CA1241172A - Process for thermoformed articles - Google Patents

Process for thermoformed articles

Info

Publication number
CA1241172A
CA1241172A CA000455034A CA455034A CA1241172A CA 1241172 A CA1241172 A CA 1241172A CA 000455034 A CA000455034 A CA 000455034A CA 455034 A CA455034 A CA 455034A CA 1241172 A CA1241172 A CA 1241172A
Authority
CA
Canada
Prior art keywords
process according
vinyl
methacrylate
polymer
copolymer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000455034A
Other languages
French (fr)
Inventor
Ronald F. Ofstead
W. James Hammar
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
3M Co
Original Assignee
Minnesota Mining and Manufacturing Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Minnesota Mining and Manufacturing Co filed Critical Minnesota Mining and Manufacturing Co
Application granted granted Critical
Publication of CA1241172A publication Critical patent/CA1241172A/en
Expired legal-status Critical Current

Links

Landscapes

  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

Abstract of the Disclosure A process for preparing shaped articles and shaped hydrogel articles including contact lenses comprises the steps of preparing a polymer or copolymer comprising units derived from an ethylenically-unsaturated monomer bearing at least one trihaloacetoxy-substituent group, thermoforming said polymer by heating in a mold or in sheet-form at a temperature in the range of 100 to 400°C
for about 5 seconds to 15 minutes, and then cooling said polymer, to provide a shaped article, optionally, solvolyzing the resulting shaped article to provide a hydroxy-substituted polymeric shaped article, and optionally hydrating said hydroxy-substituted polymeric shaped article to provide a shaped hydrogel article.

Description

~ 32889 CAN 8A
. ~.~ .

Description PROCESS FOR THERMOFORMED ARTICLES

Field of the Invention This invention relates to thermoformed articles and a process ~or preparing such articles ~rom thermally-processable polymers. In another aspect, it relates to shaped hydrogel ar-ticles including corneal transplants, corneal implants, and contact lenses.

Background Art Polymers containing free hydroxyl groups are well-known to the art, and are useful for a variety of purposes. For example, polymers such as poly(vinyl alcohol) and poly(hydroxyethyl methacrylate) are well known, Some polymers containing hydroxyl groups, such as poly(vinyl alcohol) form excellent hydrogels, i.e,, they absorb large amounts of water without dissolving.
Hydrogels have desirable physical, optical, and physiological properties and are useful, for example, as contact lens materials. However, in order to obtain properties of strength and structural integrity, these polymers are generally cross-linked, See, for example, U.S. Patent Nos. 3,220,960 and 3,361,858. It is known in the art that the strength oE these polymers is generally related to the amount oE cross-linking present.
It is also well-known that hydroxyl-containing polymers, due to extensive hydrogen bonding interactions, are 0enerally not moldable into shapes with structural integrity, that such polymers are 0enerally considered infusibLe and non~thermopLastic, and that they undergo thermal degradation before temperatures allowing melt-flow (i.e., melting without degradation) are attained.
Furthermore, cross-linked polymeric materials are generally not moldable into shaped articles since covalent bonds between polymer molecuLes do not allow unrestricted flow oE

\\ ~

polymers even at elevated temperatures When the arnount of cross-linking is extremely low, cross-linked polymers can sometimes be formed into ilms or other thin shapes, e.g., by solvent casting. It is recoynized in the art that when the cross-linking in hydrogels is minimal, the strength is reduced, In order to provide shaped articles having hydrogel properties from hydroxyl-containing monomers, the articles also possessing adequate strength and structural integrity, two processes are used in the art. One proces~
requires forming a cross-llnked polymer, cutting and machining the cross-linked poiymer into the desired shape and configuration and then hydrating the article to provide a hydrogel article. This process utilizes labor-intensive cutting, machining, polishiny, and the like. The other proce~ss, called spin casting is described, ~or example, in U.S. Patent NoO 3,408,429 and requires that polymerization in the presence of a crosslinking agent be carried out in a rotating mold which approximates the shape of the desired article. After polymerization the article is further processed if necessary to attain the inal shape. The shaped article is then hydrated to provide a hydrogel article, An early attempt to hydrolyze vinyl trifluoro-acetate polymers is disclosed in U.S. Patent No. 2,436,144(see Example VIII). It is taught in the patent that the polymer obtained by hydrolysis is soluble in water, i.e , it is not a hydrogel. The polymers of polyvinyl trifluoroacetate obtained are described as colorlessJ
trangparent, tou~h and thermoplastic (col. 3, 11. 25-31).
Further, the patent discloses molded articles of polyvinyl trifluoroacetate having softening l:emperatures of 70C.
Thus, the poly(vinyl trifluoroacetate) and its hydrolysis product oE this patent are significantly diEferent Erom that of the present invention Poly(vinyl triEluoroacetate) has also been hydrolyzed by other workers to poly(vinyl alcohol) in studies of the stereoregularity of poly(vinyl alcohol), e.g., Harris, et al., J. Polymer Sci., Part A-l, 4, 649-677 (1966) and Pritchard, et al., J. Polymer Scl., Part A-l, 4, 707-712 (1966). These authors did not preform the poly(vinyl triEluoroacetate) into shaped articles nor recognize the possibility or significance of doing so U.S. Patent No. 3,470,124 describes monomers of the formula ~'COO-Y-OOCR", wherein R'COO is a perfluoroallcanoic acid residue, ~"COO is a residue of a polymerizable alkenoic acid; and ~ is a residue of an organic cornpound selected Erom the group consisting of aliphatic, aliphatic-aromatic and aromatic dihydric alcohols as well as the functional derivatives thereoE.
The reference relates to maximizing the properties oE the monomers and polymers obtained by incorporating fluorine into the acyl group in the materials. Thus, trifluoro-acetoxyethyl methacryl~te was not prepared, nor was its potential as a source of either poly(trifluoroacetoxyethyl methacrylate) or poly(hydroxyethyl methacrylate) appreciated.
Cross-linked and uncros.s-linked poly(vinyl alcohol) is known in the art. The properties of these forms of poly(vinyl alcohol) are known to differ as is disclosed in ~. Polymer Sci., 14, 441-457 (1976). Previous preparations of poly(vinyl alcohol) and shaped articles formed therefrom (see U,S. Paten-t No. 3,361,85~) do not exhibit the improved properties obtained in the shaped poly(vinyl alcohol) articles of the present invention.

