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
1998-11-30
2003-09-02
Egwim, Kelechi (Department: 1713)
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...
C523S200000, C523S213000, C523S214000, C524S081000, C524S262000, C524S264000, C524S265000, C524S442000, C524S451000
Reexamination Certificate
active
06613825
ABSTRACT:
The present invention relates to thermoplastic compositions based on syndiotactic polymers of styrene, reinforced with inorganic and/or organic rigid fillers.
More specifically this composition comprises:
a) 100-80% by weight of a crystalline syndiotactic polymer of styrene;
b) 0-20% by weight of a polyarylene-ether;
c) 1-200 parts by weight, with respect to 100 parts of (a)+(b), of one or more inorganic and/or organic rigid fillers;
d) 0.01-5 parts by weight, with respect to 100 parts of (a)+(b), of a silanic compound having general formula (I):
wherein
R and R
1
are, independently, hydrogen or an alkyl radical containing from 1 to 8 carbon atoms;
R
2
is a hydrolyzable alkoxyl group containing from 1 to 6 carbon atoms or a halogen atom;
R
3
is an alkyl radical containing from 1 to 8 carbon atoms;
X is either a radical having the formula
or an aromatic or cycloaliphatic or heterocyclic radical, wherein R
4
is hydrogen or an alkyl radical containing from 1 to 18 carbon atoms and n is an integer between 1 and 4;
m is an integer between 1 and 3.
The compositions claimed have improved thermal properties, creep resistance and impact strength with a consequent increase in rigidity and shock-resistance properties and they can be used for applications in the field of household appliances and in the electronic and car industries.
It is known that styrene polymers have a good rigidity but poor resistance to solvents, heat and impact; the discovery of new catalysts has recently allowed the synthesis of polystyrenes with a high degree of syndiotaxy, which are crystalline rather than amorphous, very rigid and with a high melting point.
Owing to the different molecular conformation, these new polystyrenes have reasonable resistance to heat and solvents but retain the fragility of the atactic polymer.
In an attempt to improve both resistance to creep deformation (induced by a constant loading, generally at high temperatures) and impact, efforts have been made to reinforce the new polymer with inorganic fibres.
As, to obtain this result, it is necessary to have good adhesion between the fibre and polymeric matrix, research has been directed towards determining under what conditions this can be achieved.
In this respect, the U.S. document U.S. Pat. No. 5,426,171 (Huang et al.) describes the use of small amounts of polyphenylene-ethers grafted with maleic anhydride (PPO-g-MAH) associated with a silane, both operating on the polymer and sizing the glass fibre.
U.S. Pat. No. 5,270,353 (Nakano et al.), on the other hand, claims a composition comprising a styrene polymer having a syndiotactic configuration, a styrene polymer modified with epoxy groups and a sized inorganic filler, to favour compatibilization between the components.
In U.S. Pat. No. 5,395,890 (Nakano et al.), a rubber and/or inorganic filler is added to the styrene polymer/thermoplastic resin (generally PET) mixture to improve the heat resistance and impact strength.
The patent EP 0 314 146 (Albizzati et al.), on the other hand, relates to a composition based on syndiotactic styrene polymers and polyphenylene-ethers (PPO) which, also in this case, has improved mechanical properties compared with compositions containing amorphous or isotactic polystyrene.
U.S. Pat. No. 5,412,024 (Okada et al.) describes thermo plastic compositions which comprise syndiotactic polymers whose modified end-group is bound to compounds having polar groups in the presence of an inorganic filler.
U.S. Pat. No. 5,436,397 (Okada et al.) describes a composition with improved mechanical properties comprising a polystyrene resin as such and modified, an elastomeric compound and an inorganic filler.
In conclusion, all the compositions claimed, either limit themselves to facing the problem of impact strength by using rubbers (which however reduce the rigidity and heat resistance) or try to solve the problem of adhesion matrix/filler by both modifying the polymer by the introduction of particular reactive groups, and covering the filler with substances which favour adhesion; in all cases however, the process is complicated and incomplete.
