Additives for Cyanoacrylate Adhesives

EP 0058187 B1 Europaisches Patenta mt 0’ European Patent Office Office européen des brevets 0058187 B1 @ Publication number: ® EUROPEAN PATENT SPEClFlCATION Date of publication of patent specification: 30.04.86 ® Int. CL“: C 09 J 3/ 14, C 08 L 35/O4 ® Application number: 81902382.1 ® Date of filing: 27.08.81 International application number: PCT/GB81/00170 International publication number: WO 82/00829 18.03.82 Gazette 82/08 ® ADDITIVES FOR CYANOACRYLATE ADHESIVES. ® Proprietor: LOCTITE CORPORATION 705 North Mountain Road Newington, Connecticut 06111 (US) Priority: 2s.os.so IE 1312/so ® Date of publication of application: 25.08.32 Bulletin 82/34 ® Inventor: HARRIS, Stephen John 10, Broadford Crescent Ballinteer @ Publication of the grant of the patent: Dublin 14 (IE) 30.04.86 Bulletin 86/18 Representative: Marchant, James Ian et al_ Elkington and Fife High Holborn House 52/54 High Holborn London WC1V 6SH (GB) Designated Contracting States: DE FR GB NL References cited: US-A-4 196 271 Patent Abstracts of Japan, vol. 2, nr. 144, November 30, 1978, page 3295C78 Patent Abstracts of Japan, vol. 1, nr. 120, October 12, 1977, page 2799C77 Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European patent convention). Courier Press, Leamington Spa, England. '15 20 25 30 35 40 45 50 55 60 65 0 058 187 Description This invention relates to adhesive compositions containing as the major polymerisable constituent one or more esters of 2-Cyanoacrylic acid, such as Ethyl 2-cyanoacrylate. The improvement of cyanoacrylate adhesive compositions, particularly as regards the stability of the adhesive bonds formed therewith under exposure to high temperatures and moist conditions, is an area of wide-ranging and energetic research activity. The present invention adds one compound to the list of additive substances known to improve these compositions in the said respect. There follows a short outline of the closest prior art known to us. 1. Federal German Patent No. 24 29 070 (1975: Bostik GmbH) discloses the use of ltaconic anhydride as an additive in alkyl and allyl cyanoacrylate compositions to impart improved heat resistance to the adhesive bonds formed. 2. Patent No. 34874 (1972: Loctite (Ireland Limited) and its U.S. equivalent Patent No. 3832 334 disclose the use of Maleic anhydride and derivatives thereof as additives in alkyl cyanoacrylate compositions to impart improved heat resistance to the adhesive bonds formed. 3. Japanese Patent No. 78 110 635 (1978: Toa Gosei) discloses the use of hydroxyalkyl and hydroxylhaloalkyl esters of c1,B-unsaturated carboxylic acids as additives in alkyl cyanoacrylate compositions to impart improved heat resistance to the adhesive bonds formed. 4. Japanese Patent No. 77 80 336 (1977: Toa Gosei) discloses the use of dicarboxylic acids and their anhydrides as additives in ethyl cyanoacrylate compositions to impart improved impact resistance to the adhesive bonds formed. 5. Japanese Patent No. 77 78 933 ( 1977: Toa Gosei) discloses the use of aromatic polycarboxylic acids and their anhydrides as additives in Ethyl cyanoacrylate compositions to impart improved impact resistance to the adhesive bonds formed. 6. U.S. Patent No. 4196271 (1980: Toa Gosei) discloses the use of substituted and unsubstituted aliphatic carboxylic acids having three or more free carboxyl groups, anhydrides thereof, partial esters thereof having at least three free carboxyls, and aromatic polycarboxylic acids having three or more free carboxyl groups as additives in cyanoacrylate compositions to improve impact resistance of the adhesive bonds formed. The above references also provide a good indication of progress up to their respective dates in the improvement of heat and impact resistance in adhesive bonds formed from alkyl cyanoacrylate compositions by the use of additives. I It will be noted that various organic anhydrides have been proposed for the general purpose of the present invention. However, none of the prior proposals known to us, either in the art cited above or elsewhere, embraces the use of Phthalic anhydride. Some of the prior art goes so far as to exclude Phthalic anhydride specifically, indicating perhaps some misconception or prejudice prevalent in the art about the suitability of this compound. Hence the present invention may be said to rest on the surprising discovery of a hitherto unsuspected utility of Phthalic anhydride. The invention provides an adhesive composition containing as the major polymerisable constituent at least one ester of 2-Cyanoacrylic acid, characterised in that the composition additionally comprises a proportion of Phthalic anhydride effective for favourably influencing the strength and/or durability of adhesive bonds formed from said composition, under exposure to moisture or elevated temperature. An effective proportion of Phthalic anhydride for the above recited purpose is