EP3585855A1

EP3585855A1 - Adhesive film activatable at low temperature

Info

Publication number: EP3585855A1
Application number: EP18710105.0A
Authority: EP
Inventors: Guillaume Michaud; Aurélien WIEGAND
Original assignee: Bostik SA
Current assignee: Bostik SA
Priority date: 2017-02-23
Filing date: 2018-02-22
Publication date: 2020-01-01
Also published as: FR3063080A1; FR3063080B1; CN110300786B; CN110300786A; US20200024495A1; WO2018154246A1; US11279860B2

Abstract

The invention relates to an adhesive composition that can be activated at a low temperature (from 110°C, preferably from 100°C) and is available in the form of a film, and to the method for the production thereof. The invention also relates to a composition comprising at least one specific polyester polyol and at least one specific polyisocyanate dispersible in said polyester polyol in the presence of at least one specific organic solvent, and to the use of said composition for producing an adhesive composition that can be activated at a low temperature and is available in the form of a film.

Description

Low temperature activatable adhesive film

FIELD OF THE INVENTION

The present invention relates to an adhesive composition which can be activated at low temperature (from 110 ° C., preferably from 100 ° C.), available in film form, and its preparation process.

The present invention also relates to a composition comprising at least one particular polyester polyol and at least one particular polyisocyanate dispersed in said polyester polyol in the presence of at least one particular organic solvent, as well as the use of said composition for the manufacture of a adhesive composition activatable at low temperature (from 110 ° C, preferably from 100 ° C), available in film form.

BACKGROUND

The use of heat-activatable adhesive compositions has many applications in various fields of the industry. In particular, these compositions can be used in the form of films (also referred to as heat-activatable adhesive films) for bonding substrates.

By "heat activatable" (or "thermally activatable") it is meant that the composition (optionally in the form of a film) has latent adhesive properties which are activated only after heating said composition (or said film) beyond beyond a given temperature (called "activation temperature"). It is during this thermal activation step that the composition (or the film) will develop its adhesive properties.

The use of such compositions has many advantages. In particular, the adhesion of the substrate (s) may be delayed at the desired moment and implemented easily by simple heating or thermal activation.

In addition, the use of adhesive films is an interesting alternative when the operator does not have facilities or dedicated means for coating the adhesive composition. Adhesive films are also simple and quick to implement, compared with solvent-based adhesive compositions, for example, the implementation of which requires evaporating the solvent.

In principle, during the gluing process, the adhesive film is placed between the surfaces of the substrates to be assembled and held in contact while the assembly is heated to a high temperature to melt and thermally activate said film. Generally, the assembly is heated for a relatively short time to prevent thermal degradation of substrates. This time may vary depending on the thickness of the film. After cooling, an adhesive seal is obtained assuring the assembly of the substrates.

There are currently on the market adhesive compositions based on polyol (s) and blocked isocyanate (s) available in the form of films and having interesting adhesive properties, but having a very high activation temperature.

"Blocked isocyanate" means a compound having at least one NCO function, said NCO function (s) having been blocked with a blocking agent or protective agent, to prevent it (s) react (s) with other entity (s) present (s) within the same composition, including the OH functions of the polyol (s) present (s) in the same composition. When the blocked isocyanate is heated at high temperature, the NCO function (s) of said isocyanate will be liberated and reacted with the polyol (s) present to form a polyurethane, having adhesive properties.

The heat-activatable adhesive films derived from such compositions based on polyol (s) and blocked isocyanate (s) make it possible to satisfactorily bond a large number of substrates, but still have to be improved on a certain number of points. , especially with regard to their activation temperature.

Indeed, it has been observed that these films must be heated at high temperatures (above 160 ° C), in order to be activated and fully develop their adhesive properties. Otherwise, the adhesive performance of these films will be weak or insufficient to ensure the bonding assembly of two substrates.

Moreover, the requirement of strongly heating the adhesive film to activate it is incompatible with the use of certain types of substrates liable to degrade thermally beyond the activation temperature of said film. By way of example, mention may be made of polyolefin-type substrates, such as polypropylene, which degrades if it is heated above 160 ° C.

The purpose of the present application is now to develop new heat activatable adhesive compositions, available in the form of films, which can be activated at an activation temperature lower than that of the compositions constituting the above-mentioned adhesive films of the market. and having excellent adhesion properties on various substrates (metallic or non-metallic).

Surprisingly, it has been discovered that it is possible to obtain, by a simple preparation process, a heat-activatable adhesive composition, usable in film form, and having the above-described properties, from a composition comprising at least one particular polyester polyol, at least one particular polyisocyanate, and at least one particular organic solvent, as defined below.

In particular, the composition according to the invention makes it possible to manufacture ready-to-use adhesive films which can be activated rapidly at low temperature and which have excellent mechanical and adhesive properties. The adhesive film according to the invention is especially heat-activatable at temperatures below 150 ° C, especially from 110 ° C, preferably from 100 ° C.

Moreover, it has been observed that the composition according to the invention makes it possible to obtain an adhesive film having, for the same type of substrate, improved adhesive properties, especially in terms of shear strength, compared to films existing on the market.

