Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2003-04-11
2004-08-10
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S137000, C524S140000, C524S141000, C524S145000, C252S609000
Reexamination Certificate
active
06774163
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel flame retardant system for polymers comprising a mixture of two different aryl phosphates, to its preparation, and to its use.
2. Brief Description of the Prior Art
The high combustibility of many polymers means that they have to be provided with flame retardants. One way of increasing the flame retardancy of polymers is to add incombustible or low-combustibility fillers, such as glass, powdered quartz, wollastonite, etc. Another way is to use inorganic flame retardants. Examples which may be mentioned are boron compounds and metal hydroxides. However, large amounts of these types of flame retardants have to be used for adequate flame retardancy. This leads to major problems in the production and processing of polymers.
Use of halogenated compounds is very widespread, examples being tetrabromo-bisphenol A or the corresponding bisepoxide derived therefrom, decabromodiphenyl ether, and brominated polystyrenes. However, the use of halogenated flame retardants is controversial. During combustion corrosive gases such as hydrogen chloride or hydrogen bromide can be produced. There is also a risk that severely toxic dioxin-like products are formed.
U.S. Pat. Nos. 3,689,602, 3,192,242, GB-A-1 487 609 and EP-A-465 605 disclose the use of halogen-containing and also halogen-free phosphates as flame retardants for polymers. However, organophosphorus compounds which are not incorporated into the polymer matrix have plasticizing properties. Large amounts of these phosphorus compounds have to be added in order to achieve effective flame retardancy, and they therefore impair the mechanical and electrical properties of the polymers to an unacceptable degree for many applications.
For example, the strength values and/or the glass transition point are lowered. In addition, some of these compounds are thermally unstable or unstable with respect to hydrolysis. The halogen-containing phosphates are moreover controversial from an environmental point of view, as mentioned above.
It is known that the use of certain aryl thiophosphates or aryl phosphates containing certain functional groups brings about an increase in the flame retardancy of polymers, in particular resins, such as epoxy resins, without substantially impairing their thermal and mechanical properties.
DE-A-44 00 441 has previously disclosed the sole use of the aryl phosphates (termed “aryl phosphate type I” hereinafter) containing functional groups. However, there was a need to make further improvement in the use of aryl phosphates as flame retardants for polymers according to DE-A-44 00 441. For example, these aryl phosphates have never been able to pass a fire test to the UL 94 standard. Furthermore, glass transition temperatures above 150° C. were generally achieved using a combination of aryl phosphates type I and a further amine hardener. Resins which comprise solely this aryl phosphate generally begin to soften at from 130 to 140° C. These temperatures are too low for use in electrical devices or in printed circuits (“printed circuit boards”). Another disadvantage of DE-A-44 00 441 is that the aryl phosphates described therein discolour the polymers.
An object on which the invention was based was to provide a flame retardant which can be used for polymers and which has at least one of the following properties: high glass transition temperatures and/or markedly less discoloration/yellowing and/or, required for flame retardancy, a very high phosphorus content, the flame retardant being used in polymers and in particular in epoxy resins.
SUMMARY OF THE INVENTION
The invention provides a mixture comprising aryl phosphates type I of the general formula (I)
where
R
1
to R
4
, independently of one another, are hydrogen, alkyl, cycloalkyl, alkenyl, aralkyl or aryl, where the aryl moiety may be unsubstituted or have alkyl substitution,
Y is oxygen or sulphur,
X is OH, SH, COOH, COOR
5
, NH
2
, NHR
6
, NR
6
R
7
or CN,
where R
5
to R
7
, independently of one another, are as defined for R
1
to R
4
, and
n is 0, 1 or 2, and
aryl phosphates type II of the general formula (II)
where
R
8
to R
15
, independently of one another, are hydrogen, alkyl, cycloalkyl, alkenyl, aralkyl or aryl, where the aryl moiety may be unsubstituted or have alkyl substitution,
m is 0, 1, 2 or 3 and
A is aromatics which contain at least two functional groups.
