Anaerobic curing formulations for sealing and blocking bolts and nuts

Abstract

Anaerobic curing formulations for sealing and/or blocking screws, nuts, bolts and screw or sealing caps are described. The sealing formulation comprises at least one acrylic resin and phenoxy-polyethoxy sulphate. The self-locking formulation comprises at least one diacrylate, an acrylic resin, a microencapsulated polymerisation initiator and a microencapsulated polymerisation accelerator. A method is described for coating a polymerization accelerator to obtain a microencapsulated polymerisation accelerator.

Claims

1. An anaerobic curing formulation comprising an aqueous emulsion of: a) at least one acrylic resin and b) phenoxy-polyethoxy sulphate.

2. The formulation according to claim 1, wherein the acrylic resin is an aqueous emulsion of cured copolymers.

3. Formulation according to claim 1 wherein the phenoxy-polyethoxy sulphate is an aqueous mixture containing nonylphenoxy polyethoxy branched ammonium sulphate and an aqueous solution of ammonia.

4. An anaerobic curing formulation comprising an aqueous emulsion of a) 30-60% by weight of at least one dimethacrylate; b) 5-9% by weight of at least one acrylic resin; c) 2-4% by weight of a microencapsulated polymerization initiator; and d) 0.3-1.5% by weight of a microencapsulated polymerization accelerator.

5. Formulation according to claim 4, wherein it comprises a diurethane dimethacrylate.

6. Formulation according to claim 4 wherein the acrylic resin is an aqueous emulsion of cured copolymers.

7. Formulation according to claim 4, wherein the dimethacrylate is bisphenol A ethoxylate dimethacrylate.

8. Formulation according to claim 4, wherein the polymerization accelerator is microencapsulated ferrocene.

9. Formulation according to claim 1 wherein the pH is adjusted in a range between 5 and 10 with an inorganic base selected from the group consisting of NH.sub.4OH and NaOH.

10. Method for microencapsulating a polymerization accelerator, comprising preparing an aqueous gelatin solution, adjusting the pH of the aqueous solution to a value between 4 and 7, introducing a polymerization accelerator into the aqueous gelatin solution, adding an agent to harden the gelatin and an anticaking material, separating the solid part from the aqueous part, washing the solid part with water and drying the end product.

11. Method according to claim 10, wherein the polymerization accelerator is ferrocene, the hardening agent is glutaric aldehyde and the anticaking material is silica.

12. A method for sealing or blocking screws, nuts, bolts, screw caps or sealing caps comprising applying the formulation of claim 1 to the threads of the screws, nuts, bolts, screw caps or sealing caps.

13. A method for sealing or blocking screws, nuts, bolts, screw caps or sealing caps comprising applying the formulation of claim 4 to the threads of the screws, nuts, bolts, screw caps or sealing caps.

14. A method of claim 13 wherein the surfaces of the threads of screws, bolts and screw caps and sealing caps are not pre-treated with a primer.

15. An anaerobic formulation comprising an aqueous emulsion of a) at least one dimethacrylate; b) at least one acrylic resin; c) a microencapsulated polymerization initiator; and d) a microencapsulated polymerization accelerator, wherein the microencapsulated polymerization accelerator is prepared by the method of claim 10.

16. An anaerobic curing formulation comprising an aqueous emulsion containing a) at least one dimethacrylate; b) at least one acrylic resin; c) a microencapsulated polymerization initiator; and d) a microencapsulated polymerization accelerator, wherein the microencapsulated polymerization accelerator includes a coating comprising gelatin, glutaric aldehyde, and silica.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further characteristics and advantages of the present invention will become clear from the following description, provided as a non-limiting example, with reference to the accompanying figures, in which:

(2) FIG. 1 is an IR spectrum of the product Multicor (vehicle engine lubricant oil);

(3) FIG. 2 shows two overlapped IR spectra of the screws immersed in the oil and not immersed in the oil, treated with the sealing formulation according to the present invention;

(4) FIG. 3 is an IR spectrum of the product Torma Prot (vehicle engine lubricant oil);

(5) FIG. 4 shows two overlapped IR spectra of the screws immersed in the oil and not immersed in the oil, treated with the sealing formulation according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) The sealing formulation was then tested for resistance to oil by submerging the treated screws in two different types of vehicle engine lubricant oil: Multicor and TormaProt.

(7) The preparation method of the sealing formulation and the results of the oil resistance and detachment force test are given below in the examples, which are described here solely by way of non-limiting example of the present invention.

EXAMPLE 1

(8) The following compounds are added in a turbo-mixer under stirring: 30 g of deionised water, 4 g of butyl glycol, 0.1 g of pigment Unisperse® blue ID 30466565 and 0.2 g of aqueous solution of ammonia 28% to obtain a mixture with pH 6.5. The compounds are mixed at a speed of 1400 rpm and then 2 g of titanium dioxide, 0.7 g of ammonium benzoate and 4 g of acrylic resin ACRYSOL™ ASE 60 are added to the mixture under stilling. The mixture obtained is placed in a vacuum at 0.6 bars and stirring is maintained for 5 minutes. The mixture is then brought to atmospheric pressure and 16 g of Teflon® are added under stirring while 60 g of phenoxy-polyethoxy sulphate are added. The mixture obtained is maintained under stirring for 25 minutes at 0.8 bars.

(9) In order to obtain an end product with optimal characteristics, such as viscosity and sealing property, the reaction times and pressures must be maintained as in the example.

