NOVEL COMPOSITIONS WHICH ARE CROSS-LINKABLE BY HEATING, AND CORRESPONDING SELF-ADHESIVE ARTICLES

Abstract

1) A heat-crosslinkable adhesive composition, comprising: at least one polymer (A) comprising a hydrolyzable alkoxysilane group; at least one tackifying resin (B); at least one silsesquioxane resin (C); and at least one crosslinking catalyst (D).

2) A self-adhesive article comprising a support layer coated with a self-adhesive layer consisting of the adhesive composition in the crosslinked state.

Claims

1-15. (canceled)

16. A heat-crosslinkable adhesive composition comprising: at least one polymer (A) comprising a hydrolyzable alkoxysilane group; at least one tackifying resin (B); at least one silsesquioxane resin (C); and at least one crosslinking catalyst (D).

17. The adhesive composition as claimed in claim 16, wherein the polymer (A) comprises at least one hydrolyzable group of formula (I):
—Si(R.sup.4).sub.p(OR.sup.5).sub.3-p  (I) wherein: R.sup.4 represents a linear or branched alkyl radical comprising from 1 to 4 carbon atoms, with the possibility that when there are several radicals R.sup.4, these radicals are identical or different; R.sup.5 represents a linear or branched alkyl radical comprising from 1 to 4 carbon atoms, with the possibility that when there are several radicals R.sup.5, these radicals are identical or different, with the possibility that two groups OR.sup.5 may be engaged in the same ring; p is an integer equal to 0, 1 or 2.

18. The adhesive composition as claimed in claim 17, wherein the polymer (A) corresponds to one of the formulae (II), (III) or (IV): ##STR00015## wherein: P represents a saturated or unsaturated, linear or branched polymeric radical optionally comprising one or more heteroatoms, and having a number-average molar mass ranging from 100 g/mol to 48,600 g/mol, R.sup.1 represents a divalent hydrocarbon-based radical comprising from 5 to 15 carbon atoms, which may be aromatic or aliphatic, linear, branched or cyclic, R.sup.3 represents a linear or branched divalent alkylene radical comprising from 1 to 6 carbon atoms, X represents a divalent radical chosen from —NH—, —NR.sup.7— or —S—, R.sup.7 represents a linear or branched alkyl radical comprising from 1 to 20 carbon atoms and which may also comprise one or more heteroatoms, and f is an integer ranging from 1 to 6.

19. The adhesive composition as claimed in claim 18, wherein the polymer (A) corresponds to one of the formulae (II′), (III′) or (IV′): ##STR00016## wherein: R.sup.2 represents a saturated or unsaturated, linear or branched divalent hydrocarbon-based radical optionally comprising one or more heteroatoms, and having a number-average molar mass ranging from 100 g/mol to 48,600 g/mol, and n is an integer greater than or equal to 0.

20. The adhesive composition as claimed in claim 18, wherein the polymer (A) is a silyl polymer of formula (III′) wherein R.sup.2 is a divalent radical derived from a polyether.

21. The adhesive composition as claimed in claim 16, wherein the resin (B) is chosen from: i. resins obtained by polymerization of terpene hydrocarbons and of phenols, in the presence of Friedel-Crafts catalysts; ii. resins obtained by a process comprising the polymerization of α-methylstyrene, it also being possible for said process to comprise a reaction with phenols; iii. rosins of natural origin or modified rosins; iv. resins obtained by hydrogenation, polymerization or copolymerization (with an aromatic hydrocarbon) of mixtures of unsaturated aliphatic hydrocarbons containing approximately 5, 9 or 10 carbon atoms obtained from petroleum fractions; v. terpene resins; vi. copolymers based on natural terpenes; or vii. acrylic resins having a viscosity at 100° C. of less than 100 Pa.Math.s.

22. The adhesive composition as claimed in claim 16, wherein the silsesquioxane resin (C) has the general formula:
[RSiO.sub.3/2]t wherein R, which may be identical or different in nature, represents an organic radical and t is an integer which may range from 6 to 12.

23. The adhesive composition as claimed in claim 22, wherein the silsesquioxane resin (C) corresponds to the general formula (V): ##STR00017## wherein each one from among R′.sup.1 to R′.sup.8 represents, independently of each other, a group chosen from: a hydrogen atom, a radical chosen from the group consisting of a linear or branched C1-C4 alkoxy radical, a linear or branched alkyl radical comprising from 1 to 30 carbon atoms, an alkenyl radical comprising from 2 to 30 carbon atoms, an aromatic radical comprising from 6 to 30 carbon atoms, an allyl radical comprising from 3 to 30 carbon atoms, a cyclic aliphatic radical comprising from 3 to 30 carbon atoms and an acyl radical comprising from 1 to 30 carbon atoms, and a group —OSiR′.sup.9R′.sup.10 wherein R′.sup.9 and R′.sup.10 each represents, independently of each other, a hydrogen atom or a radical chosen from the group consisting of linear or branched C1-C4 alkyls, linear or branched C1-C4 alkoxys, C2-C4 alkenyls, a phenyl, a C3-C6 allyl radical, a cyclic C3-C8 aliphatic radical and a C1-C4 acyl radical; on condition: that at least one radical from among the radicals R′.sup.1 to R′.sup.8 is a C1-C4 alkoxy radical; and that at least one radical from among the radicals R′.sup.1 to R′.sup.8 is a phenyl radical.

24. The adhesive composition as claimed in claim 16, wherein it is in the form of a one-component composition comprising: from 3% to 90% by weight of the polymer (A); from 15% to 80% by weight of the tackifying resin (B); from 0.1% to 30% by weight of the silsesquioxane resin (C); and from 0.01% to 10% by weight of the crosslinking catalyst (D); wherein the weight percentages are indicated on the basis of the total weight of one-component composition.

25. The adhesive composition as claimed in claim 16, wherein it is in the form of a multicomponent composition comprising: a composition U comprising: the polymer (A); and the tackifying resin (B); and a composition V comprising: the crosslinking catalyst (D); and at least one compound (E) chosen from: a compound (E1) with a number-average molecular mass ranging from 300 g/mol to 100,000 g/mol; and a compound (E2) with a vapor pressure at 20° C. of greater than or equal to 0.08 kPa; the silsesquioxane resin (C) being included in composition U or in composition V.

26. A self-adhesive article comprising a support layer coated with a self-adhesive layer, wherein said self-adhesive layer comprises the adhesive composition of claim 16, in the crosslinked state.

27. A process for manufacturing the self-adhesive article of claim 26, said process comprising: a) preheating to a temperature of between 40 and 130° C. a heat-crosslinkable adhesive composition comprising: i. at least one polymer (A) comprising a hydrolyzable alkoxysilane group; ii. at least one tackifying resin (B); iii. at least one silsesquioxane resin (C); and iv. at least one crosslinking catalyst; b) c) application of said composition by coating onto a bearing surface; d) crosslinking of said composition, by heating to a temperature ranging from 50 to 200° C.; and then e) laminating or transferring the layer of crosslinked adhesive composition onto a support layer or onto a nonstick protective film.

28. A process for manufacturing a self-adhesive article comprising a support layer coated with a self-adhesive layer, wherein the self-adhesive layer comprises the adhesive composition of claim 25, the process comprising a) preheating to a temperature of between 40 and 130° C. the heat-crosslinkable adhesive composition of claim 25; b) application of said composition by coating onto a bearing surface; wherein application is performed using a facility for the hot application of said adhesive composition; c) crosslinking of said composition, by heating to a temperature ranging from 50 to 200° C.; and then d) laminating or transferring the layer of crosslinked adhesive composition onto a support layer or onto a nonstick protective film, wherein the facility for the hot application of the adhesive composition comprises: an application nozzle for applying the multicomponent adhesive composition; a first line for feeding composition U included in the multicomponent adhesive composition to be applied in fluid form; a second line for feeding composition V included in the multicomponent adhesive composition to be applied in fluid form; a third line for feeding the application nozzle with the multicomponent adhesive composition to be applied in fluid form; and a mixer for mixing at least compositions U and V of the multicomponent adhesive composition; wherein step (b) further comprises: supplying the first feed line with at least composition U; supplying the second feed line with at least composition V; mixing at least composition U and composition V of the multicomponent composition using a mixer; and hot application of the mixed multicomponent adhesive composition onto a support layer with the aid of the application nozzle.

29. The process as claimed in claim 28, wherein the mixer is a dynamic mixer.

30. A bonding method using the self-adhesive adhesive article as defined in claim 26, comprising the following steps: a) removing the nonstick protective layer, when such a layer is present; b) applying the self-adhesive article to one surface of a product; and c) applying a pressure to said article.