On the other hand, there are also documents that describe the use of compatibilizing compounds applied to polypropylene reinforced with mica (EP 0 69 937—Moro et al.) or, more generally, to reinforced polyolefins (EP 0 370 551—Joslyn et al.).
The Applicant has now overcome the above drawbacks by preparing a mixture in a single phase, which comprises syndiotactic styrene polymer to which small amounts of a polyarylate, a rigid filler and a particular compatibilizing compound are generally added, without the necessity, therefore, of preparing the polymeric matrix for adhesion with the filler by means of particular pretreatment processes.
The present invention consequently relates to thermoplastic compositions based on syndiotactic polymers of styrene, reinforced with inorganic and/or organic rigid fillers.
More specifically this composition comprises:
a) 100-80% by weight of a crystalline syndiotactic polymer of styrene;
b) 0-20% by weight of a polyarylene-ether;
c) 1-200 parts by weight, with respect to 100 parts of (a)+(b), of one or more inorganic and/or organic rigid fillers;
d) 0.01-5 parts by weight, with respect to 100 parts of (a)+(b), of a silanic compound having general formula (I):
wherein
R and R
1
are, independently, hydrogen or an alkyl radical containing from 1 to 8 carbon atoms;
R
2
is a hydrolyzable alkoxyl group containing from 1 to 6 carbon atoms or a halogen atom;
R
3
is an alkyl radical containing from 1 to 8 carbon atoms;
X is either a radical having the formula
or an aromatic or cycloaliphatic or heterocyclic radical, wherein R
4
is hydrogen or an alkyl radical containing from 1 to 18 carbon atoms and n is an integer between 1 and 4;
m is an integer between 1 and 3.
A preferred form of this composition is the following:
a) 100-95% by weight of a crystalline syndiotactic polymer of styrene;
b) 0-5% by weight of a polyarylene-ether;
c) 10-70 parts by weight, with respect to 100 parts of (a)+(b), of one or more inorganic and/or organic rigid fillers;
d) 0.1-3 parts by weight, with respect to 100 parts of (a)+(b), of a compound having general formula (I), described above.
Component (a) is given by a styrene homo- or co-polymer with a prevalently syndiotactic configuration; this means that the stereostructure of the polymer has phenyl or phenyl-substituted side groups situated alternately in opposite directions with respect to the main chain represented according to a Fisher projection.
The preparation of these polymers can be carried out, according to what is known in the art, in bulk, solution or suspension, at temperatures generally ranging from −50 to 120° C. and pressures generally ranging between 0.1 and 5 atmospheres, using catalytic systems containing as main components a titanium complex (for example TiX
4
, CpTiX
3
, Cp*TiX
3
, with Cp=cyclopentadienyl, Cp*=pentamethylcyclopentadienyl, X=alkyl, alkoxide, halogen, carboxylate, dialkylamine, etc., and the various X can also be different from each other) and a co-catalyst selected from an alkylaluminoxane (preferably methylaluminoxane) or a derivative of tris(pentafluorophenyl)boron.
The catalytic system may optionally also contain other activator components such as aluminum alkyls or tin alkyls, etc. (see, for example, EP 0 780 405).
The degree of taxis can be quantitatively determined by means of NMR (Nuclear Magnetic Resonance) of carbon 13 according to the method described in U.S. Pat. No. 4,680,353.
The styrene polymers with a prevalently syndio-tactic configuration mentioned in this composition comprise, among others, homo- and co-polymers containing styrene, ortho-, meta- and para-substituted alkylstyrenes, ortho-, meta- and para-substituted halogen alkylstyrenes (or mixtures of these two polymers), with a degree of syndiotaxy, measured according to the method indicated, which is such that the proportion of racemic dyads is at least 75% or preferably higher than 85%
Franco Raffaele
Moro Alessandro
Po′ Riccardo
Scapin Marco
Egwim Kelechi
Enichem S.p.A.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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