FR2777297A1 - Transparent or translucent tracing paper for architects, with excellent printing and drawing characteristics - Google Patents

Abstract

On at least one side a layer (2) of solids has been deposited from an aqueous suspension. An Independent claim is included for the method of making the paper. Preferred features: An intermediate protective layer (3) conferring dimensional stability and preventing deformation of the paper during deposition. The structure as described, may be double-sided. The solids are not particularly opaque and are present in small quantities, preferably less than 10 g/m<2>. Their specific area is high, especially exceeding 5 m<2>/m. Suitable solids include porus zeolites, porus silica, miconized silica, sodium aluminosilicate or pyrogenic silica. The layer may include optical brighteners, colorants or decorative additives permitting watered- or iridescent paper finishes. Complementary impressions on either side, form a watermark.

Description

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TRANSPARENT OR TRANSLUCENT PAPER LAYER WITH A

GOOD PRINTABILITY AND ITS MANUFACTURING PROCESS

The present invention relates to a transparent or translucent coated paper which can be used in particular as paper for

printing and / or writing and its manufacturing process.

Transparent or translucent papers are already known which are called tracing papers. These papers are made by suspending long fibers of a pulp in water, in a pulper.

from softwood, 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, namely, numerous fibrils are formed which confer a high affinity of the fibers for water and which make it possible to obtain a transparent or translucent paper. The temperature of the aqueous slurry of fibers is maintained at 80-100 ° C and then the aqueous slurry of refined fibers is deposited on the wire of a flat table paper machine. The water is removed by gravity, then the sheet is pressed to remove residual water and the sheet is then dried between dryer rollers. One such process is the traditional process for obtaining transparent or translucent paper which is used by architects or designers to reproduce an original design. Such paper is intended for use in the field of technical drawing rather than in that of printing and / or writing. However, according to the present invention, it is desired to provide a tracing paper having

very good printability qualities.

Furthermore, non-transparent papers are known which are coated with an aqueous composition containing white opaque fillers and most of the time traditional non-transparent papers are coated with a preparation based on kaolin or

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CaCO3. The coating is done using a coater, on or off the machine, that is to say that the paper is made on a paper machine with a flat table, and after its manufacture it is passed through a coater to coat it on at least one side with a kaolin or CaCO3 layer, and then it is oven dried.

The coating makes it possible to obtain a good quality of printability.

Also known are papers used for lottery tickets which consist of a black paper and coated on the faces with a layer of opaque fillers. We try to make the layer as white as possible and as opacifying as possible to completely cover the black paper and so that the eye can only see the white layer. A large quantity of opaque charges is therefore deposited on the black paper. We want this paper to be as transparent as possible so that the winning numbers printed on the paper and covered with a varnish cannot be read by transparency and

thus avoid fraud.

The inventors therefore had to solve the following problems: to give good printability to a traditional layer, and at the same time

time not to degrade the transparency of the layer too much.

The inventors therefore thought of coating a traditional layer to give it good printability. But those skilled in the art thought that by coating a traditional tracing paper it would significantly reduce its transparency and therefore the inventors had to go against prejudices.

of those skilled in the art.

Furthermore, the person skilled in the art thought that coating a tracing paper with an aqueous suspension was impossible because the tracing paper has a very high sensitivity to water. By coating a tracing paper with an aqueous suspension, the paper curls and undergoes a very strong deformation which it is not then possible to recover and we obtain a

paper warped and not flat.

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On the other hand, a problem with tracing paper is that it has low dimensional stability and in the presence of a high degree of humidity, the tracing paper which has a very high affinity for water, can undergo damage.

longitudinal and transverse dimensional changes.

However, tracing papers are known which have good dimensional stability. These papers are made by laminating two sheets of traditional tracing paper to a sheet of polyester. Such a product has many drawbacks; it is expensive and complicated to manufacture, it is much thicker since it has three laminated sheets, and it is not biodegradable, since it has one sheet

of polyester.

Another object of the invention is therefore to provide a tracing paper having good dimensional stability, which is relatively inexpensive compared to traditional tracing paper and which is

biodegradable.

The inventors therefore thought of depositing a protective layer preventing the paper from deforming. Such a layer is a moisture barrier layer. However, such a layer, which has a film-forming effect, clogs the pores of the tracing paper which already contains little compared to other papers. Clogging of these pores therefore prevents ink from entering the pores and therefore reduces the printability of the layer. The problems which arise are therefore the following: to provide a transparent or translucent paper having both good printability and good dimensional stability and which retains high transparency. After numerous tests, the inventors have therefore developed a transparent or translucent paper having good printability and not being

not deformed and having good dimensional stability.

