EP0395539B1 - Process for obtaining a high-gloss base and the base so produced - Google Patents

Abstract

- Papermaking. <??>- The base comprises, on at least one face: - a first coat of a conventional coating slip deposited at a rate of 3 to 25 g/m<2>, - at least one superposed coat deposited at a rate of 1 to 10 g/m<2> and based on conventional pigments, at least one conventional binder and gloss pigments in a proportion of at least 20 % of parts by weight of the traditional pigment charge and corresponding to a particle size of between 0.05 and 1 micrometre and, preferably, close to 0.5 micrometre. <??>- Application to the production of a high-gloss paper.

Description

The present invention relates to the technical field of stationery and it relates, more particularly, to the production of special papers comprising, on at least one side, a coating intended to give them particular characteristics.

The invention relates, more particularly, among these so-called special papers, those having a high gloss character and intended to be used for printing, in particular in the advertising field.

The current trend is to be able to have so-called high-gloss papers, in the sense that they have, on at least one side, a gloss at least equal, or even, preferably, greater than 85%.

In an attempt to obtain such papers, at least two preparation techniques are known.

The first, known under the name of coating on chrome or "cast coating", consists of scrolling the paper strip to be treated on a chrome cylinder, perfectly polished and heated which it partially surrounds, after having been taken care of by two deflection rollers.

Just before its wrapping on the chromed and heated cylinder, the paper strip is coated, on its internal face, in particular by injection, with a coating layer or sauce including, in addition to traditional pigments, special binders and adjuvants intended to preserve to the layer a certain malleability during its contact with the chromed cylinder and to facilitate the separation between this last and the layer.

The spread sauce is distributed, pressed and heated, between the paper and the chrome cylinder, so as to undergo, simultaneously with its spreading, a kind of calendering and simultaneous drying.

Suitable results can be obtained with running speeds between 0 and 50 or 100 m / min. This requirement for a limited running speed corresponds to the need to have, beyond the cylinder, a paper which is sufficiently dry for it to be able to be peeled off from the chrome-plated cylinder.

Such a technique is therefore penalized by a low production speed requiring, in addition, a special installation to ensure the winding of the paper strip, the permanent heating of the chromium cylinder of expensive manufacture and the injection of the coating sauce.

Such a technique is further penalized by the difficulty of being able to produce a high-gloss paper on two sides. Indeed, during the coating of the second face, the evacuated vapor must, necessarily, pass through the paper and the layer of the first coated face. This vapor, during its evacuation, deteriorates the layer of the first face and does not make it possible to obtain a suitable second face, due to the braking imposed on the evacuation of the vapor by the need to pass through the paper and the first layer filed.

Such a technique is, moreover, also known for not allowing the coating, under suitable conditions, of a support other than paper and, more particularly, of a support made of plastic, due to the non-permeability of such a material.

A second technique consists in depositing, by traditional coating, with a trailing blade for example, a sauce on one face of a support by composing the coating sauce so as to include in it a suitable proportion of plastic pigments also called gloss pigments in following this memo and made up of spherical particles whose average diameter is between 0.05 and 1 micrometer and, preferably, close to 0.5 micrometer.

In such a technique, the coating takes place over a sufficient thickness, generally between 3 and 25 micrometers, so as to be able to have a resistant layer capable of being suitably calendered.

After calendering and due to the dispersion of the gloss pigments in the thickness of the layer, it is observed that a gloss characteristic is obtained, which is certainly manifest, but does not reach the 80% or 85% sought, even with of levels of gloss pigments as high as 30% by dry weight relative to the total charge of pigments used in the composition of the coating sauce.

One might think that to achieve this characteristic it suffices to increase, in the necessary proportions, the load of plastic pigments incorporated in the coating sauce. Such an intellectual approach, if it may seem obvious initially, is in fact practically not possible for two reasons.

The first is due to the very high cost that should be agreed for the composition of the coating sauce, because of the high price of the plastic pigments to be incorporated.

The second is that by proceeding in this way, we notice, during calendering, a very harmful side effect and unexpected. Indeed, the layer containing a high proportion of plastic pigments, generally greater than 30% by dry weight relative to the total charge of pigments, if it compacts very easily during calendering, suffers a loss of harmful opacity in it -same but which results, moreover, in a defect in appearance on the surface, analogous to the defect in appearance commonly called sealing in the paper industry. Such sealing corresponds to the appearance of a more or less heterogeneous gray tint which comes from a sort of vitrification of the paper. Such a drawback is unacceptable for the production of high-gloss white or pastel-colored papers, but also of dark shades.

