AU601779B2 - Cross-linkable casting composition - Google Patents

Description

I

I

AUSTRALIA 6 1 77 9 Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: a o s i a oc a i a 4

C

a This document contains the amendments made under Section 49 and is correct for printing.

APPLICANT'S REF.: CAP-:of PH 9090 SOLA INTERNATIONAL HOLDINGS LTD.

Name(s) of Appli:ant(s): Address(es) of Applicant(s): Sherriffs Road, Lonsdale, South Australia, Australia HUAN KIAK TOH ta Actual Inventor(s): Address for Service is: PHILLIPS, ORMONDE AND FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne, Australia, 3000 Complete Specification for the invention entitled: CROSS-LINKABLE CASTING COMPOSITION The following statement is a full description of this invention, including the best method of performing it known to applicant(s): P19/3/84 li)ii~:; i :1 ~-I~-lllllil_ The present invention relates to the manufacture of plastic optical articles such as video discs and ophthalmic lenses. The most widely used plastic ophthalmic lens material is polymerised diethylene glycol bis (allyl carbonate). This polymer has proved a satisfactory material for the manufacture of ophthalmic lenses because of a combination of features, including excellent transmission, resistance to discolouration, high strength and high impact resistance. The material has a reasonable abrasion resistance and can be coated to improve that resistance.

The manufacturing process involves the polymerisation of diethylene glycol bis (allyl carbonate) by curing the material within a pair of glass moulds sealed by a gasket and held together by a clip. The cure times are lengthy and can be as long as 16 hours or more. Such extended cure times not only mean that a large stock of glass S' moulds is required but that also, warehouse stocks of cast polymerised lenses are high so as to meet order requirements as they arise.

*r 4 S t, 4 tr 4 L( t4 t.j There has been a long felt need for a material which could be cast using the existing arrangements with a considerably reduced cure time while still producing a lens with all the desirable characteristics of those made with diethylene glycol bis (allyl carbonate).

Urethane acrylates and methacrylates have been widely used in the formulation of coating compositions, photosensitive compositions for making flexographic printing plates, adhesives and dental filling materials. In such formulations the urethane material is usually chosen so as to have a high viscosity and low shrinkage and forms the principle component of any formulation.

In order to cast a satisfactory lens by a commerically useful casting process from a composition containing a urethane acrylate or methacrylate, it is necessary to formulate the composition so as to have a viscosity not exceeding approximately 200 cps at 25 C.

Accordingly, it is an object of the present invention to overcome, or at least alleviate, one or more of the difficulties related to the prior art.

Accordingly, the present invention provides a z-eea 2 4 1. r -3a cross-linkable polymeric casting composition including at least polyoxyalkylene glycol diacrylate or dimethacrylate, at least one polyfunctional unsaturated cross-linking agent and a urethane monomer having from 2 to 6 terminal acrylic and/or methacryic groups.

The at least one polyoxy alkylene glycol diacrylate or dimethacrylate compound according to the present invention may include ethylene oxide or propylene oxide repeating units in its backbone. An ethylene glycol derivative is preferred.

Preferably from approximately 6 to 11 alkylene oxide repeating units may be included.

A polyethylene glycol dimethacrylate is preferred.

A polyethylene glycol dimethacrylate with an average molecular weight of the order of 600 is preferred. One f 'C suitable material is that sold under the trade name NKESTER 9G by SHIN NAKAMURA which has an average Molecular weight of 536. The average number of ethylene oxide polymerised units is 9. Alternatively, an NK Ester 6G At a having an average number of 6 ethylene oxide polymerised units may be used.

Though the use of polyethylene glycol dimethacrylate on its own is exemplified below, it is also possible to use mixtures of polyethylene glycol diacrylates and LI I C t I OF

RB

U 48r T' VLL *7"E 1 dimethacrylates. Mixed esters can also be used.

The at least one polyoxy alkylene glycol diacrylate or dimethacrylate component may be present in an amount suitable to provide a viscosity of not greater approximately 200 cps at 25°C in the final product. The diacrylate or dimethacrylate compound may be present in amounts of from approximately 40% by weight to 60% by weight based on the total weight of the casting composition. The diacrylate or dimethacrylate component is preferably present in amounts of at least approximately 45% by weight, more preferably 50% by weight.

The dimethacrylates are more preferred than the diacrylates as the diacrylates need to be used with care, as with their greater reactivity than the corresponding dimethacrylates, distortion may be introduced into the lens blank as cast due to strain. Any particular diacrylate also S tends to be more water absorbing than the corresponding dimethacrylate. It has also been found that as the number of polymerised alkylene oxide groups is increased from six, in the case of both dimethacrylates and diacrylates the water absorption increases and becomes unacceptably high at an average value of 12 alkylene oxide groups per molecule.

water and can result in cracking subsequent to tinting.

The poly functional unsaturated cross-linking .gent according to the present invention may be a tri- o' tetrafunctional vinyl, an acrylic or methacrylic ,ronomer. The cross-linking agent may be a short chain mpdomer for example trimethylol propane trimethacryl t'e, pentaerythritol triacrylate or tetracrylate, /r the like. Other polyfunctional cross-linking a ts which may be used include NK ESTER TMPT 0 CH CH -0-C-C=CH

SCHC-CH

2 -O-C-C=CH 2 S0 CH 3 4CH C-=CH 04N- 4 ~LL- The term "poly functional unsaturated cross-linking" agent according to the present invention as used herein the description and claims refers to a tri- or tetra- functional vinyl, an acrylic or methacrylic monomer. The cross-linking agent may be a short chain monomer for example trimethylol propane trimethacrylate, pentaerythritol triacrylate or tetracrylate, or the like. Other polyfunctional cross-linking agents which may be used include NK ESTER TMPT O CH o 0 CH -O-C-C=CH 2 I CH 3 CH CH -O-C-C=CH O CH 3 3 2 2 1 2 CH -O-C-C=CH S0 2 C 2 O CH 2 *1 FY FY P o -4a- *i 1 0. cj.-L r NK ESTER A-TMPT 0 11 CH C1=CH 2

CH

3 Uri -C-CH 2

-C-CH=CH

2 CH 2 -O0-jjCH=CH 2 0 NK ESTER A-TMM-3 0 CH -O-C-CH=CH 1 2 2 HO-Ch 2 C-CH O-C--CH=CH 2 2 O 2( NESTER A-TMMT 0 0 CH -O-C-CH=CH 2 CH =CH-A-O-CH 2 -C-CH -O-C-CH=CH 2 22 2 112 0 DI-TRIMETHYLOL PROPANE TETRAACRYLATE 4kCH -CHCOO OOCCH=CH 2 1 12 CH CH OCH 2~2 2 2 CH L;H7 UhCH O OOCCt-Ch2 trimethyloipropane triacrylate, pentaerythritrol tetramethacrylate, dipentaerythritol monohydroxypenta acrylate, pentaerythritol triacrylate, ethoxylated trimethyloipropane triacrylate, ethoxylated trimethylolpropane trimethacrylate.

It has been found when operating at the lower end of the preferred range 40 to 60% for the diacrylate or dimethacrylate component that it is preferable to select as the polyfunctional unsaturated cross linking age'nt, material such as that sold under the trade name SR-454 which is an ethoxylated trimethylol propane triacrylate.

The poly functional unsaturated cross-linking agent may be present in amounts of from approximately 10 to 30% by weight preferably approximately 20% by weight based on the total weight of the casting composition. The weight ratio of cross-linking agent to tetracrylic urethane monomer, when present, is preferably in the range of approximately 1:4 to 2:1.

As stated above, the cross-linkable polymeric coating composition in a preferred form may also include a urethane monomer having terminal acrylic and/or methacrylic groups. The number of such groups can vary from 2 to 6, and we have found that satisfactory materials fo- use in this invention are those in which the molecular weight of the compound divided by the functionality or number of groups is 200 50. Suitable materials falling within this definition include materials supplied under the trade names U-4H, U-4HA and U-6HA by Shin Nakamura, NF-201 and NF-202 by Mitsubishi Rayon. These monomers are included to improve physical toughness without causing the lens material to become too brittle. Impact resistance is improved without adversely affecting abrasion resistance.

The structures contained within any particular monomer can be selected from those containing aliphatic, I aromatic, and cyclic structures of other forms. We have V found that in the formulations of the present invention, the tetracrylic urethane monomer gives particularly satisfactory results.

The inclusion of the tetracrylic urethane monomer may provide a product of increased hardness.

The tetracrylic urethane monomer according to a preferred aspect of the present invention may be a compound of the formula 4 -6-

V

LIL- R R 3

R

1 2 2 1 CR =C-COOCR -C-CR -OCO-C=CR 2 2 1 2 2 0

NH

X

NH

CO

R O R 12 2 12 1 CR =C-COOCR -C-CR -OCO-C=CR 2 2 132 2

R

*r r r,

I

LI

C r 1 2 3 wherein R, R R and R which may be the same or different are selected from hydrogen, alkyl of 1 to 6 carbon atoms or a substituted alkyl of 1 to 6 carbon atoms; and X is an organic residue having 1 to 20 carbon atoms. X may be an aliphatic, alicyclic or aromatic residue. X may be a C1-C20 alkyl, alkoxy, alkylamino, alkyl carbonyl alkoxy carbonyl, alkylamido or alkoxy amide group.

X may be substituted with one or more halogen, hydroxyl, nitro, amino, alkyl or alkoxy groups.

The tetracrylic urethane monomer may be present in any suitable amount to provide a desired level of hardness.

The tetracrylic urethane monomer may be present in amounts of from 0 to approximately 40% by weight, preferably 10 to Dy weight based on the total weight of the casting composition.

Where X is an aromatic group, the article formed therefrom may exhibit a high refractive index and be suitable i- for applications where this is desirable. A urethane monomer having the following structure is preferred: R R

CH

2

=C-COOCH

2

-CH-CH

2

-OCO-C=CH

2 I 0

CO

NH

NH

CO

R 0 R

CH

2

-COOCH

2

-CH-CH

2

-OCO-C=CH

wherein R is a hydrogen atom or a methyl group or a substituted methyl group and X is an organic residue having 2 20 carbon atoms, preferably 6 carbon atoms.

In the above formula, while X may be any of organic residues having 2 20 carbon atoms, it is generally an aliphatic or alicyclic hydrocarbon residue, the backbone of which may be interrupted by oxygen. Specific examples thereof are as follows: Examples of aliphatic hydrocarbon residues include alkylene groups such as -CH 2

CH

2

-(CH

2 3

-(CH

2 4 -(CH2) 6

CH

S3 -CH -C-CH -CH-CH -CH- 2 2 2 2

CH

3 CH -(CH18-, -(CH2)1 -CH 2 etc.

(ii) alkyloxyalkylene groups such as -C2H40C2H

-(CH

2 6

(CH

2 6 etc. and the like.

The urethane monomer may be produced by reacting 2 moles of a glycerin di(meth)acrylate R R (CH2= -COOCH 2

CHCH

2 0

COC=CH

2

OH

and 1 mole of an organic diisocyanate compound (OCN-X-NCO).

The glycerin di(meth)acrylates are known compounds which can be obtained by reacting glycidyl (meth)acrylate and (meth)acrylic acid. The organic diisocyanate compounds are 7 7 known compounds, many of wDhich are on the market and thus easily available. The, organic diisocyanate comply with the definition of X and thus their examples include ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate. The reaction of the glycerin di(meth)acrylate and the organic diisocyanate may be conducted using a catalyst commonly used for reactions of alcohols and isocyanates dibutyltin dilaurate) in the absence of a solvent, or by dissolving in a solvent. The solvent used is an organic solvent having no active hydrogen such as methyl chloride, benzene, toluene, etc. The reaction is preferably carried out at a temperature of up to 100 C (generally 200 90 0 thereby free radical polymerisation of the di(meth)acrylate monomer can be prevented, and a reaction time of 1 2 hours affords the monomer almost in a quantitive yield. After the reaction, the monomer may be obtained by removing the reaction solvent.

The cross-linkable casting composition according to the present invention may further include a cross-linking initiator. The cross-linking initiator may be a heat and/or ultraviolet initiator.

The compositions are preferably cured by a combination of UV radiation and heat. The combination of UV radiation and heat may reduce the possibility of incomplete curing for example due to the phenomenon known as "radical trapping".

The composition, with the addition of approximately to 2.0% by weight of cross-linking initiator may be exposed to UV radiation for between 0.5 and 10 seconds.

Any commercially viable UV curing system may be used. We have used a Fusion System with microwave driven lamps. A number of fusion bulbs with different output Spectra may be considered. Presently we prefer the bulb and the bulb.

One source we have found satisfactory is a 10 inch, 300 watt/inch mercury lamp. The mould assembly is then heated to 100 C for one hour or the lens may be removed from the assembly and heated in air for about one hour at 100C. This means that fully cured lenses can be 8 manufactured, if desired, in about one hour. Heat curing can also be used without any use of U.V. radiation.

Typically 2 4 passes under the UV lamps plus an hour of heat treatment at 100°C completes the cure.

Any suitable UV initiator may be used. An initiator available under the trade designation Irgacure 184 has been found to be satisfactory. More than one curing agent may be present. It has been possible to operate with a relatively low level of initiator of between 0.05 and 0.2% by weight.

A range of photoinitiators available commercially can be used, depending on sample thickness, type of UV lamp used and the .absorption wavelength of the monomer mix.

The following photoinitiators have been found to be S suitable.

Alcolac Vicure 10 isobutyl benzoin ether 2' Alcolac Vicure 30 isopropyl benzoin ether Alcolac Vicure 55 methyl phenyl glyoxylate Ciba Geigy Irgacure 184 1 hydroxy cyclohexyl phenyl ketone Ciba Geigy Irgacure 651 benzildimethyl ketal Ciba Geigy Irgacure 907 2 methyl 1 [4--(methylthio)phenyl] 2 morpholino propanone 1 S Merck Darocur 1664 Rohm Catalyst 22 A mixture of the above may also be used.

Additionally, combination of photoiniator mixtures or photoinitiator mixtures with a heat induced free radical S initiator such as peroxides, peroxypercabo.nates or an azo compound may also be employed.

As an alternative to photo curing -a heat curing may be used, for example 1,1 di-tert buty1l peroxy -3,3,5trimethylcyclohexane or secondary isopropyl percarbonate.

Other additives may be presenrt whi ch are conventionally used in casting compos.itions' such as inhibitors, dyes, UV stabilisers and .materials capable of piodifying refractive index. Mould release agents can be added but they are in general not required with the compositions used in the method of the present invention.

Such additives may include: 9 UV Absorbers including Ciba Geigy Tinuvin P 2(2'-hydroxy-5'metnyl phenyl) benzotriazole Cyanamid Cyasorb UV 531 -2-hydroxy-4-n--octoxybenzophenone Cyanamid Cyasorb UV5411-2(2-hydroxy-5--t-octylphenyl)benzotriazole Cyanamid UV 2098 2 hydroxy-4-(2-acryloyloxyethoxy) j benzophenone 4 National S C Perrnasorb MA 2 hydroxy-4-(2 hydroxy-3methacryloxy)propoxy benzophenone Cyanamid UV24 2,2'-dihydroxy-4-methoxybenzophenone p- BASF UVINUL 400 -2,4 dihydroxy-benzophenone BASF UVINUL D-49 -2,2'-dihydroxy-4,4' dimethoxybenzophenone BASF UVINUL D-50 4,4' tetrahydroxy benzophenone BASF UVINUL D-35-ethyl-2--cyano-3,3-diphenyi acrylate -BASF UNINYL N-539-2-ethexyl-2-cyano-3,3-diphenyl acrylate Ciba Geigy Tinnuin 213 Hindered amine ligrht stabilizers (HALS). including -Ciba Geigy Tinuvin 765/292 bis (l,2,2,6,6-pentamethyl-4piperidyl)sebacate -Ciba Geigy 770 bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate 11 Antioxidants including.

-Ciba Geigy Irganox 245 -triethylene glycol-bis-3-(3-tert phenyl)propionate -Irganox 1010 -2,2-bis[[3-[3,4-bis(l,l-dimethylethyl)-4hydroxyphenyl]-l-oxopropoxylrnethyl]-l,3-propanediyl (1,1-dimethyl ety)4hdoybenzene propanoate 106- otdcl3-(3',5'-di=tert=butyl(-4'-hydroxy phenyl) propionate 10 Cure modifiers including Dodecyl mercaptan Butyl mercaptan Thiophenol Other monomeric additives can be present in amounts up to 10% by weight as diluents, and include monomers such as methacrylic acid, vinyl silanes, methyl allyl, hydroxy ethyl, benzyl and phenyl methacrylate, styrene and N-vinyl pyrrolidone. Other monomeric additives may be included to improve processing and/or material properties, these include: methacrylic acid, maleic anhydride, acrylic acid adhesion promoters/modifiers such as Sartomer 9008, Sartomer 9013, Sartomer 9015 etc.

