FR2969637A1 - Crosslinking adhesive composition, without solvent, on film, by driving and/or guiding film in air conditioned enclosure by Carroll drive and/or guide, where composition comprises polyurethane or polyether and compatible tackifying resin - Google Patents

Abstract

Process of crosslinking an adhesive composition, without solvent, on a film, comprises driving and/or guiding a film in an air conditioned enclosure by Carroll drive and/or guide. An independent claim is included for air conditioned enclosure comprising a Caroll drive or guide.

Description

FIELD OF THE INVENTION The subject of the invention is a novel method for crosslinking a heat-curable adhesive composition by heating and the associated device.

BACKGROUND OF THE INVENTION Pressure-sensitive adhesives (also called self-adhesive adhesives or "Pressure Sensitive Adhesives" or PSA) are substances which give the support which is coated with them an immediate adhesive strength at ambient temperature (often termed "tack"), which allows its instant adhesion to a substrate under the effect of a light and brief pressure. PSAs are widely used for the manufacture of self-adhesive labels which are affixed to articles for the purposes of presenting information (such as bar code, name, price) and / or for decorative or medical purposes. PSAs are also used for the manufacture of self-adhesive tapes of various uses. For example, in addition to the transparent adhesive tape widely used in everyday life, there is the shaping and assembly of cardboard packaging; surface protection for painting work, in construction; the maintenance of electrical cables in the transport industry; carpet bonding by double-sided adhesive tape. For the manufacture of self-adhesive labels and / or tapes, PSAs are often applied by continuous coating processes over the entire surface of a large (possibly printable) backing layer, at a rate (usually expressed in g / m2) and hereinafter referred to as "grammage". The support layer is made of paper or film of a single or multi-layered polymeric material. The adhesive layer which covers the support layer may itself be covered with a protective release layer (often called the "release liner"), for example consisting of a silicone film. The multilayer system obtained is generally packaged in the form of large coils up to 2 m wide and 1 m in diameter, which can be stored and transported. These films on the coils can be further processed into self-adhesive tapes by cutting and packaging into rolls of defined width and length. Self-adhesive tapes and labels are generally manufactured with reactive or non-reactive adhesives in the solvent phase. These solvents are intended to facilitate mixing, dosing, pumping, etc. during the production of these adhesives and their implementation, but especially to facilitate their coating in a thin layer, thin layer which after evaporation will create the self-adhesive surface. The low solids content of these adhesives ensure an application rheology (viscosity) suitable for sizing by roll (x) and drying. However, the use of solvents is subject to increasingly stringent regulations, and solvents are destined to disappear. More recently some lines are exploited with adhesives in aqueous phase. In this case, if the problems inherent in the solvents are removed, the problem of the drying of the coating remains whole (The drying must be progressive for reasons of appearance, the water has a high evaporation enthalpy compared to those of common solvents, and also requires heating and strong ventilation and extraction.The drying must also be complete).

