Title of Invention

'A PROCESS FOR THE PREPARATION OF AN IMPROVED POLYURETHANE BASED SEALANT'

Abstract This invention relates to a process for preparation of polyurethane based sealant composition. According to the process synthesis of pre-polymer by treating hydroxylterminated polybutadiene (HTPB) with toluene di-isocyanate. Synthesis of polyester polyol by reaction of trimethylol with propylene in the presence of a catalyst. Hardener is prepared by mixing amines and polyol and charging the mixture with a filler. Sealant composition and its curing is prepared.
Full Text FIELD OF INVENTION
The present invention relates to a process for preparation of an improved polyurethane based sealant.
PRIOR ART
Sealants are flowable materials, which set after application and are highly elastic in nature. These are applied for joining surfaces like rubber to rubber, rubber to metal, metal to metal articles. The sealants are capable of undergoing deformation under any dynamic condition, and recovering quickly to its original shape once the dynamic condition is removed. Commonly used sealants are based on silicone resin, polysulfides, polyurethane, butyl rubber etc.
Polyurethane-based sealants are a class of materials whose properties can be tailor made by varying the constituent components to suit a particular application. Basically, it comprises of polyol, isocyanate and amine. At times, fillers are used to further modify the properties of sealant as per specific need. Polyol provides the elasticity whereas amine provides the strength characteristics to the sealant. A judicious selection of polyol, amine and isocyanate along with necessary fillers is required in order that the sealant composition may have the specific properties. However, the sealant compositions, known in the art, suffer from several disadvantages. One such disadvantage is that such sealant compositions do not have very high adhesion strength. Another disadvantage is that these sealant compositions do not have enough cohesive strength to bear high loads, and have low tensile strength.
Still another disadvantage is that such sealants have low elongation.
OBJECTS OF THE INVENTION
A primary object of the present invention is to provide a process for preparing a polyurethane-based sealant composition, which can be utilised for joining surfaces like rubber to rubber, rubber to metal, metal to metal having different shapes.
Another object of the present invention is to provide a process for preparing a sealant composition which has high adhesive strength.
Still another object of the present invention is to provide a process for preparing a sealant composition, which can bear high loads and does not break under its influence.
Yet another object of the present invention is to provide a process for preparing a sealant composition which is highly viscous, thereby permitting further structural buildup without significant delay.
Yet further object of the present invention is to provide a process for preparing a
sealant composition which is not brittle.
Yet another object of the present invention is to provide a process for preparing a sealant composition which has sufficient flexibility.
Still another object of the present invention is to provide a process for preparing a sealant composition, which has excellent weather resistance.
Yet further object of the present invention is to provide a process for preparing a sealant composition which has excellent resistance to marine environment thereby facilitating its use under marine environment.
Still another object of the present invention is to provide a process for preparing a sealant composition, which has minimal air entrapment.
Still further object of the present invention is to provide a process for preparing a sealant composition wherein suitable filler material may be added for obtaining improved sealing action.
DESCRIPTION OF THE PRESENT INVENTION
According to present invention there is provided a process for preparation of an improved polyurethane based sealant comprises and characterised by the steps of:-
a) synthesis of Pre-polymer carried out at a temperature of 40 to 80° C by
treating hydroxyl-terminated polybutadiene (HTPB) with toluene di-
isocyanate as herein described.
