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Title:
HYDROPHILIC,SOFT AND OXYGEN PERMEABLE COPOLYMER COMPOSITIONS
Document Type and Number:
WIPO Patent Application WO/1980/000253
Kind Code:
A1
Abstract:
A new composition of matter specially adapted for the production of contact lenses, artificial eyes or other prosthetic devices. The composition has the characteristics of increased hydrophilicity, softness after hydration and oxygen permeability. The composition is a solid copolymer of comonomers consisting essentially of about 15 to about 65 parts by weight of one or more of the hydrophilic amide group containing monomers and about 10 to about 75 parts by weight of one or more of the copolymeric organosiloxane. Optionally, about 0.1 to about 65 parts by weight of at least one property modifier, a vinyl group containing monomer such as methyl methacrylate, can be employed into the copolymers. The inventive material is optionally transparent, translucent or opaque depending on the type, composition and relative content of the comonomers used. In general, the transparent composition is suitable for use in making contact lenses.

Inventors:
CHANG S (US)
Application Number:
PCT/US1979/000441
Publication Date:
February 21, 1980
Filing Date:
June 14, 1979
Export Citation:
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Assignee:
CHANG S
International Classes:
G02C7/04; C08F20/52; C08F26/00; C08F26/10; C08F30/00; C08F30/08; C08F220/54; C08F220/56; C08F226/06; C08F226/10; C08F230/08; C08F283/12; C08F290/00; C08F290/06; C08F299/08; G02B1/04; (IPC1-7): C08F26/08; C08F20/06; C08F30/08; C08F230/08
Foreign References:
US3808178A1974-04-30
US3849238A1974-11-19
US3948871A1976-04-06
US4099859A1978-07-11
US4120570A1978-10-17
US4138382A1979-02-06
US4139513A1979-02-13
US4153641A1979-05-08
GB1480880A1977-07-27
Other References:
See also references of EP 0016138A4
Download PDF:
Claims:
WHAT IS CLAIMED IS:
1. A composition of matter specially adapted for use as a prosthetic device having the characteristics of increased hydrophilicity, softness after hydration and oxygen permeability, said composition being a copolymer of comonomers consisting essentially of: (A) about 15 to about 65 parts by weight of at least one amide group containing monomer being selected from a group consisting essentially of: (a) heterocyclic amide group containing monomers consisting essentially of: (1) N(olefin containing group)2pyrrolidone, (2) N(olefin containing group)2piperidone, (3) N(olefin containing group)2imidazolidone, and (4) N(olefin containing group) succinimide, wherein said olefin containing group is select¬ ed from a group consisting essentially of vinyl, acryloxy, methacryloxy, acrylatoalkyl, methacry latoalkyl, acrylamidoalkyl and methacrylamido alkyl groups, wherein the alkyl group contains from one to 4 carbon atoms, and (b) noncyclic amide group containing monomers consis ting essentially of Nalkyl acrylamide, Nalkyl methacrylamide, N,Ndialkyl acrylamide and N,N dialkyl methacrylamide, wherein the alkyl group is individually selected from a group consisting of unsubstituted and substituted monovalent hydrocarbon radicals having from one to 6 carbon atoms, and (B) about 10 to about 75 parts by weight of at least one organosilicon compound, wherein the essential consti¬ tuent units of each molecular compound have the formulas: M, CH9*CRCOO(CH9 ) R' SiO, _ and N ' R"bsi04b 2 .
2. wherein the molar ratio of M to N is within a range of from about 1 to 99 to about 99 to 1; R is selected from a group consisting of hydrogen and methyl group; R' and R", which may be the same or different, are monovalent hydrocarbon groups selected from a group consisting of CJC alkyl groups, cyclohexyl groups and phenyl groups; n is an integer of o one to four inclusive; a is an integer of from 0 to 2 inclusive and b is an integer of from zero to three inclusive.
3. 2 The compositionof Claim 1, wherein said amide group containing monomer being selected from a group consisting essentially of Nvinyl2pyrrolidone, N(2 methacrylato ethyl) pyrrolidone, Nvinyl2piperidone, N(2'metha crylatoethyl)2piperidone, Nalkyl acrylamide, Nalkyl methacrylamide, N,Ndialkyl acrylamide, N,Ndialkyl metha¬ crylamide and mixture thereof.
4. The composition of Claim 1, wherein there is about 20 to about 55 parts by weight of at least one amide group containing monomer and about 20 to about 55 parts by weight of at least one organosilicon compound.
5. The composition of Claim 3t wherein said prosthetic device is a contact lens device.
6. The composition of Claim 4, wherein there is about 25 to about 45 parts by weight of at least one amide group containing monomer.
7. The compositionof Claim 5. wherein said amide group containing monomer is Nvinyl2pyrrolidone.
8. The composition of Claim 5* wherein said amide group containing monomer is N(2'methacrylatoethyl)2pyrroli done.
9. The composition of Claim 5* wherein said amide group containing monomer is N,Ndimethyl methacrylamide. BUREAU OΛ.PI /[_. W1PO .
10. A composition of matter specially adapted for use as a prosthetic device having the characteristics of increased hydrophilicity, softness after hydration and oxygen permeability, said composition being a copolymer of comonomers consisting essentially of: (A) about 15 to about 65 parts by weight of at least one amide group containing monomer being selected from a group consisting essentially of: (a) heterocyclic amide group containing monomers consisting essentially of: (1) N(olefin containing group)2pyrrolidone, (2) N(olefin containing group)2piperidone, (3) N(olefin containing group)2imidazolidone, and (4) N(olefin containing group) succinimide, wherein said olefin containing group is selected from a group consisting essentially of vinyl, acryloxy, methacryloxy, acrylatoalkyl, methacry latoalkyl, acryla idoalkyl and methacrylamidoal kyl groups, wherein the alkyl group contains from one to 4 carbon atoms, and (b) noncyclic amide group containing monomers consist ing essentially of Nalkyl acrylamide, Nalkyl methacrylamide, N,Ndialkylacrylamide and N,N dialkylmethacrylamide, wherein the alkyl group is individually selected from a group consisting of unsubstituted and substituted monovalent hydrocarbon radicals having from one to 6 carbon atoms; (B) about.
11. to about 75 parts by weight of .at least one organosilicon compound, wherein the essential consti¬ tuent units of each molecular compound have the formulas: wherein the molar ratio of M to N is within a range o from about 1 to 99 to about 99 to 1; R is selected OΛ from a group consisting of hydrogen and methyl group; R* and R", which may be the same or different, are monovalent hydrocarbon groups selected from a group consisting of C^C^ alkyl groups, cyclohexyl groups and phenyl groups; n is an integer of from one to four inclusive; a is an integer of from 0 to 2 inclusive and b is an integer of from zero to three inclusive; and (C) about 0.1 to about 65 parts by weight of at least one ester of a C,C20 alkanol and an acid selected from a group consisting of acrylic and methacrylic acids.
12. 10 The composition of Claim t wherein there is about 20 to about 55 parts by weight of at least one amide group containing monomer and about 20 to about 55 parts by weight of at least one organosilicon compound, the said amide group containing monomer is selected from a group consisting essentially of Nvinyl2pyrrolidone, N(2' methacrylatoethyl)2pyrrolidone, Nvinyl2piperidone, Nalkyl acrylamide, Nalkyl methacrylamide, N,Ndialkyl acrylamide, N,Ndialkyl methacrylamide and mixture thereof.
13. A composition of matter specially adapted for use as a contact lens device having the characteristics of increa¬ sed hydrophilicity, softness after hydration and oxygen permeability, said composition being a copolymer of comonomers consisting essentially of: (A) about 20 to about 45 parts by weight of at least one amide group containing monomer being selected from a group consisting essentially of Nvinyl2pyrroli¬ done, N(2'methacrylatoethyl)2pyrrolidone, Nmeth yl acrylamide, Nmethyl methacrylamide, N,Ndimethyl acrylamide and N.Ndimethyl methacrylamide; (B) about 10 to about 50 parts by weight of at least one organosilicon compound, wherein the essential consistituent units of each molecular compound have the formulas: M, CH 2 ) n R' a SiO, 3a a and 2 N » R"bSi04b wherein the molar ratio of M to N is within a rang of about 1 to 99 to 99 to lj R is selected from a group consisting of hydrogen and methyl group; R* and R", which may be the same or different, are monovalent hydrocarbon groups selected from a grou consisting of C,C^ alkyl groups, cyclohexyl groups and phenyl groups; n is an integer of from one to four inclusive; a is an integer of from 0 to 2 inclusive and b is an integer of from zero to three inclusive; and (C) 0 to about 35 parts by weight of at least one ester of a C,C20 alkanol and an acid selected from a group consisting of acrylic and methacrylic acids.
Description:
THE DESCRIPTION OF INVENTION HYDROPHILIC. SOFT AND OXYGEN PERMEABLE COPOLYMERCOMPOSITIONS

FIELD OF INVENTION

This invention relates to novel copolymer composi¬ tions, and more particularly to hydrophilic, soft after hydra- tion and oxygen-permeable copolymers.

THE PRIOR ART AND BACKGROUND OF THE INVENTION

The basic requirements for polymeric materials in some areas of medical application are that they be hydrophilic, soft and oxygen-permeable. The prior art teaches the use of many different polymeric materials in these areas such as in contact lenses, intraocular lens and other prosthetic devices. Although these polymers possess certain desirable properties for their specific medical application, they suffer from other undesirable characteristics which reduce their utility.

In contact lens area, the hard lens material, poly- methyl methacrylate (PMMA), is durable but relatively imper¬ meable to oxygen and further suffers from being rigid and hydrophόbic. The hydrogel contact lens based on hydrophilic polymers such as polyhydroxyethyl methacrylate (Poly HΞMA) are soft but with poor durability and dimensional stability. It also does not have enough oxygen permeability.

Another polymeric material is silicone rubber, one kind of polysiloxane, which can also be used in contact lens and other prosthetic devices. Although it is soft, resilient and is highly gas permeable, it is hydrophobic.

Accordingly, it would be highly useful and desirable in medical applications to provide a polymeric material having increased hydrophilicity, softness after hydration, and oxygen permeability. As compared to the hard lens material, PMMA, the copolymers taught in the patent to Gaylord, ϋ. S. Patent No. 3,808,178, for contact lens fabrication have relatively high oxygen permeability, but suffer from being rigid and relatively hydrophobic. Although in Examples 3 to 9 of the

patent, Gaylord teaches the use of 5 to 9 percent by weight of HEMA (hydroxyethyImethacr late) to increase the wettabilit of the copolymer. The copolymers prepared therefrom can only absorb water up to about 1% ' of its weight. It is still relatively rigid and hydrophobic. If a larger amount of this hydrophilic monomer is used in the compositions as claimed in the Gaylord patent, different defects would occur, such as, the comonomer mixture would become incompatible! the copolyme prepared therefrom could become heterogeneous, brittle, lack¬ ing of strength or opaque; or the hardness of the copolymer is essentially unchanged even after hydration because the material is relatively hydrophobic. Similar difficulties would result with the use of other hydrophilic monomers as taught in column , lines 53 "to 62 of the Gaylord patent. Therefore by following Gaylord's teaching to use about 0.1 to about 10 of hydrophilic monomers to improve the wettability of the copolymers as described, we still could not make the material of the present invention which has increased hydro- philicity, softness after hydration and oxygen permeability for the fabrication of contact lenses or other prosthetic devices. In search of such a material, I unexpectedly disco¬ vered a novel copolymer material which possesses these highly useful properties.

The novel copolymers which I have discovered are prepared by essentially c©polymerizing the copolymeric organo- siloxane with the hydrophilic amide group containing monomer (hereafter, HAGM). One of the novel properties of these copolymers is illustrated in Fig. 1 which shows the effects o different amounts of hydrophilic monomers in the comonomeric compositions upon the hydrophilic properties of the copolymers prepared therefrom. The latter is expressed in the percent by weight of water absorption as defined in Examples 10-16 of this specification. Fig. 1 also shows the comparison of hydro philic properties of the copolymers prepared in the present invention and in the Gaylord patent. Curve A of Fig. 1 is the general trend of the hydrophilic properties of the materials prepared in this invention, curve B is the general hydrophilic trend of Gaylord's copolymers in which about 0.1 to about 10$ of hydrophilic monomeric material can

be used and curve G is a prior art projection when HEMA rela¬ ted monomers are used as the hydrophilic monomer in the como- nomeric mixture. It appears that the hydrophilic properties of the copolymers of the present invention, curve A, are substantially higher than those of the Gaylord materials, cur¬ ve B, and also substantially higher than those of prior art pro . iection, curve C. In addition, as described previously these copolymers of curve C would have other shortcomings.

In order to support the unobviousness of the present invention, a comparison of optical characteristics between those of the instant invention and those of the closest prior art, the Gaylord patent and its projection is summarized in Table I, which shows that according to the prior art projec¬ tion, if the amount of HEMA used in the composition is about or larger than 15$ by volume of the composition, the copolymer obtained is opaque - a characteristic being not desirable for contact lens application. However, when a corresponding amount of VP (vinyl pyrrolidone) to that of HEMA is used in the composition, the copolymer obtained in the instant appli¬ cation is transparent - a characteristic being desirable for contact lens application.

TABLE I. Comparison of the Unobvious Optical Characteris¬ tic of the Compositions of the Instant Invention to Those of the Prior Art Composition, the Gaylord Patent and Its Projection.

Example Comment and Optical

Si VP C HEMA d MMA e # Properties

1 50 9 41 T, The Prior Art

2 50 15 35 0t The prior art

3 50 17 33 0 pro.lection, opaque 50 20 30 0

5 50 35 15 0

6 50 9 l T

7 50 15 35 T, The .instant appli¬

8 50 17 33 T cation, transparent 9 50 20 30 T

10 50 ~ 1> 1$ T

OMPl

^he composition (volume$) were prepared by following the general procedure as described in the Example 2-9 of the instant application. b Si p was prepared in Example 1 of the specification.

C VP = N-vinyl pyrrolidone

HEMA = 2-hydroxyethy1 methacrylate e MMA = methyl methacrylate

■ Based on the visual observation to the composition rods about 11 mm in diameter. 0 = opaque; T = transparent.

As a matter of fact, Gaylord limited the use of hydrophilic monomers to improve the wettability of his copolymer to a narrow range of from about 0.1 to about 10$ by weight only as shown in curve B of Fig. 1.

In addition, I have also discovered that not every percentage range of HAGM can be used in the composition of thi invention, the useful range of HAGM as indicated in the curve A of Fig. 1 is only limited within the general range from abou 15 to about 65 and most preferably from about 25 to about 5 percent by weight. Another novel and useful property of my invented material is that it becomes increasingly soft after hydration while the hardness of Gaylord's material is essen¬ tially unchanged after hydration. An example of this is illustrated in Example 17 in the specification of this inven¬ tion.

I also discovered that my claimed composition has the characteristics of increased oxygen permeability. The oxygen permeability of my invention as illustrated in Example 18 of this specification is about 1,600 c.c.-mil/lOO in 2 /24 h /atm whereas those as illustrated in the examples of the Gaylord patent are between 300 and 500 units only.

With these novel properties as described above, the composition of this invention is highly useful in a number of medical applications. For contact lenses, this material provides a combination of properties that are close to an idea combination ofproperties of the best features of the hard lens material, PMMA, soft lens material, Poly HEMA, silicone rubber and the Gaylord copolymer lenses, For other prosthetic device

features such as increased hydrophilicity, softness after hydration and gas permeability are also very useful and desir¬ able.

DISCLOSURE OF THE INVENTION

The invention relates to a new composition of matter specially adapted for the making of contact lenses, artificial eyes or other prosthetic devices.

An object of the invention is to provide a new and useful composition for medical prosthetic devices. Another object of the invention is to provide increased hydrophilicity, softness after hydration and oxygen permeability for hard contact lens composition.

Still another object of the invention is also to provide for increasing the oxygen permeability of soft lens compositions.

Yet another object of the invention is to provide increased hydrophilic, soft after hydration and oxygen-perme¬ able compositions.

The novel copolymers which are disclosed are prepar¬ ed by essentially copoly erizing the amide group containing monomers with copolymeric organosiloxane. Particularly effec¬ tive for this invention is a copolymer composition consisting essentially of:

(A) about 15 to about 65 1 preferably about 20 to about 55 and most preferably about 25 to about 45 weight per¬ cent of at least one of the hydrophilic amide group containing monomers;

(B) about 10 to about 75ι preferably 20 to 55 and most preferably 25 to 45 weight percent of at least one copolymeric organosiloxane; and

(C) optionally, about 0.1 to about 65 parts by weight of at least one ester of a C,-C 20 alkanol and an acid selected from a group consisting of acrylic and methacrylic acids.

The typical amide group containing monomers that are suitable for the practice of this invention must be hydrophilic and must contain a carbonyl functionality adjacent to the

nitrogen, which can be either in the heterocyclic ring or in the noncyclic structure. In addition, such monomers must contain a polymerizable olefin containing group (hereafter, G), such as vinyl, acryloxy and methacryloxy groups (CHg^C -^- C00-), acrylatoalkyl and methacrylatoalkyl groups (CH 2 =CR^- C00(CH 9 ) -), acrylamido and methacrylamidoalkyl group (CH 2 =CR 1 C0NH(CH 2 ) -), wherein R^ is either hydrogen or methyl group, m is an integer of from one to 4. Preferably G is bonded to the nitrogen atom of the amide group. ,The suitable heterocyclic amide containing groupof the monomer is preferab ly selected from a group consisting essentially of pyrrolidon piperidone, imidazolidone and succinimide. It is understood that these amide containing group may be substituted in the heterocyclic ring by one or more of low alkyl groups such as methyl, ethyl and the like. The suitable noncyclic amide group containing monomer is preferably selected from a group consisting essentially of N-alkyl or N,N-dialkyl acrylamide and methacrylamide, wherein each alkyl group is individually an unsubstituted monovalent hydrocarbon radical having one to 6 carbon atoms or a substituted monovalent hydrocarbon radica having,.'one to 6 carbon atoms wherein the substituent may be selected from a group consisting of amino, alkoxy, carbonyl and hydroxy groups. It is understood of course that mixtures of such heterocyclic and noncyclic monomers can be employed i preparing the copolymers of the present invention.

The preferred heterocyclic monomers employed are N-vinyl lactams of which N-vinyl-2-pyrrolidone is the most preferred, and the preferred noncyclic monomers employed are N,N-dialkyl methacrylamide of which N,N-dimethyl methacrylamid is the most preferred.

The copolymeric organosiloxanes that are suitable for the practice of this invention fall within the general acrylated or methacrylated organosilicon compounds. The essential constituent unitsof each molecular compound have the formulas.

M, » 3, SiO- _-} x~m a _- and

N ' R "b si0 4-b 2

2

( O PI

wherein the molar ratios of M to N are in the range of from about 1 to 99 to about 99 to 1, more particularly from about 1 to 50 to about 50 to 1 and most particularly from about 1 to 20 to about 20 to 1; R is selected from a group consisting of hydrogen and methyl group; R' and R", which may be the same or different, are monovalent hydrocarbon groups selected from a group consisting of C-^-C^ alkyl groups, cyclohexyl groups and phenyl groups; n is an integer of from one to four inclu¬ sive; a is an integer of from 0 to 2 inclusive and b is an integer of from zero to three inclusive.

The term of "molar ratio" is not used herein as based upon the actual molecular weight of the copolymer per se, but rather as based upon the molecular weight of the unit or average molecular weight of the units which are present in such copolymer, as is the common practice in the polymer chemistry.

The defined copolymeric siloxane can contain either one or two of such monovalent hydrocarbon radicals attached to any given silicon atom. The R' amd R"groups attached to the individual silicon atoms can be the same or different radicals. The copolymeric organosiloxanes prepared can themselves con¬ tain the Si0 2 ι SiO, R"Si0, _. _ or R" SiO ς siloxane units and with any desired variation of R" radicals attached to silicon atoms, as long as they are liquid so that intimate contact can be made with the amide group containing monomers and other monomers.

The general procedures to synthesize the.above defined copolymeric organosiloxane which is suitable for the practice of this invention are well known in the art of sili- cone chemistry. One of the preferred methods is to react the corresponding chloromethyl substituted organosilicon compounds with a triethylamine salt of either acrylic or methacrylic acid as illustrated in Example 1 of this specification. As is well known in the art, the chloromethyl substituted organo¬ silicon compounds employed as intermediates in the above pre¬ parations may themselves be prepared by halogenating armethyl trihalosilane and subjecting the product to reaction with a Grignard reagent to replace some or all of the silicon bonded halogen atoms, followed if desired by the hydrolysis of the

unreacted silicon bonded halogen atoms to produce the corres¬ ponding siloxane.

Alternatively, the defined copolymeric organosilo- xanes can be prepared by means of the well known acid catalyz¬ ed siloxane condensation methods. One of the preferred method is to react r-methacryloxypropyltrimethoxysilane with trimethy acetoxysilane or other corresponding ρ.cetoxysiloxanes as illustrated in Example 1 herein, and the other method is to mix the acrylated or methacrylated organosiloxane as specified previously with the organosiloxane as defined in formula N in the desired ratio and the mixture heated in the presence of an acid catalyst such as concentrated sulfuric acid. The acid catalyst is preferably present in an amount of from 0.5 to 3 percent by weight based upon the weight of the combined reactants. This type of reaction proceeds at room temperature but is preferably speeded up by heating the mixture at a highe temperature. Obviously, in order to prepare a mono- or multi- acrylated or methacrylated copolymeric organosiloxane which is suitable for the practice of this invention, the above mention ed methods can be properly combined to use, such as those des¬ cribed in the U. S. Patent No. 2,956,θ44.

Optionally, the physical properties of the copoly¬ mers in this invention can be modified by copolymerizing the composition mixture with one or more of vinyl group contain¬ ing monomers. For example, if desired, in order to increase the strength, hardness, or in some cases to improve the optical properties or to act as additive of the copolymers, about 0.1 to about 65. preferably 5 to 50 and most preferably 15 to 35 parts by weight of one or more of the vinyl group containing monomers or an ester of a alkanol and an acid selected from a class consisting of acrylic and metha- crylic acids, such as methyl methacrylate, ethyl acrylate and methacrylate, butyl acrylate and methacrylate, amyl acrylάe and methacrylate, hexyl acrylate and methacrylate, octyl acrylate and methacrylate, 2-ethylhexyl acrylate and methacrylate, decyl acrylate and methacrylate, lauryl acryl¬ ate and methacrylate, octadecyl acrylate and methacrylate, and the like, can be incorporated into the materials by the

technique of copolymerization.

The rigidity of the copolymer in this invention can also be improved, if desired, by incorporating into the material with about 0.1 to about 20, preferably about 0.1 to about 5 parts by weight of one or more of the vinyl group containing crosslinking monomers. Representative of cross- linking monomers which are suitable for the practice of this invention are polyol dimethacrylate or diacrylate or a polyol acrylic or methacrylic ester of higher functionality, for example, mono-, di-, tri-, or tetraethylene glycol dimethacryl¬ ate, butylene glycol dimethacrylate, neopentyl diacrylate andpentaerythritol triacrylate or tetracrylate and the like.

The copolymers of the invention are prepared by contacting the mixture of comonomers with a free radical generating polymerization initiator of the type commonly used in polymerizing ethylenically unsaturated compounds. Repre¬ sentative free radical polymerization initiators are organic peroxides, such as acetyl peroxide, lauroyl peroxide, decano- yl peroxide, stearoyl peroxide, benzoyl peroxide, tertiary- butyl peroxypivalate, acetyl peroxy isobutyl carbonate and the like. Other catalysts, such as β.,tf-azobisisobutyroni- trile, can also be used. Alternatively, in certain cases the mixture of the comonomers can also be polymerized by radiation initiated polymerization. Conventional polymeriza¬ tion techniques can be employed to produce the novel copoly¬ mers. The comonomer mixture containing the free radical initiator, generally from about 0.01 to about 5 and prefer¬ ably between 0.05 to 2 percent by weight, is heated to a temperature of from about 45°C to 100°C or even higher but preferably between 45°C to 70°C. , to initiate and complete the polymerization.

The polymerization can be carried out directly in a mold with the desired configuration such as for contact lenses. Alternatively, the polymerization mixture can be heated in a suitable mold or container to form discs, rods, sheets or other forms which can then be fabricated into the desired shape using conventional equipment and technology well known in the art. Instead of employing the bulk poly-

O PI v*V W1P0

merization techniques described above, one can employ solu¬ tion, emulsion or suspension polymerization to prepare the novel copolymers, using techniques conventionally used in the preparation of polymers from ethylenically unsaturated mono¬ mers. The copolymer thus produced may be extruded, pressed or molded into rods, sheets or other convenient shapes which are then machined to produce a contact lens or other prosthe¬ tic devices. The inventiye copolymers can also be tinted as known in the art.

The inventive copolymer is optionally transparent, translucent or opaque depending on the type, composition and relative content of the comonomers used. Generally speaking, the transparent product is suitable for contact lens fabrica¬ tion.

The novel copolymers have vastly increased hydrophi- licity in comparison to the corresponding copolymers taught in U. S. Patent No. 3,808,178, the conventional hard lens materia polymethyl methacrylate (PMMA), or silicone rubber used in medical applications. For example, a copolymer comprising 45$ by volume of N-vinyl pyrrolidone, 25$ by volume of copoly¬ meric organosiloxane, Si, prepared in Example 1 of this specification and 30$ by volume of methyl methacrylate (MMA) as---taught in this invention can absorb water or hydrate up to about 26$ of its weight, whereas the hard lens material, PMMA, and the copolymer with the composition of 25$ of Si, and 75$ of MMA as taught in the above mentioned patent can only be hydrated up to about 0.5$ of the weight. If the wettability of the copolymer is improved by the addition of up to about 10$ of hydrophilic HEMA in the comonomeric mixture as describ¬ ed in Examples 3-9 of the Gaylord patent, the hydration of the material prepared therefrom is also only about 1$. The sili¬ cone rubber is essentially hydrophobic.

In addition, the novel copolymers taught in this invention have vastly increased softness after hydration. For example, in the above mentioned examples before hydration the hardness of the material taught in this invention is at about 75 as measured by Portable Hardness Tester, Model GYZJ 936, Barber-Colman Co., 111., but after fully hydrated, it

/-BURE f OMP

becomes about 15; whereas the others still keep at about original value, PMMA at about 93 and the others at about 80. Generally the degree of softness of the copolymer after hydra¬ tion in this invention depends on the degree of its hydrophi- licity. The higher the content of the hydrophilic comonomer in the copolymer, the higher the degree of its hydrophilicity and the softer the lens is after hydration. In the practice . of this invention it is preferred to select the copolymer with percent of hydration between about 8 toabout 35$.

Furthermore, the novel copolymers have also vastly increased gas permeability in comparison to conventional contact lens materials, PMMA, and soft lens material, poly HΞMA. For example, a copolymer comprising 30 parts by volume of N-vinyl pyrrolidone, 50 parts of Si, and 20 parts of MMA

_? has an oxygen permeability of about 1,600 c.c.-mil/100 in /

24 hrs/atm compared to an oxygen permeability of about 30 for PMMA and about 15 for Poly HEMA as described in the Gaylord patent. The oxygen permeability values of the Gaylord copo¬ lymers illustrated in the examples of the Gaylord patent are between 300 and 500 units only. These oxygen permeability values were determined in accordance with ASTM D1434. The substantially increased oxygen permeability of- the composi¬ tions of this invention could be due to the synergistic effect of the components used.

In the practice of this invention in contact lens area, the refractive index is an important but noncritical characteristic. Thus, the refractive index of polymethyl methacrylate, the polymer most widely used in the fabrication of hard contact lenses, is 1.49. The refractive indices of the copolymers useful in the practice of this invention in the fabrication of contact lenses are preferably selected between about 1.4 and about 1.5 which may be varied by chang¬ ing the ratio and nature of the comonomers used.

BRIEF DESCRIPTION OF THE DRAWING

The difference between the hydrophilic properties of the copolymers of this invention and those of the closest

OMPI

prior art, the Gaylord copolymers, will become even further apparent upon the consideration of the following disclosure of this invention, particularly when taken in conjunction with the accompanying drawing, Fig. I, wherein the variation of hydrophilic properties of the copolymers are illustrated with respect to the percentage change by volume of the hydrophilic monomers used in the comonomeric mixture. Curve A is the present invention; B is the prior art; and C is the prior art projection, when HEMA related monomers are used.

BEST MODΞ FOR CARRYING OUT THΞ INVENTION

The following examples are presented to illustrate the practice of the invention and not as an indication of the limits of the scope thereof.

EXAMPLE I

This example illustrates some general procedures to synthesize the copolymeric organosiloxanes that are suit¬ able for the practice of this invention by the methods well known in the art,

Organosilicon Compounds 1 and 2, Si, and Sig

The synthesis procedures of these compounds are essentially the same as that described in Example 15. U. S. Patent No. 3,808,178

23.8 g. (13 ml) of concentrated sulfuric acid is added slowly with stirring to a mixture of 11.6 g. (14.7 ml) of absolute ethanol and 16.5 ml of water. The mixture is cooled in a water bath.

|"-Methacryloxypropyltrimethoxysilane (0.1 mole, 24.8 g. ) ismixed with 0.3 mole (39.6 g. ) of trimethylacetoxy- silane prepared from tri ethylchlorosilane by following the procedure which is described in the article, Journal of American Chemical Society, 74, 4584 (1952), in a flask equipp¬ ed with a magnetic stirrer. Ethylsulfuric acid (6.5g. )? prepared as described above, is added dropwise from a dropp¬ ing funnel into the stirred mixture. The flask is cooled

O

duringthe addition of the ethylsulfuric acid catalyst solution in an ice water bath. After completion of the catalyst addition, the solution is stirred at room temperature for two days. The upper oily layer is then separated, washed with water until neutral, decolorized with activated carbon if required, and then dried over anhydrous sodium sulfate. The produce is distilled under high vacuum to remove methyl acetate, dimer of silane, siloxane or other impurities. The distillation flask is immersed in a water bath whose tempera¬ ture is maintained between 4θ°C and 90°C, preferably at about 50° C, to facilitate the distillation. The yield of this organosilicon compounds (Si,) will be about 85$ and the materi¬ al is refrigerated until use.

The procedure described above can also be used to synthesize other corresponding organosilicon compounds, if trimethyl acetoxysilane used in the reaction is replaced by the other desired acetoxy siloxane, such as pentamethyl ace- toxydisiloxane, heptamethyl acetoxy trisiloxane and the like. Apparently, the higher the number of silicon in the acetoxy- siloxane used, the higher the vacuum and the higher the temperature of water bath, such as 80 or 90°C under high vacuum should be used in order to distill out the impurities. When pentamethyl acetoxydisiloxane is used in the reaction, the copolymeric organosilicon compound thus prepared is called si 2 .

Organosilicon Compound 3, Si,-,

The synthesis procedure of methacryloxymethylpenta- methyldisiloxane (Si,,) is fully described in Ξxample 1 of U. S. Patent No. 2,956,044 and Example 1 of U. S. Patent No. 3,808,178.

Other Organosilicon Compounds, Si^, Si.., Si^ etc.

The detailed procedures to synthesize these compounds are fully described in Examples 2,3,4 ani 5 of U. S. Patent No. 2,956,044.

EXAMPLES 2-9

The examples illustrate the preparations and proper¬ ties of the copolymers containing varying proportions of heterocyclic amide group containing monomer, e.g., N-vinyl-2-

pyrrolidone (VP), the first type of organosilicon compounds, with or without MMA and crosslinking monomers, e.g., tetraethylene glycol dimethacrylate (TΞGDM). Furthermo¬ re, they also illustrate that a prosthetic device can direct¬ ly be made from copolymerizing the composition mixture in a mold with a desired configuration.

The mixture of VP, Si- j^ or Si 2 with or without MMA, crosslinking agent, TEGDM, and with t-butyl peroxypivalate (t-BPP) (about 0.004 ml per ml of monomer mixture), after flushing nitrogen through the reaction mixture for 30 minutes, was polymerized in a glass tube at 50°C for about 48 hours, followed by placing at 100°C oil bath for another 24 hrs. After the tube was broken, they were all in the forms of rods. The composition and properties of the copolymers are collected in the following table. As indicated, all the rods are either transparent or opaque, hard and rigid before hydration which can be cut, machined, polished and finished to contact lenses or other prosthetic devices by the techniques well known in the art. The material should have increased softness after hydration and increased oxygen permeability.

Composition, Vol. Percent

#

Example VP si l si 2 MMA TEGDM Properties

2 33 67 0 0 H, T, R

3 50 50 0 0 H, Op. , R

4 5 25 30 0 H, T, R

5 4o 50 10 0 H, T, R

6 30 50 20 0 H, T, R

7 20 50 30 0 H, T, R

8 30 50 15 5 H, T, R

9 35 35 30 0 H, T, R

*

Properties before hydration: H= hard; T = transpar¬ ent; Op = opaque; and R = rigid

OM

EXAMPLES 10-16

The examples illustrate the hydrophilic properties of the novel copolymers.

A small piece of sample (about 0.1 cm width) was cut from the cylindrical rod prepared in the above examples, followed by immersing in water for about 18 hours. The hydro¬ philicity is expressed as percent of hydration which can be calculated by the following formula:

ΔW $ Hydration = — - X 100 wherein AW is the weight difference of the sample after and before hydration and Wt is the weight of the sample before hydration. The approximate value of the percent hydration of the copolymer is collected in the Table below:

Example # Sample # a $ Hydration

10 2 7 11 4 25 12 5 14

13 6 8 14 9 15

15 b 0.5 16 c 1

a The number indicates the example number from which the sample was prepared.

The sample being prepared from the copolymer of 50$ by weight of Si, and 50$ of MMA as taught in the patent to Gaylord, U. S. Patent No. 3,808,178.

-~\

The sample was prepared from the copolymer of 50$ by weight ofSi- j^ , 39$ of MMA and 11$ of HEMA. The HEMA was used to improve the wettability of the copolymer as taught in theGaylord patent.

EXAMPLE 17 This example illustrates the increased softness of the copolymers after hydration in this invention.

The hardness of the copolymer prepared in Example 4

"BUREAU

O PI

before hydration is about 72 as measured by the portable hardness Tester, Model GYZJ 936, Barber-Colman Co., 111., after hydration, it is about 15? whereas the hardness of hard lens material, PMMA, before hydration is about 90, after hydr¬ ation it is still at about 90. The hardness of the copolymer containing the corresponding composition with that prepared in Example 4, i.e., 25$ of Si-^ and 75$ of MMA by volume as taught in U. S. Patent No. 3,808,178, before hydration is about 80 after hydration it is still at about 80.

EXAMPLE 18

This example illustrates the gas permeability of the copolymers in this invention.

* The oxygen permeability of the copolymer prepared in Example 6 is about 1,600 c.c.-mil/lOO in /24 hrs/atm. in comparison to about 35 for hard lens material, PMMA, and about 15 for soft * lens material, Poly HEMA, which are described in the Gaylord patent. The oxygen permeabilities of the copo¬ lymers illustrated in the examples of the Gaylord patent are between 300 and 500 units only. These oxygen permeability values were determined in accordance with ASTM D1434.

Examples 19-25

These examples illustrate the preparations and properties of the copolymers containing different types of organosilicon compounds, e.g., Si, and Si 2 , and different types of the amide group containing monomers with heterocyclic and noncyclic structures, e.g., VP, N,N-dimethyl methacrylami¬ de (NNMA) and N,N-dimethylacrylamide (NNAA).

The cyclindrical rods can be prepared in the manner described in Examples 2-9 from the comonomeric mixture as list ed in the following table:

Composition, Vol. Percent

Example # NNMA NNA_ VP Si Si, MMA

19 30 30

20 40 30 30

21 30 20 50

22 20 50 30

23 30 40 30

24 15 30 35 20

25 40 35 25

The copolymers thus prepared can be used in the practice of this invention.

Obviously many other modifications and variations of the composition of this novel copolymer prepared therefrom, are possible in light of the teachings given hereinabove. It is, therefore, to be understood that, within the scope of the appended claims, the invention can be practiced other¬ wise than as specifically described.

INDUSTRIAL APPLICABILITY

The invention relates to a new composition of matter specially adapted for the making of contact lenses, artifi¬ cial eyes or other prosthetic devices.