DETAILED DESCRIPTION OF THE INVENTION
Particular alkyl radicals R
1
to R
4
which may be used for the aryl phosphates type I are those having from 1 to 20 carbon atoms, preferably from 1 to 6 carbon atoms, particularly preferably from 1 to 4 carbon atoms. The cycloalkyl radicals preferably have from 5 to 8 ring carbon atoms, in particular 5 or 6 ring carbon atoms, and the alkenyl radical may be linear or branched and contain from 2 to 12 carbon atoms, preferably from 2 to 6 carbon atoms. Preferred aralkyl groups are those containing from 7 to 12 carbon atoms. Preferred aryl radicals used are those with substitution by C
1
-C
4
-alkyl radicals and having from 6 to 14 ring carbon atoms. The aryl radicals may also be unsubstituted.
Examples of the radicals R
1
to R
4
of the aryl phosphates type I are: methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, hexyl, octyl, dodecyl, tetradecyl, eicosyl, cyclopentyl, cyclohexyl, methylcyclohexyl, vinyl, prop-1-enyl, prop-2-enyl, n-but-3-enyl, n-pent-4-enyl, n-hex-5-enyl, phenyl, naphthyl, biphenyl, benzyl, methylbenzyl, phenylethyl.
The use of these aryl phosphates of type I is particularly preferred when X is NH
2
, the radicals R
1
to R
4
are hydrogen and n is 0, 1 or 2.
Particular alkyl radicals R
8
to R
15
which may be used for the aryl phosphates type II are those having from 1 to 20 carbon atoms, preferably from 1 to 6 carbon atoms, particularly preferably from 1 to 4 carbon atoms. The cycloalkyl radicals preferably have from 5 to 8 ring carbon atoms, in particular 5 or 6 ring carbon atoms, and the alkenyl radical may be linear or branched and contain from 2 to 12 carbon atoms, preferably from 2 to 6 carbon atoms. Preferred aralkyl groups are those containing from 7 to 12 carbon atoms. Preferred aryl radicals used are those with substitution by C
1
-C
4
-alkyl radicals and having from 6 to 14 ring carbon atoms. The aryl radicals may also be unsubstituted.
Examples of the radicals R
8
to R
15
of the above formula are: methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, hexyl, octyl, dodecyl, tetradecyl, eicosyl, cyclopentyl, cyclohexyl, methylcyclohexyl, vinyl, prop-1-enyl, prop-2-enyl, n-but-3-enyl, n-pent-4-enyl, n-hex-5-enyl, phenyl, naphthyl, biphenyl, benzyl, methylbenzyl, phenylethyl.
The aryl phosphates type II may be unbridged, and here m is preferably 0. The aryl phosphates type II are preferably bridged, m being 1, 2 or 3. Examples of unbridged aryl phosphates type II are triphenyl phosphate and alkylphenyl phosphates.
As A, preference is given to a radical which in the form of A(OH)
2
is the compound bisphenol A or resorcinol.
Very particular preference is given to aryl phosphates type II in which R
8
to R
15
are methyl and A is a radical which in the form of A(OH)
2
is bisphenol A.
Some of the compounds are known or may be prepared by known methods. One way of preparing the aryl phosphates type I is transesterification of an appropriate triaryl phosphate with the appropriate phenols in a suitable molar ratio with basic catalysis (Houben-Weyl, Methoden der organischen Chemie [Methods of organic chemistry], Volume 12/2, pp. 371 et seq., Georg Thieme Verlag, Stuttgart, 1964).
Some of the aryl phosphates type II, e.g. diphenyl cresyl phosphate or bisphenol A bis(diphenyl) phosphate, are commercially available products with the trade names Disflamoll DPK® and Fyrolflex BDP®, respectively, from Bayer or Akzo. Bridged phosphates, e.g. dixylenyl bisphenol A diphosphate (hereinafter “bisphenol A bis(dixylenylphosphate)”), may be prepared by bridging of POCl
3
with multi-functional aromatics and reaction
Janke Nikolaus
Mauerer Otto
Pieroth Manfred
Akorli Godfried R.
Bayer Chemicals AG
Szekely Peter
vanEyl Diderico
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