WO2002090453A2

WO2002090453A2 - Anaerobic sealant compositions having enhanced washability

Info

Publication number: WO2002090453A2
Application number: PCT/US2002/014001
Authority: WO
Inventors: Stephen W. Ernst; Charles M. Muisener; Frederick F. Newberth, Iii
Original assignee: Henkel Loctite Corporation
Priority date: 2001-05-08
Filing date: 2002-05-01
Publication date: 2002-11-14
Also published as: AU2002256439A1; WO2002090453A3

Abstract

An anaerobic sealant composition having enhanced washability is provided. The composition includes a (meth)acrylate component, which includes mono(meth)acrylate and multi(meth)acrylate components; and an anaerobic cure-inducing composition. Desirably at least about 90% by weight of said (meth)acrylate component is polar group-functionalized.

Description

ANAEROBIC SEALANT COMPOSITIONS HAVING ENHANCED WASHABLITY

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates to an anaerobic impregnation sealant composition having improved washability from and sealing of porous parts. The present invention further relates to methods of preparing such compositions, as well as methods and apparatus for testing the washability of the compositions.

Brief Description of Related Technology

[0002] Impregnation sealing of porosity in porous parts frequently is carried out by introducing sealant compositions into the porosity under a pressure differential, by wet vacuum and dry vacuum techniques, all of which being well known.

[0003] Impregnation sealing of porosity may also be carried out by wicking, where the impregnation sealant is flowed across the surface of the porous part and allowed to wick into the voids thereof during a selective period of time. Once the wicking action is completed, the impregnated parts are washed to remove excess surface impregnant. With certain parts, wicking may be enhanced by creating a vacuum inside a cavity within the part. For example, with large parts such as engine blocks, which may not be able to be accommodated by conventional wet vacuum and dry vacuum systems, all but one of the ports or openings into the interior of the engine block is closed off, followed by attachment of a vacuum pump to the remaining port. After the vacuum pump is actuated, air will attempt to enter the engine block through the voids or pores in the porous metal constituting the engine block. The resulting vacuum and air flow transport any resins which are applied to the surface of the metal part into the porosity thereof. [0004] The sealant compositions typically employed in the aforementioned impregnation applications include a wide variety of self-curing anaerobic sealants, which are curable via free- radical polymerization in the presence of suitable free-radical initiators — peroxy-type initiators, as well as heat-curing sealants, and sealants which cure by both anaerobic and heat cure mechanisms.

[0005] Illustrative of known (meth)acrylic monomer-based anaerobic impregnant compositions are described in U.S. Patent Nos. 3,672,942 (Neumann); 3,969,552 (Malofsky); Re. 32,240 (DeMarco) and 4,632,945 (Garcia), which are curable via free-radical polymerization in the presence of suitable free-radical initiators — e.g., peroxy-type initiators.

[0006] U.S. Patent No. 5,256,450 (Catena) provides a water miscible, anaerobic polymerizable acrylate composition which contains no organic solvents or surfactants. The composition includes about 75 to 90% by weight of a mixture of acrylate or methacrylate monomers of a certain formula about 10 to 25% by weight of an hydroxy -terminated acrylate and an effective amount of a free radical initiator to initiate cure of the monomers upon exclusion of oxygen.

[0007] With respect to heat-curing impregnation sealants, examples include those ones described in U.S. Patent Nos. 4,416,921 (Dunn), 5,212,233 and 5,416,159 and U.K. Patent Nos. 1,308,947 and 1,547,801, as well as sealants which cure by both anaerobic and heat-cure mechanisms.

[0008] U.S. Patent No. 4,147,821 (Young) describes a composition for impregnating porous articles such as metal castings. The disclosed impregnant composition includes a monomer system, such as mixtures of monofunctional and polyfunctional (meth)acrylic esters, in combination with a peroxy catalyst and an inhibitor (col. 3, lines 1-2 1). The '821 patent discloses that it is convenient to include emulsifying agents, such as wetting agents and detergents, in the impregnant as an aid to subsequent water washing. [0009] European Patent No. 0 169 348 Bi also describes heat curing compositions for impregnating porous articles. The disclosed compositions are described as having improved washability. These compositions include a partially water soluble (meth)acrylate in amounts of 50-85% by weight. The water soluble (meth)acrylate is either soluble at a rate of at least 20% by weight, and/or is a hydroxyalkyl (meth)acrylate soluble at a rate of at least 5% by weight and less than 20% by weight. Also included in these compositions are an ethylenically (C820) unsaturated cross-linking agents and a surfactant. If the ethylenically unsaturated cross-linking agent is a methacrylic compound its inclusion is limited to 6% by weight.

[0010] The anaerobic compositions used in such impregnation sealant compositions are victim to the criticism that they are typically two-part compositions, one part including the monomer to be polymerized, and the other part containing a catalytic accelerator of polymerization, so that upon mixing of such parts, the composition must be constantly aerated.

[0011] In view of such criticism, heat-curable (meth)acrylic monomer-containing impregnant compositions have become popular with consumers and are in widespread use. For instance, International Metal Impregnator's IM-3 000 and KID Impreganier and Polymertechnik GMIBH's Ml 80.10.2 are widely used. The commercially available European Community Material Safety Data Sheet reports the monomer in the KID composition to be 60-100% 2- hydroxyethyl methacrylate. The heat-curable impregnant compositions may be effectively used, with a minimum of monitoring and maintenance (as compared with anaerobic impregnant compositions), with little or no aeration. Such heat-curable impregnant compositions may cure at temperatures ranging from 40°C to 150°C, depending on the specific formulation employed.

