|Title of Invention||
"A FORMULATION USEFUL AS ANAEROBIC ADHESIVES"
|Abstract||A formulation useful as anaerobic adhesive A formulation useful as anaerobic adhesive by the following ingredients monomers (100 parts), initiators (2-7 phm), imides (0.2-1.0 phm), accelerators (0.04-0.8 phm), stabilisers (0.04-0.6 phm). The composition has long shelf life in the liquid state as long as contact with air is maintained. In the present investigation the care has been taken to describe the sequence of addition of each raw material and also explain the function of each component in the formulation to increase or decrease the set times.|
|Full Text||This invention relates to a formulation useful as anaerobic adhesive.This invention particularly relates to a Anaerobic Sealant formulation having extended Storage Stability. More particularly this invention relates to polymerisable formulation, the polymerisation of which is inhibited by the presence of air or oxygen and which polymerise spontaneously upon the substantial exclusion of air and free oxygen. Such compositions are generally known as and are hereinafter referred to as Anaerobically Curable Compositions and are said to the capable of curing anaerobically". These anaerobic compositions are useful as nutlock, studlocl the etaining. compounds, hydraulic sealants and piping sealants. A principal novel feature of the compositions of the present invention is that in addition to having anaerobic curing characteristics, the compositions have a long shelf life in the liquid state as long as in contact with air is maintained. This property is particularly useful in bonding the surfaces since the composition can be stored or permitted to stand in contact with air for long periods of time without polymerisation and yet when it is placed in the threaded assemblies where there is an exclusion of air, should be in a position to polymerise and form a sirong bond.
It is known that the monomeric esters having the following general formula,
are mixed with other additives to get a suitable anaerobic adhesive compositions. One of the additives is initiators. Suitable initiators used are hydroperoxides which include cumene hydroperoxide, i-butyl hydroperoxide, methylethylketone hydroperoxide. Suitable accelerators used in order to render the composition cured anaerobically are tertiary amines such as tri ethyl amine, orthobenzoic sulphimide, dimethylparatoluidene etc. It is also essential to add polymerisation inhibitors so as to make the compositions with long shelf life. These are quinones such as naphtnaquinone, benzoquinone ete.
There are several patents in which the anaerobic adhesive formulations have been reported.
1. Burnett, R.E., and Nordlander, B.W., U.S. Patent 2,628,178
2. Krieble V.K., U.S. Patent 2,895,950 (July 21, 1959).
3. Krieble, V.K., U.S. Patent 3,041,322 (june 26, 1962).
4. Krieble, R.H., U.S. Patent 3,043,820 (July 10, 1962).
Most of the patents described the formulations which hold good for the mild steel surfaces and also the process for making these formulations has not been described and for this reason, the formulations made with the help of these patents have given the anaerobic adhesives with long curing times, and short storage stability. In the present investigation the care has been taken to describe the sequence of addition of each raw material and also explained the function of each component in the formulation to increase or decrease the set times and the torque strengths of the mated threaded and non threaded assembles. Apart from this, these compositions have also extended storage stability to even two years or more.
The main object of the present invention is to provide a formulation useful as adhesive which obviates the drawbacks of known adhesives.
Another object of the present invention is to provide a anaerobic curable formulation having extended storage stability.
Accordingly, the present invention provides a formulation useful as anaerobic adhesive which comprises following ingredients a) monomers, b) initiators, c) imides, d) accelerators, e) stabilizers characterized that the monomers are in the range of 100 parts, initiators in the range of 2-7 phm, imides 0.2 to 1.0 phm, accelerators in the range of 0.04 to 0.8 phm, stabilizers in the range of 0.04 to 0.6 phm.
In an embodiment of the present invention the monomer used may be such as diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate polythelene glycol 200 dimethacrylate, tri methylol propane trimethacrylate.
In another embodiment of the invention the initiator used may be such as cumene hydroperoxide tertiary butyl hydroperoxide, methyl ethyl ketone hydroperoxide.
In yet another embodiment of the invention the accelerator used may be such as N - N dimethyl para toluidene, triethyl amine, 1,2,3,4 tetra hydroquinolene, di-methyl anilene. In still another embodiment of the invention the imides used may be such as orthobenzoic acid sulphimide (saccharin) succinimide, N - ethyacetamide.
In yet another embodiment of the invention the stabilizer used may be such as 1,4 benzoquinone, naphthoquinones, anthraquinone.
In accordance with the present invention, it has been found that the foregoing objects can be attained in anaerobic cure sealant composition containing essentially dimethacrylates and a catalyst which will promote the polymerisation of monomer upon exclusion of air. The addition of small amounts of quinones will greatly prolong the shelf life of these compositions. Generally, effective range of 0.005 to 0.04 phrn of quinones are used. However, the actual amount of quinone necessarily will depend upon the instability of the basic sealant composition. It is desirable to prepare a test formulation of small quantity for rapid evaluation before finalising the formulation on production scale. .Of the various quinones,- the benzoquinones and naphthaquinones are proved to be very effective and desirable because they are soluble in alcoholic solution.
The amount of initiator necessary for optimum cure may be decreased by the use of accelerator such as tertiary amines. Generally, these accelerators are used in the range of 0.05 to 0.8 by weight of monomer in the composition. The initiators used are generally hydroperoxides of cumene, tertiary butyl, metyl ethyl ketone and these catalysts are preferably used in the range of 1-10% on the weight of the monomers. The accelerators such as benzoic sulphimide and dimethyl paratoluidene are used.
By way of example, these include organic amines such as tertiary amines including tri-ethyl amine and di-methyl paratoluidene, di-ethyl anilene etc. In general if the accelarator is added more than 10%, then it will have a dilution effect. In such a case for quick bonding, the accelerator may be applied separately, preferably as a pre-treatment to the surfaces to be bonded. Such a pre-treatment step with an accelerator is particularly advantageous for promoting the bonding of the sealant composition on zinc and cadmium surfaces.
The monomers generally used in these formulations are dimethacrylate esters of diethylene glycol, (DEC DMA) triethylene glycol (TEG DMA) tetraethylene glycol (TETEG DMA) and trimethylolpropane trimethacrylate (TMA TMA). These monomers need not be freed from the inhibitors or stabilizers such as hydroquinone or monomethyl ether of hydroquinone which are usually added to stabilise them.
To determine the long term stability of the sealant composition a simple and effective test has been evaluated. The sealant is placed in polythene bottles and these are placed in an oven, controlled at 82°C plus or minus 1°C. At every regular intervals of 10 minutes a glass rod is dropped into the sealant to notice whether the product has gelled. The viscosity of the gelling sealant prevents the rod from striking at the bottom. The time is noted. It has been found that the sealant free from gelling in 30 minutes or more during this accelerated heat aging test, is considered to be suitable and free from gelling at 25°C in presence of oxygen for atleast one year. It is commercially acceptable.
To test the activity of the anaerobic sealant compositions of the present invention, some more simple tests are designed. For one test to determine the initial set locking time, one drop of the sealant mixture is placed between two elongated glass plates or even metal preferably at right angles to each other. When it is possible to move the two plates as a unit by manupulating one of the plates, it is evident that polymerisation has taken place. The time taken to lock the plates is noted.
In another test, the strength of the bond between the threaded assemblies is determined by placing several drops of the anaerobic sealant in the mating threads of nut and bolts, tightening the nut to a pre determined torque and allowing the sealant to set and cure at room temperature (25°C), the break loose torque (BT) is noted but more conventionally the prevailing torque (PT) is the measure of bond strength. To obtain the prevailing torque of the bond, the torque required to turn the bolt or screw, usually four points after the break loose torque and upto one full turn or average is measured. Commercially a bolt adhesive developing PT of one foot pound on 3/8" full nut is considered to be satisfactory.
To illustrate the efficacy of present invention, various formulations were prepared in order to study the role of each component in the formulation. This is essential as the anaerobic sealant compositions are used in various studdlock, nut lock, hydraulic sealant, pipe sealant etc. For each application, the sealant composition changes.
The formulations prepared are not mere admixture of individual ingradients but it is a synergistic mixture in which the aggregate property of the formulation is different from the properties of individual ingradients- and is net a product of chemical reacline
Following examples are therefore, given in the way of illustrations and therefore should not be construed to limit the scope of the present invention:
Anaerobic curing properties were achieved with the compositions by passing a stream of air through the components. A glass flask fitted with a non-metallic stirrer was charged with TETEG DMA lOOg and cumene hydroperoxide 2g . To this orthobenzoic sulphimide (saccharin accelerator (mainly tertiary amine) and stabiliser 1,4 benzoquinone were added one after the other in the quantities mentioned in the following table:
a) N.N. Dimethyl p toluidene
b) 1, 2, 3, 4 Tetrahydro quinolene
c) 1,4 Benzoquinone
BT - Break loose torque
PT - Prevailing torque
All these formulations are stable at 82°C for more than 30 minutes.
It is evident from the above table that as the quantity of Saccharin is increased, the accelerator and also the stabiliser have to be increased proportionately to maintain the stability of the composition.. All these 8 compositions are found to be stable for more than 30 minutes at 82°C plus or minus 1°C. This indicates that these compositions are stable at ambient temperatures for more than a year which is commercially acceptable.
EXAMPLE - 2:
Anaerobic sealant compositions were prepared by taking trimethylolpropane trimethacrylate (TMPTMA) 1 OOg and cumene hydroperoxide 2g. To this mixture, orthobenzoicacid sulphimide, accelerator and stabilisers were added as shown in the following table:
a) N.N. Dimethyl P_ toluidene
b) 1, 2, 3, 4 Tetrahydroquinolene
c) 1,4 Benzoquinone
BT - Break loose torque PT - Prevailing torque
All these formulations are stable at 82°C for more than 30 minutes.
All che compositions were maintained same as shown in the example 1 except for the fact that the anaerobic monomer has been changed. It has been observed here that the set time of anaerobic sealant compositions containing TMPTMA monomer are faster in curing and gave higher torque values.
Anaerobic sealant compositions were made by mixing monomer 100 parts, cumene hydroperoxide, 2 parts, saccharin, 0.2 parts dimethyl p-toluidene 1 part and 1,4 benzoquinone 0.1 part. The effect of various monomers used in these formulations on the stability and also the torque strengths are given in the following table:
EXAMPLE - 4:
To illustrate the efficacy of the imides, anaerobic sealant compositions were made using tetra etylene glycol dimethacrylate 100 parts (TETEG DMA) cumene hydroperoxide 2 parts, dimethyl paratoluidene 0.5 parts and 1,4 benzoquinone 0.05 parts. Different imides such as saccharin, succinimide &-, N.ethyl acetimide 0.2 parts were added as shown in the table. It is noticed that the saccharin is found to be the best imide which can be successfully used in the anaerobic formulations.
a) Saccharin (b) Saccinimide (c) N.ethyl acetimide
+ EXAMPLE - 5
To illustrate the effect of increasing the amounts of quinone stabiliser and its relation with dimethyl para toluidene, few formulations were prepared using tetraethylene glycol dimethacrylate 100 parts, cumene hydroperoxide 2 parts and saccharin 0.7 parts and other two ingredients such
as dimethyl para toluidene (DMPT) and 1,4 benzoquinone were added as shown in the following table:
* 1, 2, 3, 4 Tetra hydroquinolene
100 PPM = 0.01 weight percent on monomer
Upon heat aging at 82°C, these formulations did not gell at 30 minutes. Generally, it was found that with the increase in the dimethyl para toluidene, it is necessary to increase the stabiliser benzoquinone. The prevailing torque increased with the increase of dimethyl para toluidene.
EXAMPLE - 6:
The main advantages of this compositions are:
1. These anaerobic sealant compositions have extended shelf stability for more than a year
at ambient temperatures which is commercially acceptable.
2. These compositions cure in between 15-30 minutes between the threaded assemblies
where there is an exclusion of air.
3. These anaerobic sealant compositions have 5 components i.e., (a) Monomers
(Dimethacrylate) (b) Initiators (Hydroquinones) (c) Imides (d) Accelerators (Amines) (e)
By varying these components, the sealant compositions with desired torque strengths could be prepared to meet the demands of the engineering industry (nutlock, studlock, hydraulic sealants, retaining compounds and gasket eliminators).
We claim :
1. A formulation useful as anaerobic adhesive which comprises following
ingredients a) monomers, b) initiators, c) imides, d) accelerators, e)
stabilizers characterized that the monomers are in the range of 100 parts,
initiators in the range of 2-7 phm, imides 0.2 to 1.0 phm, accelerators in
the range of 0.04 to 0.8 phm, stabilizers in the range of 0.04 to 0.6 phm.
2. A formulation as claimed in claim 1 wherein the monomers used is
selected from diethylene glycol dimethacrylate, triethylene glycol
dimethacrylate, tetra ethylene glycol dimethacrylate, polythelene glycol
200 dimethacrylate, tri methylol propane trimethacrylate.
3. A formulation as claimed in claims 1-2 wherein the initators used is
selected from cumene hydroperoxide, tertiary butyl hydroperoxide, methyl
ethyl ketone hydroperoxide.
4. A formulation as claimed in claims 1-3 wherein imides used is
orthobenzoic acid sulphimide (saccharin) succinimide, N-ethylacetamide.
5. A formulation as claimed in claims 1-4 wherein accelerators used is
selected from N-N dimethyl para toluidene, triethylamine, 1,2,3,4 tetra
hydroquinolene, di-methyl aniline.
6. A formulation as claimed in claims 1-5 wherein stabilizers used is
selected from 1 ,4-benzoquinone, naphthoquinones, anthraquinone.
7. A formuation useful as anaerobic adhesive as herein described with
reference to the examples.
|Indian Patent Application Number||1091/DEL/1999|
|PG Journal Number||12/2008|
|Date of Filing||10-Aug-1999|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI-110001, INDIA.|
|PCT International Classification Number||C09J 11/08|
|PCT International Application Number||N/A|
|PCT International Filing date|