FR2910908A1 - Composition, useful as structural adhesive, comprises methacrylate ester monomer, elastomer block copolymer containing styrene and isoprene, elastomer block copolymer containing styrene and butadiene or ethylene, and elastomer - Google Patents

Abstract

Composition, useful in a structural adhesive, comprises a methacrylate ester monomer, an elastomer block copolymer (I) containing styrene and isoprene, at least an elastomer block copolymer (II) containing styrene and butadiene or ethylene, and an elastomer (III) having Hildebrand solubility parameter, which is compatible with Hildebrand solubility parameter of used block copolymers.

Description

The present invention relates to the field of structural adhesives

  acrylics (based on acrylate or methacrylate) and their applications. Structural adhesives are a good alternative to other mechanical techniques for bonding two materials together, such as metals or plastics. Indeed, the force distribution is better by bonding than when using alternative techniques such as riveting or welding. In addition, the use of gluing often makes it possible to work more quickly, and also has the advantage of offering better insulation against external elements (dust, moisture) than mechanical technologies. Structural adhesives are thus used in many industrial fields, even if they have certain disadvantages. In fact, the bond created during the polymerization of the adhesive (setting) is often rigid when good mechanical strength is required. Thus, if the elasticity of the adhesive is insufficient, a break can be observed when the two parts connected to each other are caused to undergo forces away from one another. Adhesives with good elasticity exist, but they often have low mechanical strength. It is therefore necessary to identify structural adhesives having both good mechanical strength (including shear strength) and satisfactory elasticity. Furthermore, it is important that these qualities be observed on different types of materials, and in particular on metal and on composite materials.

  The present invention proposes to solve the above problems by providing an adhesive composition having an elongation at break greater than or equal to 100%, and a tensile shear strength greater than 15 MPa on aluminum. The structural adhesives are composed of two elements, namely a catalyst element for carrying out the polymerization of the other element which contains monomers.

  The invention thus relates to a composition for use in a structural adhesive, comprising: (a) at least one methacrylate ester monomer (b) an elastomeric block copolymer containing styrene and isoprene (c) at least one elastomeric block copolymer containing styrene and butadiene or ethylene (d) an elastomer selected such that its Hildebrand solubility parameter is compatible with the Hildebrand solubility parameters of the block copolymers used.

  The composition according to the invention will thus be used with a polymerization catalyst.

  In a preferred embodiment, the ester monomer (a) is a methacrylate monomer. A methacrylate monomer is preferably selected in which the alcohol portion has a short linear chain (i.e. having one or two carbon atoms). Thus, the preferred monomers according to the invention are methyl methacrylate and ethyl methacrylate. In another embodiment, the alcohol moiety has at least one ring, which may be substituted or unsubstituted. Thus, in this embodiment, the monomers may in particular be chosen from tetrahydrofurfuryl methacrylate, phenoxyethyl methacrylate, isobornyl methacrylate, glycidylether methacrylate, benzyl methacrylate, cyclohexyl methacrylate and trimethylcyclohexyl methacrylate. .

  Mixtures of these esters can also be used. The percentage by weight of methacrylate in the composition is preferably between 20 and 80%, more preferably between 30 to 65%, even more preferably between 42 and 58%, ie around 50%. In a particular embodiment, the composition also contains at least one acrylic ester monomer (e) in which the alcohol portion has a linear chain of at least 6 carbon atoms (long chain). Thus, lauryl methacrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, esters based on polyethylene glycol or mixtures of these esters are preferably used. It is preferable that the composition contains at most 10%, more preferably at most 8% or even at most 5% by weight in total of these long chain acrylic monomers. In a particular embodiment, the composition comprises a mixture of two long chain acrylic ester monomers. Preferably, when the composition contains only one acrylic ester monomer (e), it is preferred that it be present in an amount of less than or equal to 8% by weight, while it is acceptable that there be it has an amount of between 8 and 10% when the composition contains a mixture of these esters (e). In this case, it is preferred that each is at most 5%.

  The composition may also contain other monomers such as acrylonitrile, methacrylonitrile, or styrene. The composition according to the invention also comprises a mixture of different block copolymers. Thus, it comprises a styrene-isoprene-styrene block copolymer (SIS) (b) and at least one block copolymer containing styrene and butadiene or ethylene (c). When it contains butadiene, this block copolymer may be styrene-butadiene-styrene (SBS) or a styrene-isoprene-butadiene-styrene copolymer (SIBS) such as Kraton MD6455 (Kraton Polymers Company) described by Dr. Donn DuBois and al., at the Adhesives & Sealants Council Meeting, Louisville, KY, 9-12 October 2005.

  When it contains ethylene, this block copolymer can be an SEBS (styrene-ethylene / butylene-styrene copolymer) or a SEPS (styrene-ethylene / propylene-styrene copolymer). These compounds are available in the Kraton G range (Kraton Polymers). In the preferred embodiment of the invention, the block copolymer (c) contains butadiene. Preferably, the styrene is present in a proportion of between 15 and 50%, more preferably between 22 and 40%, even more preferably about 28-33% by weight of the SBS copolymer. It is present in a proportion of between 12 and 24%, more preferably about 18-19% by weight in the SIS or SIBS copolymers. Preferably, the composition contains a mixture of SIS and SIBS in a proportion of varying from 4: 1 (by weight in the composition) to 1.5: 1. The preferred proportion of SIS over SIBS is of about 3: 1 or 3.3: 1. However, a mixture of SIS and SBS can also be used in the same relative proportions as the SIS / SIBS mixture. It is also possible to use a mixture of SIS, SIBS and SBS. It is also possible to add another block copolymer to one of these mixtures.

  The SIS, SBS or SIBS block copolymers that can be used according to the invention are well known to those skilled in the art. They are produced by Kraton Polymers (Houston, Texas, USA). Thus, Kraton D1160 SIS described in US 20050238603 or Kraton D1161, Kraton S1102 SBS described in US 5,106,917 and Kraton MD6455 or Kraton MD 6460 SIBS can be used.

  Those skilled in the art know how to select the SIS, SIBS, SBS block copolymers that can be used in the composition according to the invention, from among those existing, as a function, in particular, of their ease of dissolution in the monomers used, or of their tensile strength.

  Preferably, the composition according to the invention comprises between 10 and 30% by weight, preferably between 15 and 25%, more preferably between 18 and 25%, of the mixture between said SIS block copolymer and said butadiene-containing block copolymer. or ethylene.

  The composition according to the invention also contains an elastomer chosen so that it is compatible in solution with the block copolymers used. If necessary, it is functionalized (having a double bond at its ends, in particular methacrylate functions to improve the bonds with the monomers). In some cases, a liquid elastomer is chosen.

  In particular, it is chosen such that its Hildebrand solubility parameter is compatible with the Hildebrand solubility parameters of the block copolymers used. The Hildebrand solubility parameter is well known and is calculated by the square root of the cohesive energy density of the compound. In particular, the Hildebrand solubility parameter of the elastomer is between 8 and 9. Polybutadiene elastomers (which are then preferably chosen to be liquid and functionalized) are preferably used, polyisoprene. Polychloroprene (Neoprene AD10, DuPont, USA) can also be used.

  This elastomer is favorably present in an amount of between 6 and 15% by weight in the composition according to the invention, preferably between 8 and 12%. The relative proportions of the block copolymer mixture and the elastomer are from 4: 1 to 1: 1 by weight in the composition, preferably about 2: 1.

  The composition according to the invention may also contain an acidic monomer such as a free radical polymerizable acidic monomer known in the art of the unsaturated carboxylic acid type, maleic acid, crotonic acid, isophthalic acid, fumaric acid. Methacrylic acid or acrylic acid is preferred.

  The composition according to the invention may also contain, in its preferred embodiments, at least one additional compound chosen from a polymerization accelerator, a rheology agent and an adhesion promoter. The polymerization accelerator serves to promote the polymerization and hardening of the adhesive when the catalyst is added. It is a tertiary amine, preferably aromatic, such as dimethyl para-toluidine, and / or 2,2 '- (p-tolylimino) diethanol.

  The rheology agent serves to ensure a good viscosity of the composition according to the invention, so that it can be easily applied to the surfaces to be bonded. Polyamides such as Disparlon 6500 (Kusumoto Chemicals Ltd, Japan) can be used. The adhesion promoter is in particular a methacrylated phosphate ester, such as the methacrylate 2-hydroxyethyl phosphate ester (Genorad 40 from Rahn AG, Zurich, Switzerland). Other elements such as mineral fillers (TiO2, CaCO3, Al2O3, zinc phosphate), ultraviolet-resistant agents (such as 2-hydroxyphenyltriazine, Ciba-Geigy Tinuvin 400), wax, can also be used. added to the composition according to the invention. Free radical polymerization inhibitors such as BHT, or benzoquinones such as naphthoquinone, hydroquinone or ethylhydroquinone may also be added to increase the life of the composition.

  It is known that the structural adhesives are formed from two elements which are a composition according to the invention and a catalyst agent allowing the polymerization and the setting of the adhesive. These two elements are stored in two different compartments and are mixed during the application of the adhesive.

  This catalyst is a free radical polymerization initiator, particularly a peroxide based one, and is well known in the art. In particular, benzoyl peroxide, tertbutylperoxybenzoate and cumene hydroperoxide may be chosen. It is preferred when the catalyst contains between 5 and 40% by weight of peroxide, in particular about 20% by weight of peroxide. In particular, a paste containing approximately 20% of benzoyl peroxide is used. The catalyst is used in a ratio of 1: 1 to 1: 30, preferably 1: 5 to 1: 30, still more preferably about 1: 10 relative to the second element which is the composition according to the invention. .

  The invention is therefore based on the fact that the combined use of a styrene-isoprene-styrene elastomeric block copolymer, of an elastomeric block copolymer containing butadiene, or of ethylene, and of an elastomer with Hildebrand solubility parameter compatible with the Hildebrand solubility parameters of the block copolymers used makes it possible to obtain a composition for a structural adhesive which has an elongation at break greater than or equal to 100% and a superior tensile shear strength. or equal to 15, or even 17 MPa (on aluminum). This result is totally unexpected, because this adhesive thus has properties far superior to those described in the art. Furthermore, this adhesive also has excellent mechanical strength when used on a composite material. In fact, it is common that the mechanical strengths observed on metal are not always repeated on composite material. The use of a composition according to the invention therefore makes it possible to bond metal, plastics and composite materials to composite and thus finds application particularly in the field of the construction of silos, boats or truck trailers. . It can also be used in the field of automotive construction, or the railway field.

  Thus, the composition allows the adhesion of a material to another material, one or the other material being in particular a metal, a plastic, wood or a composite material. The composition can therefore be used in one of the following applications: adhesion metal / metal, metal / composite, metal / plastic, metal / wood, wood / plastic, wood / composite, wood / wood, plastic / composite , plastic / plastic or composite / composite. The composition according to the invention is thus particularly advantageous when it is necessary to bond a material to a composite material.

  The flexible structural methacrylate structural adhesives with high mechanical performance obtained with the composition according to the invention are resilient, resistant to shocks and vibrations. They make it possible to assemble by bonding between materials of the same or different chemical nature for example: concretes, wood, ceramics, glasses, ferrites, aluminum, anodized aluminum, steel, galvanized steel, stainless steel, painted metals, steel, copper , zinc, abs, PVC, polyester, acrylic, polystyrene, polyester or epoxy gel coat, composite materials, fiberglass reinforced composites, laminates, honeycombs, and any painted or lacquered material. They can also fill large gaps between the substrates, of different thicknesses, roughnesses, and flatness, with a better distribution of stresses. The flexibility of this composition thus makes it possible to take up the efforts of the differential expansions between the substrates over long lengths of several meters, by reducing and canceling the geometry defects (angle, roughness, flatness). The applications and activity sectors concerned include: Bonding reinforcements, rails, frames, beams, stiffeners, panels, partitions, fasteners, supports, body elements, reinforcing brackets, inserts, cylindrical and conical elements, hinges, frames, etc. . Bonding with laminate reinforcement on partition, bonding with filling requiring a high mechanical strength. In particular bonding of any structural or mechanical element glued into the shipbuilding, automotive, rail (and infrastructure), aeronautical, aerospace, electronic equipment, electromechanical, electrical appliances, military structures, signs, panels signaling (and advertising), street furniture, exterior joinery (windows, bay windows, patio doors, entrance doors and garages), wind turbines, containers, structures and infrastructure ( suspended bridges, offshore oil platforms, air terminals, etc.), construction and fastening and facade of building and solar panels.