[0012] Once the impregnant composition (either anaerobic or heat cure) is introduced into the porosity of the parts to be sealed, the parts are transferred to an agitated water rinse zone for removal of any remaining surface accumulations of sealant or extraneous sealant which is trapped in blind holes of the impregnated parts. Thereafter, the impregnated parts which have been treated with anaerobic curable compositions are passed to a tank containing a catalyst activator solution which serves to cure the sealant composition at the entrance of the porosity. This creates a hardened plug or cap in the outer portion of the pores, trapping the remaining resin for anaerobic self-cure. With respect to impregnated parts which have been treated with heat-curable compositions, such parts are passed to a tank containing hot water, e.g., at a temperature of 70°C to 120°C _or other medium at elevated temperature which serves to cure the sealant composition in the porosity. Heat-curable compositions, however, suffer from the disadvantage that the monomer expands more rapidly during cure than the porous metal part and the unpolymerized monomer is often forced out of the pores before final cure. This results in failure to achieve complete sealing of the pores. Moreover, heat-cure compositions use significantly more heat than anaerobic sealants in order to polymerize, thus increasing costs associated with processing and manufacture.

[0013] One problem common to many impregnation sealants is the accumulation of excess sealant on the outer surface of parts. Excess sealant is removable by normal abrasion or by contact with various liquids. The removal of extraneous or surface accumulation of anaerobic and heat curing sealants from the parts is important because such residues can readily contaminant the environment of porous parts. In addition, such surface sealant deposits may, by virtue of their thickness, cause the impregnated product part to vary from the desired dimensional specifications. This often renders the part deficient or even useless for its intended function in applications requiring close dimensional tolerances.

[0014] In addition, such surface sealant deposits may interfere with subsequent painting, plating, or assembly operations or cause delamination of applied paint or plated films which frequently are performed on porous articles subsequent to their impregnation. Specifically, such surface sealant deposits may be removed during painting or plating operations, resulting in contamination of the baths used in such operations, and may interfere with the adhesion of paint, plating, and the like to the impregnated part. [0015] Furthermore, when precision holes are present, such as machined holes for cylinders and bearings, or when threaded holes are present, sealant residue often collects and cures in these cavities, rendering them useless for subsequent use.

[00161 To remove excess sealant from impregnated articles, agitated rinse times of significant duration have conventionally been required. The actual rinse time will depend upon, among other things, the nature of the article, such as porosity, and the washability of the uncured sealant in an aqueous solution. Often such rinse operations are from about one to about twenty minutes, but actual rinse times may for any particular article be even longer in duration. In addition, chemicals, such as surfactants or detergents, have been added to the aqueous solution to facilitate the removal of sealant deposits.

[0017] For example, U.S. Patent No. 3,672,942 (Neumann) discloses an anaerobic impregnant comprising a free-radical polymerizable acrylate ester monomer and free-radical polymerization initiator, which requires an organic solvent, such as a halogenated hydrocarbon, to remove uncured impregnant from the outer surface of a porous article.

[0018] U.S. Patent No. 3,969,552 (Malofsky) describes a washing process for removing excess impregnant from the surface of the porous article after porosity impregnation. The disclosed impregnation composition comprises an acrylic anaerobic curing resin and a peroxy initiator therefor. The wash solution is an aqueous solution of a nonionic surfactant of specified formula which is necessary for the removal of uncured impregnant.

[0019] The impregnated and water-rinsed parts may be transferred to an activator zone in which the impregnated parts are contacted with a catalyst activator solution, to effect curing of the sealant material at the entrance to the pores in the parts. This creates a hardened plug or cap of sealant material in the outer portion of the pore, trapping the resin for anaerobic self-cure. [0020] Thereafter, parts impregnated with anaerobic compositions may be transferred to a final rinse zone for removal of the activator solution from the impregnated parts. This final rinse solution may be at elevated temperature, e.g., on the order of about 50°C, to warm the impregnated parts for quick drying, and to accelerate curing of the anaerobic impregnant within the interior porosity of the article, the rate of such cure increasing with increasing temperature.

[0021] As stated above, however, removal of remaining anaerobic surface sealant or sealant trapped in blind holes of the impregnated parts is typically attempted using an agitated water rinse zone. In the process, however, if the uncured monomer fails to adequately wash off, blind holes which are intended for functioning of the part, e.g. precision holes or threaded holes of various sizes and thread-types, can become partially or fully occluded so as to render the part unusable for its intended purpose.

[0022] Notwithstanding the state-of-the-art it would be desirable to provide an anaerobic impregnation sealant compositions having improved washability and sealing of porosity in parts.

SUMMARY OF THE INVENTION

[0023] The present invention meets the desires addressed above by providing an anaerobic impregnation sealant compositions having improved washability from porous parts as compared to conventional anaerobic compositions and superior sealing of porosity in parts in comparison to heat cure technology.

[0024] As used herein, the term "(meth)acrylate" or "(meth)acrylic" refers to acrylate and/or methacrylate species. The term "mono(meth)acrylate" refers to the presence of a single (meth)acrylate group, while the term "multi(meth)acrylate" refers to more than one (meth)acrylate group. [0025] More specifically, the anaerobic sealant compositions of the present invention include a (meth)acrylate component which includes a mono(meth)acrylate and a multi(meth)acrylate, at least 90% of said (meth)acrylate component being polar group- functionalized; and an anaerobic cure-inducing composition. In one particularly desirable aspect of the invention, there is also included a surfactant. Desirably, the (meth)acrylate component includes an hydroxy alkyl (meth)acrylate.

