Abstract:
The present invention relates to phenylgycines and derivatives thereof, 1,4-aminobenzoyl compounds, and phenyl pyrazolinones as cure accelerators for anaerobically curable compositions.

Description:
RELATED U.S. APPLICATION DATA 
     This application continues in part from U.S. patent application Ser. No. 10/740,669, filed Dec. 22, 2003, now U.S. Pat. No. 6,897,277 the entire disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to phenylgycines and derivatives thereof, 1,4-aminobenzoyl compounds, and phenyl pyrazolinones as cure accelerators for anaerobically curable compositions. 
     2. Brief Description of Related Technology 
     Anaerobic adhesive compositions generally are well-known. See e.g., R. D. Rich, “Anaerobic Adhesives” in  Handbook of Adhesive Technology , 29, 467-79, A. Pizzi and K. L. Mittal, eds., Marcel Dekker, Inc., New York (1994), and reference cited therein. Their uses are legion and new applications continue to be developed. 
     Conventional anaerobic adhesives ordinarily include a free-radically polymerizable acrylate ester monomer, together with a peroxy initiator and an inhibitor component. Oftentimes, such anaerobic adhesive compositions also contain accelerator components to increase the speed with which the composition cures. 
     Desirable anaerobic cure-inducing compositions to induce and accelerate cure may include saccharin, toluidines, such as N,N,-diethyl-p-toluidine (“DE-p-T”) and N,N-dimethyl-o-toluidine (“DM-o-T”), acetyl phenylhydrazine (“AHN”), maleic acid (“MA”), and quinones, such as napthaquinone and anthraquinone. See e.g., Loctite U.S. Pat. No. 3,218,305 (Krieble), U.S. Pat. No. 4,180,640 (Melody), U.S. Pat. No. 4,287,330 (Rich) and U.S. Pat. No. 4,321,349 (Rich). 
     Saccharin and APH have been used as standard cure accelerator components in anaerobic adhesive cure systems since the inception of the technology, and has been well studied in that connection. Hitherto, it was believed that the nitrogen-hydrogen bond off the heterocycle ring was necessary to achieve performance under anaerobic conditions, as early studies substituting the hydrogen with an alkyl group proved to be ineffective. See F. J. Boerio et al., “Surface-Enhanced Raman Scattering from Model Acrylic Adhesive Systems”,  Langmuir , 6, 721-27 (1990), in which it is stated “[t]hese salts [of saccharin] are thought to be important factors in the curing reaction of the adhesive.” 
     Recently, Loctite (R&amp;D) Ltd. developed an anaerobic adhesive composition, which is defined by (a) a (meth)acrylate component; and (b) an anaerobic cure-inducing composition comprising an anaerobic curative within the following structure: 
                                
where A and A 1  may be selected from O and N; and
 
     R, R 1 , R 2  and R 3  may be the same or different and are selected from alkyl, alkenyl, cycloalkyl, cycloalkenyl, and aryl, having from 1 to about 30 carbon atoms, and may be substituted or interrupted with a heteroatom, and heterocyclic structures; or 
     R 1  and R 3  taken together may join to form a cyclic structure having from about 20 to about 28 ring atoms, and together represent dialkyl substituted polyether structures that may be substituted or interrupted with the trithiadiaza pentalene structure, which itself may or may not be substituted by A 1 , R 2 , or R 3 , as defined above. See U.S. Pat. No. 6,583,289 (McArdle). 
     There is an on-going desire to find alternative technologies for accelerating the cure of anaerobic curable compositions to differentiate existing products and provide supply assurances in the event of shortages or cessation of supply of raw materials. Accordingly, it would be desirable to identify new materials, which function as accelerators in the cure of anaerobic curable compositions. 
     SUMMARY OF THE INVENTION 
     The present invention provides new cure accelerators for anaerobic curable compositions. The anaerobic curable compositions are typically used as adhesives or sealants. 
     The anaerobic cure accelerators are generally phenyl glycines and derivatives thereof. For instance, the inventive cure accelerators may be within structure I 
                                