(10) The product obtained in this example undergoes an oil resistance test after immersion of the screws having surfaces treated with the product of the Example 1. The IR spectrum of the Multicor product (vehicle engine lubricant oil) is recorded and the IR spectrum shown in FIG. 1 is obtained. The outer surfaces of the screws are treated with the product obtained according to Example 1 and the screws are immersed in the Multicor product. The IR spectra recorded are shown in comparison in FIG. 2, which highlights the overlapping of the two IR spectra of the surfaces of the immersed 1 and not immersed 2 screws in the oil. To conclude, it was found that the two IR spectra in FIG. 2 do not show relevant differences and only some absorption bands of the sample immersed in the oil show a slight increase, which can be attributed to migration to the surface of the benzoate present in the sealing product. No new absorption bands are present, and therefore no chemical modifications occurred in the sealing product following immersion in oil of the treated screw with the product of Example 1.

(11) The same test was repeated with another type of vehicle engine lubricant oil, sold under the name Torma Prot.

(12) The IR spectrum of the Torma Prot oil is shown in FIG. 3, while FIG. 4 shows the IR spectra of the outer surfaces of the screws immersed in the oil 1 and not immersed in the oil 2 treated with the sealing product of Example 1. The IR spectra of the surfaces of the immersed and not immersed screws do not show relevant differences. A slight increase is noted in some absorption bands of the sample immersed in the oil, attributable to migration to the surface of the benzoate present in the sealant. No new absorption bands are present, hence no chemical modifications have taken place in the sealing product following immersion in the Torma Prot oil.

EXAMPLE 2

(13) 55 g of deionised water are placed in the turbo-mixer and under stirring the following are added: 0.6 g of pigment UNISPERSE® RED ID 1996500, 0.4 g of an aqueous solution of ammonia 28%, 2 g of titanium dioxide, 0.8 g of talc, 1 g of ammonium benzoate, 0.1 g of ammonium phosphate, 6 g of acrylic resin ACRYSOL™ ASE 60 and 18 g of bisphenol A ethoxylate dimethacrylate. The of the mixture is 6.5. The temperature of the mixture obtained is brought to ambient temperature and the mixture is placed in a vacuum at 0.6 bars and kept under stirring for 5 minutes in a vacuum. The pressure of the mixture is then brought to atmospheric pressure and 21 g of bisphenol A ethoxylate dimethacrylate are added. The obtained mixture is placed in a vacuum at 0.8 bars and kept under stirring for 20 minutes. 3 g of microencapsulated benzoyl peroxide and 0.9 g of microencapsulated ferrocene are added to the product thus obtained and the mixture is stirred for 5 minutes.

(14) The benzoyl peroxide initiator is microencapsulated according to the method known in the prior art, while the ferrocene accelerator is encapsulated via the following method.

(15) 80 g of deionised water are added in the mixer, and 0.2 g of sodium hexametaphosphate and 4 g of gelatin are introduced under stirring. When introduction of the gelatin is complete, the stirring is maintained for a few minutes and the mixture is left to rest for 30 minutes. Under stirring, the temperature of the mixture is brought to 45-70° C. and the sodium hydroxide is added, the mixture is cooled to 43° C., 0.2 g of acetic acid are added and, at the end, 15 g of ferrocene. The temperature of the mixture is cooled at ambient temperature. The temperature of the product obtained is then rapidly cooled to 10-18° C. and 2 g of glutaric aldehyde and 1 g of silica (SiO.sub.2) are added.

(16) The product obtained is settled, then the aqueous solution is removed and the solid part is washed with deionised water. This operation is repeated three times. The product obtained is then filtered and placed in a dryer at 40° C. for 48 hours. The end product is microencapsulated ferrocene.

(17) Surprisingly, the product thus formulated has much higher detachment values than the products in use and the values are very uniform. The detachment values measured on an M10 screw according to the DIN 267/27 standard are given in the following Table 1.

(18) TABLE-US-00003 TABLE 1 Mean Test No 1 2 3 4 5 6 7 8 9 10 value Detachment 30.10 27.47 31.96 31.79 31.70 30.27 26.59 29.95 29.00 28.68 29.71 after 48 hours (Nm)

EXAMPLE 3

(19) 55 g of deionised water are placed in the turbo-mixer and then under stirring the following are added: 0.6 g of pigment UNISPERSE® GREEN ID 30267548, 0.4 g of an aqueous solution of ammonia 28%, 1 g of titanium dioxide, 1 g of ammonium benzoate, 0.1 g of ammonium phosphate and 7 g of ACRYSOL™ ASE 60 (used as acrylic resin). The temperature of the mixture obtained is brought to ambient temperature and the mixture is placed under a vacuum at 0.6 bars. Stirring of the mixture is maintained under a vacuum for 5 minutes. The mixture is brought to atmospheric pressure and 25 g of bisphenol A ethoxylate dimethacrylate are added. It is placed under a vacuum at 0.8 bars and kept under stirring for 20 minutes.

(20) 2 g of microencapsulated benzoyl peroxide and 0.4 g of microencapsulated ferrocene are added to the product thus obtained. The mixture is stirred for 5 minutes.

(21) Surprisingly, the product thus formulated presents very uniform detachment values. The values measured on an M10 screw according to the DIN 267/27 standard are given in the following Table 2.

(22) TABLE-US-00004 TABLE 2 Mean Test No 1 2 3 4 5 6 7 8 9 10 value Detachment 16.80 16.15 17.00 16.31 15.60 16.30 16.21 15.50 15.31 16.75 16.19 after 48 hours (Nm)