DE2262866C2 - Contact lens material and process for its manufacture - Google Patents

Description

It is known to manufacture contact lenses from hard materials such as glass and transparent plastics, in particular from hard acrylic polymers. Such lenses can be used, but they have serious drawbacks. Although plastic lenses safer to use and to handle than glass lenses, they have limited use because they ÜR the carriers are (too hard and uncomfortable. In order to eliminate the disadvantages of the hard polyacrylate L.isen, lenses are made of hydrophilic polyacrylates, called Hydrogel polyacrylates. The contact lenses made from the hydrogel polymers are indeed what and adapt to the human eye with relatively little discomfort, but also have considerable disadvantages:

The hydrogel polymer is enriched with harmful substances.

- The hydrogel product promotes the growth of pathogenic microorganisms.

- Due to their low strength and high water content, the hydrogel linens require special, cumbersome handling. * °

To eliminate these disadvantages, contact lenses made of hydrophilic polymers have therefore already been proposed (US-PS 35 03 942) containing 50 to 90% by weight of hydroxyalkyl acrylate or methacrylate, up to 35% by weight Alkyl acrylic or methacrylate and 1 to 50% by weight of a crosslinking agent. Contact lenses off This material are harder than those made from hydrogel polymers, which is true of their manufacture and processing relieved, but on the other hand also easily leads to discomfort when wearing. They absorb up to 38% Water and therefore tend to swell, which changes the optical properties.

The task was thus to provide a contact hosematerial that would allow the production of substantially anhydrous, pliable lenses that allow them to be worn safely and without discomfort are convenient to use.

According to the invention, this object is achieved by a contact sleeve material according to claim 1. A betrayal for producing the contact lens material is specified in claim 2. Advantageous further training of the Invention are set out in the remaining claims.

The invention enables the glass transition temperature (softening) of hard, moderately crosslinked polymers with a carbon-carbon structure to be lowered. If these polymers are at least 10 wt .-% carboxy Substituent groups, calculated as free carboxyl groups -COOH, can be effectively replaced by a Treatment which can be made in which the pendant groups are replaced by one or more chemical Conversion reactions with a suitable alcohol directly or indirectly esterified and / or transesterified will. Such substituent groups are carboxyl groups, carboxylic acid alkyl ester groups of lower alkyls and Carboxylic anhydride groups. The polymer may contain one or more kinds of these substituents. M)

A hard polymer is understood to mean one whose glass transition temperature is so high that that from Him with Hllie common processing methods objects, z. B. contact lenses can be. In general, the 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 "Introduclion 10 Polymeric Visco-clastlcliy" by J. J. Aklonls, W. J. MacKnlght and es M. Shcn, John Wlley, New York. 1972.

A moderately crosslinked polymer becomes a polymer with a substantially linear structure understood in which the front column erasure used for the production only has such an amount of cross-linking

contains means that a moderate three-dimensional crosslinking of the polymer occurs, d. H. a polyrnerlsailons mix, that for every 100 moles of monomer units 0.1 to 10 moles of a conventional crosslinking agent from Contains divinyl type with a molecular weight of 70 to 400.

Crosslinking agents for practicing the present invention include compounds of the following Classes:

1. Divinyl esters of organic dicarboxylic acids such as oxalic acid, terephthalic acid, hexahydroterephthalic acid, malonic acid, succinic acid and similar acids;
ίο 2nd ethers of the divinyl type such as divinyl ether, dibutenyl (-3) -ether, dlpentenyl (-4) -ether and similar ethers,

3. Divinyl hydrocarbons (alpha-omega-diolefin hydrocarbons) such as divinylbenzene, divinyltoluene. 1,4-pentadiene, 1,5-hexadlene and similar hydrocarbons which _{contain two vinyl, ie (CH 2} = CHj-GrUpPCn;

4. Aliphatic diol (glycol) esters of. Acrylic type acids as mentioned above. for example esters with the formula CH ₂ = CH ₂ COO (CH ₃ CH ₂ O) _n CH ₂ CH ₂ OOCH = CH ₂ , where η is a number from 0 to 3 inclusive: M-Cyclohexandloldiacrylat and -dimethacrylaie and the corresponding esters of 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, ethylene glycol and like esters of acrylic acid type carboxylic acids.

