DE2262866A1 - A POLYMER SUITABLE AS A CONTACT LENS MATERIAL AND A PROCESS FOR ITS MANUFACTURING - Google Patents

Description

Suitable polymer and method as contact lens material for its manufacture

The invention relates to a polymer suitable as a contact lens material with moderately crosslinked! Contains% pendant Carbdxy substituent groups, calculated as the free carboxyl groups, wherein the substituents are carboxyl groups, Carbonsäurealky may be estergruppen lower .Alkyle, carboxylic anhydride groups or combinations of these groups, and a method for producing this - carbon-carbon backbone which comprises at least 10 wt.! Polymers.

It is known that contact lenses are made of hard materials such as glass and transparent plastics, in particular hard aoryl polymers and the like. Solo lenses are useful, but have serious disadvantages. Although plastic lenses Safer to use and handle than glass lenses, they have limited application as they are too useful for the wearer are hard and uncomfortable. About the disadvantages of the hard polyacrylate lenses To eliminate, lenses made of hydrophilic polyacrylates, so-called hydrogel polyacrylates, have been developed. Even though

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the contact lenses made from the hydrogel polymers in are in fact soft and are proportionate to the human eye with adapt to little inconveniences «they also have serious disadvantages:

1. the hydrogel polymer becomes enriched with harmful substances;

2. the hydrogel product promotes the growth of pathological microorganisms; and

3. The hydrogel lenses require because of their low strength and its high water content a special, cumbersome one Handling.

There is therefore a need for a material that is capable of being made substantially more anhydrous but more pliable Contact lenses are suitable that are comfortable for the wearer, firm, comfortable and safe to use. Purpose of the invention is to such a contact lens material and a Specify the process for its manufacture.

According to the invention, this object is achieved with a polymer of the type mentioned at the outset in that such a proportion of the pendant carboxy substituents is present as carboxylic acid ester groups of an alcohol with 1-15 carbon atoms in the molecule that the glass transition temperature is below 20 ^° C,

Furthermore, this object is achieved according to the invention by that the polymer undergoes one or more chemical conversion reactions is subjected, namely

a) a direct esterification of the pendant carboxyl and carboxylic acid anhydride groups;

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b) an indirect esterification of the attached carboxyI- and carboxylic anhydride groups; and or

o) a transesterification of the alkyl carboxylate groups lower Alkyls.

The invention enables the glass transition temperature to be lowered (Softening) hard, moderately cross-linked polymers with a carbon-carbon structure. If these polymers are at least 10 wt% carboxy substituent groups calculated as contain free carboxyl groups -COOH, they can be effective be softened by a treatment in which the pendant groups are directly or indirectly softened by one or more chemical conversion reactions with an appropriate alcohol be esterified and / or transesterified. Such substituent groups are carboxyl groups, carboxylic acid alkyl ester groups lower alkyl and carboxylic acid anhydride groups. The polymer may contain one or more kinds of these substituents.

"A hard polymer is understood here as one whose glass transition temperature is so high that objects, for example contact lenses, can be manufactured from it with the aid of customary processing methods. In general, the glass transition temperature of such polymers is above 50 ^° C.

The measurement of the glass transition temperature of plastics is known. A description can be found, for example, in the

Book "Introduction to Polymeric Visco-elasticity" by

J.J. Aklonis, W.J. MacKnight and M. Shen, John Wiley, New York,

A moderately crosslinked polymer is understood here to mean a polymer with an essentially linear structure in which the Only one of the precursor mixes used for production

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Amount of crosslinking agent contains that a moderate three-dimensional crosslinking of the polymer occurs, i.e. a polymerization mixture, which contains 0.1 to 10 moles of crosslinking agent per 100 moles of monomer and crosslinking agent.

Polymers with a carbon-carbon structure are known (see "Organic Chemistry of Synthetic High Polymers", RW Lenz, Intersoience Publishers, New York 1967). These monomers are made by polymerizing monoolefinic monomers and monomer mixtures. When the crosslinking agent is not included in the monomer, long linear chains of carbon atoms are generated. When the olefin functional group contains substituent groups such as a carboxyl group as in acrylic acid, the linear chains of carbon atoms contain pendant carboxyl groups; hence the name polymer with a carbon-carbon backbone. For the present purpose, the polymer with a carbon-carbon backbone must contain sufficient carboxy substituent groups to enable the desired chemical and physical modification. In general, at least 10% by weight , preferably at least 20% by weight, of the polymer should be carboxy substituents. Although the hard polymer precursors used here are essentially insoluble in suitable esterifying agents such as alcohols, alcohol mixtures and the like, it has surprisingly been found that the esterifying agent penetrates the solid, moderately crosslinked polymer easily and relatively quickly, so that useful reaction times are possible within acceptable reaction times chemical conversions can be achieved.

