Maleimide polymers and contact lenses from such polymers

Abstract: A maleimide polymer comprises units derived from a maleimide derivative represented by the following general formula (I): where R¹ is a hydrogen atom or a methyl group, and R² is an alkyl, alkenyl or aryl group, each of which groups is substituted by at least one organosiloxane group or fluorine atom, or comprises a copolymer of (1) a maleimide derivative represented by the formula (I) but in which R² may be hydrogen or any optionally substituted aliphatic hydrocarbon or aryl group with (2) an alkyl or fluoroalkyl methacrylate or an organosiloxy styrene- or organosiloxy-(meth)acrylic acid derivative. The polymer material may be formulated into contact lenses high in oxygen permeability and having good mechanical properties.

Description: This invention relates to maleimide polymer compositions and to contact lenses made from them. In recent years, polymers containing an organosiloxane substituted methacrylate such as tris(trimethylsiloxy)silylpropyl methacrylate or a modified polysiloxane as a component have been developed and used as materials for contact lenses with high oxygen permeability; see for example, JP-A-85-142324 and JP-A-79-24047. In particular, EP-A-0452098 discloses a silicone-containing acrylic block copolymer comprising units derived from (a) a vinyl or maleimide monomer and (b) a vinyl siloxane polymer. However, due to the hydrophobic nature of the siloxane constituent, these materials tend to exhibit repellency of lachrymal tears on the surface and to result in clouding of the lenses. Furthermore, as a result of the low inter-molecular interaction peculiar to the silicone constituent, they show poor creep characteristics and low impact strength as physical disadvantages. Moreover, when the copolymerization of comonomers consisting of a hydrophilic monomer with active hydrogen such as 2-hydroxyethyl methacrylate and the silicone monomers is carried out in order to modify the lens material by polymer reaction or to improve the hydrophilic property of the polymer, then the further disadvantage arises that the electrostatic repulsion between hydroxyl groups as polar groups and siloxane portions as non-polar groups causes phase separation, not allowing a transparent polymer to be obtained. The present invention seeks to overcome the above problems by providing polymers from which contact lenses may be prepared which are high in oxygen permeability and excellent in mechanical properties such as impact strength. The present invention provides a polymer comprising units derived from a maleimide derivative represented by the following general formula (I) where R 1 is a hydrogen atom or a methyl group, and R 2 is an alkyl, alkenyl or aryl group, each of which groups is substituted by at least one organosiloxane group or fluorine atom. The invention also provides contact lenses obtained from a plastics material comprising such a polymer. The invention additionally provides a contact lens obtained from a plastics material comprising a polymer, which polymer comprises units derived from a maleimide derivative represented by the formula (I), given and defined above. The invention further provides a copolymer (and a contact lens obtained from a copolymer), which copolymer comprises units derived from (a) a maleimide derivative of the above formula (I)'; and (b) a copolymerizable derivative selected from i) at least one (meth)acrylic acid ester selected from an alkyl(meth)acrylate and a fluoroalkyl(meth)acrylate; or ii) at least one styrene derivative of the formula wherein R 4 , X, Y, A, m, a, b and c are as later defined: or (c) at least one (meth)acrylic acid siloxanylalkyl ester of the structure wherein R 4 , X, Y, A, m, a, b and c are as later defined and R 5 is a hydrogen atom or a methyl group. The maleimide derivative of the present invention is characterized by the existence of an imide group as providing both a polar group and a rigid five-membered ring. Moreover, as a result of the substituent group on the nitrogen atom as later described, the polymer may be very effectively used as a material for contact lenses. In the maleimide derivative of the invention represented by the general formula (I), R 2 is an alkyl, alkenyl, or aryl, group substituted by an organosiloxane group and/or a fluorine atom. The alkyl or alkenyl group may be either a straight chain or branched chain group, and is preferably an alkyl or alkenyl group with 2 to 30 carbon atoms selected, for example, from an ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, t-butyl group, n-pentyl group, neopentyl group, n-octyl group, n-decyl group, n-dodecyl group, n-tetradecyl group, cyclohexyl group, hydroxyethyl group, hydroxybutyl group, ethoxyethyl group, butoxyethyl group, allyl group and an acetoxyethyl group. The aryl group is preferably an aryl group with 6 to 20 carbon atoms selected, for example, from a phenyl group, 4-hydroxyphenyl group, 4-carboxyphenyl group, 2-methoxyphenyl group, 4-methoxyphenyl group, 2-methylphenyl group, 4-methylphenyl group and a naphthyl group. Above all, if R 2 is an aryl group, a polymer high in both refractive index and glass transition temperature can be obtained, and if R 2 is a long-chain alkyl group with 10 or more carbon atoms, a polymer low in glass transition temperature and high in oxygen permeability can be obtained. Furthermore, R 2 contains, as a substituent, at least one organosiloxane group or fluorine atom, which substituent may depend from the alkyl or alkenyl, moiety or aryl moiety itself or, when another substituent is present thereon, from that other substituent. If the group R 2 is at least partially substituted by a fluorine atom, stain resistance can be achieved, and if substituted by organosiloxane, high oxygen permeability can be achieved. When a group R 2 contains an organosiloxane substituent, R 2 may have the formula: wherein: (1) B is a direct bond, a phenyl group or a phenyl group substituted by an organosiloxane group and/or a fluorine atom; (2) R 3 is a direct bond, an ester linkage or an amide linkage; (3) R 4 is a C 1-5 alkyl group; (4) X, Y and A are each, independently of one another, a C 1-5 alkyl group, a phenyl group or a fluoroalkyl group; (5) m is from 0 to 200 inclusive, and (6) a, b and c are each independently of one another from 0 to 2 inclusive. When a group R 2 contains a fluorine atom as substituent, R 2 may have the formula: wherein X 1 , X 2 , X 3 , X 4 and X 5 are each, independently of one another, a hydrogen atom, a fluorine atom or a fluoroalkyl group. Groups substituted by a fluorine atom and/or organosiloxane include, for example, -CH 2 (CF 2 ) 2 H, -CH 2 CF 2 CF 3 , -CH 2 (CF 2 ) 4 H, -CH 2 (CF 2 ) 3 CF 3 , -CH 2 CF 3 , -CH(CF 3 ) 2 . and Examples of the maleimide derivative represented by the general formula (I) are given below: The contact lenses of the present invention are made of a polymer comprising a maleimide derivative represented by the general formula (I) as a polymer component. When the maleimide derivative is copolymerized, either a polar monomer or a non-polar monomer can be used as the comonomer, for obtaining a transparent polymer. For example, monomers known for use in preparing conventional contact lens materials can be used without any special limitation. The non-polar monomer can be selected, for example, from alkyl (meth)acrylates (i.e. alkyl acrylates or methacrylates) such as methyl (meth)acrylate, ethyl (meth)acrylate and butyl (meth)acrylate, halogenated alkyl (meth)acrylates such as trifluoroethyl (meth)acrylate and tetrafluoroethyl (meth)acrylate, cycloalkyl (meth)-acrylates such as cyclohexyl (meth)acrylate and aromatic vinyl monomers such as vinylbenzene, vinylnaphthalene and vinylethylbenzene. The polar monomer can be selected, for example, from hydroxyalkyl (meth)acrylates such as hydroxyethyl (meth)acrylate and hydroxybutyl (meth)acrylate, (meth)acrylic acid and heterocyclic vinyl monomers such as vinyl carbazole and N-vinylpyrrolidone. The amount of the maleimide derivative contained in the polymer is not especially limited but is preferably at least 5 wt%, and can also be 100 wt%. If the content is less than 5 wt%, the excellent balance between oxygen permeability and mechanical properties tends to be lost. Particularly preferred copolymers consist essentially of units derived from about 5 to 95 parts inclusive by weight of total monomer content of at least one maleimide derivative of the above formula (I), and about 95 to 5 parts inclusive by weight of the total monomer content of: i) at least one (meth)acrylic acid ester selected from an alkyl(meth)acrylate and a fluoroalkyl(meth)acrylate; or ii) at least one styrene derivative of the formula wherein R 4 , X, Y, A, m, a, b and c are as defined above. Another preferred copolymer consisting essentially of units derived from: (a) at least one maleimide derivative of the above formula (I); and (b) at least one (meth)acrylic acid siloxanylalkyl ester of the structure wherein R 4 , X, Y, A, m, a, b and c are as defined above and R 5 is a hydrogen atom or a methyl group. The contact lenses of the present invention can be prepared according to any of the following methods. In one method, a maleimide monomer and, as required, another comonomer are copolymerized and the polymer is machined to form lenses. In another method, a maleimide monomer and a monomer with a functional group capable of being modified later are copolymerized, and the polymer is formed into lenses which can be subsequently modified by a polymer reaction. For soft lenses, mold polymerization or spin cast polymerization, for example, can also be used. In a material for a contact lens of the present invention, it is also preferable to include an ultraviolet radiation absorbent or pigment or a coloring agent for protecting the eyes from harmful ultraviolet rays or to improve handling convenience. The present invention enables the provision of contact lenses high in oxygen permeability and good in mechanical properties. Embodiments of the invention will now be described with reference to the following Examples and comparative Example. Example 1 Maleic anhydride and tris(trimethylsiloxy)propylamine were caused to react at a molar ratio of 1 : 1, to obtain maleinamic acid. This was heated in the presence of acetic anhydride and sodium acetate, to obtain N-3-tris(trimethylsiloxy)silylpropylmaleimide. Fifty parts by weight of the N-3-tris (trimethylsiloxy) silylpropylmaleimide, 100 parts by weight of 2-hydroxyethyl methacrylate and 0.015 part by weight of ethylene glycol dimethacrylate as a cross-linkable monomer were mixed, and 0.0075 part by weight of azobisisobutyronitrile and 0.0075 part by weight of azobiscyclohexane carbonitrile as polymerization initiators were added. The mixture was placed in a test tube of 18 mm in diameter and 180 mm in height. The monomer mixture was degassed in an argon atmosphere, sealed, polymerized at first at 60°C for 22 hours, heated from 60°C to 110°C, taking 24 hours, and held at 110°C for 4 hours, to obtain a polymer. The polymer obtained was homogeneous and transparent, and the Shore D hardness was about 85. From the polymer 0.5 mm thick disc samples were cut out, and the coefficient of oxygen permeability (DX) was measured and found to be about (110 x 10 -11 cc (STP),cm/(cm 2 .sec. mmHg)) 8.25 x10 -16 m 3 (STP)m/s.m 2 .Pa, to show that the polymer has good oxygen permeability. Comparative Example 1 A polymer was obtained as in Example 1, except that methacryloxypropyl tris(trimethylsiJ.oxy)silane was used instead of N-3-tris (trimethylsiloxy) silylpropylmaleimide. It was white and opaque. As can be seen from the above results, these embodiments of the present invention provide contact lenses high in oxygen permeability and good in mechanical properties.

Claims: A polymer comprising units derived from a maleimide derivative of the formula (I) wherein R 1 is a hydrogen atom or a methyl group and R 2 is an alkyl, alkenyl or aryl group, which alkyl, alkenyl or aryl group is substituted by an organosiloxane group and/or a fluorine atom. A polymer according to claim 1, wherein R 2 has the formula: wherein: (1) B is a direct bond, a phenyl group or a phenyl group substituted by an organosiloxane group and/or a fluorine atom; (2) R 3 is a direct bond, an ester linkage or an amide linkage; (3) R 4 is a C 1-5 alkyl group; (4) X, Y and A are each, independently of one another, a C 1-5 alkyl group, a phenyl group or a fluoroalkyl group; (5) m is from 0 to 200 inclusive; and (6) a, b and c are each independently of one another from 0 to 2 inclusive. A polymer according to claim 1, wherein R 2 has the formula: wherein X 1 , X 2 , X 3 , X 4 and X 5 are each, independently of one another, a hydrogen atom, a fluorine atom or a fluoralkyl group. A copolymer consisting essentially of units derived from: (a) a maleimide derivative of the formula (I), where R 1 is a hydrogen atom or a methyl group, and R2 is an alkyl, alkenyl or aryl group, which alkyl, alkenyl or aryl group is substituted by an organosiloxane group 'and/or a fluorine atom; and (b) at least one (meth)acrylic acid ester selected from an alkyl(meth)acrylate and a fluoroalkyl(meth)acrylate. A copolymer according to claim 4 , comprising about 95 to 5 parts by weight of the total monomer content of component (a) and from 5 to 95 parts by weight of the total monomer content of component (b). A copolymer consisting essentially of units derived from: (a) a maleimide derivative of the formula (I), defined in claim 1; and (b) at least one styrene derivative of the formula wherein R 4 , X, Y, A, m, a, b and c are as defined in claim 2. A copolymer according to claim 6, comprising about 95 to 5 parts by weight of the total monomer content of component (a) and from 5 to 95 parts by weight of the total monomer content of component (b). A copolymer consisting essentially of units derived from the following comonomers: (a) at least one maleimide derivative of the formula (I), defined in claim 1; and (b) at least one (meth)acrylic acid siloxanylalkyl ester of the structure wherein R 4 , X, Y, A, m, a, b and c are as defined in claim 2 and R 5 is a hydrogen atom or a methyl group. A copolymer according to claim 8, comprising about 95 to 5 parts by weight of the total monomer content of component (a) and from 5 to 95 parts by weight of the total monomer content of component (b). A contact lens comprising a polymer according to any preceding claim. Use, as a contact lens, of a plastics material comprising a polymer, which polymer comprises a maleimide derivative of the formula (I), wherein R 1 is a hydrogen atom or a methyl group and R 2 is an alkyl, alkenyl or aryl group, which alkyl, alkenyl or aryl group is substituted by an organosiloxane group and/or a fluorine atom.

Inventors: KAWANO TEIJI, YOKOTA MITSURU, KAWANO, TEIJI, YOKOTA, MITSURU
Applicants: TORAY INDUSTRIES, TORAY INDUSTRIES, INC.
Application year: 1993
Main classification: G02B1
IPC codes: G02B1, C08F22, C08F230, C08F222, C08F246, G02C7