b) synthesis of polyether polyol by reaction of trimethylol with propylene
oxide in the presence of a catalyst such as NaoH, KoH, CsoH in
preferred quantity of 0.1 to 0.2 parts by weight.
c) preparation of hardener by mixing amines and polyol and charging the
mixture with a filler as herein described.
d) preparation of sealant by mixing preferably 1 equivalent of pre-polymer
and 0.8 to 1.2 equivalent hardner, followed by curing as herein
described.
The polyurethane-based sealant composition can be utilised for joining surfaces like rubber to metal, rubber to rubber, metal to metal having different shapes and configurations. The sealant composition has high adhesion strength along with sufficient flexibility and is capable of bearing high loads. The composition has excellent weather resistance including resistance to marine environment. It has minimal air entrapment and can be utilised for underwater applications. The composition comprises, basically, a prepolyrner and a hardener. The pre-polymer is toluene diisocyanate (TDI) capped polybutadiene diol and the hardener is a mixture of two aromatic diamines in a suitable polyol. The process for preparing the sealant composition
comprises the steps of synthesis of prepolymer, synthesis of polyether polyol, preparation of hardener and curing of sealant
composition.
( i ) Synthesis of the prepolymer:
Hydroxyl—terminated polybutadiene, HTPB (broad molecular
weight 500 to 5000 and preferred molecular weight 1000 to 3000) with known hydroxyl value (40 to 50) is treated with toluene
diisocyanate, TDI (ratio of HTPB: TDI=i:2) under continuous
stirring for about S-10 hours in a closed vessel. The temperature
o of the reaction could be from 25 to 150 C and preferably from 40-
o 80 C. The reaction is continued till the desired isocyanate value
is obtained. The product is stored in a sealed container to avoid exposure to air and moisture as it has tendency for gelling under
high humidity condition.
(ii) Synthesis of polyether polvol:
Polyether polyol is synthesised by reaction of trimethylol propane with propylene oxide in presence of a suitable catalyst
like NaOH, KOH, CsOH etc. For every 1 equivalent of trimethylol propane, 30 to 200 equivalent of propylene oxide (preferably 80
to 120) is utilised. Preferably, 0.1 to 0.2 parts (weight wise) of CsOH is used as a catalyst. The reaction is terminated after
attaining the desired hydroxyl value (27 to 33). The catalyst is removed by treating with water and finally the product is dried to
remove the moisture. The synthesised polyether polyol is stored in a sealed tin container or dark glass bottle.
(iii) Preparation of hardener :
The hardener, basically, is a mixture of an amine and a polyol. The amines used for making polyurethane can be aliphatic or aromatic diamine. However, for better pot life and inherent strength of the sealant, aromatic diamines like 4,4' diamino 3,3' dichloro diphenyl methane and 4,4' diamino 3,3' dichloro triphenyl methane are preferred. Diamine is mixed with polyol under continuous stirring and heating. The percentage of diamine can be varied from 5 to 60% but the preferred percentage is 25 to 40%. The temperature of mixing is in the range of 60 to 90°C. The hardener solution is charged with known quantity of filler such as carbon black, CaCO3 etc. The preferred percentage of carbon black and CaCO3 is 10-15. Among the various filler carbon black is preferred as it adds to the strength characteristics of the resultant sealant. The entire mass comprising of amine, polyol and filler is thoroughly mixed with in a triple roll mill to get a homogeneous product. This mixture is called hardener. The hardener is finally checked for amine content.
(iv) Curing of the sealant composition:
Finally, the sealant composition is prepared by mixing 1 equivalent of prepolymer and 0.8 to 1.2 equivalent of hardener, prepared in above manners. The viscous mass, thus mixed, is thoroughly mixed for 10 to 15 minutes. Afterwards, the mixture is poured onto a mould and the mass is spread with the help of a knife. The mould with mass is left for 24 hrs. at ambient conditions for curing and then, in an oven for post curing at 60° C for 8 hrs. The mould is removed from oven and kept at room temperature for 72 hrs. for complete curing.