In the present process, a part of the hard polymer, For example, a lens made from a polymer blank, immersed in a liquid medium and esterified and / or transesterified or indirectly esterified. Apart from the proportionate

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longer reaction times and the solid reactant, the usual conditions are to be used and satisfactory.

The esterification is through direct reaction of the attached Carboxyl groups of the polymer with an alcohol:

0 0

1. -C-OH + ROH ^ -COR + Η _£ 0

or by indirect esterification of the pendant carboxyl groups carried out by an acid halide according to the following equations:

0 0

dd M

2. -C-OH + PC1 _K £ ■ -C-Cl + POCl, + HCl

5 y?

-C-Cl + ROH> ~ C ~ O-R + HCl

The transesterification is an alcohol exchange reaction that takes place as follows can be represented:

0
dd

-CO-CH ₀ CH (GH,) ₀ + CH ^ OH

The products, lenses, etc. obtained are generally flexible and physiologically compatible), for example Contact lenses made by the method of the invention

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treated with little or no eye discomfort for most wearers. The new polymers obtained by the process according to the invention are essentially hydrophobic (they absorb less than 1 wt .- ^ water at room temperature) and have glass transition temperatures of below 20 ° C, often below 0 ⁰ C. Due to the low water absorption of the new polymer products according to the In the invention, those in known products, in particular lenses made from hydrogel polymers, are avoided.

In a preferred embodiment of the invention, a hard polymer is produced by polymerizing a mixture of acrylic acid, 2-methoxyethyl methacrylate and 1,4-butanediol dimethacrylate. Expediently, 49.5 mol of acrylic acid, 49.5 mol of 2-methoxyethyl methacrylate and 1 mol of 1,4-butanediol ester are contained in every 100 mol of the mixture. The polymerization is carried out by means of a broadband ultraviolet radiation, and by the addition of about 0.1 - promoted (based on the mixture)% benzoin as photoinitiator.. For the polymerization, the mixture is poured into a flat vessel, the inner surfaces of which have preferably been pretreated in the usual way for easy removal of the acrylic polymer. The vessel is filled with the polymerization mixture to a height of about 6 mm. At room temperature and under ultraviolet radiation to catalyze the polymerization, the reaction is complete after about 12 hours. The product is a clear, non-pliable polymer with a vinyl backbone that contains pendant carboxyl and 2-methoxyethyl groups. This polymer has a glass transition temperature of about 100 C.

In the next stage of the process, the hard polymer becomes one Lens blank (button) cut. The blank is made taking into account the in the subsequent esterification treatment

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Dimensional change occurring (preliminary tests showed an increase in volume of about $ 5) formed into a lens. Here become the well-known and customary ones for machining, grinding and polishing of the contact lens precursor Methods used to manufacture plastic lenses (see "Contact Lens Practice," Robert Mandell, C. Thomas; Springfield, Illinois 1965). The product obtained is a hard one Lens, a precursor lens suitable for conversion into a new and useful lens by the method of the invention is.

Next, the precursor lens is immersed in a concentrated solution of phosphorus pentachloride in carbon disulfide (carbon disulfide) immersed and the solution kept boiling on the reflux condenser for 20 hours. Through this treatment will be the pendent carboxyl groups of the hard polymer are converted into acid chloride groups (-C0C1). After that, the acid chloride groups converted to ester groups by taking the precursor lens out of the carbon disulfide solution and is immersed in n-butyl alcohol, which until the esterification is complete, i.e. about 20 hours, is kept at the reflux condenser at boiling temperature. The esterified polymer obtained Lens, is then washed with water and dried, for example in a vacuum dryer at 60 ° C. The dried one Lens is soft, clear and ready to use after autoclave sterilization.

In an alternative embodiment of the invention, the glass transition temperature of the precursor hard lens is determined by a direct esterification process decreased. In this procedure, the lens is immersed in a suitable acidic alcohol, e.g. n-butanol, "immersed under reflux for about 10 hours is kept at boiling temperature, a period of time that is

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is sufficient to esterify essentially all of the free carboxyl groups present. About 1 wt -.% (Based on the alcohol) 85 # sulfuric acid, a sufficient amount of acid.

The treated lens is then removed from the n-butanol. It is washed to remove adhering acid and alcohol and dried at 60 ° in a vacuum dryer. The lens obtained has a satisfactory glass transition temperature and is ready to use.

The direct esterification treatment of the prepolymer appears primarily to be the esterification of pendant carboxyl groups to pass. It should be noted, however, that other reactions, such as transesterifications and etherifications, are also to a certain extent as well as reactions between pendant carboxyl and pendant 2-methoxyethyl groups (internal transesterification) can take place.

Pendant carboxyl groups and lower alkyl carboxylic acid alkyl ester groups give a polymer having a carbon-carbon backbone Hardness and at the same time form the functional places where the method of the invention for degradation the glass transition temperature of the treated polymer attacks. The desirable relative amount of pendant groups imparting this hardness depends on the number and type of pendant Carboxylic acid alkyl ester groups of higher alkyls contained in the polymer. In general, the acidic production Polymerisatiotlsmisohung used of the hard polymer contain at least about 20 mole # of a carboxyolefin monomer. These hard, moderately cross-linked polymers with a carbon-carbon backbone and their manufacture are known, and the products and their manufacture themselves are within the scope of this Invention not claimed as new. As stated above, the determination of the glass transition temperature is also a well-

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known measure, accordingly, the use of hard, moderate crosslinked polymers with carbon-carbon backbone, which have at least 10 wt .- ^ carboxy substituent groups, calculated as free carboxyl groups included in the invention as well included such as the use of similar hard polymers that have a smaller number (up to $ 20) of carbon atoms in the The basic structure is replaced by oxygen, nitrogen, silicon and sulfur, preferably oxygen and nitrogen.

Preferably the hard polymer precursor is an acrylic polymer.

An acrylic polymer as used for the purposes of the present invention is understood to mean a polymer which by the usual polymerization of an acid of the aerylic acid type (an acid with an olefinic double bond), an acrylic acid ester, an acrylic anhydride or a mixture of two or more of these monomers. Accordingly included the polymers used for the purposes of the present invention pendent carboxyl groups, pendent carboxylic acid ester groups, pendant carboxylic anhydride groups or mixtures of two or more types of these groups.

Acids with olefinic double bonds, which are preferred as monomers for the preparation of the hard polymer for purposes of the invention, have the general formula (C = C) (COOH) _n (R) ₂ , wherein η 1 or 2 and R is hydrogen or a When η is 2, the carboxyl groups with the same carbon atom or ^ can be linked to different carbon atoms of the carbon-carbon double bond, and when η is greater than 1, the R groups can be the same or to be different. When the olefinic acid is a monobasic acid, the preferred monomers have the formula:

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R ¹ R ² C = CR ⁵ COOH,

IP

where R and R are alkyl groups of less than 6 carbon atoms or hydrogen and Br is hydrogen or methyl

1 2
is. Preferably R and R are the same or different and either hydrogen, methyl or ethyl. The corresponding carboxylic acid anhydrides can also be used.

Representative olefinic acids for making more satisfactory hard acrylic polymers include acrylic acid, methacrylic acid, butene-1-acid, isopentene-2-acid, 2,> - dimethylbutene-2-acid, Methylpentene-2-acid, tiglinic acid, angelicic acid, senecic acid, Maleic acid, itaconic acid and like olefinic acids.

Acrylic ester type monomers, i.e., esters of the foregoing Olefic acids are generally in admixture with an olefinic acid component useful for making a suitable hard polymer. Satisfactory hard polymers are also produced obtained when the monomer acrylic component wholly or mainly a methyl acrylate, an ethyl acrylate or is a mixture of the two esters. Preferred monomer components acrylic acid ester type have the shape

R ¹ R ² C = CR ^ COOZ, 12 "5

wherein the groups R, R and R ^ are the same as above and wherein Z is an alkyl group having 1 to about 11 carbon atoms, a hydroxyalkyl group having 2 to about 11 carbon atoms, or an alkoxyalkyl group having 3 to about 11 carbon atoms,

Representative acrylic ester monomers for running the Invention include methyl, ethyl, n-propyl, i-propyl as well Butyl acrylates and methacrylates, 2-hydroxyethyl acrylate and methacrylates, 2-hydroxypropyl acrylates and methacrylates as well as especially the alkoxyalkyl acrylates and methacrylates

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where Z has the formulas: -CH ₂ CH ₂ OY, -CH ₂ CH (OY) CH _{1, -CH (CH 3} ) CH ₂ OY or -CH ₂ CH ₂ CH ₂ CH ₂ OY, where Y is an alkyl group with 1 to T, in particular 1 to 3, carbon atoms.

