Cyanoacrylate Adhesive Composition

United States Patent [19] Takahashi et al. [54] [75] [73] [21] [22] [86] [37] [30] Nov. 9, 1992 [51] [52] [53] [56] CYANOCRYLATE ADHESIVE COMPOSITION Inventors: Shin Takahashi; Asako Kaai; Toshio Okuyama, all of Nagoya, Japan Assignee: Toagosei Co., Ltd., Tokyo, Japan Appl. No.: 416,881 PCT Filed: Nov. 9, 1993 PCT No.: PCT/JP93/01619 § 371 Date: Apr. 20, 1995 § l02(e) Date: Apr. 20, 1995 PCT Pub. No.: W094/11454 PCT Pub. Date: May 26, 1994 Foreign Application Priority Data [JP] Japan Int. Cl.6 ........................... .. US. Cl. .................... .. References Cited U.S. PATENT DOCUMENTS 3,551,311 12/1970 Nass et al. ............................ .. 428/458 ...... .. 4-323638 C08F 220/50 526/298; 428/520 Field of Search ............................................. .. 526/298 H|||||||||||||ll|||||||l|||I|||lll|||||||Illlllllll||||||I|||I|||I|||||||l US005536799A Patent Number: [45] Date of Patent: [11] 5,536,799 Jul. 16, 1996 3,940,362 2/1976 Overhults .............................. .. 523/116 5,367,002 11/1994 Huang et al. ......................... .. 523/116 FOREIGN PATENT DOCUMENTS 51-5391 7/1976 Japan . 63—128089 5/1988 Japan . 5695966 8/1991 Japan . Primary Examiner——-Mark Nagumo Attomey, Agent, or Firm—-Cushman Darby & Cushman [57] ABSTRACT A cyanoacrylate adhesive composition, which contains esters in which an alcohol residue thereof includes a dipen- taerythritol residue and an acid residue thereof is an acrylic or methacrylic acid residue, and which composition is improved in adhesion performance under high temperature and humid conditions, namely moisture and thermal resis- tance. The cyanoacrylate adhesive composition according to the present invention has excellent moisture and thermal resistance and thus is more widely usable than conventional ones in various industries, medical field, and leisure activity as well as household application and pupils’ stationary. 17 Claims, No Drawings 5,536,799 1 CYANOCRYLATE ADHESIVE CONIPOSITION TECHNICAL FIELD The present invention relates to a cyanoacrylate adhesive composition which is improved in adhesion function under conditions of high temperature and high humidity, namely resistance to heat and moisture. It is utilized widely in the adhesive industry and various industries using adhesives. BACKGROUND ART Cyanoacrylate adhesives, which contain 2-cyanoacrylate as a major component, have been favorably used as an instantaneous adhesive in wide variety of industries, medical field, leisure activity and household since 2-cyanoacrylate as the major component has the property of easily polymeriz- ing anionically in the presence of a trace amount of moisture and basic substances to quickly cure. While cyanoacrylate adhesives have excellent moisture and thermal resistance on adherends of rigid PVC, ABS or the like, they are poor in moisture and thermal resistance upon application to materials of nitrogen-containing com- pounds or sulfur-containing compounds such as chloroprene rubber, EPDM and other synthetic rubbers and Bakelite. A reason for the poor moisture and thermal resistance in adhesion of cyanoacrylate adhesives to chloroprene rubber, EPDM and other synthetic rubbers and to Bakelite would be that humidity and/or heat promote the nitrogen-containing compounds or sulfur-containing compounds to bleed from these materials and accumulate on the adhesion interface resulting in reduction of adhesion strength and that the bled compounds promote decomposition of cyanoacrylate poly- mers. The moisture and thermal resistance of the adhesives is further deteriorated when they are used to bond synthetic rubbers such as chloroprene rubber and EPDM in a state where internal residual stress exists. The reason is understood as follows: Hardened bodies of cyanoacrylate adhesives are stiff and are poor in a function of relaxing the intemal stress. Thus, it is considered that the effect of stress on adhesion interface and adhesion layer becomes significant, and as a result, deterioration of adhesion caused by humidity and/or tem- perature is promoted. Because of these reasons, urethane adhesives, epoxy adhesives, acryl adhesives and the like have been used in the industry for adhesion to sites where durability is required, while hot melt