[0026] The present invention also relates to reaction products formed from the aforementioned composition, as well as methods of producing the composition and methods of use.

[0027] Thus, in another aspect of the present invention there is provided a method of impregnating a porous part which includes:

(i) providing an anaerobic impregnation composition which includes: a) a combination of mono(meth)acrylate and multi(meth)acrylate components, at least about 90% of said combination being a polar group-functionalized (meth)acrylate; and b) an anaerobic cure-inducing composition;

(ii) submersing a porous part in the anaerobic impregnation composition to permit filling of the pores with said composition;

(iii) subjecting the pore-filled part to anaerobic curing conditions to permit cure of said anaerobic composition within the porosity of said part; and

(iv) aqueous rinsing the uncured anaerobic impregnation composition from the surface of said metal part.

[0028] In a further aspect of the present invention there is provided a method of making a water washable anaerobic impregnation composition by combining a (meth)acrylate component which includes a mono(meth)acrylate and a multi(meth)acrylate, at least 90% of said (meth)acrylate component being polar group-functionalized, and an anaerobic cure-inducing composition. [0029] Another aspect of the invention relates to an anaerobic sealant composition which includes at least about 60% by weight of a polar group-functionalized mono(meth)acrylate, at least about 5% by weight of a polar group-functionalized multi(meth)acrylate; and an anaerobic cure-inducing composition; whereby said sealant composition exhibits at least 90% sealability on porous metal parts and at least 50% washability from precision holes present on said porous metal part subsequent to anaerobic cure-inducing conditions. Another aspect of the present invention relates to a method of making such a composition by combining the components from such a composition.

[0030] In still another aspect of the invention there is included an apparatus for determining the water- washability of an anaerobic composition.

[0031] In yet another aspect of the invention there is included a method of determining the water- washability of an anaerobic sealant composition which includes providing a test apparatus having at least one blind machined hole on its surface subjecting the apparatus to anaerobic impregnation conditions, washing the apparatus in aqueous medium to remove uncured anaerobic composition, and determining the amount said hole is unobstructed by cured sealant residue on its surface. Desirably, the machined hole is a threaded hole, the portion of threads remaining unobstructed subsequent to cure and washing, as compared to the total number of threads being used to designate the percentage of washability. The higher the portion of unobstructed threads, the higher the washability of the anaerobic composition.

[0032] Other aspects and features of the invention will be more readily apparent from the

Detailed Description of the Invention section.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 shows a perspective view, a cross-sectional view and an enlarged view of a test apparatus made and used in accordance with the present invention. Figure 2 is a cross- sectional view of Figure 1. Figure 3 is an enlarged view of Figure 2. [0034] Figure 4 shows a bar graph comparing the washability of impregnation compositions.

[0035] Figure 5 shows a bar graph comparing the sealability of impregnation compositions.

DETAILED DESCRIPTION OF THE INVENTION

[0036] The (meth)acrylate component of the present invention includes a combination of mono- and multi(meth)acrylates each having polar group functionality. Desirably, at least about 90% by weight of the total composition of said (meth)acrylate component is polar group- functionalized.

[0037] In another aspect of the invention, the anaerobic sealant compositions of the prior art include at least 60% by weight of a polar group-functionalized mono(meth)acrylate; at least 5% by weight of a multi(meth)acrylate, which is desirably a polar group functionalized multi(meth)acrylate; and an anaerobic cure-inducing composition.

[0038] The polar group-functionalized mono(meth)acrylate is desirably present in amounts of about 60% to about 95% by weight, more desirably in amounts of about 75% to about 95%, and most desirably in amounts of about 80% to about 90% by weight.

[0039] Non-polar group-functionalized (meth)acrylates are useful in the present invention, in addition to polar group-functionalized (meth)acrylates. Such (meth)acrylates are generally used in lower amounts than polar group-functionalized materials so as not to render the composition impractical or commercially unviable from a washability standpoint. Generally such materials may be present in amounts of about 7% to about 13% by weight.

[0040] Desirably the multi(meth)acrylate is present in amounts of about 8% to about

20% by weight. Most desirably the rήulti(meth)acrylate is present in amounts of about 10% to about 15%) by weight. The composition of the present invention exhibits at least 50% washability on porous metal parts, and desirably seals at least 90% and more desirably 100% of the pores, while being substantially washed from blind holes. The (meth)acrylate component is present in the composition in amounts up to about 98% by weight of the total impregnation composition.

[0041] The polar groups present in the composition include without limitation, such groups as labile hydrogen, hydroxy, amino, cyano, halogen, heterocyclic rings, alkoxy and combinations thereof. Of particular usefulness is the hydroxy functionality, at least in part because they are readily commercially available. Such hydroxy functionalized (meth)acrylates are commercially readily available.

[0042] Mono(meth)acrylates useful in the present invention include those which conform to the structure:

H₂C=CGCO₂R wherein G may be hydrogen, halogen or alkyl of 1 to about 4 carbon atoms, and R may be selected from alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkaryl, aralkyl or aryl groups of 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, carbamate, amine, amide, sulfur, sulfonate, sulfone and the like.

[0043] Examples of polar group functionalized mono(meth)acrylates include cyclohexylmethacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, t-butylaminoethyl methacrylate, cyanoethylacrylate, and chloroethylmethacrylate. Other common monofunctional esters include alkyl esters such as lauryl methacrylate. Many lower molecular weight alkyl esters exhibit volatility, and frequently it may be more desirable to use a higher molecular weight homologue, such as decyl methacrylate or dodecyl methacrylate, or any other fatty acid acrylate esters, in (meth)acrylate-based impregnant compositions. [0044] Hydroxyalkyl (meth)acrylates are particularly useful. The alkyl portion may be selected from numerous linear, branched or cyclic groups, e.g., having 1-20 carbon groups, which may also include various substitutions.

[0045] Desirably at least a portion of the (meth)acrylic monomer comprises a di- or other multi(meth)acrylate ester. These multifunctional monomers produce cross-linked polymers, which serve as more effective and more durable sealants. Various (meth)acrylate monomers may be used, such as those multi(meth)acrylate esters which have the following general formula:

[0046] wherein R represents a radical selected from the group consisting of hydrogen, lower alkyl of from 1 to about 4 carbon atoms, hydroxyalkyl of from 1 to about 4 carbon atoms, and

R is a radical selected from the group consisting of hydrogen, halogen, and lower alkyl of from 1 to about 4 carbon atoms; R⁵ is a radical selected from hydrogen, hydroxyl, and

m may be 0 to 12, preferably from 0 to about 6; n is at least 1 (e.g., 1 to about 20 or more, preferably between about 2 to about 6); and p is 0 or 1.

[0047] Examples of these polymerizable multi(meth)acrylate esters include, but are not limited to, di-, tri- and tetraethyleneglycol dimethacrylate, dipropylenegϊycol; dimethacrylate; polyethyleneglycol dimethylacrylate; di(pentamethyleneglycol) dimethacrylate; tetraethyleneglycol diacrylate; tetra-ethyleneglycol di(chloracrylate); diglycerol diacrylate; diglycerol tetramethacrylate; tetramethylene dimethacrylate; ethylene dimethacrylate; and neopentyiglycol diacrylate. Others include, triethyleneglycol dimethacrylate, butyleneglycol dimethacrylate, bis(methacryloxyethyl) phosphate, 1 ,4 butane diol di(meth)acrylate and trimethylol propane dimethacrylate.

[0048] Due to the inclusion of the polar group functionalized (meth)acrylates in the recited amounts, the washability of the anaerobic impregnant composition is dramatically improved as compared to conventional anaerobic impregnant compositions. As previously mentioned, the polar group-functionalized (meth)acrylate component desirably includes hydroxy groups. The polar group-functionalized (meth)acrylate desirably has a water solubility of at least about 10% to about 15%, and more desirably about 18% to about 25%).

[0049] The (meth)acrylic monomers employed in the present compositions may be curable through a free-radical mechanism. The anaerobic cure-inducing composition includes an initiator present therein, or an initiator system comprising a redox polymerization initiator (i.e., an ingredient or a combination of ingredients which produce an oxidation reduction reaction, resulting in the production of free radicals). Suitable initiators may include peroxy materials — e.g., peroxides, hydroperoxides, and peresters — which under appropriate conditions decompose to form peroxy free radicals which are initiatingly effective for the polymerization of the (meth)acrylic monomer. Saccharin is also a desirable additive in the anaerobic cure-inducing composition. [0050] Anaerobic cure accelerators may also be employed and may be selected from a variety of known materials containing active metal ion species, such as copper or iron. Additionally, amines well known in anaerobic chemistry may also be added.

[0051] In the practice ofthe invention relating to the use of a (meth)acrylic monomer- based impregnant composition to seal porosity in porous parts, excess impregnant is removed from the impregnated parts by aqueous washing.

[0052] The surfactant component of the inventive composition may be provided from a variety of surfactants. Nonionic, anionic and cationic surfactants may be employed. Desirably, when used, the surfactant is present in amounts of up to about 10% by weight of the total composition. In general, such surfactants as alkyphenol ethoxylates, linear alcohol ethoxylates, branched alcohol ethoxylates, alkylamine ethoxylates, polyethylene glycols, fatty acid ethoxylates and diesters may be employed. Particularly desirable surfactants are SURFONIC N- 95 , commercially available from Huntsman Corporation, and VARIONIC LI 67, as well as TRITON SP-160 and TERGITOL NP-b from Union Carbide; and NEODOL R25-3 from Shell Chemical Company. Other surfactants known to the industry may be employed.

[0053] Notwithstanding such measures, the surfactant component of the composition tends to minimize the extent to which any material sticks to the vessel or other components of the system. Thus, a single mixing and reaction tank may be employed for all of the reagent contacting operations, including temperature elevation, precipitating agent contacting, and any other ancillary treatment steps.

[0054] The porosity impregnation is desirably effected by a "dry vacuum" technique. It will be recognized, however, that such mode of impregnation is illustrative only, and that the porosity impregnation may be carried out by various other techniques, including "wet vacuum" impregnation and wicking impregnation techniques well known in the art. The choice of various "wet", "dry", "dry/pressure", "wet/pressure" or wicking impregnation techniques, will depend on a number of factors, including the specific (meth)acrylic monomer-containing impregnant composition, the size, shape, composition and porous character of the porous parts, and the intended end use of the impregnated parts, as will be appreciated by those skilled in the art.

[0055] The porosity impregnation systems in this illustrative embodiment generally comprises an impregnation chamber having an interior volume in which is disposed a basket containing porous metal parts.

[0056] The impregnation chamber is joined in flow communication via a conduit to a vacuum generating means, for selectively drawing a vacuum on the impregnation chamber, so that the air therein is withdrawn to evacuate the porosity of the porous parts in the basket and de- aerate the impregnant composition.