The dimensional stability and hardness requirements of the polymer precursor used for purposes of the present invention are best met by specifying the relative proportions and types of reactants used in the polymerization mixture. The relationships between dimensional stability and the amount of the grinding agent have already been discussed above. With regard to the other participants Reaktionstejl ·, of the acrylic monomers, the composition of the mixture can vary within wide limits, provided that at least 10 wt -% consists of the mixture of Carboxylgruppensubstituenten or their equivalents (ie Carbonsäurealkylester- and / or Olefinsäureanhydridgruppen)..

Preferably, the hard precursor polymer is made from a mixture of acid and ester monomers, with the acrylic polymer contains the following components, based on 100 mol of the polymerization mixture:

1. Acrylic acid type acid in an amount of 20 to 90, preferably 50 to 75 moles;

2. An acrylate type ester in an amount of 10 to 75, preferably from 25 to 50 moles; and

3. a divinyl type crosslinking agent in an amount of 0.1 to 10, preferably 1 to 5 moles.

When the acid component of the hard polymer is acrylic acid, methacrylic acid or a mixture of these acids and the ester component is an alkoxyalkyl acrylate or methacrylate, ₍

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the process of the present invention, contact lenses of superior quality.

The polymerization mixture must contain a certain amount of crosslinking agent included, otherwise the polymer precursor and the treated Polymer do not have satisfactory dimensional stability. On the other hand, if the mixture contains too much crosslinking agent contains, the polymer obtained can not naoh the process of the invention can be converted into a flexible and physiologically compatible product. For every 100 moles of the polymerizable Components of the polymerization mixture is at least 0.1 mol a divinyl type crosslinking agent is required. As a rule, a satisfactory hard polymer precursor is obtained, when the relative amount of the crosslinking agent is 0.1 to 10, is preferably 1 to 3 moles per 100 moles of the mixture.

Divinyl type organic crosslinking agents known for olefin polymerization are also brewable for the process of the invention. The general formula of the particularly suitable crosslinking agents is (H ₂ C-CH) ₂ Q, where Q can be oxygen or a divalent organic radical of carbon and hydrogen or carbon, hydrogen and oxygen. In general, satisfactory crosslinking agents have a molecular weight on the order of 70 to 400.

Representative crosslinking agents for the practice of the present invention include compounds of the following Klassent

1. Divinyl esters of organic dicarboxylic acids such as oxalic acid, Terephthalic acid, hexahydroterephthalic acid, malonic acid, Succinic and similar acids;

2. ethers of the divinyl type such as divinyl ether, dibutenyl (-5) ether, . Dipentenyl {-4) ethers and similar ethers;

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- ι? - ■

3 »Diviny! Hydrocarbons (alpha-omega-diolefin hydrocarbons) such as divinylbenzene, divinyltoluene, 1,4-pentadiene, i, 5-hexadiene and similar hydrocarbons, the two Vinyl-j i.e. "(CHp = CH) groups;

4. Aliphatic ^ diol (glycol) esters of acids of the acrylic acid type as indicated above, for example esters with the formula CH ₂ = CHgCOO (CH ₂ CH ₂ O) _n CH ₂ CH ₂ OOCCh = CH ₂ , where η a number from 0 to 3 "inclusive is 1,4-cyclohexanediol diacrylate and dimethacrylate and the corresponding esters of 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, ethylene glycol and similar esters of carboxylic acids of the acrylic acid type. Crosslinking agents of the acrylic acid and methacrylic acid glycol ester type are preferred.

Representative polymerization conditions include:

1. The use of a suitable catalyst (an organic or inorganic peroxide, ultraviolet light, X-rays, electron bombardment or the like) j

2. The application of heat and sufficient pressure to keep the Keep reactants in a liquid state;

3. Its sufficient response time to ensure a complete polymerization of the mixture. One for purposes The preferred method of the present invention is to carry out the polymerization at ambient temperature below exposure to ultraviolet light.

