FR2978938A1 - Composition for imparting appearance and aspect of velvet, leather or skin material on base material e.g. cardboard, has microspheres dispersed inside liquid medium or pasty medium that is primarily made of resin in aqueous medium - Google Patents

Abstract

The composition has a set of expansible microspheres having different diameters, and an expansible material. The set of expansible microspheres is dispersed inside a liquid medium or a pasty medium that is primarily made of a resin in an aqueous medium. The set of microspheres is made of resin, and have minimal thermal expansion temperature of about 120/140 degrees Celsius and maximum expansion temperature of about 170/210 degrees Celsius. An independent claim is also included for a method for imparting appearance and aspect of velvet, leather or skin material on a base material e.g. cardboard, paper, and/or thermoforamable materials.

Description

FIELD OF THE INVENTION The present invention relates to the field of surface treatment, especially surfaces of thermoformable materials and / or paper / board. It relates more particularly to a composition and a process for obtaining a velvet, leather, skin or similar appearance on various materials, in particular on thermoformable materials and on paper and / or cardboard. The coated materials thus produced, whatever the applications for which they are intended, then have a particularly attractive appearance and singularly a touch. Their tactile and visual aspect can be suitably adapted, in a wide range of shades, by the action on parameters that will be explained later.

BACKGROUND ART There are multiple surface treatment techniques, of a physical and / or chemical nature, and for a variety of purposes. Some techniques rely on the use of microspheres, which contribute to impart a soft touch and / or a three-dimensional effect to the surfaces lined with such microspheres. Microspheres useful in these applications are expandable microspheres, consisting of a membrane encapsulating a blowing agent. The membrane of the microspheres is generally based on copolymers comprising at least one monomer chosen from monomers of the acrylonitrile, methyl methacrylate and vinyl chloride type, among others.

The blowing agent is preferably a gas, in general isopentane, isobutane or isooctane. The microspheres conventionally used have pre-expansion diameters of between 9-15 μm and 28-38 μm. Under the effect of the heat developed during the treatment for the expansion of the microspheres, they maintain their integrity and see their diameter multiplied by a factor of 4 to 5 approximately. Depending on the grades or references of the microspheres used, they have different expansion temperatures. Thus, the expansion temperatures of the microspheres can be between 80-95 ° C and 138-148 ° C at the start of the expansion applied to them, while the maximum temperatures recommended for complete expansion are generally between 120-135 ° C and 194-206 ° C. Typical applications of such expandable microspheres are essentially: injected PVC shoe soles, printing inks, explosives, paper and cardboard. In the field of printing inks, the microspheres incorporated in the inks have the role of providing a three-dimensional velvet effect to textiles or wallpapers, the surface of which, thus provided with various swelling microspheres, has a three-dimensional velvet effect to the touch. essentially because the microspheres, whose diameters are not perfectly constant from one microsphere to another or to all its neighbors in the coating, contribute to a three-dimensional effect generating such a touch effect. In the paper and cardboard sector, expanded microspheres are used for their contribution to reducing weight and / or increasing opacity, thickness and smoothness. It is this property of softness to surfaces coated with coatings comprising microspheres which has been utilized for the manufacture of anti-slip papers. Inflatable microspheres are also used in the plastics sectors, in particular in injection molding and in thermoforming, where they are included in the masterbatches. They then make it possible to obtain a finer material that is lighter than the same material without a microsphere. In the particular case of anti-slip papers, the anti-slip property is obtained by an expansion of microspheres such that they provide the surface which comprises them with a "soft", rubber-like character, which is precisely the objective aimed at ensuring that the treated surface has a greatly reduced sliding coefficient, and no further appearance considerations. The deposit of microspheres for this application is relatively small, in quantity and thickness. Moreover, the touch of the surfaces thus treated is identical regardless of the support treated.

SUMMARY OF THE INVENTION It has now been found that it is possible to obtain a visual and tactile appearance of the velvet, leather, skin or the like type on a base material chosen from paper / cardboard and / or thermoformable materials, with advantageously an effect called "writing effect", by depositing and fixing on said base material at least one resin composition containing microspheres having different diameters, advantageously chosen in different diameter ranges, of at least one expandable material and by treating the material thus provided with expandable microspheres, by drying accompanied by a treatment selected from a thermoforming treatment and / or a mechanical treatment, under conditions capable of breaking the integrity of at least a fraction of the expanded microspheres. Thus obtained and economically paper / cardboard and / or thermoformed parts having tactile and visual effects sought and adjustable to suit, including similar to those of velvet, leather and / or skin, and particularly advantageously s 'related to the tactile and visual effects of soft velvet materials, especially those of nubuck leathers. The invention thus has as its first object a composition of expandable microspheres as described below for the treatment of paper / cardboard surfaces, and / or thermoformable materials. The subject of the invention is also a process as defined above for the treatment of materials chosen from paper / paperboard and / or thermoformable materials with such an expandable microsphere composition, capable of conferring on them a velvet, leather, skin or the like. According to the invention, such materials are provided with a velvet, leather, skin or similar appearance with a minimum energy input, with great flexibility as to the characteristics of the results obtained, and with great adaptability of the results by a simple selection. suitable for the composition of expandable microspheres and the operating parameters to be used. The invention further relates to the products coated by said process and / or by means of such an expandable microsphere composition.

DETAILED DESCRIPTION OF THE INVENTION In accordance with the present invention, an expandable microsphere composition is developed and implemented wherein said microspheres have at least two, and preferably more than two, different diameters and are at least partially able to be split off. and / or disorganized after deposition / fixation and drying on at least one surface of a material selected from paper / cardboard and thermoformable materials, and treating said deposited microspheres, such that the arrangement of the microspheres at the vicinity of said surface is disorganized and / or comprises microspheres having their free surface exploded after thermal expansion and / or brushing said free surface of said microspheres. Although it is not desired to be bound by any theory, it is believed, in the light of the numerous tests and comparative tests that the Applicant has carried out, that in the compositions and method according to the invention, the expandable microspheres included and solicited by the action of the applied thermal and / or mechanical energy, reorganize and / or burst selectively, so as to provide a surface of the material having a statistical distribution of microspheres of significantly different sizes at least two to two and / or being thus endowed, in this statistical distribution, a certain proportion respectively of whole microspheres and microspheres exploded under the thermal and / or mechanical effect of the treatment. The invention thus provides surface elements which, from a tactile as well as a visual point of view, contribute to a velvet, leather, skin or similar effect overall, instead of a gummy effect such as that which the prior art to obtain, and which met a specific objective sought, namely anti-slip power. In the present state of the types of support materials used, microsphere compositions available and applicable treatment techniques, the bursting and reorganization of the microspheres must be considered random, and therefore not completely controllable. The microspheres used according to the present invention advantageously have thermal expansion starting temperatures of the order of 120/140 ° C., and maximum expansion temperatures of the order of 170/210 ° C. They can be chosen from n types of microspheres, while n is an integer whose value is advantageously from 1 to 3. For each of these n types of microspheres, it is advisable to choose, with advantage, diameters of different microspheres. , advantageously in p ranges of different diameters, while p is an integer whose value is advantageously from 1 to 3. The expandable microspheres used are in practice chosen from a range of microspheres whose diameter before expansion is between about 6 and 45 μm, more preferably between about 9 and 38 μm. The microspheres thus selected may be from the same commercial reference or a mixture of several references. In order to facilitate the selection of the microspheres providing the desired tactile and visual effects, it is recommended to carry out case-by-case preliminary tests, and the expandable microspheres can in any event be selected from the following commercial products: EXPANCEL®, marketed by the Swedish producer EKA Chemicals AB of the AKZO NOBEL group, MICROPEARL / MICROSPHERE F® from the Japanese producer MATSUMOTO 25, and DAIFOAM from the Japanese producer DAINICHISEIKA. In this context, it is possible to prepare and use a mixture in adjusted proportions, for example, of a type of microsphere or ball that expands little and provides a rubbery feel with intermediate balls giving a little more volume and softness. and also optional with even more expansive beads providing volume and suede appearance. The coating of the microsphere composition according to the invention which is intended to be applied to the support to be treated is in the form of a liquid or a paste.

It is inside this liquid or this paste that the microspheres used according to the invention are dispersed. This liquid or paste is conventionally formulated from a synthetic resin in an aqueous medium. Said resin is advantageously chosen from acrylic emulsions, acrylic copolymer dispersions, ethylene / vinyl acetate copolymer dispersions, acrylate / vinyl acetate dispersions, vinyl acetate / versatate copolymer dispersions. vinyl, and polyesters-polyurethanes. Those skilled in the art know such formulations and are able to develop them with his usual knowledge and / or to obtain them from the respective manufacturers who market such resin formulations. In practice, such a resin is selected to provide the best possible adhesion to the support to be coated, which is obtained and confirmed by an iterative method based on tests within the reach of those skilled in the art. The selection of the deposition resin also takes into account the objective of optimizing the tactile and visual properties of the coating applied to the support, as it is revealed after drying. The choice of resins used and possibly added touch agents makes it possible to influence the final result and to control it. Resins are indeed a determining factor in obtaining the product, because if the resin is too hard with a dry extract too high, it will dry too quickly and the expansion can not be done properly, and conversely if it is too soft with a dry extract too weak, the expansion will be long before the resin hardens, and it will form a surface snow appearance. Drying and expansion must occur at a minimum distance, while it should be remembered that for polystyrene the final result can be obtained directly by thermoforming without brushing.

According to the invention, the expandable microspheres as described above are incorporated in the aforesaid resin, or an equivalent thereof, preferably in a proportion such that the solids content is between about 30 and 60% by weight. and advantageously between about 40 and 50% by weight.

Preferably, the level of expandable microspheres so incorporated is between about 1 and 15% by weight, more preferably between about 2 and 10% by weight, and most preferably between 5 and 10% by weight of the dispersion resin, by relative to the wet weight thereof. Below 2%, the volume effect would not be obtained, and a proportion greater than 10% would give too high concentration of beads that can generate surface defects and also an irregular expansion. In addition to the aforementioned constituents, it is possible to add to the formulation, to facilitate and / or secure the implementation of the treatment method according to the invention, adjuvants and / or additives commonly used in textile coatings or treatment leathers. These optional additional components are typically touch modifiers, such as animal, vegetable or synthetic waxes, packing agents, thickeners, and / or other surfactants. Advantageously, said liquid or said paste is formulated in such a way as to give it a color, which is a function of the coloration targeted for the treated material surface. The dyes or mixtures of suitable dyes / pigments are advantageously incorporated, depending on the desired color tone and intensity, at the rate of at most about 8% by weight of the formulation, on the basis of the wet weight thereof. this. After expansion under the conditions described below, the diameter of the microspheres thus formulated and applied according to the invention was found to be between about 20 and about 150 μm. The composition and the process are particularly suitable for use in the treatment of paper / cardboard surfaces, and / or thermoformable materials such as, but not limited to, polystyrenes, polypropylenes, rigid PVC, amorphous poly (ethylene terephthalate) (APET), poly (ethylene glycol terephthalate) (PETG) and acrylonitrile-butadiene-styrene (ABS). In the process according to the invention, and in order that the application of the microsphere formulation to be applied can provide the most advantageous results, it is recommended to deposit on a suitable support a quantity of the above-mentioned liquid or paste between about 20 and 100 g / m 2, preferably between about 40 and 80 g / m 2, and more preferably between about 50 and 75 g / m 2 in wet form. To achieve a coating of such a liquid or such a paste including microspheres according to the invention on a suitable support, it is possible to implement a conventional coating technique, preferably selected from curtain coating, roller coating (and in particular so-called "reverse-roll coating" or rolling coating in the opposite direction, the thousand-point roll coating, among others), the rotating-frame coating, the coating by spraying, Meyer bar coating, Zimmer process bar coating, and others. Particularly preferred is the application method employing a rotating frame. Once the coating has been carried out, the coated support is advantageously conveyed into an installation, such as an appropriate drying tunnel, the parameters of which, in particular the temperature and the degree of drying, depend on the material concerned. Said drying is preferably carried out by infrared radiation and / or by convection. In the case of paper / board media, the temperature is preferably chosen to achieve a substantially total expansion of the microspheres. In the case of thermoplastic supports, the temperature is chosen and adjusted so that the expansion of the microspheres is not achieved; this is then obtained by the implementation of the thermoforming operation during which we take advantage of the rise in temperature it requires and 25 which, however, maintains the material to be treated all its integrity. An example of a thermoforming operation with expansion of microspheres in accordance with the invention is described below, with reference to the case of polystyrene. However, the material of the plastic support to be coated according to the invention may equally well be selected from among polystyrenes, in particular a standard impact polystyrene or a superchoc polystyrene, both intended for thermoforming, or among others. thermoformable plastics such as those indicated above. In practice, said thermoformable plastic support preferably has a thickness in the range of 300 to 2300 μm, more preferably an average thickness of about 500 to 1500 μm.

After drying and cooling by conventional means, the coated support may be stored as stacked plates or coiled in coils. The material, in particular polystyrene, thus coated is intended for thermoforming and provides coated thermoformed parts. It is during this transformation by thermoforming that the coating of the support material takes its structure giving it the appearance of velvet, leather, skin or the like sought. Any conventional thermoforming process can be used.

This technique consists in forming with a mold a thermoplastic sheet softened by heating, which is then pressed onto a mold or a shape which is made to marry the contours. The molds used may be negative or positive type, and the use of a counter-mold is also possible.

According to the present invention, the heat necessary for the softening of the thermoplastic sheet is used to obtain the expansion of the expandable microspheres contained in the coating of the support material previously coated accordingly. The expansion of the microbeads obtained during the thermoforming operation gives the thermoformed piece a velvet, leather, skin or similar appearance. This visual and tactile aspect can be modulated or adjusted by varying the type of microspheres used. In another aspect, the method according to the invention involves as a support a paper / cardboard. In this case, the desired effect is obtained by means providing a suitable mechanical / thermal treatment on the coated surface of the paper / cardboard concerned. In particular, all the desired tactile and visual effects are obtained by subjecting the coated surfaces to brushing, advantageously by means of a system of brushes preferably comprising animal fibers, such as for example horsehair, and synthetic fibers. . Said fibers in the brush system can be used alone or in a mixture. By way of non-limiting example, a paper / cardboard brushing machine coated with expandable microspheres according to the invention may comprise the following brushes: Brush 1: horse hair + synthetic fiber, with a fiber length of 30 / 35 mm); Brush 2: horsehair + synthetic fiber, with a fiber length of 30/35 mm); Brush 3: horsehair (fiber length 17/20 mm).

After possibly conventional tests, simple routine, the skilled person is able to assert the choice of brushes. The retained brushes should preferably have different hardnesses, to allow a hard brushing operation and then polishing. What is essential is that we break the excessive regularity of the microspheres resulting from the expansion. Proper brushing provides, for example, a loss of thickness after brushing about 100-150 μm. In practice, the speed of rotation of the brushes should be adjusted to about 900 rpm, but advantageously with variation possibilities, while the direction of rotation of the brushes is preferably opposite to the direction of movement, although a rotation in the same direction as the direction of travel of the coated material is also possible. One can use a conventional brushing device, where each brush is supported on a counter-cylinder, while the spacing between the operating brush and the counter-cylinder is adjustable to allow in this way also to change the intensity of the brush. brushing. An alternative is to use at least one brush abrasive type, both circular and rotary. When a rotary abrasive brush is used, it is recommended to optionally add an operation of slicing or lateral movement intended to avoid / reabsorb the traces of brushing. By proceeding as indicated above, but varying the process and / or composition parameters, various articles having different leather, velvet, skins and the like have been obtained. It has thus been found that, even if the feel of a paper / cardboard coated according to the invention is still similar to non-slip paper before brushing, the action of brushing after expansion and drying of the paste coating Expandable microspheres or microbeads according to the present invention modify the round structure of the microspheres and impart to them random shapes, thus modifying both the visual effect and the tactile effect of the coated paper / cardboard surface. The advantages of the composition and method according to the present invention, noted during the tests which have been carried out, are therefore mainly the following: By controlling, by iterative tests, the adjustable parameters of the process employed and the compositions used the person skilled in the art can then vary and adjust suitably, or to meet particular demands, the physico-chemical parameters of the coatings 10 made in accordance with the present invention. In the process according to the invention, one takes advantage of the heat necessary for thermoforming and / or the mechanical and / or thermal energy that is used respectively in conventional thermoforming and / or in the brushing recommended as an alternative according to the invention to complete the fixation of the microspheres, and also to obtain, at lower cost and with high reliability of the results, parts of thermoformable material and / or paper / cardboard having a surface whose touch is at least partially visually and / or tactilely related to that of velvet, leather, skin or similar aspects. The invention also relates to the pieces of coated material resulting from the implementation of the method according to the invention on the base material, and / or whose coating uses at least one composition for coating microspheres according to the invention. the invention. It has been found that the finished materials or parts are thus obtained whose surfaces thus treated have a visual and tactile appearance of velvet, leather or skin type, or the like, in particularly practical and economical conditions. Once the microspheres or microbeads coated on a paper / cardboard support have been "broken" in accordance with the present invention, the surface thus treated has a finger-writing effect, which is the effect that is obtained. when you put your finger on the surface concerned. We get a trace, as with deer and if we pass the foigt in the other direction we have another effect. This effect is similar to that obtained on a polyester microfiber cloth scraped or on velvet leather or nubuck. It is even possible to obtain an imitation of skins on the flower side.

By comparing high magnification photographs and touch tests, it has been found that: - when the microspheres are left in the spherical state, the surfaces have a regular appearance and have a rubber-like feel, that is, blocking, as with the prior art slip paper, and - when the microspheres are scrubbed in accordance with the present invention, the appearance of the surface thus treated becomes uneven. This one is more slippery, with effect of writing. In the case of thermoformed parts, the distribution of the coating having the desired effect on the surfaces to be treated appeared particularly complete and homogeneous, advantageously on all the surfaces concerned, even when they constitute reentrant surfaces of the part resulting from a thermoforming operation, which constitutes an important additional advantage attributable to the technique according to the present invention. If it is put in place reserves or uncoated areas according to the invention, it is possible to obtain thermoformed parts of which only surface portions coated with a composition according to the invention are treated in accordance with the present invention.

Furthermore, it is known that the thermoformed parts are recyclable: after being ground again for other applications, after injection or thermoforming for uses in which a coarser material may be suitable. However, with the thermoformed products coated according to the present invention, they can even be directly re-extruded for the same purposes, that is to say, for example to subject the falls resulting from the implementation of the initial thermoforming process to grinding. and then reintroducing this material into the traditional extrusion process of a sheet of thermoforming material, for example polystyrene.