The process of the present invention will now be illustrated with working examples which are intended to be typical examples to illustrate the working of the invention and are not intended to be taken restrictively to imply any limitation on the scope of the present invention.
WORING EXAMPLES:
EXAMPLE 1
For preparation of 100 gm of prepolymer, 88.7 gm of HTPB (hydroxyl value 41) is treated with 14 gm of TDI under continuous stirring in a closed vessel at 80°C. The reaction is continued till the desired isocyanate value (3-4%) is obtained. The product is stored in a sealed container to avoid exposure to air and moisture as it has
chance of gelling under high humidity condition. For synthesis of polyol, 2.5 gm of trimethylol propane is reacted with 99 gm of propylene oxide in presence of (cesium hydroxide) CsOH (0.1 - 0.2%). After attaining the desired hydroxyl value (27 to 33) the reaction is terminated. The catalyst is removed by treating with water. Finally, the product is dried to remove the moisture. For preparation of 100 gm of the hardener, 14 gm of 4,4' diamino 3,3' dichloro diphenyl methane and 18 gm of 4,4' diamino 3,3' dichloro triphenyl methane are mixed with 46 gm of polyol in a resin kettle under stirring at 80°C. The solution thus obtained is further charged with 9 gm of carbon black and 11 gm of CaCO3. The entire mass is thoroughly mixed with in a triple roll mill to get a homogeneous product. This mixture is called hardener. The hardener is finally checked for amine content. For preparing lOOgm of cured sealant compound, 74.6 gm of prepolymer is mixed with 25.4 gm of hardener. The viscous mass is thoroughly mixed for 10 to 15 minutes. Afterwards the mixture is poured onto a mould and the mass is spread with the help of a knife. The mould with mass is left for 24 hrs. at ambient conditions for curing, and in an oven for post curing at 60° C for 8 hrs. The mould is removed from oven and kept at room temperature for 72 hrs. for complete curing.
EXAMPLE 2
For preparation of 100 gm of prepolymer, 88.7 gm of HTPB (hydroxyl value 41) is treated with 14 gm of TDI under continuous stirring for about 8 hours in a closed vessel at 80°C. The reaction is continued till the desired isocyanate value (3-4%) is obtained. The product is stored in a sealed container to avoid exposure to air and moisture as it has chance of gelling under high humidity condition. For synthesis of polyol, 2.5 gm of trimethylol propane is reacted with 99 gm of propylene oxide in presence of CsOH (0.1 - 0.2%) After attaining the desired hydroxyl value (27 to 33) the reaction is terminated. The catalyst is removed by treating with water. Finally, the product is dried to remove the moisture. For preparation of 100 gm of the hardener, 32 gm of 44' diamino 33' dichloro diphenyl methane is mixed with 46 gm of polyol in a resin kettle under stirring at 80°C. The solution thus obtained is further charged with 9 gm of carbon black and 11 gm of CaCO3. The entire mass is thoroughly mixed with in a triple roll mill to get a homogeneous product. This mixture is called hardener. The hardener is finally checked for amine content. For preparing lOOgm of cured sealant, 75.6 gm of prepolymer is mixed with 24.4 gm of hardener. The viscous mass was thoroughly mixed for 10 to 15 minutes. Afterwards the mixture is poured onto a mould and the mass was spread with the help of a knife. The mould with mass is left for 24 hrs. at ambient conditions for curing, and in an oven for post curing at 60° C for 8 hrs. The mould is removed from oven and kept at room temperature for 72 hrs. for complete curing.
From the above moulded set, samples are cut as per ASTM D 412 and tested for tensile properties.
As per example 1 the mechanical properties are
Tensile strength 7 MPa
Elongation at break 300%
As per example 2 the mechanical properties are
Tensile strength 9 MPa
Elongation at break 200%
It is to be understood that the process of present invention is susceptible to adaptations, changes, modifications by those skilled in the art. Such adaptations, changes, modifications are intended to be within the scope of the present invention which is further set forth by following claims.


