepare a surface treatment liquid. While maintaining the surface treatment solution at 65 ± 3 ° C., the base paper produced in the preparation example was impregnated in the surface treatment solution for 10 seconds, and then the excess was removed using a compression press. Thereafter, the base paper was impregnated with a borax solution having a concentration of 5.5% by weight for 5 seconds, and then the excess was removed using a compression press. The coating amount was set to about 6 g / m ² on a dry basis. The treated base was dried for 3 minutes at a surface temperature of 100 ° C. using a cylinder dryer.

Example 3

It carried out similarly to Example 1 except having dried for 2 minutes using the infrared (IR) dryer.

Comparative Example 1

While maintaining the polyvinyl alcohol aqueous solution dissolved at 6% by weight at 45 ± 3 ℃ impregnated the base paper produced in the manufacturing example in the polyvinyl alcohol aqueous solution for 10 seconds, the excess was removed using a compression press. The base paper was impregnated in 5 wt% borax solution for 5 seconds and then excess was removed using a press. The coating amount was set to about 6 g / m ² on a dry basis. The treated base was dried for 3 minutes at a surface temperature of 100 ° C. using a cylinder dryer.

Comparative Example 2

Maintain the polyvinyl alcohol solution dissolved at 7.0% by weight at 45 ± 3 ° C and impregnate the paper for 10 seconds, remove excess by using a compression press, and impregnate the borax solution at 5.5% by weight for 5 seconds. In the same manner, the excess was removed so that the coating amount was about 6 g / m ² on a dry basis. The treated base was dried for 3 minutes at a surface temperature of 100 ° C. using a cylinder dryer.

The security paper produced as above was evaluated using the following method.

Paper property

The security papers prepared in Examples and Comparative Examples were subjected to humidity control for 24 hours at 20 ° C. and 65% of conditions, and then tensile strength and fracture resistance were measured based on KS M 7014 and KS M 7068, respectively.

Dry pollution

Tumbler was used as a device for evaluating dry contamination. Samples were prepared in the size of banknote measures, punched at four corners, and prepared by mounting rubber weights. As a medium for transferring contaminants, 2000 g of glass beads having a diameter of 2 mm were used, and contaminants used were 0.4 g of carbon black, 0.4 g of olive oil, and 0.4 g of ethanol. 2000g glass beads were put in a 2L plastic barrel and carbon black was added and shaken sufficiently. Then, olive oil and ethanol were added and shaken again. The contaminants thus prepared were placed in a tumbler and stirred for 5 minutes. Twenty samples to be evaluated for contamination were put in a tumbler and subjected to contamination experiments at 15 rpm clockwise, 15 minutes counterclockwise, and 60 rpm. After the stop of the tumbler, the sample was taken out, the rubber weight was removed, and each sample was wiped three times with a wet towel, and then three times with a dry towel and dried. The evaluation of pollution degree was compared by measuring the difference in whiteness before and after contamination according to ISO 2470.

Wet durability

Three-dimensional mixer (TURBULA) was used for the evaluation of wet durability. Samples were prepared by cutting them into bank-sized measures and then wrinkling them four times using a creasing test apparatus and mounting them on a cuboid-shaped specimen holder. Contaminants consist of artificial sweat, color powder and grease. Put a total of four samples, standard specimens, two specimen holders in a 2L barrel, 25 ceramic beads of 2cm in diameter, and finally put contaminants for 5, 10, and 15 minute contamination experiments at 67 rpm. Was carried out. In this evaluation, the time taken for the specimen to survive without breaking was measured.

Tensile Strength (kgf / 15mm) Wet Tensile Strength (kgf / 15mm) Surge strength (times) Wet Durability (min) Dry stain resistance (△ whiteness) Comparative Example 1 12.5 2.7 3723 5 14.0 Comparative Example 2 13.0 2.8 3689 5 13.9 Example 1 12.7 4.3 3825 15 13.5 Example 2 13.2 4.4 3742 15 7.5 Example 3 12.6 4.3 3810 15 13.5

According to the measurement results of the physical properties of Table 1, the security paper according to Examples 1, 2 and 3 has a large difference from the security paper according to Comparative Examples 1 and 2 in terms of dry tensile strength and cut resistance. It can be seen that it is not shown. However, in the wet tensile strength, the security paper according to Examples 1, 2 and 3 was found to be considerably superior to the security paper according to Comparative Examples 1 and 2. In other words, by treating with a surface treatment liquid containing a modified urea resin, the wet tensile strength was increased without deteriorating other physical properties.

In the wet durability evaluation, the security papers according to Examples 1, 2 and 3 were not broken even at the contamination time of 15 minutes, while the security papers according to Comparative Examples 1 and 2 were tolerated up to 5 minutes. It was destroyed. This too, the wet durability is greatly improved by the application of the deformable urea resin.

As a result of the dry pollution resistance evaluation, it can be seen that the security paper according to Example 2 has a much smaller whiteness difference before and after contamination compared to the security paper according to Comparative Examples 1 and 2, and the resistance to contamination is considerably improved.

 As described above, the present invention performs surface treatment with a surface treatment liquid containing polyvinyl alcohol, modified urea resins and catalysts, and optionally a water and oil repellent agent, thereby enhancing durability without additional coating equipment or coating of special chemicals. And a paper with improved stain resistance can be produced.

While specific embodiments of the present invention have been described above, the present invention is not limited to the above-described specific embodiments, and the technical field to which the present invention pertains without departing from the gist of the present invention as claimed in the claims. Anyone of ordinary skill in the art can make various modifications, as well as such modifications are within the scope of the claims.

Claims (13)

Treating the base paper with a surface treatment liquid containing polyvinyl alcohol, a modified urea resin, and a catalyst; Treating the base paper treated with the surface treatment solution with borax or boric acid as a curing solution; And And drying the treated paper with the curing liquid. Wherein the content of the deformable urea resin is 1 to 10% by weight in the total surface treatment liquid, and the content of the catalyst is 0.1 to 1 of the content of the modified urea resin. The method of claim 1, wherein the modified urea resin is a modified urea resin that does not detect free formaldehyde in the security paper. The method of claim 1, wherein the catalyst is an ammonium salt, an amine salt, or a metal salt. delete delete The method of claim 1, wherein the temperature of the surface treatment liquid is 60 to 70 ° C. delete The method according to claim 1, wherein in the drying step, a drying temperature is 100 ° C. or more and a drying time is 3 minutes or more. The method of claim 1, wherein the drying step is performed by using a cylinder dryer or a short-wave infrared (IR) dryer. The method of claim 1, wherein the surface treatment liquid further comprises a water and oil repellent agent. 11. The method of claim 10, wherein the content of the water / oil repellent agent is 0.5 to 3% by weight in the total surface treatment liquid. The method of claim 1, wherein the fiber length of the base paper is 1.2 to 1.3 mm. A security paper produced by the method according to any one of claims 1 to 3, 6, or 8 to 12.