A third technique, disclosed by patent US-A-4 248 939 , relates to a process for double coating of a paper, in which a first layer exclusively consisting of traditional mineral pigments and binders is applied to the surface of the paper. . This first layer, deposited at a rate of approximately 3 g / m² by conventional coating, with a dragging blade, is coated, after drying, with a second layer, at a rate of 0.5 to 0.9 g / m². The composition of this second layer is characterized by the exclusive presence of pigments of organic shine in the total pigment load.

The paper is then calendered under normal conditions.

This technique does not achieve gloss values at least equal to 80-85%.

In addition, it suffers from the drawbacks linked to the presence of excessive amounts of organic gloss pigments in the upper layer and mentioned above in the description of the second technique of the prior art (cost, sealing).

All in all, therefore, current techniques do not make it possible to obtain a paper or a high-gloss support in the sense that it is characterized by a gloss at least equal to 80 or 85% and, above all, do not provide any teaching making it possible to conduct the Tradesman on a path capable of filling this gap and solving the problem thus posed.

The object of the present invention is precisely to overcome this difficulty by proposing a new method for obtaining a high-gloss support, such a support being able to be a paper but also, indifferently, a substrate, such as a strip or a film. of plastic.

The method of the invention also makes it possible, if necessary, to treat the two faces of the same substrate, using the same operating phases, possibly offset in time, if a method is considered processing by continuous scrolling.

To achieve the above objectives and others which follow from the thesis which follows, the method of the invention is characterized by the implementation of the successive operating phases defined in claim 1.

• une première couche ou précouche comprenant des pigments traditionnels et, éventuellement, des pigments de brillance à base de polymères ou copolymères organiques, déposée à raison de 3 à 25 g/m²,
• au moins une couche superposée, dite supérieure, formée d'une sauce déposée à raison de 1 à 10 g/m² et à base de pigments traditionnels de granulométrie d'au moins 60 % inférieure à 2 micromètres, d'au moins un liant traditionnel en quantité suffisante et de pigments de brillance à raison d'au moins 20 % en poids sur sec de la charge totale de pigments de cette couche supérieure et répondant à une granulométrie comprise entre 0,05 et 1 micromètre et, de préférence, voisine de 0,5 micromètre.

The subject of the invention is also, as a new industrial product, a high-gloss support, with a gloss at least equal to 80 or 85%, characterized by the existence of a substrate comprising, on at least one face:

• a first layer or pre-layer comprising traditional pigments and, optionally, gloss pigments based on organic polymers or copolymers, deposited at a rate of 3 to 25 g / m²,
• at least one superimposed layer, called the upper layer, formed of a sauce deposited at a rate of 1 to 10 g / m² and based on traditional pigments with a particle size of at least 60% less than 2 micrometers, of at least one traditional binder in sufficient quantity and of gloss pigments at a rate of at least 20% by dry weight of the total charge of pigments of this upper layer and corresponding to a particle size between 0.05 and 1 micrometer and, preferably, close to 0.5 micrometer.

Various other characteristics will emerge from the description given below which shows, by way of nonlimiting examples, embodiments of the subject of the invention.

The process for obtaining a high-gloss support according to the invention consists in using a substrate in sheet, film, plate, of relatively thin thickness, generally close to 100 micrometers. Such a substrate is described, preferably in the following, as being a paper of traditional manufacturing, for example with a grammage of 80 g / m² having possibly undergone a size press treatment during its manufacture. However, the invention applies, under exactly the same conditions, to any substrate of different material and, in particular, to a polyester film.

In a first example of implementation, the first operational phase of the process consists in depositing, on at least one of the faces of the substrate, a coating sauce, of traditional composition in stationery, at a rate of 3 to 25 g / m² , more particularly from 8 to 15 g / m² and, preferably, around 10 g / m². The coated sauce is said to be traditional by its composition, pigments, binders and additives conventionally used. A reservation must be made in the sense of the term "traditional", because of the desire to choose, in all cases, a composition that must meet different imperatives to assume the functions assigned to it. Among these functions, it should be mentioned that of attachment support by constituting a prelayer for subsequent layers, that of being as white as possible, that of being of low cost and that of having the ability filling in surface differences, usually presented by paper.

