Title of Invention	"A PROCESS FOR THE PREPARATION OF NITRILE RUBBER BASED ADHESIVE FOR AUTOMOTIVE GASKET"
Abstract	A process for the preparation of nitrile rubber based adhesive for automotive gasket which comprises milling of nitrile robber having high acrylonitrile with additive softening agent, vulcanizing agent and lubricating metal in a twin roll shear mill; dissolving the milled mixture of rubber and ingredients in a mixture of solvent of methyl ethyl ketone and methyl isobutyl ketone and stirring the said mixture in a vertical churner /reactor to get a homogenous solution ; adding a solution of about 23%w/v of phenolic resin having been compounded with hexamine to the homogenous mixture and further stirring the mixture solution; adding antioxidant to the homogenous mixture to obtain the nitrile rubber based adhesive.

Title of Invention

"A PROCESS FOR THE PREPARATION OF NITRILE RUBBER BASED ADHESIVE FOR AUTOMOTIVE GASKET"

Abstract

A process for the preparation of nitrile rubber based adhesive for automotive gasket which comprises milling of nitrile robber having high acrylonitrile with additive softening agent, vulcanizing agent and lubricating metal in a twin roll shear mill; dissolving the milled mixture of rubber and ingredients in a mixture of solvent of methyl ethyl ketone and methyl isobutyl ketone and stirring the said mixture in a vertical churner /reactor to get a homogenous solution ; adding a solution of about 23%w/v of phenolic resin having been compounded with hexamine to the homogenous mixture and further stirring the mixture solution; adding antioxidant to the homogenous mixture to obtain the nitrile rubber based adhesive.