Summary oE th~ Inv~ntion Briefly, this inventlon provides a process for malcing shaped articles which may be ocular devices COmpriSin~J thermoformillg a trihaloacetate-protected polymer, then solvolyzing the thermoformed polymer, followed by hydrating it, to provide a hydro~el shaped
2~

article with improved properties which may include improved struc-tural integrity and improved strength.
According to one aspect of the present invention there is provided a process for preparing shaped articles comprising the steps:
a. preparing a homopolymer or copolymer having a softening temperature of at least 100C comprising units derived from an ethylenically-unsaturated monomer bearing at least one trihaloa-cetoxy-substituent group, and b. thermoforming said polymer or copolymer by heating in a mold or pressing into sheets or films at a temperature in the range of 100 to 400C for 5 seconds to 15 minutes, and then cooling said polymer, to provide a shaped article.
According to another aspect of the present invention there is provided a shaped article comprising poly(trifluoroacetoxyethyl (meth)acrylate) having a softening temperature of at least 100C.
In other aspects the invention provides a shaped article, ; particularly a contact lens, prepared by the above process.
Trihaloacetate-protected polymers are thermoplastic polymeric precursors to uncross-linked hydrogel polymers, and a solvolytic process followed by hydration transforms the molded precursor polymer into a shaped hydrogel polymer. Both strength and water sorbency in the absence of covalent cross-linking may be provided in certain examples by creating semicrystalline polymer hydrogels. These polymer hydrogels are suited for use as ocular devices because they have extraordinarily high strength, flexibi-lity transparency, and are capable of absorbing large amounts of water which give high rates of oxygen permeability needed for .:

7~

corneal health.
As mentioned above, cross-linked poly(vinyl alcohol), although having good strength and hydrogel properties, is non-thermoplastic and cannot be molded into shaped articles such as contact lenses. I-t has been discovered, surprisingly, that the polymeric compositions of this invention provide thermoplastic copolymeric precursors to hydrogels which can be thermoprocessed to molded lens articles, then solvolyzed and subsequently hydrated to provide a molded hydrogel lens with high and controllable water sorbency characteristics.
It has not previously been recognized that the novel process of the present invention can provide articles with improved water absorption and in some instances improved strength even when compared to heavily cross-linked hydrogel polymers. The present process avoids both of the factors which can prevent thermal processability, i.e., hydrogen bonding by hydroxyl functional groups and cross-linking.
The present invention provides shaped hydrogels without using the step of machining or cutting a tough polymer, and thus provides a significant advantage in hydrogel processing.

- 4a -., The approach, materials, and processes described below are believed to represent a novel solution to achieving superior ocular devices giving a desirable and surprising combination of pxoperties.
As used in this application:
"ocular device" means corneal implant, corneal transplant, and contact lens;
"halo" means fluoro or chloro;
"trihaloacetate-protected polymer;' means a polymer bearing trihaloacetate-ester groups, which when solvolytically removed provides a polymer bearing hydroxyl groups;
"solvolyzable" means a compound having at least one ester group which is capable oE cleaving into a carboxyl-containing compound (e.g., amide, ester, or acid) and an alcohol in the presence of a nucleophile such as ammonia, organic amines, or water (at room temperature) or in the presence of a lower (Cl to C~) alkanol (at temperatures up to 60C);
"solvolyzing" means reacting a solvolyzable compound as decribed above;
"hydrogel" means a material which absorbs water, in the range of 10 to 95 percent by weight, without itself dissolving;
"prehydrogel" means a polymer that can be solvolyzed to give a hydrogel;
"thermally processable (thermoprocessable) polymer" means a polymer which may be heated to a temperature in the range oE 1()0 to 400C, (i.e., these polymers have a soEtening temperature oE at least 100C) and preEerably at about 200C, and then cooled to provide a shaped article which will retain its shape under ambient conditions; and "solvent-coatahle polymer" means a polymer which may be dissolved in a suitable solvent, which resulting solution may then be poured onto or over an article to be coated. The solvent is then evaporated, and the article dried. For some purposes, i e., to obtain a hydrogel coatiny, the CoatinCJ may be solvolyzed as described above, and then exposed to water to provide the desired hydrogel coating, Detailed Description The present invention provides a process for preparing shaped articles which may be ocular devices comprising the steps:
a. preparing a polymer or copolymer comprising units derived ~rom an ethylenically-unsaturated monomer bearing at least one trihaloacetoxy-substituent group;
b. thermoforming said polymer by heating in a mold or in sheet-form at a temperature in the range oE 100 to 400C for about 5 sec. to 15 min., and then cooling said polymer, to provide a shaped article;
c. optionally, solvolyzing the resulting shaped article to provide a hydroxy-substituted polymeric shaped article; and d, optionally, hydrating said hydroxy-substi-tuted polymeric shaped article to provide a shaped hydrogelarticle.
This process has general applicability to aLl ethylenically-unsaturated monomers and polymers and copolymers thereo~, the monomers being substituted by trihaloacetoxy yroups and particularly trifluoroacetoxy c~roups, since that group is readily solvolyzed in the third step of the process. Some suitablc ethylenically-unsaturated monomers include vinyl triEluoroacetate, triEluoroacetoxyethyl acrylate, triEluoroacetoxyethyl methacrylate, and substituted-propyl acrylate and methacrylate esters having the formulae R o CH2-X R O O~
I 11 / I il I
CH2=C-C-O-CII\ and CEI2=C-COCH2CHCH2X

wherein R is hydrogen or methyl, X is fluoro, chloro, bromo, iodo, perhaloacetoxy or perfluoroalkylsulfonoxy of one to three carbon atoms, and Y is trichloroacetyl or triEluoroacetyl Copolymers of the above monomers are prepared, for example, by reacting the above-described monomers with each other or with olefinic compounds such as vinyl esters, e.g., vinyl acetate, vinyl perfluoro-n-butyrate, vinyl formate and the like; vinyl ethers, such as vinyl tertiary-butyl ether; disubstituted ethylenes, e.g., derivatives of maleic, fumaric, itaconic and citraconic acid such as maleic anhydride, dimethyl itaconate, monoethyl fumarate, and the like and various monomers known to copolymerize with vinyl trifluoroacetate such as those described in column 6 of U.S. Patent No. ~,436,1~4.
Acrylate and methacrylate monomers described above form copolymers very readily with, e g., methyl, ethyl, ethoxyethyl and propyl acrylate and methacrylate, and acrylamides and methacrylamides, styrenes, and the like.
When the copolymers are obtained and the comonomer 2~ does not contain a hydrophilic group, i.e., the comonomer ; does not contribute to the hydrophilic properties of the subsequently formed hydrogel, the amount of comonomer, i.e., the weight percent, will be a variable that must be controlled. Generally, in order to obtain greater water absorption in the subsequently Eormed hydrogel more of the protected hydroxyl-containing monomers will be used although, surprisingly, this is not true for poly(vinyl triEluoroacetate) (PVTA) copolymers. Usually the amount of protected hydroxyl monomer will be greater than 50 percent, and in the case oE PVTA copolymers, the protected monomer will comprise 95 percent by weight or greater o~ the copolymeric composition. This will vary depending both upon the comonomer selected and the properties oE the copolymer which are desired or acceptable.
Some of the presently preferred copolymers Eor use in the process of the invention are copolymers of vinyl trifluoroacetate with vinyl esters having up to 6 carhon . 7,~

atom.s in the acid portion of the ester, particularly vinyl acetate, vinyl ethers having up to 8 carbon atoms, or di-substituted ethylenes such as esters or anhydrides of lower alkyl (C1 to C4) substituted or unsubstituted dicarboxylic acids having up to 8 carbon atoms, particularly maleic anhydride These copolymers are particularly useful when the units o~ vinyl trifluoro-acetate are present in an amount o at least 95 weight percent and preferably at least 98 weight percent and the units of comonomer are present in amounts oi less than about 5 percent, and most pre~erred are amounts o less than about 2 percent.
Other suitable preferred copolymers include copolymers of trifluoroacetoxyethyl methacrylate with methyl and ethoxyethyl methacrylate and copolymers o~
1,3-bis(triEluoroacetoxy)propyl-2-methacrylate with methyl methacrylate and ethoxyethyl methacrylate.
Some of the monomers useful ~or providing hydrogel properties in the articles of the invention are known, while others are novel. The preparation of some novel monomers is described in -the Examples. Two novel classes oi polymeric material are included among materials useful in the process oE the invention, namely, (1) amorphous polymers, illustrated by homopolymers oE
substituted-isopropyl acrylate and methacrylate esters, and copolymers with compatible ethylenically-unsaturated monomers (preferably at least 5 weight percent), which amorphous polymers are novel and are disclosed in assignee's copending Canadian Patent Application No, ~4 ~ , iiled the same date as this application, and 2) ~emicrystalline polymers, illustrated by copolymers oE
vinyl triiluoroacetate and S weight percent or less oE
vinyl estor or di-substituted ethylene comonomers, which are also novel, and are disclosed in assignee's copending Canadian Patent ~pplication No. ~S~/ S7~_ , filed the same date as this application.

Novel and useful trihaloacetyl-protected, e.g., trifluoroacetyl-protected polymers are obtained by polymerization oE the monomers described hereinabove. The polymerization of the monomers may be carried out by employing initiators which generate free radicaLs on application of activating energy as is conventionally used in the polymerization oE ethylenically-unsaturated monomers, Included among free-radical initiators are the conventional thermally activated initiators such as organic peroxides, azo compounds and organic hydroperoxides.
Representative examples of such initiators include benzoyl peroxide, tertiary-butyl perbenzoate, diisopropyl peroxydicarbonate, cumene hydroperoxide, azobis(isobutyronitrile), and the like. Generally, Erom about 0.1 to 5 percent by weight of thermal initiator is used.
Photoinitiators may also be employed to initiate polymerization. Such initiators are well known and have been described, ~or example, in polymerization art, e.~., Chapter II o~ "Photochemistry" by Calvert and Pitts, John ~ Wiley and Sons (1966). The preferred initiators are ; photoinitiators which ~acilitate polymerization when the composition is irradiated. Representative examples of such initiators include acyloin and derivatives thereoE, such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether and ~-methylben-zoin; dilcetones such as benzil and diacetyl, etc , ketones such as acetophenone, a,a,a-trichloroacetophenone, a,a,a-tril~romoacetophenone, ~,a-diethoxyacetophenone (DEA~P), methyl benzoylformate, 2-hydroxy-2-methyl-1-phenyl-1-propanone, o-nitro-~ ~tribromoacetophenone, benzophenone and p,~'-tet~amethylcliaminobenzopllenone; a-acylo~ime esters such as benzil-(o-ethoxycarbonyl) ~-monoxime; Icetone/amine combination~ ~uch A~ benzophenone/~-methyldiethanolamine, benzophenone/tributylamine and benzophenone/Michler's ketone; and benzilke-tals such as benzildimethyllcetal, benziLdiethyllcetal and 2,5-dichlorobenzildimethyllcetal L.2~

Normally, the photoinitiator is used in amounts ranging frorn about 0.01 to 5 percent by weight of the total monomeric composition~ When the quantity is less than 0.01 percent by weight, the photopolymerization rate becomes extremely low. If the photoinitiator is used in excess of 5 percen-t by weight, no correspondingly improved effect is observed, Preferably, about 0.1 to 1.0 percent of photoinitiator is used in the polymerizable compositions Polymeri~ation may be carried out, for e~ample, in bullc in a conventional manner. When the activating energy is ultraviolet light, the irradiation is typically carried out at a temperature of about 0 to 50C for 0.5 minutes to 5 hours or more. IE the ultraviolet photoinitiator is thermally-sensitive, following ultraviolet irradiation, the composition may be heated at 50 to 100C to complete the polymerization.
When the activating energy is only heat, polymerization is usually carried out at a temperature from ahout 40 to 140C for 5 to 50 hours. The polymerization can also be carried out in stages. Thus, in a first stage, the composition may be heated at ~0 to 60C for about 5 to ~5 hours. In a second step the composition may be heated at a temperature in the range oE 60 to 100C for several hours. It is to be understood, of course, that the polymerization conditions are not limited to such temperature and time conditions nor to the use of I ultraviolet or heat as the initiating energy. Copolymers are preferably prepared by mixing compatible monomers with the monomers of the invention in the presence of the free radical catalysts and applying heat or UV irradiation as necessary to obtain the desired reaction rate.
In order to provide the desired geometry to the shaped articles, which is an aspect of the present invention, the solid polymers and copo:Lymers are thermoprocessed (thermo~ormed). 'ri-e polymeric materials are placed in molds of various desired shapes, e.g , contact lens molds or pressed into sheets or Eilms of i 7. ~

various shapes. The polymer-filled molds oE various shapes are then heated, generally slightly above (10 to 20C
above) the melting point (Tm or PMT) of the polymer or copolymer to thermoEorm the polymeric sample. Using this technique shaped contact lenses and films, sheets and articles of various shapes can be obtained. Good retention of shape is observed when the molded polymer is solvolyzed or hydrolyzed to a hydroxyl-group substituted polymer. For example, if the polymeric articles are subsequently hydrated to form hydrogels, it is observed that the hydrogel articles retain their shape and indeed in some cases have excellent and improved strength compared to alternative materials, Injection molding is an alternative methocl of molding which is useful to prepare shaped articles from the polymers and copolymers of the present invention, Surprisingly, polymer hydrogels of poly(vinyl alcohol) prepared by the process of the present invention have two distinct improvements over related materials previously known. The strength oE these hydrogels of the invention is much greater than that of known, conventional poly(vinyl alcohol) materials such as commercially available poly(vinyl alcohol) derived from poly(vinyl acetate) by alkaline hydrolysis. When films of the poly(vinyl alcohol) of the present invention are compared to films o commercially available poly(vinyl alcohol) in stress-strain measurements, the total energies to failure, i.e., the areas under the stress-strain curves show distinct differences between the polymer films. Over twice as much energy is required to cause failure of the poly(vinyl alcohol) film of the present invention. It is hypothesized that this difle~ence in mechanical strength is related to differing intermolecular forces associated with the more highly syndiotactic stereochemical structure (i,e., the stereochemical configurations of the tertiary carbon atoms are regularly alternating) associated with the polymers of the invention. Conventional polyvinyl alcohol ~2~