  Examples The examples below illustrate the invention without restricting its scope. Example 1: raw materials used and methodology The following elements are used: methacrylate ester monomer (a): methyl methacrylate (MMA) monomer acrylate ester (e): lauryl methacrylate (LauMA), 2-15 ethylhexyl acrylate (AE2H SIS copolymer (b): Kraton D1160 (Kraton Polymers) SBS copolymer (c ': Kraton D1102 (Kraton Polymers) or SIBS copolymer (c): Kraton MD6455 (Kraton Polymers) functionalized liquid elastomer (d): Hycar VTB 2000x168 (Noveon , USA) 20 acid monomer: methacrylic acid (AMA) adhesion promoter: phosphate methacrylate Genorad 40 (Rahn AG) polymerization accelerator: dimethyl-para-toluidine (DMPT) rheology agent: Disparlon 6500 (Kusumoto Chemicals) catalyst: peroxide The tests are carried out according to the following protocols: ISO 527 is used to perform the tests for measuring the tensile strength RT, the elongation at break AR, the modulus the elasticity (Young's modulus, MY). The elongation is observed according to a method well known to those skilled in the art described in particular by ISO 527, the speed of stretching of the adhesive being constant and 50 mm / min.

  The tensile shear strength (Rc) is measured according to ISO 4587. Briefly, aluminum specimens 2024T3 of dimensions 100 x 25 x 1.6 mm (L x 1 x e) are used. Two specimens are glued to one another, the overlap area being 25 x 12 mm (300 mm 2), with a glue joint thickness of about 200 to 400 m. The force required to break the adhesion is then measured by pulling on the two test pieces. The T (Rp) peel strength is evaluated according to ISO 14173. Aluminum test specimens 100 x 25 x 1.5 mm or 100 x 25 x 0.8 mm galvanized steel are used, cover of 75 x 25 mm and a glue joint about 500 m thick.

  Results Sample 1 2 3 4 5 6 MAM 54 54 54 54 54 54 Kraton D 1102 21 21 - - - - Kraton D 1160 - - 21 21 - - Kraton - - - - 21 21 MD6455 VTB 2000x 168 10 10 10 10 10 10 AE2H 5 - 5 - 5 - LauMA - 5 - 5 - 5 AMA 5 5 5 5 5 5 Genorad 40 3 3 3 3 3 3 DMTP 1 1 1 1 1 1 Disparlon 6500 1 1 1 1 1 1 Total (weight) 100 100 100 100 100 100 The tested samples contain the block copolymer (b) or a block copolymer (c) according to the invention with an elastomer (d) .

  The results obtained are as follows: Sample 1 2 3 4 5 6 5 RT (MPa) 22 19.1 21.1 18.1 20.3 21.8 aluminum Rp (N / mm) 12.4 13.8 20, 5 12.0 16.4 11.3 aluminum Rp (N / mm) 8.9 12.9 17.2 17.0 10.8 16.7 galvanized steel RT (MPa) 12.4 14.0 9.4 10.2 11.5 11.3 AR (%) 43.2 53.2 50.2 50, 8 88.0 66.1 MY (MPa) 268 295.7 173.8 185.4 181.2 193, These results demonstrate that the presence of only two elements chosen from (b), (c) and (d), makes it possible to obtain a good tensile shear strength on aluminum, but an insufficient elongation at break because less than 100. %.

  Other compounds are tested as follows: Sample 7 8 9 10 MAM 54 50.2 50.2 54 Kraton D 1102 5 - - 5 Kraton D 1160 16 16 16 - Kraton - 5 5 16 MD6455 VTB 2000x168 10 10 10 10 AE2H 2.5 8.8 2.5 2.5 LauMA 2.5 - 3.8 2.5 AMA 5 5 5 5 Genorad 40 3 3 3 3 DMTP 1 1 1 1 Disparlon 6500 1 1 1 1 Total (weight ) 100 100 100 100 These samples contain a mixture of the compounds (b), (c) and (d), the sample being a new sample in which the compound (b) is absent.

  The results obtained are as follows: Sample 7 8 9 10 RT (MPa) 18.1 20.5 21.2 24.3 aluminum Rp (N / mm) 15.8 17.3 18.0 9.6 aluminum Rp ( N / mm) 25.1 17.5 16.2 15.7 Galvanized steel RT (MPa) 10.4 9.6 10.2 10.0 AR (%) 112.6 251.0 205.7 26.1 MY (MPa) 182.2 95.7 143.5 166.3 It is clear that the joint presence of elements (b), (c), (d) makes it possible to maintain excellent resistance to tensile shear and to obtain an unexpected effect on elongation at break (elasticity), which then becomes greater than 100%. It is also noted that the results observed for peel or tensile strength are maintained.

