AU606137B2 - Transparent thermoplastic molding composition - Google Patents

Description

S606137 Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-69 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: 'Complete Specification Lodged: Accepted: Published: Priority: 0 o This document contains the amendments made under Section 49 and is correct for printing.

Related Art Related Art: Name of Applicant: HOECHST AKTIENGESELLSCHAFT 0 i Address of Applicant a 4 SActual inventor: Address for Service: 45 Bruningstrasse, D6230 Frankfurt/Main Federal Republic of Germany GERHARD WIENERS, RUDOLF HEUMULLER, JOCHEN COUTANDIN, WERNER GROH and PETER HERBRECHTSMEIER EDWD. WATERS SONS, 50 QUEEN STREET, MELBOURNE, AUSTRALIA, 3000.

Complete Specification for the invention entitled: TRANSPARENT THERMOPLASTIC MOLDING COMPOSITION The following statement is a full description of this invention, including the best method of performing it known to US HOECHST AKTIENGESELLSCHAFT HOE 87/F 074 Dr.DA/je Description Transparent thermoplastic molding composition The invention relates to a transparent, thermoplastic molding composition which is suitable for the production of I polymeric glasses, articles for the optical industry and optical fibers for transmission of light signals, and to a I 'process for the production thereof. The molding compo- S 10 sition has a high thermal distortion resistance.

I Optical fibers can comprise a core and a sheath, the core Smaterial always having a higher refractive index than the sheath material. The core material and the sheath material of such an optical fiber should absorb as little light as possible.

SThe polymeric materials employed the most frequently hitherto for optical fibers are homopolymers and copolymers of methyl methacrylate. Whereas halogen-containing polymers have also been employed for the core, exclusively i fluorine-contaiining polymers have hitherto been used for the sheath since they have a lower refractive index. In Sorder to reduce light absorption, it has also already been proposed to replace the hydrogen atoms in the monomers and polymers by deuterium.

Copolymers of methyl methacrylate with a compound of the Sformula CH2=CR-(CO-O)n-ArBrm (R=H or CH 3 n zero or 1, and m 1 to 5) have been disclosed (cf. German Offenlegungsschrift 2,202,791). Acrylates and methacrylates of mono-, di-, tri-, tetra- and pentabromophenol have been mentioned by name.

Furthermore, a molding composition is known which comprises a polymeric a-fluoroacrylate which can contain deuterium atoms both on the 8-carbon atom of the vinyl 4 4i r fitt ft 4 o o i ao o i o o rn 0 0 2 group and in the alcohol component (European Application Publication 0,128,517). These polymers are used as core materials for optical fibers; they have a molecular weight of 200,000 to 5,000,000 (gel permeation), a refractive index of 1.45 to 1.60 and a softening point of 100 to 200 0 C. The sheath material used for the optical fibers are polymers which have a lower refractive index; suitable for this purpose are, inter alia, polymers of afluoroacrylates whose alcohol component contains fluorine atoms, for example trifluoroethyl a-fluoroacrylate and hexafluoroisobutyl a-fluoroacrylate.

The preparation and properties of the abovementioned poly- (fluoroalkyl a-fluoroacrylates) are Likewise known 15 (European Application Publication 0,128,516). The polymers are obtained by free-radical initiated bulk, solution or suspension polymerization of the monomers in the presence of a chain-transfer agent at a temperature of 0 to 1000C. The polymers have a molecular weight of 20 200,000 to 5,000,000 (gel permeation), a refractive index of 1.36 to 1.44 and a softening point of 80 to 140 0

C.

In addition, an optical fiber has been described whose core material is produced by block polymerization of, 25 inter alia, halogenated aryl methacrylates, for example pentafluorophenyl methacrylate (cf. Japanese Published Specification 60-242,404).

Furthermore, polyhalogenated aryl(fluoro/meth)acrylate- 30 containing polymers have been proposed as materials for polymeric optical fibers. Finally, polymers have been disclosed which were produced by polymerization of two allyl alcohol groups which have been esterified using the carboxylic acid groups of 1,4,5,6,7,7-hexachlorobicyclohept-5-ene-2,3-dicarboxylic acid (cf. Japanese Published Specification 61-51,901).

