EP3997185A1

EP3997185A1 - Hmpsa crosslinkable under uv irradiation

Info

Publication number: EP3997185A1
Application number: EP20750317.8A
Authority: EP
Inventors: Amandine RAFAITIN; Alexandre GOURLAIN; Christophe Robert
Original assignee: Bostik SA
Current assignee: Bostik SA
Priority date: 2019-07-10
Filing date: 2020-07-06
Publication date: 2022-05-18
Also published as: US20220315811A1; AU2020312223A1; JP2022540852A; FR3098520A1; KR20220032549A; WO2021005299A1; CN114096630A; FR3098520B1; CA3140840A1; MX2021015444A

Abstract

1) A UV cross-linkable HMPSA composition comprising: - 10-24% by weight of a block copolymer which comprises a styrene block and a polybutadiene block comprising at least 25% by weight of the 1,2-vinyl unit; - 43-65% by weight of a tackifying resin obtained by polymerisation and subsequently total or partial hydrogenation of a C9 cut, having a softening point of 80-150°C; - 10-25% by weight of a petroleum hydrocarbon oil; and - a suitable content of a photoinitiator (D). 2) A self-adhesive article comprising a backing layer (b) coated with a self-adhesive layer (a) consisting of the HMPSA composition in the cross-linked state. 3) A method for manufacturing the article 2), comprising: - preheating the HMPSA composition to a temperature of 70-80°C; - applying the HMPSA composition, by coating, to a bearing surface; cross-linking the HMPSA composition by UV irradiation to form the layer of cross-linked adhesive composition (a); and subsequently - laminating or transferring the layer (a) onto a backing layer or an anti-adhesive protective film.

Description

HMPSA CROSS-LINKABLE UNDER UV IRRADIATION

A subject of the present invention is a hot-melt self-adhesive composition (HMPSA) which can be crosslinked under UV irradiation, as well as a self-adhesive article comprising an adhesive layer constituted by said crosslinked composition. Said article is particularly useful for the manufacture of self-adhesive tapes and / or labels, and has

advantageously an adhesive power which can be maintained over a wide temperature range. Finally, a subject of the invention is a method for manufacturing said article.

Self-adhesives (also called pressure-sensitive adhesives or alternatively, in English "Pressure Sensitive Adhesives" or PSA) are substances giving the support which is coated therewith an immediate tackiness at room temperature (often referred to as " tack "), which allows its instant adhesion to a substrate under the effect of a light and brief pressure. PSAs are used in the manufacture of self-adhesive tapes for various uses. We can cite for example, in addition to the transparent adhesive tape widely used in everyday life: the shaping and assembly of cardboard packaging; protection of surfaces for painting work, in construction; the maintenance of electric cables in the transport industry; the gluing of the carpets with double-sided adhesive tapes. PSAs are also used for the manufacture of self-adhesive labels which are affixed to articles for the purpose of presenting information (such as barcode, denomination, price) and / or for decorative purposes.

With a view to the manufacture of self-adhesive tapes and / or labels, PSAs are often applied by continuous coating processes over the entire surface of a support layer (if applicable printable) of large dimensions , in an amount (generally expressed in g / m ² ) and designated below by the term "basis weight". The support layer is for example made of paper or film of a polymer material with one or more layers. The adhesive layer which covers the support layer can itself be covered with a protective non-stick layer (often referred to by the English name of “release liner”), for example consisting of a silicone film. The resulting multilayer system is usually packaged by winding in the form of large coils up to 2 m in width and 1 m in diameter, which can be stored and transported. These multilayer systems can be subsequently transformed into self-adhesive tapes by cutting and packaging in rolls of determined width and length.

These multi-layered systems can also be converted into self-adhesive labels applicable by the end user, by converting processes which include printing the desired informative and / or decorative elements on the printable side of the backing layer, then die-cutting. the desired shape and dimensions. The protective release layer can be easily removed without modifying the adhesive layer which remains attached to the backing layer. After separation of its protective non-stick layer, the label is applied to the article to be coated either manually or using labelers on automated packaging lines.

PSAs allow, because of their high tack at room temperature, a rapid setting or adhesion of the self-adhesive tape and / or the label on the substrate (or article) to be coated (for example, in the case of tapes, on packaging boxes to be shaped, or, in the case of labels, on bottles), suitable for obtaining high industrial production rates.

There is a field of application of PSAs for which it is desirable that the adhesive power of the tapes and / or labels on the substrate is also maintained when the adhesive joint (also called adhesive joint) which ensures the fixing is exposed (likewise , therefore, that the article coated with the tape and / or the label) at a temperature which can vary over a wide range. By way of example, mention may be made of the use of self-adhesive tapes for the assembly of parts for which good thermal resistance is necessary as in the case, for example, of the interior trim of airplanes or other vehicles. Mention may also be made of the placing of labels on certain components of automobiles (or other vehicles) located near the engine, or on packaging designed to receive a hot liquid during packaging, or on items (such as tires) which are hot-labeled, right off the production line.