In addition, it has been observed that the adhesive seal formed after thermal activation from the adhesive film according to the invention makes it possible to durably assemble two substrates, while maintaining a level of cohesion sufficient to ensure the bonding of the two substrates, even after having been exposed to heat (up to 40 ° C).

In some applications, it is also desirable that the adhesive films are furthermore flexible enough to be rollable and packaged in the form of coils or rolls of suitable dimensions.

In particular, it has been observed that the composition according to the invention has good film-forming properties and makes it possible to obtain a flexible film of homogeneous appearance that is easy to handle and to store.

SUMMARY OF THE INVENTION:

Thus, a first subject of the invention relates to a composition comprising:

at least one saturated polyester polyol (A), of which at least one saturated polyester polyol having a number-average molecular weight (denoted MnI) greater than or equal to 15,000 g / mol, preferably greater than or equal to 18,000 g / mol more preferably greater than or equal to 21,000 g / mol, more preferably still ranging from 21,000 to 75,000 g / mol, and more preferably ranging from 21,000 to 60,000 g / mol (denoted Al), and

at least one uretdione-type polyisocyanate (B) having at least two NCO groups.

The composition according to the invention may also comprise at least one organic solvent (C) capable of solubilizing the polyester polyol (s) (Al) without solubilizing the polyisocyanate (s) (B). According to one embodiment, the present invention relates to a composition comprising:

at least one uretdione-type polyisocyanate (B) having at least two groups

NCO;

- optionally at least one organic solvent (C) capable of solubilizing the (s) polyester polyol (s) (A) without solubilizing the (s) polyisocyanate (s) (B).

A second subject of the invention relates to the use of the composition according to the invention for producing a heat activatable adhesive composition, especially in the form of a monolayer or multilayer film.

In particular, the invention relates to a method for preparing a heat-activatable adhesive composition, especially in the form of a monolayer or multilayer film.

A third subject of the invention relates to a heat-activatable adhesive composition, especially in the form of a monolayer or multilayer film, obtainable from the composition according to the invention.

Other objects and features or advantages of the present invention will become more apparent upon reading the description and examples.

In this application, in the absence of any indication to the contrary:

the amounts expressed as a percentage correspond to weight / weight percentages;

the hydroxyl number is expressed in milligram of potash per gram of product (mg KOH / g);

the glass transition temperature (Tg) can be measured in a well-known manner, for example according to ASTM standard El 356-08;

the softening temperature (sp) can be measured in a well-known manner, for example according to the ASTM E28-99 standard;

- The melting temperature (mp) can be measured in a well known manner for example using standard differential scanning calorimetry techniques (often referred to as DSC for Differential Scanning Calorimetry). DETAILED DESCRIPTION OF THE INVENTION

According to a first subject, the invention relates to a composition comprising:

at least one saturated polyester polyol (A), of which at least one saturated polyester polyol having a number-average molecular weight (denoted MnI) greater than or equal to 15,000 g / mol, preferably greater than or equal to 18,000 g / mol more preferably greater than or equal to 21,000 g / mol, more preferably from 21,000 to 75,000 g / mol, and more preferably ranging from 21,000 to 60,000 g / mol (Al), and

at least one uretdione-type polyisocyanate (B) having at least two groups

NCO.

The number average molecular weight of the polyester polyol (s) is calculated in a well known manner with respect to the hydroxyl numbers and the functionality of the (each) polyester polyol (s).

Preferably, the composition according to the invention comprises:

from 75 to 95% by dry weight of at least one saturated polyester polyol (A), of which at least one saturated polyester polyol (Al) as defined above, and

from 5 to 25% by dry weight of at least one uretdione-type polyisocyanate (B) having at least two NCO groups,

said contents being expressed relative to the total dry weight of the composition according to the invention.

The saturated polyester polyol (s) (A) that can be used according to the invention can be obtained by polycondensation:

at least one polyester diol, such as ethylene glycol, diethylene glycol, trimethylene glycol, butane diol (1,4-butanediol; 1,2-butanediol; 1,3-butanediol), neopentyl glycol, 2- methyl 1-1, 3-propane diol, hexane diol (hexamethylene glycol), propane diol (propane-1,2-diol, propane-1,3-diol or propylene glycol), trimethylolpropane, cyclohexanedimethanol, or mixtures thereof, and

at least one dicarboxylic acid or one of its ester or anhydride derivatives, such as terephthalic acid, dimethyl terephthalate, isophthalic acid, adipic acid, azelaic acid, sebacic acid, cyclohexane dicarboxylic acid, dodecanoic acid (1,10-decanedicarboxylic acid), succinic acid, phthalic anhydride, maleic anhydride and hydroxycarboxylic acids such as diesters obtained from polycaprolactone or epsilon-caprolactone and diethylene glycol (named CAP A), or mixtures thereof. The saturated polyester polyol (s) (A) usable according to the invention is (are) preferably linear or branched and preferably amorphous or semi-crystalline. (s).

The saturated polyester polyol (s) (A) usable according to the invention preferably has a glass transition temperature (Tg) ranging from -40 to 70 ° C., preferably measured. according to ASTM E1356-08.

The saturated polyester polyol (s) (A) which may be used according to the invention preferably have a melting temperature (mp) and / or a softening temperature (sp) of less than or equal to 160 ° C, preferably less than or equal to 130 ° C, more preferably less than or equal to 100 ° C.

The saturated polyester polyol (s) (A) that may be used according to the invention may consist solely of saturated polyester polyol (s) (Al) as defined above, or a mixture of saturated polyester polyols including at least one saturated polyester polyol (Al) as defined above and at least one saturated polyester polyol (A2) other than (Al).

Preferably, the saturated polyester polyol (s) (Al) is (are) semi-crystalline (s) and more preferably has a Tg of less than or equal to 0 ° C., preferably Tg. being measured according to ASTM E1356-08.

Preferably, the (dry) mixture of saturated polyester polyols (A) comprises:

at least one saturated polyester polyol (Al) as defined above, and

at least one saturated polyester polyol (A2) having a hydroxyl number greater than or equal to 15 mg KOH / g, preferably ranging from 20 to 90 mg KOH / g, more preferably from

30 to 60 mg KOH / g.

According to one embodiment, the composition according to the invention comprises:

at least one saturated polyester polyol (Al) as defined above, preferably a saturated polyester polyol (Al) semi-crystalline or a mixture of two saturated polyester polyols (Al) amorphous, and

at least one saturated polyester polyol (A2), having a hydroxyl number greater than or equal to 15 mg KOH / g, preferably ranging from 20 to 90 mg KOH / g, more preferably from 30 to 60 mg KOH / g, said said polyester polyol (s) (A2) being preferably amorphous.

Preferably, the mass ratio of the amount of polyester polyol (s) (Al) to the amount of polyester polyol (s) (A2) present in the mixture of saturated polyester polyols (A) ranges from 0.1 to 1, of preferably from 0.2 to 1, and more preferably from 0.25 to 0.7.

Preferably, the saturated polyester polyol mixture (A) comprises:

at least one semi-crystalline saturated polyester polyol (Al), preferably, as defined above, and at least one amorphous saturated polyester polyol (A2), preferably as defined above.

In the context of the invention, the term "amorphous polyester polyol" means a polyester polyol having no crystalline form. It preferably has a mass crystallinity level of less than 10%, preferably less than 5%, advantageously less than 2%, and even more preferably less than 1%.

In the context of the invention, the term "semi-crystalline polyester polyol" means a polyester polyol comprising crystalline zones and amorphous zones in its structure. It preferably has a mass crystallinity level of at least 20%, preferably at least 30%, preferably at least 40%, and less than 90%, preferably less than 80%.

The degree of crystallinity, designating the. proportion of material in the crystalline state, can be determined by X-ray diffraction analysis at different angles of incidence, by calorimetric measurements such as its DSC (Differential Scanning Calorimetry) or by any other technique for estimating the proportion crystalline phase of the semicrystalline polyester polyol.

Preferably, the mixture (dry) of saturated polyester polyols (A) preferably has an average IOH ranging from 2 to 65 mg KOH / g, more preferably ranging from 4 to 60 mg KOH / g, even more preferably from 6 to 55 mg KOH / g, in particular from 10 to 50 mg KOH / g, and more preferably ranging from 15 to 45 mg KOH / g.

The polyester polyol (s) (A) usable (s) according to the invention is (are) available (s) commercially. Preferably, polyester polyols of the VITEL® series marketed by Bostik, as illustrated in the examples of the present application, are used.

The uretdione polyisocyanate (s) (s) usable according to the invention is (are) preferably solid at room temperature (20 ° C.) and is present in the form of particles whose maximum particle size is less than 40μιη.

According to one embodiment, the uretdione-type polyisocyanate (s) which can be used according to the invention is (are) solid at ambient temperature (20 ° C.).

According to one embodiment, the uretdione-type polyisocyanate (s) that can be used according to the invention has (a) a melting temperature greater than or equal to 50 ° C., preferably greater than or equal to 100. ° C, preferably greater than or equal to 130 ° C, preferably greater than or equal to 140 ° C, and still more preferably greater than or equal to 250 ° C. According to one embodiment, the uretdione-type polyisocyanate (s) which can be used according to the invention is in the form of particles.

Preferably, the polyisocyanate (s) uretdione type (B) used (s) according to the invention has (nt) a particle size distribution in volume ranging from 0.1 to 40μιη.

Preferably, the polyisocyanate (s) uretdione type (B) used (s) according to the invention has (s) a mean size (D50) ranging from 1 to 15 μιη.

The polyisocyanate (s) of the uretdione type (B) that can be used according to the invention preferably have a (D50) less than or equal to 15 μιη, preferably ranging from 0.1 to 15 μιη, and advantageously ranging from 1 to 15 μιη.

D50 is the median particle diameter corresponding to 50% (by volume) of the cumulative particle distribution, i.e., by volume, 50% of the particles have a diameter less than D50 and 50% of the particles have a diameter greater than D50.

D50 and volume particle size distribution can be measured according to ISO 13320-2009 ("Particle size analysis - Laser diffraction methods").

