Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J4/00—Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J5/00—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/46—Manufacturing multilayer circuits

Definitions

• This invention relates to one part cyanoacrylate adhesive compositions having improved bonding and/or thermal bonding performance and which are particularly useful for bonding polar surfaces, such as glass and metal surfaces, and other high energy surfaces, such as ceramics, quartz and certain plastics, especially flame-treated plastics and engineering plastics such as those of polycarbonates, polysulfones, polyimides, polyetheretherketones (PEEK) or phenolic-type or epoxy-based plastics.
• polar surfaces such as glass and metal surfaces
• other high energy surfaces such as ceramics, quartz and certain plastics, especially flame-treated plastics and engineering plastics such as those of polycarbonates, polysulfones, polyimides, polyetheretherketones (PEEK) or phenolic-type or epoxy-based plastics.
• PEEK polyetheretherketones
• Cyanoacrylate adhesive compositions are noted for their rapid bonding activity i.e very low fixture times. However if their usefulness for bonding some surfaces, in particular polar surfaces, is to be increased, the bond strength performance needs to be improved. On glass, the bond strength retention is unsatisfactory at room temperature as well as at elevated temperatures. On metal surfaces such as mild steel the bond strength performance tends to deteriorate at elevated temperatures.
• U.S. Patent No. 5,290,825 (Lazar) describes cyanoacrylate compositions that are temporarily inhibited from polymerizing and curing even in the presence of activating substances, such as metals, the inhibition-stabilization being accomplished by an inhibitor-stabilizer including an organic carboxylic acid, and a hydrated or anhydrous metal chloride, fluoride, bromide or iodide.
• the metal halide salts used in the working examples of Lazar are MgBr.6H 2 0, SnCl 2 .6H 2 0, and FeCl 3 .6H 2 0.
• Other metal halide salts mentioned include LiF, LiI.3H ? 0, LiI.H ? 0 and MgCl 2 -
• metal halide salts are too reactive for the purposes of the present invention. Accordingly, Lazar reports a solution different from that taught herein.
• Robins describes a two-part adhesive system wherein one part includes an alpha-cyanoacrylate monomer with a stabilizer and the other part is a weakly acidic or weakly basic ionic accelerator compound including a cation M and an anion A.
• the pKa relating to cation M in the equilibrium is defined by
• the nucleophilicity constant of anion A is less than about 2 when cation M is an onium cation comprising more than 8 carbons, with the nucleophilicity constant being determined relative to methyl iodide. + + + The cation M is disclosed in Robins to be K , Na , Ca ,
• a quaternary ammonium cation e.g. tetraethyl ammonium cation, tetrapropyl ammonium cation, tetrabutyl ammonium cation, trimethylethyl ammonium cation, dimethyldiethyl ammonium cation, and trimethylbutyl ammonium cation.
• anion A examples are perchlorate, iodide, bromide, chloride, chlorate, thiocyanate, nitrate, phenylsulfonate, methyl phenyl sulfonate, methyl sulfonate, trifluoroacetate, tetrafluoroborate, periodate, triflate, hexafluorophosphate, hexafluoroantimonate and hexafluoroarsenate.
• the accelerator compounds include lithium triflate (CF ⁇ SO ⁇ Li), lithium bromide (LiBr) and magnesium bromide (MgBr,-,) .
• This two-part adhesive system is said to exhibit suitable cure rates when employed on wooden substrates.
• Robins set out to solve was the slow curing of cyanoacrylate adhesive on wooden substrates.
• the objective therefore is to compensate for the slow curing (due to the acidic nature of wooden substrates) by using a suitable accelerator to enhance cure speeds.
• the salts listed in the Robins patent are said to increase the cure speed of the cyanoacrylate adhesive, acting as accelerators to the curing process.
• the alternative use of the composition on other substrates such as on glass, metal and plastics is mentioned.
• Robins compositions relate to substrates other than wooden substrates and there is no teaching about polar or high energy surface substrates. Robins is silent with respect to one-part cyanoacrylate adhesive compositions.
• FR 2,187,870 discloses a stable adhesive of a substituted olefinic monomer, which polymerises easily by anionic polymerisation, in particular which may be polymerised by weak Lewis bases.
• the adhesives are stabilised on storage and during processing by the addition of an effective amount of an onium-type salt.
• the stabilisers may alternatively be phosphoniu salts.
• the salts are solids and are stated not to have adverse effects on the curing of cyanoacrylate. The inventors were thus seeking salts which would stabilise the adhesive composition on storage but which would not slow down the rate of cure of the adhesive.