dye-enhancing, pH-adjusting monomers like Alcolac SIPOMER 2MIM a charge-reducing cationic monomer to render.the material more antistatic, example Sipomer Q5-80 or Q9-75 hydrophobic comonomers: Shin Nakamura NPG, P9-G etc. to reduce the water adsorption of the material S refractive index modifiers such as benzyl or phenyl methacrylates to adjust the refractive index to the desired value.

In a further aspect of the present invention there is provided a polymeric article formed from a cross linkable c casting composition as described above. The polymeric article may be an optical article. The optical article may provide characteristics equal to or greater than those achievable with articles made from diethylene glycol bis(allyl carbonate) but with a considerably reduced cure time and substantially increased throughput.

The optical articles prepared by the method of this invention include camera lenses, ophthalmic lenses and video discs.

The casting composition may be formed into a suitable article by mixing in a convenient vessel the components making up the material, and then adding the curing ;i catalyst and/or photo-initiator. The mixed material is then Sdegassed or filtered. As the curing time is substantially reduced the casting process may be undertaken on a continuous or semi-continuous basis.

The present invention will now be more fully described with reference to the accompanying examples. It should be understood, however, that the description following is illustrative.only and should not be taken in any way as a restriction on the generality of the invention described above.

11 v--a 4

I

i~1 The following Examples 1 to 4 are provided for purposes of comparison. In all cases the casting material was used to fill the space between a pair of glass moulds separated by a plastic gasket at their periphery and held together by a clip.

10 0Q 0 VG (C Ca t f j i 12 b7j7~

'V

1 n rrr r nn ^r 4 -08 *E 9

O

n n 4 4 C 0* C C

I

EXAMPLE CASTING NUMBER MATERIAL

CURING

CATALYST/

INITIATOR

CURING

TEMP.

AND

TIME

YELLOGNESS

INDEX

(1.8 m) THICK PLANO

LENS

TRANS-

MISSION

BARCOL

HARD-

NESS

TABAR

ABRASION

200 CYCLES W 500 GMS

LOAD

HAZE

SHRINK-

AGE

CALCU.

MONOMER

VALUES

Diethylene Glycol Bis (allyl carbonate) Example 1 coated with Abrasion Resistant coating

PEGM

U-4HA

TMPT

40-90 0

C

17 Hours 3.0% SIP 0.62 92.0 31.8 19.0 14.0 2%

IRGACURE

184 0.5 Secs.

UV 1 Hour 100 C 0.78 2.21 91.3 33.8 6.7 90.9 56.3 6.8 14.0 10.4

PEHM

Difunctional Urethane 0.2% SIP Acrylate (Sartomer 9504)

TMPT

43-90C 5 Hours Soft/ Cloudy Rubber Cloudy aft C U CS C C C 0 0 C THE FOLLOWING EXAMPLES 5 10 ILLUSTRATE BUT DO NOT LIMIT THE INVENTION

CURING

EXAMPLE CASTING CATALYST/ NUMBER MATERIAL INITIATOR

CURING

TEMP.

AND

TIME

YELLOWNESS

INDEX

(1.8 m) THICK PLANO

LENS

TRANS

MISSION

BARCOL

HARD-

NESS

TABAR

ABRASION

200 CYCLES W 500 GMS

LOAD

HAZE

SHRINK-

AGE

CALCU.

MONOMER

VALUES

PEGM

TEGM

PEGM

U-4HA

TMPT

PEGM

U-4HA

TMPT

PEGM

U-4HA

TMPT

0.1% SIP 40-90 C 5 Hours 0.1% SIP 40-90°C 5 Hours 0.2% SIP 40-90°C 5 Hours 0.2% SIP 40-90°C 5 Hours 0.90 0.77 0.76 0.78 1.05 91.7 1.1 6.8 91.9 47.5 6.8 91.9 28.5 91.9 43.6 7.1 92.3 47.0 6.6 PEGM 0.5% U-4HA IRGA( TMPT 184 0.5 Secs

UV

CURE 1 hour at 100°C

PEGM

U-4HA

TMPT

0.5%

IRGACURE

184 0.5 secs 2.20 UV 1 hour at 100°C (2.2mm) 44.0 eAR

A,

C

AR b~ o*4 AA A

A

Re

A

o 0 9 A GA Q A 9A A A CA A A A A A AC C A A A P A Cc 4 4 0.b A SAC CCC 900 EXAMPLE CASTING

CURING

CATALYST/

CURING

TEMP.

