COMPOSITION FOR STRUCTURAL ADHESIVES

Abstract

The invention relates to an acrylic structural adhesive composition containing (meth)acrylate monomers at least 20% of which is a mixture of 1,3-Dioxan-5-yl methacrylate and 1,3-Dioxolan-4-ylmethyl methacrylate, as well as block copolymers, elastomers and particles formed of a thermoplastic shell and an elastomeric core.

Claims

1. A composition that can be used in a structural adhesive, the composition comprising (by weight): (a) between 35% and 60% of (meth)acrylate monomers, including i. at least 20% of a monomer of formula (I), a monomer of formula (II), or a mixture thereof ##STR00012## wherein R, R1, and R2 are independently H or CH.sub.3, and ii. at least 5% of one or more other (meth)acrylate monomer(s), (b) from 8 to 30% of particles formed from a thermoplastic shell and an elastomeric core, (c) between 9 and 15% of an elastomeric block copolymer comprising styrene and at least one second monomer, or a mixture of such block copolymers, and (d) between 5 and 25% of an elastomer; wherein the sum of components (b), (c), and (d) is at least 35%.

2. The composition according to claim 1 comprising a mixture of the monomer of formula (I) and the monomer of formula (II) that is a mixture of 1,3-dioxan-5-yl methacrylate and 1,3-dioxolan-4-ylmethyl methacrylate.

3. The composition according to claim 1 comprising between 25 and 35% of the monomer of formula (I) and/or the monomer of formula (II), and at least 10% of the other (meth)acrylate monomer(s).

4. The composition according to claim 1, wherein the other (meth)acrylate monomer(s) are selected from the group consisting of isobornyl methacrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, lauryl methacrylate, polyethylene glycol-based esters, and mixtures of these esters.

5. The composition according to claim 1 comprising at least 5% of 2-ethylhexyl acrylate.

6. The composition according to claim 1, wherein the particles of (b) the elastomeric block copolymer of (c), and the elastomer of (d) contain butadiene.

7. The composition according to claim 1 comprising from 15 to 25% of the particles of (b), wherein the particles consist of a thermoplastic shell and an elastomeric core (b).

8. The composition according to claim 1 between 9 and 12% of the elastomeric block copolymer of (c).

9. The composition according to claim 1 comprising between 10 and 25% of the elastomer of (d).

10. The composition according to claim 1, wherein the particles of (b) are chosen from acrylonitrile-butadiene-styrene, methacrylate-butadiene-styrene, methacrylate-acrylonitrile-butadiene-styrene, methacrylate-acrylonitrile particles, and mixtures thereof.

11. The composition according to claim 1 comprising up to 26% of the particles of (d).

12. The composition according to claim 1, wherein the second monomer of the elastomeric block copolymer of (c) is chosen from isoprene and butadiene.

13. The composition according to claim 1, wherein the elastomeric block copolymer of (c) is selected from SIS, SBS, SIBS, SEBS, and mixtures thereof.

14. The composition according to claim 1, wherein the elastomer of (d) is chosen from non-functionalized polybutadiene, polybutadiene functionalized by carboxyl ends, polybutadiene functionalized by vinyl ends, polyisoprene, polychloroprene, and mixtures of these elements.

15. The composition according to claim 1, further comprising an amine selected from the group consisting of toluidines, anilines, and substituted or unsubstituted phenols.

16. The composition according to claim 1, further comprising a crystal violet lactone or 4,4′,4″ methylidynetris (N, N-dimethylaniline).

17. The composition according to claim 1, further comprising a phosphate ester-based adhesion promoter, preferably methacrylated.

18. The composition according to claim 17, wherein the phosphate ester-based adhesion promoter is 2-hydroxyethyl methacrylate phosphate ester or a mixture of 2-hydroxyethyl methacrylate mono- and di-phosphate esters.

