FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules  2005

COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)

TITLE OF THE INVENTION

Improvised Bond Performance with Unconventional curing for Abrasive and Super abrasive resin bonded wheels

APPLICANTS:

Name Nationality Address
Wendt India Ltd Indian 69/70 Sipcot Hosur 635 126 Tamil Nadu India

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-

TECHNICAL FIELD
[001] The embodiments of this invention relate to a resin bonded tool and  more particularly but not exclusively the embodiments of this invention relate to an improvised resin bonded tool which can be processed at an elevated temperature by enhancing the properties such as hardness of the bond  mechanical properties with controlled bond fracture to facilitate more aggressive cutting. Thus the invention is improvised resin hot pressed abrasive tools made from phenol formaldehyde resins and combined abrasives of super abrasives plus conventional abrasives grits and additives to sustain higher cut and longer life. Further a post curing is carried out by microwave technology. This yields a longer life with fast cutting.

BACKGROUND
[002] Resin bonded diamond or cubic Boron nitride grinding wheels are used in tool and cutter  surface and in saw gumming applications on carbides  steels and ceramics or glass. These wheels in various forms and configurations contain a modified phenolic bond system. To produce the abrasive wheel matrix of this   Diamond or CBN abrasive is bonded by a hot-pressing processing route.
[003] However  the abrasive products such as grinding wheels that are manufactured by the conventional method of producing abrasive wheel matrix of resin bonded does not facilitate aggressive cutting  which may affect the overall efficiency of the abrasive product.
[004] Further  it can also be observed that the abrasive products such as grinding wheels that are manufactured by the conventional method of producing abrasive wheel matrix of resin bonded does not have longer life.
[005] Therefore  there is a need for an efficient process in the manufacturing of resin bonded abrasive products which may be used to overcome the above mentioned drawbacks
OBJECT OF INVENTION
[006] The object of the invention is to provide an improvised bond formulation and a method of unconventional curing for manufacturing the abrasive products that may enhance its characteristics.

SUMMARY OF INVENTION
[007] In view of the foregoing  an embodiment herein provides an abrasive body having the said abrasive particles and phenolic resins of novalac bond for binding the abrasive particles  wherein the abrasive particles include one of super abrasives  super abrasives and conventional abrasives and a combination thereof. Further  the phenolic resin of novalac bond includes active filler  wherein the active filler is a combination of two inorganic metallic Fluoride and Sulphide formulations. Further  the phenolic resins novalac bond also includes Hexamethylenetetramine in a substantially higher percentage to facilitate faster curing and enhanced strength.