Hot Melt Pressure Sensitive Adhesive or HMPSA (Hot Melt Pressure Sensitive Adhesive) are substances that are solid at room temperature, substantially free from solvent and water, which are deposited (or coated) on a support in the molten state. , and provide the latter, after cooling, with a high tack and adhesive power on various substrates. However, the corresponding compositions generally comprise a thermoplastic polymer, such as a styrenic block copolymer (hereinafter referred to as SBC, abbreviation of the corresponding English expression Styrenic Block Copolymer), so that the adhesive joint which ensures the attachment of the support for the substrate does not exhibit, at high temperature, all the resistance (or cohesion) necessary for the field of application referred to above.

Hot-melt self-adhesive compositions crosslinkable under UV irradiation are already known in the prior art for their resistance to high temperature.

Thus, application EP 1 123 362 B1 from KRATON describes an adhesive composition which comprises a specific styrenic block copolymer in combination with a tackifying resin and a totally or partially saturated oil. Said co-polymer comprises a polybutadiene block which itself comprises at least 25% by weight of the 1,2-vinyl unit. This composition is crosslinkable under UV irradiation and has a high adhesive power in addition to its resistance to high temperature.

International application WO 01/55276 by LULLER describes an adhesive composition crosslinkable by UV radiation, which comprises a specific styrenic block copolymer, a tackifying resin and a plasticizer. Besides a terminal styrenic block, said copolymer comprises as middle block a conjugated diene, preferably 1,3-butadiene and / or isoprene, which is modified by a 1,2-vinyl group pendant on the main chain of said middle block , at a concentration sufficient for said copolymer to crosslink upon exposure to a source of radiation.

TESA's US6887919 B2 patent describes a pressure-sensitive adhesive composition which comprises a first SBC whose styrene block content is greater than 20% by weight, as a mixture with a styrenic block copolymer crosslinkable by exposure to UV, in particular an SBC with an elastomeric block containing more than 30% by weight of the vinyl-1,2 unit.

The object of the present invention is to provide an HMPSA composition which can be crosslinked under UV irradiation, which, after coating on a support and then crosslinking, leads to a pressure-sensitive adhesive having improved properties of adhesive power and tack.

Another object of the invention is that the adhesive joint ensuring the fixing of the self-adhesive support thus obtained on a substrate is resistant to a higher temperature, in other words, keeps the required cohesion over a wide temperature range, including for high PSA grammages.

Such objects are particularly desirable with a view to the use of said HMPSA composition for obtaining high performance pressure sensitive tapes (or labels).

Self-adhesive hot melt composition crosslinkable under UV irradiation:

The subject of the invention is therefore firstly a hot-melt self-adhesive composition (HMPSA) crosslinkable under UV irradiation, comprising, on the basis of the total weight of said composition:

- from 10 to 24% by weight of a block copolymer (A) which comprises at least:

- an Al block consisting of an aromatic hydrocarbon repeating unit substituted by a vinyl group, and

a polybutadiene A2 block comprising at least 25% by weight of the 1,2-vinyl unit, based on the total weight of said polybutadiene block;

- from 43 to 65% by weight of a tackifying resin (B) obtained by polymerization, then total or partial hydrogenation of a cut of petroleum origin of unsaturated or aromatic hydrocarbons of C9 type, said resin (B) having a softening point ranging from 80 to 150 ° C;

- 10 to 25% by weight of a liquid plasticizer (C) consisting of a fully or partially saturated hydrocarbon oil of petroleum origin; and

- of an appropriate content of a photoinitiator (D).

In the absence of any indication to the contrary, the percentages used in the present text to express quantities correspond to weight / weight percentages.

It was found that the composition according to the invention makes it possible to obtain

advantageously, after coating on a support of polyethylene terephthalate (PET) at a rate of 60 g / m ² , then crosslinking by UV, an improved permanent adhesion of said coated support on a stainless steel substrate. Said adhesion corresponds to an adhesive power (measured by the peel test, or peel, at 180 ° on stainless steel described below) advantageously greater than 18 N / 2.54 cm. The tack of this same support at room temperature (measured by the instantaneous adhesion test of the loop on stainless steel described below) is advantageously between 10 and 50 N / (2.54 cm) ² . Finally, the adhesive joint formed after application to a stainless steel substrate of this same support ensures its fixing in a temperature range of up to at least 160 ° C., this temperature being evaluated according to the test known by the English name of Shear Adhesion Failure Temperature (or SAFT).

