FR2771758A1 - TRANSPARENT OR TRANSLUCENT EXTRA WHITE PAPER AND ITS MANUFACTURING PROCESS - Google Patents

Abstract

Transparent or translucid paper has degree of transparency inferior to that of the traditional tracing paper, and a degree of whiteness greater than that of the traditional white copy paper. The paper contains at least an optical dye. An Independent claim is also included for a process for making the paper.

Description

EXTRA WHITE TRANSPARENT OR TRANSLUCENT PAPER AND ITS SOUND

MANUFACTURING PROCESS

  The present invention relates to transparent or translucent paper which is extra white. This paper can be used among other things

  as paper for printing and / or writing.

  We already know transparent or translucent papers which are called tracing papers. These papers are produced by suspending in water, in a pulper, long fibers of a paper pulp from softwoods, by refining the fibers in a refiner. The refiner has two ridged surfaces rubbing against each other and between which the fiber suspension passes. The fibers then undergo a physical transformation, that is to say, numerous fibrils are formed which confer a great affinity of the fibers for water and which make it possible to obtain a transparent or translucent paper. The temperature of the aqueous suspension of fibers is maintained at 80-100 ° C. and the aqueous suspension of refined fibers is then deposited on the canvas of a paper machine with a flat table. The water is removed by gravity, then the sheet is pressed to remove the residual water and the sheet is then dried between drying rollers. One such method is the traditional method for obtaining a transparent or translucent paper which is used by architects or by designers to reproduce an original design. This paper has a grayish color and is not perfectly white. The grayish color is due to the fact that the fiber pulp is refined to the extreme to obtain many fibrils. There is therefore an extreme friction between the metal faces of the refiner and the

  fibers, which gives the greyish color to the tracing paper.

  Tracing papers of the prior art must have a high transparency to allow the reproduction of drawings or plans. However, their whiteness is not an essential characteristic of the fact that they are used as a means of reproduction and therefore that they constitute a temporary support for a design which will be transferred to another paper. In general, the postponement of the plans of architects is done by means of a paper called diazo paper which contains colorless compounds which are colored under the action of ultraviolet rays and a developer based on ammonia. The tracing paper comprising the planes or the drawings is placed on this diazo paper, it is illuminated by UV rays, which forms a latent image on the diazo paper, this latent image corresponding exactly to the drawings or the plans traced on the tracing paper. Then, the latent image is revealed on the diazo paper by means of an ammonia-based developer. It is therefore understood that the tracing paper must absolutely not contain in its composition products liable to interfere with ultraviolet rays. Tracing papers of the prior art must meet strict standards with regard to their composition and must not contain optical brighteners. The object of the present invention is to provide a transparent or translucent paper having a high whiteness, namely greater than that of

  traditional layer of grayish color.

  The object of the present invention is to provide such a transparent or translucent paper having a high whiteness, and usable as paper for printing and / or writing, this paper not being

  intended for the reproduction of plans or drawings.

  To this end, the inventors have produced a transparent or translucent paper which in its composition is different from a traditional tracing paper, namely which contains compounds which do not enter the

  composition of traditional tracing papers.

  The inventors therefore thought of introducing into the paper formed from refined fibers, optical brighteners. These optical brighteners are products intended to increase the whiteness of papers

  non-transparent printing and / or writing.

  However, those skilled in the art thought that the use of bulk optical brighteners would permanently pollute the paper machine. Furthermore, he thought that the size-press deposit of the brightener would be insufficient

  to give a sufficient degree of whiteness to the refined paper.

  The skilled person also wishes, in a traditional way,

  maintain maximum transparency with tracing paper.

  The inventors have therefore made numerous attempts to obtain a transparent paper with a high degree of whiteness. They compared transparent paper to a glass plate and hypothesized that by opacifying

  a transparent glass you can create a whiteness support.

  The inventors therefore reduced the transparency of the paper so that it has a degree of transparency lower than the degree of transparency.

traditional tracing paper.

  The inventors have therefore introduced into the composition of the paper constituents which reduce the transparency of the paper, namely opacifiers. Another way to reduce the transparency of the paper is to refine the fibers less, which helps reduce graying. This results in less transparent and less gray paper than paper

traditional tracing.

  To their surprise, the inventors found that their hypothesis turned out to be correct and that a paper less transparent than a traditional tracing paper to which an optical brightener was added had a higher degree of whiteness than that of the traditional tracing. We actually create a kind of haze in the paper by reducing its transparency, this haze constituting a support for the optical brightener, which means that the quantity of optical brightener necessary to obtain the desired degree of whiteness is low, contrary to prejudice of the skilled person. The invention therefore relates to a printing and / or writing paper, transparent or translucent, characterized in that it has a degree of transparency less than the degree of transparency of a traditional tracing paper and a degree of whiteness greater than the degree whiteness of a layer

  traditional and in that it comprises at least one optical brightener.

  Again, it should be noted that the paper according to the invention is not intended for the reproduction of plans or drawings, but is intended in particular for printing and / or writing. It can also be used for printing slip sheets in advertising or presentation brochures, etc. or as decoration paper

  used for its light transparency properties.

  The paper according to the invention is such that it comprises an opacifier chosen from the group formed by opaque mineral or organic fillers, such as for example TiO2, CaCO3, talc, kaolin, ground melamine-formaldehyde resins, of the genus PERGOPAK (brand

  registered and available from Martinswerke, Germany).

  According to another characteristic of the paper of the invention, it consists of fibers less refined than what is considered to be

  necessary to obtain a traditional tracing paper.

  The paper according to the invention contains from 0 to 10% of opacifier and

less than 10% optical brightener.

  Optical brighteners are derivatives of stilbene, for example brighteners like LEUCOPHOR (registered trademark of SANDOZ) or

  BLANKOPHOR (registered trademark of BAYER).

  The invention further relates to a method of manufacturing such paper. According to the invention, a slightly refined paper pulp is suspended in water, the fiber suspension is placed on a flat table of a paper machine to form a sheet, the water is removed by gravity and then dried. the sheet obtained between drying rollers and finally a solution of at least one brightener is deposited

  optic on the surface of the sheet, for example by means of a sizepress.

  According to another embodiment of the process of the invention, a slightly refined pulp is suspended in water, at least one opacifier is introduced into the aqueous suspension, the fiber suspension is placed on a flat table d '' a paper machine to form a sheet, the water is removed by gravity and then the sheet obtained is dried between drying rollers, and finally a solution of at least one optical brightener is deposited on the surface of the sheet, by

example using a size-press.

  The optical brightener can be introduced in bulk or at the surface.

  The inventors have in fact found that the refining of the pulp, even if it is less than the refining usually carried out for a traditional tracing paper, allows an excellent fixing of the brightener on the cellulose fibers, which allows its introduction in bulk , preferably just before the headbox. This reduces pollution of the

paper machine.

  The following description, with reference to the examples appended as

  non-limiting, will make it possible to understand how the invention can be implemented

in practice.

  Comparative Example 1 Long fibers of a pulp from softwoods are suspended in water in a pulper, and they are refined in a refiner. The temperature of the aqueous suspension of fibers is maintained at a temperature of 80-100 C. Then, the aqueous suspension of fibers is deposited on the canvas of a paper machine with a flat table, the water is removed by gravity. The relatively high temperature of the aqueous suspension is necessary to remove water by gravity, the fibers having a great affinity for water, due to the presence of many fibrils. Then the sheet is pressed to remove the residual water. The sheet is then dried between drying rollers. We then obtain a transparent traditional tracing paper. Note its degree of transparency with the naked eye and give it a rating of 10. This tracing paper is grayish in color. We measure the degree of whiteness with the naked eye and give it a rating of 0. We take as rating 10 for the degree of whiteness, the whiteness of a white non-transparent traditional printing and / or writing paper and as a rating 0 for the degree of transparency of the same

  white non-transparent printing and / or traditional writing paper.