Description

[0427] FIG. 1 shows a schematic representation of one embodiment of a facility 20 suitable for performing the process for manufacturing the self-adhesive article according to the invention.

[0428] According to one embodiment, as a result of the at least double supply, composition V (66) is separated from composition U (68) up to the mixer (30) placed between the lines for feeding at least compositions U (88a) and V (66a), on the one hand, and the line (88) for feeding the multicomponent adhesive composition to be applied, on the other hand. In other words, the mixer (30) is in-line and allows a step of homogeneous mixing of compositions (66) and (68) supplied separately to be performed. The injection of composition V (66) into composition U (68) is performed in the mixer (30), as illustrated, for example, in FIG. 1, to allow immediate mixing of these compositions.

[0429] The various compositions constituting the multicomponent adhesive composition according to the invention may be totally separated, i.e. each composition is supplied separately to the hot application facility (20). In particular, the injection of composition A (68), of composition B (66) and of optional additional composition(s) of the multicomponent adhesive composition is performed in the mixer (30).

[0430] In the facility according to the invention, composition U (68) may be heated in the storage reservoir (82) by means of a heating means (44), without bringing about crosslinking of composition U (68) due to the separation of composition V (66), comprising at least the crosslinking catalyst. Heating in the storage reservoir (82), represented in the form of a drum, in particular makes it possible to reduce the viscosity of composition U (68), to facilitate the pumping in the facility (20), such as with the aid of a pump (46), before any contact with the separate composition V (66).

[0431] This heating means (44) (preferably being a hotplate) notably contributes toward raising composition U (68) to the application temperature. The application temperature notably corresponds to a temperature at which the adhesive composition to be applied has a viscosity that is low enough to allow the application, in other words the coating, of the mixed multicomponent adhesive composition (80) onto the surface (96).

[0432] Specifically, after mixing compositions V (66) and U (68), the multicomponent adhesive composition (80) is constituted and can be applied hot to the support (96) with the aid of an application nozzle (50). A temperature for application of the multicomponent adhesive composition (80) may thus correspond to a temperature at which the viscosity of the multicomponent adhesive composition is less than or equal to 50 Pa.Math.s, preferably less than or equal to 10 Pa.Math.s. By way of example, the multicomponent adhesive composition (80) may have a viscosity of 5±1 Pa.Math.s at an application temperature ranging from 60° C. to 120° C. Following the application of the multicomponent adhesive composition (80) to the surface (96), the coated support (98) is subjected to a controlled temperature, and optionally to a controlled moisture level, to allow the crosslinking of the multicomponent adhesive composition.

[0433] The controlled temperature may be obtained with the aid of an oven or a chamber. The controlled temperature corresponds to a temperature of crosslinking of the multicomponent adhesive composition (80) and is, for example, between 50° C. and 200° C., preferably between 80° C. and 160° C., in particular between 100° C. and 150° C.

[0434] Similarly, composition V (66) may itself also be heated before it is mixed with composition U (68) without any risk of crosslinking before they are mixed. This is likewise the case for any composition of the multicomponent composition according to the invention.

[0435] The heating of all of the separate compositions V (66) and U (68) before mixing them notably makes it possible to bring these components to the application temperature without any risk of crosslinking before they are mixed in the mixer (30).

[0436] The self-adhesive article according to the invention may finally be used in a bonding method which is also the subject of the invention, characterized in that it comprises the following steps:

[0437] a) removing the nonstick protective layer, when such a layer is present;

[0438] b) applying the self-adhesive article to one surface of a product; and

[0439] c) applying a pressure to said article.

[0440] In step b), the self-adhesive article is applied so that the self-adhesive part of the article (formed by the self-adhesive layer) is facing the surface of the product.

[0441] According to an embodiment in which the self-adhesive article is a double-sided article, the bonding method also comprises a step in which either a second surface of a product is applied to the article bonded to the first surface of a product, or the article bonded to the first surface of a product is applied to a second surface of a product.

[0442] The examples that follow are given purely by way of illustration of the invention and should not be interpreted in order to limit the scope thereof.

EXAMPLE A (REFERENCE): HEAT-CROSSLINKABLE ADHESIVE COMPOSITION BASED ON GENIOSIL© STP-E30 WITHOUT SILSESQUIOXANE

[0443] A1. Preparation of the Composition:

[0444] The composition given in table 1 is prepared by first of all introducing the tackifying resin Dertophene® H150 into a glass reactor under vacuum and heated to approximately 160° C. Then, once the resin has fully melted, the Geniosil® STP-E30 is added.

