Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From ketone or ketene reactant
Reexamination Certificate
2001-11-02
2003-07-29
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From ketone or ketene reactant
C528S397000, C528S422000, C528S425000, C528S482000
Reexamination Certificate
active
06600005
ABSTRACT:
DESCRIPTION
The invention relates to a process for preparing poly-(1,4-phenyleneazine-N,N-dioxide), which is also called poly-N,N-diazadioxide, and its nuclearly-substituted derivatives by oxidation of p-benzoquinonedioxime or its corresponding nuclearly-substituted derivatives, by means of polyanions of the halogens bromine or iodine.
Poly-(1,4-phenyleneazine-N,N-dioxide) is a highly effective cross-linker in rubber mixtures or rubber/metal binding agents. Moreover, the use of this substance as a reusable evaporation chemical for the manufacture of electronic circuits by way of laser inscriptions (Solventless Laser-Imageable Resist Process) is also known.
Principally available for the synthesis of poly-(1,4-phenyleneazine-N,N-dioxide) is only an oxidative path, starting from p-benzoquinonedioxime or its nuclearly-substituted derivatives, because the reduction of the corresponding nitro compounds cannot be kept at the level of the nitroso compound. Chlorine, nitrogen monoxide/sodium hypochlorite, sodium chlorate, nitric acid, iron III chloride and potassium hexacyanoferrate (III), for example, are known as oxidising agents.
The primary reaction product of all of the above-mentioned oxidation reactions is a dinitroso compound. A characteristic of almost all p-dinitroso compounds is their spontaneous polymerisation to form poly-N,N-azodioxides. For example, p-dinitrosobenzene is present as a monomer at −240° C. and as a dimer or oligomer between −90° C. and −50° C. At higher temperatures (−10° C. to 100° C.), only poly-(1,4-phenyleneazine-N,N-dioxide) is still found.
A disadvantage to some extent of the manufacturing processes known hitherto is, in most cases, the enormous salt load which accumulates. The following table gives examples of this:
TABLE 1
Salt load produced in the oxidation of p-
benzoquinonedioxime as a function of the oxidising
agent used.
Salt load per 100 kg
Oxidising agent
poly-N,N-azodioxide
K
3
[Fe(CN)
6
]
510
kg complex salt
FeCl
3
184
kg FeCl
2
NO/NaOCl
85
kg NaCl
NaClO
3
/HCl
85
kg NaCl
Other processes are salt-load-free, but have other disadvantages instead. Thus, oxidation by means of nitric acid with yields of <80% is less economical and, because of the necessity of having to wash the reaction product effectively, a disadvantageous formation of waste water results.
Oxidation with elemental chlorine first of all takes place in a salt-load-free manner by forming hydrochloric acid, as does oxidation in the H
2
O
2
/hydrochloric acid system. In this case, elemental chlorine is released in situ from hydrochloric acid and hydrogen peroxide (equation 1). Chlorine is also used in this case as the actual oxidising agent.
2 HCl+H
2
O
2
→Cl
2
+2 H
2
O (1)
Cl
2
+H
2
O
2
→2Cl
−
+2 H
+
+O
2
(2)
The possible reaction of the chlorine which is formed with hydrogen peroxide in accordance with equation (2) can lead to the release of oxygen. Direct oxidation of p-benzoquinonedioximes with hydrogen peroxide is not observed, even in the case of a raised reaction temperature.
In this process, the mother liquor which results, including any wash water which may be required, has to be neutralised, which in turn leads to the creation of a salt load. It is also disadvantageous that continuing oxidation of the reaction product to form p-dinitroso compounds cannot be ruled out. These compounds are explosive and highly toxic.
In the context of mechanistic considerations, A. Ermakov and Y. F. Komkova (Zh. Org. Khim. 20, 10, 2252 (1984)) refer, corresponding to the oxidation with chlorine (from H
2
O
2
/hydrochloric acid), to the oxidation with iodine formed in situ (from H
2
O
2
and potassium iodide) analogously to equation (1). A manufacturing process with iodine or iodine formed in situ is not described in this text, however.