  New samples are tested: Sample 7 11 13 8 12 14 MAM 54 64 55.7 50.2 60.2 55.7 Kraton D 1102 5 5 7 - - - Kraton D 1160 16 16 23 16 16 23 Kraton - - - 5 5 7 MD6455 VTB 2000x168 10 - - 10 - - AE2H 2.5 2.5 2.2 8.8 8.8 4.3 LauMA 2.5 2.5 2, 1 - - - AMA 5 5 5 5 5 5 Genorad 40 3 3 3 3 3 3 11 DMTP 1 1 1 1 1 1 Disparlon 6500 1 1 1 1 1 1 Total (weight) 100 100 100 100 100 100 These samples confirm the importance of the presence of compound (d). It should be noted that the compound (d) being present at 10% by weight in the composition for the samples 7 and 8, this percentage was distributed in full on the methyl methacrylate (samples 11 and 12), or partially on the monomer and compounds (b) and (c), keeping the initial proportions to a minimum (samples 13 and 14).

  The following results are obtained: Sample 7 11 12 8 13 14 RT (MPa) 18.1 18.3 16.8 20.5 24.3 16.8 aluminum Rp (N / mm) 15.8 7.9 4, 9 17.3 12.9 5.4 aluminum Rp (N / mm) 25.1 11.3 6.9 17.5 14.9 8.7 galvanized steel RT (MPa) 10.4 7.7 5.8 9.6 6.4 4.1 AR (%) 112.6 7.0 31.5 251.0 12.0 49.0 MY (MPa) 182.2 213.7 63.0 95.7 154.2 25.4 These results demonstrate the importance of the presence of the compound (d) to obtain an elongation at break greater than 100%.

  Adhesion to composite material: The bonding test was carried out by adhesion of galvanized steel to polyester gelcoat. The quality of adhesion is noted according to the following convention: +++: excellent ++: good +: average 20 -: bad10 Sample Adhesion galvanized steel / polyester gelcoat 1 ++ 2 ++ 3 ++ / +++ 4 + + / +++ ++ / +++ 6 + / ++ 7 +++ 8 + / ++ 9 +++ + 11 + / ++ 12 + 13 - 14 - It is observed that the adhesion to composite material is very satisfactory for the compositions according to the invention.

Claims (12)

claims   A composition for use in a structural adhesive, comprising: (a) at least one methacrylate ester monomer (b) an elastomeric block copolymer containing styrene and isoprene (c) at least one elastomeric block copolymer containing styrene and butadiene or ethylene (d) an elastomer selected such that its Hildebrand solubility parameter is compatible with the Hildebrand solubility parameters of the block copolymers used.   2. Composition according to claim 1, characterized in that the said elastomeric block copolymer (c) is chosen from a styrene-butadiene-styrene copolymer (SBS) and a styrene-isoprene-butadiene-styrene copolymer (SIBS).   3. Composition according to one of claims 1 or 2, characterized in that said elastomer (d) is selected from polybutadiene and polyisoprene.   4. Composition according to one of claims 1 to 3, characterized in that it comprises between 7 and 15% by weight of said elastomer (d).   5. Composition according to one of claims 1 to 4, characterized in that it comprises between 15 and 25% by weight of the mixture between said elastomeric block copolymer (b) and said elastomeric block copolymer (c).   6. Composition according to one of claims 5 to 5, characterized in that it also comprises at least one acrylate ester monomer in which the alcohol portion has at least one linear chain of at least 6 carbon atoms (e).   7. Composition according to claim 6, characterized in that said one acrylate ester monomer (e) is a methacrylate or acrylate monomer.   8. Composition according to one of claims 6 or 7, characterized in that it contains a mixture of two monomers acrylate (e).   9. Composition according to one of claims 6 to 8, characterized in that it comprises less than 10% by weight of acrylate monomer (e).   10. Composition according to one of claims 1 to 9, characterized in that it also contains at least one additional compound selected from a polymerization accelerator, a rheology agent, an adhesion promoter, an acidic monomer.   11. The combined use of an elastomeric block copolymer containing styrene and isoprene, at least one elastomeric block copolymer containing styrene and butadiene or ethylene and a functionalized liquid elastomer chosen so that its Hildebrand solubility parameter is compatible with the Hildebrand solubility parameters of said elastomeric block copolymers for the preparation of a composition usable as a structural adhesive having an elongation at break greater than or equal to 100% and a resistance tensile shear greater than or equal to 15 MPa on aluminum.   12. Use of a composition according to one of claims 1 to 10 to allow adhesion of a material on another material.