Full Text	This invention relates to the process for the preparation of "Nitrite rubber based adhesive. Particularly this invention relates to the preparation of nitrite rubber adhesive which can bond surfaces of tin and asbestos, for making automotive gaskets. The nitrite phenolic contact adhesives are therefore, used in a wide variety of structural and non structural applications. The most important property of nitrite rubbers is their resistance towards the petroleum oils. This property increased as the acrylonitrile content of the co-polymer is increased. The increase in acrylonitirle content also improves its compatability with phenolic resins. The phenolic resins so chosen, functions as viscosity stabiliser, tackifier and also as a cross linking resin with the unsaturation and carboxyl groups of the nitrite rubber and these impart good strength, durability and heat resistance. The strength of such a structural bond depends not only upon the adhesive but also on the processing conditions such as heat cure schedule. The ratio of phenolic resin to nitrite rubber may be varied over a broad range and this ratio determines the property of the adhesive. The literature on nitrite - phenolic contact adhesives is available in the form of patents and also technical articles as shown below: M.H.Pintell U.S.P.2,711,380 (1955) R.J.Reid U.S.P. 2,514,222 (1950) HAHusseyand O.D.Wright U.S.P. 2,653,884 (1953) A.W.Bethune SAMPE.J 11(3) 4 (1975) These patents have described nitrite - phenolic contact adhesives especially useful for bonding rubber and other materials and are normaly termed as non-structural adhesives, due to the fact that the bonds strengths developed are not significant. These nitrile - phenolic contact adhesive bonds are not resistant towards ketonic solvents, and also at the same time the curing temperatures were of about the order of 250°C for over a long period of 30 minutes. Therefore, the present invention provides the preparation of nitrile rubber based adhesives for manufacture of gaskets required for automobiles which exhibit excellent resistance towards ketonic solvents. The curing temperatures are reduced drastically to the order of 180 - 200°C for much lower durations such as 20 minutes. A principal novel feature of the compositions of the present invention is that the methylol groups of phenolic resin react with the unsaturation present in the nitrile rubbers and thereby giving a chroman type of ring structure and also in some cases it reacts with the carboxy group present in the nitrile rubber, giving a wide variety of cross linked structures responsible for the excellent bonding properties. These adhesive compositions give bonds with high peel strength and impact resistance. These properties are particularly useful in bonding the tin surfaces and asbestos surfaces to give high quality gaskets for automobiles. Accordingly the present invention provides a formulation for the preparation of nitrile rubber based exhibits excellent resistance towards hydrocarbons, ketonic solvents; and also esjstance towards the antifreeze solutions. These properties are must for aking a successful and high performance gasket adhesive. All the raw V materials used may be of commercial grade. adhesive for the automobiles which/ The process of invention is described here under: The nitrile rubber having medium to high percentage (15 - 35%) acrylonitrile was milled over twin roll rubber mill while incorporating the additives such as stearic acid, sulphur, zinc oxide in it. The phenolic resin which is used as tackifier in this invention is a novolac resin compounded with hexamine to an extent of 6-15%. The major advantage of this type of novolac resins is that no water of reaction is evolved during the cure with hexamine. The amount of hexamine in the high end of this range is used where optimum hot strength is required. The molecular weights of phenolic novolac resin used in this investigation are in the range of 500 - 900. The milled rubber sheets were then cut into small pieces and were added into a stainless steel vertical churner and then dissolved in a mixture of methyl ethyl ketone and methylisobutylketone, mixed solvents. Seperately, phenolic resin was dissolved in methylethylketone and this solution was then added to the vertical reactor. The adhesive is then discharged and stored in the metal containers. To evaluate the bond strength of the adhesive, the adhesive was applied by K-coater on both the tin plate and the asbestos sheet of 5cm x 5cm size producing a thickness of approximately 0.03mm. The composites were then prepared by pressing both the surfaces in a hydraulic press. These are termed as wet laminated composites. In the other set of composites, the gummed surfaces of tin and asbestos were dried at 130°C for 15 - 20 sec. and then laminated in the hydraulic press. These laminates are termed as heat reactivated laminates. These laminates were then cured for 10 - 30 min. at temperatures ranging from 150°C - 230°C in a hot air oven. The samples were then tested for their resistance to methylethylketone by immersing the composite panels for 2 h. in this solvent. The bond strength was estimated by driving a 2.5cm wide stainless steel spatula at 45°C from the interface of the joint as hard as possible while preventing the bowing of the spatula. The percent amount of