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The invention therefore relates to a transparent or translucent paper comprises on at least one of its faces a layer obtained by deposition.

on said face of an aqueous suspension of fillers.

The paper may optionally include a protective intermediate layer preventing the paper from deforming during the deposition of said layer of an aqueous suspension of fillers and

providing high dimensional stability.

According to one embodiment of the present invention, the paper comprises on each of its faces a layer obtained by deposition on

said face of an aqueous suspension of fillers.

According to another embodiment of the present invention, the paper comprises on each of its faces a layer obtained by depositing on said face an aqueous suspension of fillers and a protective intermediate layer preventing the paper from deforming and causing it.

providing high dimensional stability.

According to the invention, the fillers are not very opaque and deposited in

small amount, preferably less than 10 g / m2.

The fillers have a high BET specific surface area, preferably

greater than or equal to 5 m2 / g.

Because they have a large specific surface area, they retain inks better in their pores and provide high printability.

to paper, even if they are deposited in small quantities.

These fillers can be chosen from porous zeolites, porous silicas, micronized silicas, precipitated sodium silicoaluminates, pyrogenic silicas, and the like. The layer may optionally include optical brighteners, dyes, or decorative elements such as moiré, iridescence, etc. The invention further relates to a method of manufacturing such

paper.

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According to the invention, a traditional tracing paper is produced which is coated, i.e. a highly refined pulp is suspended in water, the suspension of fibers is placed on a flat table of a paper machine. to form a sheet, the water is removed by gravity then a protective coating is applied in size-press preventing the paper from deforming, the sheet obtained is dried between drying rollers

and an aqueous suspension of fillers is applied outside the machine.

According to another embodiment of the invention, a highly 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 paper is removed. water by gravity, a layer of an aqueous suspension of fillers is deposited on the machine and the sheet obtained is dried between drying rollers. This keeps the paper flat

by passage between the drying rollers.

The following description, with regard to the figures and examples

appended without limitation, will make it possible to understand how the invention

can be put into practice.

Figure 1 is a sectional view of a paper according to the invention

comprising a layer giving it printability.

Figure 2 is a sectional view of a paper according to the invention comprising a barrier layer coated with a layer giving it printability. Figure 3 is a sectional view of a paper according to the invention comprising a layer giving it printability on each of its

faces.

Figure 4 is a sectional view of a paper according to the invention comprising a barrier layer coated with a layer giving it

printability on each of its faces.

Figure 5 is a sectional view of a paper according to Figure 3 which

has prints on its front side and on its back side.

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Figure 6a is a view of a sheet of paper according to the invention,

for example of A4 format, comprising on its face a printed pattern.

Figure 6b is a view of a sheet of paper according to the invention,

having on its other side another printed pattern.

Figure 7 is a view of the sheet of paper according to the invention

printed according to Figures 6a and 6b and seen in transparency.

In Figure 1, there is shown a tracing paper according to the invention which has good printability. This paper is obtained by suspending in water, in a pulper, long fibers of a pulp obtained from coniferous trees, 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 wire 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 high 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 dryer rolls. The paper shown in 1. This paper is then obtained on one of its faces a layer 2 giving it good printability. This layer consists of

fillers having a BET specific surface area greater than 5 m2 / g.

In Figure 2, there is shown a tracing paper 1 on which has been deposited a layer 3 which gives it its dimensional stability and above layer 3, a layer 2 giving it a good

printability. Layer 3 is for example of the polyvinyl alcohol type.

This paper is remarkable because the layer 3 which is a moisture barrier layer does not prevent the deposition and the adhesion of the layer 2 on it, whereas those skilled in the art thought that such a barrier layer would be harmful to the formation of layer 2 conferring printability. Moreover, despite

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the deposition of these two layers, the paper loses little of its transparency. A

such paper has dimensional stability and good printability.

In Figure 3, there is shown a tracing paper 1 which is coated on its two sides respectively with a layer 2 and 2 'which give it good printability on both sides. This paper is remarkable because it retains a large part of its transparency despite the deposition of a layer on each of its faces. In addition, it is printable on each of its sides. Thus, we obtain a printable symmetrical paper

both front and back.