DETAILED DESCRIPTION OF EMBODIMENTS
[008] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly  the examples should not be construed as limiting the scope of the embodiments herein.
[009] The embodiments herein disclose a method of manufacturing the abrasive products.
[0010] The invention is a novalac type phenol formaldehyde bonded abrasive tool comprising a modified and a short flow resins. The additive to the bond is a Sodium Aluminum Fluoride in common parlance  known as synthetic cryolite and Pyrite fines  chemically called as Iron Sulphide  having 35 to 55% by weight of Sulphide contents. This material is a processed mineral where in synthetic cryolite is chemically processed from fluorspar mineral. Both are mineral based fillers in the specific gravity range of 2.95 and 5.10.
[0011] The filler materials may constitute about 5%-10% by volume on the mix and more preferably 40 -80% by volume to bond. The average particle size is from 30 µ to 15 µ
[0012] The bond further comprises of a single stage phenol formaldehyde powder having 5% to 40% weight percentage modification by epoxy material  which has a Methyl amine cure hardener  preferably in 10 to 15 weight percentage in the resin powder. More precisely the amine cure is Hexamethylenetetramine. The second one in the bond is a short flow straight phenol formaldehyde novalac powder  precisely having the same amine cure hardener  preferably in the weight percentage of 9% to 12%. These powders are having flow propriety of 18mm to 22mm at 60? inclination for the modified resin and 13mm to16mm for the straight short flow resin. More preferably the volume percentage presence of the bond is 5-10 on the mix matrix.
[0013] The bond is used in the form of a blend preferably the bond and fillers are mixed together to get a homogenous mixture by using one of ball mill or ribbon blender or conical blender or combination thereof.
[0014] The blend is used in the formation of abrasive tools. The abrasive tools comprise a mix matrix formed to a specific shape of standard dimensions. The abrasive mix matrix in a composition of abrasive blend  cure initiator or accelerator and a plasticizer based liquid wetting agent.
[0015] The abrasive composition is a mixture of an abrasive and the bond described above. The abrasive preferably diamond or CBN provides from 5 to 80 volume percentage on the total composition. The abrasive composition may contain other abrasives of fused microcrystalline  macrocrystalline or white Aluminium Oxide and SiC and others like sol-gel  krystolax .ceramic coated granulated and zircon Alloyed grains. The abrasive tools preferably contain one or more of these abrasives. The preferred abrasive is diamond or CBN. The abrasive grit size is based on the function or application on the tool. Further  abrasive tools with more than one grit size sometimes being desirable. The preferred abrasive is a super abrasive with a fixed concentration of particle distribution. The abrasive tools contain substitute grit and filler grit from other above said conventional abrasive groups. The most preferred abrasive is silicon carbide or white fused Aluminium Oxide. The preferred substitution may be one grit coarser or one or two grits finer than the size of the preferred primary super abrasive. The preferred filler grit is of the same group of substitute grit. The preferred size to filler grit is 30µ to 20µ.
[0016] The bond indicated above preferably provides from 10 to 80 volume percentage of the total composition and 35 to 50 volume percentage to the preferred abrasive group.
[0017] The abrasive composition is mixed by conventional mixing technique known to those skilled in art. Preferably the adherence of the bond blend to the grain grits is done by wetting the grits with a solvent type plasticizer. Most preferably a solution compatible to phenolics and a supplemental hardener to phenolic bond.
[0018] The shape of the abrasive tools used is determined by the function to be performed. The preferred embodiment the abrasive tools are for surface cleaning and tool sharpening in tool and cutter application or surface grinding or saw gumming.
[0019] The wheel is preferably hot pressed at temperature above 165oC  more precisely at 190oC. The wheel is hot pressed preferably at pressures above 5000PSI  most preferably at 3000-4000 PSI. The curing time at the temperature and pressure is 10-15 minutes more preferably 10 minutes.
[0020] The post curing may be unconventional for comparison with the technology provided by microwave. Preferably microwave generated by way of Magnetron supplies  a special oven built up for this purpose. The precise apparatus fitted with controls to ramp up temperature by digital mode. The oven can operate similar to conventional oven. The energy output directly converts itself to heat energy and perform with in the mass. More preferably heat loss is limited to minimum. The heat applied is measured directly from the mass. The conventional oven gives radiation through out the container and heat transfer takes place. The measuring point can be anywhere inside the chamber. The internal heat development with in the mass gives an excellent polymerisation at a shorter time. The time duration is very short thus power inputs have lower value than conventional.
EXAMPLE
[0021] An improvised resin bonded diamond 11V9 cup wheel of 100mm diamond by 2mm by 10mm thick by 20mm bore. In the first part of wheel making  a bond blend consisting modified epoxy phenolic novalac resin powder short flow phenolic novalac powder  both were sieved through 240mesh  synthetic cryolite  pyrite and potassium titanate. Each material weighed out separately and charged in to a ribbon blender  run for 20 minutes to get a homogenous powder. The powder was screened through a 240 mesh to breakdown lumps and agglomerates etc. Second part was wetting the grain weighed out grits of diamond  Sic filler and substitute sic grain were sieved through 80 mesh to filter out rough and wild grits if any. This was charged into a wetting machine allowed to run for 5 to 10 minutes with a lid on. The lid may then be removed to add liquid wetting agent preferably furfural. The addition was approximately 10CC to 25CC per kg. The wetting was for a period of 3 to 5 minutes with the lid on.
[0022] Then the wet grit particles were transferred to a sieve having a sieve no 80. This screening was mainly to break agglomerates. The wet mix was visually inspected and then transferred to a barrel mix. Mixing time was 15-30 minutes more preferably 20 minutes. First charge in the barrel was 80% of the blend. Second charge was slow addition of wet grain then followed by the balance blend of 20%. The final mix was a dry granular and the life of this mix 72 hrs under controlled condition that required for Resin bond mixes. The ingredients that had gone through the above said process are as per the table below.
S. No Ingredients Volume Percentage
1 D126 diamond 20.00
2 Silicon carbide# 180 10.40
3 Silicon carbide # 600 6.76
4 Phenolformaldehyde - Epoxy powder 3.64
5 Phenolformaldehyde – short flow resin 2.64
6 Cryolite 2.64
7 Iron sulfide 5.20
8 Potassium titanate 1.56
9 Porosity 47.16