• GB 2 228 943A Loctite (Ireland) Limited describes one-part cyanoacrylate adhesive compositions suitable for bonding porous or non-active surfaces containing a phase transfer catalyst of the formula
• C is a cation other than sulfonium, e.g. ammonium, a quaternary chlorometallate, pyrilliu , thiopyryll ium, iodoniu , phosphoniu , metalloceniu , or diazonium; and
• a " is an anion of relatively low nucleophilicity which does not initiate polymerization of the cyanoacrylate monomer.
• CA cyanoacrylate
• RT room temperature
• TBAHFP tetrabutyl ammonium hexafluorophosphate
• GBMS grit blasted mild steel (lapshears)
• Cx calixarene
• the present invention overcomes the problems noted above, and provides cyanoacrylate compositions having improved bonding and/or thermal bonding performance, particularly on polar substrates and other high energy surfaces. That is, provides a one-part cyanoacrylate adhesive composition including a cyanoacrylate monomer and a salt of a cation which is a hard Lewis acid with an anion of low nucleophilicity which does not initiate polymerization of the cyanoacrylate monomer.
• Figure 1 is a graph of shear strength (mPa) against salt concentration ( w/w) which shows shear strength performance (RT pulled) after heat ageing at 120°C of soda glass bonded with ethyl CA containing a range of LTFB concentrations.
• Figure 2 shows shear strength performance (RT pulled) after heat ageing for 24 hours at 120°C of soda glass laps bonded with ethyl CA containing very low salt levels of LHFP.
• Figure 3 shows shear strength performance (RT pulled) after heat ageing at 120°C of soda glass bonded with ethyl CA containing LTFB or MTFB .
• Figure 4 is a graph of fixture time (seconds) against formulation ageing time (weeks) and shows the effect of LTFB on the fixture times of soda glass laps which were bonded with ethyl CA formulations had been subjected to accelerated ageing at 55 C.
• the control formulation "set-up" after nine weeks.
• Figure 4a is a similar graph showing the effect of LTFB on the fixture times (minutes) of GBMS lapshears which were bonded with ethyl CA formulations which had been subjected to accelerated ageing at 55°C.
• the control formulation "set up" after three weeks.
• Figure 5 is a graph of shear strength (mPa) against ageing time (weeks) and shows the effect of LTFB on the heat aged (120°C) shear strength (RT pulled) of GBMS laps bonded with ethyl CA.
• Figure 6 shows the effect of LHFP on the heat aged (120°C) shear strength (RT pulled) of GBMS laps bonded with ethyl CA.
• Figure 7 shows the effect of MTFB on the heat aged (120°C) shear strength (RT pulled) of GBMS laps bonded with ethyl CA.
• Figure 8 is a shear strength diagram and shows the separate and combined effects of the lithium cation and the hexafluorophosphate anion on the shear strength of ethyl CA bonded GBMS laps which were heat aged at 120°C and pulled at RT.
• Figure 9 shows the effect of 0.5% w/w calixarene (Cx) on the shear strength (RT pulled) of heat aged (120°C) GBMS laps bonded with ethyl CA containing 0.1% w/w LTFB.
• Figure 10 shows the effect of LHFP on the fixture times of soda glass and GBMS bonded with ethyl CA.
• Figure 11 shows the short term effect of LTFB and CHP on heat ageing (RT pulled) of GBMS bonded with ACA formulations containing LTFB and/or CHP.
• Figure 12 shows the long term effects of LTFB and CHP on heat ageing (RT pulled) of GBMS bonded with ACA formulations containing LTFB and/or CHP.
• Figure 13 shows heat aged hot strength at 150°C of GBMS bonded with Allyl CA formulations containing 0.5% w/w LTFB and/or 1% w/w CHP.
• Figure 14 shows the effect of ZTFB on the heat aged (120°C) RT pulled bond strength of GBMS laps bonded with ethyl CA.
• Figure 15 shows the effect of LTFB which has been washed repeatedly with diethyl ether on the heat-aged shear strength (120°C, RT pulled) of GBMS bonded with ethyl CA
• Figure 16 shows the effect of LTFB on heat aged shear strength (120°C, RT pulled) of FIRELITE (glass ceramic) and stained glass (20% w/w lead oxide content) bonded with ethyl CA.
• the present invention provides a one-part cyanoacrylate adhesive composition including a cyanoacrylate monomer and a salt of a cation which is a hard Lewis acid with an anion of low nucleophilicity which does not initiate polymerization of the cyanoacrylate monomer.
• hard Lewis acid refers to those acids which are classified as “hard” or “borderline” in Chapter 5 (Table 5.4) p.213 of “Inorganic Chemistry” by Shriver, Atkins and Langford (second edition) published by Oxford University Press (1994).
• the definition of ' 'hard” Lewis aciid thus includes Li + , Na +
• the cation is desirably a metal cation.
• the metal cation is desirably a metal cation.
• the metal cation is desirably a metal cation.
• + + 2+ 2+ 2+ 2+ cation is selected from Li , K , Mg , Ni and Zn
• Particularly suitable cations are metal ions having an ionic radius of less than about 0.095 nm and especially less than 0.090 nm.
