Adhesive Composition

United States Patent [191 Katsumura et al. [54] ADHESIVE COMPOSITION [75] Inventors: Tasuo Katsumura; Tadashi Inamura, both of Hyogo; Eizo Kajigaki, Osaka, all of Japan Takeda Chemical Industries, Ltd., Osaka, Japan [73] Assignee: [21] Appl. No.: 496,692 [22] Filed: Mar. 21, 1990 [30] Foreign Application Priority Data Mar. 24, 1989 [JP] Japan .................................. .. 1-72740 [51] Int. Cl.5 ....................... .. C08L 33/14; COSF 4/52 [52] U.S. C1. .................................. .. 524/850; 526/196; 526/297 [58] Field of Search ............... .. 524/850; 526/196, 297 5,034,456 Jul. 23, 1991 [11] Patent Number: [45] Date of Patent: [56] References Cited U.S. PATENT DOCUMENTS 2,763,585 9/1956 Coover, Jr. et al. ............... .. 154/43 2,912,454 11/1959 McKeever .......... .. 260/465.4 3,692,752 9/1972 Setsuda et al. . . . . . . . . . . . . . .. 526/297 3,836,565 9/1974 Brinkman et al. 260/464 4,076,685 2/1978 Kogler .................... .. 524/850 4,581,313 4/1986 Minamizono et al. 430/145 Priman; Examiner——Joseph L. Schofer Assistant Examiner—R. H. Delmendo Attorney, Agent, or Firm——Wegner, Cantor, Mueller & Player [5 7] ABSTRACT An a-cyanoacrylate base adhesive composition com- prising 0.0001 to 0.5 part by weight of borofluoric acid on a 100% basis per 100 parts by weight of an a-cyanoa- crylate monomer, which composition has improved storage stability. 5 Claims, No Drawings 1 ADHESIVE COMPOSITION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive composi- tion. In particular, the present invention relates to an a-cyanoacrylate base adhesive composition having good storage stability. 2. Description of the Related Art Since an a—cyanoacrylate base adhesive is a reactive adhesive comprising an a-cyanoacrylate monomer, it tends to be cured in an adhesive container during stor- age because of radical or anionic polymerization of said monomer. Therefore, a polymerization inhibitor is added to the adhesive as a stabilizer to improve the storage stability of the adhesive. As the radical polymerization inhibitor for the a- cyanoacrylate monomer are used hydroquinone, hydro- quinone monomethyl ether, catechol, pyrogallol, bis- phenol A and the like. The polymerization inhibitor is added to the adhesive in an amount of 1 to 5000 ppm to inhibit the radical polymerization during room tempera- ture storage. The anionic polymerization is initiated with a small amount of moisture or a base such as an amine and ammonia. To prevent increase of viscosity and gelation due to anionic polymerization of the monomer are used S02, S03, SOCI3, SO1Cl2, HF, BF3, BF3-ether com- plexes, N02, paratholuenesulfonic acid, methanesul- fonic acid, propanesultone, phosphoric acid, sulfuric acid and the like. However, the addition of the anionic polymerization inhibitor increases the setting time of the adhesive and deteriorates instantaneous adhesivity. Since such inhibi- tors are in a gas state at ambient temperature, their handling and adjustment of their concentration in the adhesive are difficult. Some of them such as S03 and BF 3-ether complexes tend to fume and color the adhe- SIVC. SUMMARY OF THE INVENTION An object of the present invention is to provide a novel anionic polymerization inhibitor which is useful as a stabilizer for an a-cyanoacrylate base adhesive. Another object of the present invention is to provide an a-cyanoacrylate base adhesive composition which does not suffer from the drawbacks of the conventional a-cyanoacrylate base adhesives. Accordingly, the present invention provides an at- cyanoacrylate base adhesive composition comprising 0.0001 to 0.5 part by weight of borofluoric acid (HBF4) (as 100 %) per 100 parts by weight of an a-cyanoacry- late monomer. DETAILED DESCRIPTION OF THE INVENTION Specific examples of the a-cyanoacrylate monomer which is a main component of the adhesive composition are methyl a-cyanoacrylate, ethyl at-cyanoacrylate, propyl a-cyanoacrylate, allyl a-cyanoacrylate, butyl ct-cyanoacrylate, heptyl ct-cyanoacrylate, hexyl