So that the above functions can be carried out under the best conditions, the coating sauce comprises conventional pigments including, preferably, kaolin, pigments corresponding, for at least 60% of them, to a particle size less than 2 micrometers. Preferably, the pigments chosen have, for at least 90% of them, a particle size of less than 2 micrometers.

Among the conventional pigments, mention should be made, for example, of calcium carbonates, kaolins, talcs, calcium sulfates, silicoaluminates, satin whites, silicas, aluminas and aluminum hydroxides.

The composition of the coating sauce also comprises, in a traditional manner, suitable binders so that the layer assumes the above functions, binders among which mention should be made of synthetic latexes, starch, polyvinyl alcohol, proteins.

In this first example, the coating sauce is free of gloss pigments. This sauce is deposited to form a precoat regularly covering, in a homogeneous and uniform manner, the support face. This precoat is deposited, by any suitable means known in the art, for example with a trailing blade.

After coating, the precoat undergoes a natural or forced drying phase, followed, if necessary, by a calendering phase carried out using traditional stationery means but, preferably, at a higher temperature than room temperature to facilitate subsequent production. of shine. This temperature can be between ambient and 150 ° C., for example between 80 and 100 ° C. Calendering can be carried out with a pressure of 0 to 300 kg per linear centimeter.

After depositing the precoat, the method according to this first implementation provides for the deposition of at least one so-called gloss layer, at a rate of 1 to 10 g / m², preferably at a rate of 3 g / m². The gloss layer is formed from a coating sauce based on traditional pigments, of the type described in relation to the previous precoat. The constituent sauce of the so-called gloss layer incorporates, however, gloss pigments in an amount of at least 20% by weight of the pigment charge of the gloss layer. The gloss pigments are chosen to have a particle size between 0.05 and 1 micrometer and, preferably, close to 0.5 micrometer. Among the products which are particularly suitable in the intended application, mention should be made of acrylic styrene copolymers, such as, in particular, the product sold under the brand Ropaque® by the company ROHM and HAAS or, again, polystyrenes, such as products marketed under the LYTRON ® brand by the company WILLIAMS.

Particularly remarkable results are obtained by constituting the sauce of the gloss layer from traditional pigments of which at least 60% of them, and preferably 90% of them, have a particle size of less than 2 micrometers. The gloss layer is deposited by traditional coating method, also preferably with a dragging blade, then undergoes traditional or forced drying followed by conventional calendering at usual temperature. This temperature is preferably as high as possible to improve the gloss, but it must not exceed 105 ° C., in order to avoid adhesion of the layer to the rollers of the calender. Calendering is carried out at conventional pressures, for example of the order of 100 to 300 kg per linear centimeter.

Unexpectedly, the constitution of an overall layer, by proceeding as said above, by depositing a precoat followed by at least one gloss layer, makes it possible to obtain, from a substrate of the type of that specified above, a brightness characteristic close to 85%. This characteristic is obtained without the effect of graying or sealing, by globally involving only a small proportion of plastic pigments of gloss deemed to be of a high cost price.

Results, particularly surprising and advantageous, are obtained by depositing, on the precoat of the type described above, two superimposed layers, called gloss, of similar composition and deposited by coating under the same conditions. In such a case, it is possible to lower the proportion of gloss pigments in each of the layers, while obtaining the desired result. Suitable results have been obtained by providing at least 15% by dry weight of gloss pigments relative to the total charge of pigments of the layer considered for the first superimposed layer and at least 20% by dry weight for the second layer called superior.

In some cases, it may be advantageous to compose the gloss layer from 30% by dry weight of gloss pigments, 20% by dry weight of kaolin relative to the total charge of pigments of the layer in question, of which at least 98% preferably corresponds to a particle size of 2 micrometers, and of traditional pigments and binders in sufficient quantity complementary.

In certain cases, in particular, when the precoat does not contain kaolin, it can be envisaged to compose the layer, known as gloss, from 30% by dry weight of gloss pigments and a complement to 100% of pure kaolin, such a composition being supplemented by ordinary binders and additives provided in a proportion which may be between 4 and 20 parts by dry weight per 100 parts by dry weight of pigments.

In the examples given above, the total mass of pigments included in the layer considered should be considered as a reference base, for the% by dry weight in traditional pigments or in gloss pigments.

Due to the implementation of a traditional coating process it becomes possible, when desired, to treat, as said previously or differently, the two faces of the same substrate, either in completely different operating phases and delocalized, either, again, in successive or simultaneous operating phases in the event of continuous treatment of a strip of great length.

