Anaerobically curable compositions

Abstract

An anaerobically curable composition in dry to touch is provided, which is formed from: (a) a liquid anaerobically curable component; (b) a thermoplastic polyurethane (TPU) component in an amount of about 10% to about 35%, for example from about 20% to about 30%, by weight based on the total weight of the composition; and (c) a curing component for curing the liquid anaerobically curable component.

Claims

1. An anaerobically curable composition in dry to touch form, the anaerobically curable composition formed from: (a) a liquid anaerobically curable component; (b) a thermoplastic polyurethane (TPU) component present in an amount of from about 10% to about 35% by weight, based on the total weight of the anaerobically curable composition, wherein the TPU component comprises: (i) polyester segments, based on at least one of a greater than C.sub.10 diol or a greater than C.sub.10 dicarboxylic acid, or (ii) a (co)polyester of dodecanedioic acid and 1,6-hexanediol, said (co)polyester having a melting point of about 70 C., and with an OH number from about 27 to about 34 mg KOH/g (as measured according to standard procedure DIN 53240-2); and (c) a curing component for curing the liquid anaerobically curable component, wherein the curing component comprises a peroxide in liquid form free of encapsulation; and (d) a solvent present in an amount less than 1% by weight, based on the total weight of composition, wherein the TPU component has a mass average molar mass M.sub.w from about 50,000 to about 100,000, and wherein the TPU is soluble in the composition.

2. A composition according to claim 1, wherein the TPU component is present in an amount of from 20% to 30% by weight, based on the total weight of the composition.

3. A composition according to claim 1, wherein the TPU component comprises a modified TPU which includes one or more (meth)acrylate end groups.

4. A composition according to claim 1 wherein the liquid anaerobically curable component is present in an amount of from about 60% to about 85%, by weight based on the total weight of the composition.

5. A composition according to claim 1 wherein the liquid anaerobically curable component is present in an amount of from 65% to 80%, by weight based on the total weight of the composition.

6. A composition according to claim 1 wherein the liquid anaerobically curable component comprises at least one acrylate or methacrylate ester group.

7. A composition according to claim 1 wherein the curing component is present in an amount of from about 0.1 to about 10%, by weight based on the total weight of the composition.

8. A composition according to claim 1 wherein the curing component is present in an amount of from about 1 to about 5% by weight based on the total weight of the composition.

9. A composition according to claim 1 wherein the curing component is present in an amount of about 5% by weight based on the total weight of the composition.

10. A composition according to claim 1 wherein the TPU component has a mass average molar mass M.sub.w from about 55,000 to about 75,000.

11. A composition according to claim 1 wherein the TPU component comprises polyester segments, based on at least one of a greater than C.sub.10 diol or a greater than C.sub.10 dicarboxylic acid.

12. A composition according to claim 1 wherein the TPU component has a glass transition temperature of from about 60 C. to about 0 C., and a melting point of from about 30 C. to about 100 C. as measured by differential scanning calorimetry in accordance with ISO11357.

13. A composition according to claim 1 wherein the TPU component has a glass transition temperature of from about 55 C. to about 20 C.

14. A composition according to claim 1 wherein the TPU component has a glass transition temperature of from about 50 C. to about 30 C.

15. A method of applying a composition according to claim 1 to a substrate comprising the steps of: (i) providing a composition; (ii) heating the composition to a flowable form; and (iii) applying the composition to the substrate.

16. A method of providing a threadlocking composition to a thread of a threaded article to be thread locked, the method comprising: (i) providing the composition of claim 1; (ii) applying the composition to a thread of the threaded article by heating the composition to a flowable liquid form; and (iii) optionally passively or actively cooling the composition to provide a solid tack-free form.

17. A method of threadlocking two threaded articles, the method comprising: (a) providing the composition of claim 1; (b) applying the composition to a thread of at least one of the two threaded articles; and (c) threading the two threaded articles together to initiate anaerobic cure of the composition, thereby chemically bonding the two threaded articles.

18. A bolt or a nut, to which the composition of claim 1 has been applied.

19. An assembly comprising two substrates bonded together by a cured form of a composition according to claim 1.

20. The composition of claim 1, wherein the TPU has a solubility value at 65 C. of at least 40% by weight, based on the total weight of the anaerobically curable composition.

