Note: Descriptions are shown in the official language in which they were submitted.
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A vinylcyclo6exane-Eased nolymer
The present invention relates to vinylcyclohexane (VCH)-based polymers and
copolymers which have a predominantly isotactic configuration, to a process
for the
production thereof, and to the use thereof as an optical material. The
materials can be
processed by extrusion or injection moulding and are particularly suitable as
a
substrate for optical materials, prisms, lenses and compact discs.
Transparent plastics such as aromatic polycarbonates, polymethyl rnethacrylate
or
polystyrene can be used as a substrate for optical materials. Addition
copolymers
formed from ethylene and a norbornene derivative or a tetracyclododecene
derivative,
as well as hydrogenated products of ring-opened methathesis polymers of
norbornene
or tetracyclododecene, are also suitable for this purpose.
Optical materials comprising a hydrogenation product of a polymer of an
aromatic
alkenyl hydrocarbon compound or a copolymer thereof are described in GB
933,596
(= DE-AS 1 131 885), EP-A 317 263, US 4,911,966 and US 5,178,926. There is no
mention of their configuration.
The hydrogenation of polystyrene was first described by Hermann Staudinger in
1929.
More recent patent literature is concerned with the underlying microstructure
of
polyvinylcyclohexane or hydrogenated polystyrene. The current state of
knowledge is
that amorphous vinylcyclohexane polymers possess an atactic configuration and
crystalline VCH (vinylcyclohexane) polymers possess either an isotactic or a
syndiotactic configuration (EP-A 0 322 731, EP-A 0 423 100, US-A 5,654,253; US-
A 5,612,422, WO 96/34896). Isotactic PVCH (polyvinylcyclohexane) is produced
in
the presence of Ziegler catalysts, and has a high melting point (J. Polym.
Sci., A2,
5029 (1964)). EP-A 0 322 731 states that vinylcyclohexane polymers with a
syndiotactic configuration and which are produced by the hydrogenation of
syndiotactic polystyrene are crystalline, wherein the amount of dyads is at
least 75
and the amount of pentads is at least 30 %. WO 94/21694 describes a process
for the
production of hydrogenated aromatic polyalkykenyl polymers and aromatic
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polyalkenylpolydiene block polymers. Syndiotactic polystyrene is mentioned in
a
general sense.
Processes which result in isotactic, syndiotactic and atactic hydrogenated
polystyrene
which exhibits the material properties which were known previously are
described in
WO 94/21694 and in US-A 5,352,744, wherein special catalysts are used.
Processes
for the hydrogenation of atactic polystyrene to form atactic hydrogenated
polystyrene
using special catalysts are described in US-A 5,654,253, US-A 5,612,422 and WO
96/34896.
Atactic polymers are regular polymers. According to their definition, they
possess the
possible configurative basic components in equal amounts, with an ideal random
distribution from molecule to molecule (ILJPAC). They are distinguished by the
same
number of iso- and syndiotactic dyads. They are described as an amorphous
material
with only one glass phase and without a crystalline constituent.
The present invention relates to a vinylcyclohexane-based polymer or copolymer
which has an isotactic configuration, wherein olefines, alkyl esters of
acrylic acid
derivatives, malefic acid derivatives, vinyl ethers or vinyl esters can be
used for the
production thereof, characterised in that the amount of dyads is greater than
50.1
and less than 74 %, and is most preferably 51-70 %. These vinylcyclohexane-
based
polymers are amorphous polymers.
The polymers according to the invention are distinguished by their high
transparency,
low extent of birefringence and high dimensional stability when hot, and can
therefore
be used as a substrate material for optical data storage media. The known
isotactic
PVCH, which is produced using Ziegler Natta catalysts and which comprises a
proportion of isotactic dyads >75%, is unsuitable for optical applications due
to its
crystallinity (J. Polymer Sci, A2, 5029 (1964)).
The present invention relates to hydrogenated products of polystyrene, which
result in
an amorphous hydrogenated polystyrene comprising an excess of isotactic dyads.
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The vinylcyclohexane polymer of this invention is a new amorphous polymer with
a
defined stereostructure, which is distinguished by the predominant occurrence
of an
isotactic dyad configuration and which can be produced by the process
described.