where R may appear up to five times on the phenyl ring and is independently selected from hydrogen, halogen, alkyl, alkenyl, hydroxyalkyl, hydroxyalkenyl, carboxyl, or sulfonato; R 1  is hydrogen, alkyl, alkenyl, hydroxyalkyl, hydroxyalkenyl, aralkyl, carbonyl or carboxyl; and R 2  is hydrogen, alkyl, alkenyl, hydroxyalkyl, hydroxyalkenyl, aralkyl, nitrogen, carbonyl or carboxyl; or R 1  and R 2  taken together form a ring structure. This ring structure may be saturated or unsaturated and may be substituted on one or more places by halogen, alkyl, alkenyl, hydroxyalkyl, hydroxyalkenyl, or carboxyl. The ring structure thus may be a saturated or unsaturated heterocycle.
 
     The use of these materials in anaerobic cure inducing compositions for anaerobic curable compositions as a replacement for some or all of the amount of conventional anaerobic cure accelerators (such as o-benzoic sulfimide or saccharin, used interchangeably throughout) and/or aromatic amines (such as toluidines like DE-p-T and DM-o-T) surprisingly provides at least comparable cure speeds and physical properties for the reaction products formed therefrom. 
     This invention also provides anaerobic curable compositions and anaerobic curable composition systems prepared with such cure accelerators, methods of preparing and using the inventive anaerobic curable compositions as well as reaction products of the inventive anaerobic curable compositions. 
     The present invention will be more fully appreciated by a reading of the “Detailed Description of the Invention”, and the illustrated examples which follow thereafter. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  depicts a bar chart of breakloose strength over time at ambient temperature of a control composition (Sample A) as contrasted with compositions within the scope of the invention (Samples B-E). 
         FIG. 2  depicts a bar chart of prevail strength over time at ambient temperature of a control composition (Sample A) as contrasted with compositions within the scope of the invention (Samples B-E). 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides anaerobic cure accelerators, which may be represented below within structure I: 
                                
where R may appear up to five times on the phenyl ring and is independently selected from hydrogen, halogen, alkyl, alkenyl, hydroxyalkyl, hydroxyalkenyl, carboxyl, or sulfonato; R 1  is hydrogen, alkyl, alkenyl, hydroxyalkyl, hydroxyalkenyl, aralkyl, carbonyl or carboxyl; and R 2  is hydrogen, alkyl, alkenyl, hydroxyalkyl, hydroxyalkenyl, aralkyl, nitrogen, carbonyl or carboxyl; or R 1  and R 2  taken together form a ring structure. This ring structure may be saturated or unsaturated and may be substituted on one or more places by halogen, alkyl, alkenyl, hydroxyalkyl, hydroxyalkenyl, or carboxyl. The ring structure thus may be a saturated or unsaturated heterocycle.
 