[0445] The mixture is stirred under vacuum for 15 minutes and then cooled to 70° C. The catalyst (K-KAT® 5218) is then introduced. The mixture is kept under vacuum and with stirring for a further 10 minutes.

[0446] A2. Preparation of a PET Support Layer Coated with the Crosslinked Composition, at a Weight Per Unit Area Equal to 60 g/m.sup.2:

[0447] A rectangular sheet of polyethylene terephthalate (PET) with a thickness of 50 μm and dimensions of 20 cm by 40 cm is used as support layer.

[0448] The composition obtained in point A1 is preheated to a temperature close to 100° C. and is introduced into a cartridge, from where a bead is extruded which is deposited close to the edge of the sheet parallel to its width.

[0449] The composition included in this bead is then spread over the whole of the surface of the sheet, so as to obtain a uniform layer of substantially constant thickness. A film spreader (also known as a film applicator) is used to do this, and is moved from the edge of the sheet to the opposite edge. A layer of composition corresponding to a weight per unit area of 60 g/m.sup.2 is thus deposited, which represents approximately a thickness of the order of 60 μm.

[0450] The PET sheet thus coated is then placed in an oven at 120° C. and under a humid atmosphere (4% relative humidity) for 5 minutes for crosslinking of the composition, and is then laminated onto a protective nonstick layer consisting of a rectangular silicone-treated film sheet of the same dimensions.

[0451] The triple layer obtained is subjected to the two tests described below.

[0452] 180° Peel Test on a Stainless-Steel Plate:

[0453] The adhesive power is evaluated by the 180° peel test on a stainless-steel plate, as described in the FINAT method No. 1, published in the FINAT Technical Handbook, 6.sup.th edition, 2001. FINAT is the International Federation of Self-Adhesive Label Manufacturers and Converters. The principle of this test is as follows:

[0454] A test specimen in the form of a rectangular strip (25 mm×175 mm) is cut out from the triple layer obtained previously.

[0455] This specimen, after it has been prepared, is stored for 7 days at a temperature of 70° C. and under an atmosphere with a humidity of 50%. It is then attached over two-thirds of its length (after removal of the corresponding portion of protective nonstick layer) to a substrate consisting of a stainless-steel plate. The assembly obtained is left at ambient temperature for 20 minutes. It is then placed in a tensile testing device capable, starting from the end of the rectangular strip which has remained free, of performing the peeling or detachment of the strip at an angle of 1800 and with a separation speed of 300 mm per minute.

[0456] The device measures the force required to detach the strip under these conditions.

[0457] The corresponding result is expressed in N/cm and indicated in table 1.

[0458] Tack Test (Also Known as the Loop Test):

[0459] The initial grab (or tack) is evaluated by the “loop” tack test described in the FINAT method No. 9, the principle of which is as follows:

[0460] A test specimen in the form of a rectangular strip (25 mm×175 mm) is cut out from the triple layer obtained previously. This specimen, after it has been prepared, is stored for 7 days at a temperature of 70° C. and under an atmosphere with a humidity of 50%. After removing all of the protective nonstick layer, the two ends of this strip are joined so as to form a loop, the adhesive layer of which is facing outward. The two joined ends are placed in the movable jaw of a tensile testing device capable of imposing a displacement speed of 300 mm/minute along a vertical axis with to-and-fro possibility. The lower part of the loop placed in the vertical position is first brought into contact with a horizontal sheet of glass of 25 mm by 30 mm over a square region with a side length of approximately 25 mm. Once this contact has been established, the direction of displacement of the jaw is reversed. The tack is the maximum value of the force required for the loop to become completely detached from the sheet.

[0461] The corresponding result is expressed in N/cm.sup.2 and is indicated in table 1.

[0462] A3. Preparation of a PET Support Layer with a Nonstick Surface Treatment and Coated with the Crosslinked Composition, at a Weight Per Unit Area Equal to 500 g/m.sup.2:

[0463] A PET support layer coated with the crosslinked composition obtained in point A1 is prepared by repeating the protocol of point A2, with: [0464] a PET support layer which has received beforehand a nonstick surface treatment, [0465] a weight per unit area for the layer of composition (deposited on the nonstick side of the support) equal to 500 g/m.sup.2, which represents an approximate thicknesses of the order of 500 μm for said layer; and [0466] a crosslinking time in the oven of 30 minutes.

[0467] The triple layer obtained is subjected to the test described below.

[0468] Measurement of the Tensile Strength and the Elongation at Break by Tensile Testing:

[0469] The principle of the measurement consists in drawing, in a tensile testing device, the movable jaw of which is displaced at a constant speed equal to 300 mm/minute, a test specimen consisting of the crosslinked adhesive composition, and in recording, at the moment when the test specimen breaks, the applied force (in N) and also the elongation of the test specimen (in %).

[0470] The test specimen is 9 cm long and 2.5 cm wide for a thickness of 500 μm and is obtained by cutting out, after having removed the PET support layer and the protective nonstick layer from the triple layer obtained above.

[0471] The results of the measurements obtained are given in table 1.

EXAMPLES 1 AND 2 (ACCORDING TO THE INVENTION): HEAT-CROSSLINKABLE ADHESIVE COMPOSITION BASED ON GENIOSIL® STP-E30 WITH 5% AND 10% BY WEIGHT OF SILSESQUIOXANE

[0472] Example A is repeated with the compositions given in table 1.

[0473] These compositions are prepared in accordance with protocol A1, except that the Dow Corning® 3074 is introduced at the same time as the catalyst.

[0474] The results of the peel, tack and tensile tests are also indicated in table 1. As regards the tensile test, breaking of the test specimen is not observed under the test conditions.

[0475] A significant increase in the peel and the tack, and also in the elongation at break and the tensile strength relative to the reference example A, are observed.

EXAMPLE B (REFERENCE): HEAT-CROSSLINKABLE ADHESIVE COMPOSITION BASED ON GENIOSIL® STP-E30 WITHOUT SILSESQUIOXANE

[0476] The composition given in table 2 is prepared as indicated in point A1 of example A, replacing the tackifying resin Dertophene® H150 with the tackifying resin Picco® AR100.

[0477] The protocol indicated in point A2 is repeated with the composition thus obtained, so as to prepare a PET support layer coated with the crosslinked composition at a weight per unit area equal to 60 g/m.sup.2.

[0478] The triple layer obtained is then subjected to the three tests described below. [0479] the 180° peel test on a stainless-steel plate, performed in accordance with example A, except that, after it has been prepared, the test specimen is stored for one day at 23° C.; [0480] the 180° peel test on a high-density polyethylene (or HDPE) plate, performed in accordance with example A, except that, after it has been prepared, the test specimen is stored for one day at 23° C. and the stainless-steel plate used as substrate is replaced with an HDPE plate; [0481] the 180° peel test on a polypropylene (or PP) plate, performed in accordance with example A, except that, after it has been prepared, the test specimen is stored for one day at 23° C. and the stainless-steel plate used as substrate is replaced with a PP plate.

[0482] The results obtained are collated in table 2.

EXAMPLE 3 (ACCORDING TO THE INVENTION): HEAT-CROSSLINKABLE ADHESIVE COMPOSITION BASED ON GENIOSIL® STP-E30 WITH 5% BY WEIGHT OF SILSESQUIOXANE

[0483] Example B is repeated with the composition given in table 2.

[0484] This composition is prepared in accordance with protocol A1, except that the Dow Corning® 3074 is introduced at the same time as the catalyst.

[0485] The results of the peel tests are also indicated in table 2.

[0486] Relative to the reference example B, a significant increase in the peel force is observed on the three substrates tested.

TABLE-US-00001 TABLE 1 Content in weight/weight % Ingredient Example A Example 1 Example 2 (A) Geniosil ® STP-E30 52 49.4 46.7 (B) Dertophene ® H150 47 44.6 42.3 (C) Dow Corning ® 3074 — 5 10 (D) K-KAT ® 5218 1 1 1 180° C. peel (N/cm) 8.0 11.8 14.1 Tack (N/cm.sup.2) 5.9 9.5 9.9 Tensile strength (N) 16 no breaking no breaking Elongation at break (%) 823 >1000 >1000

TABLE-US-00002 TABLE 2 Content in weight/weight % Ingredient Example B Example 3 (A) Geniosil ® STP-E30 47 42.4 (B) Picco ® AR100 52 51.6 (C) Dow Corning ® 3074 — 5 (D) K-KAT ® 5218 1 1 180° peel on a stainless-steel plate 10.5 13.2 (N/cm) 180° peel on an HDPE plate (N/cm) 3.7 5.4 180° C. peel on a PP plate (N/cm) 9.5 11.5