Primer for Cyanoacrylate Adhesive

US 20060278337Al (19) United States (12) Patent Application Publication (10) Pub. No.: US 2006/0278337 A1 Chikatsune et al. (43) Pub. Date: Dec. 14, 2006 (54) PRIMER FOR CYANOACRYLATE Publication Classification ADHESIVE (51) Int. Cl. (75) Inventors: Keizo Chikatsune, Osaka-shi (JP); C09J 5/04 (2006.01) Kazufumi Hamada, Kobe-shi (JP); C04B 37/00 (2006.01) Kazuo Kohara, Moriyarna-shi (JP) (52) U.S. Cl. .......................................... .. 156/316; 156/325 Correspondence Address: (57) ABSTRACT ARMSTRONG, KRATZ, QUINTOS, HANSON . . . & BROOKS’ LLP Some of ot-cyanoacrylate adhesive does not achieve practi- 1725 K STREET NW cal bond (adhesion) strength and any objective materils do SUITE 1000 ’ not have adhesion with the same. The inventor provides a W ASHINGTON, DC 20006 (US) primer which is not harmful against human body and shows when applied sufficient adhesion strength even on those (73) Assigneez ALTEC0 INC” 1baraki_Shi (JP) materials hard to have adhesion. Aprimer for cyanoacrylate adhesive characterized by comprising as an effective content (21) App]. No‘; 11/143,310 amphoteric compounds containing in molecules the follow- ing substances a and b: a: carboxyl group or sulfonic acid (22) Filed: Jun. 9, 2005 group, and b: amines. US 2006/0278337 A1 PRIMER FOR CYANOACRYLATE ADHESIVE BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a primer for a cyanoacrylate adhesive. [0003] 2. Prior Art [0004] Cyanoacrylate adhesives hitherto provided have been broadly and much put into practical use industrially or domestically for organic materials such as metal and plastic and for natural stuffs such as stone and wood thanks to quickness of hardening and variation of corresponding objects to undergo adhesion with the adhesive. [0005] However, the conventional cyanoacrylate adhe- sives are not almighty, i.e. some materials do almost not have adhesion with the conventional cyanoacrylate adhe- sives, or many materials are not given a predetermined level of adhesion strength with the conventional cyanoacrylate adhesives. To solve the problems, it would be ordinarily possible to provide a pre-treatment or apply a primer. However, in fact, there has been found no such pre-treatment carried out. And a primer is hitherto not employed for a metal surface or nylon. [0006] Moreover, in recent times, there exist various and many chemicals and substances that are argued of questions or doubts regarding safety or restrained from using practi- cally in relation to the environmental problems. Therefore, development of primers should meet many regulations and rules. In particular, the conventional primer was regarded as problematic in use for adhering in the manufacture of tools and devices for medical purpose. [0007] To overcome the above problems, the inventor has researched and studied minutely and developed a primer that shows an excellently high safety and largely improves adhesion strength of cyanoacrylate adhesives. SUMMARY OF THE INVENTION [0008] The present invention relates to a primer for cyanoacrylate adhesives characterized by containing amphoteric compounds as an effective content. DETAILED DESCRIPTION OF THE INVENTION [0009] Most of the conventional primer has the effective content in liquid state and is thereby applied on the assump- tion that it broadly extends over the whole surface subjected to adhesion. Transcending beyond the conventional concept, the inventor conceived such feature that crystalline sub- stances are adhered on the objective surface not all over the whole but as dotted or studded, in detail, microscopically quite sparsely, in such manner that a diluted solution dis- solved by solvent is applied and the solvent is then volatil- ized. [0010] It has been found such fact that the dotted crystal- line substances unexpectedly effectively function to provide high adhesion. The reason although not yet specified is so inferred that the polymer of adhesive hardens from the state of studded microcrystallines to grow quickly, and in the other region than that of the crystalline particles the adhesive Dec. 14, 2006 and the objective material are not separated but directly contact with each other, whereby enabling the whole surface to undergo adhesion very much quickly. [0011] The main content of the primer according to the present invention is amphoteric compounds, i.e., those including in molecules both of acid and amines, which is to become the foregoing microcrystallines. [0012] Acid referred to here may be carboxyl group (COOH) or sulfonic acid group (SO3H). [0013] Amines may employ primary amines, secondary amines or tertiary amines. [0014] A substances containing in molecules carboxyl group and primary amines is typically amino acid. The present invention started from the inventor’s discovery of the fact that amino acid effectively functions as a primer for cyanoacrylate adhesives. [0015] Amino acid may employ aspartic acid, glutamic acid, glutamine, cysteine, cystine, phenylalanine, threonine, thyrosin, serine, hydroxyproline, methionine, tryptophan, citrulline, isoleucine, valine, glycine, alanine, [3-alanine, histidine, lysine, leucine, arginine, etc. [0016] Those containing in molecules carboxyl group and secondary amines may be typically proline, which is one of essential amino acids and called separately cyclic amino acids. [0017] Next, a substance containing in molecules carboxyl group and tertiary amines may be nicotine acid or the like. [0018] Those containing in molecules sulfonic acid group and primary amines may be taurine, which is regarded as a kind of amino acids. Those containing in molecules sulfonic acid group and secondary amines may be N-methyltaurine. [0019] In the present invention, those acid groups and amines may exist in molecules plurally, for example, in the form of diarnine, or dicarboxylic acid, or the like. [0020] These amphoteric compounds may include ester with lower alcohol in the acid part. In this case, ester is suitably usable in acidic state. [0021] In formulation of the primer, by adding ethanol (EtOH) or isopropyl alcohol (IPA), the acidic region is locally esterified in a comparatively short time. [0022] The present invention dissolves the amphoteric compounds in solvent (as dispersed or emulsified, the same meaning hereunder) and mix other compositions as or when required, thereby providing the primer. The primer is applied or coated or sprayed so as to allow the amphoteric com- pounds to be uniformly adhered in a proper quantity. [0023] Dissolution concentration of the amphoteric com- pounds the main content of the present invention may be 0.0001-0.02 mol/100 g (the whole quantity), and preferably 0.001 -0.005 mol/100 g. A dilute solution is preferable for the purpose of avoiding that the amphoteric compounds (i.e., the primer) is applied thickly to hinder the adhesive from contacting with the objective material. [0024] A solvent for dissolving the amphoteric com- pounds is not particularly defined but may be preferably water or alcohol, in particular, water itself, alcohol itself or an aqueous solution of alcohol. Furthermore, organic solvent US 2006/0278337 A1 such as ketone, ester, saturated hydrocarbon or the like, or combination(s) or mixture(s) of those may be usable. Among them water is more safe while alcohol is more quickly dried and shows an excellent wetting on the surfaces of organic substances, metal plating. After considering all the factors, preferably is a thick aqueous solution such as ethanol, propanol or the like (concentration: 50-90 wt %). [0025] The foregoing saturated hydrocarbon may be cyclohexane, methylcyclohexane, cyclopentane, normal hexane, etc. Those may be used solely as above but may be preferably used by adding 5-30 wt % into an aqueous solution of alcohol. [0026] The rate of the above solvent in the whole of primer is preferably 90-95 wt % or more. [0027] The primer made of amphoteric compounds according to the present invention may be mixed with various contents other than the solvent, such as acid, alkali, furthermore, any other than these not preventing hardening such as perfume, pigment, hardening catalyst or the like. [0028] Acid and alkali are mixed into the invention to improve solubility and adhesion strength and may employ sodium hydroxide, potassium hydroxide, ammonium hydroxide, hydrochloric acid, sulfulic acid, acetic acid or the like. Quantity of mixture may be preferably identical in mol to that of corresponding groups (amino group, carboxyl group, etc) in the amphoteric compounds but not defined particularly. By adding those acid and alkali, pH is adjusted to enable selecting any optimum pH for the objective materials subjected to adhesion. [0029] In case that primer itself has higher pH (about pH 7.5-11.0), the primer generally quickly hardens. But, a comparatively low pH is suitable for metal surface or the like. The objective materials subjected to adhesion are each differently influenced with pH. Such influences with pH is able to be previously measured, and suitable values are found through try and error and used to adjust adhesion strength. [0030] One of characteristics of the present invention is that the foregoing amphoteric compounds are basically harmless and do not pollute environments. This is a high advantage in use for the medical purpose as foregoing as well as for other cases. Generally, harmful organic solvent does not readily dissolve. Thus, safety is ensured in this regard, too. [0031] Quantity of applying the primer may be enough to be sprayed once or applied once using a brush and may be adjustable by means of specific concentration. [0032] Cyanoacrylate adhesives in the present invention may be alkyl-ot-cyanoacrylate such as methyl-ot-cyanoacry- late, ethyl-ot-cyanoacrylate, butyl-ot-cyanoacrylate, or octyl- ot-cyanoacrylate, or cyclohexyl-ot-cyanoacrylate, methoxy- ot-cyanoacrylate, etc. PREFERABLE EMBODIMENTS [0033] Next, the present invention will be detailed with referring to specific example. [0034] Tensile shear/bond (adhesion) strength with and without using the primer according to the present invention with respect to various objective materials are compared to Dec. 14, 2006 research the effects. (Comparison with other primer than the present invention was tried but not made since primers for those objective materials are not commercially available and not known.) [0035] As cyanoacrylate adhesive, etyl-ot-cyanoacrylate (Altico Inc.: E50) was made use of. [0036] Experiments were carried out in such manner that primers (Primer Nos. 1-21 in Table 1) were applied by brush on an end part 12.5 mm width of two test pieces (100 mm>