has a more atactic structure (tertiary carbon atoms possessing a random stereochemical configuration) and its crystallinity properties are distinctly different.
A second major improvement is in the hydrogel properties of the polymers, Commercially available poly(vinyl alcohol) derived Erom poly(vinyl acetate) generally displays water absorption levels of about 40 weight percent or less, depending on drying time and temperature oE the polymer film used for hydration.
Poly(vinyl alcohol) polymers of the present invention, and especially copolymers of poly(vinyl alcohol) containing as little as 1 percent or less by weight of various comonomers have water absorption values which may be controllably varied to yive hydrogels which absorb much more water than these commercially available polyvinyl alcohol materials.
Aqueous liquid a~sorption levels of 10 to 90, and preferably at least 60 to 70 weight percent are obtained with polymers of the present invention. It is theorized that ionic comonomers can leacl to enhanced aqueous liquid absorption by af~ecting the crystallinity of the poly(vinyl alcohol) copolymer and by increasing the inherent absorptivity of the amorphous regions of the polymers.
Non-ionic comonomers may exert their surprisingly large effects principally by affecting polymer crystallinity.
Once the shaped polymeric article has been thermoformed it is optionally, and in most cases preferably, hydrolyzed or solvolyzed to provide a shaped article of different chemical composition. The hydrolysis or solvolysis reaction is carried out under relatively mild conditions (i.e., less than 60C) using a nucleophile capable of displacing the trihaloacetyl group from the polymer. The nucleophile used is preferably a mild base, such as methanolic ammonium hydroxide or an organic amine ~such as di-n-butylamine, morpholine or diethylamine).
Ammonium hydroxide is the preferrecl nucleophilic reagent for the solvolysis step of this process. The base chosen will regulate the ionic character of the polymer when the -l3--polymer contains a carboxylic comonomer such as maleic anhydride.
The solvolysis reaction is carried out in a diluent which is not a solvent for the trihaloacetyla~ed polymer, Eor example a diluent such as water, a lower alkanol e.g., ethanol or methanol, an ether e.g., diethyl ether or tetrahydrofuran, and the like.
The reaction time may be monitored analytically, e,g , chromatographically to determine both rate and completion of reaction, The solvolysis is preferably complete, and it is very rapid. For examplel using 9:1 methanol:al~nonium hydroxide as the solvolysis reagent, solvolysis is essentially complete in 15 minutes for most of the polymeric articles.
lS It is believed that in the cases o~ the poly~vinyl alcohol) polymers that the improved proper-ties of the shaped hydrogel articles in the absence of cross-linking may be the result of the formation of semicrystalline polymer hydrogels. In other materials other forces may be involved.
In addition to hydrogel contact lenses (soft lenses), corneal transplants and implants, mol~ed tubes, e,g., as vascular prostheses and hydrogel coatings, may be prepared by the process of this invention.
Objects and advantages of this invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention.

Example 1 A mixture of 50 g vinyl trifluoroacetate, 0.75 g vlnyl acetate and 0.25 g oE decanoyl peroxide was placed in an ampoule, The ampoule was sealed and maintained at ~7C
Eor about 16 hours, then at 57C ~or two hours. The product, poly(vinyl trifluoroacetate-co-vlnylAcetate) copolymer, was removed from the ampoule, pressed at 191C

for about 1 minute into sheets ancl solvolyzed by treating with 10 percent ammonium hydroxide in methanol. The product was poly(vinyl alcohol-co-vinyl acetate) copolymer, The nuclear mac~netic resonance spectrum of the copolymer was consist0nt with the assigned structure.

Example 2 A mixture oE 50 g vinyl triEluoroacetate, 0~75 g vinyl acetate, and 0.05 g ~-hydroxy-2-methyl-1 phenyl-l-propanone was placed in an ampoule. The ampoule was sealed and then rotated under an ultraviolet sunlamp Eor about three hours, ~ir was blown over the ampoule during the irradiation -to cool it. The product, poly(vinyl triEluoro-acetate-co-vinyl acetate) copolymer, was removed Erom the ampoule and pressed into sheets at 191C (375F) ~or two minutes. The sheets were solvolyzed in 10 percen-t ammonium hydroxide in methanol for thirty minutes to provide poly(vinyl alcohol-co-vinyl acetate) copolymer.

Example 3 A mixture of 5 9 of vinyl trifluoroacetate, 0.030 g oE maleic anhydride, and 0.025 g of azobisisobutyroni-trile was placed in an ampoule, the contents oE the ampoule were ~ro~en with liquid nitrogen, the ampoule was degassed under a vacuum and then sealed, The ampoule was heated in a bath at 47C Eor about 16 hours. The contents o~ the ampoule were found to be white solid poly(vinyl tri~luoro-acetate-maleic anhydride) copolymer, Example ~
'rhe product oE Example 3 was thermoEormed by pressing between two polyester sheets at: 191C (375E`) Eor 0.75 minutes, A polymeric article with good strength was obtained, AEter cooling, the polymer Eilm was placed in a Elask and 2U ml o~ 10 percent concentrated ammonium hydroxide in methanol was added. AEter standing Eor 15 minutes, the polymer was separated by decanting the ~2~ 7 ~.
~. ~

liquids, then dried in air to provide a poly(vinyl alcohol maleic anhydride) copolymer in which the anhydride functional group had been converted to a carboxylate and an amide group~ The copolymer was found to form a hydrogel when water was added, in that water absorption to a clear, strong elastic film occurred without dissolving the polymer sample, Examples 5 to 10 Using the method of Example 1, vinyl trifluoro-acetate was copolymerized with various monomers at a weight ratio of 99 to 1 to provide the copolymers shown in the examples oE TA~LE I:

TABLE I
Example 15 number Comonomer Copolymer .
dimethyl poly(vinyl trifluoro-itaconate acetate-co-dimethyl . itaconate) 6 monoethyl poly(vinyl -trifluoro-fumarate acetate-co-monoethyl fumarate) 7 vinyl poly(vinyl trifluoro-perEluoro- acetate-co-vinyl per-butyrate Eluorobutyrate) Using the method o~ Example 4, the copolymers oE
the above examples were thermoEormed, then so:lvolyzed and hydrated to provide the copolymers oE TA~L~3 Il.