However, such polymers cannot be processed thermoplastically since they crosslink during the polymerization.

4 it r Polymers which contain the 1, 4 ,5,6,7,7-hexachloro[2.2.13bicyclohept-5-en-2-yL group in the alcohol part of acry- V Lates and methacrylates have also long been known (cf.

US Patent 3,022,277). However, nothing has been disclosed on the optical properties, the thermal distortion resistance and the processing properties of these polymers, or on the properties of copolymers with other acrylates and Smethacrylates.

i 10 The object was to provide a polymer which can be prepared in a simple and economical fashion and which can be processed into objects of high transparency and thermal distortion resistance.

15 It has been found that a transparent thermoplastic mold- 4 ing composition which is essentially derived from an ester of a (meth)acrylic acid with a bicyclic alcohol, it being possible for the acid and alcohol radical to be deuterated Sand/or halogenated, is capable of achieving the object.

The invention thus relates to a transparent thermoplastic molding composition comprising 10 to 100% by weight of units which are derived from an ester of the formula (I)

R

6

C

(I I) 3

(R

5 n R

R

3 0 R R 8 C C C O C

R

2

C

R

4 in which

R

6 R denotes a hydrogen, deuterium or fluorine atom,

R

2 denotes a hydrogen, deuterium or fluorine atom,

R

3 denotes a hydrogen, deuterium, fluorine, chlorine or bromine atom, a cyano group, or a methyl group in which all or some of the hydrogen atoms may be replaced by deuterium, fluorine or chlorine atoms, R denotes a hydrogen or deuterium atom or a C 1 to

C

5 -alkyl group in which all or some of the hydrogen 4 atoms may be replaced by deuterium or fluorine atoms, denotes a -CHR 9 or -CD R

R

5 denotes a -CHR 9 or -CDR group in which R is a hydrogen, deuterium, fluorine, chlorine or bromine atom or a C 1 to C 5 -alkyL group in which all or some of the hydrogen atoms may be replaced by deuterium or fluorine atoms, 6 R denotes a fluorine, chlorine or bromine atom or a trii fluoromethyl group,

R

7 denotes a -CH 2 group in which all or some of the hydroi 10 gen atoms may be replaced by deuterium, fluorine, chlor- S ine or bromine atoms, by two CH30 groups or by one 1', 2' -ethanediyldioxy group, denotes a carbonyl group or an ethylene group in which all or some of the hydrogen i atoms may be replaced by deuterium, chlorine or bromine atoms or by an oxo group, R denotes a -CR0=CR 10 group in which R 10 is a fluorine, chlorine or bromine atom or a trifluoromethyl Sgroup, or denotes a -C(R 1 1 2

-C(R

11 2 group in which

SR

1 1 is a fluorine atom or a trifluoromethyl group, S' 20 and n is zero or 1, n not being zero when R 7 is a -CH 2 or carbonyl group, and to 0% by weight of units which are derived from other copolymerizable vinyl compounds.

In addition, the invention also relates to the process for the production of these molding compositions and to the transparent optical objects produced from the molding composition.

In formula Ri is preferably a hydrogen, deuterium or fluorine atom, in particular a hydrogen or deuterium atom,

R

2 is preferably a hydrogen, deuterium or fluorine atom, in particular a hydrogen or deuterium atom,

R

3 is preferably a hydrogen, deuterium or fluorine atom, or a methyl group in which all or some of the hydrogen atoms may be replaced by deuterium atoms, in particular I I I is a deuterium or fluorine atom or a trideuteromethyl group, R is preferabLy a hydrogen or deuterium atom, 5 R is preferably a methylene, deuteromethylene or chloromethylene group, in particular a methylene or deuteromethylene group, R1is preferabLy a chlorine or bromine atom or a trifluoromethyL group, in particular a chlorine or bromine atom,

R

7 is preferably a methyLene group in which the hydrogen atoms may be replaced by deuterium, chlorine or bromine atoms or by two methoxy groups, is a carbonyl group or an ethyLer.e group in which the hydrogen atoms may be replaced by chlorine atoms or by an oxo group, in particular is a -CH 2

-CD

2

-CCL

2 -CBr 2

-CHCL-,

-C(=0)-CCI 2 or -CH 2

-CH

2 group, R8 is preferably a -CR 10

=CR

10 group in which Rio may denote a chlorine or bromine atom or a trifluoromethyL group, in particular may denote a chLorine or bromine i 011 11 1 atom, or is a -C(R 2 -C(R 2 group in which R 11 may denote a fluorine atom or a trifLuoromethyL group, and n is preferably 1.