Representative polymerization conditions include:

1. The use of a suitable catalyst (an organic or inorganic ceroxide, ultraviolet Light, x-rays, electron bombardment;

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

3. A sufficient reaction time to ensure complete polymerization of the mixture. One The preferred method for purposes of the present invention is to carry out the polymerization at ambient temperature under the action of ultraviolet light.

The choice of alcohols which can be used for the purposes of the present invention depends on whether the treatment

'.' ■ '■ is an esterification or a transesterification. For the esterification of carboxylic acid groups, etha

: nol advantageous for lowering the glass transition temperature. The one for direct esterification

Claim 1 alcohol used should contain at least 3 carbon atoms in the molecule. In those cases where the desired Erwelchungseffekt is brought about by a transesterification, are called exchange alcohols the higher alcohols used according to claim 1 which have a larger number of carbon atoms in the molecule than the replaced alcohols.

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

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

2. A radical of the formulas -CH ₂ CH ₂ OY, -CH ₂ CH (OY) CII ,, -CH ₁ CH ₂ CH ₂ OY, -CH (CH ₁ ) CH ₂ OY, -CH ₂ CH ₂ CH ₂ CH ₂ OY or the like, where Y is an alkyl group of 1 to about 7, preferably 1 to 3 carbon atoms. The aforementioned hydrocarbon radicals must be free of double and triple bonds between carbon atoms, ie they must not be unsaturated hydrocarbon radicals. Suitable hydrocarbon radicals are alkyl, cycloalkyl, aralkyl, alkylcycloaikyl or cycloalkylalkyl groups, and the alkyl moieties can be straight-chain or branched. Preferably the hydrocarbon radical is an alkyl group.

ig Representative alcohols (for esterification or conversion) include methanol, ethanol, n-propanol.

'* § so i-propanol, n-butanol, s-butanol, t-butanol, pentalnol-2, n-pentanol, n-hexanol, heptanol-2, octane oil, nonanol,

j Decrnol and similar; Alkanols, in particular alkenols with fewer than 8 carbon atoms in the molecule, also

Cyclohexanol, benzyl alcohol, hexahydrobenzyl alcohol, 1,4-cyclohexanedol, cyclopentanone, 2-methylcyclopentanol and similar cyclic alcohols, 2-methox; -äth..nt! l, 2-methoxypropanol-l, 2-ethoxyethanol, 2- (n-propoxy) ethanol, 3- (n-propoxy) -n-propanol, 3-methoxy-n-butanol, 4- (n-propoxy) -n-butanol, 4-ethoxy-n-butanol and similar alkoxyalkanols, glycol, 1,4-butanedol, 1,3-propanedol,:, 2-dihydroxybutane, 1,3-dihydruxybutane and like dihydric alcohols. Preferred alcoholic esterifying agents are n-propanol and n-butanol.

Polymers with a carbon-carbon structure are known (see »Organic Chemistry of Synthetic High Polymers ", R. W. Lenz, Intersclence Publishers, New York 1967). These polymers are made by Polymerlmi sation mönööleflnlschef monomers and monomer mixtures produced, if in the monomer no crosslinking agent is contained, long linear chains of carbon atoms are created. If the functional Olefin group contains the substituent groups, for example a carboxyl group such as In acrylic acid carboxyl groups pending linear chains of carbon atoms; hence the name polymer with Carbon-carbon backbone. For the present purpose, the polymer with carbon-carbon-6 * The basic structure of the substance contains enough carboxy-substance groups to produce the desired chemical and physical properties To enable modular ventilation. Although the hard polymer precursors used previously are essentially In suitable learning media. such as alcohols, alcohol mixtures. are insoluble, surprisingly found that the Vcrcsterung.smllld lelehi and VerällnlsmilUlg nisch In du.s lesio, m: \ lilg vcr-

22 ö2 866

networked polymer penetrates, so that useful chemical conversions within acceptable reaction times be achieved.