The direct conversion of p-benzoquinonedioxime with elemental iodine (Comparative Example A) leads, however, to the primary dinitroso product only after relatively long reaction times in a reaction which is not very uniform, and the product can moreover be obtained only in very low yields. Elemental iodine thus appears to be an oxidising agent which is not very suitable for the industrial oxidation of p-benzoquinonedioximes.
Thus, until now, there has not been an industrial process which allows the quantitative oxidation of p-benzoquinonedioximes to form the corresponding poly-N,N-diazadioxides with strict avoidance of the formation of toxic dinitro by-products, and which additionally avoids a salt load, even an indirect one.
The object of the invention is therefore to overcome the disadvantages of the prior art and to develop a process for preparing poly-(1,4-phenyleneazine-N,N-dioxide) and its nuclearly-substituted derivatives, which process is distinguished by a complete conversion of the reaction partners whilst excluding the formation of dinitro derivatives, the avoidance of salt loads and a clear reduction in the amounts of waste water.
The object is achieved by the process presented in claim 1. Claims 2 to 12 develop the process further.
Surprisingly, it has been found that easily accessible derivatives of the halogens, namely the polyanions, lead to a clear increase in the chemical selectivity of the oxidation reactions described above. Polyanions (X
Z
−
, z ≧3) of the halogens (X) are very easily accessible by means of the conversion of halide ions (X
−
) with the elements, for example:
X
2
+X
−
→X
3
−
(3)
With increasing atomic number, trihalides of chlorine, bromine and iodine form increasingly easily, as is evident from the equilibrium constants in accordance with Table 2 that apply for the solvent water.
Table 2: Equilibrium constants of the trihalide formation in water (X
2
+X
−
→X
3
−
)
K
chlorine
=0.01
K
bromine
=18
K
iodine
=725
It can be seen that a very large excess of chloride ions is required in order to form trichloride ions (Cl
3
−
). Experiments with rising concentrations of chloride ions in the HCl/H
2
O
2
system actually lead to an increased chemical selectivity of the oxidation process.
If the oxidation is carried out at a given temperature in 15% hydrochloric acid, the poly-N,N-diazadioxide is obtained with yields of 90 to 95% and contains approximately 1% p-dinitrobenzene. An increase in the concentration of hydrochloric acid to 25 or 35% leads, with dinitrobenzene contents of only 6000 or 1200 ppm, respectively, in the end product, to a clear reduction in the formation of by-products. The increased chemical selectivity, however, is linked with a reduction in the isolated yields to approximately 80%. Therefore, the alteration of the redox potentials that accompanies the variation of the chloride ion concentration thereby leads to a loss of reactivity.
Because of the comparatively great equilibrium constants (Table 2) in the case of the halogens bromine and iodine, the bromide concentration or iodide concentration does not have to be chosen to be as high in order to obtain a comparatively great selectivity. Therefore, only the polyanions of the bromine and of the iodine are of practical significance for the process in accordance with the invention, in which case mainly tribromide or triiodide are used. The oxidising polyanions are to be used in at least a stoichiometric amount and at most in double the stoichiometric amount.
Advantageously, the corresponding alkali compound can be used as the tribromide or triiodide.
Instead of being added separately, the tribromide or triiodide can also be produced in situ from a bromide compound or iodide compound respectively and H
2
O
2
, in which case the corresponding alkali compound is advantageously used.
Particularly advantageously, the process can be carried out if triiodide (I
3
−
) is selected as the oxidising agent, which is obtained in situ from an alkali iodide and H
2
O
2
. The alkali iodide can thereby be used in a catalytic to stoichiometric amount of 0.1 to 100% by
Dehnicke Stefan
Krtsch Bernhard
List Ernst
Rullman Helmut
Zellner Adolf
Falk Stephen T.
Rohm and Haas Denmark Finance A/S
Truong Duc
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