Claims (17)

REVENDICATIONS1. Composition intended to impart a visual and tactile appearance of velvet, leather, skin or the like type to a base material selected from paper / cardboard and / or thermoformable materials, with an optional so-called "writing effect" effect, characterized in that it comprises expanding microspheres having different diameters, advantageously chosen in different diameter ranges, of at least one expandable material, while said microspheres are dispersed inside a liquid or pasty medium even essentially consisting of a resin in an aqueous medium. 2. Composition according to claim 1, characterized in that said microspheres have thermal expansion starting temperatures of the order of 120/140 ° C, and maximum expansion temperatures of the order of 170/210 °. vs. 3. Composition according to claim 1, characterized in that said microspheres are chosen from n types of microspheres, while n is an integer whose value is advantageously from 1 to 3, and have diameters of microspheres in p diameter ranges. different, while p is an integer whose value is advantageously from 1 to 3. 4. The composition according to claim 1, characterized in that the expandable microspheres are selected from a range of microspheres whose diameter before expansion is between about 6 and 45 μm, more preferably between about 9 and 38 μm. 5. Composition according to claim 1, characterized in that said resin is chosen from acrylic emulsions, acrylic copolymer dispersions, ethylene / vinyl acetate copolymer dispersions, acrylate / vinyl acetate dispersions, copolymer dispersions of vinyl acetate / vinyl versatate, and polyesters-polyurethanes. 6. Composition according to claim 1, characterized in that said expandable microspheres are incorporated in said resin, or an equivalent thereof, in a proportion such that the solids content is between approximately 30 and 60% by weight, and advantageously between about 40 and 50% by weight. Composition according to claim 1, characterized in that the level of incorporated expandable microspheres is between about 1 and 15% by weight, more preferably between about 2 and 10% by weight, and most preferably between 5 and 10% by weight. weight of the dispersion resin, based on the wet weight thereof. 8. Composition according to claim 1, characterized in that it also comprises, optionally, touch modifiers, such as waxes of animal, vegetable or synthetic origin, fillers, thickeners, and / or other surfactants. 9. A method for providing a velvet, leather, skin or similar appearance to a base material, said base material being selected from paper / paperboard and thermoformable materials, characterized in that it comprises the deposit with fixing / drying on said expandable microsphere material dispersed within a liquid or pasty medium itself essentially consisting of a resin in an aqueous medium according to any one of claims 1 to 8, and treating said microspheres deposited on said material, such that the arrangement of the microspheres in the vicinity of said surface is disorganized and / or comprises microspheres having their free surface exploded after thermal expansion and / or brushing said free surface of said microspheres. 10. Process according to claim 9, characterized in that the material thus provided with expandable microspheres is treated by drying accompanied by a treatment chosen from a thermoforming treatment and / or a mechanical treatment, under conditions capable of breaking the lump. integrity of at least a fraction of the expanded microspheres. 11. The method of claim 9, characterized in that the diameter of the microspheres present in said composition is between about 20 and about 150 μm after expansion. 12. Method according to claim 9, characterized in that it is used for the treatment of the surfaces of paper / paperboard, and / or thermoformable materials such as polystyrenes, polypropylenes, rigid PVC, poly (terephthalate). amorphous ethylene) (APET), poly (ethylene glycol terephthalate) (PETG) and acrylonitrile-butadiene-styrene (ABS). 13. Process according to claim 9, characterized in that it comprises the deposition on a suitable support of an amount of said liquid or said paste of between approximately 20 and 100 g / m 2, preferably between approximately 40 and 80 g / m 2. m2, and more preferably between about 50 and 75 g / m2 in wet form. 14. The method of claim 9, characterized in that it comprises an application method using a rotary frame. 15. The method of claim 9, characterized in that it is implemented on paper / cardboard, and the temperature is preferably chosen so that one reaches a substantially total expansion of the microspheres. 16. The method of claim 9, characterized in that it is implemented on supports of thermoformable materials, especially polystyrene, the temperature being selected and adjusted so that it does not reach the expansion of the microspheres; this being then obtained by the implementation of the thermoforming operation. 17. Coated products made of base material chosen from paper / paperboard and / or thermoformed parts, in particular of polystyrene, characterized in that they are obtained from a composition according to any one of Claims 1 to 8 or by a process according to any one of claims 9 to 16.