|Title of Invention||
"A PROCESS FOR THE PREPARATION OF POLYCHLOROPRENE RUBBER VULCANISATE"
|Abstract||A process for the preparation of polychloroprene rubber vulcanisate an accelerator along with a synergetic co-accelerator such as herein described and the process comprising in the steps of conditioning in a manner as herein described separately of reinforcing filler as herein described and inorganic filler such as herein described incorporating raw polychloroprene, stearic acid metal oxide such as herein described anti-degradants such as herein described a reinforcing filler, inorganic filler through mill mixing procedure in the sequential order disclosed herein, cooling and adding slowly an accelerator and a co-accelerator followed by vulcanization at temperature between 60-80'C.|
|Full Text||FIELD OF INVENTION
This invention relates to a process for the mererahinm of polychloroprene rubber. The vulcanisate obtained by the process according to this invention has reduced cure time and lower processing temperature and can be used for application such as underwater electrical and electro-acoustic devises requiring protection from water, sheathing thermoplastics, collapsible mandrills, etc.
Vulcanisation is a process in which the rubber molecules are chemically cross linked to form a net work, thereby transforming the soft, weak plastic like material into an elastic solid. Polychloroprene, an emulsion polymer of 2-chlorobutadiene comprises of three major types. Type (1) is a copolymer of chloroprene with sulphur, while type (2) is a chloroprene homo polymer, where as types (3) are crystallization resistant grades. Presence of electrophilic chlorine in chloroprene units renders carbon carbon double bond less active. And hence sulphur vulcanization is difficult in polychloroprene rubbers. However, curing can be achieved with metal oxides, typically, zinc oxide/and or magnesium oxide. Sulphur modified types do not require organic accelerators, if curing is at temperature above 150 degree Celsius. However, cure rates and states of cure can be enhanced by addition of accelerators. In any case homo polymer (type-2) invariably requires organic accelerators.
US Patent 5,210,152 describes vulcanization of polychloroprene with a metal oxide in the presence of ami dine compounds as vulcanization accelerators. US Patent 3,968,092 describes the use of aromatic furfuryl polycarbamate as an accelerator for vulcanization of polychloroprene.
The major limitation of the above processes known in the art is that temperature of vulcanization in these processes is typically 150 to 190 degree Celsius or higher. The fabrication of devices bases on piezo-ceramics and piezo-polymers which use vulcanized polychloroprene of the known art, for encapsulation of a device, require temperature of about 150°C and such temperature are detrimental to the performance of the devices due to possible deterioration caused by accelerated thermal ageing of the sensing materials.
OBJECT OF THE INVENTION
The primary object of present invention is to provide a process for vulcanizing polychloroprene at or below 80°C and vu lean is ate obtained there-from.
Another object of present invention is to provide a process for vulcanizing polychloroprene which is energy saving.
Still another object of present invention is to provide a process that provides a rubber based passive acoustic material that has the required combination of processing characteristics, electrical insulation, low water absorption, and mechanical properties for use as encapsulation materials in tbe fabrication of underwater electro-acoustic transducers.
Yet another object of present invention is to provide a rubber vuleanisate which is processable at and below 80°C and simultaneously maintains high resistance to water absorption for use in underwater applications. DESCRIPTION OF INVENTION
According to this invention there is provided a process for the preparation of polychloroprene rubber comprising/it steps of conditioning in a manner as herein described
reinforcing filler as herein described and inorganic filler as herein described incorporating raw polychloroprene, stearic acid.metal oxide as herein described anti-degradants as herein described a reinforcing filler, inorganic filler through mill mixing in sequential order.
cooling and charaterised in that adding slowly an accelerator and a co-
accelerator followed by vulcanization at temperature between 60-80°C. The main inventive feature of the process is use of a novel accelerator which is a combination of derivative of thio urea used along with a derivative or polymeric imines. The imine derivative could be an individual polymeric imine or a suitable physical and/or chemical combination of polymeric imines or a reaction product of polymeric imine. The combination of two derivatives used as an accelerator, acts as an effective and synergic accelerator and enables lowering of vulcanization temperature from conventional 150*190°C to 60-80°C. The thio urea is from among diethyl thio urea, dimethyl thio urea, diphenyl thio urea, and ethyl methyl thio urea. The preferred derivative of polymeric imine is polyethyieneimine (PEI) or other polyimines such as the polymers derived from propyleneimine, 1,2 butyleneimine, 2, methylpropyleneimine. The process of vulcanization involves mixing of sulphur modified polychloroprene-Neoprene-ORT with fillers, red lead (PB304, anti-degradents, stearic acid and above mentioned novel accelerator. The antidegradents used are substituted trim ethyl qumoline, paraphenylene diamine, reinforcing filler used is carbon black and inorganic fillers used as talc and calcium carbonate. Naphthenic oil is used as a dispersion medium to aid processing.