WE CLAIM;
1. A process for preparation of an improved polyurethane based sealant
comprises and characterised by the steps of:-
a) Synthesis of Pre-polymer carried out at a temperature of 40 to 80° C by
treating hydroxyl-terminated polybutadiene (HTPB) with toluene di-
isocyanate as herein described.
b) synthesis of polyether polyol by reaction of trimethylol with propylene
oxide in the presence of a catalyst such as NaoH, KoH, CsoH in
preferred quantity of 0.1 to 0.2 parts by weight.
c) preparation of hardener by mixing amines and polyol and charging the
mixture with a filler as herein described.
d) preparation of sealant by mixing preferably 1 equivalent of pre-polymer
and 0.8 to 1.2 equivalent hardner, followed by curing as herein
described.

2. A process as claimed in claim 1 wherein HTPB has preferably molecular
weight from 1000 to 3000 and hydroxyl value from 40 to 50.
3. A process as claimed in claim 1 wherein ratio of HTPB to toluene di-
isocyanate is preferably 1:2.
4. A process as claimed in claim 1 wherein reaction for synthesis of polyol
is carried out till hydroxyl value is preferably between 27 to 33.
5. A process as claimed in claim 1 wherein amine present in said
hardener is preferably a mixture of 4,4' diamino 3,3' dichloro diphenyl
methane and 4,4' diamino 3,3' dichloro triphenyl methane.
6. A process as claimed in claim 1 wherein for the said preparation of
hardener, the diamines are preferably 25 to 40% by wt. of the mixture
of diamines and polyol.
7. A process as claimed in claim 1 wherein for said preparation of
hardener, the temperature of mixing of diamines and polyol is
preferably 60 to 90° C.
8. A process as claimed in claim 1 wherein for said preparation of
hardener, the said filler is for example carbon black, with CaCO3 and
preferred percentage of two together is 10 to 15%.
9. A process for preparation of polyurethane based sealant composition as
claimed in claim 1 wherein said curing of the sealant composition is
carried out by leaving the composition at ambient conditions for 24
hours followed by curing in an oven at 60° C for about 8 hours.
10. A process for preparation of an improved polyurethane based sealant as substantially described and illustrated herein.

Documents:

223-del-2000-abstract.pdf

223-del-2000-claims.pdf

223-DEL-2000-Correspondence-Others-(22-02-2010).pdf

223-del-2000-correspondence-others.pdf

223-del-2000-correspondence-po.pdf

223-del-2000-description (complete).pdf

223-del-2000-form-1.pdf

223-DEL-2000-Form-15-(22-02-2010).pdf

223-del-2000-form-19.pdf

223-del-2000-form-2.pdf

223-del-2000-form-3.pdf

223-del-2000-gpa.pdf


Patent Number 213231
Indian Patent Application Number 223/DEL/2000
PG Journal Number 01/2008
Publication Date 04-Jan-2008
Grant Date 24-Dec-2007
Date of Filing 10-Mar-2000
Name of Patentee CHIEF CONTROLLER RESEARCH & DEVELOPMENT ORGANISATION
Applicant Address MINISTRY OF DEFENCE GOVERNMENT OF INDIA, B-341, SENA BHAWAN DHQ P.O. NEW DELHI-110011.
Inventors:
# Inventor's Name Inventor's Address
1 MANORANJAN PATRI NAVAL MATERIALS RESEARCH LABORATORY, SHIL BADLAPUR ROAD, MIDC AREA,ANANDNAGAR P.O. ADDITIONAL AMBERNATH, AMBERNATH (E) -421506, DIST. THANE, MAHARASHTRA.
2 UTTAM GOPAL SURYAVANSHI NAVAL MATERIALS RESEARCH LABORATORY, SHIL BADLAPUR ROAD, MIDC AREA,ANANDNAGAR P.O. ADDITIONAL AMBERNATH, AMBERNATH (E) -421506, DIST. THANE, MAHARASHTRA.
3 PRAMIL CHANDRA DEB NAVAL MATERIALS RESEARCH LABORATORY, SHIL BADLAPUR ROAD, MIDC AREA,ANANDNAGAR P.O. ADDITIONAL AMBERNATH, AMBERNATH (E) -421506, DIST. THANE, MAHARASHTRA.
PCT International Classification Number C08L 75/04
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA