WO2003044114A2

WO2003044114A2 - Anaerobic adhesive compositions curable on inactive surfaces

Info

Publication number: WO2003044114A2
Application number: PCT/US2002/036875
Authority: WO
Inventors: Dzu Dinh Luong; Iii Frederick F. Newberth; Canh M. Tran
Original assignee: Henkel Corp; Henkel Loctite Corp
Current assignee: Henkel Corp; Henkel Loctite Corp
Priority date: 2001-11-19
Filing date: 2002-11-18
Publication date: 2003-05-30
Anticipated expiration: 2004-05-19
Also published as: AU2002359417A1; WO2003044114A3

Abstract

The present invention relates to anaerobically curable compositions, methods of preparation, and methods of use that provide enhanced physical properties when cured in contact with untreated inactive surfaces. The compositions which include an alkanediol dimethacrylate, a (meth)acrylate selected from the group consisting of glycerol (meth)acrylates, glycol (meth)acrylates, and combinations thereof, and a free-radical initiator, may be used without the addition of a transition metal catalyst.

Description

LC-4507PCT PATENT

ANAEROBIC ADHESIVE COMPOSITIONS CURABLE ON INACTIVE SURFACES

BACKGROUND OF INVENTION FIELD OF THE INVENTION

[0001] The present invention relates to anaerobically curable compositions which when cured on an inactive surface provide enhanced strength of cure, speed of cure, or combinations thereof. The compositions cure on inactive surfaces without the use of a primer and without the addition of a transitional metal catalyst.

BRIEF DESCRIPTION OF THE RELATED TECHNOLOGY

[0002] Anaerobic adhesive compositions are well known for their ability to remain in a liquid, unpolymerized state in the presence of oxygen and to cure to a solid state upon the exclusion of oxygen. Early work on anaerobic adhesive compositions concentrated on developing a cure system which improved the speed and/or bond strength of the adhesive composition. Various cure systems for anaerobic adhesive compositions have been developed to primarily focus on efficiently performing the redox reaction, which is the basis for anaerobic chemistry. Hydroperoxides were found to serve as a catalyst for the generation of a free radical.

[0003] Anaerobic compositions generally contain (meth)acrylic functional monomers, an organic hydroperoxy or perester initiator, accelerators such as saccharin and/or dimethyl-p- toluidene, and stabilizers such as hydroquinone or other phenolic stabilizers and metal chelators such as sodium EDTA. Those persons of ordinary skill in the art acknowledge that peroxides serve as a free radical generating source which initiate free radical curing of the polymerizable anaerobic adhesive monomer compositions. To increase the speed at which the free radical is generated, accelerators are employed in combination with the peroxides to enhance the speed at which the peroxide free radical is generated. In so doing, the cure speed of the anaerobic adhesive composition is increased. Speed of cure and strength are two desirable properties of anaerobic sealants that increase their usefulness for impregnation of porous materials and threadlocking.

[0004] Substrates such as stainless steel, zinc, dichromate, cadmium and plastic are inactive porous materials that are relatively slow to cure compared to active metals such as iron and copper. Therefore, many anaerobic adhesive compositions have conventionally employed primer compositions to speed their cure and/or the addition of a transition metal, generally in the form of a salt. For inactive surfaces, primer compositions have been considered necessary for the quick fixture and cure times required of many applications.

[0005] The use of primer compositions requires an additional step prior to applying the anaerobic adhesive composition, which is often inconvenient and costly. Often the solvent used to carry the accelerator component in the primer is environmentally harmful and requires special handling and disposal. Moreover, the user must ordinarily wait until the solvent has evaporated before applying the adhesive. For example, U.S. Patent No. 4,731,146 to Clark discloses a primer/activator composition that requires the use of a volatile organic solvent to carry the cure activator which must evaporate before the anaerobically curable composition may be introduced to the substrate.

