Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-03-11
2001-09-04
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
active
06284827
ABSTRACT:
The invention relates to a polymerizable fluorine-containing composition and use thereof for the preparation of cured polymer masses having a reduced content of fluoride ions extractable with water. The invention further relates to the use of this composition as a bonding, sealing, coating and potting material, more particularly in such fields of application where a high content of fluoride ions extractable with water is undesirable.
It is known to employ fluorine-containing formulation constituents for the preparation of reaction masses curing by polyreactions. For example, fluorine-containing monomers or fluorine-containing fillers or additives are used. It is further known to employ fluorine-containing initiators or catalysts in order to achieve satisfactory curing rates. There is extensive use of fluorine-containing photoinitiators comprising perfluorinated anions, and such use has been described in many patent documents, for example in
Use of borofluoride complexes as catalysts for polyreactions is likewise known (cf. Makromolekulare Chemie 191 (1990), p. 1403). What is a disadvantage in connection with the use of fluorine-containing formulation constituents in compositions curing by polyreactions is the usually very high content of fluoride ions extractable with water of the cured masses. This proportion of readily mobile ions can be undesirable when applying the compositions. When the compositions are used for bonding, potting and coating of electronic devices or in mounting such devices, a high proportion of fluoride ions extractable with water may result in the appearance of corrosion and thus impair the operability of the devices.
It is the object of the invention to propose polymerizable compositions containing fluorine-containing formulation constituents and resulting in cured masses having a reduced content of fluoride ions extractable with water.
This object is achieved in accordance with the invention in that the composition containing at least one polymerizable compound and at least one fluorine-containing compound additionally contains at least one magnesium compound and has, after curing, a low content of fluoride ions extractable with water.
It has been surprisingly found that by adding at least one magnesium compound the content of such fluoride ions which are extractable with water of the cured polymer mass obtained from the polymerizable composition is distinctly reduced as compared with the content of fluoride ions extractable with water of cured polymer masses of the known type, which differ from the masses obtainable according to the invention merely in that the polymerizable fluorine-containing compositions have no magnesium compound(s) added thereto. Preferably, the content of fluoride ions extractable with water after curing is lower by at least 40% as compared with the content of fluoride ions extractable with water of an otherwise identical composition which does not contain a magnesium compound. In a particularly preferred composition the content of fluoride ions extractable after curing is lower by at least 60% than without a magnesium compound.
The surprising effect of the addition of one or more magnesium compound(s) has, to date, never been described nor even presumed in the previously published prior art.
In an advantageous embodiment of the invention the polymerizable fluorine-containing composition contains the at least one magnesium compound in an amount of from 0.001 to 60 parts by mass, in an especially preferred embodiment in an amount of from 0.01 to 10 parts by mass, each per 100 parts by mass of the total composition.
Within the ranges indicated, the required concentration of the magnesium compound(s) may be set in wide limits. In general, even small proportions of a magnesium compound, for instance 0.05 parts by mass per 100 parts by mass of the composition, will cause a distinct reduction in the content of fluoride ions extractable with water of the cured masses.
The magnesium compounds may be present in the liquid composition in a dissolved or an undissolved form.
In the case of magnesium compounds soluble in the composition the addition is performed in a simple manner during the mixing process. Although soluble magnesium compounds are less effective than insoluble magnesium compounds as regards the reduction in the content of fluoride ions extractable with water, they offer the advantage of a greater homogeneity of the compositions, above all in low-viscosity compositions. A soluble magnesium compound of this kind is, for instance, magnesium acetylacetonate, a magnesium chelate compound.
The insoluble magnesium compounds, which are preferred owing to their greater effectiveness, may lead to inhomogeneities due to the settling of solid particles in the compositions. To reduce this risk it should be made sure that the magne- sium compounds are employed in a very finely divided form. The settling of the magnesium compounds from the liquid composition can additionally be reduced or avoided entirely by applying suitable thixotroping agents, such as pyrogenic silicic acids, which may be silanized, if required.
The at least one magnesium compound is preferably selected from the group consisting of magnesia, magnesium hydroxide, magnesium carbonate, magnesium silicate, magnesium carboxylates, magnesium chelates, and magnesium alcoholales. Of these, particular preference is given to the inorganic magnesium compounds, in particular magnesium silicate, magnesium carbonate, magnesium hydroxide, and magnesia, each alone or in a mixture with each other.
For many applications it is convenient to use especially pure magnesium compounds.
In another preferred embodiment of the invention, the polymerizable composition contains the magnesium compound(s) in a dispersed, finely divided form having a maximum particle size of 50 micrometers (&mgr;m).
Where magnesia is employed as one of the preferred magnesium compounds, both caustic, calcined magnesia and also sintered magnesia or fused magnesia may be utilized; a person of ordinary skill in the art will select the type which is most favorable for any particular application, depending on the composition of the polymerizable fluorine-containing composition.
Of the organic magnesium compounds, preference is given to magnesium carboxylates and magnesium alcoholates. Depending on the structure of the organic residue, these magnesium compounds may be soluble or insoluble in the polymerizable fluorine-containing composition.
Aside from the at least one magnesium compound, the polymerizable fluorine-containing composition may otherwise be composed in the most varied of ways. The mechanism of curing of the composition (cationic, anionic, radical or by poly-condensation) is of no importance here.
In a further preferred embodiment of the invention, the at least one polymerizable compound is a compound which contains at least one epoxide group and which is selected from the group consisting of glycidyl ethers and compounds con- taining epoxycyclohexyl groups.
Preferably utilized are aliphatic, cycloaliphatic and/or aromatic epoxy resins which may contain fluorine. The diglycidyl ethers of bisphenols, glycidyl ethers of novolaks and compounds containing epoxycyclohexyl groups such as for instance 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexyl carboxylate or bis(3,4-epoxycyclohexylmethyl)adipate are typical representatives of this family.
Fluorine-containing (meth)acrylates may however also be used as polymerizable compounds.
The employment of at least one magnesium compound in accordance with the invention for the reduction in fluoride ions in the aqueous extract of the cured polymer masses is especially useful when fluorine-containing formulation constituents are, or have to be, applied for achieving specific effects in curing or in use of the polymer masses. This is the case for example in the cationic polymerization of epoxy resins where iodonium, sulphonium or ferrocenium compounds having a complex fluorine-containing anion are typically applied as catalysts or initiators. Preferably used anions
Dengler Dietmar
Eckhardt Gunther
Somnitz Ursula
Cain Edward J.
Delo Industrieklebstoffe GmbH Co. K
Haynes, Soloway, Hennessey, Grossman & Hage, P.C.
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