19. The composition according to claim 1, further comprising a metal acrylate monomer.

20. (canceled)

21. A two-component structural adhesive comprising: a. a composition according to claim 1, and b. a polymerization catalyst agent, for addition to the composition to initiate polymerization of the meth(acrylate) monomers, comprising a free radical polymerization initiator.

22. The two-component structural adhesive according to claim 21, wherein the free radical polymerization initiating agent present in the polymerization catalyst agent is a peroxide, in particular benzoyl peroxide, in an amount between 5 and 40% (preferably between 10 and 20%) by weight of polymerization initiating agent.

23. The two-component structural adhesive according to claim 21, wherein the polymerization catalyst agent also contains between 1 and 30% by weight of an epoxidized silane.

24. The two-component structural adhesive according to claim 21, wherein the polymerization catalyst agent additionally contains an epoxy resin.

25. (canceled)

26. A cartridge for applying a two-component structural adhesive according to claim 21 comprising: i. a compartment containing the composition; and ii. another compartment containing the polymerization catalyst agent.

27. (canceled)

28. (canceled)

29. A method of bonding a first material to a second material comprising: i. applying a composition according to claim 1 mixed with a polymerization catalyst agent comprising a free radical polymerization initiator to the first material, and ii. applying the second material over the first material, thereby bonding the two materials to each other after polymerization.

Description

EXAMPLES

[0233] The examples below illustrate the invention without restricting its scope. The compositions described are also the subject of the invention.

Example 1: Raw Materials Used and Methodology

[0234] The following elements are used:

[0235] Composition (Resin) [0236] (meth)acrylate ester monomer: see below [0237] functionalized liquid elastomer: HYPRO™ VTB 2000×168 (EPM, USA) [0238] acid monomer: methacrylic acid (MAA) [0239] adhesion promoter: methacrylate phosphate Genorad 40 (Rahn AG) [0240] polymerization accelerator: N-(2-Hydroxyethyl)-N-Methyl-para-toluidine (MHPT, CAS 2842-44-6) [0241] toluidine (d): N,N-bis-(2-hydroxyethyl)-p-toluidine (PTE) [0242] Zinc dimethacrylate: SR 708 (Sartomer) [0243] Fillers: metal ions, rheology agents, powdery agents [0244] SBS copolymer: Kraton D1102 (Kraton Polymers) [0245] SIS copolymer: Kraton D1114 (Kraton Polymers) [0246] SIBS copolymer: Kraton D1171 (Kraton Polymers) [0247] Rheology agent: Disparlon 6500 (Kusumoto Chemicals) [0248] Elastomeric polymeric particles (core shells, MBS): Cleartrength C303H, XT100 (Arkema), FM50 Sundow Polymers

[0249] Catalyst Agent

[0250] 20% benzoyl peroxide, with or without epoxidized silane (see WO2011033002).

[0251] Composition:catalyst mixing ratio=10:1

[0252] The tensile shear strength (SS) is measured according to the ISO 4587 standard. Briefly, 2024T3 aluminum test pieces measuring 100×25×1.6 mm (L×W×E) are used. Two test pieces are bonded to each other with an overlap area of 25×12 mm (300 mm.sup.2) with an adhesive joint thickness of approx. 200 to 400 μm. The force required to break the bond is then measured by pulling on both test pieces.

[0253] The ISO 527 standard is used to carry out the tests to measure the elongation at break EB. Elongation is observed according to a method well known to those skilled in the art, described in particular by ISO 527, with a pull rate of the adhesive being a constant 50 mm/min.

[0254] The Tensile peel strength (PS) is evaluated according to the ISO 14173 standard. Aluminium test pieces 2024T3 measuring 200×25×1.6 mm are used, which are bonded with an overlap of 150×25 mm and an adhesive joint thickness of approx. 500 μm.

EXAMPLES

Example 1. Dissolution Test of Block Copolymers in Different Monomers

[0255] The blending capability of different monomers with SBS and SIS block copolymers was evaluated.

[0256] The reference was the monomer MMA (methyl methacrylate) which has a ratio (Monomer/(SIS-SIBS mixture or SBS mixture)) of 65/35.