[0006] Limiting the number of components required to provide an anaerobically curable composition promotes efficiency of manufacturing and reduction of cost. A further advantage would be to provide an anaerobically curable composition with enhanced properties such as speed of cure and strength of cure without the need for a primer or the addition of a transitional metal. Therefore, there is a need for an anaerobically curable composition that provides enhanced cure properties with a limited number of components required in manufacture that does not require the additional step of preparing the substrate with a primer and may be used without the addition of a transitional metal. SUMMARY OF THE INVENTION

[0007] One aspect of the present invention provides an anaerobically curable composition which when cured in contact with an untreated inactive surface such as stainless steel, zinc, plastic, and cadmium and without the addition of transition metal catalysts provides enhanced strength of cure, speed of cure, and combinations thereof. The composition includes an alkanediol dimethacrylate and a glycerol (meth)acrylate, glycol (meth)acrylate, or combinations thereof, such as 1,3 -glycerol dimethacrylate, and methyl triglycol methacrylate as well as an anaerobic cure system. The alkanediol dimethacrylate may be a C₂-C₆ alkanediol dimethacrylate, such as 1,4-butanediol dimethacrylate.

[0008] Another aspect of the present invention provides an anaerobically curable composition which when cured in contact with an untreated inactive surface and without the addition of transition metal catalysts provides enhanced strength of cure, speed of cure, and combinations thereof, which includes the reaction product of an alkanediol dimethacrylate and a (meth)acrylate selected from the group consisting of glycerol (meth)acrylates, glycol (meth)acrylates and combinations thereof, and an anaerobic cure system

[0009] A further aspect of the present invention provides a method of preparing an anaerobically curable composition which when cured in contact with an untreated inactive surface and in the absence of added transition metal catalysts provides enhanced strength of cure, speed of cure, and combinations thereof, comprising the steps of combining an alkanediol dimethacrylate and a (meth)acrylate selected from the group consisting of glycerol (meth)acrylates, glycol (meth)acrylates and combinations thereof, and an anaerobic cure system.

[0010] A still further aspect of the present invention provides a method of impregnating a porous untreated inactive surface with an anaerobic sealant. The method includes preparing a composition comprising an alkanediol dimethacrylate, a (meth)acrylate selected from the group consisting of glycerol (meth)acrylates, glycol (meth)acrylates and combinations thereof and an anaerobic cure system. The porous inactive surface is then impregnated with the composition and allowed to cure. DETAILED DESCRIPTION OF THE INVENTION

[0011] The anaerobically curable compositions of the present invention provided improved cure properties when cured on an untreated inactive surface. The compositions may be used without the addition of a transition metal catalyst and without the additional step of first priming or treating the surface which has the disadvantages of added cost and time.

[0012] 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.

[0013] The curable combination of components of the compositions include an alkanediol dimethacrylate combined with glycerol (meth)acrylates, glycol (meth)acrylates, or combinations thereof, and an anaerobic cure system. The anaerobic compositions may be used with a variety of untreated inactive surfaces that include but are not limited to stainless steel, zinc, plastic, and cadmium.

[0014] The alkanediol dimethacrylate may be used in the largest weight percentage compared to the other components. The composition may include between about 30% to about 90% of the alkanediol dimethacrylate by weight of the composition. Useful alkanediol acrylates include C₂-C₆ alkanediol dimethacrylates such as 1,4-butanediol dimethacrylate.

[0015] The glycerol (meth)acrylates, glycol (meth)acrylates,^v or combinations thereof may be used in a smaller percentage; from about 10% to about 30% by weight. Examples of these include but are not limited to 1,3 -glycerol dimethacrylate, methyl triglycol methacrylate, poly(ethylene glycol) di(2-ethyl hexoate), triethylene glycol dimethacrylate, poly(ethylene glycol) dimethacrylate, di(pentamethylene glycol) dimethacrylate; tetraethylene glycol di(chloroacrylate); diglycerol diacrylate; diglycerol tetramethacrylate; butylene glycol dimethacrylate; neopentyl glycol diacrylate; and trimethylopropane triacrylate. [0016] Additional (meth)acrylates may also be added.

[0017] Other (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.

[0018] 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.

[0019] Hydroxyalkyl (meth)acrylates are also 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.

[0020] A portion of the (meth)acrylic monomer may comprise 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:

[0021] 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 o

-CH; -0 -C - =CH_;

[0022] 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 -O C ^■C=CH₂

>3

[0023] m may be 0 to 12, preferably from 0 to about 6; n is at least 1 (e.g_i5 1 to about 20 v or more, preferably between about 2 to about 6); and p is 0 or 1.

