METHOD FOR ACYLATING A HYDROXYLATED SOLID MATERIAL

Abstract

A method for chromatogenic acylation of a solid material carrying hydroxyl groups capable of reacting with fatty acid chlorides in the gaseous state, wherein a reactive fatty acid chloride composition is applied to the surface of the solid hydroxyl material by means of an applicator capable of releasing the composition on the surface of the material. The composition is applied to the surface of the solid hydroxyl material at an acylation temperature lower than the vaporization temperature of at least one fatty acid chloride of the composition to allow acylation of the material by reaction of at least one fatty acid chloride in the gaseous state of the composition with at least one of the hydroxyl groups of the material, the acylation temperature being between 160 C. and 250 C.

Claims

1. A process for the chromatogenic acylation of a solid material bearing hydroxyl groups that are accessible to at least one fatty acid chloride in the gaseous state and that are capable of reacting with this (these) fatty acid chloride(s) in the gaseous state, wherein: at least one composition, referred to as reactive composition, of at least one fatty acid chloride is applied at least on the surface of said hydroxylated solid material by means of at least one applicator device having an application surface formed of filiform elements that are not reactive with said reactive composition and that are able to release said reactive composition at least on the surface of said hydroxylated solid material by contact of the filiform elements and the hydroxylated solid material, said reactive composition applied by the applicator device at least on the surface of said hydroxylated solid material is, during the application thereof, at a temperature, referred to as acylation temperature, below the vaporization temperature of at least one fatty acid chloride of said reactive composition and chosen to enable an acylation of said solid material by reaction of at least one fatty acid chloride in the gaseous state of said reactive composition with at least one of the hydroxyl groups of said solid material, said acylation temperature being between 160 C. and 250 C.

2. The process as claimed in claim 1, wherein at least one application surface portion of the applicator device is in contact with a surface portion of the hydroxylated solid material, at least this surface portion of the hydroxylated solid material is at said acylation temperature during application of said reactive composition to the hydroxylated solid material.

3. The process as claimed in claim 1, wherein the filiform elements forming the application surface are at said acylation temperature during the application of said reactive composition to the hydroxylated solid material.

4. The process as claimed in claim 1, wherein said reactive composition is applied at least on the surface of said hydroxylated solid material, in a thermoregulated chamber suitable for maintaining said reactive composition released by the applicator device at said acylation temperature.

5. The process as claimed in claim 1, wherein the process further comprises at least one step of redistributing fatty acid chloride(s) deposited on the hydroxylated solid material, without a fresh supply of said reactive composition, the redistribution step being carried out by means of at least one distributor device having an application surface formed of filiform elements which are not reactive with the fatty acid chlorides of said reactive composition and are able to be loaded with fatty acid chlorides deposited on the hydroxylated solid material, by contact of the filiform elements of the distributor device with the hydroxylated solid material and in order to release at least some of the loaded fatty acids, in contact with said hydroxylated solid material by contact of the filiform elements with the hydroxylated solid material, the distributor device being at a temperature of between 160 C. and 250 C.

6. The process as claimed in claim 1, wherein at least one reactive composition comprises at least one fatty acid chloride chosen from the group formed of palmitic acid chloride, stearic acid chloride, arachidic acid chloride and behenic acid chloride.

7. The process as claimed in claim 1, wherein the hydroxylated solid material is a paper material.

8. The process as claimed in claim 1, wherein the hydroxylated solid material is formed of a paper web moved in a run direction parallel to the largest dimension of the web, between an upstream reel of said paper web and a downstream take-up roll for a web of acylated paper.

9. The process as claimed in claim 8, wherein at least one reactive composition is applied at fixed station(s) at least on one main face of the moving paper web.

10. The process as claimed in claim 8 or 9, claim 8, wherein at least one applicator device is a roller with an axis of rotation parallel to the plane of the paper web and not parallel to the run direction.

11. The process as claimed in claim 8, wherein the process further comprises at least two applications of reactive composition(s) at fixed stations on the moving paper web, each reactive composition being at said acylation temperature during the application thereof.

12. The process as claimed in claim 8, wherein the solid material is a paper material coated with polyvinyl alcohol.

13. The process as claimed in claim 8, wherein the filiform elements of at least one applicator roller are supplied by centrifugal diffusion of said reactive composition from an axial lumen of this applicator roller rotated upon itself.

14. The process as claimed in claim 13, wherein said reactive composition is introduced into the axial lumen of the applicator roller by means of a bar for distributing said reactive composition over the length of the axial lumen, the distribution bar extending over substantially the entire length of the axial lumen.

15. The process as claimed in claim 8, wherein at least one applicator roller is provided with means for heating said reactive composition to said acylation temperature.

16. The process as claimed in claim 8, wherein a withdrawal of fatty acid chloride(s) on the paper web is carried out using a recovery device having a rotatable recovery surface provided with filiform elements which are not reactive with said reactive composition and are able to:| be loaded with fatty acid chloride(s) by contact of the recovery surface and the paper web, and release fatty acid chloride(s) by applying a flow of gaseous composition heated to a temperature above said acylation temperature, the flow of gaseous composition being applied in contact with the recovery surface.

17. The process as claimed in claim 1, wherein the filiform elements are formed from at least one material chosen from the group formed of aramid fibers and microfibers and inorganic fibers and microfibers.

18. The process as claimed in claim 1, wherein at least one portion of gaseous hydrochloric acid formed due to the chromatogenic acylation is entrained by a flow of a gaseous composition circulating in contact with the solid material, at said acylation temperature.

19. The process as claimed in claim 1, wherein said reactive composition is free of any solvent medium.

Description

[0068] Other objectives, features and advantages of the invention will become apparent on reading the following description which refers to the appended figures and to the examples given solely by way of non-limiting example of the invention, and in which:

[0069] FIG. 1 is an overview diagram illustrating a chromatogenic acylation process known from the prior art (WO2022/033698) and presented solely by way of comparison with a process according to the invention,

[0070] FIG. 2 is an overview diagram illustrating a first embodiment of a chromatogenic acylation process according to the invention,

[0071] FIG. 3 is an overview diagram illustrating a second embodiment of a chromatogenic acylation process according to the invention, and

[0072] FIG. 4 is a schematic representation of a device for implementing an industrial process for the chromatogenic acylation of a width of paper according to the invention.

[0073] The process known from WO2012/066015, for the chromatographic acylation of a paper material comprising the deposition on the paper material of liquid fatty acid chloride by means of a cylinder, referred to as an anilox roll, designed for printing is not satisfactory.