adhesives, pressure-sensitive adhesives and the like have been used for adhesion to sites where flexibility is required. However, urethane adhesives, epoxy adhesives, acryl adhesives and the like have disadvantages that they are “poor in operability due to requirements of blending of two packages or primer pretreatment of the surfaces to be adhered” and “poor in productivity due to slow adhesion rate.” On the other hand, hot melt adhesives and pressure- sensitive adhesives have a disadvantage that they are “poor in durability.” In the industry, thus there is a strong demand for development of an adhesive that is excellent in durability and brings about improvement in operability and produc- tivity. 10 20 25 30 35 40 45 50 55 60 65 2 Cyanoacrylate adhesives, which are characterized by single package instantaneous adhesion, may bring about the above-mentioned improvement in operability and produc- tivity, however are poor in durability and flexibility (stress relaxation) as already explained. For the purpose of providing flexibility with cyanoacry- late adhesives, a known technology is to blend a phthalate, a sebacate, and a saturated copolymer polyester described in JP-A-63-284279. However, these softening materials adversely aifect mois- ture and thermal resistance since they are present in cyanoacrylate polymers just in dispersed state. JP-A-58- 1 85 666 is another known technology for provid- ing flexibility, which discloses blending a C1-C4 alkyl (meth)acrylate or a C1-C4 alkoxyalkyl (meth)acrylate. These (meth)acrylates not only exist in cyanoacrylate poly- mers in dispersed state but also have a possibility of improv- ing durability by radical polymerization at elevated tem- perature. In the adhesion to chloroprene rubber which contains nitrogen-containing compounds or sulfur-containing com- pounds, however, the compositions blended with the C1-C4 alkyl (meth)acrylate or the C1-C4 alkoxyalkyl (meth)acry- late described in JP~A-58-185666 can not still satisfy the moisture and thermal resistance. Under such situations, there is a strong need for devel- oping an instantaneous adhesive-that is excellent in moisture and thermal resistance even on materials said to be difiicult to bond, that is, materials that contain nitrogen-containing compounds or sulfur-containing compounds, for example, synthetic rubbers like chloroprene rubber and EPDM, and Bakelite. The present invention is to provide a cyanoacrylate instantaneous adhesive that has excellent moisture and ther- mal resistance when applied for adhesion particularly to adherends that contain nitrogen-containing compounds or sulfur-containing compounds, for example, synthetic rub- bers like chloroprene rubber and EPDM, and Bakelite. DISCLOSURE OF INVENTION As a result of intensive studies for solving the above mentioned problems, the present inventors have found that a composition obtained by adding a specific acrylate or methacrylate to 2-cyanoacrylate, can be an adhesive com- position exhibiting excellent moisture and thermal resis- tance, and have completed the present invention. The present invention relates to a cyanoacrylate adhesive composition characterized in that it comprises an ester the alcohol residue of which contains a dipentaerythritol residue and the acid residue of which is an acrylic or methacrylic acid residue. ' Now, the adhesive composition according to the present invention is explained. As 2-cyanoacrylate, which is the main component exhib- iting adhesion function in the present composition, may be widely adopted what has been used as a main component of cyanoacrylate instantaneous adhesives; examples of the 2-cyanoacrylate are listed below: That is to say, 2-cyanoacrylic acid esters of methyl, ethyl, n-propyl, i-propyl, propargyl, n-butyl, i-butyl, n-pentyl, n-hexyl, 2-ethylhexyl , n-octyl, n-nonyl, oxononyl, n-decyl, n-dodecyl, allyl, ethynyl, 2-butenyl, cyclohexyl, phenyl, phenethyl, tetrahydrofurfuryl-, chloroethyl, 2,2,2-trifluoroet- hyl, hexafluoroisopropyl, methoxyethyl, ethoxyethyl, pro- 5,536,799 3 poxyethyl, isopropoxyethyl, butoxyethyl, hexyloxyethyl, 2-ethyl hexyloxyethyl, butoxyethoxyethyl, hexyloxyethoxy- ethyl, 2-ethyl hexyloxyethoxyethyl, methoxypropyl, meth- oxypropoxypropyl, methoxypropoxypropoxypropyl, ethox- ypropyl, ethoxypropoxypropyl, or