Advantageously, the uretdione-type polyisocyanate (s) which can be used according to the invention corresponds to the following formula (I):

(I)

in which :

R is a divalent group comprising from 6 to 13 carbons and

n is an integer ranging from 0 to 10.

Preferably, R is a divalent aromatic or polyaromatic group, more preferably derived from an aromatic diisocyanate such as toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI).

Preferably, R is a divalent hydrocarbon group.

Advantageously, the uretdione-type polyisocyanate (s) which can be used according to the invention corresponds to one of the following formulas (1-1) or (1-2):

(1-1)

(1-2)

These polyisocyanates advantageously have a melting point higher than the activation temperature of the adhesive composition according to the invention.

More preferably, the uretdione-type polyisocyanate (s) which can be used according to the invention is (are) chosen from among the MDI uretdione dimers and the TDI uretdione dimers, and more preferably the uretdione dimers of MDI (n being in particular 1 in formula (I) above).

Preferably, the uretdione-type polyisocyanate (s) that can be used according to the invention has (s) an NCO content (denoted% NCO) ranging from 15 to 40% by weight, more preferably from 20 to 35% by weight, based on the weight of said polyisocyanate.

The polyisocyanate (s) (B) used (s) according to the invention is (are) commercially available. By way of example, mention may be made of the following products:

Addolink® TT (Uretdione from TDI) marketed by Rhein Chemie (% NCO = 24%),

Grilbond® A2bond (uretdione of MDI) marketed by the company EMS-Griltech (% NCO = 30.2%),

as illustrated in the examples of this application.

According to a preferred embodiment, the uretdione-type polyisocyanate (s) usable according to the invention does not comprise an isocyanurate group.

Preferably, the content of polyisocyanate (s) uretdione type (B) in the composition according to the invention is such that the molar ratio NCO / OH ranges from 0.5 to 1.5, preferably from 0.8 to 1 , 2, and more preferably is equal to about 1. This ratio corresponds to the molar ratio of the number of NCO functions to the number of OH functions in the composition. Functions NCO are provided by all the polyisocyanates present in the composition according to the invention and the OH functions are provided by all the polyester polyols present in the composition according to the invention.

The composition according to the invention may also comprise at least one organic solvent (C) capable of solubilizing the polyester polyol (s) (A) without solubilizing the polyisocyanate (s) of uretdione type (B), especially in the mixing conditions.

Thus, the organic solvent (s) (C) that may be used according to the invention are (are) preferably such that:

the polyester polyol (s) (A) is (are) soluble in the organic solvent C). By soluble in the organic solvent C) is meant that it (s) can (s) form a homogeneous composition consisting of up to 40% by weight of polyester polyol (s) in the organic solvent C), and preferably they can form a solution of up to 60% by weight of polyester in the organic solvent C),

the polyisocyanate (s) of uretdione type (B) is (are) insoluble in the organic solvent (s) (C), and in particular in a composition comprising the ) said (s) organic solvent (s) (C) and the (s) said (s) polyester polyol (s) (A).

The organic solvent (s) (C) used (s) according to the invention is (are) typically inert (s) vis-à-vis the ingredients included in the composition according to the invention.

The composition according to the invention may comprise from 0 to 60% by weight, preferably from 1 ppm to 50% by weight (ie from 10% to ⁴ % by weight to 50% by weight) and more preferably from 1 ppm to 40%> by weight, of the total weight of said composition of at least one organic solvent (C) as defined in the present application.

Preferably, the composition according to the invention comprises at least 35% by weight of organic solvent (s) (C), and more preferably from 40 to 60% by weight of organic solvent (s) (C). ), relative to the total weight of the composition according to the invention, for solubilizing the polyester polyol (s) (A) and dispersing the polyisocyanate (s) B) in said solvent mixture.

According to one embodiment, the composition according to the invention comprises more than 1 ppm of the above-mentioned organic solvent (s) (C), preferably more than 10 ppm by weight, preferably more than 100 ppm by weight. more preferably more than 1000 ppm by weight, and more preferably more than 10 000 ppm by weight of organic solvent (s) (C) relative to the total weight of said composition.

Preferably, the composition according to the invention comprises more than 30% by weight of the above-mentioned organic solvent (s) (C), preferably more than 35% by weight, preferably more than 40% by weight, and advantageously more than 45% by weight of organic solvent (s) (C), relative to the total weight of said composition.

Preferably, the organic solvent or mixture of organic solvents (C) has a delta solubility parameter (δ) (also called Hildebrand solubility parameter, HSP) ranging from 6.9 to 10.0 (cal / cm ³ ) ^{1 / 2} and a hydrogen bonding index (HBI) gamma (y) ranging from 5.0 to 7.7. These parameters are defined in a manner well known in the literature, such as, for example, in paragraphs 38 and 39 of application US 2004/0204524:

the delta solubility parameter is defined in Rompp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, "solubility parameters", p. 361 to 365;

hydrogen bonding index describes the ability of a solvent molecule to form hydrogen bonds. The donor solvents have a negative hydrogen bonding index and the acceptor solvents have a positive hydrogen bond number. The hydrogen bond index is determined according to the infra-red band deviation for the RO-H elongation band (RC Nelson, RW Hemwall and GD Edwards, Journal of Paint Technology, "Treatment of hydrogen bonding in predicting miscibility" 42, No. 550, 1970, pp. 636-64). Preferably, the organic solvent or organic solvent mixture (C) has a boiling point of less than or equal to 130 ° C, preferably less than or equal to 100 ° C, more preferably ranging from 50 to 90 ° C.

Preferably, the organic solvent or organic solvent mixture (C) has a saturation vapor pressure at 20 ° C. of greater than 0.5 kPa, preferably greater than 5 kPa.

Preferably, the organic solvent or organic solvent mixture (C) is chosen from ketone type solvents, ethers, and mixtures thereof.

Preferably, the organic solvent (C) is chosen from aliphatic ketones such as acetone, methyl ethyl ketone (MEK), 2-pentanone, 3-pentanone, methyl isobutyl ketone, and mixtures thereof. More preferably, the organic solvent (C) is methyl ethyl ketone.

In addition, the composition according to the invention may or may not comprise at least one optional ingredient chosen from polyols other than polyol polyols (A), in particular having a molar mass or a number-average molar mass of less than 5000 g / mol, stabilizers (anti-oxidant, anti-UV, thermal stabilizer), catalysts, dyes, pigments, antiblocking agents (silica, fatty acid amides, waxes, talc), and mixtures thereof, provided that the advantageous properties of the composition according to the invention are not modified.

According to a second object, the invention relates to the use of the composition according to the invention for producing a heat activatable adhesive composition.

In particular, the invention relates to a process for preparing a heat-activatable adhesive composition comprising the following steps:

El) preparing a composition according to the invention by dispersing the polyisocyanate (s) of the uretdione type (B) in a composition comprising at least one polyester polyol (s) (A) and at least one organic solvent (C) ), as defined above, E2) removal of the organic solvent (C).

In step E1), the polyester polyol (s) (A) is (are) solubilized in the organic solvent (s) (C), preferably while hot, by for example at a temperature of less than or equal to 160 ° C., preferably less than or equal to 130 ° C., more preferably less than or equal to 100 ° C., before introducing, into the composition obtained, the polyisocyanate (s) of urétdione type (B), with rapid stirring so as to obtain a dispersion. The temperature is for example greater than or equal to 50 ° C, preferably greater than or equal to 60 ° C, and preferably greater than or equal to 70 ° C.

The temperature of the solvent mixture can be lowered before introduction of the polyisocyanate (s) of urétdione type (B).

According to a preferred embodiment, the preparation method according to the invention comprises between step El) and E2) a step El bis) in which the dispersion obtained in step El) is formed into a film. For this, the dispersion is applied in a uniform layer on a non-stick surface, such as a silicone surface. The application can be made in particular using a filmmaker or filmstrip. At the end of steps El), Elbis) and E2), a heat-activatable adhesive composition in the form of a monolayer film is advantageously obtained.

According to a variant of this preferred embodiment, the steps Elbis) and E2) can be repeated, so as to obtain a heat-activatable adhesive composition in the form of a multilayer film.

According to one embodiment, the method for preparing a heat-activatable adhesive composition comprising the following steps:

i) solubilization of (s) polyester polyol (s) (A) as defined above in the above-mentioned organic solvent (s) (C), preferably in the hot state, for example at a temperature of less than or equal to 160 ° C, preferably lower or equal to 130 ° C, more preferably less than or equal to 100 ° C, said temperature being advantageously between 50 ° C and 160 ° C;

ii) possible lowering of the temperature of the solvent mixture, for example at a temperature ranging from 40 ° C. to 100 ° C., preferably from 40 ° C. to 80 ° C., and advantageously at a temperature ranging from 40 ° C. to 60 ° C. VS;

El) dispersion of the above-mentioned polyisocyanate (s) of the uretdione type (B) in a composition comprising at least one polyester polyol (s) (A) and at least one organic solvent (C), as defined above,

possible El bis) in which the dispersion obtained in step El) is formed into a film;

E2) removal of the organic solvent (C).

According to a third object, the invention relates to a heat-activatable adhesive composition, especially in the form of a monolayer or multilayer film, obtainable from the composition according to the invention.

The heat-activatable adhesive composition according to the invention comprises:

at least 75% by weight of at least one saturated polyester polyol (A) as defined above, of which at least one saturated polyester polyol (Al) as defined above,

from 5 to 25% by weight of at least one polyisocyanate of the uretdione type (B) having at least two NCO groups, as defined above, and

less than 0.5% by weight, preferably less than 0.1% by weight, preferably less than 0.01% by weight, and advantageously less than 0.001% by weight, of at least one organic solvent (C ), as defined above, with respect to the total weight of the adhesive composition according to the invention.

According to one embodiment, the heat-activatable adhesive composition comprises more than 1 ppm of at least one organic solvent (C) as defined above, preferably more than 10 ppm, and advantageously more than 100 ppm by weight per relative to the total weight of said adhesive composition according to the invention.

In the context of the invention, the term ppm, "part per million". It is ppm by weight.

The heat-activatable adhesive composition according to the invention may further comprise at least one optional ingredient as defined above.

The heat-activatable adhesive film according to the invention preferably has a total thickness ranging from 3μιη to 500μιη. In the case of a monolayer film, the thickness of the film is preferably from 3μηι to 120μηι. In the case of a multilayer film, the film thickness is preferably from 3μιη to 500μιη.

The heat-activatable adhesive films according to the invention are ready for use and can be rapidly cross-linked on a substrate or between several substrates, unlike solvent-based adhesive compositions which must be dried before crosslinking. It has been observed that for an adhesive film according to the invention of thickness ΙΟΟμιη, the crosslinking time is about 10 minutes at 100 ° C.

The following examples are given purely by way of illustration of the invention and can not be interpreted to limit its scope.

EXAMPLES

The following ingredients were used:

as polyester polyol (A.l):

-V7200: VITEL® 7200 sold by the company Bostik: semi-crystalline saturated polyester polyol having a glass transition temperature Tg equal to -40 ° C, and an IOH ranging from 3 to 5 mg KOH / g,

-V3550: VITEL® 3550B sold by the company Bostik: amorphous saturated polyester polyol having a glass transition temperature Tg equal to -11 ° C and a weight average molecular weight (M _w ) equal to 75,000 g / mol, and a IOH ranging from 3 to 6 mg KOH / g,

-V3330: Vitel® 3330B marketed by the Bostik Company: amorphous saturated polyester polyol having a glass transition temperature Tg equal to 16 ° C and a weight average molecular weight (M _w) equal to 70 000 g / mol, and an IOH ranging from 3 to 6 mg KOH / g,

-V2700: Vitel® 2700B marketed by the Bostik Company: amorphous saturated polyester polyol having a glass transition temperature Tg equal to 50 ° C and a weight average molecular weight (M _w) equal to 74 000 g / mol and an OH value ranging from 2 to 5 mg KOH / g,

-V2200: VITEL® 2200B sold by the company Bostik: amorphous saturated polyester polyol having a glass transition temperature Tg equal to 69 ° C and a weight average molecular weight (M _w ) equal to 47,500 g / mol and an IOH ranging from 3 to 5 mg KOH / g, as polyester polyol (A.2) or other polyol other than (A.

-V5833: VITEL ® 5833B sold by the company Bostik: polyester polyol having a glass transition temperature Tg equal to 48 ° C and a weight average molecular weight (M _w ) equal to 9,800 g / mol and an IOH ranging from 37 at 55 mg KOH / g, -PI: BAYCOLL® AD 5027 sold by the company Covestro (polyester polyol having an IOH ranging from 23 to 33 mg KOH / g),

-P2: DY ACOLL® 7360 sold by the company Evonik (polyester polyol having an IOH ranging from 27 to 34 mg KOH / g, and a melting point equal to 55 ° C.), -P3: DYNACOLL® 7320 sold by the company Evonik (polyester polyol having an IOH ranging from 27 to 34 mg KOH / g, and a glass transition temperature Tg = -

20 ° C),

-P4: Dynacoll® 7230 sold by the company Evonik (polyester polyol having an IOH ranging from 27 to 34 mg KOH / g, and a glass transition temperature Tg = -30 ° C.),

-P5: CAP A® 2054 sold by the company PERSTORP (polyester polyol having an IOH ranging from 200 to 215 mg KOH / g, and a melting temperature ranging from 18 to 23 ° C.),

-P6: DIEXTER® G235 sold by the company COIM (polyester polyol having an IOH ranging from 54 to 58 mg KOH / g),

-P7: DIANOL® 320 marketed by the company ARKEMA (polyether polyol:

diethoxylated bisphenol A having an OHI equal to about 325 mg KOH / g),

-P8: CARBOWAX® PEG 4000 marketed by DOW (polyether polyol: polyethylene glycol having an IOH ranging from 25 to 32 mg KOH / g),

-P9: Diethylene Glycol (DEG) (polyether polyol having an OHI equal to about 1057 mg KOH / g),

-P10: DESMOPHEN® Cl 100 sold by the company COVESTRO (polyester polyol having an IOH ranging from 198 to 238 mg KOH / g).

as polyisocyanate (B):

UR1: ADDOLINK® TT marketed by the company RHEIN CHEMIE (uretdione of TDI, having a melting point greater than 140 ° C., and a TDI monomer content of less than 0.1%),

UR2: GRILLBOND® A2bond marketed by the company EMS-GRILTECH (Uretdione de MDI having a melting point of approximately 260 ° C.), as an organic solvent (C) or a comparative organic solvent:

-MEC: Methyl Ethyl Ketone,

-DCM: Dichloromethane,

-AcOEt: Ethyl acetate.

Preparation of the solvent compositions according to the invention

The compositions of Examples 1 to 9 according to the invention are prepared from the ingredients described in Table 1 below, mixed with 40% by weight of an organic solvent SI relative to the weight of the mixture.

The contents indicated in Table 1 are expressed in grams (g) and, where appropriate, in percent by dry weight relative to the weight of the composition without solvent (% dry).

