Patent Application
20200255692
This invention relates to cyanoacrylate composition, comprising: (a) a β-alkoxyakyl cyanoacrylate component, (b) a cyanoacrylate component selected from 2-methylbutyl cyanoacrylate, isoamyl cyanoacrylate, 2-ethylhexyl cyanoacrylate, 2-pentyl cyanoacrylate, 3-methylpentyl cyanoacrylate, 2-ethylbutyl cyanoacrylate, 3,7-dimethyloctyl cyanoacrylate, and combinations thereof; (c) a rubber toughening component; (d) a humidity resistance conferring component; and (e) a thermal resistance conferring component. Cured products of the inventive cyanoacrylate compositions demonstrate improved toughening, heat and humidity resistance without the odor experienced with conventional cyanoacrylate compositions or the blooming also experienced with conventional cyanoacrylate cured compositions.
Cyanoacrylate adhesive compositions are well known, and widely used as quick setting, instant adhesives with a wide variety of uses. See H. V. Coover, D. W. Dreifus and J. T. O'Connor, “Cyanoacrylate Adhesives” in Handbook of Adhesives, 27, 463-77, I. Skeist, ed., Van Nostrand Reinhold, New York, 3rd ed. (1990). See also G. H. Millet, “Cyanoacrylate Adhesives” in Structural Adhesives: Chemistry and Technology, S. R. Hartshorn, ed., Plenun Press, New York, p. 249-307 (1986).
U.S. Pat. No. 4,440,910 (O'Connor) pioneered rubber toughened cyanoacrylate compositions through the use of certain organic polymers as toughening additives that are elastomeric, i.e., rubbery, in nature. The '910 patent is thus directed to and claims a curable adhesive comprising a substantially solvent-free mixture of: (a) a cyanoacrylate ester, and (b) about 0.5% to about 20% by weight of an elastomeric polymer. The elastomeric polymer is selected from elastomeric copolymers of a lower alkene monomer and (i) acrylic acid esters, (ii) methacrylic acid esters or (iii) vinyl acetate. More specifically, the '910 patent notes that as toughening additives for cyanoacrylates, acrylic rubbers; polyester urethanes; ethylene-vinyl acetates; fluorinated rubbers; isoprene-acrylonitrile polymers; chlorosulfinated polyethylenes; and homopolymers of polyvinyl acetate were found to be particularly useful.
The elastomeric polymers are described in the '910 patent as either homopolymers of alkyl esters of acrylic acid; copolymers of another polymerizable monomer, such as lower alkenes, with an alkyl or alkoxy ester of acrylic acid; and copolymers of alkyl or alkoxy esters of acrylic acid. Other unsaturated monomers which may be copolymerized with the alkyl and alkoxy esters of acrylic include dienes, reactive halogen-containing unsaturated compounds and other acrylic monomers such as acrylamides.
U.S. Pat. No. 5,288,794 (Attarwala) is directed to an improved cyanoacrylate monomer adhesive formulation, where an effective amount, for enhancing the thermal resistance of the polymerized adhesive, of a mono, poly or hetero aromatic compound characterized by at least three substitutions on an aromatic ring thereof, two or more of the substitutions being electron withdrawing groups, is provided. Examples of the aromatic compound are given as 2,4-dinitrofluorobenzene; 2,4-dinitrochlorobenzene; 2,4-difluoronitrobenzene; 3,5-dinitrobenzonitrile; 2-chloro-3,5-dinitrobenzonitrile; 4,4′-difluoro-3, 3′-dinitrophenyl sulfone; pentafluoronitrobenzene; pentafluorobenzonitrile; α,α,α-2-tetrafluoro-p-tolunitrile and tetrachloroterphthalonitrile.
Prior to the discovery in the '794 patent, numerous attempts have been made to improve the thermal stability of cyanoacrylate adhesive bonds.
For instance, U.S. Pat. No. 3,832,334 is directed to the addition of maleic anhydride, which is reported to produce cyanoacrylate adhesives having increased thermal resistance (when cured) while preserving fast cure speed.