Obtaining a high gloss characteristic, from a low incorporation of gloss pigments included in the second gloss layer, makes it possible to produce papers with sought-after characteristics for a particularly attractive cost price, involving only a traditional process and a material known for its implementation.

According to a variant of the process, a first layer is deposited on the substrate intended to assume the function of prelayer and the function of first gloss layer. To this end, a layer of 5 to 20 g / m² and preferably 10 g / m² is deposited on the substrate, according to usual conditions. traditional composition including a proportion of less than 15% by dry weight of gloss pigments relative to the total charge of pigments of said layer then, after drying and optional calendering, at a rate of approximately 4 g / m², one second layer including 20% by dry weight of gloss pigments relative to the total charge of pigments of this second layer. This second layer is dried and calendered and the substrate thus treated is characterized by a gloss close to 87%.

Various examples of implementation of the process of the invention are given below.

EXAMPLE 1 :

• . Etape 1 :
  Dans un premier temps, ce support a été couché sur la face 1 avec une coucheuse à lame traînante avec la sauce de couchage suivante :
  • 60 parties en poids (sec/sec) de carbonate de calcium naturel broyé Hydrocarb 90® fabriqué par la Société OMYA et caractérisé par une granulométrie de 90 % < 2 micromètres,
  • 40 parties en poids (sec/sec) de kaolin HT commercialisé par la Société ENGELHARD,
  • 10 parties en poids de latex synthétique DL 670 de la Société DOW CHEMICAL FRANCE,
  • 0,3 parties en poids (sec/sec) de carboxyméthylcellulose de moyenne viscosité 7 M1 de la Société HERCULES,
  • la quantité nécessaire d'eau pour obtenir une préparation à 65 % de teneur en matières solides,
  • la quantité d'ammoniaque nécessaire pour obtenir un pH de 9,5.
  Le poids de couche déposé a été de 12 g/m² sur la face 1.
• . Etape 2:
  Ce papier a été couché une deuxième fois sur la même face 1, à la lame traînante avec une formulation de couchage de composition suivante :
  • 30 parties en poids (sec/sec) de pigment organique synthétique Ropaque OP 84® de la Société ROHM et HAAS,
  • 70 parties en poids (sec/sec) de kaolin fin (98 % < 2 micromètres) Amazon 88® commercialisé par la Société EUROCLAY,
  • 16 parties en poids (sec/sec) de latex synthétique Acronal® 360 D de la Société BASF,
  • 0,5 partie en poids (sec/sec) de carboxyméthylcellulose 7 M1 de la Société HERCULES,
  • la quantité d'eau nécessaire pour obtenir une préparation avec une teneur en matières solides de 51 %,
  • la quantité nécessaire d'ammoniaque pour obtenir un pH de 9,5.
  Le poids de couche déposé a été de 4,5 g/m².
• . Etape 3 :
  Ce papier a ensuite été caLandré dans les conditions habituellement utilisées pour obtenir des papiers brillants ordinaires (brillances de l'ordre de 65 %).
  Le papier obtenu avait les caractéristiques suivantes :
  

A standard paper support was used, consisting, for example, of 50% long softwood fibers and 50% short hardwood fibers and coated with starch in press size during its manufacture and characterized by the following tests:

• . Step 1 :
  Initially, this support was coated on side 1 with a dragging coater with the following coating sauce:
  • 60 parts by weight (dry / dry) of calcium carbonate natural crushed Hydrocarb 90 ® manufactured by OMYA and characterized by a particle size of 90% <2 micrometers,
  • 40 parts by weight (dry / dry) of kaolin HT marketed by the ENGELHARD Company ,
  • 10 parts by weight of synthetic latex DL 670 from the company DOW CHEMICAL FRANCE,
  • 0.3 parts by weight (dry / dry) of carboxymethylcellulose of medium viscosity 7 M1 from the company HERCULES,
  • the necessary amount of water to obtain a preparation with a 65% solids content,
  • the amount of ammonia required to obtain a pH of 9.5.
  The layer weight deposited was 12 g / m² on side 1.
• . Step 2 :
  This paper was coated a second time on the same side 1, with a dragging blade, with a coating formulation of the following composition:
  • 30 parts by weight (dry / dry) of Ropaque OP 84 ® synthetic organic pigment from the company ROHM and HAAS,
  • 70 parts by weight (dry / dry) of fine kaolin (98% <2 micrometers) Amazon 88 ® sold by the company EUROCLAY ,
  • 16 parts by weight (dry / dry) of Acronal ® 360 D synthetic latex from BASF,
  • 0.5 part by weight (dry / dry) of carboxymethylcellulose 7 M1 from the company HERCULES,
  • the amount of water required to obtain a preparation with a solids content of 51%,
  • the necessary amount of ammonia to obtain a pH of 9.5.
  The layer weight deposited was 4.5 g / m².
• . Step 3 :
  This paper was then calendered under the conditions usually used to obtain ordinary glossy papers (glosses of the order of 65%).
  The paper obtained had the following characteristics:
  