[0024] Examples of these polymerizable multi(meth)acrylate esters include, but are not limited to, di-, tri- and tetraethyleneglycol dimethacrylate, dipropyleneglycol; dimethacrylate; polyethyleneglycol dimethylacrylate; di(pentamethyleneglycol) dimethacrylate; tetraethyleneglycol diacrylate; tetra-ethyleneglycol di(chloracrylate); diglycerol diacrylate; diglycerol tetramethacrylate; tetramethylene dimethacrylate; ethylene dimethacrylate; and neopentylglycol diacrylate. Others include, triethyleneglycol dimethacrylate, butyleneglycol dimethacrylate, bis(methacryloxyethyl) phosphate, 1,4 butane diol di(meth)acrylate and trimethylol propane dimethacrylate.

[0025] The (meth)acrylate monomers employed in these compositions may be curable through a free-radical mechanism using an anaerobic cure inducing composition, desirably in the presence of a free-radical initiator, such as a peroxide. A number of well known initiators of free radical polymerization may be incorporated in the present invention. Among those included are, without limitation, hydroperoxides, such as cumene hydroperoxide (CHP), paramenthane hydroperoxide, tertiary butyl hydroperoxide (TBH) and tertiary butyl perbenzoate. Useful amounts of peroxide compounds typically range from about 0.1 to about 10% by weight of the total composition. A reducing agent, such as saccharin may also be included.

[0026] While the compositions are anaerobically curable, meaning in the substantial absence of oxygen, they are also optionally heat curable. For this reason a heat curing catalyst may also be employed.

[0027] Stabilizers and inhibitors may also be employed as well as chelating agents to control and prevent premature peroxide decomposition and polymerization. Among those useful inhibitors include phenols such as hydroquinone and quinones. Chelating agents may be used to remove trace amounts of metal contaminants. An example of a useful chelating agent is the tetrasodium salt of ethylenediamine tetraacetic acid (EDTA).

[0028] Other agents such as thickeners, plasticizers, fillers, elastomers, thermoplastics, and other well-known additives may be incorporated where functionally desirable.

[0029] The method of preparing the anaerobically curable compositions include combining the alkanediol methacrylate with the glycerol (meth)acrylates, glycol (meth)acrylates, or combinations thereof, as described above. Other components may also be included such as free-radical initiators, heat cure catalysts, thickeners, plasticizers, fillers, elastomers, thermoplastics, and the like. [0030] The anaerobically curable compositions may be used to impregnate porous inactive surfaces by any conventional impregnation means such as wet vacuum impregnation, wet vacuum/pressure impregnation, or dry vacuum/pressure impregnation.. The impregnate is then allowed to cure in the surface either at room temperature or heated.

[0031] The anaerobically curable compositions are also useful as threadlockers, i.e. to secure a nut to a bolt. This is achieved by applying the composition to the threads of a bolt, mating it with a nut and allowing it to cure.

[0032] 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.

EXAMPLE

[0033] Anaerobically curable threadlocking compositions according to the present invention were prepared. Comparative compositions A and B and inventive composition C were prepared using approximately the amounts shown in Table I.

TABLE I

* composition contains at least one peroxide and saccharin

[0034] The compositions were applied in equal amounts to the threads of bolts and mated with nuts using a pretorque of 5 newton-meters (Nm) (about 44 in-lbs.). The compositions we allowed to cure for 24 hours at room temperature. The percent of ultimate strength was also calculated. [0035] The compositions were tested for their cure speed as measured by the threadlocking strength (breakloose/prevail [in-lbs.]) developed on various inactive substrates (nuts and bolts) , as well as on degreased steel and reoiled steel as a comparison, at room temperature for a given cure time. A relatively high breakloose torque is preferred as this is the force required to initially move the nut. A relatively lower prevail strength is desired to provide ease of disassembly.

[0036] The results of these tests are shown below in Table II.

TABLE II

[0037] As indicated by the results in Table II, Inventive Composition C shows significant improvement with speed of cure and strength of cure. Inventive Composition C worked especially well with zinc demonstrating an advantageously higher breakloose strength as compared to the prevail strength, and a higher % ultimate strength than both Comparative Compositions A and B.

Claims

WHAT IS CLAIMED IS:

1. An anaerobically curable composition which when cured in contact with an inactive surface and in the absence of added transition metal catalysts provides enhanced strength of cure, speed of cure, or combinations thereof, comprising an alkanediol dimethacrylate, a (meth)acrylate selected from the group consisting of glycerol (meth)acrylates, glycol (meth)acrylates, and combinations thereof, and an anaerobic cure system.

2. The composition of claim 1 wherein said alkanediol dimethacrylate is selected from the group consisting of C₂-C₆ alkanediol dimethacrylates.

3. The composition of claim 1 wherein said alkanediol dimethacrylate comprises 1,4- butanediol dimethacrylate.

4. The composition of claim 1 wherein said (meth)acrylate is selected from the group consisting of 1,3 -glycerol dimethacrylate, methyl triglycol methacrylate, and combinations thereof.

5. The composition of claim 1 wherein said alkanediol dimethacrylate comprises from about 40% to about 90% by weight of said composition.

6. The composition of claim 1 wherein said (meth)acrylate comprises from about 10% to about 30% by weight of said composition.

7. The composition of claim 1 wherein said inactive surface is selected from the group consisting of stainless steel, zinc, plastic, and cadmium.

8. An anaerobically curable composition which when cured in contact with an inactive surface and in the absence of added transition metal catalysts provides enhanced strength of cure, speed of cure, or combinations thereof, comprising a C₂-C₆ alkanediol dimethacrylate, a (meth)acrylate selected from the group consisting of glycerol (meth)acrylates, glycol (meth)acrylates and combinations thereof, and an anaerobic cure system.

9. An anaerobically curable composition which when cured in contact with an inactive surface selected from the group consisting of stainless steel, zinc, plastic, and cadmium and in the absence of added transition metal catalysts provides enhanced strength of cure, speed of cure, or combinations thereof, comprising 1,4-butanediol dimethacrylate, 1,3 -glycerol dimethacrylate, methyl triglycol methacrylate, and an anaerobic cure system.

10. An anaerobically curable composition which when cured in contact with an inactive surface and in the absence of added transition metal catalysts provides enhanced strength of cure, speed of cure, or combinations thereof, comprising a reaction product of an alkanediol dimethacrylate, a (meth)acrylate selected from the group consisting of glycerol (meth)acrylates and glycol (meth)acrylates, and an anaerobic cure system.

11. The composition of claim 10 wherein said alkanediol dimethacrylate is selected from the group consisting of C₂-C₆ alkanediol dimethacrylates.

12. The composition of claim 10 wherein said alkanediol dimethacrylate comprises 1,4- butanediol dimethacrylate.

13. The composition of claim 10 wherein said (meth)acrylate is selected from the group consisting of 1,3 -glycerol dimethacrylate, methyl triglycol methacrylate, and combinations thereof.

14. A method of preparing an anaerobically curable composition which when cured in contact with an inactive surface and in the absence of added transition metal catalysts provides enhanced strength of cure, speed of cure, or combinations thereof, comprising the steps of combining an alkanediol dimethacrylate and at least one (meth)acrylate selected from the group consisting of glycerol (meth)acrylates, glycol (meth)acrylates and combinations thereof.

15. The method of claim 14 wherein said (meth)acrylate is selected from the group consisting of 1,3 -glycerol dimethacrylate, methyl triglycol methacrylate, and combinations thereof.

16. A method of impregnating a porous inactive surface with an anaerobic sealant comprising the following steps: a) preparing a composition comprising an alkanediol dimethacrylate and a (meth)acrylate selected from the group consisting of glycerol (meth)acrylates and glycol (meth)acrylates and combinations thereof; b) impregnating said porous inactive surface with said composition; and c) allowing said composition to cure within said porous inactive surface.

17. The method of claim 16 wherein said alkanediol dimethacrylate is selected from the group consisting of C₂-C₆ alkanediol dimethacrylates.

18. The method of claim 16 wherein said alkanediol dimethacrylate is 1 ,4-butanediol dimethacrylate.

19. The method of claim 16 wherein said (meth)acrylate is selected from the group consisting of 1,3 -glycerol dimethacrylate, methyl triglycol methacrylate, and combinations thereof.

20. The method of claim 16 wherein said inactive surface is selected from the group consisting of stainless steel, zinc, plastic, and cadmium.

21. An anaerobically curable threadlocking composition which when cured in contact with an inactive surface and in the absence of added transition metal catalysts provides enhanced strength of cure, speed of cure, or combinations thereof, comprising an alkanediol dimethacrylate, a (meth)acrylate selected from the group consisting of glycerol (meth)acrylates, glycol (meth)acrylates, and combinations thereof, and an anaerobic cure system.