[0057] Subsequent to the evacuation of the interior volume of the impregnation chamber, impregnant composition is stored in reservoir and maintained therein in an aerobic state, at higher pressure than the evacuated impregnation chamber, is flowed into the interior volume of the impregnation chamber. The impregnant material may be of any the aforementioned compositions.

[0058] The (meth)acrylic monomer-containing impregnant composition in the reservoir may also be deaerated by means of a conduit joining the reservoir with the vacuum generating means, just prior to transferring the impregnant from the reservoir to the impregnation chamber. The vacuum drawn by the vacuum generating means is discontinued once the impregnant fills the impregnation chamber to the desired extent.

[0059] As a result, the impregnant penetrates into the porosity of the porous parts in the basket. Such hydrostatic impregnation may be further assisted by reversing the vacuum generating means to pressurize the interior volume of the impregnation chamber, to force the impregnant further into small porosity passages. [0060] Subsequent to this impregnation, the impregnant is returned to the impregnant reservoir. While the impregnant is being returned to the reservoir, the basket may be spun briefly by suitable spinning means to allow centrifugal force to remove the major portion of the impregnant on the exterior surfaces of the porous parts.

[0061] Next, the basket containing the impregnated porous parts is removed from the impregnation chamber and transferred, via a suitable support joined to the basket, to the aqueous washing chamber, for water rinse removal of excess impregnant from the impregnated porous articles.

[0062] Subsequent to aqueous washing, the basket of porous parts may suitably be passed to activation chamber. The activation chamber contains an aqueous solution of activator material, as supplied from the activator reservoir to the chamber, to cure the impregnant composition at the entrance of the pores in the porous parts. This creates a hardened plug or cap in the outer portion of the pores, trapping the remaining curable composition in the interior pore volume of the porosity for anaerobic self-cure.

[0063] The activator may be any suitable material which is effective to cure the impregnant at the surface of each pore. Illustrative of suitable activator species which may be potentially usefully employed in combination with anaerobically-curing monomer-containing impregnant compositions, are erythorbic acid, sodium erythorbate, ascorbic acid, and ascorbic acid derivatives, thiourea, and sodium metabisulfite, as well as any other efficacious materials which are usefully employed as reducing agents in the broad practice of the present invention.

[0064] The concentration of activator in the aqueous solution may suitably be up to about

2% by weight, based on the weight of aqueous solvent, with concentrations on the order of about 1% by weight, on the same weight basis, being generally usefully employed. [0065] Subsequent to the activation step in the activation chamber, the basket of impregnated porous parts may be removed therefrom and transferred to final rinsing and drying steps.

[0066] The compositions of the present invention are capable of impregnating and sealing the porosity of porous parts, while possessing an enhanced ability of washing away excess impregnants from holes having a defined purpose in an assembly process using the part. For instance, the inventive compositions may fill and seal the pores of a part as intended, but also fill a guide pin hole or a female threaded surface, which is unintended. The inventive compositions are capable of selective substantial removal from the latter while remaining within the former for curing and sealing. A benefit of such a composition is that for instance stress cracking and threadstripping may be avoided when a bolt or screw, respectfully, is introduced to the guide pin hole or female threaded surface.

[0067] The compositions of the present invention also do not suffer from the known problem of "bleed out" that is seen with heat cure in pregnation sealants. "Bleed out" is due to the difference in coefficients of thermal expression between the sealant and the part to be sealed. In impregnation sealants of the present invention, however, the phenomena is over come be the length and completion of the cure.

[0068] The apparatus and method of testing the washability of impregnation compositions can be described by reference to Figures 1-3. As shown in Figure 1, test block 10 has multiple precision holes or cavities 12 and 12' on one or more of its surfaces. The cavities may have a smooth internal surface for accommodation of such parts as pins, cylinders or bearings, such as shown in cavity 12' or may be threaded such as shown in cavity 12, for subsequent engagement with a mateable threaded part. Test block 10 is desirably made from metal, such as aluminum, but can be made from a variety of other materials.

[0069] In the method of testing the washability of impregnation compositions, test apparatus 10 is submersed in an impregnation tank containing an impregnation composition in a conventional method. The impregnation sealant composition is allowed to penetrate into the cavities 12 and/or 12', and subjected to cure conditions.

[0070] Subsequent to the initial impregnation with sealant, the test apparatus is removed and optionally centrifuged to eliminate excessive uncured sealant on the test apparatus surface. Centrifuging, however, removes only the larger portions of uncured sealant but does not substantially eliminate the fine coating or the build-up of adhesive in the precision cavities.

[0071] The test apparatus, such as through threaded attachment area 22, can be engaged with an oscillating device to repeatedly dip the apparatus into a wash water tank. The oscillation rate, time of washing, as well as the stroke distance may be varied depending on the size, shape and type of test apparatus. For block-type configurations such as shown in Figure 1, about 50 oscillations per minute in and out of the water at a stroke distance of about 5 inches is desirable. The wash cycle may also vary, but is desirably about 1-3 minutes and most desirably about 2 minutes.

[0072] Subsequent to the wash cycle, an optional activator bath may be employed, whereby the test apparatus is immersed in the activator. An optional warm water bath may also follow.

