|Title of Invention||
"BUILT-IN STABILIZED VINYL PYRIDINE LATEX, PROCESS FOR PREPARING THE SAME AND USE THEREOF"
|Abstract||Disclosed herein is a built-in stabilized vinyl pyridine latex suitable for use in tyre cord dipping, wherein the latex comprises a polymerisable emulsifier as co-monomer, polymerized with a mixture of monomers comprised of vinyl pyridine, styrene and butadiene along with rosin acid soap as base emulsifier. The process for preparing the same and use thereof is also disclosed in the present invention.|
|Full Text||Field of the Invention
This invention, in general, relates to the field of vinyl pyridine latex. More specifically, but without restriction to the preferred embodiments herein after described in accordance with the best mode of practice, the present invention provides a built-in stabilized vinyl pyridine latex employing a suitable polymerizable emulsifier as co-monomer, process for preparing the same and use thereof
Background of the Invention
Vinyl pyridine latex is extensively used in tyre cord dipping process. Prior to use, the latex is mixed with either a resin forming agent or a combination of resin forming reagents such as resorcinol, resorcinol formaldehyde novolak, resorcinol formaldehyde resole, etc. This mixture is referred to as an RFL tyre cord dipping solution (referred to hereinafter as "RFL dip").
US Patent 3,960,796 discloses about polyester fabric reinforcing elements which can readily be bonded or adhered to curable rubbery compounds by dipping the elements in a booth consisting essentially of an aqueous alkaline dispersion of a minor amoimt by weight of a mixture of a major amount by weight of a rubbery vinyl pyridine copolymer and a minor amount by weight of a heat reactable 2,6-bis (2,4-dihydroxy phenylmethyl)-4-chlorophenol composition, drying the same, and combining said dipped and dried element with a vulcanizable rubber compound and vulcanizing the same.
US Patent 4,040,999 reveals about the phenol formaldehyde resole preparation and use in a cord dip without the necessity of isolation and purification of the resole. The products of the process are not adversely affected by the presence of formaldehyde, salts, phenols and other by-products.
US Patent 4,134,869 reveals about the use of the resorcinol-formaldehyde novolak, normally used as a compounding ingredient for tire cord dips to stabilize the vinyl pyridine latex. Vinyl pyridine latexes containing resorcinol-formaldehyde novolaks
compare quite favorably in shear stability with vinyl pyridine latexes stabiHzed with soap.
US Patent 4,248,938 reveals about processes for preparing a polyester fiber composite material having an excellent bonding property to rubber, a proper softness and a high resistance to fatigue, comprises the steps of first impregnating a polyester fiber material much as fabric, cord or thread, with a first treating liquid containing (A) a polyepoxide compound having two or more epoxy groups per molecule of the compound, (B) a blocked polyisocyanate compound, for example, an addition product of a polyisocyanate compound with a phenol, tertiary alcohol or aromatic secondary amine compound and (C) a rubber latex such as vinyl pyridine-styrene-butadiene terpolymer latex; first drying and heat treating the first impregnated material at a temperature of, preferably, 180°C or higher but lower the melting point of the polyester fiber material; second impregnating the first impregnated and heat-treated material with a second treating liquid containing a resorcinol formaldehyde reaction product, a rubber latex and optionally an ethylene-urea compound.
A cord dip composition comprising a styrene-butadiene-vinyl pyridine terpolymer latex and a mixture of an aldehyde condensate and a glyoxal reaction product are disclosed in US patent 4,263,190.
US Patents 5,034,462 and 5,171,637 reveal the preparation of a terpolymer of styrene, butadiene and amino substituted alkyl acrylate which is used as an adhesion promoter between organic substrate and unsaturated polymer. The composition consists of styrene (0-30%), butadiene (55-97%) and the amine substituted alkyl acrylate (1-15%) based on the total wt. of the monomers present in adhesion promoter. The amine substitutions are alkyl / aryl or substituted aromatics. The latex is produced by core-shell type emulsion polymerization wherein the core consists of styrene & butadiene and shell consists of styrene, butadiene and acrylate.
US Patent 5,863,987 relates an adhesive composition with improved adhesion between polyester tyre cord and rubber by treating the cord fabric in a dip consisting of vinyl
pyridine latex having two kinds of monomer composition and a thermosetting resin comprised of resole and novolak type condensate of resorcinol and formaldehyde.
US Patent 5,922,797 reveals about the preparation of a low cost modified vinyl pyridine latex composition for RFL dip. The latex consists of a polymer made fi-om a conjugated diene monomer, vinyl aromatic monomer, 2-vinyl pyridine and a vinyl aldehyde monomer. This invention also discloses about an adhesive composition consisting of Resorcinol, formaldehyde and modified vinyl pyridine latex. This invention also relates to the process of adhering synthetic textile fibers to rubber in four steps i.e., immersing fibers in aqueous dispersion of the above adhesive composition, drying the dipped fabrics, placing the dipped fibers with rubber and curing the rubber fiber composites. It also discloses the composite composition, which consists of modified vinyl pyridine latex.
Vinyl pyridine latex prepared by emulsion polymerization generally requires a post modification step, where fatty acid soaps have been used as stabilizers. There are some common drawbacks of using these fatty acid soap stabilizers. The excess soaps used to prevent coagulation have caused excessive foaming during dipping operation when high mechanical force is exerted to the latex solution. This foaming causes non-uniformity both in the amount of dip applied to a cord and in the coating on the dipped cord surface. Also presence of carboxylic acid groups in the fatty acids have resulted in widowing effect during long term storage which in turn resulted in poor mechanical stability, chemical stability and high foaming. There is also a possibility of migration of these soaps to the interface of tyre. Deposition of soap at one stage may also cause separation of the rubber components at that particular interface causing tire failure.
Therefore there is a need to improve vinyl pyridine latex to eliminate the limitations in the prior art for the application in tyre cord dipping. Accordingly, the present invention discloses the preparation and production of an improved vinyl pyridine latex.
Summary of the Invention
It is a principal object of the present invention to provide a vinyl pyridine latex with built-in stabilization for dipping of synthetic cords during tyre manufacturing.
Further object of the present invention is to prevent the excessive foaming and the resulting problems caused by the presence of fatty acid soaps in the latex during dipping. The built-in stabilized vinyl pyridine latex of the present invention exhibits better mechanical stability.
Furthermore, said vinyl pyridine latex also provides superior chemical stability, hard water stability and low foaming during high mechanical shearing, with an improved freeze-thaw stabiUty as compared to normal vinyl pyridine latex. This and other objectives of the present invention are further attained and supported by the embodiments described herein.
In accordance with one preferred embodiment of the present invention, there is provided a built-in stabiUzed vinyl pyridine latex for utiUzation in RFL dip processes, wherein said latex comprises of mixture of monomers having 4-9 carbon atoms, a polymerizable emulsifier, an initiator, a chain modifier and a base emulsifier.
In accordance with another preferred embodiment of the present invention, there is provided a built-in stabilized vinyl pyridine latex for utilizing in RFL dip, wherein the latex comprises a polymerizable emulsifier as co-monomer, polymerized with vinyl pyridine, styrene and butadiene along with rosin acid soap as base emulsifier, to avoid the use of fatty acid soap during post modification step and helps to prevent the excessive foaming and the resulting problems caused by the presence of soaps in the latices and exhibits better mechanical stabiUty, chemical stability, hard water stability and low foaming during high mechanical shearing with an improved fi-eeze thaw stability.
In accordance with another preferred embodiment of the present invention, there is provided a built-in stabilized vinyl pyridine latex for utilization in RFL dips, wherein
the said vinyl pyridine latex is manufactured with rosin acid soap as the base emulsifier with a minimal percentage of polymerizable emulsifier as fourth monomer along with monomers vinyl pyridine, styrene and butadiene, wherein the percentage range of the polymerizable emulsifier is about 0.01% to 1%.
In accordance with another embodiment of the present invention, there is provided a stable vinyl pyridine latex for utilization in RFL dips, wherein said polymerizable emulsifier is selected from anionic emulsifier preferably sulphonate or sulphosuccinate group, more preferably vinyl or allyl sulphonate/sulphosuccinate.
In accordance with another preferred embodiment of the present invention there is provided a built-in stabilized vinyl pyridine latex, wherein the latex comprises 5-20% of vinyl pyridine, 5-20% of styrene and 60-90% of butadiene and is polymerized with rosin acid soap as base emulsifiers and 0.01-1% of polymerizable emulsifier, preferably vinyl or allyl sulphonate/sulphosuccinate and tertiary dodecyl mercaptan as a chain modifier and a chain initiator.
In accordance with another preferred embodiment of the present invention there is provided a stabilized vinyl pyridine latex, wherein the monomer system comprises of styrene, 1,3-butadiene and 2-vinyl pyridine as main monomers and polymeric emulsifier having sulphonate or sulphosuccinate group as the co-monomer, wherein the ratio of styrene, 1,3-butadiene and 2-vinyl pyridine varies from 5:65:30 to 20:75:5.
In accordance with yet another embodiment of the present invention, there is provided a process for preparing the built-in stabihzed vinylpyridine latex, wherein the process comprises emulsion polymerization process.
In further embodiment of the present invention there is provided a use of said vinyl pyridine latex preferably in dipping of synthetic cords during tyre manufacturing.
Detailed Description of the Invention
The present invention provides built-in stabilized vinyl pyridine latex mainly used in dipping of synthetic cords during tyre manufacturing. It also describes the process for preparation of the vinyl pyridine latex through emulsion polymerization employing polymerizable emulsifier as a co-monomer along with monomers.
The vinyl pyridine latex disclosed herein comprises styrene or substituted styrene, 1,3-butadiene, and 2-vinyl pyridine as monomers, rosin acid soap as base emulsifier with polymeric emulsifier as the co-monomer and tertiary dodecyl mercaptan as a chain modifier along with other ingredients. The initiator used for the reaction is a thermally decomposable initiator selected from sodium, potassium or ammonium peroxodisulphate. The base emulsifier used in the reaction is sodium or potassium soap of rosin acid and is used upto 7 parts per hundred parts of monomer, herein after referred as phm. The polymeric emulsifier used in the reaction is sodium or potassium soap of vinyl or allyl sulphonate / sulphosuccinate upto a level of 1.0%. The chain modifier is selected from primary, secondary or tertiary dodecyl mercaptan and is used upto 2 phm level. The pH of latices and solutions and emulsifiers should be similar and compatible to avoid coagulation and mixing of the latices.
The present invention avoided the necessity for adding fatty acid soaps in latices during post modification, which are basically anti-adhesive in nature. Also, the alkaline metal ion of the fatty acid soap reduces the adhesion of cord such as polyester with rubber that can cause separation of the tire components at the interfaces. The present invention also helps to prevent the excessive foaming and the resulting problems caused by the presence of soaps in the latices and exhibits better mechanical stability, chemical stability, hard water stability and low foaming during high mechanical shearing with an improved freeze thaw stability.
Disclosed styrene or substituted styrene is selected from styrene, a-methyl styrene, 2-methyl styrene, 3-methyl styrene, 4-methyl styrene, 2,4-diisopropyl styrene, 2,4-dimethyl styrene, 4-t-butylstyrene, hydroxymethyl styrene and the like. Preferably styrene is used in the invention.
Said vinyl pyridine is selected from 2-vinyl pyridine, 3-vinyl pyridine, 4-vinyl pyridine, 2-methyl 5-vinyl pyridine, 5-ethyl 2-vinyl pyridine and the like mentioned as a pyridine ring containing vinyl compovmd. One or two of the above may be used but 2-vinyl pyridine is most preferably used.
Rosin acid soap is used herein in the range of about 5% by wt. in initial charge composition. Of the rosin acids, 90% are isomeric with abietic acid and other 10% are mixture of dehydro abietic acid and dihydro abietic acid.
The polymerization can be initiated using free radical generators, UV light or radiation. To ensure a satisfactory polymerization rate, uniformity and controllable polymerization, free radical initiators are generally used. The free radical initiators which are commonly used include various peroxy compounds such as potassium persulphate, ammonium persulphate, benzoyl peroxide, hydrogen peroxide, di butyl t-peroxide, dicumyl peroxide, lauryl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, etc.
The vinyl pyridine latex disclosed herein is prepared by conventional emulsion polymerization process. Initially a solution of dehydro abietic rosin acid in sodium or potassium hydroxide solution is prepared and aspirated to the pressure reactor fitted with a variable drive agitator. Desired dose of dodecyl mercaptan followed by a thermally decomposable initiator is fed into the reactor.
The monomer system comprises of styrene, 1,3-butadiene and 2-vinyl pyridine as main monomers and polymeric emulsifier having sulphonate or sulphosuccinate group used as the fourth monomer. The ratio of styrene, 1,3-butadiene and 2-vinyl pyridine varies from 5:65:30 to 20:75:5. Polymeric emulsifier generally used is 0.01-1.0%. After all the monomers and initiator are aspirated into the reactor, the temperature is increased to 45°C and controlled within the range of 45-50°C.
After completion of feeding, the reactants are held at 45-70°C for desired duration and progress of reaction is monitored by measuring the non-volatile matter on a hourly basis. After desired degree of conversion is attained, a conventional shortstopping agent, e.g. hydroquinone is added to the polymerization medium to terminate the reaction. The batch cycle time usually takes 25-35 hours. After the polymerization is over, the latex is cooled, filtered and collected and tested to check the properties.
The emulsion polymerization utilized to synthesize the latices of this invention can be carried out over a broad temperature range from 0-1000C. However it is normally preferred to carry out the process in the temperature range of 5-800C and the most preferred temperature range of the polymerization is 50-70°C.
The mechanical stability of latex was measured by following ASTM D-1417 cl.l2, in which a specified quantity of sample is rotated in a Klaxon Mechanical stability tester at a speed of 14000 + 200 rpm for 10 minutes. Shear generated coagulum was measured after filtration in a 100 mesh stainless steel screen and drying at 105°C for 3 hrs.
Mechanical Stability, % = (A-B) X 100 / M
A = Screen plus coagulum weight
B = Tared screen weight
M = Latex sample weight
The viscosity was measured using a brookfield viscometer Model LVT at 25°C by following ASTM D-1417 cl.8. Viscosity was measured with Spindle 1 at a speed of 60 rpm.
The latex foam rise was measured using a klaxon mechanical stability tester with specified quantity of sample taken in a graduated test cup as per ASTM D1417 cl. 8 and rotated at a speed of 14000 ± 200 rpm for 10 minutes. The foam level was
measured in cms after 6 minutes run. The reading was taken after 6-7 minutes of testing.
Latex surface tension was measured with a Fischer scientific surface tensiometer by following ASTM D-1417 cl.7. The test is a standard test and involves dipping a platinum-iridium ring (Du nouy ring) into the latex. During pulling out the ring from the emulsion, a point is reached when the contact of the ring and surface of the emulsion breaks. The scale reading at that point indicates the surface tension of the emulsion.
Latex chemical stability was studied with resorcinol and formaldehyde solution Clear solution of 37 gms of resorcinol was prepared in 79 gms of distilled water. 19.50 ml of formaldehyde (37 % solution) was added and mixed properly. The mixture was matured for one hour at 25°C. Then the 216 gms of latex was added to a dry erlenmeyer flask. After six hours coagulum was measured after filtration in a 180 mesh stainless steel screen and drying at 105°C for 3 hrs.
The test for bactericidal effect was performed by adding a bacterial culture derived from spoiled vinyl pyridine latex. One ml of inoculation (3 million coimts) was added to 500 ml of latex. After one day a second one ml inoculation was added to the 500 ml latex sample and the counts repeated. After another day i.e. third day one ml inoculation was added to the 500 ml latex sample and the counts repeated. The samples were aged for 30 days at 25°C with bacterial agar and potato dextrose as the nutrient and then plated to get a coimts/ml.
Hard water compatibiHty was studied by using hard water of 1000-1200 micro mho conductivity in post incorporation and final solid and pH adjustments. After modification, the latex was stabilized for 24 hrs. Then mechanical stability of the aged sample was measured using a Klaxon mechanical stability tester. Shear generated coagulum was measured after filtration in a 100 mesh stainless steel screen and drying at 105°C for 3 hrs. During washings of coagulum also hard water of 1000 micro-mho was used.
Freeze thaw stability of latex was studied for three cycles of freezing and thawing of latex with an interval of 12 hrs at -10 to 30°C respectively. After three cycles mechanical stability of the latex was measured by the above-mentioned method. Shear generated coagulum was measured after filtration in a 100 mesh stainless steel screen and drying at 105°C for 3 hrs.
A series of formulations were prepared using styrene, butadiene and 2-vinyl pyridine as main monomers by emulsion polymerization process wherein rosin acid soap was used as base emulsifier and vinyl or allyl sulphonate/sulphosuccinate was used as polymerisable emulsifier.
The recipe of 9 sets of experiments has been tabulated in Table-1, wherein the ingredients are measured in parts by weight. Set 1 experiments was performed with the standard recipes of vinyl pyridine latex manufactured with normal quantity of fatty acids in the post modification step. Set 2 experiments was performed with lower quantity of fatty acids in the post modification step. In Set 3 no post incorporation was done. Set 4-8 had some post incorporation with different dosages of polymerizable emulsifiers. Set 9 was done without any fatty acid post incorporation.
All the above set of experiments were performed and latices were prepared. All formulations were adjusted to 41% TSC with deionised water and pH was adjusted up to 10.8 with KOH. After the incorporation of hydroxylated tallow fatty acid (HTFA), samples were allowed to stand for 24 hours. The experiments of set 3 and set 9 were performed after 24 hours of preparation without any post incorporation.
The test results are disclosed in Table-2. It is evident from the test results that as the quantity of fatty acid soaps are reduced from 0.4 to 0.0 phm from set 1-3, mechanical stability becomes inferior. Set 3 gives the expected poor results. A part of fatty acid soap is replaced by polymerizable emulsifiers in sets 4-9. In experiment 4-9, polymerizable emulsifier was increased by keeping the quantity of fatty acid soaps constant, which results in negligible impact on mechanical stability. Foam rise level
decreases from 10 to 7 cm with post stabilization quantity in set 1-3. With partial addition of fatty acid soaps in case of set 4-8, the foam rise level increases. In set 9, when the quantity of fatty acid soap is nil with an optimum quantity of polymerizable emulsifier, foam rise level is again low. Chemical stability also follows the same trend as that of mechanical stabiluity. Surface tension, particle size and brookfield viscosity however follows a different trend. Maximum surface tension, minimum particle size and highest viscosity was observed in case of set 3.
In the microbial study after 2nd inoculation and 6 days study in set 3 and set 7-9, very scant growth of microbes is shown in the latex. Minimizing the natural products like fatty acid soaps also reduces the chances of microbial growth in the latex and hence the latex has improved lifecycle. Due to incorporation of a synthetic originated sulphonate or sulphosuccinate type of polymerizable anionic emulsifier, the hard water compatibility increases. Incorporation of the polymerizable emulsifier increases the particle size evidently which suffices that the sulphonate/sulphosuccinate added to the system are polymer bound which in turn exhibits the better properties to the latex in terms of mechanical stability, chemical and freeze thaw stability. Post incorporation of fatty acid soap are very prone to desaponification of soaps and return back to the original acids which is not in case of sulphonates/sulphosuccinates due to its better hydrophilicity.
Thus a minimum quantity of polymerizable emulsifier produces a latex having improved shear strength, microbial properties, chemical and freeze thaw stability in addition to low foaming tendency.
Nil = 10*0, Very Scant =10*1, Scant - 10*2, Light = 10*4, Moderate = 10*5, Heavy =
10*6, Dense > 10*6
While this invention has been described in detail with reference to certain preferred embodiments, it should be appreciated that the present invention is not limited to those precise embodiments. Rather, in view of the present disclosure, which describes the current best mode for practicing the invention, many modifications and variations would present themselves to those skilled in the art without departing from the scope and spirit of this invention.
1. A built-in stabilized vinyl pyridine latex, wherein said latex comprises a polymerizable emulsifier co-polymerized with the mixture of monomers having 4-9 carbon atoms, a base emulsifier, a chain modifier and an initiator, wherein, said vinyl pyridine latex is characterized by better mechanical stability, chemical stability, hard water stability and the low foaming during high mechanical shearing with improved freeze thaw stability.
2. The latex according to claim 1, wherein said polymerizable emulsifier is selected from anionic emulsifiers.
3. The latex according to claim 2, wherein said anionic polymerizable emulsifier is selected from a sulfonate or a sulfosuccinate group.
4. The latex according to claim 3, wherein said polymerizable emulsifier is selected from a group consisting of an alkali salt of vinyl sulfonate, vinyl sulfosuccinate, allyl sulfonate or allyl sulfosuccinate.
5. The latex according to claim 1, wherein the emulsifier is used in the range of 0.001-l.0 phm.
6. The latex according to claim 1, wherein the mixture of monomers comprises a straight chain or a branched chain ahphatic or aromatic compound with or without hetero atom.
7. The latex according to claim 1, wherein the mixture of monomers comprises preferably vinyl benzene derivative, 1,3-butadiene and 2-vinyl pyridine.
8. The latex according to claim 7, wherein the ratio of vinyl benzene derivative, 1,3-butadiene and 2-vinyl pyridine varies from 2:68:30 to 25:70:5.
9. The latex according to claim 7, wherein said vinyl benzene derivative is selected from the group consisting of styrene, alpha methyl styrene, para methyl styrene, vinyl toluene or a combination thereof
10. The latex according to claim 1, wherein said initiator is selected from sodium, potassium or ammonium peroxodisulphate.
11. The latex according to claim 1, wherein said chain modifier is selected from primary, secondary or tertiary dodecyl marcaptan.
12. The latex according to claim 11, wherein said dodecyl mercaptan is used in the range of 0.5 to 3.0 phm.
13. The latex according to claim 1, wherein the base emulsifier is a rosin acid soap.
14. The latex according to 13, wherein said rosin acid soap is used in the range of 0.1 to 7 phm.
15. A built-in stabilized vinyl pyridine latex as substantially herein described with reference to the description and examples.
|Indian Patent Application Number||1913/DEL/2004|
|PG Journal Number||14/2014|
|Date of Filing||04-Oct-2004|
|Name of Patentee||JUBILANT ORGANOSYS LIMITED|
|Applicant Address||PLOT 1A, SECTOR 16A, NOIDA-201 301, U.P., INDIA.|
|PCT International Classification Number||C08L 39/00|
|PCT International Application Number||N/A|
|PCT International Filing date|