  Comparative Example 2 A paper is prepared in the same manner as in Comparative Example 1, and a 20% by weight aqueous solution of a LEUCOPHOR optical brightener from SANDOZ is deposited in size-press. We note its degree of whiteness which is 2 in comparison with a white non-transparent printing and / or writing white paper and its degree of transparency which is 10 in comparison with a traditional tracing paper. Comparative Example 3 A paper is prepared in the same manner as in Comparative Example 1, and an aqueous solution at 30% by weight of a LEUCOPHOR optical brightener from SANDOZ is deposited in size-press. We note its degree of whiteness and its degree of transparency. The results are

given in the following table.

  Example 1 according to the invention A paper is prepared in the same manner as in Comparative Example 1, but the fibers are refined less and introduced into the

  suspension 6% by weight of LEUCOPHOR optical brightener from SANDOZ.

  We note its degree of whiteness and its degree of transparency. This paper is much less transparent than tracing paper according to the example

  comparative 1, but much whiter.

  Example 2 according to the invention A paper is prepared in the same manner as in Comparative Example 1, but 6% by weight of LEUCOPHOR optical brightener from SANDOZ and 6% by weight of calcium carbonate are introduced into the aqueous suspension. We note its degree of whiteness and its degree of transparency. This paper is much less transparent than tracing paper according to Comparative Example 1, but still a little greyish because of

  that the fibers are very refined.

  Example 3 according to the invention A paper is prepared in the same manner as in Example 2, but the fibers are refined less. We note its degree of whiteness and its degree of transparency. This paper is much less transparent than a

  tracing paper according to Comparative Example 1, and much whiter.

  TABLE Example No. Degree of whiteness Degree of transparency Comparative example 1 0 10 Comparative example 2 2 10 Comparative example 3 3 10 Example 1 4 8 Example 2 6 6 Example 3 8 5 white paper for printing and / or writing 10 0

Claims (10)

  1. Transparent or translucent paper, characterized in that it has a degree of transparency lower than the degree of transparency of a traditional layer and a degree of whiteness greater than the degree of whiteness of a layer   traditional and in that it comprises at least one optical brightener.   2. Paper according to claim 1, characterized in that it comprises an opacifier chosen from the group formed by opaque fillers mineral or organic.   3. Paper according to claim 1, characterized in that it comprises an opacifier chosen from the group formed by TiO2, CaCO3, talc, kaolin,   crushed melamine-formaldehyde resins.   4. Paper according to any one of the preceding claims,   characterized in that it consists of significantly less refined fibers   than the fibers of a traditional tracing paper.   5. Paper according to any one of the preceding claims,   characterized in that it contains from 0 to 10% opacifier and less than 10 % optical brightener.   6. Paper according to any one of the preceding claims,   characterized in that the optical brighteners are derivatives of stilbene.   7. A method of manufacturing a paper according to any one of   previous claims, characterized in that one puts in   a paper pulp suspension in water, the fiber suspension is deposited on a flat table of a paper machine to form a sheet, the water is removed by gravity and then the sheet obtained is dried between drying rollers and what we introduce a bulk optical brightener,   preferably immediately after the headbox.   8. A method of manufacturing a paper according to any one of   Claims 1 to 6, characterized in that one suspends in   water a paper pulp, the fiber suspension is placed on a flat table of a paper machine to form a sheet, water is removed by gravity and then the sheet obtained is dried between drying rollers and   what an optical brightener is introduced on the surface.   9. A method of manufacturing a paper according to claim 8, characterized in that one suspends in water a slightly refined paper pulp, the fiber suspension is deposited on a flat table of a machine paper to form a sheet, the water is removed by gravity and then the sheet obtained is dried between drying rollers, and finally a solution of at least one optical brightener is deposited on the surface of the leaf.   10. A method of manufacturing a paper according to claim 8, characterized in that a slightly refined paper pulp is suspended in water, at least one opacifier is introduced into the aqueous suspension, the suspension of fibers on a flat table of a paper machine to form a sheet, the water is removed by gravity then the sheet obtained is dried between drying rollers, and finally a solution of at least one optical brightener is deposited on the surface of the sheet.