The choice of those useful for purposes of the present invention Alcohols depends on whether the treatment is an esterification or a transesterification. For the esterification of carboxylic acid groups Ethanol is already advantageous for lowering the glass transition temperature. Preferably the one for a direct

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Esterification used alcohol at least 3 carbon atoms contained in the molecule. In cases "where the desired softening effect is brought about by a transesterification" higher alcohols are used as exchange alcohols, which generally have at least 2 more carbon atoms in the molecule than that contain substituted alcohols. A satisfactory alcohol therefore generally contains from 1 to 15 carbon atoms Molecule and shows useful penetration into the interior of the hard polymer described above. Preferably the Number of carbon atoms in the molecule of alcohols be less than 12. The alcohol can be monohydric or dihydric or a monohydric methoxy, ethoxy or propoxy alcohol be. A single alcohol or a mixture of alcohols can be used for the esterification or transesterification.

Particularly satisfactory results are obtained when the treated hard polymer, i.e. the final product, is less than 75 mol # alkoxyalkyl and hydroxyalkyl! Ester groups. The relative proportion of the hydroxyalkyl and alkoxyalkyl ester groups of the treated polymer should be in the range of 10 to 75, preferably from 25 to 50 mole # of the total amount of pendant ester groups.

Those used for the esterification or transesterification treatment Alcohols can contain primary, secondary or tertiary hydroxyl groups. Apparently, best results will appear in general obtained when using monohydric primary alcohols having 1 to about 7, preferably 3 to 7 carbon atoms in the molecule.

A preferred class of alcohols for purposes of the invention is represented by the formula ZOH, where Z can be:

1. A hydrocarbon radical having 1 to 11 carbon atoms; or

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2. A radical of the formula -CH ₂ GH ₂ OY, -

-CH ₂ CH ₂ CH ₂ OY, -CH (CH ₃ ) CH ₂ OY, -CH ₂ CH ₂ CH ₂ CH ₂ OY, or the like, wherein. Y is an alkyl group having 1 to about 7, preferably 1 to 5 carbon atoms. The aforementioned hydrocarbon radicals must be free of double and triple bonds between carbon atoms, that is, they must not be unsaturated hydrocarbon radicals. Suitable hydrocarbon radicals are alkyl, cycloalkyl, aralkyl, alkylcyoloalkyl or cyoloalkylalkyl groups, and the alfcyl moieties can be straight-chain or branched. Preferably the hydrocarbon radical is an alkyl group.

Representative alcohols (for esterification or transesterification) include methanol, ethanol, n-propanol, i-propanol, n-butanol, s-butanol, t-butanol, pentanol-2, n-pentanol, n-hexanol, Heptanol-2, octanol, nonanol, decanol and similar alkenols, especially alkenols with fewer than 8 carbon atoms in the Molecule, also cyclohexanol, benzyl alcohol, hexahydrobenzyl alcohol, 1,4-cyclohexanediol, cyclopentanone 2-methylcyolopentanoi and similar acyclic alcohols, 2-methoxyethanol, 2-methoxypropanol-1, 2-ethoxyethanol, 2- {n-propoxy) A "ethanol, 3- (n-propoxy) -n-propanol, 5-methoxy-n-butanol, 4- (n-propoxy) -n-butanol, 4-ethoxy-n-butanol and similar alkoxyalkanols, glycol, 1,4-butanediol, 1, J5-propanediol, 1,2-dihydroxybutane, 1,3-dihydroxybutane and like dihydric alcohols. Preferred alcoholic esterifying agents are n-propanol and n-butanol.

The esterification and / or transesterification reactions by which the hard precursor polymer is upgraded are carried out in one of the common ones Esterification or transesterification of a representative carboxylic acid, e.g. propionic acid, analogously in a known one homogeneous reaction system carried out, however, the reaction time can be longer by 10 to 500 #.

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The direct esterification by treatment with an esterifying agent can be carried out over a wide range of temperatures. Satisfactory results are obtained in a temperature range of about 10 to 200 ⁰ C. Since the esterifying agent must be in the liquid state, a pressure sufficient to maintain the liquid state is necessary when working in the upper range of the specified temperature range.

In general, what is required for a satisfactory conversion of the hard polymers, the temperature used, the alcohol used for esterification and the time required Presence or absence of an esterification catalyst in the mixture. Usually the time required is between 1 and 100 hours, with shorter times being assigned to higher temperatures in the specified range.

The esterification takes place in the absence of a catalyst under the known thermal conditions for an esterification, for example at a temperature of approximately above 10 ^° C. and approximately below 200 ^° C. An esterification catalyst is preferably used which is soluble in the alcohol provided as the esterifying agent. In general, esterification catalysts whose usefulness is known for the catalysis of alkanol-carbonic acid esterification reactions can also be used for the proposed process. Concentrated sulfuric acid is a preferred catalyst because of its general solubility in the esterifying agents contemplated herein and because of its relatively easy removability from the treated polymer. When sulfuric acid is used to catalyze the desired conversion, a satisfactory reaction time is between 4 and 20 hours.

The amount of the esterifying agent and the catalyst can be in

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wide limits fluctuate, in general one should be so large Amount of alcoholic esterifying agent to be used, that the hard precursor polymer can be completely submerged therein. According to the usual esterification practice. the effective amount of the esterification catalyst is 0.2 to 5 wt .- ^, based on the weight of the alcoholic esterification agent.

As has been found, pendant carboxyl groups can be identified by known Acid halide-yielding reactions in acid halide groups be transferred. Since the hard precursor polymer in the liquid reactant (i.e. the halogenating agent, if this is itself a liquid, or a solution of the same is insoluble in an inert solvent) are the Response times a little longer than with conventional conversions.

The time required also depends on the thickness of the object, such as a lens, and the temperature used. In general, suitable reaction times are between about 1/2 hour and 100 hours, usually between 5 and 25 hours. The inert solvents conventionally used in acid chloride reactions, such as carbon disulfide (carbon disulfide), carbon tetrachloride (carbon tetrachloride), alkyl ethers, hydrocarbon mixtures and the like, are just as suitable for the present purpose as the temperatures normally used in converting a carboxyl group into an acid halide group . These depend on the respective reagent, the solvent and the pressure and are usually in the range between 10 and 200 ^° C.

A large number of inorganic acid chloride-forming reagents including phosphorus penta chloride, phosphorus trichloride, phosphorus oxychloride, Thionyl chloride, sulfuryl chloride and similar reagents

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zlen are useful for the present purpose. The corresponding Bromine compounds are also useful reagents, however naturally more expensive and therefore less useful. Phosphorus pentachloride and theonyl chloride are preferred in the present invention.

The esterification of a hard polymer having pendant acid halide is carried out by the polymer immersed in a suitable alcohol, and is held therein to a temperature in a range voh'eiwa IÖ to 200 ⁰ C at a pressure sufficient to increase the alcohol in a liquid state and for such a long period of time that an essentially complete (> 95 # lge) conversion of the acid halide groups (-COC $ to ester groups (-COOR) takes place. Depending on the temperature, a satisfactory reaction time is between 1/2 hour and 100 hours.

When the esterification is over, the esterified polymer is taken out of the agent from the hydrohalic acid formed washed free, freed from the absorbed or trapped alcohol by washing with water and dried. Upon transesterification by the present process, pendant carboxylic acid alkyl ester groups become lower alkyls (usually methyl or ethyl) by an acid-catalyzed exchange reaction in alkyl ester group η suitable higher Converted to alkyls. A low-boiling alcohol is displaced from the ester group by a higher-boiling alcohol, and the reaction continues until it is completely displaced when the low-boiling alcohol is separated off by distillation will. The hard lens is immersed in the higher alcohol, which contains a mineral acid catalyst, and on the reflux condenser is kept simmering. The conversion is complete when little or no low-boiling alcohol remains from the reaction

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medium distilled off. To achieve a satisfactory Lowering the glass transition temperature of the hard polymer the higher boiling alcohol should generally have 2 to 9 carbon atoms contain more in the molecule than the lower boiling alcohol. As in the case of a direct esterification, it is useful to to use a strong mineral acid such as sulfuric acid in the same proportion as there. That way will a hard polymer that has pendant carboxyl groups (-COOH) and pendant carboxylic acid alkyl ester groups (-COOR) of lower alkyls contains, through a combination of a direct esterification and a transesterification into a product with reduced and satisfactory Glass transition temperature converted.

The following examples illustrate the invention. In any case, the polymerization mixture was maintained at a temperature of about 25 ⁰ C. The reaction would be catalyzed by irradiating the mixture with broadband ultraviolet light until the reaction was essentially complete, which was about 4 to 12 hours. About 0.1 wt% benzoin was added to the reaction mixture to improve the effectiveness of the catalyst. As a crosslinking agent, 1,4-butanediol dimethacrylate was used, which was added to the polymerization mixture in the ratio of 1 mol to 99 mol of the acrylic type monomer (s). The resulting acrylic prepolymer was generally a hard and inflexible solid.

With the help of common lens manufacturing methods, the Part of the product of each example cut out a blank and formed a lens from this. The lens was then immersed in a suitable alcohol according to the table below immersed, which contained 0.5 g of sulfuric acid for every 100 g. The acidified alcohol and the lentil were then used for one also in the table to the time span in the

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Temperature listed in the table. In Examples 1 to 8 acrylic acid (AA) or acrylic acid and 2-methoxyethyl methaorylate (MEMA) were used. After removal of the treated lens from the alcohol, it was recently was dried in a drier at 60 ⁰ C. The following results were obtained.

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co OO N> 00

O CO

example
No. Acrylate
Components Relative amount
Mole alcohol Esterification conditions
Temp. ⁰ C time, hrs. 6th Remarks I.
\ ^ 6th I. 1. AA
MEMA 1.0
0.0 n-propanol '90 β Soft lens,
satisfactory 2. AA
MEMA OO
to to
ro-3
UlUl n-propanol 90 β Soft lens,
Well AA
MEMA OO
to to
UiUi
OO n-propanol 90 4th Soft lens,
very good 4th AA
MEMA 0.25
0.75 n-propanol 90 4th Soft lens,
satisfactory 5. AA ■
MEMA 1.0
0.0 Methoxyethanol 125 • 4 Soft lens,
satisfactory 6th AA
MEMA 0.75
0.25 Methoxyethanol 125 4th Soft lens,
Well 7 · AA
MEMA 0.50
0.50 , Methoxyethanol 125 Soft lens,
excellent 8th. AA
MEMA 0.25
0.75 Methoxyethanol 125 Soft lens,
satisfactory

ro

Example 9

A mixture of acrylic type monomers has been used of the catalyst system polymerized ultraviolet light benzoin as above. The monomer mixture had the following composition:

Components Haul% n-butyl methaorylate 48 Aoryic anhydride 48 Ethylene glycol dimethacrylate 4th

TOO

The obtained hard acrylic polymer was cut, molded into a contact lens, and polished. The lens was then immersed in isopentanol, which was refluxed at boiling temperature for about 20 hours. Thereafter, the treated lens was taken out of the alcohol, washed with water and dried. The lens obtained was soft (glass transition temperature door below 0 ⁰ C) and clear.

Example 10

The above example was repeated using n-butanol as the esterifying agent. The esterified lens was soft and clear.

Examples 11-17

White aorylate lenses were produced by indirect esterification using the following monomer mixture as the starting material was used;

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component

n-butyl methacrylate 48

Acrylic acid 48

Ethylene glycol dimethacrylate 4

100

The polymerization was carried out as in Example 9. From the The hard acrylic polymer obtained became aerylate lenses as before manufactured. The pendent carboxyl groups of the hard lenses were then made by dipping the hard lenses in an under Refluxing solution of phosphorus pentachloride in carbon disulfide (carbon disulfide) for 20 hours in acid chloride groups converted. The treated lenses were then esterified by immersion in the following alcohols and drying. The following results were obtained:

Example no. Alcohol remarks

Soft, clear, excellent lens

tt η

It It

tt It

dd dd

It tt

1! W.

Examples 18-20

A mixture of the following acrylic monomers and crosslinking agents: Component #

11 n-propanol 12th Isopropanol 13th n-butanol 14th n-pentanol 15th Isopentanol n-hexanol 17th n-octanol

Il It H M. dd dd dd M. dd If tt ' It

2-hydroxyethyl ethacrylate 96

Ethylene glycol dimethacrylate .- 4

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Polymerization was carried out according to the procedure of Example 9, and the reaction products were converted into the described manner hard lenses made. The hard lenses were made using a higher alcohol and an acid catalyst (1 wt .- # sulfuric acid, based on the alcohol) interesterified. The lenses were immersed in the refluxing alcohol, and the following results were obtained:

Example no. Alcohol remarks

18 isopropanol pliable and clear

19 n-butanol "" ⁿ

20 n-pentanol ^w ""

Similar favorable results were also generally obtained with other hard polymers prepared from the above-mentioned monomers and acrylic type monomer mixtures. The resulting hard polymers (lenses) could generally be subjected to one or more of the treatments described above effectively softened and made physiologically compatible.

The above examples show that hard, moderately crosslinked acrylic-type polymers contain pendant carboxyl and / or ester groups contained by an esterification and / or transesterification treatment can be significantly improved with a suitable alcohol.

Except for the contact lenses described in the previous examples Adhesive shells in the form of corneal, half-scleral and scleral lenses of various kinds were also made according to the method of the invention well-known types treated. In each case, the lenses had excellent properties including good flexibility and good physiological tolerance, but a lower water absorption capacity.

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Claims (12)

1. Polymer suitable as a contact lens material with moderately cross-linked carbon-carbon skeleton, which is at least 10 wt .- ^ pendant carboxy substituents, calculated . as free carboxyl groups, where the substituents can be carboxyl groups, carboxylic acid alkyl ester groups of lower alkyls, carboxylic acid anhydride groups or a combination of these groups, characterized in that such a proportion is present as carboxylic acid ester groups of an alcohol with 1-15 carbon atoms in the molecule that the Glass transition temperature of the polymer is below 20 ^° C. 2. Polymer according to claim 1, characterized in that such a proportion of the pendent carboxy substituents is present as carboxylic acid ester groups of an alcohol with 1-15 carbon atoms in the molecule that the glass transition temperature of the polymer is below 0 ^° C. 3. A method for producing a polymer according to claim 1 or 2, characterized in that the polymer is subjected to one or more chemical conversion reactions, namely a) a direct esterification of the attached carboxyl » and carboxylic anhydride groups j b) an indirect esterification of the pendant carboxyl and carboxylic acid anhydride groupsj and / or c) a transesterification of the carboxylic acid alkyl ester groups of lower alkyls. 4. Application of the method according to claim J5 to one of the Polymers made contact lens. 26 466 - 2 - 309828/1034 5. The method NaOH to claim 3, characterized in that? A hard polymer having a glass transition temperature above 50 ⁰ C a the chemical conversion reactions mentioned is subjected to the glass transition temperature to below 20 ⁰ C is lowered. 6. The method according to claim 3, characterized in that the direct esterification mentioned under a) is carried out by reacting the pendent carboxyl or carboxylic acid anhydride groups of the polymer formed into a contact lens with one or more monohydric or dihydric alcohols having fewer than 16 carbon atoms in the molecule by immersing the molded contact lens in the liquid alcohol at a temperature in the range of about 10-200 ⁰ C and a pressure sufficient to maintain the liquid state of the alcohol, the temperature being maintained for a period of 1-100 hours until the lowering of the glass transition temperature is brought about. 7. The method naoh claim 6, characterized in that the esterification is catalyzed by a strong mineral acid. 8. The method naoh Anspruoh 6 or 7, characterized in that the esterification is carried out with a monohydric alcohol with 3-7 carbon atoms la molecule. 9. The method naoh claim 3 » daduroh characterized in that the indirect esterification mentioned under b) of the pendant carboxyl or carboxylic acid anhydride groups of the polymer formed into a contact lens by reaction with an inorganic, carboxylic acid chloride-forming reagent is carried out by the contact lens in the liquid or dissolved 309828/1034 i * 2262886 Reagent is immersed at a temperature in the range of about 10-200 ⁰ C and a pressure which is sufficient to maintain the liquid state of the reagent or the solution, the temperature being maintained for a period of about 2-100 hours until a sufficient chlorination for lowering the glass transition temperature. Carboxyl or carboxylic acid anhydride groups is reached, the contact lens and also from the liquid or gelbsten reagent is removed and the carboxyl groups are formed by immersing the treated contact lens in a liquid alcohol having 1-15 carbon atoms in the molecule, at a temperature in the range of about 10-200 ⁰ C be esterified for a period of 1/2 to 1 hour. 10. A method for improving the flexibility and for reducing the hardness of a contact lens made of a three-dimensionally crosslinked acrylic polymer which contains pendant carboxyl groups, characterized in that the carboxyl groups by immersing the contact lens in a liquid alcohol at a temperature of about 10-200 ⁰ C for esterified over a period of about 1-100 hours. 11. The method according to claim 10, characterized in that the Alcohol contains a sufficient amount of an esterification catalyst. , 12. Flexibility improvement and reduction methods the hardness of a contact lens made from a three-dimensionally crosslinked acrylic polymer that contains pendant carboxyl groups, characterized in that the carboxyl groups are esterified indirectly, ■ by the carboxyl groups first converted into carboxyl chloride groups and then carried out 309828/103 4 Immersing the lens in a liquid alcohol with 1-15 carbon atoms in the molecule at a temperature in the range of about 10-200 ⁰ C for a period of about 1/2 to 100 hours can be implemented. 309828/1 034