U.S. Pat. No. 4,196,271 is directed to tri-, tetra-and higher carboxylic acids or their anhydrides, which are reported to be useful for improving heat resistance of cured cyanoacrylate adhesives.
U.S. Pat. No. 4,450,265 is directed to the use of phthalic anhydride to improve heat resistance of cyanoacrylate adhesives. More specifically, the '265 patent is directed to and claims an adhesive composition comprising a polymerizable constituent the major part of which comprises at least one ester of 2-cyanoacrylic acid, characterized in that the composition additionally comprises a proportion of phthalic anhydride effective for favorably influencing the strength and/or durability of adhesive bonds formed from the composition, under exposure to moisture or elevated temperature. The effective amount is reported as 0.1% to 5.0%, such as 0.3% to 0.7%, by weight of the composition. The '265 patent reports the superiority of phthalic anhydride over compositions where no additive was used, and where maleic anhydride was used (though less pronounced in the case of stainless steel lapshears than in those of aluminum).
U.S. Pat. No. 4,532,293 is directed to the use of benzephenonetetracarboxylic acid or its anhydride and is said to provide a superior heat resistance for cyanoacrylate adhesives.
U.S. Pat. No. 4,490,515 is directed to cyanoacrylate compositions containing certain maleimide or nadimide compounds to improve hot strength properties.
U.S. Pat. No. 5,340,873 is directed to a cyanoacrylateadhesive composition having improved toughness and flexibility and consisting essentially of: a) a anoacrylate monomer; and b) an effective toughening amount of a saturated, hydroxy germinated polyester polymer derived from a dibasic aliphatic or aromatic carboxylic acid and a glycol and having repeating units of a specific structure where R is the organic residual of the dibasic carboxylic acid and R1 is the organic residue of the glycol, the polyester having a weight average molecular weight of from about 30,000 to 60,000 and a Tg of from about −40° C. to 30° C.
U.S. Pat. No. 6,833,196 is directed to a method of enhancing the toughness of a cyanoacrylate composition between steel and EPDM rubber substrates, comprising the steps of: providing a cyanoacrylate component; and providing a toughening agent comprising methyl methacrylic monomer and at least one of butyl acrylic monomer and isobornyl acrylic monomer, whereby the acrylic monomer toughening agent enhances the toughness of the anoacrylate composition such that whereupon cure, the cyanoacrylate composition has an average tensile shear strength of over about 4400 psi after 72 hours of room temperature cure and 2 hours post cure at 121° C.
Conventional commercial ethyl cyanoacrylate compositions have an odor, which some end users find offensive. β-methoxy ethyl cyanoacrylate is known to not have the same odor. And ethyl cyanoacrylate compositions are also known to show blooming when cured. β-methoxy ethyl cyanoacrylate tends not to.
Today there are no toughened, low odor/low bloom cyanoacrylate products commercially available in the market. Commercially available toughened cyanoacrylate products are predominately based on ethyl cyanoacrylate monomer and exhibit (1) an odor that some end users find offensive and/or (2) sometimes blooming when cured. And there are no such products that offer thermal and/or humidity resistance to cured products thereof.
Commercially available cyanoacrylate products are often toughened with an ethylene: methyl methacrylate terpolymer. This polymer contributes little toughness to cyanoacrylate compositions containing β-methoxy ethyl cyanoacrylate, one reason for which may be that the polymer shows sparing solubility in β-methoxy ethyl cyanoacrylate.
Notwithstanding the state of the art and the efforts to date to improve the toughness of β-alkoxyalkyl cyanoacrylate compositions, there remained a long felt, yet unmet, need to provide toughness to cured products of such cyanoacrylate compositions, and while doing so minimize the odor and/or blooming oftentimes associated with cyanoacrylate compositions, and in some instance confer thermal and/or humidity resistance to cured products thereof. Until now.
Cyanoacrylate compositions comprising: (a) a β-alkoxyakyl cyanoacrylate component, (b) a cyanoacrylate component selected from 2-methylbutyl cyanoacrylate, isoamyl cyanoacrylate, 2-ethylhexyl cyanoacrylate, 2-pentyl cyanoacrylate, 3-methylpentyl cyanoacrylate, 2-ethylbutyl cyanoacrylate, 3,7-dimethyloctyl cyanoacrylate, and combinations thereof; (c) a rubber toughening component; (d) a humidity resistance conferring component; and (e) a thermal resistance conferring component are thus provided.
This invention is also directed to a method of bonding together two substrates, which method includes applying to at least one of the substrates a composition as described above, and thereafter mating together the substrates.
In addition, the present invention is directed to reaction products of the inventive compositions.
Also, the invention is directed to a method of preparing the inventive compositions, and a method of conferring improved toughness, and thermal and humidity resistance to a cured product of a cyanoacrylate composition, without the odor experienced with conventional cyanoacrylate compositions or the blooming also experienced with conventional cyanoacrylate cured compositions.
The invention will be more fully understood by a reading of the section entitled “Detailed Description”, which follows.
As noted above, this invention is directed to a cyanoacrylate composition, which includes (a) a β-alkoxyakyl cyanoacrylate component, (b) a cyanoacrylate component selected from 2-methylbutyl cyanoacrylate, isoamyl cyanoacrylate, 2-ethylhexyl cyanoacrylate, 2-pentyl cyanoacrylate, 3-methylpentyl cyanoacrylate, 2-ethylbutyl cyanoacrylate, 3,7-dimethyloctyl cyanoacrylate, and combinations thereof; (c) a rubber toughening component; (d) a humidity resistance conferring component; and (e) a thermal resistance conferring component.
The β-alkoxyalkyl cyanoacrylate component (a) may be chosen from β-methoxymethyl cyanoacrylate, β-methoxyethyl cyanoacrylate, β-ethoxymethyl cyanoacrylate, β-ethoxyethyl cyanoacrylate and combinations thereof. Particularly desirable among those β-alkoxyalkyl cyanoacrylates is β-methoxyethyl cyanoacrylate.
The β-alkoxyalkyl cyanoacrylate component (a) should be included in the compositions in an amount within the range of from about 40% to about 90% by weight, with the range of about 55% to about 75% by weight being desirable, such as from about 55% to about 70% by weight or from about 55% to about 65% by weight, and about 60% by weight of the total composition being particularly desirable.
The cyanoacrylate component (b) may be selected from 2-methylbutyl cyanoacrylate, isoamyl cyanoacrylate, 2-ethylhexyl cyanoacrylate, 2-pentyl cyanoacrylate, 3-methylpentyl cyanoacrylate, 2-ethylbutyl cyanoacrylate, 3,7-dimethyloctyl cyanoacrylate, and combinations thereof. Particularly desirable among those cyanoacrylate components is isoamyl cyanoacrylate.
The cyanoacrylate component (b) should be included in the compositions in an amount within the range of from about 10% to about 50% by weight, with the range of about 20% to about 35% by weight being desirable, and about 30% by weight of the total composition being particularly desirable.
The rubber toughening component (c) may be selected from (i) reaction products of the combination of ethylene, methyl acrylate and monomers having carboxylic acid cure sites, (ii) dipolymers of ethylene and methyl acrylate, (iii) vinylidene chloride-acrylonitrile copolymers, (iv) vinyl chloride/vinyl acetate copolymer, (v) copolymers of polyethylene and polyvinyl acetate, and combinations thereof.
Desirably, the reaction products (c) (i) of the combination of ethylene, methyl acrylate and monomers having carboxylic acid cure sites, where the reaction products are substantially free of release agents, anti-oxidants, stearic acid and polyethylene glycol ether wax, β-alkoxyalkyl cyanoacrylate are chosen for use. DuPont supplies such a reaction product under the trade name VAMAC VCS 5500.
The rubber toughening component (c) should be included in the compositions in an amount within the range of from about 3% to about 20% by weight, with the range of about 5% to about 15% by weight being desirable, and about 8% by weight of the total composition being particularly desirable.
As a thermal resistance conferring component (d), benzonitriles should be used, such as those chosen from mono-, poly- or hetero-aromatic compounds characterized by at least three substitutions on an aromatic ring thereof, with two or more of the substitutions being electron withdrawing groups. Specific examples of such benzonitriles include 3,5-dinitrobenzonitrile; tetrafluoroisophthalonitrile 2-chloro-3,5-dinitrobenzonitrile; pentafluorobenzonitrile; α,α,α-2-tetrafluoro-p-tolunitrile; and tetrachloroterphthalonitrile.
The thermal resistance conferring component (such as a benzonitrile) should be present in an amount up to about 3% by weight, like about 0.01% to about 3% by weight, such as about 0.1% to about 1% by weight, with about 0.5% by weight being particularly desirable.
As a humidity resistance conferring component (e), hydrogenated anhydrides ordinarily the hydrogenated anhydride should be a hydrogenated phthalic anhydride, such as 3,4,5,6-tetrahydro phthalic anhydride. However, isomeric versions thereof and partially hydrogenated versions of phthalic anhydride may also be used.
The humidity resistance conferring component (such as a hydrogenated phthalic anhydride) should be used in an amount up to about 0.1% by weight, such as within the range of about 0.01 to about 0.09, desirably within the range of about 0.03 to about 0.05% by weight. At such level, a product label generated under the EINECS regulatory regime in Europe would not need to carry a “skin sensitizer” warning in order to be in compliance with that portion of the regulations.
Desirably, the 3,4,5,6-tetrahydrophthalic anhydride should be used in an amount of up to about 1% by weight, such as about 0.01% to about 1% by weight, and the pentafluorobenzonitrile should be used in an amount of up to about 0.5% by weight, such as about 0.01% to about 0.5% by weight.
A particularly desirable set of constituents to form the inventive compositions may include those listed below, in the broad ranges and the desired ranges. In a parcularly preferred embodiment, the inventive compositions also include citric acid in an amount of about 50-100 ppm, desirably in an amount of about 100 ppm.
Accelerators may also be included in the inventive cyanoacrylate compositions, such as any one or more selected from calixarenes and oxacalixarenes, silacrowns, crown ethers, cyclodextrins, poly(ethyleneglycol) di(meth)acrylates, ethoxylated hydric compounds and combinations thereof.
Of the calixarenes and oxacalixarenes, many are known, and are reported in the patent literature. See e.g. U.S. Pat. Nos. 4,556,700, 4,622,414, 4,636,539, 4,695,615, 4,718,966, and 4,855,461, the disclosures of each of which are hereby expressly incorporated herein by reference.
For instance, as regards calixarenes, those within the following structure are useful herein:
where R1 is alkyl, alkoxy, substituted alkyl or substituted alkoxy; R2 is H or alkyl; and n is 4, 6 or 8.
One particularly desirable calixarene is tetrabutyl tetra[2-ethoxy-2-oxoethoxy]calix-4-arene.
A host of crown ethers are known. For instance, any one or more of 15-crown-5, 18-crown-6, dibenzo-18-crown-6, benzo-15-crown-5-dibenzo-24-crown-8, dibenzo-30-crown-10, tribenzo-18-crown-6, asym-dibenzo-22-crown-6, dibenzo-14-crown-4, dicyclohexyl-18-crown-6, dicyclohexyl-24-crown-8, cyclohexyl-12-crown-4, 1,2-decalyl-15-crown-5, 1,2-naphtho-15-crown-5, 3,4,5-naphtyl-16-crown-5, 1,2-methyl-benzo-18-crown-6, 1,2-methylbenzo-5, 6-methylbenzo-18-crown-6, 1,2-t-butyl-18-crown-6, 1,2-vinylbenzo-15-crown-5, 1,2-vinylbenzo-18-crown-6, 1,2-t-butyl-cyclohexyl-18-crown-6, asym-dibenzo-22-crown-6 and 1,2-benzo-1,4-benzo-5-oxygen-20-crown-7 may be used. See U.S. Pat. No. 4,837,260 (Sato), the disclosure of which is hereby expressly incorporated herein by reference. Of the silacrowns, again many are known, and are reported in the literature.
Specific examples of silacrown compounds useful in the inventive compositions include:
See e.g. U.S. Pat. No. 4,906,317 (Liu), the disclosure of which is hereby expressly incorporated herein by reference.
Many cyclodextrins may be used in connection with the present invention. For instance, those described and claimed in U.S. Pat. No. 5,312,864 (Wenz), the disclosure of which is hereby expressly incorporated herein by reference, as hydroxyl group derivatives of an α, β or γ-cyclodextrin which is at least partly soluble in the cyanoacrylate would be appropriate choices for use herein as the first accelerator component.
For instance, poly(ethylene glycol) di(meth)acrylates suitable for use herein include those within the following structure:
where n is greater than 3, such as within the range of 3 to 12, with n being 9 as particularly desirable. More specific examples include PEG 200 DMA, (where n is about 4) PEG 400 DMA (where n is about 9), PEG 600 DMA (where n is about 14), and PEG 800 DMA (where n is about 19), where the number (e.g., 400) represents the average molecular weight of the glycol portion of the molecule, excluding the two methacrylate groups, expressed as grams/mole (i.e., 400 g/mol). A particularly desirable PEG DMA is PEG 400 DMA.
And of the ethoxylated hydric compounds (or ethoxylated fatty alcohols that may be employed), appropriate ones may be chosen from those within the following structure:
where Cm can be a linear or branched alkyl or alkenyl chain, m is an integer between 1 to 30, such as from 5 to 20, n is an integer between 2 to 30, such as from 5 to 15, and R may be H or alkyl, such as C1-6 alkyl.
When used, the accelerator embraced by the above structures should be included in the compositions in an amount within the range of from about 0.01% to about 10% by weight, with the range of about 0.1 to about 0.5% by weight being desirable, and about 0.4% by weight of the total composition being particularly desirable.
A stabilizer package is also ordinarily found in cyanoacrylate compositions. The stabilizer package may include one or more free radical stabilizers and anionic stabilizers, each of the identity and amount of which are well known to those of ordinary skill in the art. See e.g. U.S. Pat. Nos. 5,530,037 and 6,607,632, the disclosures of each of which are hereby incorporated herein by reference.
Other additives may be included in the inventive cyanoacrylate compositions, such as certain acidic materials (like citric acid), thixotropy or gelling agents, thickeners, dyes, and combinations thereof.
Of the accelerators and these additives, those listed in the table below are desirable examples, particularly in the amounts noted.
The cyanoacrylate component (b) may further include cyanoacrylate monomers which may be chosen with a raft of substituents, such as those represented by H2C═C(CN)—COOR, where R is selected from C1-15 alkyl, alkoxyalkyl, cycloalkyl, alkenyl, aralkyl, aryl, allyl and haloalkyl groups. Desirably, these additional cyanoacrylate monomers may be selected from methyl cyanoacrylate, ethyl-2-cyanoacrylate, propyl cyanoacrylates, butyl cyanoacrylates (such as n-butyl-2-cyanoacrylate), octyl cyanoacrylates, allyl cyanoacrylate, and combinations thereof. A particularly desirable one is ethyl-2-cyanoacrylate.
In another aspect of the invention, there is provided a method of bonding together two substrates, which method includes applying to at least one of the substrates a composition as described above, and thereafter mating together the substrates for a time sufficient to permit the adhesive to fixture.
In yet another aspect of the invention, there is provided reaction products of the so-described compositions.
When the composition is disposed between aluminum substrates and forms a cured product and is exposed to a temperature of 100° C. for a period of time of about 6 weeks, the cured product demonstrates improved temperature performance over a comparable composition without components (d) and (e).
When the composition is disposed between mild steel substrates and forms a cured product and is exposed to a temperature of 100° C. for a period of time of about 6 weeks or relative humidity conditions of 98% and a temperature of 40° C. for a period of time of about 6 weeks, the cured product demonstrates improved temperature performance over a comparable composition without components (d) and (e).