In the present method, a part of the hard polymer, for example from a polymer blank Manufactured lens, exchanged in a liquid medium and esterified and / or transesterified or indirectly esterified. Apart from the relatively longer reaction times and the fixed reaction force, the usual conditions to be applied and satisfactory.

The esterification is achieved by the reaction of the pendant carboxyl groups of the polymer with a Alcohol:

OO ίο

I! Il

1 _C - OH + ROH > - C - O - R + H ₂ O

or by indirect esterification of the pendant carboxyl groups by an acid halide according to the following Equations executed: "

O O

2-C-OH + PCI ₅ -C-Cl + POCI, + HCI

3 - C - Cl + ROH ► - C - O - R + HCl

I I

Transesterification is an alcohol exchange reaction that can be represented as follows:
OO

II Il ^M

4. -CO-CH ₃ + (CHj) ₂ CHCH ₂ OH> - CO-CH ₂ CH (CHj) ₂ + CH ₃ OH

The products obtained, ι. B. Lenses tend to be flexible and physiologically compatible; for example, contact lenses treated by the method of the invention cause little or no eye nuisance to most wearers. The new polymers obtained by the process according to the invention are essentially hydrophobic (they absorb less than 1 wt In accordance with the invention, the disadvantages that occur with known products, in particular lenses made from hydrogel polymers, are avoided.

In one embodiment of the invention, a hard polymer is formed by polymerizing a mixture of acrylic acid. 2-Methoxyäthylmethacrylat and 1,4-Butandloldlmethacrylat produced. Every 100 moles of the mixture contains 49.5 moles of acrylic acid, 49.5 moles of 2-methoxyethyl methacrylate and 1 mole of 1,4-butanedlol ester. The polymerization is carried out with the aid of a Breltband ultraviolet radiation and promoted by adding about 0.1% by weight (based on the mixture) of benzoin as a photoinitiator. For the polymerization, the mixture is filled in a flat container whose inner surfaces are preferably pretreated in a conventional ^ catfish 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 over after about! 2 hours. The product is a clear, non-flexible polymer with a vinyl backbone. which contains pendant carboxyl and 2-methoxyethyl groups. This polymer has a glass transition temperature of about 100 ° C.

In the next process step, the hard polymer is cut into a lens blank (button). Of the Crude is made taking into account the dimensional change that occurs during the subsequent esterification treatment (Preliminary tests showed an increase in volume of about 5%) formed into a lens. Here are known for machining, grinding and bollarding of the contact lens prepress and conventional methods for the production of plastic lenses are used (see "Contact Lens Practice", Robert Mandeli, C. Thomas; Springfield, Illinois 1965). The product obtained is a hard lens, a precursor lens, which is suitable for conversion into a new and useful lens according to the method of the invention.

Next, the precursor lens is immersed in a concentrated solution of phosphorus pentachloride in carbon disulfide (carbon disulfide) and the solution is refluxed for 20 hours. By this treatment, the pendant carboxyl groups of the hard polymers are In Säurechloridgrup- ^ω pen (-COC1) converted. The acid chloride groups are then converted into ester groups by removing the precursor lense from the carbon disulfide solution and immersing it in n-butyl alcohol, which is kept at the reflux condenser until the esterification is complete, ie about 20 hours. The esterified polymer, lens obtained is then washed with water and dried, for example in a vacuum drier at 60 ⁰ C. The dried lens which, clear and after sterilization in AutoK luven ready for use.

In another embodiment of the invention, the lens In acidified alcohol, n-ßutanol, immersed. which is held under reflux at boiling temperature for about IO hours, a period of time which

sufficient to esterify essentially all of the free carboxyl groups present. About I wt. ", (Related on the alcohol) 85% lge sulfuric acid Is a sufficient amount of acid.

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

The direct esterification treatment of the prepolymer appears to be mainly more esterified To consist of carboxyl groups. It should be noted, however, that to a certain extent other reactions, such as transesterifications, Verütherungen as well as reactions between attached carboxyl and attached 2-methoxyethyl groups (internal transesterification) can take place.