TABLE II
Water*
sorption Exarnple Copol~neric Copolymeric (weight number starting material product _ percent) 8 poly(vinyl trifluoro- poly(vinyl alcohol- 47 co-acetate-dimethyl co-dimethyl itaconate) itaconate) 9 poly(vinyl trifluoro- poly(vinyl alcohol- 58 acetate-co-monoethyl co-monoethyl fumarate) fumarate) po]y(vinyl trifluoro- poly(vinyl alcohol- 42 acetate-co-vinyl per- co-vinyl perfluoro-fluorobutyrate) butyrate) * The water sorption oE the polymers (percent H2O) of TABLE II was a weight percent determination using the formula , percent H2O = [(W2-Wl)/W2~ x lO0 wherein W2 is a water-swollen sample weight and Wl is a dry sample weight.

Example ll To a solution of 18.0 g of trichloroacetyl chloride in lO0 ml of chloroform was aclded 14.2 g glycidyl methacrylate. The solution was warmed -to 50C, then stirred at 20C for 16 hours. The solution was then heated at reElux Eor 22 hours, the chloroform was removed hy evaporation under vacuum to provide a mixture of 68 weight percent oE l-chloro-3-(trichloroacetoxy)propyl-2-methacrylate and 32 weiyht percent of 2-chloro-3-(tri-chloroacetoxy)propyl-1-methacrylate according to in~rared and nuclear magnetic resonance spectral analyses.

,~ -17-Example 12 Into a cold solution tice bath~ of 7.1 g (50 mmole) of ylycidyl methacrylat0 in 100 ml of dich~oromethane was bubbled 6.0 g (45 mmole~ of trifluo~oacetyl chloride, The solution was allowed to stand at 20C for 16 hours then evaporated to remove low boiling components. The residue was distilled in vacuo after the addition of 0.5 g methylene blueO Fractions boiling between 53 and 60C at 0.4 mm of Hy were analyzed by gas-liquid phase chromatography to show a single major component. Infrared and nuclear magnetic resonance spectral analyses confirmed the product to he 1-chloro-3-(trifluoroacetoxy)propyl-2-methacrylate, Example 13 ~o a cold solution (0C) oE 25 g (120 mmole) of trifluoroacetic anhydride and 2 drops of trifluoroacetic acid in 100 ml of dichloromethane was added dropwise 14.2 9 (100 mmole) oE glycidyl methacrylate. The mixture~ was then allowed to warm to 20C and stirred for 20 hours. The solvent was removed by evaporation and the residue was distilled in vacuo to provide 1,3-bis(trifluoroacetoxy)-propyl-2-methacrylate, b.p. 85C/0.2 mm of Hg. The structural assignment was confirmed by infrared and nuclear magnetic resonance spectral analyses.

Example 14 A copolymer of 99.5 weight percent vinyl trifluoroacetate and 0.5 weic~ht percent maleic anhydride prepared according to the ~ethod of Example 2 was dissolved in acetone to give a 20 weight percent solution, The solution was cast onto a clear polyester film in su~icient thiclcness to give, af~,er solvent evaporation, a clear film oE approximately 0,4 mm ~0.015 inches) thiclcness. This Eilm was placed in a metal mo:Ld designed to form a single contact lens, and the mold ~heated at 200C) was closed under pressure (hydraulic ram pressure of approximately ~18-1000 p~si or 70 kg/cm~) for two minutes.
The mold was cooled and the molded lens was removed and placed in a container with 20 ml of 9/1 methanol/concentrated ammonium hydroxide for 15 minutes.
The solvolyzed contact lens was then air dried and placed in distilled water. Hydration to a clear, flexible, very strong hydrogel lens (water sorption :Level 65 weight percent) occurred.

Example 15 To a stirred solution of 6~0 g (lg.4 mmole) of trichloroacetic anhydride in 25 ml of acetonitrile was added dropwise 1.4 g of glycidyl methacrylate. The reaction was stirred for 16 hours. The solvent was removed in vacuo and the product analyzed by nuclear maynetic resonance and infrared spectra. The analysis showed that the product obtained was l,3-bis(trichloroacetoxy)-propyl-2-methacrylate.

Example 16 rrO a stirred ice-bath cooled sample of 63 g oE
trifluoroacetic anhydride was addecJ slowly 26 y oE
hydroxyethyl methacrylate, After stirring about 16 hours at 20C the solution was poured into a mixture of ice and diethyl ether. The ether layer was washed several times wi-th ice water, then with cold saturated sodium bicarbonate solution until carbon dioxide was no lonyer evolved. 'rhe ether layer was then washed with cold sodium chloride solution and dried over maynesium sulEate. Evaporation o~
the ether provided ~0.3 y oE product. Distillation Erom rne-thylene blue ~2 g) provided 21.9 g of product, triEluoro-acetoxyethyl methacrylate, b.p. 57-5~C/3.0 mm of ~Ig.
Chromatographic analy.sis sho~Jed 99 percent purity.
InErared and nuclear rnagnetic resonance spectral analyses confirmed the structural assiynment.

-19~ 7.~
Example 17 To a mixture of 3.6 g of methyl methacrylate and 14.4 g of 1/3-bis(trifluoroacetoxy)propyl-2-methacrylate (prepared according to Example 13) was added 20 mg of diisopropyl percarbonate. Nitrogen wa~ bub~led through the solution for 30 minutes. The solution WAS polymerized by heating at 60C for 4 hours in a Teflon container 1.26 mm in thickness. The resulting polymer was thermally molded by holding at 149C (300F) for 10 minutes in a contact lens mold made of metal. The lens was placed in a stirred 1 M a~ueous ammoniurn hydroxide solution for about 16 hours then rinsed with distilled water. The lens remained transparent and retained its shape.

Example 18 A mixture of 12 g of 1,3-bis(trifluoroacetoxy)-propyl 2-methacrylate (prepared according to Example 13), 1.5 g oE methyl methacrylate, 1.5 g of ethoxyethyl methacrylate and 17 mg diisopropyl percarbonate was degassed by bubbling through nitrogen gas. A film cell consisting of two glass plates separated by a washer-like spacer of poly(tetraf]uoroethylene) of about 12 mil (0.3 mm) thickness was filled with this solution and the mixture was polymerized at 60C for 4.75 hours. The Eilm was placed in 1 M ammonium hydroxide solution and stirred for 26.5 hoursO The film was then rinsed three times with distilled water and mixed in 0.9 weight percent sodium chloride solution for 18 hours. The weight percent hydration of the film was determined to be ~0.6.

Example 19 To a mixture of 3.6 g oE ethoxyethyl methacrylate and 1~.~ g of 1,3-bis(trifluoroacetoxy)-propyl-2-methacrylate (prepared according to Example 13) was added 20 mg of diisopropyl percarbonate. The solution was degassed with nitrogen and poured into a polyrnerization cell. Polymerization was carried out at 65C Eor 1~ hours.
The resulting polymer was tllermoformed at 177C (350F) Eor five minutes~ The article was placed in stirred 1 M
ammonium hydroxide for 24 hours, then rinsed in distilled water for 24 hours, to provide a hydrated article which retains 64 weight percent water.

Example 20 To 10 g of 1,3 bis(trifluoroacetoxy)propyl-2-methacrylate (prepared as in E~ample 13) was added 30 mg of diisopropyl percarbonate. ~itrogen was bubbled through the solution. After 20 minutes the solution was injected into a Eilm cavity with a 1.02 mm (~0 mil) thick Teflon~
spacer. This container was placed in a 78C oven for 3.5 hours, The homopolymer film was then immersed in water on a steam bath for 22.5 hours. The water content was determined to be 82 weight percent.

Example 21 To 17 g of trifluoroacetoxyethyl methacrylate (prepared as in Example 16) was added 25 mg of diisopropyl percarbonate. The solution was degassed with nitrogen and then used to fill a glass plate cell. The film was cured at 65C for four hours. The polymer film obtained from the cell was pressed between two pieces oE Teflon~ at 300C and was found to be thermoplastic, Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.

Claims (29)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A process for preparing shaped articles comprising the steps:
a. preparing a homopolymer or copolymer having a softening temperature of at least 100°C
comprising units derived from an ethylenically-unsaturated monomer bearing at least one trihaloacetoxy-substituent group, and b. thermoforming said polymer or copolymer by heating in a mold or pressing into sheets or films at a temperature in the range of 100 to 400°C for 5 seconds to 15 minutes, and then cooling said polymer, to provide a shaped article.
2. The process according to Claim 1 further comprising the step:
c. solvolyzing the shaped article by reacting with a nucleophile capable of displacing said trihaloacetoxy group to provide a hydroxy-substituted polymeric shaped article.
3. The process according to Claim 2 further comprising the step:
d. hydrating said hydroxy-substituted polymeric article to provide a shaped hydrogel article.
4. The process according to Claim 1 wherein said monomer is vinyl trifluoroacetoate.
5. The process according to Claim 1 wherein said monomer is selected from trihaloacetoxyethyl acrylate and trihaloacetoxyethyl methacrylate.
6. The process according to Claim 1 wherein said monomer is an isopropyl or n-propyl acrylate or methacrylate ester.
7. The process according to Claim 1 wherein said copolymer comprises comonomer units derived from additional compatible ethylenically-unsaturated comonomers.
8. The process according to Claim 2 wherein said polymer further comprises units derived from additional compatible ethylenically-unsaturated comonomers.
9. The process according to Claim 3 wherein said polymer further comprises units derived from additional compatible ethylenically-unsaturated comonomers.
10. The process according to Claim 7 wherein said comonomers are selected from vinyl esters and disubstituted ethylenes.
11. The process according to Claim 7 wherein said comonomers are selected from a) vinyl esters, b) vinyl ethers, and c) disubstituted ethylenes.
12. The process according to Claim 7 wherein said trihaloacetoxy-substituted monomer is selected from an acrylate or methacrylate and said comonomer is selected from the group consisting of vinyl acetate, vinyl perfluoro-n-butyrate, vinyl formate, methyl methacrylate, ethyl methacrylate, ethoxyethyl methacrylate, and propyl methacrylate.
13. The process according to Claim 7 wherein said trihaloacetoxy-substituted monomer is vinyl trifluoroacetate and said comonomer is a vinyl ether.
14. The process according to Claim 11 wherein said comonomer is a disubstituted ethylene selected from the group consisting of maleic anhydride, dimethyl itaconate, and monoethyl fumarate.
15. The process according to Claim 4 wherein said units of vinyl trifluoroacetate are present in an amount of at least 95 weight percent.
16. The process according to Claim 5 wherein said units of trihaloacetoxyethyl acrylate or trihaloacetoxyethyl methacrylate are present in an amount of at least 50 weight percent.
17. The process according to Claim 6 wherein said units of isopropyl or n-propyl acrylate or methacrylate ester are present in an amount of at least 50 weight percent.
18. The process according to Claim 3 wherein said hydro-gel articles comprise in the range of 10 to 90 weight percent of an aqueous liquid.
19. The process according to Claim 2 wherein said nucleo-phile is a mild base selected from ammonium hydroxide and an organic amine.
20. The process according to Claim 1 wherein said polymer comprises poly(trifluoroacetoxyethyl (meth)acrylate).
21. The process according to Claim 2 for preparing a shaped article wherein the homopolymer or copolymer is a homopolymer or copolymer of vinyl alcohol.
22. The process according to Claim 9 for preparing a shaped article wherein said copolymer is derived from vinyl tri-fluoroacetate and maleic anhydride.
23. The process according to Claim 9 for preparing a shaped article wherein said copolymer is derived from vinyl tri-fluoroacetate and vinyl acetate.
24. The process according to Claim 3 wherein said hydro-gel shaped article is a contact lens.
25. The process according to Claim 2 wherein said shaped article is a contact lens.
26. The process according to Claim 9 wherein said copoly-mer is derived from vinyl trifluoroacetate and a comonomer selected from vinyl acetate and maleic anhydride.
27. The process according to Claim 8 wherein said copoly-mer is a copolymer of polyvinyl alcohol.
28. The process according to Claim 8 wherein said comono-mer is maleic anhydride.
29. The process according to Claim 26 wherein said shaped article is a contact lens.
CA000455034A 1983-06-03 1984-05-24 Process for thermoformed articles Expired CA1241172A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US50078483A 1983-06-03 1983-06-03
US500,784 1983-06-03

Publications (1)

Publication Number Publication Date
CA1241172A true CA1241172A (en) 1988-08-30

Family

ID=23990925

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000455034A Expired CA1241172A (en) 1983-06-03 1984-05-24 Process for thermoformed articles

Country Status (1)

Country Link
CA (1) CA1241172A (en)

Similar Documents

Publication Publication Date Title
US4673539A (en) Process for thermoformed articles
US4693939A (en) Article coated with copolymer of poly(vinyl alcohol)
EP0128004B1 (en) Copolymers of poly(vinyl trifluoroacetate) or poly(vinyl alcohol), process for preparing poly(vinyl alcohol) copolymers and process for preparing shaped articles from such copolymers.
EP0128701B1 (en) Acrylate and methacrylate monomers and polymers and process for thermoformed articles
US4618649A (en) Copolymers of poly(vinyl trifluoroacetate) or poly(vinyl alcohol)
US4921884A (en) Hydroxy-substituted polymeric shaped hydrogel article
ATE85628T1 (en) PROCESS FOR MANUFACTURE OF HYDROGEL MOLDINGS, INCLUDING CONTACT LENSES.
US4786446A (en) Process of forming a hydroxy-substitute polymeric shaped article
US3787380A (en) Polymers of n-vinyl or n-allyl hetero-cyclic compounds with monoethyl-enically unsaturated esters and gly-cidyl esters
US4694037A (en) Copolymers of poly(vinyl trifluoroacetate) or poly(vinyl alcohol)
CA1241172A (en) Process for thermoformed articles
US4022960A (en) Polymers with high transparency and refractive index and process for production thereof
US4921908A (en) Copolymers of poly(vinyl trifluoroacetate) or poly(vinyl alcohol)
US4840992A (en) Copolymers of poly(vinyl trifluoroacetate) or poly(vinyl alcohol)
JPS6338042B2 (en)
JPH06102471A (en) Hydrous contact lens
US4780514A (en) Copolymers of poly(vinyl trifluoroacetate) or poly(vinyl alcohol)
WO1999006199A1 (en) Process for preparing polyvinyl alcohol contact lenses
EP0360300A1 (en) Process for producing shaped article composed of solvolyzed poly(vinyl trifluoroacetate)
EP0637761A1 (en) Water-absorptive contact lens and process for its production
JPH0286643A (en) Material for contact optical member
JPS58217511A (en) Production of transparent plastic
JPS60188906A (en) Plastic optical transmission body and its production
JPS58179210A (en) Transparent plastic
JPH11153775A (en) Production of lens for eye made of polyvinylalcohol

Legal Events

Date Code Title Description
MKEX Expiry