selected from the range 0.1% to 5.0% by weight of the composition. A preferred proportion is selected from the range 0.3% to 0.7% by weight, a specially preferred proportion being about 0.5% by weight of the composition. It has been found that an Ethyl cyanoacylate solution containing 0.5% by weight Phthalic anhydride yields adhesive bonds having a heat resistance superior to that of bonds made with an otherwise identical composition containing 1.0% by weight Maleic anhydride in place of the Phthalic anhydride. Some of the bonds were formed between grit blasted steel lapshears, others between grit blasted aluminium lapshears. The bonds made with the invented composition were also found to possess significantly improved moisture resistance as compared with bonds made with the Maleic anhydride composition. It may be remarked that the Maleic anhydride composition is itself known to outperform a composition containing Ethyl cyanoacrylate alone, in both of the above mentioned respects. The invention will be appreciated in greater detail from the following examples of specific and preferred embodiments thereof. Each test result given in these examples is the mean of ten determinations. Example 1 Grit-blasted stainless steel strips 2.54 cm wide by circa 1 mm thick were prepared, aligned face to face, and adhesively secured together on an overlap length of 1.27 cm to give a bonded area of 3.22 cm‘°‘. The bonds were allowed to cure at room temperature for 3 days, following which about one third of their number were tested. Half of the remaining number were thereupon subjected to ageing at 120°C for 48 .hours and tested. The other half of said remainder (one third of the original number of bonds) were subjected to ageing at 40°C in conditions of 95% relative humidity for 7 days, after which they too were tested. 10 75 20 25 30 -35 40 45 50 55 60 65 0 058 1 87 The tests were destructive measurements of the tensile shear strength of the adhesive bonds, the results being expressed in kg/cmz, and (in parentheses) as a percentage of that initial strength which was determined after 3 days at room temperature. The procedure was carried out separately using three different adhesive compositions one of which was a composition of the invention, the other two being included for comparison. The polymerisable monomer of the composition in every case was Ethyl 2-cyanoacrylate. The results are set out in Table 1. TABLE 1 Tensile shear strength kg/cmz 3 days +48 hours +7 days g Additive RT 120°C 40°C 95% RH 0.5% Phthalic anhydride 155 109 (70%) 130 (84%) 1% Maleic anhydride 178 110 (62%) 85 (48%) None 158 59 (37%)) 88 (56%) Example 2 The procedure of Example 1 was repeated, but using grit—b|asted aluminium strips as the adhesive substrate in place of stainless steel. The results are set out in Table 2. TABLE 2 Tensile shear strength kg/cmz 3 days +48 hours +7 days Additive RT 120°C 40°C 95% RH 0.5% Phthalic anhydride 95 69 (73%) 63 (66%) 1% Maleic anhydride 159 51 (32%) 57 (36%) None 123 28 (23%) . 61 (50%) The utility of Phthalic anhydride is apparent from a composition of its results with those where no additive was used. its superiority to Maleic anhydride is likewise evident, though less pronounced in the case of stainless steel lapshears than in those of aluminium. The adhesive compositions of the invention are found, additionally, to exhibit excellent stability in the unpolymerised state when stored for periods of three months or more. Thus they can be presented as one—part cyanoacrylic compositions without the known disadvantage associated with the use of Maleic anhydride. Maleic anhydride must, as a rule, be mixed into the Ethyl cyanoacrylate just prior to use. Storage of 1% Maleic anhydride in Ethyl cyanoacrylate leads to loss of the adhesive properties of the composition after about the third month, due to overstabilisation by Maleic acid resulting from in situ hydrolysis of the anhydride. Claims . 1. An adhesive composition containing as the major polymerisable constituent at least one ester of 2-Cyanoacrylic acid, characterised in that the composition additionally comprises a proportion of Phthalic anhydride effective for favourably influencing the strength and/or durability of adhesive bonds formed from said composition, under exposure to moisture or elevated temperature. 2. A composition according to claim 1 characterised in that the proportion of Phthalic anhydride is selected from the range 0.1% to 5.0% by weight of the composition. 3. A composition according to claim 2 characterised in that the range is 0.3% to 0.7%. 4. A composition according to claim 3, characterised in that the proportion is about 0.5% by weight of the composition. 5. A composition according to one of claims 1-4 characterised in that the ester is Ethyl 2-cyanoacrylate. 6. A bonded assembly characterised by comprising at least two members bonded by a film of an in situ cured adhesive composition according to one of claims 1-5. 