ίο Pendent carboxyl groups and carboxylic acid alkyl ester groups of lower alkylc give a polymer with Carbon-carbon basic structure Hard and at the same time form the functional points where the process attacks the invention to lower the glass transition temperature of the treated polymer. The ; j desirable relative amount of this hardness-imparting pendant groups depends on the number and An | of the pendant carboxylic acid alkyl ester groups of higher alkylc contained in the polymer. | j

Among an acrylic polymer, as it is used for the purposes of the present invention, the acrylic ι

polymer according to claim 1 to be understood, which by the usual polymerization of the acid from acrylic! lurciy | i ....

(a carboxylic acid with a double bond), the acrylic acid ester, the acrylic acid canhydride or a mixture ^!

is obtained from two or more of these monomers and has a glass transition temperature of above j

50 ° C. d

2 "This hard acrylic polymer (precursor polymer) is best made from a mixture of acid and F.sler · s

made monomers, the acrylic polymer the following components, based on 100 mol of the Polymcrl- yj

Satellite mix, contains:

1. Acrylic acid type acid In an amount of 20 to 90, preferably 50 to 75 moles;
2. an acrylic type ester in an amount of from 10 to 75, preferably from 25 to 50 moles; and

3. a customary Divinyl type crosslinking agent in an amount of 0.1 to 10, preferably 1 to 3 mol, with a molecular weight of 70 to 400

The direct esterification by treatment with an esterification mlilol can be carried out in a large temperature range : run rich. Satisfactory results are obtained in a temperature range from IO to 200 ° C obtain. Since the esterification agent must be in a liquid state. Is a to maintain fluidity Sufficient pressure is required.

In general, the time required for satisfactory conversion of the hard polymer depends on the temperature used, the alcohol used for the esterification and the presence or Absence of an esterification catalyst in the mixture. The required tent is between 1 and 100 Hours, with shorter tents being assigned higher temperatures in the specified range.

The esterification takes place in the absence of a Ks! A! Ysalor under the known thermal conditions for an esterification. Preferably, an esterification analyzer is used, which is used as an esterification agent provided alcohol is soluble. In general, conversion catalysts whose useful-

■ w wedge is known for the catalysis of alkanol-carboxylic acid compounds, also for the proposed one Process usable. Because of their general solubility in the other under consideration and is concentrated because of its relatively easy removability from the treated polymer Sulfuric acid is a preferred catalyst. When sulfuric acid to catalyze the desired conversion is used. Has a satisfactory response time between 4 and 20 hours.

• 45 As has been found, pendant carboxyl groups can be produced by known acid halide reactions are carried out in acid halide groups. As the hard precursor polymer is in the liquid reactant (i.e. the halogenating agent, if this is itself a liquid, or a solution thereof If insoluble in an inert solvent), the reaction tents are slightly longer than conventional ones Conversions. The required tent also depends on the thickness of the item, for example one

5i 'lens, and the temperature used. The conventional reactions with acid chloride used inert solvents such as carbon di-ulfld (carbon disulfide), carbon dioxide tetrachloride (Carbon tetrachloride), alkyl ethers, hydrocarbon mixtures and the like are for the present Purpose as well as the temperatures normally used in the conversion of a carboxyl group In an acid halide group can be used. These depend on the particular reagent, the solvent

and the pressure and are in the range between 10 and 200 ° C. '.

A wide variety of inorganic acid chloride forming reagents including phosphorus pentachloride. Phosphonrichlorld, Phosphorus oxychloride, thionyl chloride, sulfuryl chloride, and similar reagents are for present Purpose useful. The corresponding bromine compounds are also useful reagents, but of course more expensive and therefore less useful. Phosphorus pentachloride and thionyl chloride are used in the present invention preferred.

The esterification of the hard acrylic polymer with pendant acid halide groups is carried out. By immersing the polymer in an alcohol according to claim I and in it to a temperature in the range from 10 to 200 ° C at a pressure sufficient to keep the alcohol in the liquid state hold, and for such a long period of time that an essentially complete (> 95'Vige) conversion of the Acid halide groups (-COCi) take place in ester groups (-COOR).