21. An anaerobically curable composition in dry to touch form, the anaerobically curable composition formed from: (a) a liquid anaerobically curable component; (b) a thermoplastic polyurethane (TPU) component present in an amount of from about 20% to about 30% by weight, based on the total weight of the anaerobically curable composition, wherein the TPU component comprises: (i) polyester segments, based on at least one of a greater than C.sub.10 diol or a greater than C.sub.10 dicarboxylic acid, or (ii) a (co)polyester of dodecanedioic acid and 1,6-hexanediol, said (co)polyester having a melting point of about 70 C., and with an OH number from about 27 to about 34 mg KOH/g (as measured according to standard procedure DIN 53240-2); and (c) a curing component for curing the liquid anaerobically curable component, wherein the curing component comprises a peroxide in liquid form free of encapsulation; and (d) a solvent present in an amount less than 1% by weight, based on the total weight of composition, wherein the TPU component has a mass average molar mass M.sub.w from about 55,000 to about 75,000, and wherein the TPU is soluble in the composition.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 shows Torque strength in N.Math.m for a composition of the invention (solid anaerobic formulation) versus a control (Henkel Loctite product 2701). (For each composition the break value is represented by the left hand column and the prevail value is represented by the right hand column.)

(3) FIG. 2 shows the effect of aging on Torque strength in N.Math.m for a composition of the invention (solid anaerobic formulation) under different compositions. (For each composition the break value is represented by the left hand column and the prevail value is represented by the right hand column.)

DETAILED DESCRIPTION

(4) A formulation was prepared based on Loctite product 2701 (available from Henkel Corporation) which is a green, low viscosity, methacrylate-based threadlocking adhesive with high strength, especially for chromated surfaces. It exhibits steel fixture time of 10 min, brass 4 min and stainless steel 25 min. It tolerates slight contaminations of industrial oils. Suitable for all metal fasteners.

(5) All components were mixed with the exception of DIPP 539 (TPU) and CHP.

(6) This mixture was brought to a temperature of 65 C. whilst mixing gently. DIPP 539 was added under high shear using a dissolver stirrer in aliquot portions until all of the material was added. This facilitated proper dissolution of the polyurethane and ensured no clumping of the material. Full dissolution occurred within 30 mins at which time the mixture temperature is reduced to 45 C. At this time the CHP is added under low shear, this reduced both the time and temperature minimising exposure of the peroxide (CHP) thereby reducing any possible decomposition. After the peroxide (CHP) was added the mixture was allowed to cool overnight after which time it becomes solid. The composition prepared is set out in Table 1 below.

(7) TABLE-US-00001 TABLE 1 % by weight based on the total Amount weight of the Material (grams) composition Hydroxypropyl Methacrylate 42.95 33.79 (monomer) SS 119 32.3 25.41 Low Mw polyurethane (methacrylate capped PU) Flex II 10.02 7.89 (Polyurethane resin/Isobornyl methacrylate mixture) PM 16 0.2 0.16 (Free radical stabilizer) PM 17 1.0 0.79 (Metal chelator) Saccharin (accelerant) 0.5 0.39 DIPP 539 38.13 30 (Thermoplastic polyurethane) CHP 2.0 1.57 (initiator/peroxide)

(8) Comparative testing was done using Loctite product 2701 as a control following the standard DIN 267 Part 27. Cold indicates room temperature. Hot indicates 150 C.

(9) The results are set out in the following Table 2:

(10) TABLE-US-00002 TABLE 2 Loctite 2701 Composition of Composition of Control Table 1 Cold Table 1 Hot (Break/Prevail) (Break/Prevail) (Break/Prevail) mPa mPa mPa 38/20 33/5 1/0 45/21 33/2 17/6 32/25 34/5 5/2 60/45 19/2 15/4 44/32 32/6 5/1 AVERAGE 44/29 30/4 9/3

(11) It can be seen that the performance of a composition of the invention although not as high as the 2701 control is still quite acceptable for a medium to high strength threadlocker. These lower results are to be expected given the overall lower levels of active ingredients (70% versus 100% as is the case with 2701 control). This system can be further modified to include functionality within the TPU materials themselves with the incorporation of methacrylate or acrylate end chains, thereby reacting the TPU into the matrix. Further modification whilst using HQEE chain extenders would lead to better thermal stability of these materials which would give superior heat aging performance.

(12) The results shown in FIG. 2 show on-part aging of the composition of Table 1 for one month at room temperature. Each bolt was coated with the solid formulation (containing liquid CHP) and allowed to age at room temperature for 1 month. Cold formulation was used to coat parts which were assembled and aged under the conditions set out in Table 3 below:

(13) TABLE-US-00003 TABLE 3 45 C/95% Humidity (Break Prevail) mPa 120 C. 150 C. 200 C. 7/2 9/1 2/2 11/2 20/4 16/2 7/3 7/1 5/2 13/2 5/1 7/1 26/7 16/3 6/2 14/2 12/3 15/3 7/1 7/1 AVERAGE 14/4 14/2 5/2 9/1

(14) The words comprises/comprising and the words having/including when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

(15) It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.