In most cases, drying ovens suitable for the production of self-adhesive ribbons and labels (especially high performance) have a useful length of 10 to 100 meters, are heated by forced air (80 ° C to 180 ° C) and are equipped with powerful extraction to complete drying, and in the case of solvent-phase adhesives, to keep vapors emitted below their explosive threshold. These processes are very energy intensive, noisy and heavy in terms of maintenance. It has also been recently developed solvent-free technologies, reactive, with 1000/0 dry extract, including HMPSA (Hot Melt PSA) and UV PSA cure (PSA generally acylic, crosslinkable to UV), and more recently STPU- PSA Hot-Cure, it is for example a composition that is curable hot (and in the presence of moisture). Such a technology makes use, to obtain good properties, of a moisture content adapted to the quantity of adhesive (generally stoichiometry), and a relatively high temperature (from 50 ° C. to 180 ° C., preferably between 80 ° C and 160 ° C and most often between 100 and 140 ° C) to obtain the desired conversion rate in a defined time, compatible with the size of the furnaces and the line speeds. R: \ 32100 \ 32101 BSTK \ 32101--101228-DEPOT EN.doc Reactive technology based on thermal crosslinking, if it may require a controlled humidity and a high temperature for the reaction to be rapid, does not contain any solvent and requires only a very small extraction (mainly useful for the proper functioning of the control system in the oven or enclosure). The fact that there is no need to dry the coating as in the case of solvent or aqueous technologies, allows the use of more compact furnaces, know on a design type ovens or ovens and no longer as dryers . But the very sticky nature of the coatings prohibits all contact with surfaces, even anti-adhesive treated (Fluorocarbon treatment (Teflon ()) or plasma for example). The systems can be horizontal or vertical, but in all cases must be linear. In Figure 1, there is shown a system according to the state of the art based on suction in vacuum boxes, allowing a reversal of the band, the glued face being inwardly of the loop. Such a system is obviously complex, difficult to control, with high costs. There is therefore a need for a thermal crosslinking process which is compact, while avoiding contact of the tacky material with the various elements of the device, and which is of a simple and robust design. SUMMARY OF THE INVENTION The subject of the invention is a process for crosslinking a solvent-free crosslinkable adhesive composition on a film comprising driving and / or guiding said film in an air-conditioned chamber, by a Caroll drive or guide. Particular embodiments are as follows: the adhesive composition is an HMPSA adhesive composition. the adhesive composition is an adhesive composition comprising: 20 to 85% of a polyurethane or polyether comprising 2 hydrolysable alkoxysilane end groups; 15 to 80% of a compatible tackifying resin; and 0.01 to 3% of a crosslinking catalyst. the temperature in the climatic chamber is between 50 ° C. and 200 ° C., preferably between 80 ° C. and 160 ° C. and advantageously between 100 ° C. and 150 ° C. and / or humidity. The relative amount is from 30 to 90% RH, preferably about 50% RH. the film forms parallel or zig-zag corrugations by passing over multiple interferences. - The climatic chamber comprises in the lower part a series of rollers or rollers Caroll and in the upper part a series of full cylinders or another series of rollers or rollers Caroll. - The rollers or rollers are movably mounted on the support axis. - The rollers or rollers are motorized or free. - The cutting of the drive or Caroll guide in the film is implemented with a rotary cutting system with magnetic cylinder and removable plates. the rollers or rollers are associated with counter rollers or against rollers. the process comprises a step of double coating on both sides of the film. - The method further comprises a delaizage cutting step. - the inlet and outlet of the enclosure are located on the same side, on opposite sides or on adjacent sides. the film is preheated to a temperature close to the temperature of the chamber before crosslinking. - the film is perforated. The invention also relates to an air-conditioned enclosure comprising a Caroll drive or guide. Particular embodiments are as follows: the temperature in the climatic chamber is between 50 ° C. and 200 ° C., preferably between 80 ° C. and 160 ° C. and advantageously between 100 ° and 150 ° C. and / or relative humidity is between 30 and 90% RH, preferably about 50% RH. - The climatic chamber comprises in the lower part a series of rollers or rollers Caroll and in the upper part a series of full cylinders or another series of rollers or rollers Caroll. R: \ 32100 \ 32101 BSTK \ 32101--101228-DEPOT EN.doc 35 - the rollers or rollers are mounted mobile on the support axis. - The rollers or rollers are motorized or free. - the enclosure includes a multiplicity of embarrassments. - The enclosure is associated with a cutting device of the Caroll drive or guide comprising a rotary cutting system with magnetic cylinder and removable plates. the rollers or rollers are associated with counter rollers or against rollers. - The enclosure is associated with a delaizage cutting device. The invention is based on the use of a Carroll drive (and / or guidance), which is based on the use of the edges of the film, generally with the presence of holes for driving or mechanical guidance, or perforated tape. The invention makes it possible to obtain, with a non-crosslinkable solvent-free adhesive, one or more of the following advantages: compactness, since the glued face can travel with the coating facing the axis, hence a gain in footprint ; 20 - significant gain in terms of investment, but especially of operation (energy saving, reduced maintenance); - regulation of the enclosure (or oven) in temperature and humidity easier; 25 - possibility of double-sided coating. BRIEF DESCRIPTION OF THE FIGURES The invention is described with reference to the following figures: FIG. 1 represents a diagram of an oven available on the market. Figure 2 shows a view of a Caroll type drive. - Figure 3 shows a sectional view of an air-conditioned chamber with Caroll drive. Figure 4 shows a roll and counter roll of a Caroll drive. R: \ 32100 \ 32101 BSTK \ 32101--101228-DEPOT EN.doc DESCRIPTION OF EMBODIMENTS OF THE INVENTION The invention is now described in more detail (in the following, the training description is also intended to guide unless specifically stated otherwise).

In Figure 2, there is shown a view of a Caroll type drive (1). This type of training owes its name to its inventor, and is used in many industries, including mechanography and "punching", or lateral perforation of media (paper, cardboard, etc ...) for their transport (Conveying, gear), detection (mechanical probes or optical detection), automation, etc. The cutout (2) is shown here as being lateral, but can be median, or multiple for the films of large width or large widths. The support film receiving the adhesive layer according to the invention is therefore perforated with a Caroll cut. Such cutting can be performed at high speed (> 100 m / min) on most substrates: nonstick treated paper (Silicone or Kaolin treated), paper labels, thermoplastic films (Polyolefins, Polyester, Polyamide, etc ...). Cutting can be practiced either by traditional, linear or rotary systems (punch and die type) or by rotary cutting systems with magnetic cylinder and removable plates (consumable plates placed on the magnetic cylinders, magnetism holding the plates on the cylinder ). Rotary cutting with magnetic cylinder and removable plates, allows a quick change of tools, an evolution of the design of perforations, and can be associated with a system of ejection of waste (compressed air, aspiration). In general, the cleanliness of the perforated film and the working environment is obtained (the confetti produced by punching, which are very light, have a tendency, without any effective suction to be fixed on the surfaces by electrostatic effect). Rotary cutting with magnetic cylinder and removable plates is adapted to frequent width changes. Such cutting allows to quickly set the path, by centering or servo to an edge (wedging on a roll edge). By this cut, a film is obtained for receiving an adhesive deposit without crosslinkable solvent. This support film is driven or guided in the enclosure by Caroll drives. In Figure 3, one can see by way of example a climatic chamber (3) with drive Caroll, whose compactness is obvious. For a useful oven length of 25 meters, the floor length is less than 2 R: \ 32100 \ 32101 BSTK \ 32101--101228-DEPOT EN.doc meters, or even less than 1.5 meters (for a height of the order from 2 to 3 meters). The residence time in the climatic chamber corresponds to that of a dryer of 25 meters offering only one pass according to the state of the art. This compactness offers improved thermal and hygrometric regulation, compared to a traditional linear dryer. In the chamber shown, the film forms parallel loops (parallel ripple). The spacing of the rollers / rollers would lead to the formation of a zig-zag (zig-zag corrugation). The presence of a Caroll drive thus makes it possible to have the glued face turned towards the axis of the drive, but without the glued face, which is tacky at least during part of the process, does not touch fixed parts or oven movement. Training (and / or guidance) Caroll can be of different natures. In general, they are rollers or rollers (4) provided with pins (5) fitting into the holes of the strip (6). Various shapes can be provided for the holes (circular, square or any other shape), and it is also possible that the only friction on a suitable support is sufficient for the training or at intermediate levels. The rollers or rollers can be free, the film simply moving by a traction system external to the climatic chamber. The rollers or rollers may be motorized, in whole or in part only, in the upper part and / or low and / or median. The rollers also serve to guide the film and / or to avoid vibrations during film transfer. The motorization of the rollers can be synchronous, to manage the tensions of the film and to avoid breaks. In the case of cutting Caroll fingerprints in a film directly associated with the oven, the distance between the Caroll rollers can be adjusted to adjust to the desired width. One of the rollers can be fixed on the axis, while the spacing with the outer roller (or median, if necessary), can be controlled according to the location of the caroll fingerprints made in the film. The roller is then movable in translation on the axis to adapt the width of the perforated film. In the embodiment of Figure 3, and in the case of single-sided gluing, the upper rollers (7) can be conventional, ie solid. Indeed, as the inner face of the film is not glued, it can be based on conventional cylinders. The conditions in the enclosure are variable depending on the nature of the adhesive. In general, the temperature, as well as the relative humidity, is regulated to obtain the crosslinking of the adhesive. The temperature in the chamber is thus typically between 50 ° C and 200 ° C, preferably between 80 ° C and 160 ° C and preferably between 100 and 150 ° C; the temperature also takes into account the nature of the film (chemical nature and film thickness). The relative humidity, which can be controlled or not, advantageously is controlled, is generally between 30 and 90% RH, preferably about 50% RH. It can also be expected that the temperature regulation in the case of adhesive systems that are 1000/0 hot-cure or that the regulation of moisture in the case of adhesive systems that are 1000/0 moisture-cure. In general, adhesive systems are hot and moisturecure. It is also possible to provide baffles in the enclosure, to define different areas within this enclosure. Different conditions, in particular temperature, may be provided in the different zones 15 of the enclosure. The regulation of temperature and humidity, if necessary, is carried out in various ways. The heating may be internal or external, usually external. An extraction can be provided to improve the regulation, a low flow being useful for this purpose. It is also possible to inject steam (if dry) while avoiding condensation on the support film. In the operation of the chamber, it will advantageously be able to preheat the film entering the chamber, to immediately benefit from the efficiency of the oven (the first meter in the oven is then available for crosslinking and not to raise the temperature of the oven. movie). Counter rollers (4a) can also be provided, as described in FIG. 4 (and mentioned in FIG. 3). The presence of against-roll may be useful for training purposes by deporting the motorization, may also allow guidance, and may also be useful to avoid tearing and / or buckling (crimping between the rollers). The additional frustoconical shape (optional) shown also makes it possible, by exerting pressure between the rollers, to cause a tension (widening) of the film by mechanical adjustment. The invention also allows double sizing or double coating on both sides. This may be useful for two adhesive layers, one on each side, the composition of the two adhesive layers may be the same or different. This can also be useful in the case of the application of a release layer called "release" on the other side of the film. Indeed, it is often necessary to provide a release layer for R: \ 32100 \ 32101 BSTK \ 32101--101228-DEPOT EN.doc be able to wind the film having received the adhesive. One possibility is to coat the other side with for example a silicone emulsion, so that the film during its winding has this non-stick silicone layer facing the adhesive layer. In the state of the art, it was necessary to turn the film with a complex loading system and iron the film with the silicone coating in the dryer, whose adjustment of the operating conditions also presented problems. At the outlet of the enclosure or furnace, it eliminates by cutting (delaizage, slitting) the perforated lateral area (or median if necessary). The waste product (of the order of 5 to 7%) is then recycled. The costs related to this part of the process correspond to the current costs related to lateral cutting. A side cut is indeed necessary because it is not currently possible in practice to glue 1000/0 of the useful surface, as it is also not possible in practice to fall perfectly on a multiple of the width of adhesive tapes or labels for all items produced in a unit. A scrap rate of the order of 100/0 or more is common. The entry and exit of the Caroll Drive Enclosure may be on the same side, on opposite or adjacent sides. The flexibility of definition of the input and output permits to have only one operator for the various operations on a line which traditionally actually employs two. The invention is also directed to the enclosure comprising a Caroll drive system. The enclosure therefore comprises a multiple-locking system using Caroll rollers or rollers. Any type of support film may be used, such as polyethylene, polypropylene, polyester (eg PET), polyamide. The adhesive which is coated on a film is a crosslinkable PSA adhesive without solvent. Adhesives which are the subject of patent applications EP0106330, CA2554743 and W009 / 106699 may be mentioned. Mention may also be made of the adhesives that are the subject of the French applications on behalf of the applicant filed under the numbers 07/09027 (published under the number FR2925517 and WO2009106699) and 09/06194, the contents of which are incorporated herein by reference. The adhesive is in particular an adhesive based on polyurethane or polyether. Such an adhesive may comprise: 20 to 85% of a polyurethane or polyether comprising two hydrolysable alkoxysilane end groups; 15 to 80% of a compatible tackifying resin; and 0.01 to 3% of a crosslinking catalyst. Preferably, the heat-curable adhesive composition comprises from 40 to 65% of the polyurethane or polyether and 35 to 60% of tackifying resin.

According to one embodiment, the adhesive composition comprises a polyurethane comprising 2 hydrolyzable alkoxysilane end groups and having the formula (Ia): ## STR5 ## R 3 -N (R 4) p Si R 3 -NH-C Wherein R 'represents a divalent hydrocarbon radical comprising from 5 to 15 carbon atoms which may be aromatic or aliphatic, linear, branched or cyclic; R2 represents a linear or branched divalent alkylene radical comprising from 1 to 4 carbon atoms; - R3 represents a linear divalent alkylene radical comprising from 1 to 3 carbon atoms; R4 and R5, which are identical or different, each represents a linear or branched alkyl radical of 1 to 4 carbon atoms, with the possibility when there are several radicals R4 (or R5) that they are identical or different; n is an integer such that the number-average molar mass of the polyether block of formula - [OR 2] n - is between 300 Da and 30 kDa; M is an integer such that the number average molecular weight of the polymer of formula (Ia) is between 600 Da and 60 kDa; p is an integer equal to 0, 1 or 2. The polyurethane of formula (Ia) included in the composition according to the invention can be obtained according to the following process. In a first step, a polyurethane comprising 2 hydroxyl end groups and having the formula (IIa) is prepared: ## STR2 ## By reacting one mole of diisocyanate of formula (IIIa): NCO-R'-NCO (IIIa) with about two moles of a polyether diol of formula (IVa): H- [OR2] n-OH (IVa) which corresponds to a ratio of the number of functions N00 / OH equal to about 0.5. The reaction is carried out at a temperature between 60 and 90 ° C, for a time of about 2 to 8 hours, and optionally in the presence of a catalyst.

The polyurethane of formula (IIa) is in a second step converted to polyurethane of formula (Ia) by a silylation reaction with an isocyanatosilane of formula (Va): NCO-R3-Si (R4) p (OR5) 3 -p (Va) about one mole of polyurethane of formula (II) per 2 moles of the compound of formula (Va). These two synthesis steps are conducted under anhydrous conditions, so as to avoid the hydrolysis of the alkoxysilane groups. A typical temperature range for carrying out these reactions is from 30 ° to 120 ° C, and more preferably from 60 to 90 ° C. A slight variation with respect to the stoichiometries given above can be envisaged without inconvenience, provided however that it does not exceed 10% in the first step (synthesis of the polyurethane of formula IIa) and 2% in the second step (synthesis of the polyurethane of formula the). Reference is made to European Patent EP 0 931 800 for more details concerning the preparation of the polyurethane of formula (Ia) with end groups of alkoxysilane type. According to another embodiment, the adhesive composition comprises a polyether comprising two hydrolyzable alkoxysilane end groups of type R: having a viscosity measured at 23.degree. at 40 Pa.s and for formula (Ib): ## STR2 ## in which: ## STR2 ## in which: ## STR1 ## in which: R 'and R2, identical or different, each represent a linear or branched alkyl radical of 1 to 4 carbon atoms, with the possibility when there are several radicals R' (or R2) that they are identical or different; - R3 represents a divalent linear alkylene radical comprising 1 to 6 carbon atoms; R4 represents a linear or branched divalent alkylene radical comprising from 1 to 4 carbon atoms; n is an integer such that the number-average molar mass Mn of the polymer of formula (1) is between 20 kDa and 40 kDa; p is an integer equal to 0, 1 or 2; The polymer of formula (Ib) included in the composition according to the invention can be obtained by reacting a polyether diol of formula (IIb): H- [OR 4] n -OH (IIb) with an isocyanatosilane of formula (IIIb): NCO-R3-Si (R2) p (OR1) 3-p (IIIb) in the proportion of about one mole of polyether diol of formula (IIb) for 2 moles of the compound of formula (IIIb).

The polyether diols of formula (IIb) are widely available commercially, and the isocyanatosilanes of formula (IIIb) are also commercially available. By way of example, mention may be made of gamma-isocyanato-n-propyl-trimethoxysilane, which is available under the name Geniosil® GF 40 or else the alpha-isocyanato-n-methyl-methyldimethoxysilane which is available under the trade name Geniosil® XL 42. both from Wacker. This synthesis step is carried out under anhydrous conditions, so as to avoid the hydrolysis of the alkoxysilane groups. A typical temperature range for carrying out this reaction is from 30 ° to 120 ° C, and more preferably from 60 to 90 ° C. A slight variation by

R: \ 32100 \ 32101 BSTK \ 32101--101228-DEPOT EN.doc the stoichiometries given above can be considered without inconvenience, provided however not to exceed 20/0. Polyethers of formula (Ib) are also commercially available.

The resin is a tackifying compatible resin having a number-average molar mass of between 200 Da and 5 kDa, and chosen from resins which can be obtained: (i) by polymerization of terpene hydrocarbons and phenols, in the presence of Friedel-Crafts catalysts, or - (ii) by polymerization of alpha-methyl styrene, and optionally by reaction with phenols. With regard to the tackifying resins which may be included in the composition according to the invention, the term "compatible tackifying resin" is intended to denote a tackifying resin which, when it is mixed in the proportions 50% / 50% with the polymer of formula (1), gives a substantially homogeneous mixture. Such resins are commercially available and those obtainable by processes (i) and (ii) defined above include the following products: process (i): Dertophene® 1510 available from the company DRT having a molar mass M n of about 870 Da; Dertophene® H150 available from the same company of molar mass Mn equal to about 630 Da; Sylvarez® TP 95 available from Arizona Chemical having a molar mass M n of about 1200 Da; process (ii): Norsolene® W100 available from Gray Valley, which is obtained by polymerization of alpha-methyl styrene without the action of phenols, with a molar mass in number of 900 Da; Sylvarez® 510 which is also available from the company Arizona Chemical with a molar mass Mn of about 1740 Da, the method of obtaining comprises the action of phenols. The crosslinking catalyst that may be used in the composition according to the invention may be any catalyst known to those skilled in the art for the silanol condensation. Examples of such catalysts are organic titanium derivatives such as titanium acetyl acetonate (commercially available under the name TYZOR® AA75 from DuPont), aluminum such as aluminum chelate (commercially available under the name K-KAT ° 5218 from King Industries), amines such as 1,8-diazobicyclo (5.4.0) undecene-7 or DBU. The heat-curable adhesive composition according to the invention may be prepared by a process which comprises: a step of mixing, in an air-tight manner, preferably under an inert atmosphere, the polymer of formula (1) with the one or more tackifying resins, at a temperature between 50 and 170 ° C, preferably between 100 and 170 ° C, then - a step of cooling said mixture to a temperature ranging from 50 to 90 ° C, and preferably about 70 ° C and then - a step of incorporating into said mixture of the catalyst and, if appropriate, the desiccant and other optional components. The coating step is carried out conventionally by means of known coating devices, such as for example a lip or curtain-type nozzle, or by roller. It uses an adhesive composition weight ranging from 3 to 500 g / m 2, preferably from 10 to 250 g / m 2. The material that can be used for the support layer is, for example, paper or a film of a single or multi-layered polymeric material, as indicated above.

The time required for the crosslinking can vary within wide limits, for example between 1 second and 10 minutes, preferably between 30 seconds and 5 minutes. The residence time in the climatic chamber is adapted accordingly. This step of thermal crosslinking has the effect of creating - between the polymer chains of the polyurethane or polyether and under the action of moisture - siloxane type bonds which lead to the formation of a three-dimensional polymeric network. The thus crosslinked adhesive composition is a pressure-sensitive adhesive which provides the coated carrier layer with desirable tack and tack.

The invention is not limited to the description of hot-crosslinkable solvent-free hot-melt adhesive coating, but may be applicable to other fields, such as paper sizing and bonding. generally conveying (conveying, transferring) media in the form of films having been coated with a tacky material at a time of the process.

In such areas, it is sought to avoid contact between the sticky parts and the device. An accumulator can be provided by applying the Caro11 training principle. R: \ 32100 \ 32101 BSTK \ 32101--101228-DEPOT EN.doc