AND TIME

YELLOWNESS

INDEX

(1.8 mm)

THICK

PLANO LENS

TRANS-

MISSION

TABER

ABRAS ION 200 CYCLES W 500 GMS

LOAD

HAZE

SHRINKAGE

CALCU.

MONOMER

VALUES BARCOL

HARDNESS

NUMBER MATERIAL

INITIATOR

11.

13.

60% 4G 0.1% SIP U-4HA

TMPT

4G 0.1% SIP U-4HA

TMPT

30% 23G 0.1% SIP 3G U-4HA

TMPT

23G 0.1% SIP 3G U-4HA

TMPT

40-900C 5 hours 1.10 91.8 49.2 22 .0 40-900 5 hours 1.25 91.7 53.4 20. 1 12. 3 40-90 0 5 hours 12.6 0.80 91.2 28.5 27.5 12 .4 40-900 5 hours 0.86 91.2 40.1 27.2 12.6 9G 0.2% UV 0.86 91.5 24.2 12. 0 7.9 TMPT Vicure 55 1 hr 1000 NF201 0 0 00 4 *4

CURING

EXAMPLE CASTING CATALYST!

YELLOWNESS

INDEX

CURING (1.8 mm) TEMP. THICK AND TIME PLANO LENS

TABER

ABRAS ION 200 CYCLES W 500 GMS

LOAD

HAZE

TRANS-

MISSION

SHRINKAGE

CALCU.

MONOMER

VALUES BARCOL

HARDNESS

NUMBER MATERIAL

INITIATOR

9G

TMPT

NF202 0.2% Vicure 55 UV 1 hr 1000 0.63 91.6 28. 7 15.2 7.9 18.

9g 0.2% SIP

TMPT

U-6HA 60% 6G 0.1% SIP U-4HA

TMPT

60% 6G 0.1% SIP U-4H

TMPT

40-90 0C 5 hour 0.60 92.2 24.2 7.0 40-900 5 hours 1.10 8_8 92.4 38.5 19. 40-900 5 hours 40-900 C 5 hours 1.15 92.4 40.5 9.4 60% 9G 0.1% SIP U-4H

TMPT

0.72 92.4 28.8 7.6 L 7 EXAMPLE CASTING

CURING

CATALYST/

CURING

TEMP.

YELLOWNESS

INDEX

(1.8 mm)

THICK

PLANO LENS

TRANS-

MISSION

TABER

ABRAS ION 200 CYCLES W 500 GMS

LOAD

0- H-AZE

BARCOL

SHRINKAGE

CALCU.

MONOMER

VALUES

0k

HARDNFRR

NUMBER MATERIAL INITIATOR AND TIME 21. 50% 9G 0.1% SIP U-4H

TMPT

6G 0.1% SIP U-4H

TMPT

9G 0.1% SIP U-4H

ETMPT

9G 0.1% SIP U-4H

ETMPT

60% 9G 0.1% SIP

ETMPT

U-4HA 40-900 5 hours 0 .83 92.5 40.2 7.6 40-900 5 hours 1.20 92.4 46.4 9.2 40-90 0 5 hours 0.94 92.6 43 .6 40-900 5 hours 1.06 92. 6 34 .8 9.4 40-900 5 hours 0.93 92.8 12.9 6.2 a 6 #UW e 0 00 00 0 0 0* 0 0 0 4 *0 0 S S 6 0 0 a EXAMPLE CASTING NUMBER MATERIAL

CURING

CATALYST!

CURING

TEMP.

YELLOWNEVSS

INDEX

(1.8 mm)

THICK

PLANO LENS

TRANS-

MISSION

TAB ER ABRAS ION 200 CYCLES W 500 GMS BARCOL LOAD HARDNESS HAZE

SHRINKAGE

CALCU.

