Alpha-cyanoacrylate and adhesive composition

United States Patent [19] Mikuni et al. Hllll||||l|l||Il|||||||||||l|||||||||||||||||||ll||lll||llllllllllllll|||| US005l75337A [11] Patent Number: [45] Date of Patent: 5,175,337 Dec. 29, 1992 [54] a-CYANOACRYLATE AND ADHESIVE COMPOSITION [75] Inventors: HiroyukiMikuni, Sagamihara; Toshiyuki Chikusa, Hachioji, both of Japan [73] Assignee: Three Bond Co., Ltd., Tokyo, Japan [21] App]. No.: 732,457 [22] Filed: Jul. 18, 1991 [30] Foreign Application Priority Data _ Aug. 7, 1990 [JP] Japan ................................ .. 2-207679 [51] Int. Cl.5 .......................................... .. C07C 255/07 [52] U.S. Cl. .................................... .. 558/443; 428/43; 428/223; 428/463; 428/522; 526/298 [58] Field of Search ....................................... .. 558/443 [56] References Cited U.S. PATENT DOCUMENTS 4,297,160 10/1981 Kurayama et a]. ............... .. 558/443 Primary ExamI’ner—Johann Richter Attorney, Agent, or Firm—Scully, Scott, Murphy & Presser [57] ABSTRACT A novel neopentyl a-cyanoacrylate is provided. It has superior adhesive properties even at high temperatures and whitening-preventing property. 1 Claim, No Drawings ' 5,175,337 1 a-CYANOACRYLATE AND ADHESIVE COMPOSITION BACKGROUND OF THE INVENTION The present invention relates to a novel a-cyanoacry- late and a cyanoacrylate-based adhesive composition containing same. a-Cyanoacrylates such as methyl a-cyanoacrylate and ethyl a-cyanoacrylate are polymerized and cured rapidly by the action of a small amount of water present on the surface of a material to be bonded and afford an adhesive force of an extremely high strength, so are widely used as room-temperature one-pack type instan- taneous adhesives for the bonding of metals, plastics, rubber, wood and the like. As a-cyanoacrylate there are known propyl a- cyanoacrylate, allyl a-cyanoacrylate, propargyl CL- cyanoacrylate, 2,2,2-trifluoroethyl a-cyanoacrylate, 2,2,3,3-tetrafluoropropyl a-cyanoacrylate, 2-methox- yethyl a-cyanoacrylate, 2-ethoxyethyl a-cyanoacrylate and the like in addition to the above mentioned methyl and ethyl a-cyanoacrylates. Generally, in the case where an a-cyanoacrylate is used as an adhesive, a portion thereof voltilizes and is polymerized by water contained in the air and adheres as white powder to the surrounding portion of a bonded part (whitening phenomenon), thus impairing the ap- pearance of the bonded material. When used in the assembly of electric and electronic parts, the volatilized monomer contaminates a contact portion and causes defective contact, or cures in a moving part, thereby causing malfunction. Moreover, the thermal stability of a cured product is not sufficient and the bonding strength is reduced rapidly over 100° C. It is known that a-cyanoacrylates having an unsaturated bond in the ester portion have improved thermal stability. In this case the cured or adhered portion is heat treated at an appropriate temperature (lO0° C.-150° C.) in order to improve the thermal stability. However, the adhesive properties at a high temperature are not improved. It is the object of the present invention to overcome the above mentioned drawbacks of the prior art. More concretely, it is the object of the present invention to provide a novel compound having superior adhesive properties as an instantaneous adhesive and superior in whitening-preventing property and thermal stability including high temperature adhesive properties. SUMMARY OF THE INVENTION The present invention resides in a novel neopentyl a-cyanoacrylate having the chemical structural for- mula: CN / CH2=C CH3 \ I CO2CH2(|:—CH3 CH3 and an adhesive containing the above compound as an essential component. DETAILED DESCRIPTION OF THE