In the compositions of Examples 1-9, the weight ratio A.1 / A.2 varies from 0.25 to 0.67 approximately. Operating mode:

In a glass reactor of suitable capacity and equipped with a refrigerant, the polymers (polyester polyols and any other polyols) and the organic solvent are introduced into the mixture, then the whole is heated to 70 ° C. with slow stirring for about 10 hours until solubilization of the polymers.

When the polymers are solubilized, the solution is cooled to 55 ° C. The polyisocyanate is then introduced, then the mixture is transferred to a suitable container and stirred rapidly using a speed mixer for two times 1 minute at 2000 revolutions per minute (rpm).

Table 1: Compositions according to the invention

Preparation of the comparative solvent compositions:

The compositions of Comparative Examples CE1 and CE2 correspond to adhesive compositions in the form of films based on VITEL® and a compound B ') other than the compound B) used according to the invention (the compound B' is not a polyisocyanate uretdione type). These adhesive films are sold under the name FlO-316 and F10-300 by the company Bostik.

The compositions of Comparative Examples CE3 to CE12 were prepared in the same manner as the compositions of Examples 1 to 9 according to the invention, following the procedure described above. The polymers used are polyols PI to P8:

In particular, the compositions of Comparative Examples CE3 to CE10 each correspond to the composition of Example 1 according to the invention in which all of the polyester polyols A) was replaced in equal amounts by a polyol PI to P8 such that described above, chosen by polyester polyols and polyether polyols, the nature and content of the other ingredients being identical elsewhere.

In particular, the compositions of Comparative Examples CE 11 and CE 12 each correspond to the composition of Example 1 according to the invention in which the organic solvent SI has been replaced in equal amounts by an organic solvent S 2 or S 3 respectively, the nature and content of the other ingredients being identical elsewhere. Table 2: Comparative Compositions

Preparation of the films from the compositions prepared in Examples 1-9 and CE3 to CE11:

With the aid of a 500 μm filmograph, a film of the polyisocyanate dispersion is drawn on silicone paper into the solvent solution of polyester polyols. The film is left under suction for a minimum of one night to evaporate the organic solvent.

Evaluation of the quality of the films (maintenance and flexibility):

After evaporation of the solvent, the film as above-prepared is detached by hand from the silicone paper. Once detached, the flexibility of the film is tested by bringing the ends of the opposite edges of the film lengthwise so as to wind it into a cylinder.

It has been observed that the compositions of Examples 1-9 according to the invention have made it possible to obtain a self-supporting film which is sufficiently flexible to be in the form of a roll. In particular, it has been noted that the compositions of Examples 1 to 5 have a better mixing quality and were more film-forming, thus making it possible to obtain a thinner and more homogeneous film.

The commercial films of the examples CEI and CE2 also have satisfactory properties in terms of flexibility.

On the other hand, none of the compositions of Comparative Examples CE3 to CE 12 made it possible to obtain a flexible self-supporting film. Indeed, the compositions of Examples CE3 to CE10 were too friable to be detached from the silicone support. As for the examples IEC 1 and CE 12, the composition has frozen even before it can be cast as a film. Preparation of test specimens from the films:

A sample of the film 25 mm long and 12.5 mm wide is cut and placed between two rigid supports in staggered rows, of the same dimensions. Both supports can be wood or aluminum. The assembly is clamped with forceps and placed in an oven at 100 ° C for 10 minutes, during which the film will melt and crosslink. At the end of this thermal activation step, an adhesive seal is formed between the two supports.

Adhesive Seal Shear Strength Test (ISO Standard 4587):

The shear stress resulting in the rupture of the adhesive joint is measured.

The principle of this measurement is to solicit in a tensile machine, whose moving jaw moves at a constant speed, a standard-shaped test piece as prepared above, consisting of the adhesive composition crosslinked between 2 rigid supports made of aluminum, and to record the stress applied at the moment when the test piece breaks.

The maximum force measured at break is evaluated at different times and in different storage conditions, after thermal activation:

-initial: after the specimen has returned to room temperature after thermal activation, -1 week at 23 ° C: after storage of the specimen for 1 week at 23 ° C,

-1 week at 40 ° C: after storage of the specimen for 1 week at 40 ° C.

The results are expressed in megapascal (MPa) and recorded in Table 3 below. Each of the values below corresponds to an average value calculated for measurements made on 5 identical samples.

It is observed that the compositions of Examples 1 to 5 according to the invention make it possible to obtain an adhesive film having improved adhesive properties compared with adhesive films on the market. The adhesive performances observed (ex 1-5) are also maintained at a satisfactory level even after 1 week to 1 month storage at room temperature. The observed adhesive performance (ex2) is also maintained at a satisfactory level even after long exposure to heat (1 week at 40 ° C).

Table 3: Mega Pascals Shear Strength

In the same way, rigid wooden supports of the same size as previously were glued successfully using the specimens from the compositions of Examples 1 to 5 according to the invention.

Thus, in view of the foregoing, it has been observed that all of the compositions according to the invention make it possible to easily obtain an adhesive film having good adhesive properties on various substrates and having sufficient support and flexibility to be able to be handled and stored easily.