Block copolymer (A):

The HMPSA composition according to the invention comprises 10 to 24% by weight of a block copolymer (A) which comprises at least:

a polybutadiene A2 block comprising at least 25% by weight of the vinyl-1,2 unit, based on the total weight of said polybutadiene block.

According to a preferred variant, the Al block is a styrenic block (or, more precisely, a polystyrene block). Preferably, the block copolymer (A) comprises 2 Al blocks. The content of the Al blocks varies from 10 to 50% by weight, preferably from 12 to 35%, based on the total weight of the copolymer (A).

The polybutadiene A2 block comprises in its chain a repeating unit called vinyl-1,2 and of formula:

The content by weight of the 1,2-vinyl unit in the polybutadiene A2 block is at least 25% by weight based on the total weight of said polybutadiene block, and is preferably in a range of 30 to 70% by weight. weight, and even more preferably from 35 to 65% by weight.

The block copolymer (A) can be linear or radial and typically has the structure:

A1-A2-A1; or A1-A2; or

(A1-A2) _n Y where n is an integer of 2 to 100, preferably 2 to 20, more preferably 2 to 6 and Y is the residue of a coupling agent.

Reference is made, for ample information relating to the description and to the preparation of the block copolymer (A), to patent application EP 1123362B1 from KRATON and to US patent 5804663 from SHELL. A block copolymer (A) Preferred is also commercially available under the trademark KRATON ^® D-KX222 which is a copolymer of which the Al content styrene block is about 18% by weight and A2 polybutadiene block content is about 82 % by weight, based on the total weight of the copolymer (A). Said A2 block comprises approximately 57% by weight of 1,2-vinyl unit.

The HMPSA composition according to the invention comprises one or more block copolymers (A) as defined above. According to one embodiment, the HMPSA composition according to the invention does not comprise any thermoplastic polymer other than the copolymer (s) (A), and in particular no other styrene block copolymer than the said block copolymer (or copolymers) (A). ).

According to a preferred embodiment, the content of the block copolymer (A) in the HMPSA composition according to the invention is within a range ranging from 12 to 19% by weight, more preferably from 15 to 19%, and even more preferably from 15 to 18%.

Tackifying resin (B):

The HMPSA composition according to the invention comprises from 43 to 65% by weight of a tackifying resin (B) obtained by polymerization, then total or partial hydrogenation of a cut of petroleum origin of unsaturated or aromatic hydrocarbons of C9 type, said resin (B) having a softening point ranging from 80 to 150 ° C.

According to a preferred variant, the tackifying resin (s) (B) used have a softening temperature of between 90 and 120 ° C, even more

preferably between 95 and 105 ° C.

The softening temperature is determined in accordance with the standardized test ASTM E 28, the principle of which is as follows. A brass ring with a diameter of about 2 cm is filled with the resin to be tested in the molten state. After cooling to room temperature, the ring and the solid resin are placed horizontally in a thermostatically controlled glycerin bath, the temperature of which can vary by 5 ° C. per minute. A steel ball with a diameter of approximately 9.5 mm is centered on the solid resin disc. The softening temperature is - during the temperature rise phase of the bath at a rate of 5 ° C. per minute - the temperature at which the resin disc creeps from a height of 25.4 mm under the weight of the ball. Tackifying resins (B) are commercially available, and mention may be made, for example, of the following products:

- Regalite ^® SI 100 available from the company EASTMAN, which is a fully hydrogenated resin, the softening temperature of which is 100 ° C. and the average molecular mass by weight is 830 g / mole;

- the Regalite ^® S5100 available from the same company EASTMAN, which is a partially hydrogenated resin whose softening temperature is 100 ° C and the average molecular weight is 900 g / mol; or

- Regalite ^® S7100 still available from the company EASTMAN, which is a partially hydrogenated resin, the softening temperature of which is 102 ° C. and the average molecular mass by weight is 900 g / mole.

According to a preferred variant, the HMPSA composition according to the invention comprises from 50 to 65% of tackifying resins, even more preferably from 55 to 65% by weight.

Liquid plasticizer (C):

The HMPSA composition according to the invention comprises 10 to 25% by weight of a liquid plasticizer (C) consisting of a fully or partially saturated hydrocarbon oil of petroleum origin.

These oils are generally obtained from petroleum by various refining steps, including as the last purification step, catalytic hydrogenation. They generally have a very low aromatic carbon content (for example less than 10% by weight, preferably 5%), a high paraffinic carbon content (for example greater than 50% by weight, preferably 60%), and an average naphthenic carbon content (for example between 25 and 50% by weight).

According to a preferred variant, the liquid plasticizer (C) consists of an oil whose average molecular mass, measured according to the ASTM D 2502 method, is less than or equal to 2000 g / mol, preferably less than or equal to 1000 g / mole and even more preferably less than or equal to 500 g / mole.