The preferred vinylcyclohexane-based polymer comprises a recurring structural
unit of
formula (I)
R' R5
RZ (1)
R3 R4
wherein
R~ and R2, independently of each other, represent hydrogen or a C,-C6 alkyl,
preferably a C 1-C4 alkyl, and
R3 and R4, independently of each other, represent hydrogen or a C~-C6 alkyl,
I 5 preferably a C,-C4 alkyl, particularly methyl and/or ethyl, or R3 and R4
jointly
represent an alkylene, preferably a C3 or C4 alkylene (a condensed-on 5- or 6-
membered cycloaliphatic ring),
RS represents hydrogen or a C,-C6 alkyl, preferably a C~-C4 alkyl, and
R~, R2 and R5, independently of each other, represent hydrogen or methyl in
particular.
Apart from the stereoregular head-to-tail linkage, the linkage may comprise a
small
proportion of head-to-head linkages. The vinylcyclohexane-based, amorphous,
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predominantly isotactic polymer may be branched via branching centres and may
have
a star-shaped structure, for example.
The following can be used as comonomers during the polymerisation of the
initial
polymer (polystyrene which is optionally substituted) and can be incorporated
in
conjunction into the polymer: olefines which generally comprise 2 to 10 C
atoms,
such as ethylene, propylene, isoprene, isobutylene or butadiene, C~ -Cg,
preferably C,-
C4 alkyl esters of acrylic or methacrylic acid, unsaturated cycloaliphatic
hydrocarbons,
e.g. cyclopentadiene, cyclohexene, cyclohexadiene, norbornene which is
optionally
substituted, dicyclopentadiene, dihydrocyclopentadiene, tetracyclodecenes
which are
optionally substituted, styrenes comprising alkylated nuclei, a-methylstyrene,
divinyl-
benzene, vinyl esters, vinylic acids, vinyl ethers, vinyl acetate, vinyl
cyanides such as
acrylonitrile, methacrylonitrile and malefic anhydride for example, and
mixtures of
these monomers. In general, up to 60 % by weight, preferably up to 50 % by
weight,
most preferably up to 40 % by weight (with respect to the polymer) of
comonomers
can be contained. Vinylcyclohexane polymers I which contain up to 30 % by
weight
of comonomers are most particularly preferred.
The amorphous vinylcyclohexane polymer according to the invention has a
content of
isotactic dyads, as determined by two-dimensional NMR spectrometry, of 50.1 to
74
%, preferably of 51 - 70 %. Methods of elucidating the microstructure by means
of
'3C-'H correlation spectroscopy of the methylene carbon atoms of a polymer
backbone are generally known and are described by A.M.P. Ros and O. Sudmeijer
(A.M.P. Ros, O. Sudmeijer, Int. J. Polym. Anal. Charakt. (1997), 4, 39).
The signals of crystalline isotactic and syndiotactic polyvinylcyclohexane are
determined by means of two-dimensional NMR spectrometry. The methylene carbon
atom (in the polymer backbone) of isotactic polyvinylcyclohexane splits into 2
separate proton signals in the 2 D-CH correlation spectrum, and indicates a
pure
isotactic dyad configuration. In contrast, isotactic polyvinylcyclohexane only
exhibits
one signal for the C 1 carbon atom in the 2 D-CH correlation spectrum.
Amorphous,
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isotactic-enriched polyvinylcyclohexane exhibits an excess of integral signal
intensity
for isotactic dyads compared with a syndiotactic dyad configuration.
The last-mentioned substance exhibits a high degree of dimensional stability
when hot
and a low water absorption, whilst possessing satisfactory mechanical
properties, and
is therefore an ideal material for optical applications.
The vinylcyclohexane (co)polymers generally have absolute weight average
molecular
weights Mw > 1000, preferably from 1500 - 400,000, most preferably from 1500 -
3 80,000, as determined by light scattering.
Vinylcyclohexane (co)polymers of low molecular weight which are particularly
preferred are those which have absolute (weight average) molecular weights
from
1500 to 20,000.
In general, the vinylcyclohexane-based homopolyrners according to the
invention have
a glass transition temperature >90°C, preferably >95°C, as
determined by DSC.
The copolymers can exist either as random copolymers or as block copolymers.
The polymers can have a linear chain structure or can have branching locations
due to
co-units (e.g. graft copolymers). The branching centres may comprise star-
shaped or
branched polymers, for example. The polymers according to the invention may
comprise other geometric forms of the primary, secondary, tertiary or
optionally of the
quaternary polymer structure Examples thereof include a helix, a double helix,
a
folded lamella, etc., or mixtures of these structures.
Block copolymers comprise di-blocks, tri-blocks, mufti-blocks and star-shaped
block
copolymers.
The VCH (co)polymers are produced by the polymerisation of derivatives of
styrene
with the corresponding monomers, by a radical, anionic or cationic mechanism
or by
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metal complex initiators or by catalysts, and by subsequent complete or
partial
hydrogenation of the unsaturated aromatic bonds (see WO 94/02720 and EP-A 322
731 for example). They are distinguished by the predominant occurrence of the
isvtactic configuration of the vinylcyclohexane units of the present
invention.
In general, this process results in what is practically the complete
hydrogenation of the
aromatic units. As a rule, the degree of hydrogenation is >_ 80 %, preferably
>_ 90 %,
most preferably >_ 99 % to 100 %. The degree of hydrogenation can be
determined by
NMR spectrometry or UV spectroscopy, for example.
The initial polymers which are used are generally known (e.g. WO 94/21 694).
The amount of catalyst to be used is described in WO 96/34896, for example.
I 5 The amount of catalyst used depends on the process which is carried out.
This process
can be conducted continuously, semi-continuously or batch-wise.
In a continuous system, the time of reaction is considerably shorter: it is
influenced by
the dimensions of the reaction vessel. In a continuous procedure, it is
possible to use a
trickling system or a liquid pool system, which both employ fixed catalysts,
and it is
also possible to use a system comprising a suspended catalyst, which can be
recycled
for example. Fixed catalysts can exist in the form of tablets or as an
extruded product,
for example.
The polymer concentrations with respect to the total weight of solvent and
polymer
generally range from 80 to I, preferably from 50 to 10, particularly from 40
to 15
by weight.
Hydrogenation of the initial polymers is effected by methods which are
generally
known (e.g. WO 94/21 694, WO 96/34895, EP-A-322 731). There is a multiplicity
of
known hydrogenation catalysts which can be used as catalysts. The preferred
metal
catalysts are cited in WO 94/21 694 or in WO 96/34 896, for example. Any
catalyst
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which is known for hydrogenation reactions can be used as a catalyst.
Catalysts having
a large specific surface (e.g. 100 - 600 m2/g) and a small average pore
diameter (e.g.
20 - 500 t~) are suitable. Other suitable catalysts include catalysts which
have a small
specific surface (e.g. ? 10 m2/g) and a large average pore diameter, and which
are
characterised in 98 % of the pore volume comprises pores with a pore diameter
larger
than 600 A (e.g. about 1000 - 4000 ~) (see US-A 5,654,253, US-A 5,612,422, JP-
A
03076706 for example). Raney nickel, nickel on silica or on silica/alumina, or
nickel
on carbon as a support, and/or noble metal catalysts on silica, silica/alumina
and
alumina, especially Pt, Ru, Rb or Pd, are used in particular.
The reaction is generally conducted at temperatures between 0 and
500°C, preferably
between 20 and 250°C, particularly between 60 and 200°C.
The solvents which are customary for hydrogenation reactions are described in
DE-AS
1 131 885 for example (see above).
The reaction is generally conducted at pressures from 1 bar to 1000 bar,
preferably
from 20 to 300 bar, particularly from 40 to 200 bar.
The polymers or copolymers which are based on vinylcyclohexane according to
the
invention are outstandingly suitable for the production of optical materials,
e.g. lenses,
prisms and optical discs.
