Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1997-04-28
2001-04-10
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S169000, C526S169200, C526S177000, C526S185000, C526S281000, C526S308000, C526S348000
Reexamination Certificate
active
06214951
ABSTRACT:
The invention relates to thermoplastic cycloolefin copolymers (COCs) having high tear strength and low optical attenuation, to a process for their preparation, and to their use as optical waveguides (optical fibers).
Optical waveguides are employed for the transport of light, for example for the purpose of illumination or signal transmission. They generally comprise a cylindrical, light-transmitting core surrounded by a cladding layer of a likewise transparent material with a lower refractive index. Thin-film optical waveguides comprise, for example, three transparent layers, where the two outer layers have lower refrfactive index than the central layer. The conduction of light takes place by total reflection at the inteface. Transparent materials which can be employed are glasses or (organic or inorganic) polymers.
The most widespread polymer for use as an optical waveguide, polymethyl methacrylate (PMMA), can only be employed at up to about 85° C. due to its low glass transition temperature of about 106° C. Other known transparent thermoplastics having higher glass transition temperatures, such as, for example, polycarbonate or aromatic polyesters, contain aromatic units in the molecule. These result in increased light absorption in the short-wave spectral region. The use of such polymers for optical waveguides is described in illustrative terms in A. Tanaka et al., SPIE, Vol. 840 (1987).
The heat distortion resistance can be improved by reaction of polymethacrylates. An example which may be mentioned is the polymer-analogous conversion of polymethyl methacrylate into polymethacrylimide. The copolymerization of poly(meth)acrylate with comonomers such as methacrylic anhydride or methacrylonitrile also gives polymers of higher heat resistance than unmodified PMMA. Another route to transparent polymers having increased glass transition temperatures is the use of (meth)acrylates of (per)halogenated or polycyclic aliphatic alcohols or of susbstituted phenols. The latter likewise have increased light absorption in the short-wave spectral region due to the aromatic units. Although the former compounds give transparent polymers having high glass transition temperatures, conversion, for example, into optical fibers is difficult or impossible due to their inherent brittleness.
All the classes of substances described are hygroscopic due to their polar nature. At elevated temperature, the water content in the polymer can cause undesired degradation reactions during conversion, reducing the practical use value.
However, lower water absorption is exhibited by thermoplastic COCs, which also have increased heat distortion resistance. The complete absence of chromophores, such as double bonds of all types, means that these polymers appear particularly suitable for optical applications. It should also be possible to employ these plastics in the area of light conduction (EP-A 0 355 682 and EP-A 0 485 893).
A particularly economical process is described in European Patent Application EP-A 0 485 893, which describes highly reactive metallocenes which polymerize cycloolefins, in particular readily accessible norbornene, to give copolymers having a high glass transition temperature. However, experiments have shown that these copolymers are relatively brittle. Although it is known that the tear strength of a polymeric fiber can be improved by orientation, processability is poor if the polymer becomes brittle immediately below the glass transition temperature, as is the case for the polymers described in EP-A 0 485 893.
COCs can be prepared using specific Ziegler catalysts (EP-A 0 355 682 and EP-A 0 485 893), usually using alkylaluminum or alkylaluminum chlorides as cocatalysts. However, these compounds hydrolyze during the work-up process described to give extremely fine, gelatinous compounds which are difficult to filter. If alkylaluminum chlorides are employed, chlorine-containing compounds, such as hydrochloric acid or salts, which are likewise difficult to separate off, are formed during work-up. If hydrochloric acid is employed for the work-up (EP-A 0 355 682 and EP-A 0 485 893), similar problems arise. In particular in the processing of COCs prepared in this way, a brown coloration occurs. However, in addition to a sufficiently high tear strength, a further important prerequisite for the use of a polymer for the production of a polymeric optical fiber or optical waveguide is excellent transparency.
The object of the invention was to develop a process for the preparation of COCs which are distinguished by improved tear strength, lower optical attenuation, increased glass transition temperature and low water absorption compared with the prior art. A further object was to produce an optical waveguide whose core material comprises this COC.
It has now been found that copolymerization of lower alpha-olefins, cyclic olefins and/or polycyclic olefins using a catalyst system comprising at least one metallocene catalyst and at least one cocatalyst allows the preparation of COCs having a high tear strength of 560-100 mPa, preferably 55-90 mPa, particularly preferably 58-85 mPa, if metallocene catalysts of certain symmetries are employed. (The tear strength increases with increasing molecular weight). If the reaction mixture formed after the copolymerization is subjected to a specific work-up process, optical waveguides having a low optical attenuation of 0.1-5 dB/m, preferably 0.2-2 dB/km and particularly preferably 0.3-1.5 dB/m, can be prepared from the purified COC and a transparent polymer whose refractive index is lower than the refractive index of the COC.
The invention thus relates to a process for the preparation of COCs having high tear strength by polymerization of 0.1 to 99.9% by weight, based on the total amount of the monomers, of at least one monomer of the formula I, II, III or IV
in which R
1
, R
2
, R
3
, R
4
, R
5
, R
6
, R
7
and R
8
are identical or different and are a hydrogen atom or a C
1
-C
8
-alkyl radical or a C
6
-C
16
-aryl radical, where identical radicals in the various formulae can have different meanings,
from 0 to 99.9% by weight, based on the total amount of the monomers, of a cycloolefin of the formula V
in which n is a number from 2 to 10, and
from 0.1 to 99.9% by weight, based on the total amount of the monomers, of at least one acyclic 1-olefin of the formula VI
in which R
9
, R
10
, R
11
and R
12
are identical or different and are a hydrogen atom or a C
1
-C
8
-alkyl radical or a C
6
-C
16
-aryl radical, in solution, in suspension, in a liquid cycloolefin monomer, or cycloolefin monomer mixture or in the gas phase, at a temperature of from −78 to 150° C., at a pressure of from 0.5 to 64 bar, in the presence of a catalyst comprising a metallocene as transition-metal component and an aluminoxane of the formula VII
for the linear type and/or of the formula VIII
for the cyclic type, where, in the formulae VII and VIII, R
13
is a C
1
-C
6
-alkyl group or phenyl or benzyl, and n is an integer from 2 to 50, where the polymerization is carried out in the presence of a catalyst whose transition-metal component is at least one compound of the formula IX
in which
M
1
is titanium, zirconium, hafnium, vanadium, niobium or tantalum,
R
14
and R
15
are identical or different and are a hydrogen atom, a halogen atom, a C
1
-C
10
-alkyl group, a C
1
-C
10
-alkoxy group, a C
6
-C
10
-aryl group, a C
6
-C
10
-aryloxy group, a C
2
-C
10
-alkenyl group, a C
7
-C
40
-arylalkyl group, a C
7
-C
40
-alkylaryl group or a C
8
-C
40
-arylalkenyl group,
m may be one or two, depending on the valency of the central atom M
1
,
R
18
is
═BR
19
, ═AIR
19
, —Ge—, —Sn—, —O—, —S—, ═SO, ═SO
2
, ═NR
19
, ═CO, ═PR
19
or ═P(O)R
19
, where R
19
, R
20
and R
21
are identical or different and are a hydrogen atom, a halogen atom, a C
1
-C
10
-alkyl group, a C
1
-C
10
-fluoroalkyl group, a C
6
-C
10
-fluoroaryl group, a C
6
-C
10
-aryl group, a C
1
-C
10
-alkoxy group, a C
2
-C
10
-alkenyl group, a C
7
-C
40
-arylalkyl group, a C
8
-C
40
Brekner Michael-Joachim
Deckers Hellmuth
Osan Frank
Frommer & Lawrence & Haug LLP
Hoechst Aktiengesellschaft
Zitomer Fred
LandOfFree
Cycloolefin copolymers having high tear strength and low... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cycloolefin copolymers having high tear strength and low..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cycloolefin copolymers having high tear strength and low... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2438534