• a selected group of cations are Li , Mg and Zn .
• the anion may suitably be selected from
• the anion is desirably a fluorinated or chlorinated anion which releases a fluorine or chlorine anion and an acidic species e.g. on hydrolysis.
• a selected group of anions are fluorinated anions such as BF “ , PF- , SbF 6 or AsF " .
• compositions according to the invention have been found to have improved bonding performance as compared to compositions without the above-defined salts.
• Retarding the speed of cure is desirable in improving bond strength on high energy surfaces such as glass.
• lithium salts with the above selected anions have been found to stabilize cyanoacrylate (CA) compositions without substantial loss of activity apart from causing slower fixture on polar surfaces.
• CA cyanoacrylate
• On glass it is desirable to reduce the speed of bonding e.g. to a fixture time greater than 5 seconds.
• the presence of one of the above-noted salts which increases fixture time in the composition allows more time to position the components to be bonded, before bonding takes place.
• the slower cure allows time for accurate positioning of the glass substrates.
• metal such as GBMS (grit blasted mild steel)
• the addition of the above-noted salts has been shown to improve the heat ageing properties of ethyl CA compositions and to reduce bond weakening during thermal ageing of an allyl CA composition.
• Li + and Mg + and Zn cations are relatively small and have a high charge density.
• the ionic radii of some metal ions are listed below in nanometers (nm): Li Zn Ma K 0.068 0.074 0.082 0.097 0.133
• salts with larger cations such as tetrabutyl ammonium, sodium or potassium, are not as effective as those with smaller cations e.g. cations with an ionic radius less than 0.095 ⁇ m.
• Lithium is a hard Lewis acid in accordance with the above definition. It is believed that the above-noted salts undergo phase transfer adsorption onto polar surfaces. If adsorption/phase transfer is restricted by adding a chelating agent (such as a calixarene
• composition should therefore not contain a chelating agent which complexes with the cation species.
• compositions of the invention form a colourless bond with glass which remains optically clear even after heating. Previous CA compositions suffered from yellowing after heating.
• compositions of the invention contain the above-defined salt in amounts effective to improve bonding and/or thermal bonding performance which may be very small quantities, suitably not more than 6%, and more suitably not more than 1% by weight of the composition, and most suitably in the range 0.001% to 0.5%.
• the amount of the salt ⁇ iay also be determined with reference to the CA monomer so that the salt is present in an amount not more than 6% by weight of the monomer and more suitably not more than 1% by weight of the monomer and most suitably in the range 0.001% to 0.5%. Unless otherwise stated all percentages are calculated on a weight by weight basis.
• a selected group of salts for compositions of the invention are LHFP, LTFB, LHFA, MTFB and ZTFB
• Particularly suitable salt concentrations which may be based on the weight of the monomer or on the weight of the composition (% w/w) for glass bonding applications are:
• Particularly suitable salt concentrations which may be based on the weight of the monomer or on the weight of the composition (% w/w) for steel are:
• CA adhesive composition may contain an anionic polymerization inhibitor and/or free radical polymerization inhibitor in conventional amounts [see U.S. Patent No. 4,460,759 (Robins)].
• Cyanoacrylate compositions already including such inhibitors to which the salts of the invention may be added are sold by Loctite Corporation, Hartford CT, USA under the trade mark Quick-Tite and by Loctite (Ireland) Limited, Dublin 24, Ireland under the trade mark Super-Attak. The non-gel version of these products should be used.
• lithium or magnesium salts with fluorinated anions such as BF , PF , AsFj, SbFl do not destablize CA formulations. These ions undergo reversible hydrolysis with water yielding hydrofluoric acid e.g.
• the equilibrium constant for the reaction of pure water with BFl indicates that approximately half of the BFl anions undergo hydrolysis releasing HF.
• Polar substrates such as metal and most glasses are basic, and are coated in tightly bound water onolayers. While the present invention is not limited by any theory, it is considered that small cations and fluorinated anions should function as water-activated, surface-active, latent acid additives for CA polar substrate bonding applications. "Surface-active" in this context means that the latent acid binds to the substrate surface, resulting in much higher concentrations of acid at the adhesive/substrate interface than in the bulk bondline adhesive.