3 0 058 187 7. A method of preparing a bonded assembly of at least two members which method is characterised by (a) applying to at least one of the members a film of an adhesive composition according to one of claims 1-5; and _ 5 (b) placing the members in an abutting relationship across the film for a sufficient period of time to allow the adhesive composition to cure. 8. A bonded assembly characterised in that it was prepared by a method according to claim 7. 9. Use of Phthalic anhydride for favourably influencing the properties of adhesive bonds made with a composition containing at least one ester of 2-Cyanoacrylic acid in respect of the strength and/or durability 70 of said bonds under exposure to moisture or elevated temperature. Patentanspriiche 1. Eine Klebstoffzusammensetzung, enthaltend als polymerisierbaren Hauptbestandteil mindestens 15 einen Ester von 2-Cyanoacrylséiure dadurch gekennzeichnet, dais die Zusammensetzung aufserdem einen Anteil an Phthalsaure-anhydride enthalt, der wirksam zur gijnstigen Beeinflussung der Starke und/oder Dauerhaftigkeit der aus der Zusammensetzung gebildeten Klebebindungen, wenn sie Feuchtigkeit oder erhohter Temperatur ausgesetzt werden, ist. 2. Eine Zusammensetzung nach Anspruch 1, dadurch gekennzeichnet, dal3 der Anteil an Phthalsaure- 20 anhydrid im Bereich von 0,1 bis 5,0 Gew.-% der Zusammensetzung gewéihlt wird. ' F 3. Eine Zusammensetzung nach Anspruch 2, dadurch gekennzeichnet, clal3 der Bereich 0,3% bis 0,7% ist. 4. Eine Zusammensetzung nach Anspruch 3, dadurch gekennzeichnet, dal3 der Anteil etwa 0,5 Gew.-% der Zusammensetzung ist. 25 5. Eine Zusammensetzung nach einem der Ansprtiche 1-4, dadurch gekennzeichnet, dais der Ester Ethyl-2-cyanoacrylat ist. 6. Eine verbundene Anordnung, dadurch gekennzeichnet, dal3 sie mindestens 2 Teile umfalst, die durch einen Film aus einer in situ gehéirteten Klebstoffzusammensetzung nach einem der Ansprtliche 1-5, verbunden slnd. ‘ 30 7. Ein Verfahren zur Herstellung einer verbundenen Anordnung aus mindestens 2 Teilen, wobei das Verfahren gekennzeichnet ist durch (a) den Auftrag auf mindestens eines der Teile, von einem Film aus einer Klebstoffzusammensetzung nach einem der Anspriiche 1-5; und (b) das in Beriihrung bringen der Teile iiber den Film, wahrend eines ausreichenden Zeitraumes, um 35 die Hértung der Klebstoffzusammensetzung zu ermoglichen. 8. Eine verbundene Anordnung, dadurch gekennzeichnet, dal3 sie nach einer Methode nach Anspruch 7 hergestellt wurde. 9. Ven/vendung von Phthalsaure-anhydrid zur giinstigen Beeinflussung der Eigenschaften von Klebstoffbindungen, die mit einer Zusammensetzung hergestellt werden, die mindestens einen Ester von 40 2-Cyanoacrylséure enthéilt, bezuglich der Festigkeit und/oder Dauerhaftigkeit der Bindungen bei Ein- wirkuhg von Feuchtigkeit oder erhéihter Temperatur. Revendications 45 1. Une composition adhésive contenant, comme constituant polymérisable principal, au moins un ester de l’aci'de 2-cyanoacrylique, caractérisée en ce que la composition comprend, en outre, une proportion d'anhydride phtalique efficace pour influencer favorablement la résistance mécanique et/ou la durabilité de liaisons adhésives formées a partir de cette composition, sous exposition a de l’humidité ou a une température élevée. 50 2. Une composition selon la revendication 1, caractérisée en ce que la proportion d'anhydride phtalique est choisie dans la gamme de 0,1% 2'3 5% du poids de la composition. 3. Une composition selon la revendication 2, caractérisée en ce que la gamme va de 0,3% a 0,7%. 4. Une composition selon la revendication 3, caractérisée en ce que la proportion est d’environ 0,5% du poids de la composition. 55 5. Une composition selon l’une quelconque des revendications 1 a 4, caractérisée en ce que l’ester est le 2-cyanoacrylate d’éthy|e. 6. Un assemblage collé, caractérisé en ce qu’il comprend au moins deux éléments collés par une pellicule d’une composition adhésive, selon l’une des revendications ‘l a 5, durcie in situ. 7. Un procédé de preparation d’un assemblage collé d'au moins deux éléments, procédé caractérisé en 60 ce que (a) on applique 51 au moins |'un des éléments une pellicule d’une composition adhésive selon l’une des revendications 1 a 5; et (b) on place les éléments en aboutement de part et d’autre de la pellicule pendant un laps de temps suffisant pour permettre a la composition adhesive de durcir. 65 8. Un assemblage collé, caractérisé en ce qu’il a été préparé par un procédé selon la revendication 7. 4 0 058 1 87 9. L’utiIisation de l’anhydride phtalique pour influencer favorablement les propriétés de liaisons adhésives réalisées avec une composition contenant au moins un ester de l’acide 2-cyanoacrylique eu égard é la résistance mécanique et/ou :31 la durabilité de ces liaisons sous exposition é de Vhumidité ou é une température élevée. 70 15 20 25 30 35 40 45 50 55 50 65