EXAMPLE 2 :

• 50 parties en poids (sec/sec) de pigment organique synthétique Ropaque OP 84® de la Société ROHM et HAAS,
• 50 parties en poids (sec/sec) de kaolin fin (98 % < 2 micromètres) Amazon 88® commercialisé par la Société EUROCLAY,
• 16 parties en poids (sec/sec) de latex synthétique Acronal 360 D® de la Société BASF,
• 0,5 partie en poids (sec/sec) de carboxyméthylcellulose 7 M1 de la Société HERCULES,
• la quantité d'eau nécessaire pour obtenir une préparation avec une teneur en matières solides de 51 %,
• la quantité nécessaire d'ammoniaque pour obtenir un pH de 9,5.

Le poids de couche déposé a été de 4,5 g/m².The paper of example 2 was manufactured with the same support and with the same steps 1 and 3 as for example 1. In step 2, the following coating formulation was used:

• 50 parts by weight (dry / dry) of synthetic organic pigment Ropaque OP 84 ® from the company ROHM and HAAS,
• 50 parts by weight (dry / dry) of fine kaolin (98% <2 micrometers) Amazon 88 ® sold by the company EUROCLAY ,
• 16 parts by weight (dry / dry) of Acronal 360 D ® synthetic latex from BASF,
• 0.5 part by weight (dry / dry) of carboxymethylcellulose 7 M1 from the company HERCULES,
• the amount of water required to obtain a preparation with a solids content of 51%,
• the necessary amount of ammonia to obtain a pH of 9.5.

The layer weight deposited was 4.5 g / m².

The paper obtained had the following characteristics:

EXAMPLE 3 :

• . Etape 2 :
  Le papier a été couché une deuxième fois sur la même face 1, à la lame traînante avec une formulation de couchage de composition suivante :
  • 20 parties en poids (sec/sec) de pigment organique synthétique Ropaque OP 84® de la Société ROHM et HAAS,
  • 80 parties en poids (sec/sec) de kaolin fin (98 % < 2 micromètres) Amazon 88® commercialisé par la Société EUROCLAY,
  • 16 parties en poids (sec/sec) de latex synthétique Acronal 360 D® de la Société BASF,
  • 0,5 partie en poids (sec/sec) de carboxyméthycellulose 7 M1 de la Société HERCULES,
  • la quantité d'eau nécessaire pour obtenir une préparation avec une teneur en matières solides de 51 %,
  • la quantité nécessaire d'ammoniaque pour obtenir un pH de 9,5.
  Le poids de couche déposé a été de 3 g/m².
• . Etape 3 :
  Ce papier a été couché une troisième fois sur la même face et avec la même formulation que dans l'étape 2.
  Le poids de couche déposé a été de 2,5 g/m².
• . Etape 4 :
  Elle a consisté à calandrer le papier dans les mêmes conditions que celles des exemples 1 et 2.
  Le papier obtenu avait les caractéristiques suivantes :
  

The paper of Example 3 was made from the same support and with the same first step as that of Examples 1 and 2.

• . Step 2 :
  The paper was coated a second time on the same side 1, with a dragging blade, with a coating formulation of the following composition:
  • 20 parts by weight (dry / dry) of synthetic organic pigment Ropaque OP 84 ® from the company ROHM and HAAS,
  • 80 parts by weight (dry / dry) of fine kaolin (98% <2 micrometers) Amazon 88 ® sold by the company EUROCLAY ,
  • 16 parts by weight (dry / dry) of Acronal 360 D ® synthetic latex from BASF,
  • 0.5 part by weight (dry / dry) of carboxymethylcellulose 7 M1 from the company HERCULES ,
  • the amount of water required to obtain a preparation with a solids content of 51%,
  • the necessary amount of ammonia to obtain a pH of 9.5.
  The layer weight deposited was 3 g / m².
• . Step 3 :
  This paper was coated a third time on the same side and with the same formulation as in step 2.
  The layer weight deposited was 2.5 g / m².
• . Step 4 :
  It consisted in calendering the paper under the same conditions as those of Examples 1 and 2.
  The paper obtained had the following characteristics:
  