[0257] THFMA (tetrahydrofurfuryl methacrylate), MAISOBOR, BZMA (Benzyl methacrylate), MA2EH, cHMA (cyclohexyl methacrylate), A2EH, LAUMA (lauryl methacrylate) were observed to have more or less the same mixing ratios as the reference (62.5/37.5 to about 75/25). On the other hand, it was complicated to obtain block copolymer ratios compatible with prior art data when mixed with IGPMA (almost impossible mixing) or GLYFOMA (no more than 20% block copolymer), due to a mixture viscosity that was unusable in practice.

Example 2. Reproduction of Prior Art Compositions with Selected Monomers

[0258] Using the monomers identified in Example 1, for which blending with block copolymers is possible, compositions similar to the compositions of the prior art (described in particular in WO2008125521A1) were tested.

[0259] The examples in this application describe compositions that include [0260] (Meth)acrylate monomer 50-60%. [0261] Block copolymers (SBS, SIS, SIBS or blends): between 15 and 22%. [0262] Elastomer (functionalized polybutadiene): between 7-10%. [0263] Core-shells: 10-15%. [0264] Other compounds: qsp 100

[0265] Compositions with the same proportions of components have been made, using the following methacrylate monomers: THFMA, MAISOBOR, BZMA, MA2EH, cHMA, LAUMA.

[0266] Shear strengths were between 3.2 and 17.4 MPa.

[0267] Peel strengths ranged from 1.6 to 9.6 N/mm.

[0268] The composition with a peel strength of 9.6 N/mm had a shear strength of 7.3 MPa.

[0269] The composition with a shear strength of 17.4 MPa had a peel strength of 3.3 N/mm.

[0270] Compositions were also prepared in which mixtures of monomers (MAISOBOR and MA2EH in various proportions, BZMA and MA2EH, or MAISOBOR, BZMA and MA2) were made. The amounts of block, core-shell or elastomer copolymers were similar to the previous art (see above).

[0271] Shear strengths ranged from 11.2 to 16.3 MPa.

[0272] Peel strengths ranged from 2.1 to 7.7 N/mm.

[0273] The composition with a peel strength of 7.7 N/mm had a shear strength of 12.6 MPa.

[0274] The composition with a shear strength of 16.3 MPa had a peel strength of 2.1 N/mm.

[0275] Thus, compositions containing MAISOBOR (29%), MA2EH (27.2%), 17.8% SBS, 7.5% VTB, 10% core-shells were made, and a peel strength lower than 3.2 N/mm was obtained.

[0276] Using a mixture of BZMA (41.1%) and MA2EH (14.4%), SBS (18.1%), VTB (7.7%), core-shells (11.2%), a peel strength of 5.9 N/mm was obtained.

[0277] Thus, simply substituting methyl methacrylate with monomers (or mixtures of monomers) having a lower odor than methyl methacrylate, in prior art compositions does not allow the mechanical properties of these prior art compositions to be maintained. Generally speaking, it is very complicated to obtain a good peel strength of more than 10 N/mm.

Example 3. Compositions with Low Odor and Good Mechanical Properties

[0278] In order to obtain compositions with a low odor and mechanical performance similar to those of the prior art compositions (WO2008125521A1 or WO2008080913), the inventors increased the amount of core-shell and decreased the amount of block copolymers.

[0279] Surprisingly, these changes in proportions, and the use of the monomers that were not selected after the results obtained in Example 1, lead to results similar to those of the prior art and much better than those obtained in Example 2 alone.