INVENTION The novel compound, neopentyl a-cyanoacrylate exhibits excellent instantaneous adhesive properties. It has a melting point of 40° C. and is a solid at a room 5 10 15 20 25 30 35 40 45 50 55 65 2 temperature It can be used itself as a hot-melt type instantaneous adhesive and also used as a liquid instanta- neous adhesive in admixture of conventional one or more cyanoacrylates in the same mananer as conven- tional instantaneous adhesives. The instantaneous adhe- sive containing neopentyl a-cyanoacrylate as an essen- tial component does not induce the whitening phenome- non and is superior in thermal stability, especially in high temperature-bonding strength. Neopentyl a-cyanoacrylate may be used alone or in combination with conventional one or more a-cyanoa- crylates. Such conventional a-cyanoacrylates are those repre- sented by the following general formula: CN / CH2=C c--o-R ll 0 wherein R is a hydrocarbon group such as alkyl, alke- nyl, or alkynyl, or an alkoxy hyrocarbon group such as alkoxyalkyl. Examples are methyl a-cyanocrylate, ethyl a-cyanoacrylate, isopropyl a-cyanoacrylate, those wherein R is alkoxyalkyl, e.g. 2-methoxyethyl a-cyanoacrylate and 2-ethoxyethyl a-cyanoacrylate, those wherein R is alkenyl, e.g. allyl a-cyanoacrylate, and those wherein R is alkynyl, e.g. propargyl a- cyanoacrylate. When using conventional cyanoacrylates in combina- tion with neopentyl a-cyanoacrylate, the latter is pref- erably in an amount of 85 wt% or less, more preferably 5 to 85 wt% based on the weight of adhesive compo- nents. If the amount of neopentyl a-cyanoacrylate is more than 85 wt%, the composition becomes a solid at a room temperature (i.e. 20° C.). Neopentyl a-cyanoacrylate of the present invention may be prepared by the following reactions. Neopentyl a-cyanoacetate having the following structural formula: i”-‘ NCCH3CO3CH2$—CH3 CH3 is prepared and then it is reacted with formaldehyde or paraformaldehyde in the presence of a basic catalyst to produce a condensation polymer, and then the conden- sation polymer thus produced is heat-depolymerized or thermally decomposed to produce nelpentyl a-cyanoa- crylate. Neopentyl a-cyanoacrylate thus obtained is a solid at a room temperature but it is desirable to add thereto a stabilizer in order to store it more stably. Examples of such stabilizer include, as anionic polymerization inhibi- tors, fulfurous acid (S02), sultone compounds, organic sulfonic acids, mercaptans, trifluoroacetic acid, and fluoroboric acid, and as radical polymerization inhibi- tors, quinones, catechol, pyrogallol, and 2,6-di-t-butyl- phenol. The amount of these stabilizers differs depend- ing on the respective inhibiting abilities, but is prefera- bly in the range of l to 10,000 ppm, more preferably 10 to 1,000 ppm, relative to the monomer. 5,175,337 3 The following examples are given to illustrate the present invention in more detail. The “part” and “%" in the following description are all by weight. EXAMPLE 1 5 Preparation of Neopentyl a—Cyanoacetate 51 g (0.6 mole) of cyanoacetic acid, 74 g (0.84 mole) of neopentyl alcohol, 1 g of sulfuric acid and 100 g of toluene were reacted under reflux and water produced 10 was removed by azeotropic distillation. Thereafter, the mixture thus produced was cooled to a room tempera- ture and filtered to remove insoluble matter. The filtrate was washed with water and dried overnight with 15 magensium sulfate. Then, the desiccant was filtered off and the solvent was removed under a reduced pressure, followed by vacuum distillation to afford 87.1 g of neo- tyl a-cyanoacrylate (b.p. 79°—81° C./ 3 mmHg, yield %). 1 R (neat)cm'l: 2262, 1751 60 MHZ ‘H-NMR (CDCI3/TMS) 8(ppm): 3.87 (s, 2 H), 3.46 (s, 2 H), 0.97 (s, 9 H) 90 MHz 13C-NMR (CDC13) 6(ppm): 162.91, 113.06, 25 75.41. 