When the thermal resistance conferring component is tetrafluoroisophthalonitrile and when the composition is disposed between aluminum or mild steel substrates and forms a cured product and is exposed to a temperature of 120° C. for a period of time of about 6 weeks, the cured product demonstrates improved temperature performance over a comparable composition without components (d) and (e).
In still another aspect of the invention, there is provided a method of preparing the so-described compositions. The method includes providing a cyanoacrylate component, and combining therewith with mixing a hydrogenated anhydride and optionally a benzonitrile compound.
The invention will be further illustrated by the examples which follow.
All samples were prepared by mixing together the noted constituents for a sufficient period of time to ensure substantial homogeneity of the constituents. Ordinarily, about 30 minutes should suffice, depending of course on the quantity of the constituents used. Each of the samples also contained citric acid in an amount of 50 ppm, and a stabilizer package.
As controls, LOCTITE Power Easy and LOCTITE 435, were used. LOCTITE Power Easy is a β-methoxy ethyl cyanoacrylate thickened in a gel form with PMMA; LOCTITE 454 is an ethyl cyanoacrylate, rubber toughened with VAMAC VCS 5500, also in gel form.
*Tetrafluoroisophthalonitrile
+2,3,4,5,6-Pentafluorobenzonitrile
√3,4,5,6-Tetrahydrophthalic anhydride
Table A below shows the data captured for T-Peel strength performance on mild steel substrates of Sample A after ageing at room temperature, both with and without a 55 μm gap.
Reference to
Table B below shows the data captured for T-Peel strength performance on mild steel substrates of Samples A-C after ageing at room temperature for 1 week, both with and without a 55 μm gap. The two LOCTITE-branded products, Power Easy and 454, showed no performance under these conditions; consequently, no data is reported.
Samples B and C illustrate an improvement in toughness as measured by T-Peel strength performance on mild steel substrates.
Table C below shows the data captured for side impact strength performance on mild steel and aluminum substrates, respectively, of Samples A-C and LOCTITE Power Easy and LOCTITE 454 after ageing at room temperature for 1 week.
Side impact strength performance on mild steel substrates after room temperature curing for 1 week of each of Samples A-C exceeded 13.56 J, which is the maximum value observable in the test method. These values were at a minimum over two times as high as the LOCTITE-branded controls. Superior performance was also observed for these samples on aluminum substrates after curing at room temperature for 1 week. These values were at a minimum nearly three times as high as the LOCTITE-branded controls. See
Table D below shows the data captured for tensile strength performance on mild steel and aluminum substrates, respectively, of Samples A-C and LOCTITE Power Easy and LOCTITE 454 after ageing at room temperature for 3 days, 1 week, 3 weeks and 6 weeks.
Table E below shows the data captured for tensile strength performance on mild steel and aluminum substrates, respectively, of Samples A-C and LOCTITE Power Easy and LOCTITE 454 after ageing for 1 week at room temperature followed by aging at a temperature of 100° C. for 3 weeks and 6 weeks.
Reference to
Table F below shows the data captured for tensile strength performance on mild steel and aluminum substrates, respectively, of Samples A-C and LOCTITE Power Easy and LOCTITE 454 after ageing for 1 week at room temperature followed by aging at a temperature of 120° C. for 3 weeks and 6 weeks.
Reference to
Table G below shows data captured for tensile strength performance on mild steel and aluminum substrates, respectively, of Samples A-C and LOCTITE Power Easy and LOCTITE 454 after ageing at 1 week at room temperature followed by aging at 98% relative humidity and a temperature of 40° C. for 3 weeks and 6 weeks.
Reference to
At 100° C., the inventive samples outperformed the controls. At 120° C., temperature resistance is demonstrated, particularly over time, with the inventive samples, in particular Sample B on mild steel substrates. Impressive moisture durability is observed with the inventive samples, which significantly outperformed the controls.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1717711.4 | Oct 2017 | GB | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2018/079495 | Oct 2018 | US |
| Child | 16858660 | US |