TABLE-US-00001 TABLE 1 Results obtained with various compositions. 1 2 3 4 5 GLYFOMA 51.4 42.2 36.2 25.9 35.8 IPGMA MAISOBOR 6.3 MA2EH 12.6 A2EH 9.6 8.3 8.3 HEMA 5 4.5 5 SBS D1102 9.8 13.6 11.8 SIS D1114 7 9.2 SIBS D1171 2.2 2.9 VTB2000x168 6.8 7 6.1 9.9 6.1 AMA 4.5 4.6 4 5.3 4 GENORAD 40 2.1 2.1 3 3.1 3 MHPT 0.5 0.4 0.3 0.3 0.4 PTE 0.3 0.3 0.3 0.2 0.3 XT100 (MBS) 24.6 20.2 25 22.7 25 Total 100 100 100 100 100 SS (Mpa) 22 18.3 ND 20.5 ND PS (N/mm) 12 14 10.8 10.4 17 EB (%) 12 117 ND 40 192 6 7 8 9 10 GLYFOMA 29.4 24.1 26.1 24.5 IPGMA 27.6 MAISOBOR 8 10 10.1 15 8 MA2EH A2EH 6.7 10 7.4 5 10 HEMA 5 5 4.7 5 4 SBS D1102 SIS D1114 7.2 8.2 7.1 7.9 7.4 SIBS D1171 2.2 2.6 2.2 2.5 2.3 VTB2000x168 7.6 7.5 7.1 7.5 7.5 AMA 4 4 3.8 4 4 GENORAD 40 3 3 5 3 3.5 MHPT 0.3 0.4 0.3 0.4 0.4 PTE 0.2 0.2 0.2 0.2 0.3 XT100 (MBS) 26.4 25 26 25 25 Total 100 100 100 100 100 Mechanical results SS (Mpa) ND ND ND 19 14.4 PS (N/mm) 15.7 14 17 14.7 10.6 EB (%) 146 153 80 56 220 ND: not determined

[0280] The results presented above clearly show that the increase in the amount of particles formed from a thermoplastic shell and an elastomeric core (core-shells) above 20%, and the decrease in the amount of block copolymers (SBS, SIS, SIBS), using at least 20% of compounds of the general formula (I) or (II), alone or with other methacrylate monomers, gives compositions with a peel strength of more than 10 N/mm and good shear strength and/or elongation at break.

[0281] In most cases, good peel strength, good shear strength and good elongation at break are obtained, although in some cases only good peel strength and good shear strength without significant elongation at break, or good peel strength, good elongation at break, and somewhat lower shear strength can be observed.

[0282] In addition, the adhesives obtained have a low odor compared to the adhesives of the prior art obtained with methyl methacrylate as a monomer. In particular, the use of GLYFOMA or IGPMA makes it possible to considerably reduce (practically eliminate) odours, thus making these adhesives easy to use on production lines (automotive, electronics, etc.).

[0283] Other compositions have also been prepared.

TABLE-US-00002 TABLE 2 Results obtained with various compositions 11 12 13 14 15 GLYFOMA 29.7 28.1 28.1 31.8 30.5 MAISOBOR 7.3 5.2 1.0 — 7.6 A2EH 6.8 6.5 6.5 6.5 7.0 HEMA 4.7 4.0 3.1 5.1 4.9 SBS D1102 13.9 SIS D1114 7.5 7.2 7.2 — 7.8 SIBS D1171 2.3 2.2 2.2 — 2.4 VTB2000x168 13.1 18.0 25.0 18 13.6 AMA 5.2 5.8 5.0 2.9 5.4 GENORAD 40 3.0 3.0 3.0 3 3.5 MHPT 0.5 0.5 0.5 0.5 0.5 PTE 0.5 0.5 0.5 0.5 0.5 XT100 (MBS) 19.4 19.0 17.9 17.8 — C303H (MBS) — — — — 16.3 Total 100 100 100 100 100 SS (Mpa) 20.1 17.5 17.0 20.4 19.1 PS (N/mm) 14.5 16.3 16.7 11.5 10.2 EB (%) 100.4 155.2 136.9 117.8 110.3

[0284] The above examples show that the observed performance can be maintained by varying the amounts of monomers and other compounds. Tg are also acceptable (above 80° C.). Thus, by following the teaching of the application (nature and proportions of components to be used), one of skill in the art is able to adapt the different proportions while maintaining performances as described above.