EXAMPLE 4 :

• . Etape 1 :
  Dans un premier temps, ce support a été couché sur la face 1 avec une coucheuse "Gate roll" avec la sauce de couchage suivante :
  • 100 parties en poids (sec/sec) de carbonate de calcium naturel broyé Hydrocarb 90® fabriqué par la Société OMYA et caractérisé par une granulométrie de 90 % < 2 micromètres,
  • 30 parties en poids (sec/sec) d'amidon préalablement cuit dans les conditions standards,
  • 0,4 parties en poids (sec/sec) d'azurant optique Leucophor® CK de la Société SANDOZ,
  • la quantité nécessaire d'eau pour obtenir une préparation à 53,5 % de teneur en matières solides.
  Le poids de couche déposé a été de 9 g/m² sur la face 1.
• . Etape 2 :
  Ce papier a été couché une deuxième fois sur la même face 1, à la lame traînante avec une formulation de couchage de composition suivante :
  • 50 parties en poids (sec/sec) de pigment organique synthétique Ropaque OP 84® de la Société ROHM et HAAS,
  • 50 parties en poids (sec/sec) de kaolin HT commercialisé par la Société ENGELHARD,
  • 16 parties en poids (sec/sec) de latex synthétique Baysthal® P 1 700 de la Société BAYER,
  • 0,7 partie en poids (sec/sec) de carboxyméthylcellulose 7 L2C de la Société HERCULES,
  • 0,85 parties en poids (sec/sec) d'azurant optique Leucophor CK® de la Société SANDOZ,
  • la quantité d'eau nécessaire pour obtenir une préparation avec une teneur en matières solides de 51 %,
  • la quantité nécessaire d'ammoniaque pour obtenir un pH de 9,5.
  Le poids de couche déposé a été de 4,5 g/m².
• . Etape 3 :
  Le papier a été calandré dans les mêmes conditions que pour les exemples 1, 2 et 3.
  Le papier obtenu avait les caractéristiques suivantes :
  

We used a standard support with wood that was not coated in size press during its manufacture and characterized by the following tests:

• . Step 1 :
  At first, this support was coated on side 1 with a "Gate roll" coater with the following coating sauce:
  • 100 parts by weight (dry / dry) of ground natural calcium carbonate Hydrocarb 90 ® manufactured by the company OMYA and characterized by a particle size of 90% <2 micrometers,
  • 30 parts by weight (dry / dry) of starch previously cooked under standard conditions,
  • 0.4 parts by weight (dry / dry) of Leucophor ® CK optical brightener from the company SANDOZ ,
  • the necessary amount of water to obtain a preparation with a 53.5% solids content.
  The layer weight deposited was 9 g / m² on side 1.
• . Step 2 :
  This paper was coated a second time on the same side 1, with a dragging blade, with a coating formulation of the following composition:
  • 50 parts by weight (dry / dry) of synthetic organic pigment Ropaque OP 84 ® from the company ROHM and HAAS,
  • 50 parts by weight (dry / dry) of kaolin HT marketed by the company ENGELHARD ,
  • 16 parts by weight (dry / dry) of Baysthal® P 1 700 synthetic latex from the company BAYER ,
  • 0.7 part by weight (dry / dry) of carboxymethylcellulose 7 L2C from the company HERCULES ,
  • 0.85 parts by weight (dry / dry) of Leucophor CK ® optical brightener from the company SANDOZ ,
  • the amount of water required to obtain a preparation with a solids content of 51%,
  • the necessary amount of ammonia to obtain a pH of 9.5.
  The layer weight deposited was 4.5 g / m².
• . Step 3 :
  The paper was calendered under the same conditions as for Examples 1, 2 and 3.
  The paper obtained had the following characteristics:
  

EXAMPLE 5 :