31.03, 25.86, 24.30 20 Preparation of Neopentyl a-Cyanoacrylate 46.5 (0.3 mole) of neopentyl a-cyanoacetate, 8.1 g (0.27 mole) of paraformaldehyde, 140 g of toluene and 30 46.5 mg of triethylenediamine were reacted together under reflux and water was removed by azeotropic distillation. Then, 23.5 g of dioctyl phthalate, 0.465 g of hydroquinone and 0.93 g of phosphorus pentoxide were 35 added and depolymerization allowed to take place at 150°—210" C. under a reduced pressure to afford 21.65 g of crude neopentyl a-cyanoacrylate. Redistillation thereof afforded (8.3 g of neopentyl a-cyanoacrylate (b.p. 65°—67° C./2 mmHg, m.p. 40°—41° C., yield 36%). 60 MHz ‘H-NMR (CDCI3/TMS) 5(ppm): 7.01 (s, 1 H), 6.61 (s, 1 H), 3.95 (s. 2 H) 1.20 (s, 9 H) 90 MHz 13C-NMR (CDCI3) 5(ppm): 160.14, 142.78, 116.44, 114.08, 75.46, 31.22, 25.95 EXAMPLE 2 Adhesives were prepared by mixing neopentyl a- cyanoacrylate (NPCA) and ethyl a-cyanoacrylate (ECA) as a conventional a-cyanoacrylate in such pro- portions as shown Table 1 below and then incorporat- ing therein 20 ppm of BF3. ethyl ether complex and 1,000 ppm of hydroquinone. Their adhesive properties are as set forth in Table 1. TABLE 1 Adhesive Propgrties (iron/iron) Tensile Shear Hot Tensile Strength Shear Strength (kgf/cmz) (kgr/cinl) 7o 5 40 45 50 55 Mixing Ratio (parts) NPCA/ECA 1/ 100 (Comparative example) 20/80 Whitening 60 Whitened slightly whitened slightly whitened not whitened 65 40/60 60/40 4 TABLE l-continued Adhesive Properties (iron/iron) Mixing Ratio Tensile Shear Hot Tensile (parts) Strength Shear Strength NPCA/ECA (kgi/cm?) (kgf/cm2_) Whitening 80/20 124 45 not whitened 100/0 130 . 45 not whitened EXAMPLE 3 Adhesives were prepared by mixing neopentyl a- cyanoacrylate (NPCA) and allyl a-cyanoacrylate (ACA) as a conventional a-cyanoacrylate in such pro- portions as shown in Table 2 below and then incorpo- rating therein 20 ppm of BF3.ethyl ether complex and 1,000 ppm of hydroquinone. Their adhesive properties are as set forth in Table 2. TABLE 2 Adhesive Properties (iron/iron) - Mixing Ratio Tensile Shear Hot Tensile (parts) Strength Shear Strength NPCA/ACA (ltgf/cmz) (kgf/cmz) Whitening 0/100 ' 100 5 Whitened (Comparative example) 20/80 110 12 slightly whitened 40/60 113 23 slightly whitened 60/40 129 45 not whitened 80/20 130 45 not whitened 100/0 130 45 not whitened EXAMPLE 4 Adhesives were prepared by mixing neopentyl ot- cyanoacrylate (NPCA) and 2-ethoxyethyl a-cyanoa- crylate (EECA) as a conventional a-cyanoacrylate in such proportions as shown in Table 3 below and then incorporating therein 20 ppm of BF3.ethyl ether com- plex and l,O()O ppm of hydroquinone. Their adhesive properties are as set forth in Table 3. TABLE 3 Adhesive Properties (iron/iron) Mixing Ratio Tensile Shear Hot Tensile (pans) Strength Shear Strength NPCA/EECA (kgf/cmz) (kgf/cmz) Whitening 0/100 74 5 slightly (Comparative whitened example) 20/so so 6 slightly whitened 40/60 82 8 not whitened 60/40 116 28 not whitened 80/20 125 45 not whitened 100/0 130 45 not whitened Comparative Example The adhesive properties of neopentyl a-cyanoacry- late were compared with those of n-amyl a-cyanoacry- late (n-AmCA) and iso-amyl a-cyanoacrylate (i- AmCA). The results are as set forth in Table 4. 5,175,337 5 6 TABLE 4 Adhesive Properties (iron/iron) Tensile Hot Tensile Chemical Shear Strength Shear Strength Cyanoacrylate Structure (kgf/cmz) (kgf/cmz) NPCA CN 130 45 / CH2=C CH3 \ I CO2CH2(|I—CI-I3 CH3 n-AmCA CN 23 0 / CH2=C \ . C02CsHn « i-AmCA CN 68 0 / . CH2=C CH3 \ I CO2CH2CH3(|IH CH3 Testing Method 25 Tensile Shear Strength Measured at 25° C. after aging 24 hours at 43-_*-1° C., 60i2% RH, according to JIS K6861. Hot Tensile Shear Strength 30 Measureds at 150° C.>