Examples of optical data storage media include:
- the magneto-optical disc (MO disc)
- the mini-disc (MD)
- the ASMO (MO-7) ("advanced storage magnetooptic")
- the DVR (12 Gbyte disc)
- the MAMMOS ("magnetic amplifying magneto optical system")
- . the SIL and MSR ("solid immersion lens" and "magnetic superresolution")
- the CD-ROM (read only memory)
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_g_
- the CD, the CD-R (recordable), the CD-RW (rewritable), the CD-I
(interactive), and the photo-CD
- the super audio CD
- the DVD, the DVD-R (recordable), the DVD-RAM (random access memory)
- the DVD=digital versatile disc
- the DVD-RW (rewritable)
- the PC RW (phase change and rewritable)
the MMVF (multimedia video file system)
Moreover, due to their outstanding optical properties, the polymers according
to the
invention are particularly suitable for the production of optical materials,
e.g: for
lenses, prisms, mirrors, colour filters, etc., and are also suitable as media
for
holographic imaging (e.g. cheques, credit cards, passes, three-dimensional
holographic images). The materials can be used as transparent media for
inscribing
three-dimensional structures, e.g. from focused coherent radiation (LASERS),
and can
be used in particular as three-dimensional data storage media for the three-
dimensional imaging of objects.
The material can usually be employed instead of or in combination with glass
up to
temperatures of use of 145°C. External applications for the transparent
materials
include roof claddings, window panes, sheeting, and for the glazing of
greenhouses, e.g.
in the form of double-ribbed panels. Other applications include coverings,
which at the
same time exhibit a high level of transparency, for the protection of
mechanically
sensitive systems, e.g. in the photovoltaic sphere, particularly solar cells
or solar
collectors. The plastics according to the invention can be coated with other
materials,
and in particular can be coated with nanoparticles in order to increase their
scratch-
resistance, or with metals or other polymers.
Examples of domestic applications include transparent packaging materials
which
exhibit a low permeability to moisture, domestic articles which are produced
by
extrusion or injection moulding, e.g. tumblers and containers, and also
domestic
appliances and transparent lamp covers.
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The plastics can be used as temperature-resistant rigid foams for insulation
in the
building and engineering sectors (house and appliance insulation, e.g. for
refrigerators),
and can replace polystyrene or polyurethane foam for example. One advantage is
the
high temperature of continued use of these materials.
Due to their low density (d<I) and the saving in weight which results
therefrom, the
materials are particularly suitable for applications in the automobile,
aviation and space
travel industries, e.g. for instrument panels and transparent coverings for
instrument
systems, and also for light sources, for vehicle glazing and as an insulation
material.
The materials are insulators for electric current and are therefore suitable
for the
production of capacitors (e.g. dielectrics), electronic switching circuits and
appliance
housings. There are other applications in the electronics industry,
particularly on account
I S of the combination of a high level of optical transparency with a high
level of
dimensional stability when hot, and low water absorption in association with
light from
suitable emitting sources. The materials are therefore suitable for the
production of light-
emitting diodes, laser diodes, matrices for organic, inorganic and polymeric
electroluminescent materials, opto-electric signal recording devices, the
replacement of
glass fibres in data transmission systems (e.g. polymeric wave guides), and
transparent
materials for electronic display media (screens, displays, projection
apparatuses) e.g.
those comprising liquid crystalline substrates.
The materials are suitable for applications in medical technology, e.g. for
transparent
extruded or injection moulded articles for sterile and non-sterile analysis
vessels, Petri
dishes, microfilter plates, object supports, flexible tubing, breathing tubes,
contact
lenses, spectacles and containers, e.g. for infusion solutions or solutions of
medicaments, extruded and injection moulded articles for applications in
contact with
blood, particularly for the production of syringes, cannulas, catheters, short-
and long-
term implants (e.g. artificial lenses), blood tubing, membranes for the
washing of blood,
dialysers, oxygenators, transparent wound dressings, blood bottles and
stitching
materials.
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Examples
Example 1
An autoclave was flushed with inert gas (argon). The polymer solution and the
catalyst were added (Table 1). After closing the autoclave, it was repeatedly
pressurised with a protective gas and then with hydrogen. After releasing the
pressure,
the respective hydrogen pressure was set and the batch was heated with
stirring to the
corresponding reaction temperature. After the consumption of hydrogen had
commenced, the reaction pressure was held constant.
After the reaction was complete, the polymer solution was filtered. The
product was
precipitated in methanol and dried at 120°C. The isolated product had
the physical
properties listed in Table 2.
Comparative example A
Syndiotactic polyvinylcyclohexane
A baked-out 250 ml three-necked flask, which was fitted with a reflux
condenser and
which was maintained under argon, was charged with 50 ml abs. toluene, 20 ml
methylaluminoxane (10% solution in toluene), 16.5 mg (0.075 mmol) titanium
cyclopentadienyltrichloride and 10.4 g (0.1 mol) styrene, in this sequence..
The
reaction mixture was heated to 50°C and was maintained for 2 hours at
this
temperature. The reaction was stopped by adding acidic methanol. The polymer
was
repeatedly washed with 200 ml methanol and was dried at 80°C.
12.5 g palladium on barium sulphate were reduced with hydrogen and were
rendered
inert by a protective gas. A 1 litre pressurised reactor was flushed with
inert gas. 2.5 g
syndiotactic polystyrene dissolved in cyclohexane were introduced into the
autoclave
together with the catalyst (Table 1). The hydrogen pressure was adjusted to 50
bar and
the batch was heated to 200°C. After 24 hours the reaction was stopped,
the autoclave
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was depressurised and the polymer solution was filtered. The filtrate was
precipitated
in methanol and the product was dried under vacuum at 120°C. The
isolated product
had the physical properties listed in Table 2.
Comparative example B
Isotactic polyvinylcyclohexane
100 ml abs. toluene, 12.5 g (0.11 mol) vinylcyclohexane and S mmol
triethylaluminium were introduced at room temperature into a baked-out 1 litre
three-
necked flask fitted with a reflux condenser.
1 ml triethylaluminium (1 M) and 2 ml titanium(IV) chloride (1 M) in 12.5 ml
toluene
were stirred for 30 minutes at 80°C and were added to the monomer
solution.
IS
The reaction mixture was heated to 60°C, was stirred for 50 minutes
at this
temperature and was subsequently held at 85°C for 90 minutes.
Polymerisation was
stopped by adding methanol. The product was boiled in methanol under reflux,
filtered off, and was subsequently washed with methanol and acetone. The
polymer
was dried under vacuum at 60°C. The product had the physical properties
listed in
Table 2.
Comparative example C
Polycarbonate from 2,2-bis(4-hydroxyphenyl)propane
A film of polycarbonate, 150 ~m thick, based on 2,2-bis-(4-
hydroxyphenyl)propane
(Makrolon CD 2005, Bayer AG) was produced by a melt pressing process. A glass
transition temperature of 142°C and a rheooptical constant of +5.4 GPa
I were
measured for this film (see Table 2).
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Table 1
Hydrogenation of polystyrenes with different tacticity
Example WeightSolvent Weight ReactionHydrogenTime Degree
of of of
No. of catalysttemp. pressurereactionhydrogenation's
polymer ml g C bar hours
g
1 2.52 300 ml 12.53 200 50 6 100
cyclohexane
A 2.5 300 ml 12.5~ 200 85 24 100
cyclohexane
1) Determined by'H NMR spectrometry
2) Polystyrene standard, Mw = 2500, Aldrich
3) Ni /Si02/A120~, 64-67 % nickel, Aldrich
4) 5 % palladium on barium sulphate, Aldrich
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Table 2
Thermal and optical properties of different vinylcyclohexane homopolymers
Example No. Isotactic dyadsz Syndiotactic Glass transition Melting pt. Tm
Transparency of
dyadsz temp. Tg °C solution films
°C +/-
1 55 45 98 - +
A < 2 > 98 126 295 -
B > 98 < 2 -'~ 369 -
C - - 142 - +
I ) not detected by DSC measurements
2) determined by two-dimensional nuclear magnetic resonance spectrometry (2D
NMR).
The amorphous polyvinylcyclohexane according to the invention (Example 1) is
distinguished by the predominant occurrence of isotactic dyads. Compared with
polycarbonate, the material also exhibits a high level of transparency and a
high level
of dimensional stability when hot (glass transition temperature). On account
of their
crystallinity and low transparency, the syndiotactic and isotactic materials
which have
been described hitherto are unsuitable for optical applications.