According to the present invention, preparation of the polychloroprene vuleanisate is carried out by the following process wherein the different
constituents have been expressed as number of parts by weight with respect to the weight of polychloroprene taken as parts by weight;
(a) Conditioning separately the reinforcing fillers and inorganic fillers
by heating at 125±3°C in a tray drier and ensuring that the
materials are free from moisture. The reinforcing filler is N-550
carbon black, which is taken in quantity 20 to 40 parts preferably
25 to 35 parts by weight. The inorganic filters are talc and
precipitated calcium carbonate. The talc is taken in quantity 30 to
100 parts, preferably 60-80 parts and calcium carbonate is taken in
quantity 10 to 30 parts, preferably 15 to 25 parts by weight.
(b) Mixing raw polychloroprene taken in 100 parts by weight, for
about 5 minutes on a standard two roll mill, which has rolls
between 150 to 155 dia. And is equipped with retaining guides
having a distance of 250 to 280 mm between the guides. The speed
of the slow rolls is 25 ± 0.5 rpra and the ratio between slow and
fast roll is 1:1.4. The clearance between rolls is adjustable from 0.2
to 8 mm.
(c) Adding stearic acid, taken in quantity about 1 parts, slowly and
evenly across the mill at a uniform rate and making one 3/4 cut from
each end and incorporating.
(d) Adding antidegradents, 1,2 dihydro, 2,2 trimethyl quinoline taken
in quantity preferably 0.5 to 2 parts by weight and N-(l-3dimethyl
butyl) N-phenyl-p-phenylene diamine taken preferably in quantity
of 0.5 to 2 parts by weight.
(e) Adding the conditioned and cooled carbon black obtained by step
(a), evenly across the mill at a uniform rate followed by addition of conditioned and cooled inorganic fillers talc and calcium carbonate obtained by step (a). After incorporation of the fillers, opening the mill to 1.4mm and giving one cut "from each side.
(f) Dispersing red lead taken in quantity 7 to 25 parts preferably 10 to
15 parts by weight in naphthenic oil taken in quantity 5 to 20 parts
preferably 10 to 15 parts by weight and adding the dispersion thus
prepared, into the mill set at 1.4mm opening, evenly and uniformly
and making three " cutting on each side and cutting out the batch
from the mill. Thereafter the roll is set at a nip of 0.8 mm and the
rolled batch is passed endwise through the mill six times. The mill
is then opened to give a sheet of 4 mm, which is then cooled, to
(g) Banding back the cooled sheet on the rolls at a setting of 1.4 mm
and adding accelerator(s) evenly across the mill at a uniform rate.
The accelerator is a uniform combination of a derivative of thio
urea along with a derivative of polymeric iraine which acts as a
synergic co-accelerator which significantly lowers the
vulcanization temperature to 60 to SOT. The derivative of thio
urea is such as diethyl thio urea, dimethyl thio urea, diphenyl thio
urea or ethyl methyl thio urea, and is taken in quantity 0.5 to 4
parts preferably 1.5 to 2.5 parts by weight. The derivative of
polymeric imine is from polyethylene imine, poly propylene imine,
polyl, 2 butylenes imine, poly 2-methyl propylene imine, taken in
quantity 0.5 to 4 parts preferably 1.5 to 2.5 parts by weight. The
derivative of polymeric imine used is either taken individually or
as a suitably physical and/or a chemical combination of polymeric
iminies or a reaction product thereof. After addition of accelerators,
the mill is opened to a minimum gap of 4 mm. And the stock is
passed through the mill 3-4 times, folding it back on itself each
time and taking out the material as 4 mm thick sheet and keeping it
on a flat bed for maturing. The mill roll temperature is maintained
preferably at 30 ± 5°C by passing chilled water through the rolls.
It is to be noted that the vulcanisate obtained by the process is not a mere
admixture of constituents as the properties of the vulcanisate obtained by the
present invention are not mere aggregate of the properties of constituents.