[0074] The paper material obtained by such a known process contains a significant residual amount of free fatty acid chloride, despite the implementation of a final blowing (or flushing) step. Residual fatty acid chloride can decompose by hydrolysis to free fatty acid and hydrochloric acid which can degrade the solid material. In addition, the free fatty acids formed alter the barrier properties of the solid material and the residual fatty acid chlorides pose a toxicity problem for applications in particular in the field of food packaging and in the biomedical field.

[0075] A process for the chromatogenic acylation of a tissue is also known from WO2022/033698. According to this known process, stearic acid chloride is deposited by means of a varnish roller impregnated with stearic acid chloride at room temperature, on one of the faces of the tissue brought to a temperature of 160 C. The amount of stearic acid chloride impregnated on the varnish roller and the amount deposited on the tissue are adjusted by successive applications, without reloading the roller, and depletion of the stearic acid chloride until the optimum amount of acid chloride impregnated on the roller is obtained. The tissue, having received the optimal amount of stearic acid chloride, is then placed in an oven at a temperature of 160 C. Such a known process cannot be applied as is on an industrial scale.

[0076] The known chromatogenic acylation process described above is illustrated in FIG. 1. Such a known process comprises a step 2 of heating a paper material 1 in an oven heated to a temperature, referred to as the acylation temperature, below the vaporization temperature of the fatty acid chloride, but sufficient to allow acylation of the paper material 1 by reaction of a fatty acid chloride 5 in the gaseous state with reactogenic hydroxyls of the paper material 1. In this known process, a hot paper material 6 is formed at said acylation temperature. At the same time, a varnish roller 3 having an application surface formed of a pile 4 is impregnated by rolling 7 in acid chloride 5 in the liquid state at atmospheric temperature under rolling conditions suitable for obtaining a varnish roller 8 in an optimal state of impregnation allowing a deposition of an optimal amount of stearic acid chloride 5 in the liquid state. In this known process, a step 9 of applying stearic acid chloride 5 in the liquid state and at atmospheric temperature to the hot paper material 6 is carried out by rolling the impregnated varnish roller 8 over the hot paper material 6, allowing an acylation of the hot paper material 6 by stearic acid chloride in the gaseous state, at a temperature inevitably below said acylation temperature and the formation of an acylated and hydrophobic material 10. According to this known process, stearic acid chloride at room temperature and essentially in liquid form is deposited on a paper material heated to a temperature sufficient to enable chromatographic acylation of the paper material by stearic acid chloride in the gaseous state which is formed due to the temperature of the paper material.

[0077] An overview diagram of a process according to the invention for the chromatogenic acylation of a solid material 1 bearing hydroxyl groups that are accessible to at least one fatty acid chloride in the gaseous state and that are capable of reacting with this (these) fatty acid chloride(s) is represented in FIG. 2.

[0078] The hydroxylated solid material 1 may be a cellulosic material. The solid material 1 may also be formed of a fabric, in particular a fabric comprising cotton fibers. The solid material 1 may be a paper material 1. That being said, any type of hydroxylated solid material can be used. The hydroxylated solid material 1 may have an uneven surface finish. It may have a high roughness. However, the hydroxylated solid material 1 may also be a materialin particular a calendered paperhaving an even surface finish of low roughness. The hydroxylated solid material 1 may be porous or nonporous. The hydroxylated solid material 1 may be a nonporous material having hydroxyl groups borne by a polymerin particular PVA (polyvinyl alcohol)forming the free surface of the hydroxylated solid material. The hydroxylated solid material 1 may be a paper material rendered nonporous and impermeable to air by surface application of a layer of PVA, as described in FR2925910. The hydroxylated solid material 1 may be a disposable paper tissue formed of a plurality of cellulosic sheets with a grammage of less than 30 g/m.sup.2in particular less than 20 g/m.sup.2, preferably between 10 g/m.sup.2 and 30 g/m.sup.2, more preferentially between 10 g/m.sup.2 and 20 g/m.sup.2. The paper material may be formed of crosslinked cellulose fibers, the rotational mobility of which is restricted, giving the paper material improved properties in terms of mechanical strength in general and wet strength in particular. The cellulose fibers are then bonded together by hydrogen bonds and by covalent bonds formed with at least one group of crosslinking atoms, such as, for example, a 1-chloro-2,3-epoxypropane or epichlorohydrin derivative. The hydroxylated solid material 1 may be a flexible material, i.e. it is deformable under the effect of its own weight. The hydroxylated solid material 1 may be a paper material in the form of a sheet of paper known as paper towel, toilet paper, a paper napkin or a filter paper. The hydroxylated solid material 1 may be a board. It can be rigid, that is, it does not deform significantly under the effect of its own weight. The hydroxylated solid material 1 may be a piece of corrugated board formed from at least one sheet of fluted paper and at least one board sheet with a grammage of greater than 160 g/m.sup.2.

[0079] In the process according to the invention shown in FIG. 2, an applicator device 3 is chosen having an application surface provided with filiform elements 4 which are not reactive with the fatty acid chlorides of a composition, referred to as a reactive composition 20, of at least one fatty acid chloride. Such an applicator device 3 is chosen which is suitable for being able to be subjected to a temperature of between 160 C. and 250 C. without loss of its adsorbent and application functionalities. It may, for example, be an applicator device 3, the applicator face of which is formed of filiform elements 4 of inorganic fibers or microfibers, such as glass fibers or microfibers or carbon fibers or microfibers, or filiform elements 4 of aramid fibers or microfibers, such as aramid fibers or microfibers known under the Kevlar trademark. The applicator device 3 may be an applicator roller, an applicator pad, or an applicator brush provided with the filiform elements 4. The applicator device 3 may have an application surface formed of oleophilic filiform elements 4 (having affinity for fatty substances). Any suitable type of oleophilic material can be used. However, the applicator device 3 may have an application surface formed of oleophobic filiform elements 4. In particular, they may be filiform elements 4 coated with a perfluorinated coating, in particular a Teflon coating. The application surface of the applicator device 3 is formed of a chemically stable material that is resistant to abrasion and temperature, particularly to said acylation temperature. Preferably, the filiform elements have a free end suitable for cooperating with the surface of the hydroxylated solid material by brushing. The applicator device 3 may be a roller, in particular a roller of the varnish roller type and that is suitable for withstanding said acylation temperature, without loss of its adsorbent and application properties. The filiform elements 4 are flexible and suitable for being loaded with fatty acid chloride(s) and for releasing at least one portion of the loaded fatty acid chloride(s), in particular by elastic deformation. The filiform elements 4 may have a length of between 1 mm and 100 mm or more. The filiform elements may have a transverse cross section with a diameter of between 1 m and 1000 m. The applicator device may be a varnish roller, the application surface of which is formed of a pile provided with filiform elements having an implantation density of greater than 10 filiform elements per mm.sup.2 of application surface, in particular of between 50 and 500 filiform elements per mm.sup.2 of application surface. The filiform elements are chosen so as to exhibit, in particular during rotation of the applicator roller, a rigidity imparted by the rotation of the applicator roller, which rigidity is sufficient to allow application of fatty acid chloride(s) over at least one portion of the thickness of the hydroxylated solid material, without damaging it. The filiform elements have a flexibility chosen so as not to damage the hydroxylated solid material, by contact.

[0080] In a process according to the invention, a composition, referred to as reactive composition 20, of at least one fatty acid chloride is chosen or prepared. At least one fatty acid chloride is chosen from the group formed of fatty acid chlorides of formula RCOC in which R is a hydrocarbon chain having a number of carbon atoms of between 13 (limit included) and 29 (limit included), in particular between 15 (limit included) and 29 (limit included). At least one fatty acid chloride is chosen from the group formed of palmitic acid chloride (C.sub.16), stearic acid chloride (Cis), arachidic acid chloride (C.sub.20) and behenic acid chloride (C.sub.22). At least one fatty acid chloride is behenic acid chloride (C.sub.22H.sub.43OC), the vaporization temperature of which at atmospheric pressure is of the order of 385 C. At least one fatty acid chloride is palmitic acid chloride (C.sub.16H.sub.31OC), the vaporization temperature of which at atmospheric pressure is of the order of 330 C. At least one fatty acid chloride is stearic acid chloride C.sub.18H.sub.35OC), the vaporization temperature of which at atmospheric pressure is of the order of 350 C. Nothing prevents the use of a fatty acid chloride which can be prepared by transchlorination of a fatty acid with a transchlorinating agent such as, for example, acetyl chloride. The fatty acid chlorides chosen for the implementation of a process according to the invention are liquid at room temperature. In a process according to the invention, the filiform elements 4 of the applicator device 3 are impregnated 5 with at least one liquid fatty acid chloride. This impregnation step 5 is carried out by bringing the filiform elements 4 into contact with said reactive composition 20 at room temperature, that is to say at a temperature reached without using means for regulating this temperature. However, there is nothing to prevent the filiform elements 4 from being, during this impregnation 5, at a temperature above room temperature but also inevitably below or at most equal to said acylation temperature. The temperature of the filiform elements 4 is suitable for enabling them to be loaded with said reactive composition 20 essentially in the liquid state. There is nothing to prevent said reactive composition 20 from being brought, during this impregnation step 5, to a temperature above room temperature, but adapted, depending on the fatty acid chloride(s) used, so that the fatty acid chloride(s) used are essentially in liquid form and capable of being impregnated in the liquid state on the filiform elements 4 of the applicator device 3. An applicator device 6 impregnated and loaded with said liquid reactive composition 20 is formed at the end of this impregnation step 5.

[0081] In a process according to the invention, a step 7 of heating said reactive composition 20 impregnated on the filiform elements 4 of the applicator device 3 is carried out and is adapted so that said reactive composition 20 reaches said acylation temperature. This heating 7 is carried out by any appropriate means. These means may be radiative heating means (for example by radiation in the infrared range), inductive heating means, or convective heating means. These means may also be heating means specific to the applicator device 3 and suitable for heating at least the filiform elements 4 and said reactive composition 20. At the end of this heating step 7, an applicator device 3 provided with filiform elements 8 loaded with said reactive composition 20 brought to said acylation temperature is formed.

[0082] In a process according to the invention, a step 9 of heating the solid material 1 is carried out so as to form a hot hydroxylated solid material 10in particular that is at said acylation temperature-, prior to a step 11 of applying the filiform elements 8 loaded with, and retaining, said reactive composition 20. The application step 11 is carried out by rolling the applicator device 3 over the hydroxylated solid material 1. Advantageously, the hot hydroxylated solid material 10 is at least partially dehydrated as a result of this heating 9. Moreover, the fact that the hot hydroxylated solid material 10 is at said acylation temperature makes it possible to help to maintain said reactive composition 20 at said acylation temperature, to promote chromatogenic acylation and to form the acylated solid material 12.

[0083] Surprisingly, the inventor has observed that heating 7 of said reactive composition 20 adsorbed by impregnation in the filiform elements 4 of the applicator device 3 allows application of fatty acid chloride on the hydroxylated solid material 1 and acylation of this hydroxylated solid material 1 with acid chloride in the gaseous state. According to the invention, the application of said reactive composition 20 heated to said acylation temperature of between 160 C. and 250 C. does not lead to a loss of fatty acid chloride in the gaseous state by dissipation into the atmosphere surrounding the filiform elements 4, 8. On the contrary, the filiform elements 4, 8 seem to behave like a reservoir of fatty acid chloridein particular in the gaseous statemaking it possible to release/form fatty acid chloride in the gaseous state in contact with the hydroxylated solid material 1 and to acylate it.

[0084] The invention goes against the teaching provided by the prior art, which describes distributing the fatty acid chloride(s) in a preferentially liquid state and necessarily at low temperature in contact with the cold or hot solid material, then heating the cold hydroxylated solid material to said acylation temperature or maintaining the hot hydroxylated solid material at said acylation temperature. According to this teaching, the fatty acid chloride(s) essentially in the liquid state deposited in contact with the hydroxylated solid material constitute(s) a reservoir of fatty acid chloride(s) essentially in the liquid state placed in contact with the hydroxylated solid material. According to this teaching, fatty acid chloride(s) in the gaseous state is (are) formed in the vicinity of the accessible hydroxyls of the hydroxylated solid material, due to heating the hydroxylated solid material to said acylation temperature.

[0085] According to this teaching, the formation of fatty acid chloride(s) in the gaseous state in the vicinity of the accessible hydroxyls of the hydroxylated solid material makes it possible to overcome the disadvantages of said boundary layer. That being said, the teaching provided by the prior art does not make it possible to solve the problem of the persistence on the hydroxylated solid material of amounts of fatty acid chloride(s) in the liquid state which have not been heated for a long enough time to be vaporized and to be able to react in the gaseous state with the hydroxylated solid material, in particular due to the movement of the web of hydroxylated solid material.

[0086] Of course, there is nothing to prevent, in a variant (not shown) of a chromatogenic acylation process according to the invention implemented on an industrial scale, the hydroxylated solid material from being in the form of a web of paper wound in a roll on itself, the paper being moved between an upstream reel and a downstream device for rewinding a web of acylated paper. In such a process implemented on an industrial scale, the paper has a run speed of between 30 and 100 meters per minute. An example of a device suitable for implementing such a process is shown in FIG. 4. In such a process, said reactive composition is applied at a fixed station to at least one main face of the moving paper web. In such a process, the applicator device comprises an applicator roller having an application surface provided with filiform elements and arranged over the entire width (or reel width) of the paper web. The roller has an axis of rotation parallel to the plane in which the paper web runs and not parallelin particular orthogonalto the run direction of this web. The roller is placed vertically at a distance from the paper web so that the filiform elements lightly contact the moving paper web without damaging it. Advantageously, the roller may be of the type having an axial lumen for receiving said reactive composition and for dispensing said reactive composition, assisted by centrifugal force, conveyed along the filiform elements until it is brought into contact with the paper web.

[0087] In certain advantageous embodiments, the roller is provided with means for heating said reactive composition to said acylation temperature. In these advantageous embodiments, the filiform elements forming the application surface of the roller act as an applicator reservoir for fatty acid chloride(s) in the gaseous state at said acylation temperature. In these advantageous embodiments, the volume in which the fatty acid chloride(s) are at the saturation vapor pressure at said acylation temperature is limited to the free volume provided by the filiform elements of the roller heated to said acylation temperature. According to these advantageous embodiments, it is not necessary to provide a thermostatically controlled chamber at said acylation temperature in which the partial pressure of the fatty acid chloride(s) is maintained at the saturation vapor pressure throughout its entire volume. That being said, nothing prevents the provision of at least one fairing wall of the applicator roller(s) and for confining the fatty acid chloride(s) in the gaseous state in contact with the paper web.

[0088] In certain advantageous embodiments of a chromatogenic acylation process according to the invention implemented on an industrial scale, when the roller has an axial lumen for receiving said reactive composition and for centrifugal dispensing of said reactive composition guided along the filiform elements until it comes into contact with the paper web, the roller, in particular the heating roller, is supplied with fatty acid chloride by a provision of said reactive composition in the axial lumen of the roller. In these embodiments, the impregnation of the filiform elements is at least partly carried out by the centrifugal stress produced due to the rotation of the roller, to which said reactive composition is subjected in the applicator roller.

[0089] In other embodiments, the applicator device may include, in addition to the roller, a device for dispensing fatty acid chloride onto the roller. It may be a cylinder, known as an anilox roller, for supplying the roller by kissing the surface of said anilox roller with the filiform elements. Any type of anilox roller can be used. It can be used by adapting the dimensions of its cells and their surface density to the amount of fatty acid chloride to be deposited on the applicator roller. The anilox roller may have an angular speed of rotation identical to or different from the speed of rotation of the applicator roll. Said anilox roller may be supplied with liquid fatty acid chloride via a doctor blade chamber itself supplied, in particular continuously, with fatty acid chloride.

[0090] The roller may be rotated with an angular speed of rotation chosen so that the free ends of the filiform elements are rotated with a linear speed having a value different from the value of the run speed of the paper web. The linear speed of the free ends of the filiform elements and the run speed of the paper web are not necessarily identical and can be adjusted to produce the desired light contact. That being said, the roller can be rotated in a direction of rotation chosen so that the free ends of the filiform elements of the pile are moved countercurrently or concurrently with respect to the movement of the paper web.

[0091] In a chromatogenic acylation process according to the invention implemented on an industrial scale, nothing prevents the roller and the dispensing device from being placed in a thermoregulated enclosure maintained at said acylation temperature.

[0092] In an advantageous variant, not shown, of a chromatogenic acylation process according to the invention implemented on an industrial scale, a flow of gaseous composition able to be loaded with hydrochloric acid in contact with the paper web being acylated is formed so as to move the hydrochloric acid formed as a result of this acylation away from the paper web.

[0093] An overview diagram of a variant of a process according to the invention for the chromatogenic acylation of a solid material 1, 2 bearing hydroxyl groups that are accessible to at least one fatty acid chloride in the gaseous state and that are capable of reacting with this (these) fatty acid chloride(s) is represented in FIG. 3. In this variant shown, a plurality of acylation phases 40, 50, 60 of a solid material 1, 2 are carried out, each of the phases 40, 50, 60 comprising a step 11, 24, 34 of applying a reactive composition 20, 21, 22 on the solid material 1, 2. The phases 40, 50, 60 of this plurality of phases can be carried out in an artisanal manner successively on the same piece of a solid material 1, in particular of a paper material. However, the phases 40, 50, 60 of this plurality of phases can be carried out during an industrial process for the chromatogenic acylation of a paper web 2 moved between an upstream reel of the paper web 2 and a downstream device 36 for rewinding the web 12, 25, 35 of acylated paper. During this implementation on an industrial scale, each reactive composition 20, 21, 22 is applied by means of an applicator device 3, 15, 28 for applying reactive composition(s) 20, 21, 22 respectively. The applicator devices 3, 15, 28 are arranged at a distance from one another along a run zone of the paper web 2, 12, 25, 35, extending in the thermoregulated chamber 39. Each reactive composition 20, 21, 22 may be formed of a single fatty acid chloride or may comprise a plurality of fatty acid chlorides. Advantageously, each reactive composition is free of any organic solvent. The reactive compositions 20, 21, 22 may comprise the same fatty acid chloride or chlorides of different fatty acids and of different fatty chain lengths.

[0094] The overview diagram represented in FIG. 3 also illustrates a process according to the invention implemented on an industrial scale, for the chromatogenic acylation of a web 2 of paper material 1 moved between an upstream reel and a downstream device for rewinding a web of acylated paper. In this industrial process, the paper web 2 is moved by any means known to those skilled in the art, so that the paper of the paper web 2 passes successively, owing to this movement, through a plurality of successive treatment zones. A first phase 40 of acylation of the paper of the paper web 2 is carried out in an upstream zone (with respect to the run direction from upstream to downstream of the paper web) of the plurality of successive treatment zones, then a second acylation phase 50 is carried out in an intermediate zone of this plurality of successive zones, then a third acylation phase 60 is carried out in a downstream zone of this plurality of successive zones. For example, nothing prevents the first acylation phase 40 from being carried out at an acylation temperature T1, the second acylation phase 50 from being carried out at an acylation temperature T2 and the third acylation phase 60 from being carried out at an acylation temperature T3, where T1<T2<T3.

[0095] During the first phase 40, the applicator device 3 has an application surface formed of filiform elements 4 that are not reactive with the fatty acid chlorides of said reactive composition 20. The applicator device 3 and the filiform elements 4 are suitable for being placed, without deterioration, at a temperature of between 160 C. and 250 C. and without loss of their application functions. In a process according to the invention carried out on an industrial scale, the applicator device 3 may be a roller arranged so that its axis of rotation on itself extends in a plane parallel to the plane of the moving paper web 2 and not parallelin particular orthogonalto the run direction of this paper web 2. The applicator device 3 is chosen and arranged so as not to damage the paper of the moving paper web 2. During the first phase 40, the filiform elements 4 of the applicator device 3 are impregnated 5 with at least one liquid fatty acid chloride. This impregnation step 5 is carried out at low temperature (i.e. at a temperature below the envisaged acylation temperature) by bringing the filiform elements 4 forming the application surface of the applicator device 3 into contact with said reactive composition 20 at room temperature, that is to say at a temperature reached without using means for regulating this temperature. However, there is nothing to prevent the filiform elements 4 from being brought, during this impregnation 5, to a temperature above room temperature but also inevitably below or at most equal to said acylation temperature. There is nothing to prevent said reactive composition 20 itself from being brought, during this impregnation step 5, to a temperature above room temperature, but adapted, depending on the fatty acid chloride(s) used, so that the fatty acid chloride(s) used are essentially in liquid form and able to be loaded in the liquid state on the filiform elements 4 of the applicator device 3. An applicator device 6 loaded with said liquid reactive composition 20 is obtained at the end of this impregnation step 5.

[0096] In a process according to the invention, a step 7 of heating said reactive composition 20 adsorbed on the filiform elements 4 of the applicator device 3 is carried out, this heating step 7 being adapted so that said reactive composition 20 reaches an acylation temperature T1. This heating 7 is carried out by any appropriate means. At the end of this heating step 7, an applicator device 3 provided with filiform elements 8 loaded with said reactive composition 20 at said acylation temperature T1 is formed.

[0097] In a process according to the invention, a step 9 of heating the paper of the moving paper web 2 is carried out so as to form a hot paper 10 at said acylation temperature T1, prior to a step 11 of applying the hot filiform elements 8 retaining said reactive composition 20, by rolling the applicator device 3 over the hot paper 10 of the paper web 2. Moreover, the fact that the hot paper 10 is at said acylation temperature T1 makes it possible to help to maintain said reactive composition 20 at said acylation temperature T1, to promote chromatogenic acylation and to form the acylated solid material 12.

[0098] During a second chromatogenic acylation phase 50, use is made of an applicator device 15 having an application surface formed of filiform elements 16 that are not reactive with the fatty acid chlorides of a second reactive composition 21. The applicator device 15 and the filiform elements 16 are suitable for being placed, without deterioration, at a temperature of between 160 C. and 250 C. and without loss of the application functions. In a process according to the invention carried out on an industrial scale, the applicator device 15 may be a roller with an axis of rotation extending in a plane parallel to the plane of the moving paper web 2 and not parallelin particular orthogonalto the run direction of the paper. The applicator device 15 is chosen and arranged so as not to damage the moving paper 1, 2, 14. During the second phase 50, the filiform elements 16 of the applicator device 15 are impregnated 17 with at least one liquid fatty acid chloride. This impregnation 17 is carried out at a temperature below the envisaged acylation temperature T2, by bringing the filiform elements 16 into contact with said reactive composition 21 at room temperature, that is to say at a temperature reached without using means for regulating this temperature. However, there is nothing to prevent the filiform elements 16 from being, during this impregnation 17, at a temperature above room temperature. That being said, the filiform elements 16 are at a temperature necessarily below or at most equal to said acylation temperature T2. There is nothing to prevent said reactive composition 21 from being brought, during this impregnation step 17, to a temperature above room temperature, but adapted, depending on the fatty acid chloride(s) used, so that the fatty acid chloride(s) used are essentially in liquid form and able to be loaded in the liquid state on the filiform elements 16. An applicator device 18 loaded with said liquid reactive composition 21 is formed at the end of this impregnation step 17. A step 19 of heating said reactive composition 21 adsorbed on the filiform elements 16 of the applicator device 15 is then carried out and is adapted so that said reactive composition 21 reaches the acylation temperature T2. This heating 19 is carried out by any appropriate means. At the end of this heating step 19, an applicator device 3, the filiform elements 23 of which loaded with said reactive composition 21 are brought to said acylation temperature T2, is formed.

[0099] A step 13 of heating the paper of the moving paper web 12 is carried out so as to form a hot paper 14 at said acylation temperature T2, prior to a step 24 of applying said reactive composition 21 on the hot paper 14, by rolling the applicator device 15 over the paper 14 and contacting the filiform elements 23 on the hot paper 14. Moreover, the fact that the paper 14 is at said acylation temperature T2 makes it possible to help to maintain said reactive composition 21 at said acylation temperature T2, to promote the chromatogenic acylation and to form an acylated paper 25 bearing acyl groups of the first and second reactive compositions 20, 21.

[0100] In the embodiment shown, use is made, during a third phase 60, of an applicator device 28 having an application surface formed of filiform elements 29 that are not reactive with the fatty acid chlorides of a reactive composition 22. The applicator device 28 and the filiform elements 29 are suitable for being placed, without deterioration, at a temperature T3 of between 160 C. and 250 C. and without loss of the application functions. In a process according to the invention carried out on an industrial scale, the applicator device 28 is preferably an applicator roller 28 with an axis of rotation on itself extending in a plane parallel to the plane of the paper of the moving paper web 25, 2 and not parallelin particular orthogonalto the run direction of the paper. The applicator device 28 is chosen and arranged so as not to damage the paper of the moving web 2, 25. During the second acylation phase 60, the filiform elements 29 are impregnated 30 with at least one liquid fatty acid chloride.

[0101] This impregnation 30 is carried out at a temperature below an envisaged acylation temperature T3, by bringing the filiform elements 29 of the applicator device 28 into contact with said reactive composition 22 at room temperature, that is to say at a temperature reached without using means for regulating this temperature. However, there is nothing to prevent the filiform elements 29 from being, during this impregnation 30, at a temperature above room temperature but also preferably below said acylation temperature T3. There is nothing to prevent said reactive composition 22 from being brought, during this impregnation step 30, to a temperature above room temperature, but adapted, depending on the fatty acid chloride(s) used, so that the fatty acid chloride(s) used are essentially in liquid form and able to be loaded by adsorption in the liquid state on the filiform elements 29 of the applicator device 28. An applicator device 31 loaded with said liquid reactive composition 22 is formed at the end of this impregnation step 30. A step 32 of heating said reactive composition 22 adsorbed on/impregnated in the filiform elements 29 of the applicator device 28 is then carried out and is adapted so that said reactive composition 22 reaches the acylation temperature T3. This heating 32 is carried out by any appropriate means. At the end of this heating step 32, filiform elements 33 loaded by impregnation with said reactive composition 22 brought to said acylation temperature T3 is formed.

[0102] A step 26 of heating the paper of the moving paper web 2, 25 is carried out so as to form a hot paper 27 at said acylation temperature T3, prior to a step 34 of applying the filiform elements 33 of the applicator device 28 retaining said reactive composition 22, by rolling the applicator device 28 over the paper 27. Moreover, the fact that the paper 27 is at said acylation temperature T3 makes it possible to help to maintain said reactive composition 22 at said acylation temperature T3, to promote the chromatogenic acylation and to form an acylated solid material 35 bearing acyl groups of the first, second and third reactive compositions 20, 21, 22. Provision may be made for other subsequent acylation phases.

[0103] In an embodiment that is not shown, there is nothing to prevent the implementation of a final phase of extracting fatty acid chloride that may be present in excess on the running paper web. To do this, a recovery device comprising an extractor roller, in particular a varnish roller having a recovery surface formed of a pile, can be applied to the paper web to take back off fatty acid chloride in the liquid state from the paper.

[0104] An example of an acylation device 100 capable of being used for implementing a process according to the invention is shown in FIG. 4. The acylation device 100 comprises an upstream reel 66 of a web 2 of paper to be acylated and a downstream device 36 for rewinding a web 35 of acylated paper. The acylation device 100 is provided with means 37 for guiding the web 2 of paper moving between the upstream reel 66 and the downstream roll 36. The guide means 37 comprise a plurality of rollers for guiding the moving paper web 2,10,12, 25, 35, which are positioned so as to guide the paper web 2,10,12, 25, 35 moving through a thermoregulated chamber 39 of the acylation device 100. The thermoregulated and, where appropriate, compartmentalized chamber 39 has a first upstream zone 41 (upstream in terms of the run direction 42 of the web 2 of paper 1) for entry of the paper 1 of the web into the first upstream zone 41 and into the thermoregulated chamber 39. This first upstream zone 41 is provided with at least one heated roller 38 and means for guiding the paper web 2, suitable for heating the paper web 2 to a temperature enabling the dehydration thereof, at least partially, while it is moving and prior to the acylation thereof. The thermoregulated chamber 39 has, extending downstream of the first upstream heating zone 41, a first acylation zone 43 suitable for being passed through by the moving paper web 2. The first acylation zone 43 may be provided with means (not shown) for heating and/or maintaining the atmosphere of this first acylation zone 43 at a chromatogenic acylation temperature T1. It also comprises a device 45 for dispensing a reactive composition 20 of at least one, in particular only onefatty acid chloride on the surface of the paper web 2. The dispensing device 45 comprises a support roller 44 and an applicator roller 3 having an application surface formed of filiform elements 4, in particular filiform elements 4 that form a pile. The applicator roller 3 is suitable for being rotated on itself so that the filiform elements 4 sweep, with light contact, the surface of the moving paper web 2,10. The support roller 44 and the filiform elements 4 of the applicator roller 3 cooperate to guide the paper web 2,10 into contact with the filiform elements 4 of the applicator roller 3.

[0105] The thermoregulated chamber 39 has, extending downstream of the first acylation zone 43, a second acylation zone 48 suitable for being passed through by the web 2 of moving paper 12 treated in the first acylation zone 43. The second acylation zone 48 may be provided with means (not shown) for heating and/or maintaining the atmosphere of this second acylation zone 48 at a chromatogenic acylation temperature T2. It also comprises a device 51 for dispensing a reactive composition 21 of at least one, in particular only onefatty acid chloride. The dispensing device 51 comprises a support roller 49, an applicator roller 15 having an application surface formed of filiform elements 16, in particular filiform elements 16 that form a pile, and that is suitable for being rotated so that the filiform elements 16 sweep, with light contact, the surface of the web 2 of moving paper 12. The support roller 49 and the applicator roller 15 cooperate to guide the web 2 of paper 12 by applying it in contact with the filiform elements 16 of the applicator roller 15.

[0106] The thermoregulated chamber 39 has, extending downstream of the second acylation zone 48, a third acylation zone 54 suitable for being passed through by the moving paper web 2 treated in the second acylation zone 48. The third acylation zone 54 may be provided with means (not shown) for heating and/or maintaining the atmosphere of this third acylation zone 54 at a chromatogenic acylation temperature T3. It also comprises a device 56 for dispensing a reactive composition 22 of at least one, in particular only onefatty acid chloride. The dispensing device 56 comprises a support roller 55 and an applicator roller 28 having an application surface formed of filiform elements 29, in particular filiform elements 29 that form a pile, and that is suitable for being rotated so that the filiform elements 29 sweep, with light contact, the surface of the web 2 of moving paper. The support roller 55 and the applicator roller 28 cooperate to guide the paper web 2 by applying one of the faces of the paper web 2 in contact with the applicator roller 28.

[0107] In certain advantageous embodiments, at least onenotably eachapplicator roller 3, 15, 28 is provided with means for heating said corresponding reactive composition 20, 21, 22 to the acylation temperature T1, T2, T3. In these embodiments, the first, second and third acylation zones 43, 48, 54 of the thermoregulated and/or compartmentalized chamber 39 are not necessarily each heated to said corresponding acylation temperature T1, T2, T3. In addition, at least one, in particular each, of the applicator rollers 3, 15, 28 advantageously has an axial lumen for centrifugally supplying, in particular continuously, the filiform elements 4, 16, 29 with reactive compositions 20, 21, 22.

[0108] There is also nothing to prevent at least onein particular eachof the support rollers 44, 49, 55 from being a heated roller suitable for helping to heat the paper web 2 to said acylation temperature.

[0109] In certain other embodiments, not shown, at least onein particular eachof the dispensing devices 45, 51, 56 may comprise a cylinder, known as an anilox roller, for supplying the applicator roller 3, 15, 28 with a reactive composition 20, 21, 22. Said anilox roller is arranged so as to be able to be lightly contacted tangentially by the corresponding applicator rollerer 3, 15, 28. In these embodiments, the temperature of said anilox roller and of the reactive composition 20,21,22 presented by said corresponding anilox roller are substantially the same temperature as the applicator roller 3, 15, 28. Said anilox roller may be supplied with liquid fatty acid chloride by means of a doctor blade chamber itself supplied, in particular continuously, with fatty acid chloride. In these embodiments, the doctor blade chamber forms a wall covering said anilox roller facing the peripheral surface thereof, with the exception of an open strip allowing contact of said anilox roller with the applicator roller 3, 15, 28.

[0110] The thermoregulated chamber 39 has, extending downstream of the third acylation zone 54, a zone 59 for extraction and back exchange of fatty acid chloride which may be present in excess on the moving paper web. The extraction zone 59 is provided with a support roller 61 arranged to be able to cooperate with an extractor roller 62 having a recovery surface formed of filiform elements 63 and to guide the running paper web 35. The recovery surface of the extractor roller 62 may be a pile provided with filiform elements 63 able to be loaded with excess fatty acid chloride(s) on the surface of the paper web 35. Advantageously, a flow 64 of gaseous compositionin particular a flow of atmospheric airheated to a temperature above said acylation temperaturein particular between said acylation temperature and the vaporization temperature of at least onein particular eachfatty acid chloride of said reactive composition, is applied in contact with the paper web 2 so as to entrain residual fatty acid chloride, vaporized under the effect of the flow 64 of gaseous composition. The flow 64 of gaseous composition loaded with fatty acid chloride is entrained successively through acylation zones 54, 48, 43, countercurrentfrom downstream to upstream- to the run direction of the paper web 2 and also enables an entrainment of the gaseous hydrochloric acid formed due to the acylation reaction in the thermoregulated chamber 39.

[0111] In certain embodiments, the extractor roller 62 is heated to a temperature, notably to a temperature between 250 C. and 400 C., which promotes the vaporization of fatty acid chloride(s). In other embodiments, the flow of gaseous composition heated to the vaporization temperature is applied over the filiform elements of the extractor roller.

[0112] In certain embodiments, the gaseous atmosphere of the thermoregulated and/or compartmentalized chamber 39 and/or the gaseous atmosphere extending into the lumen of at least one applicator roller 3, 15, 28 is depleted in gaseous oxygen. In these embodiments, a flow of at least one inert gas is introduced into the thermoregulated and/or compartmentalized chamber 39 and/or into the gaseous atmosphere extending into the lumen of at least one applicator roller 3, 15, 28.

EXAMPLE 1APPLICATION CONDITIONS

[0113] An applicator device is made using glass microfibers bonded together to form an applicator brush or pad. The glass microfibers are chosen to withstand temperatures of between 160 C. and 250 C. They are advantageously inert with respect to the fatty acid chlorides used. The applicator brush is loaded by briefly contacting the applicator brush with a piece of microfiber fabric with a size of 100 mm100 mm impregnated with 4 ml of undiluted liquid fatty acid chloride. It has been shown that this qualitative approach makes it possible to deposit on a solid material by contact of the brush on the solid material maintained for a fraction of seconds, the minimum amount of fatty acid chloride for conferring a hydrophobicity of the treated paper material which is acceptable after development of the acylation reaction.

[0114] The applicator brush thus loaded with fatty acid chloride is used to apply fatty acid chloride to a hydroxylated solid material. The applicator brush can be applied to the paper material with a contact time of the tip of the applicator brush and the hydroxylated solid material of the order of magnitude of 1/10.sup.th of a second and so that the tip of the microfiber brush deforms on contact, generating intimate physical contact between the microfibers of the brush and the surface of the paper material, promoting the transfer of fatty acid chloride.

[0115] That being said, it is possible to apply the fatty acid chloride by gliding the tip of the applicator brush over the surface of the paper material, like a paint. The application of fatty acid chloride by means of a brush made in this way makes it possible to mimic an application of fatty acid chloride on a moving paper such as can be carried out by means of a varnish roller provided with filiform elements, by favoring an instant application of reagent rather than a continuous application.

EXAMPLE 2APPLICATION CONDITIONSVARIABLE TEMPERATURE OF THE APPLICATOR BRUSHPAPER MATERIAL AT ROOM TEMPERATURE

[0116] Example 2 describes the application of a fatty acid chloride by means of an applicator brush that applies hot acid chloride to a paper material at room temperature. Palmitic acid chloride (C.sub.15H.sub.31COC) or stearic acid chloride (C.sub.17H.sub.35COC) is applied to a piece of blotting paper (Canson, 125 g/m.sup.2) using an applicator brush as described in example 1 and maintained, after loading with fatty acid chloride, at the acylation temperature in a thermostatically controlled oven. The applicator brush, after loading, is wrapped in aluminum foil to maintain its temperature and placed in the thermostatically controlled oven at the acylation temperature. Fatty acid chloride at the acylation temperature is applied by point contact, as described in example 1, of the hot applicator brush on the blotting paper at room temperature after removing the aluminum foil. At the end of this contact, the blotting paper is placed for a few minutes in an oven at a temperature of 180 C. to allow the development of the acylation reaction, then cooled to room temperature. The hydrophobicity of the treated blotting paper is evaluated by immersion in distilled water. The hydrophobic nature of the blotting paper obtained makes it possible to evaluate the effectiveness of the acylation. The hydrophobic character of blotting paper is evaluated by measuring the dimensions of the hydrophobic spot formed and also by the intensity thereof which reflects its resistance to wetting.

[0117] It is observed that the application of the reagent by the applicator brush maintained at room temperature produces a limited hydrophobic spot corresponding to the deposition zone of the fatty acid chloride. When the temperature of the applicator brush increases, the spots observed increase in size and in hydrophobicity intensity up to a temperature limit value beyond which the hydrophobicity decreases. This limit value is of the order of 200 C. for palmitic acid chloride (C.sub.16) and of the order of 220 C. for stearic acid chloride (C.sub.18).

[0118] These results indicate that the effectiveness of the acylation and the quality of the grafting obtained depend on the temperature of the applicator brush and the filiform elements thereof, and on the temperature of the reactive composition comprising the fatty acid chloride retained by the filiform elements. Unexpectedly, the heating of the fatty acid chloride retained by the applicator brush, which inevitably favors a shift of the liquid/vapor equilibrium of the fatty acid chloride toward the vapor state, does not actually lead to a loss of the fatty acid chloride in the gaseous state by diffusion into the atmosphere, but allows grafting of the fatty acid chloride in the gaseous state onto the paper material, substantially without allowing liquid fatty acid chloride to remain on the paper material.

[0119] The invention therefore goes against a preconception from the prior art according to which fatty acid chloride must necessarily be deposited in the essentially liquid state by printing on a moving paper web in order to allow the acylation of this paper web by heating the fatty acid chloride deposited on the paper web.

EXAMPLE 3APPLICATION CONDITIONSHOT APPLICATOR BRUSHPAPER MATERIAL AT VARIABLE TEMPERATURE

[0120] Fatty acid (palmitic acid C.sub.16 or stearic acid Cis) chloride is applied to a paper material heated to a temperature above room temperature, by means of a hot applicator brush impregnated with the corresponding acid chloride. The applicator brush impregnated with palmitic acid chloride (C.sub.16) is maintained at a temperature of 200 C. and the applicator brush impregnated with stearic acid chloride (C.sub.18) is maintained at a temperature of 220 C. as described in example 1. Fatty (palmitic or stearic) acid chloride is applied to a piece of blotting paper (Canson, 125 g/m.sup.2) placed in an oven at the acylation temperature. Immediately after the application of the fatty acid chloride, the piece of blotting paper which was the subject of this application is covered with a second piece of blotting paper as a developer piece of paper. The superposition of the two emitter/developer pieces is maintained in the oven for a few minutes at the acylation temperature. The hydrophobicity imparted to the developer piece is indicative of an excess of fatty acid chloride on the emitter piece of paper, that has not reacted with this emitter piece of paper at the acylation temperature.

[0121] The combination of a hot deposition of palmitic acid chloride (C.sub.16) by means of an applicator brush heated to a temperature of 200 C. on a piece of emitter blotting paper brought to a temperature of 140 C., 170 C. or 200 C. makes it possible to demonstrate that the acylation is promoted by blotting paper at a higher temperature, notably at a temperature close to (or equal to) the temperature of the applicator brush and of the fatty acid chloride associated with the brush. The developer piece superposed on the emitter piece itself brought to 140 C. has a high hydrophobicity. The hydrophobicity of the developer piece decreases when the emitter piece has been brought to a temperature of 170 C., to be almost undetectable when the emitter piece has been brought to a temperature of 200 C.

[0122] The combination of a hot deposition of stearic acid chloride (C.sub.18) by means of an applicator brush heated to a temperature of 220 C. on a piece of emitter blotting paper itself brought to a temperature of 160 C., 190 C. or 220 C. makes it possible to demonstrate that the acylation is promoted by blotting paper at a higher temperature, notably at a temperature equal to the temperature of the applicator brush and of the fatty acid chloride associated with the brush. The developer piece superposed on the emitter piece itself brought to 160 C. has a high hydrophobicity. The hydrophobicity of the developer piece decreases when the emitter piece has been brought to a temperature of 190 C., to be almost undetectable when the emitter piece has been brought to a temperature of 220 C.

[0123] The presence and amount of residual free acid chloride on the piece of emitter paper depends strongly on the temperature of the applicator brush and on the temperature of the fatty acid chloride associated with the brush and on the temperature of the piece of paper on which the fatty acid chloride is deposited.

[0124] The combination of a hot deposition of fatty acid chloride by means of an applicator brush heated to the acylation temperature of between 160 C. and 220 C. on a piece of paper material itself brought to the acylation temperature makes it possible to obtain an optimal acylation of the paper material for a reduced treatment timenotably almost complete in 1/10 of a secondand compatible with on-the-go treatment of a moving paper web. Such an optimal acylation can of course only be obtained by controlling and adjusting the amount of fatty acid chloride deposited on the paper material, as a deposit of an amount of fatty acid chloride greater than the stoichiometric amount of accessible hydroxyls on the paper material will allow a residue of fatty acid chloride to remain on the surface of the paper material.

EXAMPLE 4APPLICATION CONDITIONSHOT APPLICATOR BRUSHHOT PAPER MATERIALSUCCESSIVE DEPOSITIONS

[0125] A succession of hot depositions of a fatty acid chloride is carried out on the same zone of a piece of blotting paper, referred to as the emitter piece, each deposition of the succession of depositions being carried out as described in example 3 by means of a hot applicator brush loaded with fatty acid chloride. After each hot deposition of the succession of depositions, a piece of developer paper is superposed on the emitter piece, the superposition of the two emitter/developer pieces being maintained in an oven for a few minutes at the acylation temperature. The hydrophobicity imparted to the developer piece is indicative of an excess of fatty acid chloride on the emitter piece of paper, that has not reacted with this emitter piece of paper at the acylation temperature. The hydrophobicity of the emitter piece increases with the number of depositions. The hydrophobicity of the developer piece corresponding to the first two depositions remains low but increases with the third deposition. It emerges from this example that the acylation takes place during the first two depositions without significant release of fatty acid chloride from the emitter piece, only the third deposition being accompanied by a significant release of fatty acid chloride leading to acylation of the third developer sheet. For greater efficiency of the chromatographic acylation reaction, it is desirable to carry out acylation at a high temperature compatible with the thermal resistance of the paper material and to carry out several successive depositions of reduced amounts of fatty acid chloride. This is accentuated by the fact that the grafting of the fatty acid chloride on the paper material and the immobilization thereof has the effect of shifting, via the mass effect, the liquid/vapor equilibrium of the fatty acid chloride toward the formation of fatty acid chloride vapor and the grafting thereof on the paper material. The paper material and the surface hydroxyl groups behave like a specific pump of the fatty acid chloride in the vapor state which will tend to lower the concentration of the fatty acid chloride in the vapor state on the substrate and promote the diffusion of the reagent from the applicator brush to the paper material.

[0126] The effectiveness of the chromatogenic acylation reaction is defined by evaluating the hydrophobicity of the acylated solid material by measuring the contact angle formed between the main plane of the acylated solid material and a drop of pure water deposited on the surface of the acylated solid material. Typically, a contact angle value of an acylated solid material is between 90 and 150, the contact angle value of 1500 corresponding to a particularly hydrophobic and water-repellent material. The quality of acylation is also defined by measuring the period of time during which the contact angle value of between 900 and 1500 is maintained at room temperature and by the pocket of water test. The pocket of water test can only be carried out with a solid material in the form of a substantially square flexible sheet enabling the corners thereof to be gathered together to form a pocket of water. The impermeability of this pocket of water is analyzed by monitoring the loss of water (taking into account the evaporation).

[0127] The hydrophobicity can also be evaluated by observation of the water repellency. 1 ml of distilled water is deposited on the surface of the solid material and it is observed whether the drop of water formed rolls over the surface, by clinging or not clinging to the surface of the solid material. A satisfactory water repellency corresponds to a contact angle of approximately 150.

[0128] The invention may be the subject of numerous variants and applications other than those described above. In particular, it goes without saying that, unless stated otherwise, the various structural and functional features of each of the embodiments described above should not be considered to be combined with and/or intimately and/or inextricably linked to one another but, on the contrary, to be mere juxtapositions. Moreover, the structural and/or functional features of the various embodiments described above may be the subject, as a whole or in part, of any different juxtaposition or any different combination.