According to another preferred variant, the liquid plasticizer (C) used is such that its kinematic viscosity at 100 ° C is within a range ranging from 7 to 11 mm ² / s.

The oils which can be used as liquid plasticizers (C) are commonly available industrially; mention may be made Primol ^® 352, of EXXONMOBIL whose Carbon contents of paraffinic, naphthenic and aromatic types, are respectively about 68%, 32% and 0% by weight. The average molecular weight, measured according to ASTM D 2502 method, of Primol ^® 352 is 480 g / mol, and the kinematic viscosity measured at 100 ° C is 8.5 mm ² / s.

According to a preferred variant, the HMPSA composition according to the invention comprises from 14 to 23% by weight of the liquid plasticizer (C).

Photoinitiator (D):

The HMPSA composition according to the invention comprises a photoinitiator (D), which is used to initiate the radical polymerization reaction which occurs upon exposure of the composition to radiation, in particular UV. Any photoinitiator known for this purpose can be used as compound (D), such as a benzophenone derivative.

Mention may in particular be made of 2,2-dimethoxy-2-phenylacetophenone, which is marketed, for example, by the company IGM RESINS under the name

OMNIRAD ^® BDK.

Such photoinitiators can be included in the composition according to the invention in a content ranging from 0.05 to 3% by weight, preferably from 1% to 2.5%.

Liquid polbutadiene resin (E):

According to one embodiment, the HMPSA composition according to the invention may further comprise up to 25% by weight of a liquid polybutadiene (E) of low molecular weight.

According to a preferred variant, the number-average molecular mass Mn of the liquid polybutadiene (E) is within a range ranging from 1500 to 5500 g / mole, preferably from 2000 to 4500 g / mole.

According to another preferred variant, the liquid polybutadiene (E) is such that its Brookfield viscosity measured at 45 ° C. ranges from 6 to 60 Pa.s, preferably from 10 to 40 Pa.s.

The polymerization of 1,3-butadiene can be carried out according to a trans-1,4 or a cis-addition-1,4, resulting in a repeating unit in the chain of the copolymer (denoted respectively by a trans-butadiene unit). 1,4 and cis-1,4), which is in the form of 2 geometric isomers of respective formula: (trans-1 butadiene unit, 4) and

(cis- butadiene unit 1, 4)

The polymerization of 1,3-butadiene can also be carried out according to a 1,2-addition, resulting in a repeating unit in the chain of the copolymer (referred to as a 1,2-vinyl butadiene unit) which has the formula:

Thus, the polybutadiene generally comprises in its chain the 3 repeat units above, designated below generically by “units derived from butadiene”.

According to a preferred variant, the liquid polybutadiene (E) comprises in its main chain the 3 above units, the content of 1,2-vinyl butadiene units being greater than or equal to 60% by weight (based on the total weight of the 3 units constituting the chain), preferably greater than or equal to 70%, even more preferably greater than or equal to 80%.

Liquid polybutadiene of (E) are commercially available, such as the Ricon ^® 152 resin from Cray Valley. The number-average molecular mass Mn of the Ricon ^® 152 resin is 2900 g / mol, its viscosity

Brookfield measured at 45 ° C is 20 Pa.s, and its content of 1,2-vinyl butadiene units is about 80% by weight, based on the total weight of the 3 units constituting the chain.

According to a more preferred embodiment, the HMPSA composition according to the invention can comprise up to 17% by weight of liquid polybutadiene (E).

Stabilizers (F): A quantity of 0.1 to 5% of one or more stabilizers (F) (or anti-oxidant) is also preferably included in the HMPSA composition according to the invention. These compounds are introduced to protect the composition from degradation resulting from a reaction with oxygen which is liable to be formed by the action of heat, light or residual catalysts on certain raw materials such as tackifying resins. .

These compounds can include primary anti-oxidants which scavenge free radicals and are generally substituted phenols such as Irganox ^® 1010 from CIBA or SUMILIZER ^® GS from SUMITOMO. The primary antioxidants can be used alone or in combination with other antioxidants such as phosphites such as Irgafos ^® 168 also from CIBA, or alternatively with UV stabilizers such as amines.

An amount of (F) ranging from 0.5 to 2% is preferred, and even more

particularly ranging from 0.5 to 1.5% preferred.

Ingredient content of the composition:

According to a preferred variant, the HMPSA composition according to the invention comprises, and, more particularly preferably, consists essentially of:

- from 12 to 19% by weight of the block copolymer (A);

- from 50 to 65% by weight of the tackifying resin (s) (B); and

- from 14 to 23% by weight of the liquid plasticizer (C).

According to a more preferred variant, the HMPSA composition according to the invention comprises, and, even more particularly preferably, consists of

mainly from:

- from 15 to 19% by weight of the block copolymer (A);

- from 55 to 65% by weight of the tackifying resin (s) (B); and

- from 14 to 23% by weight of the liquid plasticizer (C).

The viscosity of the HMPSA composition, as measured by a Brookfield ^® R VT at 163 ° C, is between 0.5 and 20 Pa.s, preferably between 0.5 and 5 Pa.s. Such a viscosity is quite suitable for the nozzles used in industrial units of coaters for its coating on a support layer.

The HMPSA composition according to the invention is prepared by simple mixing of its components at a temperature between 130 and 200 ° C, until a homogeneous mixture; preferably the photoinitiator (D) is introduced last into the mixture.

The required mixing techniques are well known to those skilled in the art.

Self-adhesive item:

A subject of the present invention is also a self-adhesive article comprising a support layer (b) coated with a self-adhesive layer (a), characterized in that said self-adhesive layer (a) consists of the adhesive composition according to the invention, in the crosslinked state.

For the purposes of the present invention, the term "self-adhesive article" includes any article which can be adhered to a surface (or substrate) only by the action of pressure with the hand or with equipment, without the use of glues or adhesives

additional. Thus, the self-adhesive article is also referred to as the "pressure sensitive self-adhesive article".

The backing layer (b) coated with a self-adhesive layer (a) is also referred to by the terms "self-adhesive backing". Said self-adhesive backing possesses the desirable adhesive power and tack. In addition, the adhesive joint formed after application of said self-adhesive support to a substrate ensures the attachment of the support layer (b) in a temperature range of up to 200 ° C. and sometimes beyond.

The purpose of these self-adhesive articles is in particular to be applied to a surface to be glued in order to bring together, hold, fix, or simply immobilize, expose shapes, logos, images or information. These articles can be used in many fields, such as the medical field, clothing, packaging, automotive (for example for the installation of logos, lettering, interior soundproofing, interior trim, gluing in the passenger compartment) or construction (eg for sound and heat insulation, window assembly). They can be shaped according to their final application, for example in the form of tapes, such as tapes for industrial use, DIY tapes or for fixing use on construction sites, single or double sided tapes, or in the form of tapes. in the form of labels, bandages, dressings, patches or graphic films.

According to one embodiment, the self-adhesive article is a self-adhesive multilayer system, and in particular a self-adhesive tape, which may be single-sided or double-sided, or else a label. The material that can be used for the support layer (b) can for example be any type of rigid or flexible support. Mention may for example be made of supports such as foams, felts, non-woven supports, plastics, membranes, papers or a film of a polymer material with one or more layers, in particular a non-stick protective paper or plastic film.

The support layer is made of a material, for example chosen from polyolefins, such as polyethylene, including high density polyethylene, low density polyethylene, linear low density polyethylene and ultra low linear density polyethylene, polypropylene and polybutylenes; polystyrene; natural or synthetic rubber; vinyl copolymers, such as polyvinyl chloride, plasticized or unplasticized, and poly (vinyl acetate); olefinic copolymers, such as ethylene / methacrylate copolymers, ethylene / vinyl acetate copolymers, acrylonitrile / butadiene / styrene copolymers, and ethylene / propylene copolymers; acrylic polymers and copolymers; polyurethanes; polyethers; polyesters; and mixtures thereof. Preferably, the support layer is based on acrylic polymers, polyethylene (PE), oriented, unoriented or bi-oriented polypropylene (PP), polyimide, polyurethane, polyester such as polyethylene terephthalate (PET), or paper.

According to a preferred embodiment, the self-adhesive article further comprises a protective non-stick layer (c) ("release liner"), adjacent to the adhesive layer (a). The protective release layer (c) can be easily removed without modifying the adhesive layer (a) which remains attached to the backing layer (b).

According to a preferred variant, said layer (c) comprises a silicone-based material, said material being either constituting said layer (c), or present in the form of a surface coating of said layer (c), said coating being intended to be in contact with the adhesive layer (a).

According to a preferred variant of the self-adhesive article according to the invention, said article is packaged in the form of a winding around a coil (or roll), the dimensions of which can vary over a wide range. Thus, the diameter of such a roll can range from 0.25 to 1 m, and its width from 0.25 to 2 m.

According to this last preferred variant, the protective non-stick layer (c) consists of the support layer (b) included in the self-adhesive article, in which the face which is opposite to the face in contact with the adhesive layer (a) is coated with silicone material. Such a multilayer system in which the protective non-stick layer (c) is not distinct from the layer (b) is sometimes referred to by the English designation of "linerless". Said packaging is particularly advantageous, because of its simplicity and the resulting economy, for

processors who convert these roll stocks into self-adhesive tapes.

According to one embodiment, the self-adhesive article obtained from the adhesive composition according to the invention comprises a permanent support layer (b) coated with an adhesive layer (a).

According to a preferred variant of the latter embodiment, the permanent support layer (b) is coated on its two faces with an adhesive composition, which may be identical or different, at least one of the two adhesive compositions being according to the invention, advantageously leading to the manufacture of so-called double-sided tapes

According to yet another embodiment, the self-adhesive article obtained from the adhesive composition according to the invention comprises a non-permanent support layer (b), which consists of a first plastic film or non-stick protective paper ( identical to layer (c) defined above), said layer (b) being coated with an adhesive layer (a), itself possibly also being coated with a second plastic film or non-stick protective paper, also identical to the layer (c) defined above. This embodiment is particularly suitable for the assembly by gluing of windows, more particularly for the assembly of the rigid panel consisting of double or triple glazing with the window frame. According to this embodiment, said non-permanent support layer (b) is intended to be removed by the user when the self-adhesive article is used with a view to assembling the window.

The self-adhesive article according to the invention can bond two substrates. The substrate to which the self-adhesive article is intended to be applied (referred to as "bonding substrate") can be flexible or rigid. In particular, it can have the same flexibility properties as the support layer (b) described above, so as to be wound up and packaged in the form of a coil, for example as described above.

Alternatively, the substrate to be bonded can be rigid. In this case, the substrate cannot be wound up and packaged in the form of a coil, for example as described above. The substrate to be bonded can for example be chosen from among concrete, paper, polyolefin type substrates, glass, ceramic and metals, in particular aluminum. The self-adhesive layer (a) consists of the adhesive composition according to the invention in the crosslinked state, and covers the support layer (b), in the self-adhesive article according to the invention. This layer (a) can have a very variable thickness, ranging from 5 μm to 2000 μm, preferably from 10 μm to 1000 μm.

A thickness within a wide range of 50 to 1000 μm is in particular preferred for self-adhesive tapes, while a thickness ranging from 10 μm to 100 μm, preferably 10 to 50 μm, is more particularly suitable in the case of self-adhesive labels.

The support layer (b) for its part has a thickness ranging from 10 microns to 50 mm, more preferably ranging from 10 microns to 20 mm, preferably ranging from 20 microns to 10 mm, more preferably ranging from 20 microns to 1. mm.

Manufacturing process of the self-adhesive article:

A subject of the present invention is also a method for manufacturing the self-adhesive article as defined above, said method being characterized in that it comprises the sequential steps:

- (i) preheating the HMPSA composition according to the invention, at a temperature between 70 and 180 ° C, preferably between 110 and 140 ° C;

- (ii) application of said composition by coating on a load-bearing surface;

- (iii) crosslinking of said composition by UV irradiation to form the layer (a) of crosslinked adhesive composition; then

- (iv) against bonding or transfer of the layer (a) on a support layer or on a non-stick protective film.

Steps (i), (ii), (iii) and (iv) are implemented sequentially in the method according to the invention, however it is not excluded either that steps (iii) and (iv) are inverted.

For the purposes of the present invention, the term “carrier surface” should be understood to mean either a conveyor belt covered with a non-stick layer, or a non-stick protective film (c) (“release liner” in English), or a layer support (b).

In the case where the carrier surface is a non-stick protective film (c), the method of manufacturing the self-adhesive article according to the invention can comprise the step (iv) of transferring the crosslinked adhesive layer (a ) on a support layer (b). In the case where the carrier surface is a support layer (b) or a non-stick protective film (c), the method of manufacturing the self-adhesive article according to the invention can further comprise step (iv) of against gluing of the adhesive layer on a non-stick protective film.

According to a preferred variant of the invention, step (iv) of the above-described method consists of a transfer of the crosslinked adhesive layer onto a flexible support layer (which may be a plastic film) after cooling the crosslinked adhesive layer to a temperature below the degradation or softening temperature of the material making up the support layer.

According to one embodiment, the method of manufacturing the self-adhesive article according to the invention further comprises a step (v) of coating a second layer of adhesive composition according to the invention on the support layer followed by a step (vi) of crosslinking the adhesive composition coated in step (v) by UV irradiation. According to this embodiment, a double-sided self-adhesive article is obtained.

Step (ii) of coating can be carried out by means of known coating devices, such as for example a lip or curtain-type nozzle, or else by roller. It uses a weight of HMPSA composition according to the invention ranging from 5 g / m ² to 2000 g / m ² , preferably from 10 g / m ² to 1000 g / m ² .

The basis weight of adhesive composition necessary for the manufacture of self-adhesive labels can range from 10 to 100 g / m ² , preferably from 10 to 50 g / m ² . That necessary for the manufacture of self-adhesive tapes can preferably vary within a range ranging from 50 to 1000 g / m ² , per face.

Stage (iii) of UV irradiation has the effect of creating - via in particular the vinyl-1,2 group during polymer chains of the block copolymer (A) - of carbon-carbon single bonds, which lead to the formation of 'a three-dimensional polymeric network in the adhesive layer (a).

This UV irradiation step is carried out by exposing, in the presence of air, the carrier surface coated with the HMPSA composition according to the invention, to a UV source which may be an arc or microwave UV lamp, doped or no, or a UV LED. The UV source is suitable for emitting radiation with a wavelength ranging from 200 nm to 500 nm. The dose of radiation required to crosslink the composition depends on various factors, such as the potency of the source, the amount (or basis weight) of composition coated, and the nature and amount of the photoinitiator. The time required for the crosslinking of step (iii) can vary within wide limits, depending on the power of the source and the basis weight of the coated composition, for example from less than 100 milliseconds to 10 minutes.

These various parameters are adjusted without difficulty by those skilled in the art.

The present invention finally relates to a bonding method using the self-adhesive article as defined above, characterized in that it comprises the following steps:

A) removal of the non-stick protective layer, when such a layer is present;

B) applying the self-adhesive article to a surface of a product; and

C) applying pressure to said article.

In step B), the self-adhesive article is applied so that the self-adhesive part of the article (formed by the self-adhesive layer) faces the surface of the product.

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

The following examples are given purely by way of illustration of the invention and should not be interpreted in such a way as to limit its scope.

Example 1:

1. Preparation of an HMPSA composition crosslinkable under irradiation:

The composition appearing in the following Table 1 is prepared by simple hot mixing at 165 ° C. of the indicated ingredients, the photoinitiator (D) being added last. The Brookfield viscosity of this composition was measured at a temperature of 163 ° C. The result is shown in Table 2 in mPa.s. 2. Preparation of a self-adhesive multilayer system comprising a PET support layer (b) coated with a layer (a) made up of the crosslinked HMPSA composition and with a thickness of 60 μm:

A laboratory coater operating continuously at a line speed of about 15 m / minute is used, said coater being available from ACUMETER Laboratory Inc. This coater is in particular equipped with a lip coating nozzle and a melter tank.

The support layer (b) is a 50 µm thick PET film in the form of a 10 cm wide strip packaged in a reel.

The non-stick protective film (c) used is a silicone paper (obtained from the company LAUFENBERG), in the form of a 10 cm wide strip packaged on a reel.

The HMPSA composition obtained above in 1. is heated in the melting tank to a temperature of 120 ° C. It is then coated at a basis weight of 60 g / m ² on the protective film (c), so as to form a layer 60 μm thick and 6 cm wide, centered on the corresponding strip of said film ( vs). Finally, the coated non-stick protective film thus obtained is laminated to the PET film.

Rectangular sheets measuring 10 cm x 20 cm are then cut from the three-layer film thus obtained, with a view to being exposed to a UV source. The UV lamp used is a UV mercury lamp of the Delolux 03S type with a power of 400 W which is placed approximately 20 cm from the three-layer sheets.

UV irradiation is carried out by placing the three-layer sheets at a distance of approximately 20 cm from the lamp (PET layer facing the lamp) and exposing them for a period of 5 to 30 seconds.

The self-adhesive article (or multilayer system) thus obtained is subjected to the tests described below.

180 ° peel test on stainless steel plate:

The adhesive power is evaluated by the peel test at 180 ° C on a stainless steel plate as described in the FIN AT method n ° 1, published in the FIN AT Technical Manual 6th edition, 2001. FIN AT is the international federation of manufacturers and converters of self-adhesive labels. The principle of this test is as follows. A test piece in the form of a rectangular strip (25 mm x 175 mm) is cut from the self-adhesive multilayer system prepared in point 2. This test piece is fixed over half of its length (after removing the portion of the corresponding protective non-stick layer ), on a substrate made of a stainless steel plate. The assembly obtained is left for 20 minutes at room temperature. It is then placed in a traction device capable, from the free end of the rectangular strip, of peeling or unsticking the strip at an angle of 180 ° and with a separation speed of 300 mm per minute. The apparatus measures the force required to take off the tape under these conditions.

The corresponding result is expressed in N / 2.54 cm and shown in Table 2.

Instant adhesion test (also called loop test):

The immediate tackiness or tack is evaluated by the instantaneous adhesion test known as the loop, described in the FINAT method no. 9, the principle of which is as follows.

A test piece in the form of a rectangular strip (25 mm x 175 mm) is cut from the self-adhesive multilayer system prepared in point 2. After removing all of the protective non-stick layer, the 2 ends of this strip are joined together. so as to form a loop with the adhesive layer facing outward. The 2 joined ends are placed in the movable jaw of a traction device capable of imposing a displacement speed of 300 mm / minute along a vertical axis with the possibility of going and returning. The lower part of the loop placed in a vertical position is first contacted with a horizontal stainless steel plate 25 mm by 30 mm over a square area of approximately 25 mm square. From this contact, the direction of movement of the jaw is reversed. The immediate tackiness is the maximum value of the force necessary for the curl to completely come off the plate.

The corresponding result is expressed in N / (2.54 cm) ² and is shown in Table 2.

Temperature causing the adhesive joint to rupture in static shear:

The maintenance at high temperature of the adhesive power of the self-adhesive multilayer system prepared in point 2 is evaluated by a test which determines the temperature causing the rupture of the adhesive joint in static shear. This test is also known by its English name of Shear Adhesion Failure Temperature (SAFT). Reference is made for this test to the FIN AT n ° 8 method. The principle is as follows.

A test piece in the form of a rectangular strip (25 mm x 75 mm) is cut from the self-adhesive multilayer system prepared in point 2. After removing all of the protective non-stick layer, a square portion of 25 mm side located at the end of the adhesive strip is attached to a stainless steel plate.

The test plate thus obtained is introduced, by means of a suitable support, in a substantially vertical position in an oven at a temperature of 20 ° C, the unglued part of the strip of length 50 mm being located below the plaque. After thermal equilibration, the part which has remained free of the strip is connected to a mass of 500 g, the whole of the device still remaining during the duration of the test maintained in said oven.

Under the effect of this mass, the adhesive joint which secures the strip to the plate is subjected to a shear stress. To better control this stress, the test plate is in fact placed so as to make an angle of 2 ° with respect to the vertical.

This oven is subjected to a programmed temperature rise at a rate of 0.4 ° C per minute up to a maximum temperature of 200 ° C.

The temperature, reported in Table 2, at which the strip detaches from the plate following the rupture of the adhesive joint under the effect of this stress is noted.

No rupture of the adhesive seal is observed up to 200 ° C, which is the maximum temperature allowed by the temperature rise programming of the oven, so that the result obtained is reported in table 2 under the caption : "> 200 ° C"

Examples 2 to 8:

Example 1 is repeated with the compositions indicated in Table 1.

The results of the tests concerning the self-adhesive multilayer systems obtained are also shown in Table 2. Table 1

Table 2

Claims

1. Hot-melt self-adhesive composition (HMPSA) crosslinkable under UV irradiation, comprising, on the basis of the total weight of said composition:

- from 10 to 24% by weight of a block copolymer (A) which comprises at least:

- of an appropriate content of a photoinitiator (D).

2. HMPSA composition according to claim 1, characterized in that the block copolymer (A) comprises 2 styrenic blocks Al and the content by weight of the vinyl-1,2 unit in the polybutadiene A2 block is within a range of from 30 at 70% by weight.

3. HMPSA composition according to one of claims 1 or 2, characterized in that the tackifying resin (B) has a softening temperature of between 90 and 120 ° C.

4. HMPSA composition according to one of claims 1 to 3, characterized in that the liquid plasticizer (C) consists of an oil whose average molecular mass, measured according to the ASTM D 2502 method, is less than or equal to 2000 g / mole.

5. HMPSA composition according to one of claims 1 to 4, characterized in that it can further comprise up to 25% by weight of a liquid polybutadiene (E) of low molecular mass.

6. HMPSA composition according to one of claims 1 to 5, characterized in that it comprises:

- from 12 to 19% by weight of the block copolymer (A);

- from 50 to 65% by weight of the tackifying resin (s) (B); and

- from 14 to 23% by weight of the liquid plasticizer (C).

7. Self-adhesive article comprising a support layer (b) coated with a self-adhesive layer (a), characterized in that said self-adhesive layer (a) consists of the adhesive composition, as defined in one of claims 1 to 6, in the crosslinked state.

8. Self-adhesive article according to claim 7, characterized in that it is a self-adhesive tape which may be single or double sided.

9. Self-adhesive article according to one of claims 7 or 8, characterized in that it further comprises a protective non-stick layer (c), adjacent to the adhesive layer (a).

10. Self-adhesive article according to one of claims 7 to 9, characterized in that the thickness of the layer (a) ranges from 5 µm to 2000 µm, preferably from 10 µm to 1000 µm.

11. A method of manufacturing the self-adhesive article as defined in one of claims 7 to 10, said method being characterized in that it comprises the sequential steps:

- (i) preheating the HMPSA composition to a temperature between 70 and 180 ° C;

- (ii) application of said composition by coating on a load-bearing surface;

- (iii) crosslinking of said composition by UV irradiation to form the layer of crosslinked adhesive composition (a); then - (iv) against bonding or transfer of the layer (a) on a support layer or on a non-stick protective film.

12. Bonding method implementing the self-adhesive article as defined in one of claims 7 to 10, characterized in that it comprises the following steps:

A) removal of the non-stick protective layer, when such a layer is present;

B) applying the self-adhesive article to a surface of a product; and

C) applying pressure to said article.