The acid component of the esters used according to the invention is thus preferably acrylic acid, methacryLic acid, c-fluoroacrylic acid, a,$-difluoroacryic acid or the corresponding fully or partly deuterated compounds, in particular perdeuteromethacrylic acid, perdeuteroacrylic acid, c-fLuoroacrylic acid or perdeutero-a-fLuoroacrylic acid; the alcohol component is preferably i,3,4,5,6,7,7-heptachorobicycoE2 2.2.1hept-5-en-2-oL 1,4,5,6,7,7-hexachloro- or -hexabromobicyclo[2.2. lhept- 5-en-2-ol, 1,4,5,6,7-pentachorobicycloE2.2.)hept-5en-2-ol, 1,4,5,6-tetrachLorobicycLo[2.2.1)hept-5-en-2-oL, 1,2,3,4-tetrachlorobicycLo[2.2.1)hept-2-en-7-oL, 1,4,5,6tetrakis~trifLuoromethy)-7-oxo- or -7-bis(methoxy)bicyclo[2.2.1)hept-5-en-2-o, 1,2, 3 ,4-tetrakis(trifluoromethyl)bicycloE2.2.1)hept-2-en-7-oL, 1,2,3,4- -6tetrabrow~o-5,6-dichLorobicycLo[2.2. 1]hept-2-en-7-oL, 1,2,3,4-tetrachLoro-5,6-dibromobicycLo[2 llhept-2-en- 7-oL, 5,5,6,6-tetrakis(trifLuoromethyL )bicycLo[2.2. 1] heptan-2-oL, 5,5,6,6-tetrafLuorobicyctoC2.2. 1lheptan- 2-ol, 1,4,5,5(or 6,6),7,8-hexachLoro-6(or 1]oct-7-en-2-oL or 1,4,5,5,6,6,7,8g-octachLorobicycLoE2.2. ljoct-7-en-2-oL, in particular 1,4,5,6,7,7hexachioro- or -hexabromobicycLo[2.2. 1]hept-5-en-2-oL, 1,4.5,6,7-pentachLorobicycLoC2.2.llhept-5-en-2-oL, 1,4,5,6-tetrachLorobicycLo[2.2. 1]hept-5-en-2-oL, 5,5,6,6-tetrakis~trifLuoromethyL)bicycLo[2.2. llheptan- 2-oL, 5,5,6,6-tetrafLuorobicycLo[2.2.l]heptan-2-oL, :I 1,4,5,5(or 6,6),7,8-hexachLoro-6Cor 0 0 2.2.1]oct-7--en-2-oL.

4* 1 0 4 44 According to the invention, those esters are preferabLy used in whose~ aI"'ohoL and acid component the hydrogen atoms have been substituted as fully as possible by deuterium, fluorine, chlorine and bromine atoms or by trifLuoromethyL groups, in particular esters of perdleuteromethacryLic acid, perdleuteroacryLic acid, (x-fLuoroacrylic acid or perdeutero-cL-fLuoroacryLic acid with 1,4,5,6,7,7-hexachLoro- or -hexabromobicycLo[2.2. 1J hept-5-en-2-oL-2,2,3-d 3 ,1,4,5,6,7-pentachLorobicycLo llhept-5-en-2-oL-2,2,3-dl 3 1,4,5,6-tetrachLorobicycLo[2.2. 1]hept-5-en-2-oL-2,2,3-d 3 5,5,6,6tetrakis~trifLuoromethyL)bicycLoC2.2.1]heptan-2-oL- 1,2,3,4,7,7-dl 6 5,5,6,6-tetrafLuoro-bicycLoE2.2. 1J heptan-2-oL-1,2,3,4,7,7-dl 6 or 1,4,5,5Cor 6,6),7,8hexachLoro-6Cor 5)-oxobicycLoE2.2. lloct-7-en--2-oL- 2,2,3-d 3 The molding composition according to the invention comprises from 10 to 100, preferably 40 to 100, in particu- Lar 50 to 80, by weight of units which are derived from an ester of the formula and 90 to 0, preferably to 0, in particular 50 to 20, by weight of units which are derived from other copoLymerizabLe vinyl compounds.