In particular, it has been observed that the compositions according to the invention make it possible to obtain an adhesive film having improved adhesive properties compared with adhesive films on the market, in particular on a metal substrate.

In particular, it has been observed that the compositions according to the invention make it possible to obtain an adhesive film exhibiting durable adhesive properties over time. In particular, it has been observed that adhesive performance can also be preserved after long exposure to heat.

Claims

1. Composition comprising:

at least one saturated polyester polyol (A), of which at least one saturated polyester polyol having a number-average molecular weight (denoted MnI) greater than or equal to 15,000 g / mol (denoted Al), and

at least one uretdione-type polyisocyanate (B) having at least two groups

NCO;

- optionally at least one organic solvent (C) capable of solubilizing the polyester (s) polyol (s) (A) without solubilizing the polyisocyanate (s) uretdione type (B).

2. Composition according to claim 1, comprising:

from 75 to 95% by dry weight of at least one saturated polyester polyol (A), of which at least one saturated polyester polyol (Al) having a number-average molecular weight (denoted MnI) greater than or equal to 15 000 g / mol, preferably greater than or equal to 18,000 g / mol, more preferably greater than or equal to 21,000 g / mol, still more preferably ranging from 21,000 to 75,000 g / mol, and more preferably ranging from 21,000 to 60,000. g / mol, relative to the total dry weight of the composition, and

from 5 to 25% by dry weight of at least one polyisocyanate (B) of uretdione type having at least two NCO groups, relative to the total dry weight of the composition.

3. Composition according to claim 1 or 2, such that the polyester polyol (s) (A) is (are) amorphous or semi-crystalline and preferably linear or branched (s). ).

4. Composition according to any one of claims 1 to 3, such that the (s) polyester polyol (s) saturated (s) (Al) is (are) semi-crystalline (s) and has (s) a lower Tg or equal to 0 ° C.

5. Composition according to any one of claims 1 to 4, such that the saturated polyester polyol (A) is a mixture of saturated polyester polyols further comprising at least one saturated polyester polyol (A2) other than (Al) having a subscript. hydroxyl greater than or equal to 15 mg KOH / g, preferably ranging from 20 to 90 mg KOH / g, more preferably from 30 to 60 mg KOH / g.

6. Composition according to claim 5, such that the (s) polyester polyol (s) saturated (A2) is (are) amorphous (s).

7. Composition according to any one of claims 1 to 6, such that the polyisocyanate (s) uretdione type (B) is (are) solid (s) at room temperature (20 ° C) and / or present (s) in the form of particles whose maximum particle size is less than 40μιη.

8. Composition according to any one of claims 1 to 7, such that the polyisocyanate (s) uretdione type (s) corresponds (e) to the following formula (I):

in which :

R is a divalent group comprising from 6 to 13 carbons and

n is an integer ranging from 0 to 10.

9. Composition according to any one of claims 1 to 8, such that the polyisocyanate (s) uretdione type (B) is (are) chosen from among the uretdione dimers of MDI and dimers d Uretdione of TDI, and more preferably the uretdione dimers of MDI.

10. Composition according to any one of claims 1 to 9, such that the content of polyisocyanate (s) uretdione type (B) is such that the molar ratio NCO / OH ranges from 0.5 to 1.5, preferably from 0.8 to 1.2, and more preferably is equal to about 1.

11. Composition according to any one of claims 1 to 10, comprising more than 1 ppm of organic solvent (s) (C), preferably more than 10 ppm by weight, preferably more than 100 ppm by weight, still more preferably more than 1000 ppm by weight, and preferably more than 10 000 ppm by weight of organic solvent (s) (C) relative to the total weight of said composition.

12. Composition according to any one of claims 1 to 11, comprising more than 30% by weight of organic solvent (s) (C), preferably more than 35% by weight, preferably more than 40%> by weight, and advantageously more than 45%> by weight of organic solvent (s) (C), relative to the total weight of said composition.

13. Composition according to claim 11 or 12, such that the organic solvent (s) (C) is (are) chosen from ketone type solvents, ethers, and mixtures thereof, and in particular aliphatic ketones such as acetone, methyl ethyl ketone (MEK), 2-pentanone, 3-pentanone, methyl isobutyl ketone, and mixtures thereof. More preferably, the organic solvent (C) is methyl ethyl ketone.

14. Use of the composition according to any one of claims 1 to 13 for manufacturing a heat activatable adhesive composition, especially in the form of monolayer film or multilayer.

15. Adhesive composition activatable by heat, in particular in the form of a monolayer film or multilayer of total thickness preferably ranging from 3μιη to 500μιη, comprising:

at least 75% by weight of at least one saturated polyester polyol (A) as defined in any one of the preceding claims, of which at least one saturated polyester polyol (Al) as defined in any one of the claims preceding,

from 5 to 25% by weight of at least one uretdione-type polyisocyanate (B) having at least two NCO groups, as defined in any one of the preceding claims, and

less than 0.5% by weight, preferably less than 0.1% by weight, of at least one organic solvent (C) as defined in any one of the preceding claims, relative to the weight total of the adhesive composition.