asbestos facing remaining on the tin surface was assessed visually. This test was also conducted on series of samples after immersion in wateranti freeze mixture at 90°C for 24 h. In another test, the resistivity of the cured neoprene rubber with phenolic resin adhesive on tin surface was tested for the fluid resistance in fluids such as methylethylketone and the antifreeze solutions. The tests were conducted on previously solvent degreased tin plates of 100mm x 25mm size, dried and preweighed before the application of the adhesive. The tin plates were then coated with this adhesive to give a thickness of approximately 0.03mm. After air drying for 30 min., the tin plates were baked at temperatures ranging from 150°C -230°C for 5-30 min. The tin plates were then weighed to give the weight of the adhesive applied on them. The adhesive coated tin plates were then placed in a soxhlet extraction apparatus and extracted with methylethylketone for 5 h. The tin plates were then removed, dried and were re-weighed. The percentage adhesive remained on the tin plates was then estimated. Similar test pieces were prepared using stainless steel panels instead of tin panels for water - anti freeze 1:1 mixture resistance test as the anti freeze mixture effects the tin plates. The samples were dipped in boiling anti freeze -water mixture for 5 h. in this test. Accordingly, the present invention provides a process for the preparation of nitrile rubber based adhesive for automotive gasket which comprises: i milling of nitrile rubber having 15-35% acrylonitrile content as herein described with additive of softening agent ranging 0-1% , vulcanizing agent as sulphur ranging 0-3% and lubricating metal oxide ranging 0-3% such as herein described in a twin roll shear mill; ii. dissolving the milled mixture of rubber and ingredients obtained in step i) in a mixture of solvent of methyl ethyl ketone and methyl isobutyl ketone and the ratio of the said solvents being in the range of 1:1 to 2:1 and the ratio of said rubber mixture and that of the solvent being kept ranging 1:4 to 1:6.5 , stirring the said mixture in a vertical churner /reactor at 60-70 rpm , temperature ranging 30-35°C for a period ranging 6-8 hours to get a homogenous solution ; iii. adding a solution of about 23%w/v of phenolic resin of novolac type containing hexamine ranging 6-15% in methyl ethyl ketone to the homogenous mixture as obtained in step ii) and further stirring the mixture solution for a period of about 1 hour; iv. adding antioxidant such as herein described to the homogenous mixture as obtained in step iii) and the concentration of antioxidant addition being in the range of o.l to 0.2 of the weight of total phenolic resin added in step iii) to obtain the nitrile rubber based adhesive ; characterized in that the adhesive contains 52-60% nitrile rubber and 40-47% of phenolic resin. In yet another embodiment of the present invention metal oxides used is such as zinc oxide, magnesium oxide and calcium oxide. In still another embodiment of the present invention softening agents used is such as stearic acid or any lower fatty acids having cabon atom less than-18. In still another embodiment of the present invention a vulcanizing agent used is such as sulphur. In still another embodiment of the present invention the antiodixants used are such as butyl hydroxyl anisole, butylhydroxy toluene. In still another embodiment of the present invention ketonic solvents used are such as Methyl ethyl ketone (MEK), Methyl isobutyl ketone (MIBK) or mixture thereof ^3ag^MB^^5--^-aH4-4^4 - h5-trmes-ef4otaL The following examples are given in the way of illustration and therefore should not be construed to limit the scope of the present invention. EXAMPLE- 1 A medium -high acrylonitrile rubber 1042 having specific gravity of 0.98 and a mooney viscosity of 50+10(1kg) was milled in a twin roll shear mill with steric acid (1.8g), sulphur (60g) and zinc oxide (60g). The milled rubber was taken in a vertical chumer and to this methylethylketone (4 Its) and methyl isobutyl ketone (2.3 Its) were added and stirred at 60 rpm for 8h. At the end of this period, the nitrile rubber with other ingredients dissolved in the solvent mixture and to which separately dissolved phenolic resin of about 23.2%w/v in methyl ethylketone was added. The uniform nitrile rubber adhesive of density of 0.85g/ml, solids (%) 20 and has viscosity as determined by Ford Cup 4 is 100 sec. Wet laminates and also heat reactivated laminates were prepared using tin plate and asbestos sheets. These were evaluated for their bond strength and also fluid resistance and the results are shown in the following tables: ADHESIVE BOND TESTS (Table Removed)FLUID RESISTANCE TESTS (Table Removed)It is observed that a cure schedule of 30 min at 180°C gives bond exhibiting resistance towards methylethylketone and the antifreeze solutions. EXAMPLE - 2 Nitrile rubber medium - high acrylonitrile rubber having mooney viscosity 50 + 10 and having acrylonitrile 31 - 35%(1kg) was milled in a twin roll mill along with sulphur (1.6g), zinc oxide (48g). The sheet thus obtained was cut into small strips and added to vertical churner containing methyl isobutylketone (2.5lts) and methylethylketone (2.5lts). After a period of 6h., the rubber solution was homogenous. A novolac phenolic resin compounded with