As can be seen in FIG. 5, the paper according to the invention can comprise impressions 4 on one of its faces and impressions 5 on its other side. Because the paper is transparent, provision can be made for the prints 4 to be complementary to the prints 5. Surprising optical effects can thus be obtained. For example, as can be seen in Figure 6a, it is possible to print a half pattern 6 on the face 7 of the paper according to the invention, and a half pattern 8 on the opposite face 9 of this paper. When we look at the paper in reflection, we see with the naked eye the half pattern, either 6 or 8, depending on the side viewed in reflection, respectively 7 or 9. On the other hand, if we look at the paper in transparency as represented by Arrow F1 in Figure 7, we will see the pattern in its entirety. If the printing is carried out with an iridescent, pearlescent or metallic ink, namely a binder comprising an iridescent, pearlescent or metallic pigment, when we look at the pattern 6 or 7 in reflection on the printed side, we see it in iridescent color , pearly or metallic. On the other hand, when viewed in transparency, it appears white because the effect

iridescent, pearly or metallic does not penetrate the paper.

In Figure 4, there is shown a tracing paper 1 on which has been deposited a layer 3 which gives it its dimensional stability and above layer 3, a layer 2 giving it good printability and a layer 3 'which gives it its dimensional stability

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and above layer 3 ′, a layer 2 ′ giving it good printability. This paper is remarkable because it is symmetrical, and therefore printable using standard offset processes, it has great stability.

dimensional and it is transparent.

Comparative Example 1 Long fibers of a paper pulp from coniferous trees were suspended in water in a pulper and 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 wire 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 high 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 dryer rolls. This produces a traditional transparent tracing paper. We note its degree of transparency with the naked eye and we give it a rating of 10. This tracing paper has poor printability. Its degree of printability is rated and it is given a rating of 0. A rating of 10 is taken for the degree of printability, the printability of a white non-transparent coated printing and / or writing paper and as rating 0 for the degree of transparency of the same non-transparent traditional white printing and / or writing paper. Comparative Example 2 A paper is prepared in the same manner as in Comparative Example 1, and an aqueous layer based on

kaolin. The paper curls and is unusable.

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Example 1 According to the Invention A paper is prepared in the same manner as in Comparative Example 1, but an aqueous layer comprising 5% by weight of fillers with a high BET specific surface area is deposited on one side. The deposit is made on the machine. The paper thus obtained does not deform. We note its degree of printability and its degree of transparency. This paper is much more printable than a tracing paper according to the example

comparative 1, and a little less transparent.

Example 2 According to the Invention A paper is prepared in the same manner as in Comparative Example 1, but an aqueous layer comprising 5% by weight of filler with a high BET specific surface area is deposited on one side. A protective layer is deposited beforehand before carrying out the deposition off the machine (for example PVA which waterproofs the paper). The paper thus obtained does not deform. We note its degree of printability and its degree of transparency. This paper is much more printable than a tracing paper according to Comparative Example 1, and a little less transparent.

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Claims (10)

1. Transparent or translucent paper having good printability characterized in that it comprises on at least one of its faces a layer (2) obtained by depositing on said face of an aqueous suspension of loads. 2. Paper according to claim 1, characterized in that it optionally comprises an intermediate protective layer (3) preventing the paper from deforming during the deposition of said aqueous suspension of loads and giving it dimensional stability. 3. Paper according to claim 1 or 2, characterized in that it comprises on each of its faces a layer (2, 2 ') obtained by depositing on said face an aqueous suspension of fillers and an intermediate layer (3, 3 ') protective preventing the paper from deforming when depositing said layer (2,2 ') and giving it dimensional stability. 4. Paper according to any one of the preceding claims, characterized in that the fillers are not very opaque and deposited in small amount, preferably less than 10 g / m2. 5. Paper according to any one of the preceding claims, characterized in that the fillers have a high BET specific surface, preferably greater than or equal to 5 m2 / g. 6. Paper according to any one of the preceding claims, characterized in that the fillers are chosen from porous zeolites, porous silicas, micronized silicas, precipitated sodium silicoaluminates, pyrogenic silicas. 11 2777297 7. Paper according to any one of the preceding claims, characterized in that the layer may optionally comprise optical brighteners, dyes, or decorative elements allowing moiré or iridescence. 8. Paper according to any one of the preceding claims, characterized in that it comprises on one of its faces printed half patterns and on the other face complementary printed patterns, so as to form a complete pattern when the paper is viewed in transparency. 9. A method of making a paper according to any one of claims 1 to 7, characterized in that one suspends in Water a very refined paper pulp, the suspension of fibers is placed on a flat table of a paper machine to form a sheet, the water is removed by gravity and then a protective coating is applied in size-press preventing the paper from deforming, the sheet obtained is dried between drying rollers and a aqueous suspension of charges. 10. A method of making a paper according to any one of claims 1 to 7, characterized in that one suspends in water a highly refined paper pulp, the fiber suspension is placed on a flat table of a paper machine to form a sheet, the water is removed by gravity, a layer of an aqueous suspension is deposited on a machine loads and the sheet obtained is dried between drying rollers, thus keeping the paper flat by passing between the dryer rolls.