[0023] The test wheel mix as per the above formulation was used to roll out an angular ring type of abrasive wheel  suitable for fixing on a back up body as per size 11V9. The compression and heating was done as per the standard conventional procedure. The heating time per mold was 15 to 20 minutes and temperature set was between 180oC to 200oC  preferably 185oC - 190oC most preferably 195 C±2oC. The cured wheel was then post cured in a microwave oven for 2 ½ Hrs. This is against the conventional post curing of 10 Hrs to 36 Hrs as a standard practice from start to end.
[0024] The cured test wheel thus finished to size and tested in a tool and cutter grinder. The operating speed was 3100 rpm the feed rate and plunge rate fixed. Wheel wear and temperature during grinding are monitored. The current production wheel  molded at 165oC and cured by conventional electrical oven was taken as master. The piece of test was a Carbide slab whose hardness and density are kept constant. Examination of 1st trial proved  that the test wheel compared to regular master wheel manufactured by using conventional practices. .
[0025] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can  by applying current knowledge  readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept  and  therefore  such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore  while the embodiments herein have been described in terms of preferred embodiments  those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

We Claim:

1. An abrasive body comprising:
abrasive particles; and
phenolic resins novalac bond for binding said abrasive particles  wherein
said abrasive particles include one of diamond  cubic boron nitride and a combination thereof.

2. The abrasive body as claimed in claim 1  wherein said phenolic resins novalac bond includes active filler  said active filler is a combination of two inorganic metallic Fluoride and Sulphide formulations.

3. The abrasive body as claimed in claim 2  wherein said phenolic resins novalac bond further includes Hexamethylenetetramine in a substantially higher percentage to facilitate faster curing.

4. The abrasive body as claimed in claim 3  wherein said phenolic resins novalac bond further includes an initiator for an advanced thermal setting during a hot pressing.

5. The abrasive body as claimed in claim 4  wherein said initiator is an Alkaline rare earth Salt.

6. The abrasive body as claimed in claim 2  wherein said active filler includes salts of one of sodium aluminium fluoride  iron sulfide and a combination thereof.

7. The abrasive body as claimed in claim 4  wherein said initiator is potassium titanate.

8. The abrasive body as claimed in claim 1  wherein said abrasive particles include fine grits of silicon carbide as substitute for diamond and cubic boron nitride.

9. The abrasive body as claimed in claim 8  wherein said silicon carbide constitute 5%-25% volume of the abrasive particles.

10. The abrasive body as claimed in claim 8  wherein said substitution is nearer to the grit size or the grit finer than the grit size of said diamond and cubic boron nitride.

11. The abrasive body as claimed in claim 10  wherein said finer grit act as filler.

12. The abrasive body as claimed in claim 10  wherein said finer grit is in the size of 30µ to 20µ.

13. The abrasive body as claimed in claim 1  wherein said a phenolic resins novalac bond includes epoxy material.

14. The abrasive body as claimed in claim 13  wherein said epoxy material constitute 10% to 40% weight of the phenolic resins novalac bond.

15. The abrasive body as claimed in claim 14  wherein said epoxy material constitute 15% to 30% weight of the phenolic resins novalac bond.

16. The abrasive body as claimed in claim 15  wherein said epoxy material constitute 25% to 30% weight of the phenolic resins novalac bond.

17. The abrasive body as claimed in claim 1  wherein said bond includes short flow straight phenol formaldehyde novalac powder.

18. The abrasive body as claimed in claim 17  wherein said short flow straight phenol formaldehyde novalac powder is a short flow with high hexa content.

19. The abrasive body as claimed in claim 2  wherein said active fillers constitute 15% volume of the bond.

20. The abrasive body as claimed in claim 4  wherein said initiator constitute 1% to 3% volume.

21. The abrasive body as claimed in claim 1  wherein said abrasive body is formed by thermosetting process.

22. The abrasive body as claimed in claim 21  wherein said thermosetting process is performed at a temperature of within 200oC ± 5 oC.

23. The abrasive body as claimed in claim 22  wherein said thermosetting process is performed under a time of dwelling of 15 minutes ± 2 minutes.

24. The abrasive body as claimed in claim 23  wherein said thermosetting process is performed at a pressure of 5000PSI.

25. The abrasive body as claimed in 23  wherein said abrasive body is cured by microwave technology.

Dated 20th Sep  2011

Dr. Kalyan Chakravarthy
Patent Agent

Abstract:
An abrasive tool includes a conventional abrasive grain or super abrasive grain bonded with improvised phenolic novalac resins. The thermosetting process carried out at 190oC ± 5 oC. The post curing is by an unconventional process that is by a microwave hot generator system.