The esterification is ended when the glass transition temperature of the hard acrylic polymer is below 20 ° C is lower. After the esterification reaction has ended, the esterified polymer becomes out of the agent taken out, washed free from the hydrohalic acid formed, from the absorbed or

LL OZ OUU

closed alcohol by washing with water and dried. In the transesterification according to the present Processes are pendant carboxylic acid alkyl ester groups of lower alkyls (usually methyl or Ethyl) by an acid-catalyzed exchange lactone in higher alkyls suitable for alkyl ester groups converted. A low-boiling alcohol is transformed from the ester group by a higher-boiling alcohol displaced. and the reaction proceeds to complete displacement when the low-boiling alcohol is separated off by distillation. The hard lens is immersed in the higher alcohol, the one Contains mineral acid catalyst and is kept boiling on the reflux cooler. The conversion is over, when the glass transition temperature of the hard acrylic polymer is lowered to below 20 ° C and if only a little or no low-boiling alcohol distills from the reaction fluid. To the demandinggemill.icn Achievement of the lowering of the glass transition temperature of the hard acrylic polymer should be higher Boiling alcohol according to Claim 1, generally 2 to 9 carbon atoms more in the molecule than the lower contain boiling alcohol. In the case of direct esterification, it is advisable to use a strong mineral acid, like sulfuric acid, to be used in the same proportions as there. That way it gets tough Acrylic polymer, the pendant carboxyl groups (-COOH) and pendant carboxylic acid alkyl ester groups (-COOR) contains lower alkyls through a combination of direct esterification and transesterification into a product with a satisfactory glass transition temperature lowered to below 20 "C.

I) The following examples illustrate the invention. In each case, the mixture used for the polymerization was kept at a temperature of about 25 ° C. The reaction was catalyzed by irradiating the mixture with Breliband ultraviolet light until the reaction was essentially complete. which was the case after about 4 to 1/2 hours. Klwa Oi wt .- 't. Benzoin has been mixed in with cocaine in order to improve the effectiveness of the catalyst. 1,4-Butanedoldl methacrylate was used as the crosslinking agent, which was added to the polymerizing compound in a ratio of 1 mol per 99 mol of the acrylic type monomer (s). The resulting acrylic prepolymer was generally a hard and inflexible solid.

Using standard communication methods, a portion of the product of each example became a Cut out the blank and form a lens from it. The lens was then placed in a suitable alcohol immersed in accordance with the table below, which contained 0.5 g of sulfuric acid for every 100 g. The acidified Alcohol and the lens were then for a period of time also indicated in the table on the Table kept temperature. In Examples 1 to 8, acrylic acid (AA) or acrylic acid were used and 2-methoxyethyl methacrylate (MEMA) are used. After removing the treated lens from the It was washed with alcohol and dried in a dryer at 60 ° C. The following results were obtained obtain.

example Acrylic Relative amount alcohol Esterification conditions Time [h! Remarks No. Components Mole Temp. | ° C) 6th 1
I. AA ! .0 ri-Pro ⁿ iino! 90 Soft lens, MEMA 0.0 6th satisfactory 2. AA 0.75 n-propanol 90 Soft lens. MEMA 0.25 6th Well 3. AA 0.50 n-propanol 90 Soft lens. MEMA 0.50 6th very good 4th AA 0.25 n-propanol 90 Soft lens, MEMA 0.75 4th satisfactory S. AA 1.0 Methoxyethanol 125 Soft lens, MEMA 0.0 4th satisfactory 6th AA 0.75 Methoxyethanol 125 Soft lens, MEMA 0.25 4th Well 7th AA 0.50 Methoxyethanol 125 Soft lens, MEMA 0.50 4th excellent 8th. AA 0.25 Methoxyethanol 125 Soft lens, MEMA 0.75 satisfactory

Example 9

A mixture of acrylic type monomers was made using the ultraviolet catalyst system Polymerized light benzene as above. The monomer mixture had the following composition:

Components mol%

n-butyl methacrylate 48

Acrylic anhydride 48

Ethylene glycol dimethacrylal 4

100

The obtained acrylic hard polymer was cut, molded into a contact lens, and pollen. DIc lens was then immersed in isopentanol, which was refluxed at boiling temperature for about 20 hours became. Then the treated lens was taken out of the alcohol, with water, etc., and 2 ". The lens obtained was white (glass transition temperature below 0" C) and clear.

Example 10

The previous example was repeated with n-butanol as a esterifying agent. The esterified lens was ²ⁱ soft and clear.

Examples II to 17

Soft acrylic lenses were produced by indirect esterification, for which the following monomer mixture was used as W starting material is used:

Components mol%

n-butyl methacrylal 48

Acrylic acid 4X

Ethyl glycol diniethacrylate 4

100

The polymerization was carried out as in Example 9. The obtained hard acrylic polymer became as previously made acrylate lenses. The pendent carboxyl groups of the hard lenses were then through Immerse the hard lenses in a refluxing solution of phosphorus pentachloride in carbon disulfide (Carbon disulfide) Converted to acid chloride groups for 20 hours. After that, the treated lenses esterified by immersion in the following alcohols and drying. The following results were obtained obtain:

Example alcohol remarks

No.

■ 11 n-Propanol Soft, clear, excellent lens

12 Isopropanol Soft, clear, excellent lens

13 n-butanol Soft, clear, excellent lens

14 n-Penlanol Soft, clear, excellent lens wi 15 isopentanol Soft, clear, excellent lens

16 n-IIexanol Soft, clear, uusgczcichnele lens

17 n-OeUinoi Soft, clear, exclusive lens

■ It 65

Examples 18-20
A mixture of the following acrylic monomers and crosslinking agents.

component

2-hydroxyethyl methacrylate Ethylene glycol dimethacrylate

MuI- ¹ Ki

100

L "s was polymerized according to the method of Example 9, and the reaction mixture was converted into hard lenses produced as described. The hard lenses were made using a higher alcohol and an acid catalyst (1 wt .- * sulfuric acid, based on the alcohol) transesterified. The lenses were immersed in the refluxing alcohol and the following results were obtained:

Example no. Alcohol

Remarks

18th Isopropanol flexible and clear 19th n-butanol flexible and clear 20th n-pentanol flexible and clear

Similar favorable curing results have generally also been obtained with other hard polymers made from the acrylic-type monomers and monomer mixtures specified were prepared. The received hard polymers (lenses.) could generally be replaced by one or more of the above Treatments are effectively softened and made physiologically compatible.

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

In addition to the contact lenses described in the previous examples, the method of Invention also adhesive shells in the form of corneal, half-scleral and scleral lenses of various 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.

Claims (7)

Patent claims: 1. Contact lens material, obtainable from an acrylic polymer of the following composition I. 20 to 90 mol% of units derived from the following formula R ¹ R ² C = CR ¹ COOH or (R ¹ R ² C = CR ³ CO) ₂ O, where Ri and R2 are the same or different and are hydrogen or an alkyl group with fewer than 6 carbon atoms and R ^{1 is} hydrogen or a methyl group, II. 75 to 10 months! - »units derived from the following formula R ¹ R ² C = CR ³ COOZ, wherein R ¹ , R ² and R ^{3 have} the same meaning as above and Z is an alkyl group having 1 to 11 carbon atoms, a hydroxylalkyl group having 2 to 1 ί carbon atoms or an alkoxyalkyl group having 3 to 11 carbon atoms, and III. 0.1 to 10 mol% of lightening of a common nylon-type crosslinking agent having a molecular weight of 70 to 400 by one or more of the following chemical conversions a) a direct esterification of attached carboxyl and carboxylic acid anhydride groups by reaction with a monohydric or dihydric alcohol with 1 to 15 carbon atoms in the molecule, b) an indirect esterification of pendent carboxyl and carboxylic acid anhydride groups by reaction these groups with a conventional carboxylic acid halide-forming reagent and further reaction of the carboxylic acid halides formed with at least one 1 to 15 carbon atoms in the molecule containing alcohol, c) a transesterification of attached carboxylic acid ester groups to higher carboalkoxy groups by reaction with an alcohol containing 2 to 15 carbon atoms in the molecule and a larger number of: Carbon atoms in the molecule as the alkyl of the carboalkoxy groups, Ϊ until such a proportion of the attached carboxy substances is present as carboxylic acid ester groups, that the glass transition temperature of the Acrylpolymcrlsats from above 50 ° C to such from below 20 ° C is lower. 2. A method for the production of a contact material according to claim I from an Acrylpolymerlsüi the following composition I. 20 to 90 mol% of unity derived from the following formula • to R ¹ R ² C = CR ¹ COOH or (R ¹ R ¹ C = CR ³ CO) ₂ O, where R ¹ and R ^{2 are} identical or different and are hydrogen or an alkyl group having fewer than 6 carbon atoms and R ^{3 are} hydrogen or a methyl group, II. 75 to 10 mol% of units derived from the following formula R ¹ R ² C = CR ¹ COOZ, in which R ¹ , R ² and R 'have the same meaning as above and Z is an alkyl group with 1 to 11 carbon atoms, a hydroxyalkyl group with 2 to 11 carbon atoms or an alkoxyalkyl group with Is 3 to 11 carbon atoms, as well III. 0.1 to 10 mol% units of a customary crosslinking medium of the nylon type with a molecular weight of 70 to 400, characterized in that the crosslinked acrylic polymer is one or more of the following chemical Conversions are subject to: a) a direct esterification of attached carboxyl and carboxylic acid anhydride groups by reaction with at least one monohydric or dihydric alcohol with 1 to 15 carbon atoms in the molecule, W) b) an indirect esterification of pending carboxyl and carboxylic acid anhydride groups by reacting these groups with a customary carboxylic acid analogous reagent and others Implementation of the carboxylic acid halides formed with at least one 1 to 15 carbon atoms Im Molecule containing alcohol, c) a transesterification of pending carboxylic acid ester groups to give higher carboalkoxy groups <ö reaction with an alcohol containing 2 to 15 carbon atoms in the molecule and a larger number of j Carbon atoms in the molecule as the alky! the curboalkoxy group contains, until such a proportion of the attached carboxy subsets is present as that the glass transition temperature of the Acrylpolymerlsats from above 50 ° C to such from below 20 ° C has been lowered. 3. The method according to claim 2, characterized in that the acrylic polymer before running the Method steps a) to c) is brought into the shape of a contact lens. 4. The method according to claim 2 or 3, characterized in that pending for direct esterification Carboxyl and carboxylic anhydride groups with at least one mono- or dihydric alcohol with 1 to 15 carbon atoms immersed the crosslinked acrylic polymer in the liquid alcohol and in this 1 hour to 100 hours in the range between 10 and 200 ⁰ C under a pressure sufficient to maintain the liquid state of the alcohol down to the lowering of the glass transition temperature is held. 5. The method according to claim 4, characterized in that a monohydric primary alcohol with 3 to 7 Carbon atoms being used in the molecule. 6. The method according to claim 4 or 5, characterized in that the esterification by a strong Mineral acid is catalyzed. 7. The method according to claim 2 or 3, characterized in that the indirect esterification is the carboxyl and carboxylic anhydride groups, the crosslinked acrylic polymer is immersed in a liquid or dissolved conventional carboxylic acid halide-forming reagent and immersed in this for 2 to 100 hours at a temperature Im Range between 10 and 200 ° C under a pressure sufficient to maintain the liquid state of the reagent or the solution, until a halogenation of the carboxyl and carboxylic acid anhydride groups sufficient to lower the glass transition temperature is achieved. Immersed in a liquid alcohol with 1 to 15 carbon atoms in the MöiekOi and held therein for ¹ Z ₁ hour to 100 hours at a temperature in the range between 10 and 200 ° C under a pressure sufficient to maintain the liquid state of the alcohol.