hexamine to an extent of 10%(920g} was dissolved in methylethylketone (2.5 Its), separately and this was added to the rubber solution and stirred for an extra 1h. To this an antioxident butylhydroxy anisole 0.1% on the total weight of the resin was added and then stored in metal containers. The uniform nitrile rubber adhesive had density of 0.9g/ml, solids 25% and viscosity of 100 sec. as determined by Ford Cup 4. The wet laminated and heat reactivated laminates were prepared using tin and asbestos sheets and were tested for their bond strength and fluid resistance tests as described earlier. The results are given in the following tables: ADHESIVE BOND TESTS (Table Removed)FLUID RESISTANCE TESTS (Table Removed)It is observed that at cure schedule of 30min at 180°C gave excellent resistane in methylethylketone and the antifreeze solutions to an extent of 100% and the bond strength also to the extent of 90% on the wet laminated sheets. EXAMPLE - 3 Nitrile rubber medium - high acrylonitrile rubber having mooney viscosity 45 and having a specific gravity of 0.98 Ikgywas milled in a twin roll mill and to this methyl isobutylketone (2 Its) and methylethylketone (2.08 Its) were added and stirred at 35°C over a period of 6h. At this time a clear nitrile rubber solution was obtained. To this novolac phenolic resin compounded with hexamine to an extent of 15% (660g.' 'was separately dissolved in methylethylketone (2.08 Its.) and this was added to the rubber solution. To this an antioxident butylhydroxy anisole 0.2% on the total weight of the resins was added and stored. This adhesive had density of 0.90g/ml, solids content of 25% and viscosity of 130 sec. as determined by Ford Cup 4. This adhesive was evaluated for the bond strength and fluid resistance of the wet and heat reactivated laminates. The results are given in the following tables: ADHESIVE BOND TESTS (Table Removed)FLUID RESISTANCE TESTS (Table Removed)EXAMPLE - 4 Nitrile rubber medium - high acrylonitrile rubber having mooney viscosity - 55 (1kg) was milled in a twin roll mill and was compounded with sulphur (10.8g) for 1 hour. This milled rubber was cut into small peices and dissolved in methyl isobutylketone (2.25 Its) and methylethylketone (2.25 Its.) in a vertical churner and stirred at 60 rpm over a period of 6h. A novolac phenolic having 13% hexamine; (794 g),was separately dissolved methylethylketone (2.25 Its.) and this was added to the rubber solution and stirred for 1 h. To this an antioxident butylhydroxy toulene 0.2% on the total weight of the solids was added and stored. This adhesive had density of 0.90g/ml, solids content 25% and viscosity of 125 sec. as determined by Ford Cup 4. This adhesive was evaluated for the bond strength and fluid resistance of the wet and heat reactivated laminates of tin and asbestos. The results are given in the following tables: ADHESIVE BOND TESTS (Table Removed)FLUID RESISTANCE TESTS (Table Removed)EXAMPLE - 5 The adhesive as prepared in example-4 was cured at different schedules ranging from 200 - 250°C for 8 - 20min. The wet laminated sheets of tin and asbestos were tested for the fluid resistance in methylethylketone. The results are given in the table: CURE SCHEDULE OF TIN-ASBESTOS COMPOSITES Application of Cure Schedule Time of Soak Results adhesive on °C at Min inMEK(h) (Table Removed)The main advantages of this process are : 1) The utilization of mixture of solvents i.e., methylethylketone and methyl isobutyl ketone to dessolve the nitrite rubber so as to get low viscosity product with high solid content. 2) The utilization of novolac phenolic resin having free hexamine content of 6- 15% helps in bonding the asbestos sheets with aluminium sheets and also We claim: 1. A process for the preparation of Nitrile rubber based adhesive for automotive gasket which comprises: i) milling of nitrile robber having 15-35% acrylonitrile content as herein described with additive of softening agent ranging 0-1% , vulcanizing agent as sulphur ranging 0-3% and lubricating metal oxide ranging 0-3% such as herein described in a twin roll shear mill; ii) dissolving the milled mixture of rubber and ingredients obtained in step i) in a mixture of solvent of methyl ethyl ketone and methyl isobutyl ketone and the ratio of the said solvents being in the range of 1:1 to 2:1 and the ratio of said rubber mixture and that of the solvent being kept ranging 1:4 to 1:6.5 , stirring the said mixture in a vertical churner /reactor at 60-70 rpm , temperature ranging 30-35°C for a period ranging 6-8 hours to get a homogenous solution ; iii) adding a solution of about 23%w/v of phenolic resin of novolac type containing hexamine ranging 6-15% in methyl ethyl ketone to the homogenous mixture as obtained in step ii) and further stirring the mixture solution for a period of about 1 hour; iv) adding antioxidant such as herein described to the homogenous mixture as obtained in step iii) and the concentration of antioxidant addition being in the range of o.l to 0.2 of the weight of total phenolic resin added in step iii) to obtain the nitrile rubber based adhesive ; characterized in that the adhesive contains 52-60% nitrile rubber and 40-47% of phenolic resin. 5. A process for the preparation of Nitrile rubber based adhesive for automotive gasket substantially as herein described with reference to the examples.

Full Text

This invention relates to the process for the preparation of "Nitrite rubber based adhesive. Particularly this invention relates to the preparation of nitrite rubber adhesive which can bond surfaces of tin and asbestos, for making automotive gaskets.
The nitrite phenolic contact adhesives are therefore, used in a wide variety of structural and non structural applications. The most important property of nitrite rubbers is their resistance towards the petroleum oils. This property increased as the acrylonitrile content of the co-polymer is increased. The increase in acrylonitirle content also improves its compatability with phenolic resins. The phenolic resins so chosen, functions as viscosity stabiliser, tackifier and also as a cross linking resin with the unsaturation and carboxyl groups of the nitrite rubber and these impart good strength, durability and heat resistance. The strength of such a structural bond depends not only upon the adhesive but also on the processing conditions such as heat cure schedule. The ratio of phenolic resin to nitrite rubber may be varied over a broad range and this ratio determines the property of the adhesive.
The literature on nitrite - phenolic contact adhesives is available in the form of patents and also technical articles as shown below:
M.H.Pintell U.S.P.2,711,380 (1955) R.J.Reid U.S.P. 2,514,222 (1950) HAHusseyand O.D.Wright U.S.P. 2,653,884 (1953) A.W.Bethune SAMPE.J 11(3) 4 (1975)
These patents have described nitrite - phenolic contact adhesives especially useful for bonding rubber and other materials and are normaly termed

as non-structural adhesives, due to the fact that the bonds strengths developed are not significant. These nitrile - phenolic contact adhesive bonds are not resistant towards ketonic solvents, and also at the same time the curing temperatures were of about the order of 250°C for over a long period of 30 minutes. Therefore, the present invention provides the preparation of nitrile rubber based adhesives for manufacture of gaskets required for automobiles which exhibit excellent resistance towards ketonic solvents. The curing temperatures are reduced drastically to the order of 180 - 200°C for much lower durations such as 20 minutes.
A principal novel feature of the compositions of the present invention is that the methylol groups of phenolic resin react with the unsaturation present in the nitrile rubbers and thereby giving a chroman type of ring structure and also in some cases it reacts with the carboxy group present in the nitrile rubber, giving a wide variety of cross linked structures responsible for the excellent bonding properties. These adhesive compositions give bonds with high peel strength and impact resistance. These properties are particularly useful in bonding the tin surfaces and asbestos surfaces to give high quality gaskets for automobiles.
Accordingly the present invention provides a formulation for the preparation of nitrile rubber based
exhibits excellent resistance towards hydrocarbons, ketonic solvents; and also
esjstance towards the antifreeze solutions. These properties are must for aking a successful and high performance gasket adhesive. All the raw V materials used may be of commercial grade.
adhesive for the automobiles which/

The process of invention is described here under:
The nitrile rubber having medium to high percentage (15 - 35%) acrylonitrile was milled over twin roll rubber mill while incorporating the additives such as stearic acid, sulphur, zinc oxide in it. The phenolic resin which is used as tackifier in this invention is a novolac resin compounded with hexamine to an extent of 6-15%.
The major advantage of this type of novolac resins is that no water of reaction is evolved during the cure with hexamine. The amount of hexamine in the high end of this range is used where optimum hot strength is required. The molecular weights of phenolic novolac resin used in this investigation are in the range of 500 - 900. The milled rubber sheets were then cut into small pieces and were added into a stainless steel vertical churner and then dissolved in a mixture of methyl ethyl ketone and methylisobutylketone, mixed solvents. Seperately, phenolic resin was dissolved in methylethylketone and this solution was then added to the vertical reactor. The adhesive is then discharged and stored in the metal containers.
To evaluate the bond strength of the adhesive, the adhesive was applied by K-coater on both the tin plate and the asbestos sheet of 5cm x 5cm size producing a thickness of approximately 0.03mm. The composites were then prepared by pressing both the surfaces in a hydraulic press. These are termed as wet laminated composites. In the other set of composites, the gummed surfaces of tin and asbestos were dried at 130°C for 15 - 20 sec. and then laminated in the hydraulic press. These laminates are termed as heat reactivated laminates.

These laminates were then cured for 10 - 30 min. at temperatures ranging from 150°C - 230°C in a hot air oven. The samples were then tested for their resistance to methylethylketone by immersing the composite panels for 2 h. in this solvent. The bond strength was estimated by driving a 2.5cm wide stainless steel spatula at 45°C from the interface of the joint as hard as possible while preventing the bowing of the spatula. The percent amount of asbestos facing remaining on the tin surface was assessed visually. This test was also conducted on series of samples after immersion in wateranti freeze mixture at 90°C for 24 h.
In another test, the resistivity of the cured neoprene rubber with phenolic resin adhesive on tin surface was tested for the fluid resistance in fluids such as methylethylketone and the antifreeze solutions. The tests were conducted on previously solvent degreased tin plates of 100mm x 25mm size, dried and preweighed before the application of the adhesive. The tin plates were then coated with this adhesive to give a thickness of approximately 0.03mm. After air drying for 30 min., the tin plates were baked at temperatures ranging from 150°C -230°C for 5-30 min. The tin plates were then weighed to give the weight of the adhesive applied on them. The adhesive coated tin plates were then placed in a soxhlet extraction apparatus and extracted with methylethylketone for 5 h. The tin plates were then removed, dried and were re-weighed. The percentage adhesive remained on the tin plates was then estimated.
Similar test pieces were prepared using stainless steel panels instead of tin panels for water - anti freeze 1:1 mixture resistance test as the anti freeze mixture effects the tin plates. The samples were dipped in boiling anti freeze -water mixture for 5 h. in this test.
Accordingly, the present invention provides a process for the preparation of nitrile rubber based adhesive for automotive gasket which comprises:
i milling of nitrile rubber having 15-35% acrylonitrile content as herein described with additive of softening agent ranging 0-1% , vulcanizing agent as sulphur ranging 0-3% and lubricating metal oxide ranging 0-3% such as herein described in a twin roll shear mill;
ii. dissolving the milled mixture of rubber and ingredients obtained in step i) in a mixture of solvent of methyl ethyl ketone and methyl isobutyl ketone and the ratio of the said solvents being in the range of 1:1 to 2:1 and the ratio of said rubber mixture and that of the solvent being kept ranging 1:4 to 1:6.5 , stirring the said mixture in a vertical churner /reactor at 60-70 rpm , temperature ranging 30-35°C for a period ranging 6-8 hours to get a homogenous solution ; iii. adding a solution of about 23%w/v of phenolic resin of novolac type containing hexamine ranging 6-15% in methyl ethyl ketone to the homogenous mixture as obtained in step ii) and further stirring the mixture solution for a period of about 1 hour;
iv. adding antioxidant such as herein described to the homogenous mixture as obtained in step iii) and the concentration of antioxidant addition being in the range of o.l to 0.2 of the weight of total phenolic resin added in step iii) to obtain the nitrile rubber based adhesive ; characterized in that the adhesive contains 52-60% nitrile rubber and 40-47% of phenolic resin.