MONOMER

VALUES

INITIATOR AND TIME 9G 0.1% SISP

ETMPT

U-4H 6G 0.1% SIP

ETMPT

U-4HA 6G 0.1% SIP

ETMPT

U-4H 40-900 5 hours 0.87 92.8 13 .1 11.3 40-900 5 hours 1.30 92.1 28.5 40-900 5 hours 1.27 92.5 31.0 8.7 29.* 40% U-6HA 0.1% SIP

ATMMT

9G 40% U-6HA 0.1% SIP

ATMMT

4G 4 0-9S 0 C 5 hours 0.90 92.3 39.8 4.7 40-900 5 hours 1.33 91-8 50.4 7.6

TABER

YELLOWNESS ABRASION SHRINKAGE INDEX 200 CYCLES CALCU.

CURING CURING (1.8 mm) W 500 GMS MONOMER EXAMPLE CASTING CATALYST/ TEMP. THICK TRANS- BARCOL LOAD VALUES NUMBER MATERIAL INITIATOR AND TIME PLANO LENS MISSION HARDNESS HAZE 31.* 40% U-6HA 0.1% SIP 40-90°C 1.53 91.6 51.6 9.1 ATMMT 5 hours 3G PEGM polyethylene glycol dimethacrylate with 9 polymerisation units of ethylene glycol U-4HA tetra functional urethaneacrylate of the general formula given above sold under the trade name by SHIN NAKAMURA TMPT trimethyol propane trimethacrylate SIP Secondary Isopropyl Percarbonate 3G polyethylene glycol dimethacrylate with 3 ethylene oxide units.

4G polyethylene glycol dimethacrylate with 4 ethylene oxide units.

23G polyethylene glycol dimethacrylate with 23 ethylene oxide units.

NF201 aliphatic urethane dimethacrylate produced by Mitsubishi Rayon Corporation NF202 aromatic urethane dimethacrylate produced by Mitsubishi Rayon Corporation U-6HA urethane oligomer from Shin Nakamura with 6 polymerizable groups per molecule.

6G polyethylene glycol dimethacrylate with 6 ethylene oxide units U-4H aliphatic urethane tetramethacrylate oligomer manufactured by Shin Nakamura ETMPT ethoxylated trimethylolpropane trimethacrylate ATMMT pentaerythritol tetraacrylate Examples 29-31 have unacceptably high viscosities of 1110, 582 and 446 cp (25 C) respectively.

i i u i n i I I i I l i i The above examples demonstrate that lenses cast in accordance with the method of the present invention have an abrasion resistance of the same order as a lens cast from diethylene-glycol bis (allyl carbonate) which has been coating with an abrasion resistant coating. It can be seen from Example 5, that the absence of the u.rethane acrylate gave a product with a low level of hardness measured on the Barcol scale. Such flexible lenses may provide useful products in the safety field. The unacceptability of a 1 Q difunctional acrylate in combination with a polyethylene glycol dimethacrylate and TMPT is demonstrated by comparison of Examples 4 and 6. All significant characteristics of the lens made in accordance with the invention can be seen to be equivalent or superior to a lens cast from diethylene glycol bis (allyl carbonate).

The following examples illustrate how the relevant proportions of the polyethylene glycol monomer and the urethane monomer can affect the viscosity of the monomer mixture used for casting lenses: Monomer Mixture Viscosity at by weight CPS at 25 Degrees C PEGM U-4HA TMPT 1. 70 10 20 52.4 2. 65 15 20 63.7 3. 60 20 20 76.8 4. 55 25 20 96.6 50 30 20 123.9 6. 40 40 20 207.9 7. 30 50 20 377.7 8. 20 60 20 796 It can be seen that the compositions which are outside the scope of the invention have a viscosity which would render casting difficult.

It will be appreciated that various modifications and/or alterations may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the present invention.

20 b 1 1

Claims (16)

1. A cross-linkable polymeric casting composition including at least polyoxyalkylene glycol diacrylate or dimethacrylate, at least one polyfunctional unsaturated cross-linking agent and a urethane monomer having from 2 to 6 terminal acrylic and/or methacrylic groups.

2. A casting composition according to claim 1 wherein the diacrylate or dimethacrylate compound includes ethylene oxide or propylene oxide repeating units in its backbone.

3. A casting composition according to claim 2 wherein the diacrylate or dimethacrylate compound includes 6 to 11 ethylene oxide repeating units in the backbone thereof. S4. A casting composition according to claim 3 wherein the diacrylate or dimethacrylate compound is a SC polyethylene glycol dimethacrylate with an average molecular weight of about 600. A casting composition according to claim 2 wherein the diacrylate or dimethacrylate compound is present in Sc amounts of from 40% by weight to 60% by weight based on the total weight of the casting composition.

6. A casting composition according to any one of claims C 1 to 5 wherein the ratio of said cross-linking agent to said urethane monomer is in the range of 1:4 to 2:1.

7. A casting composition according to any one of claims 1 to 6 wherein the urethane monomer is a tetracrylic iC urethane monomer.

8. A casting composition according to claim 7 wherein the polyfunctional unsaturated cross-linking agent is a tri- or tetrafunctional vinyl, acrylic or methacrylic monomer.

9. A casting composition according to claim 8 wherein the polyfunctional unsaturated cross-linking agent is selected from trimethylol propane trimethacrylate, pentarethritol triacrylate or pentarethritol tetracrylate. pA, I* -22- A casting composition according to claim 9 wherein the polyfunctional unsaturated cross-linking agent is present in amounts from 10 to 30% by weight based on the total weight of the casting composition.

11. A casting composition according to claim 10 wherein the urethane monomer is a tetracyclic urethane monomer of the formula: R R R =C 2_1_ 2_ R 0 R CR2-COOCR -C CR -OCO-C=CR 1 3 wherein R, R R and R which may be the same or different are selected from hydrogen, alkyl of 1 to 6 carbon atoms or a substituted alkyl of 1 to 6 carbon atoms; and X is an organic residue having 1 to 20 carbon atoms.

12. A casting composition according to claim 11 wherein X is selected from C 1 -C 20 alkyl, alkoxy, alkylamino, alkyl carbonyl alkoxy carbonyl, alkylamido or alkoxy amide group; which may be substituted or unsubstituted with one or more halogen, hydroxyl, nitro, amino, alkyl or alkoxy groups.

13. A casting composition according to claim 12 wherein the tetracrylic urethane monomer is present in amounts of from 0 to 40% by weight based on the total weight of the caLting composition. LU; *j ly. -23-

14. A casting composition according to claim 13 wherein the urethane monomer is a compound of the formula R R CH 2 =C-COOCH2-CH-CH 2 -OCO-C=CH 2 O NH x NH CO R O R CH 2 =C-COOCH2=CH-CH 2 -OCO-C=CH2 wherein R is a hydrogen atom or a methyl group or a substituted methyl group and X is an organic residue having 2 to 20 carbon atoms.

15. A casting composition according to any one of claims 2 1 to 14 further including a heat and/or ultraviolet 4 cross-linking initiator.

16. A casting composition according to claim 15 wherein the cross-linking initiator is selected from\qE....y.--anj 1,1 di-tert butyl peroxy trimethylcyclohexane or secondary isopropyl percarbonate.

17. A polymeric article formed from a cross-linkable polymeric casting composition according to claim 1.

18. A polymeric article according to claim 17 wherein the article is an optical article.

19. An optical lens having a viscosity not greater than 200 cps at 25 0 C and having increased hardness, said optical lens being formed from a cross-linkable polymeric casting composition including at least one polyoxyalkylene glycol diacrylate or dimethacrylate; at least one polyfunctional unsaturated cross-linking agent; and a tetracyclic urethane monomer. A cross-linkable polymeric casting composition comprising: at least polyoxyalkylene glycol diacrylate or dimethacrylate compound; P, L C.7 t k s* I -24- at least one polyfunctional unsaturated cross-linking agent; and a urethane monomer having from two to six terminal acrylic and/or methacrylic groups; wherein a weight ratio of said cross-linking agent to said urethane monomer is in the range of from approximately 1:4 to 2:1. A polymeric casting composition according to claim 1 substantially as hereinbefore described with reference to any one of the examples. DATED: 9 May, 1990 PHILLIPS ORMONDE FITZPATRICK v s e Attorneys for:- SOLA INTERNATIONAL HOLDINGS LTD. rl P ne r r 4441 '44 44 4 LIT