JP2005513282A - Coated paper with silk feel - Google Patents

Abstract

The present invention relates to a coating composition for coated paper for offset printing, wherein the coating dye is an ultrafine powder of polyurethane having a size of less than 10 micrometers, and preferably close to 7 micrometers. The present invention relates to a coating composition. The invention also relates to a coated paper having a silky feel, wherein the coating composition is applied on at least one side and advantageously on both sides. This paper is characterized in that it can be offset printed with little or no setback or choking.

Description

  The present invention relates to a coating composition comprising ultra-fine polyurethane powder and to paper coated with the coating composition on at least one side, preferably on both sides.

  It can be applied to various types or compositions of paper to improve its surface quality.

  Conventionally used coating compositions for this purpose are dispersions containing pigments that can be organic or inorganic.

  The coating composition can also contain other additives.

  Paper for printing, such as books, magazines, brochures or annual reports, or packaging paper, is applied to the underlying paper by one or several units of coating and sometimes manufactured by subsequent gloss processing Often done.

  The final product must generally have improved surface properties for its use.

  These surface properties are generally reflected in changes in the appearance of the paper due to its whiteness, its brightness, or even its opacity.

  Exploring the feel of the layered paper surface is new enough in itself.

  In the earlier French patent invention 2791368, the applicant provides a wrapping paper containing features that are reminiscent of one of the essential features of the product to be packaged, especially for cosmetics to be applied to the skin. Was interested in.

  Therefore, the applicant has proposed to provide features that are reminiscent of the target skin, i.e., the feel and softness of the skin.

The desired tactile sensation has been obtained by applying a layer containing expandable thermoplastic ultrafine powder to the surface of the paper.
French Patent Invention No. 2791368

  This patent seeks to solve the problem of machinability of these papers during printing, particularly the problem that stacked papers break apart due to the anti-slip properties of the added ultrafine powder.

  In general, coated thin papers often cause serious problems during printing or during processing, most commonly in the case of offset printing: choking and setback.

  Choking is a phenomenon that corresponds to delamination in the form of a dry powder during printing and can increase as the paper is continuously passed through a printing or processing machine.

  This phenomenon is due to an inadequate binder / dye formulation where the ratio of dye to binder is too large.

  It can also be attributed to the size and shape of the pigment particles.

  The set-off is that the printing of the paper moves to another, especially when stacked.

  As described above, ink stains of various densities derived from the ink on the surface of the lower paper are often observed on the back surface of the paper.

  When breaking the stack, you can hear the noise of paper of various strengths.

  When this phenomenon is small, it is called setback.

  When a paper element is involved in peeling, it is a dot.

  When the sheets can no longer be separated from each other, it is adhesion by stacking.

  Paper that is not compatible with ink may have poor ink acceptance, and paper with an irregular surface condition may require excess ink for accurate printing, so paper may be involved in this phenomenon.

  In view of these points, Applicants have endeavored to provide paper that is preferably coated on both sides, has silk feel and does not exhibit the printability and machinability problems described above. .

  Accordingly, a first object of the invention is offset printing, characterized in that the dye used in the layer is an ultrafine polyurethane powder having an average size of less than 10 micrometers, and preferably close to 7 micrometers. An object of the present invention is to provide a coating composition for coated paper.

  In particular, the invention is preferably characterized in that the binder used in the layer is an aqueous polyurethane emulsion, preferably a flexible polyurethane having an elongation of 500% or more.

  In particular, the present invention is characterized in that the ratio of the binder to the dye is 40% or more by dry weight, and preferably 200% or more.

  Another object of the present invention is to provide a coated paper having a silky feel, coated on at least one side, and advantageously on both sides, with the coating composition described above.

  The paper is characterized in that it can be offset printed with less or no set-off or choking.

The paper is mainly composed of cellulose fibers, and the weight per unit area is comprised between 70 and 500 g / m ² , preferably between 100 and 300 g / m ² .

  In certain cases, the paper is transparent or translucent.

  More particularly, the paper constitutes tracing paper.

  Tracing paper is paper as defined in point 6.94 of the international standard ISO 4046-1978.

  More specifically, the present invention is characterized in that the paper is a tracing paper, particularly a tracing paper obtained by highly refining the cellulose fibers constituting the paper.

In particular, the present invention is characterized in that the weight of the layer on at least one surface is between 2 to 10 g / m ² in dry weight, preferably is comprised between 3 to 6 g / m ² .

  When the paper was measured according to the standard NF-Q-03-082 using 200 g of sliding pieces, the dynamic friction coefficient between the coated back surface and the other back surface was 1. It is also characterized by being 0 or less.

  The dynamic coefficient of friction indicates the suitability of the paper to catch when trying to move; the higher the coefficient, the more difficult it is to start moving the stacked paper.

  Comparative and non-limiting examples of embodiments of the present invention and, in some cases, other advantages are described below.

Examples 1-5:

^On a medium paper having a weight per unit area of 100 g / m ² , more specifically on the number CONQUEROR CX22 marketed by the applicant, an air blade coater is used at a rate of about 5 g / m ² per surface. As shown in Table 1, a composition containing ultrafine polyurethane powders having different sizes is applied.

A composition comprising ultrafine polyurethane powder is realized in an aqueous solvent and in dry weight:
24.7 parts water 0.1 parts wetting agent 33.3 parts polyurethane aqueous emulsion Witcobond 290H
20 parts polyurethane ultrafine powder 0.5 parts pH adjuster 1 part thickener.

  Examples 6-13:

Using an air blade coater on a medium paper having a weight per unit area of 100 g / m ² , more specifically, the number CONQUEROR CX22 marketed by the applicant, the weight of the dye is as shown in Table 2. Varying the proportion of binder, a composition containing ultrafine polyurethane fines with an average size close to 7 micrometers is applied at a rate of about 5 g / m ² dry per surface.

A composition comprising ultrafine polyurethane powder is realized in an aqueous solvent and in dry weight:
・ Aqueous emulsion of various parts of polyurethane Rolflex PAD
20 parts polyurethane ultra fine powder Dailacoat RHU 5070
Contains 0.5 parts pH adjustor. 1 part thickener.

Implementation of test-The touch of the surface having the ultrafine powder layer of polyurethane is evaluated by hand.

  Measure the response of the blank paper to the choking test to determine the tendency of the layer to peel when passed through the machine.

The choking test is conducted as follows:
a) A piece of 40 mm × 40 mm, 2 kg weight coated with the above layer, covered with cloth-like black felt (70% wool, 30% polyamide blend) Put it on several sheets of paper,
b) Pass only once over the paper so as to cover the total length of 6 m c) Remove the felt of the slip piece d) Measure the felt reflectivity using the ELREPHO device (value measured with sackcloth is about 1.4) )

Measure the response of the printed paper to the set-off test to determine the tendency of the paper to cause set-off during machine stacking. The set-up test is carried out as follows:
a) Producing a test piece of paper to be tested having a width of 48 mm and a length of 250 mm b) Using a PRUFBAU testing machine having a first printing stand and a second printing transfer stand c) The pressure of the first stand is set to 1000 N Adjust the pressure of the two units to 400 N d) Adjust the machine speed to 0.5 m / sec e) Ink the first ink roller with HUBBER 408010 type blue ink for 30 seconds f) Remove the test piece Place the transported machine in front of the first machine g) Place the roller without ink on the second machine h) Print the test piece on the first machine i) Start the stopwatch immediately after printing j) Place the same paper specimen on the second new roller with adhesive tape. K) After 120 seconds on the stopwatch, insert the transporter with the printed specimen to the blanket site. I) Immediately pull the second test piece away from its roller m) Measure the optical density of the cyan transferred to the new test piece using a density meter XRITE.

result:
The test results of Examples 1 to 5 are shown in Table 1.

  As can be seen, it is possible to obtain an acceptable silk feel of ultrafine powder less than 10 micrometers, even though most papers are almost satisfactory in response to setback and choking tests. Only size.

  It can be concluded from the test results of Examples 6 to 13 that after selecting the size of the ultrafine powder that makes it possible to obtain the desired silk feel, then 40% or more to obtain an accurate choking. Also, it is necessary to select a binder ratio of 200% or more in order to obtain an accurate setback.

  In fact, it is judged that choking is less than 2 and set-off is less than 0.1.

  FIGS. 1 and 2 show a paper having a silk tactile sensation from the applicant's point of view as seen with a scanning electron microscope.

This paper has the following layer composition on both sides of a CONQUEOR CX22 media paper having a weight per unit area of 100 g / m ² :
2.8 kg of water 0.03 kg of wetting agent TEXAPON Z95P
81 kg LAMBERTI's commercially available binder ROLFLEX PAD
6.1 kg of polyurethane fine powder DAIPLACOAT RHU5070 marketed by PROMECOME
1% of AQUALON marketed 2.5% thickener CMC BLANOSE 7M65
Was obtained by adhering 5.4 g / m ² by dry weight per side.

  The resulting paper was then run through a gloss machine.

  Each of the photographs represents a surface magnified 200 times and a cross section magnified 2000 times.

  The resulting paper actually exhibits a silky feel on both sides.

  Using a sliding piece of 200 g, the dynamic friction coefficient of the coated paper was measured according to the standard NF-Q-03-082. As a result, excellent machinability of the paper was guaranteed on the printing machine or processing machine A value of 0.8 is obtained which makes it possible to do so.

The photomicrograph which expanded the surface of the obtained paper 200 times. The photomicrograph which expanded the cross section of the obtained paper 2000 times.

Claims (7)

  In a coating composition for coated paper for offset printing comprising a dye and a binder, the coating dye is an ultrafine polyurethane powder having a size of less than 10 micrometers, and preferably close to 7 micrometers. A coating composition, characterized by being.   The coating composition according to claim 1, characterized in that the binder used is an aqueous emulsion of polyurethane, preferably having an elongation of 500% or more.   The coating composition according to claim 2, wherein the ratio of the binder to the dye is 40% or more by weight, and preferably 200% or more.   A paper having a silky feel, wherein the coating composition according to any one of claims 1 to 3 is applied on at least one side and preferably on both sides.   When measured according to the standard NF-Q-03-082 using a sliding piece of 200 g, the dynamic friction coefficient between the coated back surface and another coated back surface is 1.0 or less. The paper according to claim 4, wherein: 6. The weight of the layer applied to at least one surface is comprised between ² and 10 g / m < ² >, preferably between 3 and 6 g / m < ² > in dry weight. The paper according to any one of the above. The paper according to any one of claims 4 to 6, which is a tracing paper, particularly a tracing paper obtained by highly purifying cellulose fibers constituting the tracing paper.

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