The final vulcanisate obtained by the process has unique and specific
properties, which are distinctively different from the properties of individual
constituents. Where-as the raw rubber is soluble in organic solvents like
benzene, toluene, xylene, methyl ethyl ketone etc.; its vulcanisate is
insoluble in them. A rubber vulcanisate can be plastically deformed to
minimum twice, its original length; the same is not possible with raw rubber
or its mix. (The same rubber in un vulcanised state undergoes plastic
The invention will now be illustrated by the following example, which is intended to be typical, and is not intended to be taken restrictively to imply any limitation on the scope of the present invention. WORKING EXAMPLE
About 500 gm of N550 carbon black and lOOOgm of precipitated calcium carbonate were conditioned at 125±3°C in a dehumidifier assisted by tray drier in separate trays for about 1 hour. After drying, the material was stored in a moisture proof container. Following ingredients were mixed in a 10 kg
capacity two roil mill in the following order: - 1 kg of polychloroprene (Neoprene-GRT) was masticated for 5 minutes; 10 gm of stearic acid was added evenly across the mill and incorporated; 10 gin of quinoline (Vulcanox HS) and 20 gm of dianiine (Vulcanox 4020) were added and mixed. This was followed by addition and incorporation of 300g conditioned carbon black. 700g of talc and 200g of precipitated calcium carbonate (both dried separately) were mixed in succession to the stock. 13Og of red lead was dispersed in 120 g of naphthenic oil (Elasto-541). The dispersion was added evenly and uniformly and incorporated completely. Mix was mill rolled on the cooled rolls to sheet form, which was further cooled, to room temperature on a cold bed. Thereafer accelerator comprising 20 g of diphenyl thio urea and 20 g of polyethylene imine was incorporated. The sheet obtained (4mm thick) was matured on a flat bed. When the product obtained by the above process is compression molded at a temperature of 60°C and pressure 75 kg/cm2 for 90 minutes. The product exhibits the following properties:
1. Physical and mechanical properties(Table Removed)
2. Cure Characteristics MDR 2000,1-degree are
(Table Removed)It is to be understood that the process of the present invention is susceptible to modification, changes and adaptations by those skilled in the art. Such modifications, changes, adaptations are intended to be within the scope of the present invention which is further set forth under the following claims:
1. A process for the preparation of polychloroprene rubber vulcanisate an accelerator along with a synergetic co-accelerator and the process comprising in the steps of conditioning separately of reinforcing filler and inorganic filler, incorporating raw polychloroprene, stearic acid metal oxide, anti-degradants, a reinforcing filler, inorganic filler through mill. mixing procedure in the sequential order disclosed here-in, cooling and adding slowly an accelerator and a
co-accelerator followed by vulcanisation at temperature
between 60 to 80 C.
2. A process as claimed in claim 1 wherein metal oxide is
3. A process as claimed in claim 1 wherein metal oxide is
taken in quantity 7 to 25 parts preferably 10 to 15
parts by weight of polychloroprene taken as 100 parts.
4. A process as claimed in claim 1 wherein stearic acid
is about 1 part by weight of polychloroprene.
5. A process as claimed in claim 1 wherein anti-degradants
are 1,2 dihydro, 2,2 trimethyl quinoline and N- (1-3
dimethylbutyl), N-phenyl-p- phenylene diamine each
present in an amoung of 0.3 to 2 parts by weight of
6. A process as claimed in claim 1 wherein the reinforcing
filler is N-550 carbon black. 7. A process as claimed in claim 1 wherein the reinforcing
filler present in an amount of 20 to 40 parts preferably 23 to 35 parts.
8. A process as claimed in claim 1 wherein the inorganic
fillers are talc and precipitated calcium carbonate
present in an amount of 30 to 100 parts preferably 6(3
to 80 parts and in quantity 10 to 30 parts preferably
15 to 25 parts respectively.
9. A process as claimed in claim 1 wherein the accelerator
is a combination of derivative of thio urea and a
derivative of polymeric imine as a synergetic co-
10. A process as claimed in claim 1 wherein said, derivative
of thio urea is preferably from among diethyl thio
urea, dimethyl thiourea, diphenyl thiourea and ethyl
methyl thio urea.
11. A process as claimed in claim 1 wherein said derivative
of thio urea is present in an amount of 1.5 to 2.5
parts by weight of polychloroprene
12. A process as claimed in claim 1 wherein said derivative
of polymeric imine, poly 1,2 butylene imine,
polypropylene imine is taken individually or in
combination of polyimines or a reaction product thereof.
13. A process as claimed in claim 1 wherein derivative of
polyimine is present in an amount of 1.5 to 2.5 parts
by weight of polychloroprene.
14. A process as claimed in claim 1 wherein said
conditioning of said reinforcing filler is carried out
o at 125+3 C.
15. A process for the preparation of polychloroprone rubber
vulcanisate substantially as described herein.
|Indian Patent Application Number||514/DEL/2001|
|PG Journal Number||01/2009|
|Date of Filing||24-Apr-2001|
|Name of Patentee||ADDITIONAL DIRECTOR (IPR) DEFENCE RESEARCH & DEVELOPMENT ORGANISATION|
|Applicant Address||DEFENCE RESEARCH & DEVELOPMENT ORGANISATION MINISTRY OF DEFENCE, GOVT OF INDIA, B-341, SENA BHAWAN, DHQ P.O. NEW DELHI - 110011, IDNIA.|
|PCT International Classification Number||C08F 036/00|
|PCT International Application Number||N/A|
|PCT International Filing date|