Title of Invention

"A PROCESS FOR THE MANUFACTURE OF A PASSIVE ENERGY DEVICE (PED) FROM A HYSTERETIC SHEAR POLYMER"

Abstract

In the present invention there is provided a process for the manufacture of a passive energy device (PED) from a hysteretic shear polymer. The hysteretic shear polymer is based on Indian standard natural rubber (ISNR). The hysteretic shear polymer is prepared by processing the ISNR at a temperature in the range of 50°C to 100°C with suitable additives, such as china clay, semi-reinforcing furnace (SRF) carbon black, zinc oxide, steric acid, vulcaniser sulphur, tetra methyl thiuram (TMT), 2-mercapto benzo thiazole (MBT) and spikel oil. The hysteretic shear polymer so obtained is fabricated to make a passive energy device (PED). The passive energy device thus obtained provides shear strain as high as 200% linearity and shear strength > 25 kg per sq. cm.which and is useful for dissipating shear load due to seismic forces in buildings.

Full Text

The present invention relates to a process for the manufacture of a passive energy device (PED) from a hysteretic shear polymer. The invention particularly relates to the development of a natural-rubber based hysteretic shear polymer and a vibration damper device, for use in buildings and structures for dissipating shear load due to seismic forces. The main usages of the present invention will be in the building / construction sectors. Buildings and structures are vulnerable to suffer damage, and in extreme cases, to collapse, due to severe horizontal accelerations / vibrations caused by seismic forces unleashed during tremors and earthquakes. Scientists and technologists have been working to develop innovative methods and products to minimise this vulnerability of buildings and structures by incorporating seismic resistant components / parts. Some of the existing developments available in prior art literature employ materials which are visco-elastic in nature and which can enable buildings withstand shear loads without suffering damage and hence improve the chances of survival during and after earthquakes. The first adaptation of the technique of visco-elastic dampers for structural engineering applications is by Mahmoodi. Reference may be made to Mahmoodi, P., "Structural Dampers", Journal of the Structural Division, ASCE, 95(8), pp.1661-1672, 1969 and Mahmoodi et al (Zhang, R.H., Soong, T.T., and Mahmoodi, P.), "Seismic Response of Steel Frame Structures with Added Viscoelastic Dampers", Earthquake Engineering and Structural Dynamics, 18, pp.389-396, 1989. These studies report the results of an experimental investigation involving the testing of commercial shear-type visco-elastic dampers. These dampers were tested with varying shear strains and ambient temperature during the time of testing. The maximum shear strain upto which the test was conducted is 40% only. Reference may be made to Chang et al (Chang, K.C., Soong, T.T., Lai, M.L., and Nielsen, E.J. ,'Viscoelastic Dampers as Energy Dissipation Devices for Seismic Applications", Earthquake Spectra, 9(3), pp.371-388, 1993) reports of a series of tests conducted on three types of visco-elastic dampers of varying areas and volumes. Three sizes of visco-elastic damper elements tested by them were 25X38X5 mm, 50X38X7.5 mm and 150X75X4 mm. The frequency of excitation, the shear strain and ambient temperature were varied. The maximum shear strength reported in these experiments is 50% only, and the maximum frequency of excitation is 4 Hz. Reference may be made to Lai et. al (Lai, M.L., Kasai, K., and Chang, K.C., "Relation between Temperature Rise and Non-linearity of a Visco Elastic Damper", ISET Journal of Earthquake Technology, V.36, 1, pp.61-71.1999). They have consistently stressed the application of such dampers in seismic resistant design of buildings. Commercially available material shows linear behaviour only upto a value of 125% shear strain, if the temperature rise in the device material is artificially removed. The main drawbacks of the hitherto known prior art are: (i) Limited shear strength devices, with workable range of shear strain not exceeding 50%. This lower capability restricts the usefulness of these devices to withstand larger shear loads as would be experienced in moderate to severe earthquakes. The devices predominantly use synthetic rubber, and hence are not environment-friendly The existing devices are reported to have optimum performance only in a narrow temperature range of operation Hence, there is a definite need for the development of an improved visco-elastic polymer and a device based on the said polymer, which will be capable of withstanding shear loads to which structures and buildings are typically subjected during and after earthquakes. The main object of the present invention is to provide a process for the manufacture of hysteretic shear polymer and a passive energy device (RED) using the said polymer, which obviates the drawbacks of the hitherto known prior art. Another object of the present invention is to provide a natural-rubber based hysteretic shear polymer and a vibration damper device, for use in buildings and structures for dissipating shear load due to seismic forces. Yet another object of the present invention is to provide a process which is cost effective and environment friendly, as compared to the synthetic based polymers. Still another object of the present invention is to provide a damper device with hysteretic shear polymer having adequate shear strength, and the bond to metal should not govern the failure load. Still yet another object of the present invention is to provide a process for the manufacture of hysteretic shear polymer and a passive energy device (RED) using the said polymer, which has shear strain as high as 200% linearity and shear strength > 25 kg per sq. cm.. A further object of the present invention is to provide a RED having shear strain as high as 200% linearity without the requirement of further gadgets, unlike in presently available commercial material. A still further object of the present invention is to provide a RED, based on natural rubber, which is particularly suitable for tropical countries like India. A yet further object of the present invention is to provide a process which is cost effective as compared to the synthetic based polymers, and is particularly suitable for a small / medium scale industries. Another object of the present invention is to provide a device which can be suitably modified for other structures like bridge structures. Still another object of the present invention is to provide a device which can be effectively used for regular structures at the time of construction and also for retrofitting purposes. In the present invention there is provided a process for the manufacture of hysteretic shear polymer and a passive energy device (RED) using the said polymer. The hysteretic shear polymer is based on Indian standard natural rubber (ISNR). Since natural polymer of ISNR grade cannot sustain environmental effect and also tends to loose the physical properties, it cannot directly be used as structural material. In order to improve its engineering properties, vulcanisation process is carried out. Chemical ingredients are added to the basic form depending upon the expected finished product strength specifications. The hysteretic shear polymer is prepared by processing the ISNR at a temperature in the range of 50°C and 100°C with suitable additives, such as china clay, semi-reinforcing furnace (SRF) carbon black, zinc oxide, steric acid, vulcaniser sulphur, tetra methyl thiuram (TMT), 2-mercapto benzo thiazole (MET) and spikel oil. The hysteretic shear polymer so obtained is fabricated to make a passive energy device (RED), which is useful for dissipating shear load due to seismic forces in buildings. Accordingly, the present invention provides a process for the manufacture of hysteretic shear polymer, which comprises masticating raw natural polymer at a temperature in the range of 50°C and 100°C, adding both chemical and natural resin and continuing the masticating process, adding china clay, semi-reinforcing furnace (SRF) carbon black, zinc oxide, steric acid and spikel oil, and continuing the masticating process, followed by adding vulcaniser sulphur, along with tetra methyl thiuram (TMT), 2-mercapto benzo thiazole (MBT) and masticating to obtain hysteretic shear polymer. In an embodiment of the present invention, the raw natural polymer is raw natural rubber of Indian standard natural rubber (ISNR) grade. In another embodiment of the present invention, the additives are of the order of 60 to 85 wt% of the raw natural rubber. In still another embodiment of the present invention, the masticating process is carried out in a roller machine with adjustable rollers and having temperature control means such as cool water circulating system. In yet another embodiment of the present invention, during the mastication process, the twin rollers are cooled continuously to maintain the temperature range. In still yet another embodiment of the present invention, the masticating process is carried out at each step for a time period of the order of minutes. 6 In a further embodiment of the present invention, the hysteretic shear polymer essentially consists of the ingredients in the relative weight proportions: (Table Removed) Accordingly, the present invention provides a process for the manufacture of a passive energy device (RED) from the said hysteretic shear polymer as obtained above, which comprises: (i) cutting to required size the hysteretic shear polymer; (ii) applying by known methods one or more layer of adhesive coating onto pre-fabricated steel plates having knurled surface, allowing to cure; placing the polymer piece(s) between the said adhesive coated steel plates and subjecting to a temperature in the range of 100 to 500° C and a constant pressure in the range of 10 kg/cm2 to 15 kg/cm2 for a time period of 20 to 45 minutes. In an embodiment of the present invention, the passive energy device (FED) consists of a sandwich having two end plates, a middle plate and two pieces of polymer between the said middle and end plates. In another embodiment of the present invention, the passive energy device (RED) has linearity for shear strain up to as high as 200%. In still another embodiment of the present invention, the passive energy device (RED) has shear strength greater than 25 kg/cm2. In yet another embodiment of the present invention, the passive energy device (RED) for lower force capacity is made from hysteretic shear polymer based on other polymers such as butyl and neoprene. Accordingly, the present invention provides a passive energy device (RED) made by the above described process from the hysteretic shear polymer as obtained above. The device developed herein based on the hysteretic shear polymer of the present invention, is a passive energy device (RED) useful to dissipate the shear load caused by seismic motion in buildings. By the application of this polymerbased device in buildings as a visco-elastic brace, the structures can withstand large shear loads and damage to buildings can be minimized. The device of the present invention allows modification for application to structures like bridge structures, without altering the principle of the method. This device has the advantage of using it for regular structures at the time of construction and also for retrofitting purposes. The device developed can take up the maximum load capacity of 8 t, and exhibit linear behaviour up to 200% shear strain under low cycle hysteresis shear load. The device in this invention has been developed based on ISNR grade natural polymer with suitable additives, as detailed herein, processed and fabricated for dissipating shear load due to seismic forces in buildings connected as a brace." The device can be used either as an X-brace with hinges at the two connecting ends or at the top of the K-brace or Chevron brace. In the case of a Chevron brace, the top and bottom plates of the device can be connected to the top floor whereas the middle plate can be connected to the top of the Chevron brace. Suitable provisions can be introduced in the connection such that the device is free to move in the plane perpendicular to the shear loading direction. The polymer developed in this invention is a natural rubber based material, and the device exhibits linearity for shear strain up to as high as 200%. The novelty of the present invention resides in providing an environment-friendly as well as cost effective process for the manufacture of hysteretic shear polymer and a passive energy device (RED) using the said hysteretic shear polymer, which is capable of sustaining large axial load, has wide range of linear shear strain and possesses sufficient energy dissipation characteristics to dissipate the shear load caused by seismic disturbances. The novelty has been achieved by the non-obvious inventive steps of processing natural polymer (ISNR) with additives such as herein described and hence providing an environment-friendly as well cost effective process, as compared to the synthetic based polymers of the hitherto known prior art. The novel process, having the non-obvious inventive steps, for the manufacture of hysteretic shear polymer and a passive energy device (RED) using the said polymer, provides shear strain as high as 200% linearity and shear strength > 25 kg per sq. cm.. The high shear strain of 200% linearity is exhibited without the requirement of further gadgets, unlike in presently available commercial material. In the process of the present invention the hysteretic shear polymer is prepared by the steps comprising: 1. The roller machine is switched on and spacing between rollers adjusted to attain ideal temperature between 50°C and 100°C. 2. Masticating the raw polymer in the roller machine for at least some minutes to reduce its molecular weight. 3. Adding both the chemical resin and natural resin and continuing masticating process for a few minutes. 4. Adding china clay, semi-reinforcing furnace (SRF) carbon black, zinc oxide, steric acid and spikel oil, and continuing the masticating process. 5. Adding vulcaniser sulphur, along with tetra methyl thiuram (TMT), 2- mercapto benzo thiazole (MBT) and masticating to obtain hysteretic shear polymer. The following examples are given by way of illustration of the process of the present invention in actual practice and therefore should not be constued to limit the scope of the present invention. Example-1 A batch of hysteretic shear polymer was prepared by the process of the present invention, using the ingredients as given in Table-1 below: Table -1 (Table Removed) The hysteretic shear polymer obtained was of shear strength, greater than 25 kg/cm2. The fabrication of a FED based on the hysteretic shear polymer obtained was carried as follows: 1. Pre- fabricated steel plates having knurling surface (the centre plate having intermediate spaces on both sides and end plates on only one side, if a brace configuration is chosen) are initially applied with an adhesive with a brush. 2. After a few minutes of duration, over the dried coating, apply another adhesive, and allow it to cure. 3. The processed polymer composition is cut to the required size. As an example, in this RED component, two equal pieces of 12.5 mm thickness of NR composition with the dimension of 100 mm x 150 mm is made. 4. Keep the mould in the temperature controlled press. 5. After the mould reaches the required temperature, slide the RED components into the mould, i.e., the end plate with polymer piece on top, middle plate and another polymer piece with end plate in the required position. 6. Place the mould inside the press, and set the temperature to the temperature between 100° and 500°. Maintain a constant pressure of 10 kg/cm2 to 15 kg/cm2 on the mould. Allow the process for at least 20 to 45 minutes. 7. Remove the mould and dismantle it to take out the RED. Example-2 A second batch of hysteretic shear polymer was prepared by the process of the present invention, using the ingredients as given in Table-1 above. The hysteretic shear polymer obtained was of shear strength, greater than 25 kg/cm2. The fabrication of a RED based on the hysteretic shear polymer obtained was carried out as per the process detailed above in example-1. In order to check the repeatability of the performance characteristics, two lots of specimens were made, as obtained in the examples 1 and 2 above, and the tests were carried out for checking the repeatability of characteristics. The typical devices (PEDs) obtained, in the examples 1 and 2, were subjected up to 8 t as a failure load, and the typical response curves obtained from such a device are given in figures 1 and 2 of the drawings accompanying this specification. In figure 1 depicts the typical behaviour of the device under static load. Figure 2 depicts a typical hysterisis loop of the device. The device can develop i and y within the linear range of 25 kg/cm2 and 200% strain respectively as seen from the mean curve in figure 1 under static shear test. Examples of the typical stable hysteresis curves for the device under constant displacement cycles at a value of 64% shear strain and 0.25 Hz frequency are shown in figure 2 of the drawings. The devices were also tested for frequencies higher than 0.25 Hz, namely, 1.0 Hz and 4.0 Hz. The properties have been found to be generally uniform in this frequency range. This range of frequencies was adopted as this is the useful range in which the natural frequencies of most of the building structures lie. The device has to be suitably connected to the building in the form of a brace. When the building is subjected to the ground motion, in the predominant first mode under low frequency range, the maximum shear load can be dissipated through the passive energy damper. The mechanical characteristics of the damper device (PEDs) obtained in the examples 1 and 2 above are given in table-2 below: Table – 2 (Table Removed) The main advantages of the invention are: 1. The process is cost effective as compared to the synthetic based polymers, and is particularly suitable for a small / medium scale industries. 2. Provides a natural-rubber based hysteretic shear polymer and a vibration damper device, for use in buildings and structures for dissipating shear load due to seismic forces. 3. Provides a process which is cost effective and environment friendly, as compared to the synthetic based polymers. 4. Provides a damper device (PED) with hysteretic shear polymer having adequate shear strength, and the bond to metal does not govern the failure load. 5. Provides a process for the manufacture of hysteretic shear polymer and a passive energy device (PED) using the said polymer, which has shear strain as high as 200% linearity and shear strength > 25 kg per sq. cm.. 6. Shear strain as high as 200% linearity is exhibited without the requirement of further gadgets, unlike in presently available commercial material. 7. The natural rubber based PED is particularly suitable for tropical countries. 8. The device can be suitably modified for other structures like bridge structures. 9. The device can be effectively used for regular structures at the time of construction and also for retrofitting purposes. We Claim: 1. A process for the manufacture of a passive energy device (FED) from a hysteretic shear polymer, which comprises: a. preparing hysteretic shear polymer by masticating raw natural rubber, at a temperature in the range of 50°C to 100°C, adding both chemical and natural resin as herein described and continuing the masticating process, adding china clay, semi-reinforcing furnace (SRF) carbon black, zinc oxide, steric acid and spikel oil, and continuing the masticating process, followed by adding vulcaniser sulphur, along with tetra methyl thiuram (TMT), 2-mercapto benzo thiazole (MBT) and masticating to obtain hysteretic shear polymer, b. cutting the hysteretic shear polymer obtained in step (a) into pieces, c. applying by known methods one or more layer of adhesive coating onto pre-fabricated steel plates having knurled surface and allowing it to cure, d. placing the hysteretic shear polymer piece(s) obtained in step (b), between the said adhesive coated steel plates obtained in step (c) and subjecting it to a temperature in the range of 100 to 500° C and a constant pressure in the range of 10 kg/cm2 to 15 kg/cm2 for a period of 20 to 45 minutes to obtain the desired product having linearity for shear strain up to as high as 200% and shear strength greater than 25 kg/cm2. 2. A process as claimed in claim 1, wherein the passive energy device (RED) consists of a sandwich having two end plates, a middle plate and two pieces of polymer between the said middle and end plates. 3. A process as claimed in claim 1, wherein in step (a) the raw natural rubber is raw natural rubber of Indian standard natural rubber (ISNR) grade. 4. A process as claimed in claim 1, wherein the masticating process is carried out in a roller machine with adjustable rollers and having temperature control means such as cool water circulating system. 5. A process as claimed in claim 1, wherein in step (a) during the mastication process, the twin rollers are cooled continuously to maintain the temperature range. 6. A process as claimed in claim 1, wherein in step (a) the masticating process is carried out at each step for a time period of the order of minutes. 7. A process as claimed in claim 1, wherein in step (a) the ingredients used are in the relative weight proportion of 1 part by weight of natural rubber and are 0.1 -0.2 part of china clay, 0.3-0.4 part of semi-reinforcing furnace (SRF) carbon powder 0.05-0.06 part of Zinc oxide 0.025-0.035 part of Steric acid, 0.008-009 part of Tetra methyl thiuram (TMT), 0.01-0.02 part of 2- mercapto benzo thiazole (MBT), 0.02-0.03 part of Vulcaniser - sulphur, 0.03-0.04 part of Ant resin, 0.03-0.04 part of Gum and 0.08-0.09 part of Spikel oil. 8. A process for the manufacture of a passive energy device (FED) from the hysteretic shear polymer, substantially as herein described with reference to the examples and drawings accompanying this specification.

Documents:

510-DEL-2003-Abstract-(17-09-2008).pdf

510-del-2003-abstract.pdf

510-DEL-2003-Claims-(17-09-2008).pdf

510-DEL-2003-Claims-(17-11-2008).pdf

510-del-2003-claims.pdf

510-DEL-2003-Correspondence-Others-(17-09-2008).pdf

510-DEL-2003-Correspondence-Others-(17-11-2008).pdf

510-del-2003-correspondence-others.pdf

510-del-2003-correspondence-po.pdf

510-DEL-2003-Description (Complete)-(17-09-2008).pdf

510-DEL-2003-Description (Complete)-(17-11-2008).pdf

510-del-2003-description (complete).pdf

510-del-2003-drawings.pdf

510-DEL-2003-Form-1-(17-09-2008).pdf

510-del-2003-form-1.pdf

510-DEL-2003-Form-18-(17-09-2008).pdf

510-del-2003-form-18.pdf

510-DEL-2003-Form-2-(17-09-2008).pdf

510-del-2003-form-2.pdf

510-DEL-2003-Form-3-(17-09-2008).pdf

510-del-2003-form-3.pdf