GB2111515A - Method of forming gaskets using a UV-and anaerobically- curable gasketing composition - Google Patents

Abstract

In the formation of gaskets a liquid gasketing material comprising monomer, UV initiator and peroxy initiator is partially pre-cured by ultraviolet exposure in situ on a flange. The partially cured gasket is then mated with another surface and further cured anaerobically to produce an adequate gasket and sealant. The method is adaptable for high speed production-line techniques to be applied on a variety of flange shapes and sizes. The invention also relates to a composition suitable for gasketing, which combines UV and anaerobic curing capability, and the monomer component of which comprises a compound selected from certain, defined diacrylate-terminated esters.

Description

SPECIFICATION Method of forming gaskets This invention relates to a method of forming gaskets.

The assembly and sealing of metal and other parts with chemical adhesives and sealants has become an important production and maintenance tool in modern industry. One area of present interest is the joining and sealing of mating surfaces, by means of a chemical gasket.

A gasket is a sealing member of relatively soft material intended to be placed between a pair of mating surfaces, usually flanges, of components of relatively harder material to assist the coupling of components by making the joint between them leakproof. The joint is effected by pressing the surfaces together with some force to conform the gasket to the surfaces. Most gaskets are cutouts from laminar material such as paper, cork, rubber or various fibre compositions, and are non-adhesive in operation.

Because of the considerable number of flange shapes used in industry today, the number of different types of preformed gaskets which must be made available is very large indeed. Problems generally encountered with these traditional gaskets involve relaxation of the gasket material, distortion, tearing or simple shrinkage thereof, all of which may cause the construction to leak, either through the gasket material itself or at the flange interface.

In recent years, the use of liquid gaskets has grown because of convenience features, reliable performance and the elimination of the need to hold a large inventory of different types and shapes of preformed gaskets. The liquid gasket is often applied as a paste or high viscosity grease from a tube onto one or both of the surfaces before mating of the surfaces.

Two main types of liquid gaskets are used in industry today. One type of liquid gasket is noncuring and depends on the deposition of a polymer onto the flange by evaporation of the solvent from a solution. A simple seal is formed when the two flanges are brought together. A physical separation rather than a chemical reaction occurs when the gasket is applied. This type of liquid gasket suffers from low resistance to high temperature, to water penetration and to chemicals, and from an inability to withstand continuous vibration.

The second type of liquid gasket is the curing gasket. A chemical reaction takes place to change the applied material from the liquid state into a solid cross-linked high-temperature-resistant thermoset plastic substance. Normally these products do not contain solvents and are applied to the flange as a thick paste or gell which subsequently cures, by chemical reaction, to a solid thermoset material. Two of the most commonly used curing types of liquid gaskets are the silicone RVT products and the anaerobic products. The silicone products depend on moisture to initiate the chemical crosslinking reaction.

Anaerobic adhesives are generally considered as the class of adhesives which are inhibited by the presence of oxygen and whose polymerization into a solid thermoset material is allowed to proceed spontaneously by the exclusion of oxygen; for example, when the anaerobic composition is confined between adjacent non-porous surfaces.

The resin monomers used in anaerobic compositions are generally mono- and poly-acrylic acid esters and derivatives thereof, wherein the non-acrylate portion of the ester normally contains an activating group which serves as a potential reaction site for the polymerization reaction.

Polymerization occurs via free radical initiation, propagated by a peroxy free radical initiator. Free radical polymerization initiators are also well known in the art and include a wide range of organic and inorganic compounds, all of which function in a similar capacity when present in the monomer. A composition comprising an acrylate ester and suitable peroxy or perester initiator will demonstrate the anaerobic cure characteristics described above. Anaerobic-curing gasketing material are already known in the art and described in detail in U.S. patents No. 3,547,851 and No. 3,625,875. These anaerobic gasketing materials are not effective in curing through large gaps between faying surfaces, nor are they capable of functioning as spacers. They also cannot easily be moved for storage once applied to a flange without disturbing the material.

A variety of accelerators, inhibitors, primers and resin systems are regularly employed in anaerobic systems to provide a variety of application possibilities. The cure rates of these systems are functions primarily of environment, adhesive compositions and type of substrate. Increases in temperature during cure will normally further accelerate polymerization, while the converse is expected for temperature decreases. These anaerobic types of compositions have been described in detail in U.S.

Patents No. 2,895,950; 3,218,305 and No. 3,425,988 among others.

As stated previously, the silicone products depend on atmospheric moisture to initiate the curing reaction. A serious problem using silicone products for gasketing is the lack of complete curing of the liquid across wide flanges due to the fact that moisture from the atmosphere can only penetrate across the narrow gap for a short widthwise distance. Alternatively, the silicone once applied can be allowed to cure by exposure to atmospheric moisture before the flange faces are clamped together, but this takes considerable time and periods of one or two hours are often required before adequate curing is achieved and the parts can be put together. The use of silicones, therefore, may require a considerable time lapse between putting the parts together and being able to test the construction to determine if adequate sealing has been obtained.Silicones are often difficult to apply because of their sensitivity to moisture and normally have to be applied by caulking gun or tracer techniques which are difficult to operate on high speed production lines.

It is well known in the art that anaerobic compositions make use of the exclusion of oxygen from the composition to promote curing of the liquid products. Since the generation of the free radicals which initiate cure in these products is sometimes dependent on a redox-type reaction, the products will cure at various rates according to the type of metal surface they are in contact with. The effect of the speed at which the seal is formed in any gasketing operation depends, to a large extent, on the type of metal being used (if any), the roughness of the surface, the temperature and whether or not an accelerator was included. It will be appreciated that since the metal surface plays a role in the initiation of cure, the rate at which the cure proceeds will also depend to some extent on the thickness of the anaerobic film of material.The products are therefore slow to cure through gaps of greater than about 0.25 mm. Large gaps between parts to be bonded with anaerobic compositions also expose the composition, particularly the bondline area, to air (oxygen) which inhibits the cure. Thus, a large enough gap would have the double effect of oxygen inhibition and lack of metal surface initiation.

There is always a need for anaerobic gaskets which are capable of curing through gaps of more than 0.25 mm and which adequately perform the sealing and adhesive functions of a gasket.

Many gasketing applications require the gasket to function as a spacer. This feature allows for compression to be built up at the joint. Presently, conventional liquid chemical gaskets are not capable of withstanding compression in the uncured state.

As explained above, many anaerobic gaskets are not capable of fully curing in large gaps (more than about 0.25 mm) and cannot function as spacers.

The present invention provides a method of forming a gasket which comprises: (a) applying a layer of a UV-curable fluid comprising a monomer, a UV initiator and a peroxy initiator to at least one of two faying interfaces; (b) causing the layer to partially cure by exposing it to an effective amount of UV radiation, to obtain a greasy and/or tacky surface; (c) placing the partially cured layer in contact with the other faying interface; and (d) allowing said layer of fluid surface to further cure anaerobically, thereby sealing the faying interfaces together.

The present invention represents a significant advance over the use of the previous anaerobic gasket types as described above by providing a means for forming gaskets which can be stored in situ on the flange applied by high speed production-line techniques to nearly any flange shape and size. The method can provide a gasket which adheres strongly enough to the flange to remain undisturbed during storage and handling, but allows for removability if required.

According to the invention a layer of an ultraviolet curable fluid composition is applied to at least one of the surfaces to be joined and the layer is caused to partially cure by exposing it to suitable radiation. It is preferred to apply the composition layer to only one of the surfaces to be joined, since this produces an adequate gasket unless the surfaces are very rough.

The invention also provides a mechanical engineering component having a jointable or coupleable surface bearing a gasket formed by the method recited above. The invention further provides a coupled pair of components at least one of which bears a gasket as recited above, and it provides likewise a coupled pair of components containing a gasket formed by the method recited above.

The present invention also provides a gasketing composition comprising: (a) at least one of certain monomers defined hereinafter; (b) a UV initiator, (c) a peroxy initiator, in concentrations from about 0.1% to about 10% by weight, (d) a free radical polymerization accelerator, and (e) an inhibitor, said composition being capable of at least partial cure on exposure to UV radiation and also being anaerobically curable.

It is preferred. in carrying out the method according to the invention in factory production conditions, to apply the layer of composition to the jointable surface by a known high-speed technique, such as by screen printing. When this is done, the irradiation with ultraviolet light is preferably carried out at a different location where stray ultraviolet light rays cannot accidentally affect the unused composition in the screen printing apparatus and therearound.

It is well known in the art that ultraviolet initiation continues only so long as the ultraviolet light is kept on the ultraviolet-sensitive material. Once the light is removed, the ultraviolet polymerization ceases immediately. A feature of the instant composition is that it continues to cure anaerobically when confined without air (oxygen), i.e., as when between coupleable surfaces. One way the amount of UV cure the gasket composition undergoes can be regulated is by varying the UV radiation and the exposure time to said radiation. Thus, one way the extent of UV initiated polymerization can be controlled is in this manner. Numerous UV curing effects (degrees of cure) can be achieved, ranging from a soft, gell-like material to a more firm (and therefore more cured) material, with the surface on any range being tacky or greasy. "Tacky" means the surface will be "stringy" to the touch. Thus, upon fingertip touching, the material will stick to the finger enough to string along when the finger (or object) is lifted. "Greasy" means the surface is wet to the touch and gives a greasy appearance.

One extreme would be to allow the composition to receive enough UV radiation to cure a firm or hard but flexible material. As indicated above, such a cure would serve as a spacer and could sustain the compression force exerted by the coupled parts between which the composition is placed.

Alternatively, another extreme might be to irradiate the composition only slightly, which would result in a soft, gell-like consistency, not firm enough to sustain compressive force, yet cured enough to be moved or stored undisturbed. "Gel I-like" is to connote a gelatine-like consistency or appearance.

It is possible, with the appropriate irradiation, to obtain partially cured composition with a firm interior and a tacky exterior or surface. In fact, normally this is the preferred effect. The tacky surface will further cure anaerobically when confined without air (oxygen), such as when placed between two faying surfaces, thereby sealing the surfaces together.

As one can observe, there are numerous combinations of effects that can be obtained from the initial partial UV cure, which can be modeled to a particular application.

Fluid compositions usable in carrying out the method of the invention have been broadly defined above; they are further characterized by the fact that all of them comprise, as the major or polymerizable constituent, at least one monomer (in the conventional sense, common in the art, which uses the word to include oligomers) having acrylate, preferably methacrylate terminated portions in the molecule. Of particularly utility as adhesive monomers are polymerizable di- and other polyacrylate esters since, because of their ability to form cross-linked polymers, they have more highly desirable structural properties. However, monoacrylate esters can be used, particularly if the non-acrylate portion of the ester contains a hydroxyl or amino group, or other reactive substituent which serves as a site for potential cross-linking.Examples of monomers of this type are hydroxyethyl methacrylate, hydroxypropyl methacrylate, cyanoethyl acrylate, t-butylaminoethyl methacrylate, glycidyl methacrylate, cyciohexyl acrylate and furfuryl acrylate. Inhibitors of the quinone type, well known in the art, may be used in the compositions, as well as various sulphimide or amine accelerators and initiators of the peroxy and perester type. The compositions normally also comprise known composition thickeners, and optionally contain plasticizers of the formed gasket. The concentrations of the peroxy type initiators (herein defined to include perester initiators) are generally from about 0.1% to about 10% by weight of the composition. Hereinafter "by weight" means by weight of the composition.The preferred amount is not more than about 5% by weight of the composition and the most preferred amount between 0.2% to 3% by weight. The accelerators are generally employed in concentrations of less than 1 0% by weight of the composition, with good results occurring in the range of about 0.05% to about 0.1% by weight. The preferred range however is 0.1% to 0.75% by weight. Sulphimides have been found to be effective in trace amounts, e.g. about 0.01% or in amounts up to about 10% by weight. They are utilized with a preferred range being from 0.1% to 2% by weight. The amount of quinone inhibitor will vary with the amount of accelerator added.An effective range for the inhibitor is between 10 parts per million to about 1 ,000 parts per million, with the preferred range being from 200 to 600 parts per million as the accelerator amount increases from 0.1% to 1.0% by weight. The amount of thickness and plasticizers will vary depending on the desired properties and would be easily determined by one skilled in the art. In all cases, the compositions contain at least one free radicalforming polymerization initiator or initiation system which is activatable by exposure to ultraviolet light, in the sense that only when so exposed does it produce a sufficiency of free radicals to start rapid partial polymerization of the monomer, and at least one free radical initiator of the peroxy or perester type to initiate the anaerobic polymerization.

Compositions suitable for employment in the process of the present invention have been disclosed in U.S. Patent Application No. 356,679 to O'Sullivan, filed May 2, 1973, now abandoned, particularly in Example 3 thereof. The compositions of Examples 1, 2 and 4 if suitably thickened, would also be suitable. Typical monomers useful in those polymerizable compositions have the general formula of (CH2=CR2 . CO .0. R7 .O. CO . NK47R4 wherein R2 is H, CH3, C2H5 or Cl, R4 is a C2--20 alkylene, alkenylene or cycloalkenylene radical or a C640 arylene, alkarylene, aralkarylene, alkyloxyalkylene or aryloxyarylene radical which may be substituted by 1-4 chlorine atoms or by 1-3 amino or mono- or di-C~3 alkylamino or C13 alkoxy groups.R7 is one of the following less one hydrogen atom: (a) a C18 hydroxy alkyl or aminoalkyl group, (b) a C16 alkylamino-C,~8 alkyl group; or (c) a hydroxyphenyl, an aminophenyl, a hydroxynaphthyl or an aminonaphthyl group which may be further substituted by an alkyl, alkylamino or dialkylamino group, each alkyl group in this sub-part (c) containing up to about 3 carbon atoms. Of these, the preferred compositions contain either monomer A, of formula

or monomer B, of formula

or both, (PR represents a propylene triol oligomer residue).

Other suitable compositions contain the polymerizable monomers disclosed in U.S. Patent No.

3,425,988. These monomers may be generally characterized as polyurethanes and polyureides (also called polyureas). They may be formed from organic polyisocyanates and they have terminal acrylate (including methacrylate) radicals and at least two bivalent urethane or ureide groups linking the terminal radicals, the number of terminal radicals in the monomer never exceeding the number of urethane or ureide groups. These monomers may be represented by the general formula I (A-X-CO.NH+B wherein X is -0-or -NR1 ; R' is selected from the group consisting of H or lower alkyl groups of 1 to 7 carbon atoms; A is CH2=CR2. CO . 0--; R2 is H or CH3; n is an integer from 2 to 6 inclusive; and B is a polyvalent substituted or unsubstituted alkyl, alkenyl, cycloalkyl, aryl, aralkyl, alkaryl, alkyloxyalkylene, aryloxy-arylene or heterocyclic radical. For example, in one group of such monomers n is 2, X is --OO-, R2 is CH3, and B is an alkoxyalkylene (polyether) radical. Each member of the group is the reaction product of 2-hydroxyethylmethacrylate and a selected difunctional linear isocyanateterminated polyether prepolymer. A preferred difunctional prepolymer is marketed under the trademark Castomer E-002 by Witco Chemical Corporation, of 400 N.Michigan Avenue, Chicago, Illinois 6061 1, U.S.A. This substance is reacted with 2-hydroxyethylmethacrylate to give a preferred member of said group, hereinafter referred to as monomer C.

Further suitable compositions contain polymerizable monomers disclosed in U.S. Patent No.

3,218,305, of general formula II

wherein R3 is H, C14 alkyl or hydroxyalkyl or R5OCH2-; R6 is.H, halogen or C14 alkyl; R4 is H, OH or R50; R5 is CH2=C(R6)C(=O)-; m is an integer, preferably 1 to 8; k is an integer preferably 1 to 20; and p is 0 or 1. Examples of some preferred monomers of this general formula II are diethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, diglycerol tetramethacrylate, trimethylol propane triacrylate, to name a few.

Other suitable compositions contain polymerizable monomers described in U.S. Patent 4,018,851, of general formula Ill

where RB is selected from the class consisting of hydrogen, chlorine, and methyl and ethyl radicals; R7 is a bivalent organic radical selected from the group consisting of lower alkylene of 1-8 carbon atoms, phenylene, and naphthylene; W is a polyisocyanate radical; E is an aromatic, heterocyclic or cycloaliphatic polyol or polyamine radical, preferably a diol, and more preferably a diol of a cycloaliphatic compound; d is either 1 or 0; i is 0 when d is 0, and otherwise is equal to one less than the number of reactive hydrogen atoms of E; Z is a polymeric or copolymeric grafted alkylene ether polyol radical; z is an integer equal to the valency of Z; and an asterisk indicates a urethane (-NH- CO-O-) or ureide (-NH-CO-NH-) linkage. Z may also be a polymeric or copolymeric methylene ether polyol radical, giving a group of polymerizable monomers disclosed in a related U.S. Patent No.

3,993,815.

The compositions in the present invention also contain an ultraviolet-activatable polymerization initiator. These UV initiators are generally employed in concentrations from about 0.1% to about 10% by weight of the composition. The initiator is selected from (i) C3B straight and branched chain alkane diones, and (ii) carbonyl compounds of the general formula R9 . CO-R10 wherein R9 and R , which may be the same or different, are selected from alkyl and aralkyl radicals and amino and mono- and di C,-6 alkylamino derivatives thereof, said radicals being optionally alpha-substituted by at least one alkoxy or aryloxy radical, aryl radical, or alkaryl radical; in which R9 may in addition be hydrogen; and in which R9 and R10 taken together with the carbonyl group to which they are attached, may represent an aromatic or heterocyclic ketone containing up to 1 6 carbon atoms, wherein the ketone carbon atom forms part of the aromatic or heterocyclic ring system. Preferred polymerization initiators are acetophenone, benzophenone and 1- and 2-acetonaphthone. Others are 2,3-butadione, 2,4-dimethyl3-pentanone, 1- and 2-naphthaldehyde, p-phenylacetophenone, n-propionophenone, fluoren-9-one, xanthen-9-one and 4,4'-bis-dimethylaminobenzophenone. The preferred metal carbonyls are Mn2(CO),0Fe(CO)5, and Re2(CO)10. Others are Cr(CO)6, Co2(CO)8, Ni(CO)4 and Mo(CO)6.

Further, ultraviolet-irradiation-initiated polymerizable fluid resins other than disclosed herein, may be useful in the present invention. In order that a gasket may have an appropriate thickness after partial curing, however, it is desirable that the liquid composition can be applied to a desired thickness on a surface without spreading or running, and this implies a certain minimum viscosity for a given application. Likewise, the use of special techniques, such as screen printing, for applying the compositions, implies a maximum working viscosity above which the technique becomes unacceptably difficult to use. These viscosity limits can easily be discovered in each case by those skilled in the art with a minimum of trial and error.

In use, a gasket composition according to the invention is applied, by means of stenciling techniques, caulking gun, squeezing from tube, or screen printing, to one member of the flange pair of an intended jointed construction to a thickness predetermined by the gasket thickness required. The preferred methods are automated techniques such as stenciling and screen printing, screen printing being the most preferred. The coated parts are conveyed to a curing station where the applied material is irradiated with an appropriate dose of ultraviolet rays. Cure takes place in 10 seconds to 3 minutes as a rule. The gasket is now a solid thermoset material with sufficient elasticity and plastic deformability to effect a good seal when the coated part is mated with the other member of the pair of parts to be coupled.Assembly of the joint may, if desired, be effected at a later time and in a different place, the coated part being transferred to storage in the meantime.

The invention will be appreciated in greater detail from the following description of specific embodiments thereof, given by way of example only. Examples 1-3 are intended only to show the UV aspects of the gasketing material. Example 4 shows that gasketing material which uses only the anaerobic feature is not suitable for sealing large gaps between faying surfaces. Example 5 demonstrates the improved gap-filling capability when the gasketing formulation is initially partially cured by UV light prior to further cure anaerobically. Example 6 further demonstrates the unique effectiveness of the instant invention.

Example 1 A formulation containing 87.40 parts of monomer C (as stated above), 9.70 parts of tetraethylene glycol di(di-ethyl hexoate), 0.96 parts of benzoin isobutyl ether and 1.94 parts of cumene hydroperoxide was prepared by blending the constituents together to yield a homogeneous composition. A thick (2--4 mm) bead of this composition was placed on a flat surface.

The bead was subjected to 10,000 UW/CM2 of ultraviolet irradiation from a Philips Ml 3/U-400 watt lamp (measured by a Blak-ray model J-22 1 ultraviolet meter) for two (2) minutes.

After the treatment, the bead had cured through its thickness and was flexible. This composition was judged to be suitable for the preparation of gaskets.

Example 2 A formulation was prepared from 79 parts of monomer C, 19.80 parts of tetrahydrofurfuryl methacrylate and 1.2 parts of 2,2'-di-methoxy-2-phenyl acetophenone. The composition was blended together, and a bead of 0.8 mm thickness was applied to a stainless steel hydraulic cell by means of a stencil. The composition was irradiated at 6,000 UW/CM2 for three (3) minutes.

The steel cover of the hydraulic cell was then placed over the gasket and secured by four bolts torqued down to 275 kgcm.

The cell was filled with hydraulic oil and pressurized by means of a hydraulic pump in increments of 14.06 kg/cm2 (200 psi). The gasket sustained a test pressure of 140.6 kg/cm2 (2000 psi).

Example 3 Using a "silk" screen of polyester with mesh opening of approximately .203 mm (0.008 inches) a layer 0.5 mm thick of the composition of Example 2 was applied to the flange of a hydraulic cell. The screen had previously been printed with an impervious coating so that the liquid gasketing material passed only through that part of the screen corresponding to the flange shape.

The screen was removed and the liquid material irradiated at 6,000 UW/CM2 for five (5) minutes.

The partially cured material was firm with a tacky surface. The top plate of the hydraulic cell was placed over the cured gasket and secured by four bolts torqued down to 300 kgcm.

Pressure was applied to the interior of the hydraulic cell in increments of 14.06 kg/cm2 (200 psi) until the gasket developed a leak at 140.6 kg/cm2 (2000 psi). The gasket material was examined and its thickness around the flange was found to vary from 0.5 to 0.9 mm. These characteristics are acceptable for a satisfactory gasket.

Example 4 A formulation was prepared from the following ingredients: Parts by weight monomer C 60.0 co-monomers and reactive diluents 30.0 accelerators 1.2 cumene hydroperoxide 1.0 O-benzoic sulphimide 1.8 2,2'-dimethoxy-2-phenyl acetaphenone 2.0 p-benzoquinone 0.022 chelators 1.95 A 1 mm thick bead of the above formulation was put onto a flange of a pressure cell. The cell was then covered and torqued down without undergoing any UV exposure. After ninety (90) hours, the material failed to form an effective seal and it sustained no hydraulic pressure when tested. This is evidence of the necessity of the combined UV and anaerobic curing systems. As mentioned earlier, anaerobic curing systems do not cure well through large gaps because of the considerable amount of air exposure the bondline area receives by virtue of the gap.

Example 5 A bead using, the formulation of Example 4 was UV-cured at 6,000 UW/CM2 for five (5) minutes on an open flange. The bead was a gell-like consistency with a greasy and tacky surface. The flange cover was then torqued down and the cell pressurized immediately. The seal sustained 90 kg/cm2 oil pressure before leaking.

The above examples demonstrate the improved gap-filling capability of the instant formulations which are attributed to the initial partial cure by ultraviolet photolysis. It is noted in Example 4 that the composition has both ultraviolet and anaerobic characteristics and hence will not cure through large gaps (i.e. 0.5-1 mm) without first partially curing the material with ultraviolet light. It is well known in the art that anaerobic compositions presently are limited in their gap-curing capabilities because they are stabilized by air (oxygen). The larger the gap between two parts to be sealed, the more air exposure the adhesive receives through the bondline area.

Example 6 The following Example serves to further demonstrate the anaerobic nature of the composition.

A formulation comprising 75.53 parts by weight of monomer C, 18.92 parts by weight of tetrahydrofurfuryl methacrylate, 1.11 parts by weight of 2,2'-dimethoxy-2-phenyl acetophenone, 2.22 parts by weight of acrylic acid and 2.22 parts by weight of gamma-glycidoxy-propyltrimethoxy silane, both adhesion promoters, was blended together to yield a homogeneous composition.

On two separate rectangles of plate glass (50 mmx 50 mmx5 mm) a layer 0.5 mm thick of the composition was spread. The coated glass pieces were then exposed to ultraviolet light at an intensity of 5,000 UW/CM2 for 1 minute, partially curing the gasketing composition.

One circular end of a 1 cm diameter cylinder of steel was pressed firmly against the partially cured composition layer on one of the glass rectangles for 24 hours. The other layer on the other glass rectangle was similarly treated with a second 1 cm diameter steel cylinder.

After that time, the force required to pull the steel cyclinders axiaily away from the glass was measured and found to be 34 and 31 pounds, respectively, for the two bonds. It must be emphasized that no immediate bond strength is observed between the steel cylinder and the above composition.

They must be left in contact long enough to effect an anaerobic cure and develop any significant bond strength.

It is evident from the examples that the unique combination of steps involving ultraviolet and anaerobic properties is an improved method and of considerable value in overcoming traditional precut and liquid gasket problems.

Claims (30)

Claims

1. A method of forming a gasket which comprises: (a) applying a layer of a UV-curable fluid comprising a monomer, a UV initiator and a peroxy initiator to at least one of two faying interfaces; (b) causing the layer to partially cure by exposing it to an effective amount of UV radiation, to obtain a greasy and/or tacky surface; (c) placing the partially cured layer in contact with the other faying interface; and (d) allowing said layer of fluid surface to further cure anaerobically, thereby sealing the faying interfaces together.

2. A method as claimed in Claim 1 wherein the UV-curable fluid contains at least one polymerizable acrylate ester monomer.

3. A method as claimed in Claim 2 wherein the monomer is the reaction product of 2hydroxyalkyl-methacrylate and a linear difunctional isocyanate-terminated polyether prepolymer.

4. A method as claimed in Claim 2 wherein the monomer is represented by the formula: (A-X-CO . NH#nB wherein X is --OO- or --NR1; R1 is hydrogen or a lower alkyl group of 1 to 7 carbon atoms; A is CH 2=CR2 . CO . 0--; R2 is H or CH3; n is an integer from 2 to 6 inclusive; and B is a polyvalent substituted or unsubstituted alkyl, alkenyl, cycloalkyl, aryl, aralkyl, alkyloxy-alkylene, aryloxy-arylene or heterocyclic radical.

5. A method as claimed in Claim 2 wherein the monomer may be represented by the formula:

wherein R3 is H, C14 alkyl or hydroxyalkyl or R5OCH2-; RB is H, halogen or C14 alkyl; R4 is H, OH or R6O ; R5 is CH2=CR6C=O-; m is an integer, preferably 1 to 8; k is an integer, preferably 1 to 20; and p is O or 1; or

wherein RB is hydrogen, chlorine, methyl or ethyl; R7 is a bivalent organic radical selected from the group consisting of lower alkylene radicals of 1-8 carbon atoms, phenylene, and naphthylene; W is a polyisocyanate radical;E is an aromatic, heterocyclic or cycloaliphatic polyol or polyamine radical; d is either 1 or 0; i is 0 when d is 0, and otherwise is equal to one less than the number of reactive hydrogen atoms of E; Z is (i) a polymeric or copolymeric grafted alkylene ether polyol radical or (ii) a polymeric or copolymeric methylene ether polyol radical; z is an integer equal to the valency of Z; wherein an asterisk indicates a urethane (--NHH-CCOO-O-) or ureide (-NH-CO-NH-) linkage.

6. A method as claimed in Claim 2 wherein the polymerizable acrylate ester monomer has either the formula:

where PR represents a propylene triol oligomer residue.

7. A method as claimed in any of Claims 1 to 6 wherein the peroxy initiator is an organic hydroperoxide, present in a concentration from about 0.1% to about 10% by weight.

8. A method as claimed in any of Claims 1 to 6 wherein the peroxy initiator is a perester, present in a concentration from about 0.1% to about 10% by weight.

9. A method as claimed in any of Claims 1 to 8 wherein the ultraviolet initiator is (a) a CX to C6 alkyl dione; (b) a metal carbonyl of the formula MX(CO)y wherein M is a metal atom, x is 1 or 2, and y is an integer determined by the total valence of the metal atoms; or (c) a carbonyl compound of the general formula R9(CO)Rr0 wherein R9 is an alkyl, aryl, aralkyl or alkaryl group containing up to about 10 carbon atoms, and RB is R10 or hydrogen; or R9 and R'O taken together with the carbonyl group form an aromatic or heterocyclic ketone containing up to about 1 6 carbon atoms.

10. A method as claimed in any of Claims 1 to 9 wherein the UV polymerisation initiator is present in concentrations from about 0.1% to about 10% by weight and is acetophenone, benzophenone or 1- or 2-acetonaphthone.

11. A method as claimed in any of Claims 1 to 10 wherein the UV-curable fluid contains a free radical polymerization accelerator.

12. A method as claimed in Claim 11 wherein the accelerator is a heterocyclic secondary amine wherein the heterocyclic ring is hydrogenated, an N,N-dialkyl aryl amine or an N,N-dialkyl substituted aryl amine wherein the substituents are one or more lower alkyl radicals of 1 to 4 carbon atoms, the number of said substituents being at least two when one of said substituents is in the ortho position.

13. A method as claimed in Claim 11 wherein the accelerator is an organic sulphimide.

14. A method as claimed in Claim 1 3 wherein the sulphimide is benzoic sulphimide.

1 5. A method as claimed in any of Claims 1 to 14 wherein the UV-curable fluid contains an inhibitor which is a benzoquinone, naphthoquinone, phenanthraquinone, anthraquinone or a substituted derivative of any of the foregoing.

16. A method as claimed in Claim 1 5 wherein the UV-curable fluid contains an inhibitor consisting of benzoquinone.

17. A method as claimed in any of Claims 1 to 16 wherein the said other faying interface is coated with an accelerator.

18. A method as claimed in any of Claims 1 to 17 wherein UV-cure is carried out to obtain a gelllike consistency.

1 9. A method of forming a gasket as claimed in Claim 1 substantially as described with particular reference to the Examples.

20. A gasketing composition comprising: (a) a monomer represented by one or more of the formulas: (i) (A-X-CO. NH+B wherein X is -0-or -N(R1)-; R' is H or a lower alkyl radical of 1 to 4 carbon atoms; A is CH2=CR2. CO.O--; R2 is H or CH n is an integer from 2 to 6 inclusive; and B is a polyvalent substituted or unsubstituted alkyl, alkenyl, cycloalkyl, aryl, aralkyl, alkyloxy-alkylene, aryloxy arylene or heterocyclic radical; or

wherein PR represents a propylene triol oligomer residue; or

wherein R3 is H, C14 alkyl or hydroxyalkyl or SOCH,; R6 is H, halogen or C14 alkyl; R4 is H, OH or R50; R5 is CH2=C(R5)C(=O); m is an integer, preferably 1 to 8; k is an integer, preferably 1 to 20; and p is 0 or 1; or

wherein R8 is hydrogen, chlorine, methyl or ethyl; R7 is a bivalent organic radical which is lower alkylene of 1-8 carbon atoms, phenylene, or naphthylene; W is a polyisocyanate radical;E is an aromatic, heterocyclic or cycloaliphatic polyol or polyamine radical; d is either 1 or 0; i is 0 when d is 0; and otherwise is equal to one less than the number of reactive hydrogen atoms of E; Z is a (i) polymeric or copolymeric grafted alkylene ether polyol radical or (ii) polymeric or copolymeric methylene ether polyol radical; z is an integer equal to the valency of Z; wherein an asterisk indicates a urethane (-NH-CO-O-) or ureide (-NH- CO-NH-) linkage; (b) a UV initiator; (c) a peroxy initiator; in concentrations from about 0.1% to about 10% by weight, (d) a free radical polymerization accelerator, and (e) an inhibitor, said composition being capable of at least partial cure on exposure to UV radiation and also being anaerobically curable.

21. A composition as claimed in Claim 20 wherein the ultraviolet initiator is (a) a Ca to C6 alkyl dione; (b) a metal carbonyl of the formula MX(CO)V wherein M is a metal atom, x is 1 or 2, and y is an integer determined by the total valence of the metal atoms; or (c) a carbonyl compound of the general formula RB(CO)Rlo wherein R9 is an alkyl, aryl, aralkyl or alkaryl group containing up to about 10 carbon atoms, and R9 is R'O or hydrogen; or R9 and R'O taken together with the carbonyl group form an aromatic or heterocyclic ketone containing up to about 1 6 carbon atoms.

22. A composition as claimed in Claim 20 wherein the UV polymerization initiator is present in concentrations from about 0.1% to about 10% by weight and is acetophenone, benzophenone or 1--or 2-acetonaphthone.

23. A composition as claimed in any of claims 20 to 22 wherein the free radical polymerization accelerator is a heterocyclic secondary amine wherein the heterocyclic ring is hydrogenated, an N,Ndialkyl aryl amine or an N,N-dialkyl substituted aryl amine wherein the substituents are one or more lower alkyl radicals of 1 to 4 carbon atoms, the number of said substituents being at least two when one of said substituents is in the ortho position.

24. A composition as claimed in any of Claims 20 to 22 wherein the free radical polymerization accelerator is an organic sulphimide.

25. A composition as claimed in Claim 24 wherein the sulphimide is benzoic sulphimide.

26. A composition as claimed in any of Claims 20 to 25 wherein the inhibitor is a benzoquinone, naphthoquinone, phenanthraquinone, anthraquinone or a substituted derivative of any of the foregoing.

27. A composition as claimed in any of Claims 20 to 25 wherein the inhibitor consists of benzoquinone.

28. A composition as claimed in any of Claims 20 to 27 wherein the peroxy initiator is an organic hydroperoxide.

29. A composition as claimed in any of Claims 20 to 27 wherein the peroxy initiator is a perester.

30. A gasketing composition as claimed in Claim 20 substantially as described with reference to any of the Examples.