Title of Invention

A PROCESS FOR PREPARING RUBBER ARTICLES OF LOW FRICTION COEFFICIENT

Abstract A process for the preparation of rubber articles such as gloves having a low co-efficient friction comprising in the step of functionalization of the rubber surface in a mixture of formic acid and hydrogen peroxide in the molar ratio of 1:0.8 to 1:3 at a temperature in the range of 20 to 80degeree c to obtain a modified surface then subjecting the modified surface to the step of grafting with a water soluble terpolymer as herein described.
Full Text This invention relates to a process for preparing rubber articles of low friction coefficient.
Rubber products such as catheters and endotracheal tubes offer undue friction during inserticm leading to mechanical injury to the mucous membranes, Mhich could cause discomfort to the patients. Further, due to surface irregularity bacterial adhesion can take place which ultimately leads to infection.
An object of this invention is to propose a process for preparing rubber articles having reduced coefficient of friction.
Further objects and advantages of this invention will be more apparent from the ensuing description.
According to this invention there is provided a process for the preparation of rubber articles such as gloves having a low co-efficient friction comprising in the step of functionalization of the rubber surface in a mixture of formic acid and hydrogen peroxide in the molar ratio of li0.8to ls3 at a temperature in the range of 20 to 80 C to obtain a modified surface and then subjecting the modified surface to the step of grafting with a water soluble terpolymer as herein described.

Rubber articles such as urinary catheters are mainly made up of natural rubber latex. Benerally the surface of these products are available with a coating of silicone oil which is not very effective in reducing the friction of these surfaces. Further, such coatings cannot maintain a high degree of slipperiness, due to
the leaching or dispersion into the surrounding body
Hence a fluids. J-hue-y->4rhe low friction surface by covalently
bonding a water soluble polymer on to the rubber
provides a long durability.
In accordance with the process of the present invention with the surface of the natural rubber is functionalized using a simple process and then grafted with a water soluble terpolymer.
The step functionalisation of the rubber surface is carried out by suspending the rubber surface in a mixture of formic acid and hydrogen peroxide at temperatures ranging from 20*^ to 80*^, and preferably at a temperature of 30° to 60t. The mixture contains formic acid and hydrogen peroxide in the molar ratio of l!0.8 to 1:3.

The modified surface is grafted with a terpolymer consisting of N-vinyl-2-pyrrolidone, vinyl acetate and acrylic acid (or methacrylic acid), using tertiary amine as catalyst.
The catalysts found to be effective in the grafting reactions are aromatic tertiary amines such as N,N-dimethyl-p-toluidine or N,N-diethanDl-p-toluidine or 2-(4-dimethyl aminophenyl) ethanol and benzyl triethyl ammonium chloride and/or tetrabutyl tin. The solvents used for reactions are dimethyl sulphoxide or N,N-dimethyl formamide or water. The broad ranges of catalyst concentrations are 0.5% to 15%.
The composition of the polymer can be N-vinyl-2-pyrrolidone (40-95%), vinyl acetate (0.15%) and acrylic acid (or methacrylic acid) (5—45%).
The scheme of reaction can be represented as follows:—



The steps of grafting comprises in dissolving the aforesaid catalyst in a solvent medium. A terpolymer is dissolved in the above solvent(s) such that the coating solution has a concentration of 0.5% to 105i. The functionalised rubber substrate is soaked into the catalysed terpolymer solution. The grafting reaction is carried out in an oven either suspending the substrate in the medium itself or in air. The temperatures employed for the grafting reactions are 4CPc to lOCPc. When the reaction is complete, the grafted rubber is grafted in distilled water and dry in vacuum.
The grafted surface is tested for coefficient of friction in water. The friction coefficient could be adjusted from 0.2 to 0.6 by adjusting the various process parameters such as monomer composition in the polymer, extent of surface epoxidation, catalyst concentration, etc. The measured coefficient of friction for the unmodified sample under the same test conditions was 0.9.
The process can be extended to any polymer surface having unsaturation or polymers having epoxy groups. The application can be biomedical (catheters, gloves, pacing leads etc.) and also in general industrial applications such as rubber lined conveyors etc.

EXAMPLE-1
A water-soluble ter-polymer was synthesised by conventional methods, using a peroxide catalyst from the following monomerss N—vinyl pyrrolidone. Vinyl acetate and Acrylic acid. The approxi¬mate ratio of the above monomers that gives a water-soluble polymer is:85:10:5.
Prepare a freshly prepared mixture of 1:1 mole solution of formic acid and hydrogen peroxide. Suspend a rubber latex
substrate in a 20% dilute solution of the above mixture for about
o 5 hours at 50 C. Wash and remove the residual reagents after the
reaction.
The surface epoxidised rubber was used for grafting as soon as the epoxidisation was complete.
The water-soluble polymer synthesized was dissolved in Dimethyl sulphoxide. About 1% N, N—dimethyl-p-toluidine was added into this solution and the solution temperature was maintained at 70 C. The expoxidised rubber was suspended in this solution for grafting and the residual reagents, were washed off from the grafted rubber when the grafting reaction was complete.


We claim;
1. A process for the preparation of rubber articles such as gloves having
a low co-efficient friction comprising in the step of functionalization
of the rubber surface in a mixture of formic acid and hydrogen
peroxide in the molar ratio of 1:0.8 to 1:3 at a temperature in the range
of 20 to 800C to obtain a modified surface then subjecting the
modified surface to the step of grafting with a water solubte
terpolymer as herein described.
2. A process as claimed in claim 1 wherein said step of functionalization
is carried out preferably at a temperature of 30" to 60" C.
3. A process as claimed in claim 1 wherein said step of grafting
comprises in dissolving a catalyst as herein described m a solvent
medium.
4. A process as claimed in claim I wherein said catalyst is present in the
amount of 0.5 to 15.
5. A process as claimed in claim 1 wherein said terpolymer has a
concentration of 0.5 to 10.
6. A process for the preparation of rubber articles substantially as herein
described and illustrated in the example.

Documents:

0281-mas-1997 abstract.pdf

0281-mas-1997 claims.pdf

0281-mas-1997 correspondence-others.pdf

0281-mas-1997 correspondence-po.pdf

0281-mas-1997 description (complete).pdf

0281-mas-1997 description (provisional).pdf

0281-mas-1997 form-1.pdf

0281-mas-1997 form-26.pdf

0281-mas-1997 form-4.pdf

0281-mas-1997 form-5.pdf

0281-mas-1997 form-6.pdf

0281-mas-1997 petition.pdf

281-mas-1997 abstract granted.pdf

281-mas-1997 claims granted.pdf

281-mas-1997 description (complete) granted.pdf


Patent Number 198257
Indian Patent Application Number 281/MAS/1997
PG Journal Number 20/2006
Publication Date 19-May-2006
Grant Date 13-Jan-2006
Date of Filing 12-Feb-1997
Name of Patentee M/S. SREE CHITRA TIRUNAL INSTITUTE FOR MEDICAL SCIENCES & TECHNOLOGY
Applicant Address BIOMEDICAL TECHNOLOGY WING, SATELMOND PALACE, TRIVANDRUM 695 012
Inventors:
# Inventor's Name Inventor's Address
1 ROY JOSEPH INDIAN INSTITUTE OF BIOMEDICAL TECHNOLOGY WING, SREE CHITRA TIRUNAL INSTITUTE FOR MEDICAL SCIENCES & TECHNOLOGY, POOJAPURA, TRIVANDRUM 695 012
2 PARAMESWARAN RAMESH INDIAN INSTITUTE OF BIOMEDICAL TECHNOLOGY WING, SREE CHITRA TIRUNAL INSTITUTE FOR MEDICAL SCIENCES & TECHNOLOGY, POOJAPURA, TRIVANDRUM 695 012
3 RAJAGOPALAN SIVAKUMAR INDIAN INSTITUTE OF BIOMEDICAL TECHNOLOGY WING, SREE CHITRA TIRUNAL INSTITUTE FOR MEDICAL SCIENCES & TECHNOLOGY, POOJAPURA, TRIVANDRUM 695 012
PCT International Classification Number C 08 J 7/14
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA