Compositions – Preservative agents – Anti-oxidants or chemical change inhibitants
Reexamination Certificate
2002-07-25
2004-04-27
Desai, Rita (Department: 1625)
Compositions
Preservative agents
Anti-oxidants or chemical change inhibitants
C546S210000, C546S184000, C546S265000, C548S559000, C548S542000
Reexamination Certificate
active
06726854
ABSTRACT:
The present invention relates to an inhibitor composition and its use for stabilizing substances capable of free radical polymerization, and a mixture containing the inhibitor composition.
Many compounds which have one or more vinylically unsaturated groups have a pronounced tendency to free radical polymerization. Such compounds are also used specifically as monomers for free radical polymerization. At the same time, however, the pronounced tendency to free radical polymerization is a disadvantage in that undesired free radical polymerization of the vinylically unsaturated compounds can occur both during storage and during chemical and/or physical processing (for example distillation or rectification), in particular under the action of heat and/or light. Undesired free radical polymerization can have various adverse effects, especially if polymer is precipitated. For example, in the distillation of vinylically unsaturated compounds, polymer formed by free radical polymerization may be deposited on the surface of the evaporator used—the tendency to free radical polymerization is particularly pronounced there owing to the high temperature. Polymerization in the region of the surface of an evaporator generally means that a polymer layer forms on the surface. Owing to the insulating effect of the polymer layer, the heat transfer is reduced in an undesired manner. Undesired polymer formed by free radical polymerization can, however, also block the internals of rectification columns, which causes undesired pressure drops. The deposition of polymer may finally necessitate stoppage of the rectification process, since the deposited polymer has to be removed in order to continue the rectification.
It is therefore general practice to add compounds which act as inhibitors or retarders of free radical polymerization to vinylically unsaturated compounds capable of free radical polymerization and mixtures which contain such compounds. While inhibitors suppress the free radical polymerization, including their complete reaction with free radicals, retarders slow down the free radical polymerization. Inhibitors and retarders are generally combined under the general term stabilizers. Below, however, both inhibitors and retarders are to be understood as meaning inhibitors. The use of inhibitors or retarders is of importance both during storage and during chemical and/or physical treatment (for example in distillation) of vinylically unsaturated compounds capable of free radical polymerization.
U.S. Pat. No. 4,187,382 relates to a process for the esterification of organic diols with acrylic acid. It is recommended to pretreat the diol with triphenyl phosphite in order thus to reduce the tendency of the reaction mixture to free radical polymerization. A phenolic polymerization inhibitor is proposed as a further inhibiting component.
DE-A 29 13 218 discloses a process for the preparation of acrylates or methacrylates, in which the polymerization inhibitor used comprises organic phosphites together with phenolic polymerization inhibitors.
The abovementioned inhibitor compositions contain phosphorus compounds which have phosphorus in the oxidation state +3 and further phenolic compounds. One object is further to improve the action of such systems in the stabilization of vinylically unsaturated compounds.
It is an object of the present invention to provide a highly active inhibitor composition which contains chemical compounds having phosphorus in the oxidation state +3 and/or phenolic compounds. This inhibitor composition should be particularly effective in that the inhibiting effects of the components present in it should reinforce one another in a synergistic manner.
We have found that this object is achieved by providing an inhibitor composition containing, as components, a) at least one nitroxyl radical (derivative), b) at least one phenol (derivative) and c) at least one further chemical compound which contains at least one phosphorus atom which has the oxidation state +3.
The oxidation state of an atom within a covalent compound is to be understood as meaning a number which has a positive or negative sign and indicates the charge which the atom would have if the bonding electron pairs of the covalent bonds in which the atom participates were assigned to the more electronegative bonding partner in each case. In the case of electron pairs of covalent bonds between two identical atoms, each atom contains one electron. The electronegativity is to be regarded here as a measure of how strongly an atom in a molecule attracts bonding electron pairs which are bonded to the atom. The electronegativities relevant at present are those according to H. R. Christen, Grundlagen der allgemeinen und anorganishcen Chemie, Verlag Sauerländer, Aarau, Diesterweg-Salle, Frankfurt am Main (1973). For the most important elements of the Periodic Table, these electronegativities have the following values:
Be (1.5); B (2.0); H (2.1); C (2.5); Si (1.8); Ge (1.7); N (3.0); P (2.1); As (2.0); Sb (1.8); O (3.5); S (2.5); Se (2.4); Te (2.1); F (4.0); Cl (3.0); Br (2.8); I (2.4).
In particular, orthophosphorous acid or an ester of orthophosphorous acid may be used as compounds (component c)) which contain at least one phosphorus atom having the oxidation state +3. Esters of orthophosphorous acid are also referred to as phosphites. Orthophosphorous acid can also be present as a salt (generally as an alkali metal or ammonium salt). Preferred bonding partners of phosphorus are the elements C, S, O, N and/or H.
Phosphonites (esters of phosphonous acid), in particular those known as stabilizers, are also suitable.
Particularly suitable phosphites (i.e. the esters of orthophosphorous acid) and phosphonites (esters of phosphonous acid) include, for example, triphenyl phosphite, diphenyl alkyl phosphite, phenyl dialkyl phosphite tris(nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythrityl, diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, diisodecyl pentaerythrityl diphosphite, bis(2,4-di-tert-butylphenyl) pentaerythrityl diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythrityl diphosphite, diisodecyloxypentaerythrityl diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl) pentaerythrityl diphosphite, bis(2,4,6-tris(tert-butylphenyl)) pentaerythrityl diphosphite, tristearyl sorbityl triphosphite, tetrakis(2,4-di-tert-butyl-phenyl) 4,4′-biphenylene diphosphite, tetrakis(2,4-di-tert-butylphenyl) 4,4′-biphenylene diphosphonite, 6-isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenzo[d,g]-1,3,2-dioxaphosphocine, 6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyldibenzo[d,g]-1,3,2-dioxaphosphocine, bis(2,4-di-tert-butyl-6-methylphenyl) methyl phosphite and bis(2,4-di-tert-butyl-6-methylphenyl) ethyl phosphite.
Esters of orthophosphorous acid (phosphites) of the formula (I) or esters of phosphonous acid (phosphonites) of the formula (II)
are advantageously used,
where R, R′ and R″ may be identical or different and are organic radicals, in particular C
1
-C
20
-alkyl, hydroxy-C
2
-C
4
-alkyl, halo-C
2
-C
4
-alkyl, in particular chloroalkyl, C
6
-C
10
-aryl, in particular phenyl, or C
1
-C
8
-alkyl-substituted aryl (in particular C
1
-C
4
-alkyl-substituted phenyl). Furthermore, two of the three organic radicals R, R′ and R″, together with the phosphorus and the two oxygen atoms, may form a heterocyclic structure (for example having 5 or 6 atoms).
Trimethyl, triethyl, tributyl, trihexyl, trioctyl, triphenyl, tri-p-cresyl, trixylyl, tritolyl and tri-&bgr;-chloroethyl phosphite may be mentioned by name. However, dimethyl, diethyl, dibutyl, dioctyl, diphenyl, ditolyl and dixylyl phosphite are also inhibitors suitable according to the invention. Particularly suitable are the species known under the trade names Irgafos® 168 (producer Ciba AG), Irgafos® P-EPQ (producer Ciba AG) or Ultranox® 626 (producer GE-Speciality Chemicals GmbH):
Other suitable chemical compounds which contain at least one phosphorus atom which has the oxidation
Jaworek Thomas
Keller Harald
Schliephake Volker
Schröder Jürgen
Sutoris Heinz Friedrich
BASF - Aktiengesellschaft
Desai Rita
LandOfFree
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