[0073] Once the test apparatus has been subjected to the washing cycle, the precision cavities are evaluated to determine the portion of the cavity which remains unobstructed by surface curing of the sealant composition. A cross section of Figure 1 is shown taken along line 2-2. Cavity wall 16 is shown having at depth ti . The adjacent cavity body is shown being filled with the uncured inventive impregnation sealant composition 18, which occurs when the test apparatus is immersed. Also shown in Figure 3 is an enlarged view of cavity 16 having cured sealant impregnant composition 20 remaining at the bottom of the cavity. The depth of the cavity tihas associated therewith a predetermined number of threads. The number of threads which are unobstructed can be determined by comparing the depth or number of threads t₂ remaining unobstructed subsequent to washing, with the total number of threads

A percentage of unobstructed threads is taken as the water- washability value of the composition.

[0074] Ideally, substantially none of the cavities are obstructed by sealant composition.

Desirably, the precision cavity is a threaded hole with a known number of threads. In such a case, a measurement device known as a thread gauge, or similar type of device, may be employed to determine the number of turns in the precision cavity which remain unobstructed by cured surface sealant. The percentage of unobstructed threads can then be calculated. By comparing the unobstructed number of turns or thread depth (t₂) with the original thread depth (tι),the amount of unobstructed threads or turns can be determined.

[0075] It is on this basis, i.e., unobstructed cavity portion, by which the amount of washability is determined. Figure 4 shows the test block washability, of Compositions A-D versus a control, which was a test apparatus that did not undergo the submersion in the anaerobic sealant composition. The percentage of unobstructed threads is calculated and indicates the degree of washability of the inventive composition from blind holes, such as those shown in Figures 1-3. This ability to wash from such cavities is particularly important in the manufacturing of a variety of parts which require engagement with mateable parts subsequent to the impregnation process. Whereas prior conventional anaerobic compositions provided excellent sealing, their washability was substantially less on parts containing such cavities and the degree of obstructed area in the cavity was often commercially less than desirable. Prior heat curing compositions provided a degree of washability, but substantially inferior sealability. The present invention provides both superior washability and sealability.

[0076] Figure 4 shows the inventive Composition A as having a 90% unobstructed thread area, indicating superior washability as compared to anaerobic Compositions C and D, the former of which is commercially available and which show washability of less than 50%. Inventive Composition A also shows superior washability as compared to the commercially available heat cure impregnation Composition B, IM-3 000. Composition C is the commercially available ANASEAL RT-20 sold by Chemence, Inc. Composition B is a heat cure composition known as IM-3 000, sold by International Metal Impregantor. Composition D is identical to Composition B, except the heat cure system has been replaced with an anaerobic cure inducing system.

[0077] It is apparent from Figure 4 that the anaerobic compositions of the present invention have substantially superior washability over commercially available heat cure compositions and conventional anaerobic compositions, as well as heat cure compositions which have been modified to be anaerobically curable. The present invention also provides a significant improvement in sealability, when compared to the heat cure compositions, such as Composition B.

[0078] Figure 5 shows the sealability of Compositions A-D. These compositions refer to those previously described in Figures 1-3. It is noted that the sealability is determined by the air flow, i.e., leakability, of the test specimen as described herein under Test Methodology For Pressure Tests. The dimensions of the test specimens were made in accordance with Military Specifications Mil-I-17563C. All anaerobic compositions demonstrated 0% leakage, indicating substantially 100% sealability. The comparative heat cure Composition B showed significant air flow, indicating substantial leakage and nonsealability.

[0079] The features and advantages of the present invention are more fully shown by the following examples which are provided for purposes of illustration, and are not to be construed as limiting the invention in any way.

EXAMPLES

Example 1

[0080] In this example, anaerobic Composition A in accordance with this invention was prepared from the components in the recited amounts: COMPOSITION A

¹ polyethylene glycol di(meth)acrylate, the ethylene portion having a molecular weight of 600. ¹ tertiary butyl hydroperoxide

[0081] Compositions B-D were used as comparison compositions. Composition B is the commercially available heat cure product previously referred to herein as IM-3 000, Composition C is a commercially available anaerobic product, Anaseal RT-20 sold by Chemence, Inc., and Composition D is IM-3000 modified by replacing the heat cure system with an anaerobic cure-inducing system.

[0082] Compositions A-D were used to impregnate test specimens described below and in accordance with the test method described herein. Both wet vacuum impregnation and dry vacuum (DVP) impregnation processes were performed.

TEST SPECIMENS

[0083] Tubular iron powder metal test specimens were prepared with varying densities and having the dimensions according to military specification Mil-I-17563C. The porosity void volume was approximately 15%). Aluminum test specimens were also dimensionally prepared in accordance with aforementioned military specification. These test specimens were used to generate sealability and washability studies, the results of which are reported in Table I and the figures. TEST METHODOLOGY FOR PRESSURE TESTS

[0084] The tubular test specimens were sealed on both ends in accordance with military specifications set forth in MIL-I- 17563. Air pressure was introduced into the hollow body of the test specimen at 50 psi for a period of five (5) minutes. The flow rate of air into the specimen was greater than 32,000 cc/mm @ 50 psi for the 6.2 iron density specimens, 24,000 cc/mm for the 6.5 and density specimens and 14,300 cc/mm for the 6.8 density specimens and 28,000 for the aluminum specimens. Measurement of the leakage was indicated by the rate of air flow after the five (5) minute interval.

[0085] The test results are shown below in Table I.

TABLE I

¹ Pressure test at 50 psi

² DVP = dry vacuum process

⁵ Powdered Iron or Aluminum [0086] As indicated in Table I, the weight of the test specimens were measured before impregnation (dry weight), after impregnation (after cure weight). The weight increase (dry weight increase) of the inventive compositions, as well as the dry weight increase of a commercially available heat cure composition, Composition B (International Metal Impregnator's IM 3000) was calculated. The increase in weight as a result of impregnation indicates the relative amount of cured resin in the pores of the test specimen.

[0087] As is evident from the data, the test specimens impregnated with the inventive composition show a significantly greater weight increase for the majority of powdered iron test specimens regardless of the specimen density or whether wet or dry vacuum processes were used.

[0088] Table I also shows the results of pressure tests conducted on the same test specimens. The control pressure test is indicated as "unimpregnated". As is evident from the table, no leakage was measured for all powdered iron test specimens impregnated with the inventive compositions, and only relatively minor leakage in aluminum test specimens. This is in contrast to those impregnated with the comparative heat cure composition exhibited substantial leakage in all test specimens regardless of density or metal makeup.

TEST BLOCK APPARATUS FOR DETERMING WASHABILITY

[0089] Apparatus test blocks were made from aluminum 6061 bar stock in the configuration as shown in Figure 1. The blocks were designed with threaded holes M-4 three (3) per side at three (3) different depths. The blocks were also grit blasted on two sides offering a textured surface similar to that of a sand casting.

[0090] Subsequent to impregnation, the washability was tested on the basis of the amount of remaining open threads subsequent to impregnation. The open threads were measured using a certified thread gage for determining open threads. The results of washability tests are shown in Figure 2. As shown in this figure, the inventive Composition A exhibited a significantly higher open thread percentage (over 90%). In contrast, the comparative Compositions B-D demonstrated 67% or less of the threaded holes remained opened, i.e. unblocked by cured impregnant.

[0091] Although the invention has been described with reference to specific aspects, features and embodiments, it will be appreciated that the invention is not so limited, and that other modifications, variations and embodiments are within the scope of the disclosure and the spirit of the claims.

Claims

WHAT IS CLAIMED IS:

1. An anaerobic sealant composition comprising: a) a (meth)acrylate component comprising a mono(meth)acrylate and multi(meth)acrylate, at least about 90% of said (meth)acrylate component being polar-group functionalized; and b) an anaerobic cure-inducing composition; wherein said polar group is a member selected from the group consisting of hydroxy, amino, cyano, halogen, a heterocyclic ring, alkoxy and combinations thereof.

2. The anaerobic sealant composition of claim 1, wherein said (meth)acrylates component comprises at least 50% by weight of the total composition and further comprises up to about 98% of the total composition.

3. The anaerobic sealant composition of claim 1, wherein composition provides at least 90%o sealability on porous metal parts and at least 50% washability from threaded cavities present in said porous metal part subsequent to anaerobic cure-inducing conditions.

4. The anaerobic sealant composition of claim 1, wherein polar group-functionalized (meth)acrylate is a member selected from the group consisting of alkoxy-functionalized mono- (meth)acrylates, alkoxy-functionalized multi-(meth)acrylates and combinations thereof.

5. The anaerobic sealant composition of claim 1 , wherein said polar group functionalized (meth)acrylate is a member selected from the group consisting of hydroxy functionalized mono- and multi-(meth)acrylates.

6. The anaerobic sealant composition of claim 1, wherein said polar group functionalized (meth)acrylate has a water solubility of about 10% or greater.

7. The anaerobic sealant composition of claim 1, wherein said polar group functionalized (meth)acrylate is a member selected from the group consisting of hydroxy ethyl (meth)acrylate, hydroxy propyl (meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, butyleneglycol di)meth)acrylate, bis(methacryloxyethyl)phosphate, 1 ,4-butanediol di(meth)acrylate trimethylol propane di(meth)acrylate, and combinations thereof.

8. The anaerobic sealant composition of claim 1, wherein said mono(meth)acrylate component conforms to the structure

H₂C=CGCO₂R

wherein G may be hydrogen, halogen or alkyl of 1 to about 4 carbon atoms, and R may be selected from alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkaryl, aralkyl or aryl groups of 1 to about 16 carbon atoms, any of which may be optionally substituted or interrupted with silane, silicon, oxygen, halogen, carbonyl, hydroxyl, ester, carboxylic acid, urea, urethane, carbamate, amine, amide, sulfur, sulfonate, sulfone and the like.

9. The anaerobic sealing composition of claim 1, wherein said multi(meth)acrylate component conforms to the structure

wherein R⁴ represents a radical selected from the group consisting of hydrogen, lower alkyl of from 1 to about 4 carbon atoms, hydroxyalkyl of from 1 to about 4 carbon atoms, and

R³ is a radical selected from the group consisting of hydrogen, halogen, and lower alkyl of from 1 to about 4 carbon atoms; R⁵ is a radical selected from hydrogen, hydroxyl, and

O

II — O— C— C=CH₂ R ! ₃ ³

m may be 0 to 12, and p is 0 or 1 .

10. The anaerobic sealant composition of claim 1, further comprising a surfactant.

1 1. The anaerobic sealant composition of claim 7, wherein said surfactant is functionalized with polar groups selected from the group consisting of, hydroxy, amino, cyano, halogen, a heterocyclic ring, alkoxy and combinations thereof.

12. The anaerobic sealant composition of claim 1, wherein said anaerobic cure-inducing composition comprises a peroxide.

13. An anaerobic sealant composition comprising: a) at least about 60% by weight of a polar group-functionalized mono(meth)acrylate; b) at least about 5% by weight of a polar group-functionalized multi(meth)acrylate; and c) an anaerobic cure-inducing composition.

14. The anaerobic sealant composition of claim 13, wherein said sealant composition exhibits at least 90% sealability on porous metal parts and at least 50% washability from precision holes present on said porous metal part subsequent to anaerobic cure-inducing conditions.

15. The anaerobic sealant composition of claim 13, further comprising a surfactant.

16. The anaerobic sealant composition of claim 13, further comprising a cure accelerator.

17. The anaerobic sealant composition of claim 13, wherein said (meth)acrylate component is functionalized with a polar group selected from a group consisting of hydroxy, amino, cyano, halogen, a heterocyclic ring, alkoxy and combinations thereof.

18. The anaerobic sealing composition of claim 13, wherein said mono(meth)acrylate component conforms to the structure

H₂C=CGCO₂R

19. The anaerobic sealant composition of claim 13 wherein said multi(meth)acrylate conforms to the structure

m maybe 0 to 12, and p is 0 or 1.

20. An anaerobic sealant composition comprising: the reaction product of (i) at least about 60% by weight of a polar group-functionalized mono(meth)acrylate; at least about 5% by weight of a polar group-functionalized multi(meth)acrylate; and (ii) an anaerobic cure-inducing composition; wherein said polar functionalized-group is selected from the group consisting of hydroxy, amino, cyano, halogen, a heterocyclic ring, alkoxy and combinations thereof

21. An anaerobic sealant composition comprising: the reaction product of(i) a (meth)acrylate component comprising a mono(meth)acrylate and a multi(meth)acrylate, at least about 90% of said (meth)acrylate component being polar group-functionalized; and (ii) an anaerobic cure- inducing composition; wherein said polar functionalized-group is selected from the group consisting of hydroxy, amino, cyano, halogen, a heterocyclic ring, alkoxy and combinations thereof.

22. A method of making an anaerobic sealant composition having improved washability comprising the step of combining (i) a (meth)acrylate component comprising about 60% by weight of a polar group-functionalized mono(meth)acrylate and at least about 5% of a polar functionalized multi(meth)acrylate; and (ii) an anaerobic cure-inducing composition.

23. A method of impregnating a porous part comprising:

(i) providing an anaerobic impregnation composition comprising: a) a combination of mono(meth)acrylate and multi(meth)acrylate components, at least about 90% of said combination being a polar group- functionalized methacrylate; and b) an anaerobic cure-inducing composition;

(ii) submersing a porous part in the anaerobic impregnation composition under wet or dry vacuum conditions to permit filling of the pores with said composition;

24. A method of making an anaerobic sealant composition having improved water washability comprising the step of combining a (meth)acrylate component comprising a mono(meth)acrylate and a multi(meth)acrylate, at least about 90% of said (meth)acrylate component having polar group functionality, and an anaerobic cure-inducing composition.

25. A method of testing the washability of an impregnation composition comprising the steps of: a) providing a test apparatus comprising a body having at least two opposing surfaces, at least one of said surfaces including one or more dimensionally predetermined cavities being defined by a wall cavity and a depth and said cavity wall being capable of being surface-coated with an impregnation composition, said body being adapted for the determination of the amount of surface coating remaining subsequent to exposure to cure conditions followed by water-washing; b) immersing said test apparatus in an impregnation composition under cure- inducing conditions; such that said composition enters said cavities; c) washing said test apparatus in aqueous medium; and d) comparing the portion of said cavity having cured sealant composition remaining thereon with the portion of said cavity which has no sealant composition thereon.

26. The method of claim 25, wherein said machined holes are threaded.

27. The method of claim 25, wherein said washing comprises oscillating said test apparatus in and out of said aqueous medium.

28. The method of claim 27, wherein said oscillating comprises a predetermined number of oscillations in a given time and the stroke distance of each oscillation.

29. The method of claim 25, further comprising the step of centrifuging to remove excess sealant composition said test apparatus prior to washing.

30. The method of claim 25, wherein determining the amount of said machined hole which is unobstructed comprises the use of a thread gauge.

31. An apparatus for determining the washability of an impregnation composition, said apparatus comprising a body having at least two opposing surfaces, at least one of said surfaces including one or more dimensionally predetermined cavities being defined by a cavity wall and a depth and said cavity wall being capable of being surface-coated with an impregnation composition during an impregnation process, said body being adapted for the determination of the amount of surface coating remaining subsequent to exposure to cure conditions followed by water- washing, whereby the washability of said impregnation composition is determined by comparing a portion of the cavity wall having impregnation composition remaining thereon with a portion of the cavity wall which has no composition remaining thereon.

32. The anaerobic sealant composition of claim 1, wherein said polar group functionalized mono(meth)acrylate is present in at least about 60% by weight; and further present in amounts up to about 95% by weight.

33. The anaerobic sealant composition of claim 1 wherein said polar group-functionalized multi(meth)acrylate is present in at least about 10% by weight; and further present in amounts up to about 20% by weight;

34. The anaerobic sealant composition of claim 13 wherein said polar group functionalized mono(meth)acrylate is present in amounts of at least about 80% by weight and said polar group- functionalized multi(meth)acrylate is present in amounts of at least about 10% by weight .

35. The anaerobic sealant composition of claim 20 wherein said polar group functionalized mono(meth)acrylate is present in amounts of at least about 80% by weight and said polar group- functionalized multi(meth)acrylate is present in amounts of at least about 10% by weight.

36. The anaerobic sealant composition claim 21 wherein said polar group-functionalized mono(meth)acrylate is present in amounts of at least about 80% by weight and said polar group- functionalized multi(meth)acrylate is present in amounts of at least about 10% by weight.

37. The apparatus of claim 31 , wherein said body further includes an attachment site comprises a threaded attachment cavity found in said body for threadably engaging with an oscillating device.