     Desirably, R is hydrogen or a carboxylate, such as ethyl carboxylate, R 1  is hydrogen, alkyl, such as methyl, or carbonyl, and R 2  is hydrogen, alkyl, such as methyl, or nitrogen, such that when R 1  comprises carbonyl and R 2  comprises nitrogen, R 1  and R 2  join to form a heterocycle, such as a pyrazolinone. Particular examples of such accelerators include N-phenyl glycine, ethyl-4-(dimethylamino)-benzoate (“EMBO”) and 3-methyl-1-phenyl-2-pyrazolin-5-one. 
     The inventive cure accelerators are useful in, or as primers for use with, anaerobic curable compositions as a replacement for some of or all of the typically used accelerator(s). These inventive cure accelerators display good solubility, stability and anaerobic activity in anaerobic curable compositions. 
     Anaerobic curable compositions generally are based on a (meth)acrylate component, together with an anaerobic cure-inducing compositions. In the present invention, such anaerobic curable compositions include the inventive anaerobic cure accelerator compounds within structure I. Examples of such compound include N-phenyl glycine, N-methyl-N-phenyl glycine, ethyl-4-(dimethylamino)-benzoate (“EMBO”), and 3-methyl-1-phenyl-2-pyrazolin-5-one, and of course combinations thereof. The anaerobic cure-inducing compositions may be substantially free of one or both of saccharin and/or toluidines. 
     (Meth)acrylate monomers suitable for use as the (meth)acrylate component in the present invention may be chosen from a wide variety of materials, such as these represented by H 2 C═CGCO 2 R 1 , where G may be hydrogen, halogen or alkyl groups having from 1 to about 4 carbon atoms, and R 1  may be selected from alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkaryl, aralkyl or aryl groups having from 1 to about 16 carbon atoms, any of which may be optionally substituted or interrupted as the case may be with silane, silicon, oxygen, halogen, carbonyl, hydroxyl, ester, carboxylic acid, urea, urethane, carbonate, amine, amide, sulfur, sulfonate, sulfone and the like. 
     Additional (meth)acrylate monomers suitable for use herein include polyfunctional (meth)acrylate monomers, such as, but not limited to, di- or tri-functional (meth)acrylates like polyethylene glycol di(meth)acrylates, tetrahydrofuran (meth)acrylates and di(meth)acrylates, hydroxypropyl (meth)acrylate (“HPMA”), hexanediol di(meth)acrylate, trimethylol propane tri(meth)acrylate (“TMPTMA”), diethylene glycol dimethacrylate, triethylene glycol dimethacrylate (“TRIEGMA”), tetraethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, di-(pentamethylene glycol) dimethacrylate, tetraethylene diglycol diacrylate, diglycerol tetramethacrylate, tetramethylene dimethacrylate, ethylene dimethacrylate, neopentyl glycol diacrylate, trimethylol propane triacrylate and bisphenol-A mono and di(meth)acrylates, such as ethoxylated bisphenol-A (meth)acryalte (“EBIPMA”), and bisphenol-F mono and di(meth)acrylates, such as ethoxylated bisphenol-F (meth)acrylate. 
     Still other (meth)acrylate monomers that may be used herein include silicone (meth)acrylate moieties (“SiMA”), such as those taught by and claimed in U.S. Pat. No. 5,605,999 (Chu), the disclosure of which is hereby expressly incorporated herein by reference. 
     Of course, combinations of these (meth)acrylate monomers may also be used. 
     The (meth)acrylate component should comprise from about 10 to about 90 percent by weight of the composition, such as about 60 to about 90 percent by weight, based on the total weight of the composition. 
     Recently, additional components have been included in traditional anaerobic curable compositions to alter the physical properties of either the curable compositions or the reaction products thereof. 
     For instance, one or more of maleimide components, thermal resistance-conferring coreactants, diluent components reactive at elevated temperature conditions, mono- or poly-hydroxyalkanes, polymeric plasticizers, and chelators (see International Patent Application No. PCT/US98/13704, the disclosure of which is hereby expressly incorporated herein by reference) may be included to modify the physical property and/or cure profile of the formulation and/or the strength or temperature resistance of the cured adhesive. 
     When used, the maleimide, coreactants, reactive diluent, plasticizer, and/or mono- or poly-hydroxyalkanes, may be present in an amount within the range of about 1 percent to about 30 percent by weight, based on the total weight of the composition. 
     The inventive compositions may also include other conventional components, such as free radical initiators, other free radical co-accelerators, inhibitors of free radical generation, as well as metal catalysts, such as iron and copper. 
     A number of well-known initiators of free radical polymerization are typically incorporated into the inventive compositions including, without limitation, hydroperoxides, such as CHP, para-methane hydroperoxide, t-butyl hydroperoxide (“TBH”) and t-butyl perbenzoate. Other peroxides include benzoyl peroxide, dibenzoyl peroxide, 1,3-bis(t-butylperoxyisopropyl)benzene, diacetyl peroxide, butyl 4,4-bis(t-butylperoxy)valerate, p-chlorobenzoyl peroxide, cumene hydroperoxide, t-butyl cumyl peroxide, t-butyl perbenzoate, di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, 2,5-dimethyl-2,5-di-t-butyl-peroxyhex-3-yne, 4-methyl-2,2-di-t-butylperoxypentane and combinations thereof. 
     Such peroxide compounds are typically employed in the present invention in the range of from about 0.1 to about 10 percent by weight, based on the total weight of the composition, with about 1 to about 5 percent by weight being desirable. 
     Conventional co-accelerators of free radical polymerization may also be used in conjunction with the inventive anaerobic cure accelerators. Such co-accelerators are typically of the hydrazine variety (e.g., APH), as disclosed in the &#39;330 and &#39;349 patents. 
     Stabilizers and inhibitors (such as phenols including hydroquinone and quinones) may also be employed to control and prevent premature peroxide decomposition and polymerization of the composition of the present invention, as well as chelating agents [such as the tetrasodium salt of ethylenediamine tetraacetic acid (“EDTA”)] to trap trace amounts of metal contaminants therefrom. When used, chelators may originally be present in the compositions in an amount from about 0.001 percent by weight to about 0.1 percent by weight, based on the total weight of the composition. 
     The inventive anaerobic cure accelerators may be used in amounts of about 0.1 to about 5 percent by weight, such as about 1 to about 2 percent by weight, based on the total weight of the composition. When used in combination with conventional accelerators (though at lower levels, for such conventional accelerators), the inventive accelerators should be used in amounts of about 0.01 to about 5 percent by weight, such as about 0.02 to about 2 percent by weight. 
     Metal catalyst solutions or pre-mixes thereof are used in amounts of about 0.03 to about 0.1 percent by weight. Other agents such as thickeners, non-reactive plasticizers, fillers, toughening components (such as elastomers and rubbers), and other well-known additives may be incorporated therein where the art-skilled believes it would be desirable to do so. 
     The present invention also provides methods of preparing and using the inventive anaerobic adhesive compositions, as well as reaction products of the compositions. 
     The compositions of the present invention may be prepared using conventional methods which are well known to those persons of skill in the art. For instance, the components of the inventive compositions may be mixed together in any convenient order consistent with the roles and functions the components are to perform in the compositions. Conventional mixing techniques using known apparatus may be employed. 
     The compositions of this invention may be applied to a variety of substrates to perform with the desired benefits and advantages described herein. For instance, appropriate substrates may be constructed from steel, brass, copper, aluminum, zinc, glass and other metals and alloys, ceramics and thermosets. The compositions of this invention demonstrate particularly good bond strength on steel, glass and aluminum. An appropriate primer may be applied to a surface of the chosen substrate to enhance cure rate. Or, the inventive anaerobic cure accelerator may be used as a primer itself. See e.g. U.S. Pat. No. 5,811,473 (Ramos). 
     In addition, this invention provides a method of preparing an anaerobic curable composition, a step of which includes mixing together a (meth)acrylate component and an anaerobic cure-inducing composition including the inventive anaerobic cure accelerator within structure I. 
     The invention also provides a process for preparing a reaction product from the anaerobic adhesive composition of the present invention, the steps of which include applying the composition to a desired substrate surface and exposing the composition to an anaerobic environment for a time sufficient to cure the composition. 
     This invention also provides a method of using as a cure accelerator for anaerobic curable compositions compounds within structure I. 
     And the present invention provides a method of using an anaerobic cure accelerator within structure I as a replacement for some or all of the typical accelerator used in anaerobic curable compositions. Of the course, the present invention also provides for a bond formed between two mated substrates with the inventive composition. 
     In view of the above description of the present invention, it is clear that a wide range of practical opportunities is provided. The following examples are provided for illustrative purposes only, and are not to be construed so as to limit in any way the teaching herein. 
     EXAMPLES 
     The inventive anaerobic cure accelerators were compared with control formulations containing conventional anaerobic cure components, such as one or more toluidines and/or saccharin, by breakloose and prevail torque adhesion tests on mild steel nut/bolt specimens. 
     A. Adhesive Formulations 
     Samples A-E were prepared from the noted components in the listed amounts, and mixed in low density polyethylene bottles. Each sample included a chelator and napthaquinone as stabilizers. 
     