Suitable compounds are C 1 to C 6 -aLkyt esters of acrylic acid, C_ to C -alkyl esters of methacrylic acid, C to C -alkyl esters of a-fluoroacrylic acid, styrene oz substituted styrene. The esters of acrylic acid, methacrylic acid and c-fluoroacrylic acid, and the deuterated derivatives thereof, are preferably used. In I particular, methyl acrylate, methyl methacrylates and methyl I-fluoroacrylate are employed, the corresponding deuterated compounds being particularly preferred.

The molding composition according to the invention is produced by free-radical block polymerization or suspension, emulsion or solution polymerization, in particular by block polymerization, of a compound of the I formula and, if appropriate, another copolymerizable vinyl compound.

II 15y, riiza-3ntie initiator may-be I Preferred free-radical active initiators are azo I compounds, such as azo-bisisobutyronitrile, azo-bis(cycloi hexylcarbonitrile), azo-bis(tert.-octane) and 2-phenylazo- 2,4-dimethyl-4-methoxyvaleronitrile, and organic peroxides, such as tert.-butyl peroxide, tert.-butyl peroctoate, S. tert.-butyl peroxyisopropylcarbonate, tert.-butyl hydroperoxide and tert.-butyl peroxyisobutyrate. The amount of initiator is preferably in the range 0.001 to 3, more 25 preferably 0.035 to 0.3, mole per 100 moles of the monomer or monomers. Polymerization is advantageously carried out Sin the presence of a chain-transfer agent (regulator).

Suitable for this purpose are, in particular, mercaptans, such as butyl mercaptan, tert.-butyl mercaptan, proply mercaptan, phenyl mercaptan, tert.-hexyl mercaptan and butylene-l,4-dithiol, and esters of mercaptoacetic acid, for example ethyl mercaptoacetate and ethylene glycol bis(mercaptoacetate) The ::f:rr polymerization temperature is to 180 0 C, more preferably 80 to 160 0 C and particularly preferably 100 to 160 0

C.

[elb Disk 6/1.59 MG -8- It is advisable to degas the reaction mixture before commencing the polymerization. For this purpose, the reaction mixture comprising monomers, initiator and, if appropriate, regulator is initially cooled in a reactor to a temperature of at least -80°C, the reactor is then evacuated and, in a sealed state, warmed to a temperature of 0 to this procedure can be repeated several times.

The molding composition according to the invention is produced in the form of a glass-clear, thermoformable material. It is therefore suitable, above all, as a material for the production of transparent objects, for example resist materials, lenses, optical fibers and, alone r t\ or mixed with another polymer which has a different refractive index, as a material for optical data-storage 15 media. The spectral transparency of the molding composition o is particularly high in the wavelength range from 600 to o 1,300 nm. The molding composition preferably exhibits the 8 0 characteristic properties below: Mean molecular weight 8,000 to 5,000,000, more preferably 50,000 to 200,000 (measured by the lighto o scattering method).

°Glass-transition temperature 95 to 250 0 C, more ii preferably 120 to 200 0 C, particularly preferably 150 to 180 0

C.

8848 25 Decomposition temperature at least 230°C, more preferably 250 to 300 0

C.

The objects manufactured from the molding °o 0 composition according to the invention have an excellent thermal distortion resistance and are nonflammable.

The following Examples serve to illustrate the invention in greater detail. Percentages in each case relate to the weight.

Melb Disk 6/1.59 MG 9 Example 1 1) 1,2,3,4,7,7-Hexachlorobicyclo[2.2.13hept-2-en-5-yL acetate 100 g (0.366 mol) of hexachlorocyclopentadiene and 37 g (0.43 mol) of vinyl acetate were refluxed in a 250 ml three-neck flask equipped with magnetic stirrer, thermometer and reflux condenser. During refluxing, the temperature of the reaction mixture was 4 initially 870C and towards the end, after 40 hours, 139 0 C. The mixture was subjected to fractional distillation, 95 g of the ester being obtained as the main fraction at 105-112 0 C (0.05 mbar) (72% of theory).

2) 1,2,3,4,7,7-HexachlorobicycloC2.2.1Jhept-2-en-5-ol 1,760 ml of methanol and 17.6 ml of concentrated hydrochloric acid were added to 880 g (2.45 mol) of compound 1 in a 4 L three-neck flask equipped with magnetic stirrer, thermometer and reflux condenser, and the mixture was refluxed for 4 hours. The solvent was then evaporated and the solid residue was recrystallized from n-heptane, 704 g of the alcohol being obtained (90% of theory).

3) 1,2,3,4,7,7-Hexachlorobicyclo2.2.2.1hept-2-en-5-yl acrylate (AHC) 50 g (0.158 mol) of compound 2 were dissolved in 150 ml of toluene in a 500 ml three-neck flask equipped with magnetic stirrer, thermometer and reflux condenser, and 21.5 g (G.237 mol) of acryl chloride were added at 70 0 C. The mixture was subsequently stirred at this temperature for a further 16 hours. The solvent was then evaporated and the residue distilled. The fraction at around 118 C (60.6 g) was dissolved in diethyl ether and filtered through an A1 2 0 3 column.

After evaporation of the diethyl ether from the I- .i 4 4 44rt 444 t 44 44, 4: 4 44 4 10 filtrate, 33.4 g of the acrylate were obtained (57% of theory).

4) 1,2,3,4,7,7-Hexachlorobicyclo[2.2.1]hept-2-en-5-yL methacrylate

(MA-HC)

200 g (0.63 moL) of compound 2 were dissolved in 500 ml of toluene in a 1 L three-neck flask equipped with magnetic stirrer, thermometer and reflux con- 10 denser, and 99.2 g (0.95 mol) of methacryl chloride were added. This mixture was then stirred under reflux for 30 hours. The solvent was subsequently evaporated and the residue, dissolved in diethyl ether, filtered through an AL 2 0 3 column. After evaporation of the diethyl ether, 189.4 g of the methacrylate were obtained (78% of theory).

Example 2 A solution of 100 parts of hexachlorobicycloheptenyl acrylate (AHC), 0.05 part of dicumyl peroxide and 0.17 part of butyl mercaptan were filtered through a membrane filter (pore size 200 nm) into a glass vessel and carefully degassed. For this purpose, the reaction mixture was firstly frozen using liquid nitrogen, and the glass vessel was then evacuated (0.001 mbar) and subsequently warmed to room temperature. This procedure was repeated three times. The reaction vessel was then sealed, and the degassed reaction mixture was initially warmed for 5 hours at a temperature of 123 0 C, then at a temperature of 140 0 C. After cooling to room temperature, a glassclear polymeric material was obtained on which the following properties were measured.

i i i ii -lo? f t r I: i Mean degree of polymerization Pw Glass transition temperature Decomposition temperature Melt flow index (250 0 C; 3.8 kg) 2,050 159 0

C

270 0

C

8 g/10 min 11 Residual monomer content 23 Refractive index n 3 1.54 i Example 3 A solution of 50 parts of hexachlorobicycloheptenyl methi acrylate (MAHC), 0.03 part of azoisobutyronitriLe and I part of butyl mercaptan in 50 parts of chloroform were i filtered and degassed analogously to Example 2. The degassed reaction mixture was then warmed at a temperature of 600C for 20 hours. After the batch had been cooled to I room temperature, 400 parts of acetone were added, and the Iresultant mixture was transferred into 6,000 parts of hex- SV ane. The polymer which precipitates during this operation was separated from the Liquid, reprecipitated from acetone/hexane and dried for 6 hours at a temperature of 100°C in vacuo. 40 g (80% of theory) of a polymer were obtained on which the following properties were measured: Mean degree of polymerization Pw 500 Glass transition temperature 220 0

C

Decomposition temperature 300 0

C

ExampLcs 4 to 6 i Solutions comprising various amounts of MAHC and methyl methacrylate (MMA) and containing 0.1 g of azoisobutyronitrile and 0.15 g of butyl mercaptan in each case were filtered and degassed analogously to Example 2. The degassed reaction mixtures were each warmed to a temperature of 60°C for 30 minutes and, after cooling to room temperature, mixed with 300 ml of acetone. The mixtures obtained in each case were transferred into 5 L of hexane, and the precipitated copolymers were separated from the liquid and dried for 6 hours at a temperature of 700C.

The respective composition of the monomer mixture and the 12copolymer and the glass transition temperature (Tg) of the copolymer can be seen from Table 1.

Table 1 Example MMA:MAHC weight ratio Tg (oC) n 3 Monomer Copolymer xmixture 4 28:72 23:77 161 1.529 51:49 40:60 155 1.523 6 70:30 59:41 147 1.513 tr I Example 7 A mixture of 50 parts of MAHC and 50 parts of MMA, 0.05 part of tert.-butyl isopropylperoxycarbonate and 0.5 part of butanedithiol was saturated with nitrogen in a (pressure-tight) reaction vessel equipped with stirrer and metering device. The reaction solution was warmed to 90 0

C

while stirring.

It was possible to detect a slight increase in viscosity, and thus commencement of the reaction, from an increase in the power consumption of the stirrer. A sample was removed from the mixture 15 minutes after commencement of polymerization, and the MMA:MAHC concentration ratio was determined by gas chromatography. Corresponding to the increased consumption of MAHC, further parts of a mixture comprising 40 parts of MMA, 60 parts of MAHC, 0.05 part of butanedithiol and 0.4 part of tert.-butyl isopropylperoxycarbonate were metered in continuously, and the metering rate adjusted, in accordance with the results of further (gas chromatographic) analyses so that a MMA:MAHC free monomer concentration ratio of 52:48 (g/g) was maintained in the reaction vessel.

When the subsequent metering was complete, the reaction mixture was heated to 160 0 C over the course of 2 hours ~ibiaarc**-~- ii- 13 and kept at this temperature for 2 hours. The mixture was subsequently transferred into a two-stage degassing extruder where residual monomer was removed.

The glass transition point of the granulated material was Tg 157 0 C, and the mean degree of polymerization was Pw 2,340.

Example 8 It was possible to mold the material from Example 2 in a S« mold at 250 0 C under pressure to form lenses and similar optical objects. After the surface of a lens had been Sro. polished, a transmission of 91% of the incident Light was 0 t achieved.

4 STransmission and image-formation properties of this lens remained unchanged even after storage for 24 hours at o0 1000C and an atmospheric humidity of 100 mbar.

20 Comparison Example A 0' A lens molded under the conditions of Example 8 from a polymeric glass element made from polymethyl methacrylate (PMMA) exhibited, after polishing, a transmission of 89% and comparable image-formation properties. After storage S for only 2 hours at 120°C, the surface of the lens was clearly cloudy and the shape of the lens had changed so substantially that a usable image was no longer produced.

P 30 Example 9 The polymerization by the method of Example 7 was repeated, and the polymer was processed directly, without granulation, to form an optical fiber. Of the light intensity which was shone into the front face of the optical fiber, it was possible to measure 45% after a length of three meters, and 70% after a length of one meter.

After the fiber had been stored for 7 days at 120 0 C and i 10 o t 0 I 14 an atmospheric humidity of 100 mbar, it was still possible to detect 70% of the incident light intens-.y after a length of one meter and 43% after three meters.

Comparison Example B: A three-meter length of an optical fiber made from PMMA exhibited a transmission of 70% at the beginning of the experiment. After storage at 110 0 C for three hours, the length of the fiber had already shrunk by half and the transmission had dropped to 10% of the incident light intensity.

4~ 4 0 0 0i 4

I

v -w

Claims (6)

1. A transparent thermoplastic molding composition, compris- ing 10 to 100% by weight of units which are derived from an ester of the formula (1) R 6 C 3 (R IIR 8 (I) 1 Rl p3 O R 7 R C C C 6 iR 6 in which R1 denotes a hydrogen, deuterium or fluorine atom, R 2 denotes a hydrogen, deuterium or fluorine atom, R denotes a hydrogen, deuterium, fluorine, chlorine or bromine atom, a cyano group, or a methyl group in which all or some of the hydrogen atoms may be replaced Sby deuterium, fluorine or chlorine atoms, S'R denotes a hydrogen or deuterium atom or a C 1 to C 5 -alkyl group in which all or some of the hydrogen 4 atoms may be replaced by deuterium or fluorine atoms, R 5 denotes a -CHR 9 or -CDR 9 group in which R 9 is a hydro- gen, deuterium, fluorine, chlorine or bromine atom or a C 1 to C 5 -alkyl group in which all or some of the hydrogen atoms may be replaced by deuterium or fluor- ine atoms, R 6 denotes a fluorine, chlorine or bromine atom or a tri- fluoromethyl group, R 7 denotes a -CH 2 group in which all or some of the hydrogen atoms may be replaced by deuterium, fluorine, chlorine or bromine atoms, by two CH 3 0 groups or by one 1',2'-ethanediyldioxy group, denotes a carbonyl I i I i- -r i: f 16 group or an ethylene group in which all or some of the hydrogen atoms may be replaced by deuterium, chlorine or bromine atoms or by an oxo group, R 8 denotes a -CR1 0 =-CR 1 0 group in which R 10 is a fluor- ine, chlorine or bromine atom or a trifluoromethyl group, or denotes a -C(R 2 -C(R 2 group in which 11 R 1 is a fluorine atom or a trifLuoromethyl group, and n is zero or 1, n not being zero when R 7 is a -CH 2 or carbonyl group, and S. 90 to 0% by weight of units which are derived from other copo ymerizable vinyl compounds.

2. A molding composition as claimed in claim 1, wherein the compound of the formula is an ester of 1,4,5,6,7,7- hexachloro- or -hexabromobicycloC2.2.1hept-5-en-2-ol, 1,4,5,6,7-pentachlorobicycloL2.2.13hept-5-en-2-ol, 1,4,5,6-tetrachlorobicycloC2.2.1]hept-5-en-2-ol, 5,5,6,6-tetrakis(trifluoromethyl)bicycloC2.2.1]heptan- 2-oL, 5,5,6,6-tetrafluorobicycloC2.2.1]heptan-2-ol, or 1,4,5,5(or 6,6),7,8-hexachloro-6(or 5)-oxobicycloE2.2.11 S °oct-7-en-2-ol. J 3. A molding composition as claimed in claim 1, wherein the Scopolymerizable vinyl compounds are C 1 -C 6 -alkyl esters of acrylic acid, C 1 -C 6 -alkyl esters of methacrylic acid, C 1 to C 6 -alkyl esters of a-fluoroacrylic acid, styrene or substituted styrene.

4. A process for the production of a transparent thermo- plastic molding composition by free-radical block poly merization of the monomers, wherein 10 to 100% by weight of an ester of the formula (I) i l;i 17 R 6 I (I) C (R )n I R 1 R 3 0 R 7 R C=C- -0-C R 2 4 R 4 R 6 in which R R 2 R 3 R 4 R R R 8 Ri and R 1 1 have the meanings mentioned in claim 1, and 90 to 0% by weight of another polymerizable vinyl compound are polymerized in the 15 presence of a free radical initiator and at a temperature of 60 180 0 C. or t The process as claimed in claim 4, wherein 40 to 100% by weight of an ester of 1,4,5,6,7,7-hexachlorobicyclo- S 201 [2.2.1]-hept-5-en-2-ol and 60 to 0% by weight of another polymerizable vinyl compound are polymerized.

6. The use of a molding composition as claimed in claim 1 for the production of transparent optical objects.

7. The use as claimed in claim 6 for the production of optical storage media.

8. The use as claimed in claim 6 for the production of optical fibers. DATED this 9th day of October, 1990 HOECHST AKTIENGESELLSCHAFT WATERMARK PATENT TRADEMARK ATTORNEYS 2nd Floor "The Atrium" 290 Burwood Road HAWTHORN VICTORIA 3122 AUSTRALIA 4.19:SC:KJS