In yet another embodiment of the present invention metal oxides used is such as zinc oxide, magnesium oxide and calcium oxide.
In still another embodiment of the present invention softening agents used is such as stearic acid or any lower fatty acids having cabon atom less than-18.
In still another embodiment of the present invention a vulcanizing agent used is such as sulphur.
In still another embodiment of the present invention the antiodixants used are such as butyl hydroxyl anisole, butylhydroxy toluene. In still another embodiment of the present invention ketonic solvents used are such as Methyl ethyl ketone (MEK), Methyl isobutyl ketone (MIBK) or mixture thereof ^3ag^MB^^5--^-aH4-4^4 - h5-trmes-ef4otaL
The following examples are given in the way of illustration and therefore should not be construed to limit the scope of the present invention.
EXAMPLE- 1
A medium -high acrylonitrile rubber 1042 having specific gravity of 0.98 and a mooney viscosity of 50+10(1kg) was milled in a twin roll shear mill with steric acid (1.8g), sulphur (60g) and zinc oxide (60g). The milled rubber was
taken in a vertical chumer and to this methylethylketone (4 Its) and methyl isobutyl ketone (2.3 Its) were added and stirred at 60 rpm for 8h. At the end of this period, the nitrile rubber with other ingredients dissolved in the solvent mixture and to which separately dissolved phenolic resin of about 23.2%w/v in methyl ethylketone was added. The uniform nitrile rubber adhesive of density of 0.85g/ml, solids (%) 20 and has viscosity as determined by Ford Cup 4 is 100 sec. Wet laminates and also heat reactivated laminates were prepared using tin plate and asbestos sheets. These were evaluated for their bond strength and also fluid resistance and the results are shown in the following tables:
ADHESIVE BOND TESTS
(Table Removed)FLUID RESISTANCE TESTS

(Table Removed)It is observed that a cure schedule of 30 min at 180°C gives bond exhibiting resistance towards methylethylketone and the antifreeze solutions.
EXAMPLE - 2
Nitrile rubber medium - high acrylonitrile rubber having mooney viscosity 50 + 10 and having acrylonitrile 31 - 35%(1kg) was milled in a twin roll mill along with sulphur (1.6g), zinc oxide (48g). The sheet thus obtained was cut into small strips and added to vertical churner containing methyl isobutylketone (2.5lts) and methylethylketone (2.5lts). After a period of 6h., the rubber solution was homogenous. A novolac phenolic resin compounded with hexamine to an extent of 10%(920g} was dissolved in methylethylketone (2.5 Its), separately and this was added to the rubber solution and stirred for an extra 1h. To this an antioxident butylhydroxy anisole 0.1% on the total weight of the resin was added and then stored in metal containers. The uniform nitrile rubber adhesive had density of 0.9g/ml, solids 25% and viscosity of 100 sec. as determined by Ford Cup 4.
The wet laminated and heat reactivated laminates were prepared using tin and asbestos sheets and were tested for their bond strength and fluid resistance tests as described earlier. The results are given in the following tables:
ADHESIVE BOND TESTS
(Table Removed)FLUID RESISTANCE TESTS

(Table Removed)It is observed that at cure schedule of 30min at 180°C gave excellent resistane in methylethylketone and the antifreeze solutions to an extent of 100% and the bond strength also to the extent of 90% on the wet laminated sheets.
EXAMPLE - 3
Nitrile rubber medium - high acrylonitrile rubber having mooney viscosity 45 and having a specific gravity of 0.98 Ikgywas milled in a twin roll mill and to this methyl isobutylketone (2 Its) and methylethylketone (2.08 Its) were added and stirred at 35°C over a period of 6h. At this time a clear nitrile rubber solution was obtained. To this novolac phenolic resin compounded with hexamine to an extent of 15% (660g.' 'was separately dissolved in methylethylketone (2.08 Its.)
and this was added to the rubber solution. To this an antioxident butylhydroxy anisole 0.2% on the total weight of the resins was added and stored. This adhesive had density of 0.90g/ml, solids content of 25% and viscosity of 130 sec. as determined by Ford Cup 4. This adhesive was evaluated for the bond strength and fluid resistance of the wet and heat reactivated laminates. The results are given in the following tables:
ADHESIVE BOND TESTS

(Table Removed)FLUID RESISTANCE TESTS

(Table Removed)EXAMPLE - 4
Nitrile rubber medium - high acrylonitrile rubber having mooney viscosity - 55 (1kg) was milled in a twin roll mill and was compounded with sulphur (10.8g) for 1 hour. This milled rubber was cut into small peices and dissolved in
methyl isobutylketone (2.25 Its) and methylethylketone (2.25 Its.) in a vertical churner and stirred at 60 rpm over a period of 6h. A novolac phenolic having 13% hexamine; (794 g),was separately dissolved methylethylketone (2.25 Its.) and this was added to the rubber solution and stirred for 1 h. To this an antioxident butylhydroxy toulene 0.2% on the total weight of the solids was added and stored. This adhesive had density of 0.90g/ml, solids content 25% and viscosity of 125 sec. as determined by Ford Cup 4. This adhesive was evaluated for the bond strength and fluid resistance of the wet and heat reactivated laminates of tin and asbestos. The results are given in the following tables:
ADHESIVE BOND TESTS

(Table Removed)FLUID RESISTANCE TESTS

(Table Removed)EXAMPLE - 5
The adhesive as prepared in example-4 was cured at different schedules
ranging from 200 - 250°C for 8 - 20min. The wet laminated sheets of tin and asbestos were tested for the fluid resistance in methylethylketone. The results are given in the table:
CURE SCHEDULE OF TIN-ASBESTOS COMPOSITES
Application of Cure Schedule Time of Soak Results
adhesive on °C at Min inMEK(h)

(Table Removed)The main advantages of this process are :
1) The utilization of mixture of solvents i.e., methylethylketone and methyl
isobutyl ketone to dessolve the nitrite rubber so as to get low viscosity
product with high solid content.
2) The utilization of novolac phenolic resin having free hexamine content of 6-
15% helps in bonding the asbestos sheets with aluminium sheets and also

We claim:
1. A process for the preparation of Nitrile rubber based adhesive for automotive gasket which comprises:
i) milling of nitrile robber having 15-35% acrylonitrile content as herein described with additive of softening agent ranging 0-1% , vulcanizing agent as sulphur ranging 0-3% and lubricating metal oxide ranging 0-3% such as herein described in a twin roll shear mill;
ii) dissolving the milled mixture of rubber and ingredients obtained in step i) in a mixture of solvent of methyl ethyl ketone and methyl isobutyl ketone and the ratio of the said solvents being in the range of 1:1 to 2:1 and the ratio of said rubber mixture and that of the solvent being kept ranging 1:4 to 1:6.5 , stirring the said mixture in a vertical churner /reactor at 60-70 rpm , temperature ranging 30-35°C for a period ranging 6-8 hours to get a homogenous solution ;
iii) adding a solution of about 23%w/v of phenolic resin of novolac type containing hexamine ranging 6-15% in methyl ethyl ketone to the homogenous mixture as obtained in step ii) and further stirring the mixture solution for a period of about 1 hour;
iv) adding antioxidant such as herein described to the homogenous mixture as obtained in step iii) and the concentration of antioxidant

addition being in the range of o.l to 0.2 of the weight of total phenolic resin added in step iii) to obtain the nitrile rubber based adhesive ; characterized in that the adhesive contains 52-60% nitrile rubber and 40-47% of phenolic resin.
5. A process for the preparation of Nitrile rubber based adhesive for automotive gasket substantially as herein described with reference to the examples.

Documents:

543-del-1999-abstract.pdf

543-del-1999-claims.pdf

543-del-1999-correspondence-others.pdf

543-del-1999-correspondence-po.pdf

543-del-1999-description (complete).pdf

543-del-1999-form-1.pdf

543-del-1999-form-19.pdf

543-del-1999-form-2.pdf

« Previous Patent

Next Patent »

Patent Number

216095

Indian Patent Application Number

543/DEL/1999

PG Journal Number

12/2008

Publication Date

21-Mar-2008

Grant Date

07-Mar-2008

Date of Filing

08-Apr-1999

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	NORI KRISHNAMURTI	INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD-500007, ANDHRA PRADESH, INDIA.

PCT International Classification Number

F16J 15/12

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA