Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-12-01
2003-10-21
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C525S373000, C544S359000, C548S148000, C508S274000
Reexamination Certificate
active
06635696
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates to thiadiazole derivatives useful as accelerators and/or curing agents for halogenated polymers in rubber vulcanization processes, and to halogenated polymer compositions containing the thiadiazole derivatives, as well as a method of preparing the same.
Vulcanizable rubber compositions present certain inherent problems in terms of handling and storage. For example, prior to the curing, the uncured rubber may often degrade during storage due to hydrolytic instability of the additives contained therein. As a result the cure reproducibility from batch to batch in the vulcanization process can often vary. However, batch-to-batch cure reproducibility is an important parameter of quality control.
It is known that halogen-containing polymers may be compounded with curing agents, accelerators and other compounds in order to prepare vulcanizable rubber compositions which are useful in a variety of applications. A description of curing agents and accelerators, as well as other components of natural and synthetic rubbers can be found in Kirk-Othmer's Encyclopedia of Chemical Technology, John Wiley & Sons, 4th Edition, at pages 460-481.
Despite the availability of curing agents and/or accelerators for halogenated polymers, there is a continuing need for curing agents and/or accelerators that allow for good bin storage characteristics and improved batch-to-batch cure reproducibility.
Accordingly, it is an object of the present invention to compounds useful as curing agents and/or accelerators for rubber vulcanization processes which provide good bin storage properties for uncured rubber and improved consistency in cure reproducibility.
It is yet another object of the present invention to provide curable rubber compositions which exhibit good bin storage properties and improved consistency in cure reproducibility and methods of preparing the cured rubber compositions.
SUMMARY OF THE INVENTION
In accordance with the present invention, an additive is provided including a dithiocarbamyl-1,3,4,-thiadiazole derivative having formula (I), or an isomer thereof:
where R
1
and R
2
are independently a radical being either an alkyl, a cycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R
1
and R
2
together form a 3- to 7-membered cyclic ring structure; and X is (i) hydrogen, (ii) a dithiocarbamyl radical having formula (II):
where R
3
and R
4
are independently a radical being either an alkyl, a cycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R
3
and R
4
together form 3- to 7-membered cyclic ring structure, or (iii) a mixture thereof. In a preferred embodiment, X is hydrogen, and R
1
and R
2
are independently a radical being either an ethyl, an isopropyl, a butyl, or an isobutyl, or R
1
and R
2
together form a 6-membered cyclic ring structure, with a piperidyl radical being preferred.
In another embodiment the present invention provides an additive including a dithiocarbamyl-bis-1,3,4,-thiadiazole derivative having formula (III), or an isomer thereof:
where X is hydrogcn or a dithiocarbamyl radical having formula (II)
where R
3
and R
4
are independently a radical being either an alkyl, a cycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R
3
and R
4
together form 3- to 7-membered cyclic ring structure. In a preferred embodiment, X is hydrogen.
The present invention also provides a curable polymer composition including at least one halogenated polymer and at least one of the above-described additives of the present invention. A method is also provided for preparing a cured polymer composition including at least one halogenated polymer and at least one of the additives of the invention.
The additives of the present invention are particularly useful as curing agents and/or accelerators for halogen-containing polymer compositions, and provide good bin storage characteristics for the uncured polymer composition and improved cure reproducibility. These and other advantages of the present invention will be more readily apparent from the detailed description set forth below.
DETAILED DESCRIPTION OF THE INVENTION
It has now been discovered that certain hydrocarbyl dithiocarbamyl-1,3,4-thiadiazole derivatives having a disulfide linkage are useful as curing agents and accelerators in halogen-containing polymer compositions. The thiadiazole derivatives of the present invention have been found to provide good bin storage characteristics and improved cure reproducibility when used as additives in halogen-containing polymer compositions.
In one embodiment an additive is provided that includes a dithiocarbamyl-1,3,4,-thiadiazole derivative having formula (I):
where R
1
and R
2
are independently a radical being either an alkyl, a cycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R
1
and R
2
together form a 3- to 7-membered cyclic ring structure; and X is (i) hydrogen, (ii) a dithiocarbamyl (i.e., DTC) radical having formula (II):
where R
3
and R
4
are independently a radical being either an alkyl, a cycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R
3
and R
4
together form substituted or unsubstituted 3- to 7-membered cyclic ring structure, or (iii) a mixture thereof. Preferably, X is hydrogen while R
1
and R
2
are independently a C
1
to C
5
alkyl radical such as an ethyl, an isopropyl, a butyl, or an isobutyl, or R
1
and R
2
together form a substituted or unsubstituted 6-membered cyclic ring structure (e.g., a piperidyl radical).
In another embodiment the present invention provides an additive that includes a dithiocarbamyl-bis-1,3,4,-thiadiazole derivative having formula (III):
where X is (i) hydrogen, (ii) a dithiocarbamyl radical having formula (II):
where R
3
and R
4
are independently a radical being either an alkyl, a cycloalkyl, an alkenyl, an aryl, an arylalkyl, or an alkylaryl, or R
3
and R
4
together form 3- to 7-membered cyclic ring structure, or (iii) a mixture thereof. In a preferred embodiment, X is hydrogen.
The derivatives of formulas (I) and (III) are synthesized following techniques known in the art. For example, compounds having formula (I) can be synthesized by reacting 2,5-dimercapto-1,3,4,-thiadiazole (i.e., DMTD) with a dithiocarbamic acid in which the amine moiety is a tertiary amine having substituents R
1
and R
2
, or R
3
and R
4
. The reaction is carried out in the presence of an oxidizing agent (e.g., hydrogen peroxide). As known in the art, dithiocarbamic acid is not readily isolatable and thus needs to be formed in situ to provide the starting material. The dithiocarbamic acid intermediate is synthesized in situ by reacting carbon disulfide with the appropriate secondary amine (e.g., dibutyl amine to form dibutyl dithiocarbamic acid). Likewise, compounds of formula (III) where X is hydrogen can be synthesized by first forming in situ bis-(1,4-piperazine dithiocarbamic acid) from homopiperazine and carbon disulfide. The dithiocarbamic acid intermediate is then reacted with 2,5-dimercapto-1,3,4-thiadiazole in the presence of an oxidizing agent. The reaction conditions (e.g., temperature and time) are variable and can be easily modified by one of ordinary skill in the art following the teachings set forth herein.
While not wishing to be limited by theory, those skilled in the art will recognize that the additives of the invention may additionally contain positional isomers of the derivatives having formulas (I) and (III) due to tautomerization or other similar rearrangement of the substituents on the DMTD moiety. In accordance with the invention, reference to “an isomer thereof” means positional isomers. Positional isomers of formulas (I) and (III) are also useful as curing agents and accelerators. Positional isomers of formula (I) would have the following structures:
Likewise, similar rearrangements for compounds having formula (III) are also expected.
The above-described additives of the invention, alone or in combination, are admixed with a major amount of at least one halogenated polymer to provide a c
Cheng Francis S.
Karol Thomas J.
Mulcahy Peter D.
Norris & McLaughlin & Marcus
R.T. Vanderbilt Company, Inc.
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