• . Etape 1 :
  Dans un premier temps, ce support a été couché sur la face 1 avec une coucheuse à lame traînante avec la sauce de couchage suivante :
  • 50 parties en poids (sec/sec) de carbonate de calcium naturel broyé Hydrocarb 90® fabriqué par la Société OMYA et caractérisé par une granulométrie de 90 % < 2 micromètres,
  • 40 parties en poids (sec/sec) de kaolin HT commercialisé par la Société ENGELHARD,
  • 10 parties en poids (sec/sec) de pigment organique synthétique Ropaque OP 84® de la Société ROHM et HASS,
  • 10 parties en poids de latex synthétique DL 670 de la Société DOW CHEMICAL FRANCE,
  • 0,3 parties en poids (sec/sec) de carboxyméthylcellulose de moyenne viscosité 7 M1 de la Société HERCULES,
  • la quantité nécessaire d'eau pour obtenir une préparation à 65 % de teneur en matières solides,
  • la quantité d'ammoniaque nécessaire pour obtenir un pH de 9,5.
  Le poids de couche déposé a été de 12 g/m² sur la face 1.
• . Etape 2 :
  Ce papier a été couché une deuxième fois sur la même face 1, à la lame traînante avec une formulation de couchage de composition suivante :
  • 20 parties en poids (sec/sec) de pigment organique synthétique Ropaque OP 84® de la Société ROHM et HAAS,
  • 80 parties en poids (sec/sec) de kaolin fin (98 % < 2 micromètres) Amazon 88® commercialisé par la Société EUROCLAY,
  • 16 parties en poids (sec/sec de latex synthétique Acronal 360 D® de la Société BASF,
  • 0,5 partie en poids (sec/sec) de carboxyméthylcellulose 7 M1 de la Société HERCULES,
  • la quantité d'eau nécessaire pour obtenir une préparation avec une teneur en matières solides de 51 %,
  • la quantité nécessaire d'ammoniaque pour obtenir un pH de 9,5.
  Le poids de couche déposé a été de 4,5 g/m².
• . Etape 3 :
  Ce papier couché a ensuite été calandré dans les conditions habituellement utilisées pour obtenir des papiers brillants ordinaires (brillances de l'ordre de 65 %).
  Le papier obtenu avait les caractéristiques suivantes :
  
  

The same support was used as for Examples 1, 2 and 3.

• . Step 1 :
  Initially, this support was coated on side 1 with a dragging coater with the following coating sauce:
  • 50 parts by weight (dry / dry) of ground natural calcium carbonate Hydrocarb ® 90 manufactured by OMYA Company and characterized by a particle size 90% <2 microns,
  • 40 parts by weight (dry / dry) of kaolin HT marketed by the ENGELHARD Company,
  • 10 parts by weight (dry / dry) of synthetic organic pigment Ropaque OP 84 ® from the company ROHM and HASS ,
  • 10 parts by weight of synthetic latex DL 670 from the company DOW CHEMICAL FRANCE,
  • 0.3 parts by weight (dry / dry) of carboxymethylcellulose of medium viscosity 7 M1 from the company HERCULES,
  • the necessary amount of water to obtain a preparation for 65% solids content,
  • the amount of ammonia required to obtain a pH of 9.5.
  The layer weight deposited was 12 g / m² on side 1.
• . Step 2 :
  This paper was coated a second time on the same side 1, with a dragging blade, with a coating formulation of the following composition:
  • 20 parts by weight (dry / dry) of synthetic organic pigment Ropaque OP 84 ® from the company ROHM and HAAS,
  • 80 parts by weight (dry / dry) of fine kaolin (98% <2 micrometers) Amazon 88 ® sold by the company EUROCLAY ,
  • 16 parts by weight (dry / dry of Acronal 360 D ® synthetic latex from BASF ,
  • 0.5 part by weight (dry / dry) of carboxymethylcellulose 7 M1 from the company HERCULES ,
  • the amount of water required to obtain a preparation with a solids content of 51%,
  • the necessary amount of ammonia to obtain a pH of 9.5.
  The layer weight deposited was 4.5 g / m².
• . Step 3 :
  This coated paper was then calendered under the conditions usually used to obtain ordinary glossy papers (glosses of the order of 65%).
  The paper obtained had the following characteristics:
  
  

The table below gives the comparative values of printing tests carried out identically on papers according to Examples 1 to 5 and on standard reference paper.

The invention is not limited to the examples described and shown, since various modifications can be made thereto without departing from its scope.