the like, but not limited thereto. Preferable 2-cyanoacrylates for use in the present inven- tion are ethyl 2-cyarroacrylate, methoxyethyl 2-cyanoacry- late and ethoxyethyl 2-cyanoacrylate. The present ester that has a dipentaerythritol residue as an alcohol residue and has an acrylic acid or mathacrylic acid residue as an acid residue, includes esters of dipentaeryth- ritol with acrylic acid or mathacrylic acid, or esters of a modified alcohol with acrylic acid or mathacrylic acid in which said modified alcohol is a dipentaerythritol modified by addition of a lactone such as caprolactone to dipen- taerythritol. Specific examples of these esters include, but are not limited to, dipentaerythritoltriacrylate (commercially available from Nippon Kayaku Co., Ltd. as KAYARAD D-330), dipentaerythritoltetraacrylate (commercially avail- able from Nippon Kayaku Co., Ltd. as KAYARAD D-320), dipentaerythritolpentaacrylate (commercially available from Nippon Kayaku Co., Ltd. as KAYARAD D-310), dipen— taerythritolhexaacrylate (commercially available from Nip- pon Kayaku Co., Ltd. as KAYARAD DPHA), and modified dipentaerythritolhexaacrylates in which dipentaerythritol is modified with caprolactone (commercially available from Nippon Kayaku Co., Ltd. as KAYARAD DPCA-20, KAYARAD DPCA-30, KAYARAD DPCA-60, and KAYARAD DPCA—120). Preferable esters among the ones listed above are dipen- taerythritoltriacrylate (available from Nippon Kayaku Co., Ltd. as KAYARAD D-330), dipentaerythritoltetraacrylate (available from Nippon Kayaku Co., Ltd. as KAYARAD D-320), dipentaerythritolpentaacrylate (available from Nip- pon Kayaku Co., Ltd. as KAYARAD D-310) and dipen- taerythritolhexaacrylate (available from Nippon Kayaku Co., Ltd. as KAYARAD DPHA). The amount of the present ester to be blended with 2-cyanoacrylate is preferably 1 through 50% by weight, more preferably 10 through 40% by weight, based on the total of the ester and 2-cyanoacrylate. When the blending amount of the ester is lower than 1% by weight, sufiicient durability will not be obtained. When it is more than 50% by weight, poor hardening and lowering of the adhesive strength will be caused. Stabilizers, polymerization accelerators, thickeners and other additives shown below may be appropriately incorpo- rated as optional ingredients into the cyanoacrylate adhesive in ordinary marmer. STABILIZER Hydroquinone, sulfurous acid gas or others may be added as a polymerization inhibitor for improving storage stability. POLYMERIZA'I‘ION ACCELERATOR AND INITIATOR A polyalkylene oxide or its derivative, crown ether or its derivative, silacrown ether or its derivative, calixarene derivative, or others may be added as an anionic polymer- ization accelerator for improving adhesion rate. An organic peroxide such as a hydroperoxide, peroxy ester, ketone peroxide, peroxyketal, dialkyl peroxide, diacyl peroxide, peroxydicarbonate or others may be added as a radical initiator. 5 10 15 20 25 30 35 40 45 50 55 60 65 4 THICKENER 2-Cyanoacrylate monomer is essentially colorless and transparent liquid of low viscosity; this liquid can be made viscous or thixotropic by dissolution or dispersion of a homopolymer or copolymer of various kinds of (meth)acry- lates, or acrylic rubber, cellulose derivative, silica or others. OTHER ADDITIVES Other additives such as a dye, pigment, plasticizer, diluent and others may be blended. BEST MODE FOR CARRYING OUT THE - INVENTION Hereinafter, the present invention will be explained in more details by way of examples and comparative examples. However, the present invention is not limited to these examples. EXAMPLES 1 THROUGH 16 COMPARATIVE EXAMPLES 1 THROUGH 5 Adhesives having the compositions shown in Table 1 were prepared, and their characteristics were evaluated as follows. Meanwhile, KAYARAD DPCA-20 and KAYARAD DPCA-30 in Table 1 are modified dipentaeryth- ritolhexaacrylates made by Nippon Kayaku Co., Ltd. Moisture and thermal resistance on chloroprene rubber: Chloroprene rubber was selected as the material to be adhered. The moisture and thermal resistance of the com- positions shown in Table 1 upon adhesion to chloroprene rubber was determined by the following procedures: Preparation of test pieces (1) Pieces of chloroprene rubber with the size of 3 mm (thickness)x25 mm (width)>