• the lithium, magnesium, or zinc cations could also function as acidic species by lessening the reactivity of surface base, owing to the ability of these ions to coordinate with basic species.
• bond strengths were measured in mPa by conventional methods using INSTRON apparatus. An average was taken of 3 results for each test. Unless otherwise stated, where experiments were performed on glass, 6mm soda glass was used. All concentrations given in the Examples are in % w/w based on the total weight of the monomer.
• cyanoacrylate formulations used in the Examples contain inhibitors in accordance with conventional practice in the art. Of a number of purification methods tested for lithium tetrafluoroborate repeated washing with diethyl ether was one of the simplest and more effective methods.
• lithium tetrafluoroborate salt used in bonding soda glass as detailed in the Examples below was purified by washing with diethyl ether. Except where otherwise stated the lithium tetrafluoroborate, used in bonding GBMS was used as supplied (Aldrich Chemical Company, Gilingha , Dorset SP8 4XT, England).
• the ionic radius of Mg is similar to that of Li + , and the intense electrostatic field associated with the magnesium ion ensures it has a high affinity for polar substrates.
• the thermal glass bonding performance of ethyl CA formulations containing magnesium tetrafluoroborate (MTFB) were comparable with equivalent LTFB formulations as shown in Fig 3.
• Fig. 4 The fixture times of soda glass laps bonded with ethyl CA formulations which were subjected to accelerated ageing at 55 C are illustrated in Fig. 4. Remarkably, the fixture times of the LTFB containing formulations were constant at 30 seconds even after eleven weeks ageing. In contrast, the fixture times of ethyl CA which did not contain LTFB gradually increased from ⁇ 3 seconds to 30 seconds after nine weeks of ageing.
• ECA formulations bonding GBMS show improved shear strength on heat ageing when LHFP is present in the formulation as shown in Fig.8.
• Fig. 9 shows the effect of added lithium-sequestering calixarene on the thermal performance of GBMS bonds made with ethyl CA formulations which contained LTFB.
• the calixarene completely deactivates the beneficial effect of the LTFB.
• the properties of calixarenes as ion-sequestering agents are well known.
• US patent No. ⁇ 1, 882, 49 of Harris describes calixarene derivatives which are useful for sequestration of transition metals.
• US patent No. 5,210,216, Harris et al. describes similar compounds. Chang et al . Chemistry Letters pages 477-478, 1984 also describes the properties of calixarene.
• the LTFB was recrystal 1 ized twice (from a 75% ethanol , 25% water solvent) prior to performing the above experiment in order to eliminate any possible effect from acidic impurities.
• Figure 10 shows the effects on the fixture times of varying concentrations of LHFP on ECA bonded soda glass and GBMS. Relatively small increases in the concentrations of LHFP show large increases in the fixture times on soda glass. Smaller increases in fixture time occur with GBMS.
• LTFB produces a small but significant increase in the thermal bonding performance of allyl CA formulations and allyl CA formulations containing CHP.
• the corresponding hot shear strengths of GBMS bonds at 150°C show small but significant increases in the heat aged performance of the formulation containing LTFB only.
• the bond formed with the formulation containing CHP only has relatively high initial hot strength.
• the bond formed with the formulation containing both CHP and LTFB shows high initial hot strength and significantly increased shear strengths on heat ageing.
• Nickel tetrafluoroborate and sodium tetrafluoroborate both supplied by Aldrich destabilized ethyl CA. No improvement in stability was obtained following single recrystall ization of the nickel salt or double recrystall ization of the sodium salt from hot solutions of the respective salts in 75% (w/w) ethanol/25% (w/w) water.
• This invention provides articles of manufacture, namely adhesive compositions.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Adhesives Or Adhesive Processes (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=11041241

Family Applications (1)

Country Status (7)

Families Citing this family (5)

Family Cites Families (4)

• 1997
  • 1997-08-15 EP EP97935732A patent/EP0918831A1/de not_active Withdrawn
  • 1997-08-15 WO PCT/IE1997/000059 patent/WO1998007801A1/en not_active Application Discontinuation
  • 1997-08-15 AU AU38616/97A patent/AU726418B2/en not_active Ceased
  • 1997-08-15 CA CA002263313A patent/CA2263313A1/en not_active Abandoned
  • 1997-08-15 JP JP10510550A patent/JP2000516289A/ja active Pending
  • 1997-08-15 KR KR1019997001261A patent/KR20000068165A/ko not_active Application Discontinuation
  • 1997-08-15 BR BR9711196A patent/BR9711196A/pt not_active Application Discontinuation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events