Claims (14)

1. Method for obtaining a high gloss base paper, of the type consisting in applying on a substrate a first coat or base coat containing pigments conventionally used in the papermaking industry, with optionally gloss pigments based on organic polymers or copolymers,
      characterized in that the first coat is applied in the proportion of 3 to 25 g/m2, and in that, after drying and optional calendering of the first coat, at least one overcoat called gloss coat of a coating slip is applied on said first coat in the proportion of 1 to 10 g/m2, which gloss coat is composed of conventional pigments of granulometry at least 60% smaller than 2 um, at least one conventional binder in sufficient quantity and gloss pigments in the proportion of at least 20% by dry weight of the total quantity of pigments contained in said overcoat and having a granulometry ranging between 0.05 and 1 um and being preferably around 0.5 um, and the thus treated substrate is calendered.
2. Method according to claim 1, characterized in that it consists in applying on the first coat at least two superposed gloss coats, of similar conventional composition, the first one containing at least 15% by dry weight of gloss pigments with respect to the total quantity of pigments contained in this first coat, and the second one, called overcoat, containing at least 20% by dry weight of the same pigments with respect to the total quantity of pigments.
3. Method according to claim 1 or 2, characterized in that at least one gloss coat is applied on the base coat, which gloss coat contains 20% by dry weight of kaolin with respect to the total quantity of pigments contained in said gloss coat, of granulometry at least 98% smaller than 2 um.
4. Method according to claim 1 or 2, characterized in that at least one gloss coat is applied on the base coat, which gloss coat is composed of 30% by dry weight of gloss pigments, and as conventional pigments, 70% by dry weight of kaolin with respect to the total quantity of pigments contained in said gloss coat, said kaolin having a granulometry of at least 98% smaller than 2 um, as conventional pigments, with an adequate quantity of binders.
5. Method according to any one of claims 1 to 4, characterized in that the first coat or base coat contains no gloss pigments.
6. Method according to claim 1, 3 or 4, characterized in that it consists in applying on the substrate a first coat in the proportion of about 10 g/m2 which contains from 0 to 15% by dry weight of gloss pigments with respect to the total quantity of pigments contained in said first coat, and a second coat in the proportion of about 4 g/m2 which contains about 20% by dry weight of gloss pigments with respect to the total quantity of pigments contained in said second coat.
7. Method according to one of claims 1 to 6, characterized in that at least one gloss coat is applied on the base coat, which gloss coat contains 4 to 20 parts by dry weight of conventional binders and additives for 100 parts by dry weight of pigments.
8. High gloss base paper of the type comprising a substrate of which one face at least is coated with a first coat or base coat containing conventional pigments and optionally gloss pigments based on organic polymers or copolymers,
      characterized in that the first coat is applied in the proportion of 3 to 25 g/m2, and in that said base paper comprises, at least one superposed coat, called overcoat, of a coating slip applied in the proportion of 1 to 10 g/m2 and containing conventional pigments of granulometry at least 60% smaller than 2 um, at least one conventional binder in sufficient quantity and gloss pigments in the proportion of at least 20% by dry weight of the total quantity of pigments contained in said overcoat and having a granulometry ranging between 0.05 and 1 um and being preferably around 0.5 um.
9. High gloss base paper according to claim 8, characterized in that it comprises at least two superposed gloss coats, one called overcoat comprising at least 20% by dry weight of gloss pigments with respect to the total quantity of pigments contained in said overcoat, the other called intermediate coat comprising at least 15% by dry weight of gloss pigments with respect to the total quantity of pigments contained in this intermediate coat.
10. High gloss base paper according to claim 8 or 9, characterized in that it comprises a first coat containing no gloss pigments and at least one gloss coat.
11. High gloss base paper according to claim 8 or 9, characterized in that it comprises a first coat applied in the proportion of about 10 g/m2 and containing between 0 and 15% by dry weight of gloss pigments with respect to the total quantity of pigments contained in said first coat, and a second coat applied in the proportion of about 4 g/m2 containing about 20% by dry weight of gloss pigments with respect to the total quantity of pigments contained in said second coat.
12. High gloss base paper according to one of claims 8 to 11, characterized in that the gloss coat contains about 20% by dry weight of kaolin with respect to the total quantity of pigments contained in said gloss coat, of granulometry at least 98% smaller than 2 um.
13. High gloss base paper according to one of claims 8 to 12, characterized in that the gloss coat contains 30% by dry weight of gloss pigments, and as conventional pigment, 70% by dry weight of kaolin with respect to the total quantity of pigments contained in said gloss coat, said kaolin having a granulometry of at least 98% smaller than 2 um.
14. High gloss base paper according to one of claims 1 to 13, characterized in that the gloss coat comprises between 4 and 20 parts by dry weight of conventional binder and additives for 100 parts by dry weight of pigments.