       
         
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 COMPONENTS 
                 Sample/(Amt./wt. %) 
               
             
          
           
               
                 Type 
                 Identity 
                 A 
                 B 
                 C 
                 D 
                 E 
               
               
                   
               
             
          
           
               
                 (Meth)acrylate 
                 Base 
                 91.1 
                 91.1 
                 91.1 
                 91.1 
                 91.1 
               
               
                   
                 Anaerobic 
               
               
                 Non-reactive 
                 PEG 200 
                 2.52 
                 2.52 
                 2.52 
                 2.37 
                 2.58 
               
               
                 Diluent 
                 MO 
               
               
                 Conventional 
                 Saccharin 
                 3.78 
                 3.78 
                 3.78 
                 3.78 
                 3.78 
               
               
                 Accelerator 
               
               
                 Toluidine 
                 DE-p-T 
                 0.8 
                 — 
                 — 
                 — 
                 — 
               
               
                 Inventive 
                 EMBO 
                 — 
                 0.8 
                 — 
                 0.95 
                 — 
               
               
                 Accelerator 
                 NPG 
                 — 
                 — 
                 0.8 
                 — 
                 0.74 
               
               
                 Peroxide 
                 CHP 
                 1.8 
                 1.8 
                 1.8 
                 1.8 
                 1.8 
               
               
                   
               
             
          
         
       
     
     The Base Anaerobic was prepared from the following components in the noted parts by weight: 
                                                           Component   Parts                                        Polyethylene glycol (PEG) dimethacrylate   62.67           Polyethylene glycol (PEG) 200 mono oleate   26.13           Chelator   0.80           Stabilizer   1.50                        
B. Physical Properties
 
     Break and Prevail Strengths 
     For the break/prevail adhesion tests, the specimens were maintained at ambient temperature for a number of time intervals, and evaluated for performance. The time intervals were: 30 minutes, 1 hour, 2 hours, and 24 hours. The break and prevail torque strengths were observed and recorded for the specimens at ambient temperature for these time intervals. The torque strengths were measured on a calibrated automatic torque analyzer. 
     The data for these evaluations is illustrated in  FIGS. 1 and 2 . 
     Sample A (with DE-p-T) is shown as a comparison against Samples B and D (with EMBO as a replacement for DE-p-T) and Samples C and E (with NPG as a replacement for DE-p-T). The torque in breakloose mode for each of Samples B-E trails that of Sample A at the 30 minute, 1 hour and 2 hour intervals, and makes a rapid ascent to levels roughly equivalent at the 24 hour interval. Sample C actually meets the same level of breakloose torque strength as Sample A after this time interval. 
     As regards the torque in prevail mode, after the 30 minute and 1 hour intervals, the observations are roughly the same. At the 2 hour interval, each of Samples B-E maintained the previous level of strength, where Sample A advances significantly. However, at the 24 hour interval, Samples B and D (with EMBO as a replacement for DE-p-T) show vastly improved performance over Sample A. And Samples C and E show significant improvement over the values observed at the 2 hour interval, and coming closer to Sample A. 
     More specifically, these data indicate that the anaerobic cure accelerators in accordance with this invention functioned in anaerobic (meth)acrylate-based adhesives at room temperature like traditional anaerobic (meth)acrylate-based adhesives when applied and cured on the substrates, though not as well in most instances as those anaerobic (meth)acrylate-based adhesives accelerated with DE-p-T in the breakloose mode. 
     The inventive accelerators are useful in anaerobic curable compositions as a replacement for some of or all of the saccharin and/or aromatic amine typically used as an accelerator combination.