Note: Descriptions are shown in the official language in which they were submitted.
:~75~ !33
This invention relates to a new dextran ester-olefin compound
copolymer, which finds wide utility in such fields as contact lens,
~ artificial viscera or parts thereof, denture and other shaped articles;
I as well as a process for preparing such a copolymer. In addition, the
invention relates to dextran esters, which can not only be used for coating
materials, films, etc., but are also useful as intermediates for the
aforesaid ne~ copolymer and other compounds; as well as a process for
preparing such dextran esters.
Dextran saturated fatty acid esters, e~g., dextran acetateJ
dextran stearate, etc., that are obtained by reacting dextran with a saturated
fatty acid, e.g., acetic acid, stearic acid, etc., are known ~see United
States Patents 2,344,190 and 2,954,372). Again, dextran unsaturated fatty
~ acid ester, e.g., dextran maleate that is obtained by reacting dextran with
,, an unsaturated fatty acid, e.g., maleic acid, is also known [see Giorn.
_iochim., 10, 373 - 9 (1961)~. The ormer dextran esters are known to be
useful ~or such purposes as, say, the resinous component of coating materials
such as paints and lacquers and of protective creams for hand. On the other
hand, it IS disclosed that when sulfuric acid ester was prepared using the
latter dextran ester as intermediates, such medical activities as cl~arifying
activity or anticoagulant activity was not exhibited at all.
However~ the dextran esters derived from dextran and the two
acids of the unsaturated and saturated acids have not been known heretofore.
The graft polymers derived from dextran and such polymerizable
olefin compounds as methyl methacrylate and useful for such purposes as
contact lens, artificial viscera, etc.J are also known along with the process
for their preparation (see West German Laid-Open Patent 2,334,530~.
' ~ Our researches were carried out with a view to providing a resin
'~ ha~ing pToperties that were still more improved than in the case of the
resin disclosed in the foregoing West German ~aid~Open Patent 2,334,530 and,
as a consequence, we discovered that it ~as readily possible to prepare a ne~
i
dextran ester-olefin compound copolymer derived from a dextran ester,
preferably a mixed acid ester of dextran derived from dextran and an
:~ ~
1 -- .
.. .
.
. :; .
56~33
unsaturated acid and a saturated acid, and a polymerizable ole:Ein compound.
It was further found that this new copolymer, when used, say, for
contact lens and other purposes, possessed such desirable and superior
properties as outstandingly high hardness, high softening point and other
improved physical properties, as well as improved acid resistance and
improvements in its other chemical properties.
We also found that a shaped article of desired configuration could
be obtained in a single operation by polymerizing this new copolymer in a mold
in the presence or absence of a polymerization initiator.
In addition, it was found that this new copolymer conveniently
possesses a thermoplasticity of a degree such as to make possible its melt- - .
shaping notwithstanding its possession of the ability to form a network
structure of considerably high degree as compared with the conventional graft
polymer obtained from dextran and a polymerizable olefin compound. Furthermore,
it was found that the interaction of the invention copolymer with, say, the
tissues of living body was exceedingly small, of a degree so small as to be
ignorable with the consequence that it was especially suitable in making such
shaped articles as contact lens~ artificial viscera or parts thereof, dentures
and denturebase.
This invention therefore seeks to provide a new dextran ester-olefin
compound copolymer possessing the various excellent properties such as above
described and a process for preparing such a new copolymer.
This invention also seeks to provide a new mixed acid ester of
dextran, which not only is useful as an intermediate for preparing the fore-
going copolymer but also is useful for preparing coating materials and films;
as well as a process for preparing such a dextran ester.
Furthermore, this invention seeks to provide shaped articles of the
foregoing copolymer and a process for producing same.
Therefore this invention provides for a dextran ester-olefin compound
copolymer comprising a unit derived from a dextran ester of the following
formula ~1)
- 2 -
., ~ .
~ ,, . . .. ,: ..
; : , : : , : :
1~7~6~33
o o
~C6H7O2~OII)3_(m~n) ~O-C-R )m . ~O-C-R )~ x (1)
wherein Rl is a C2-Cls organic radical having the /C-C~ bond derived from the
/C_C~ bond of an unsaturated acid, R2 is a Cl-CL8 alkyl radical, m is a
positive number having a value of 0<m ~3, _ is a positive number having a
value of 0~n~3, with the proviso that mtn~3, and x is a positive number having :-
a value of 5 or more; and a unit derived from a polymerizable olefin compound
of the following formula ~2)
R R
- C - I - (2)
R4 R6
wherein R3, R4 and R5 are each selected from the group consisting of hydrogen
cmd CH3 and R6 is a member of the group consisting of -~-o-R7 where R is a
member of the class consisting of hydrogen, Cl-C18 alkyl radicals, cyclohexyl
radical, lower alkyl-substituted cyclohexyl radical, Cl-C8 hydroxyalkyl
radicals, Cl-C8 aminoalkyl radicals, Cl-C8 dialkylamino-alkyl radicals,
glycidyl radical, tetrahydrofuran radical, lower alkyl-substituted tetrahydro-
furan radical, benzyl radical and ~CH2CH2O~yCH2CH2OH radical where ~ is a
positive integer from 1 to 10 ; -~-N(R10)2 where the two R10's which may be
the same or different are members of the group consisting of hydrogen and a
Cl-C4 alkyl radical; -CN; OH; O-C-R8 where R8 is a Cl-C8 alkyl radical.
'~ The unsaturated acids and acid anhydrides or acid halides thereof,
~ 20 from which the aforementioned C2 - C12 organic radical Rl is derived, include
.
I - 3 -
~'
~ .
. ~o :
'',
', ' , : ; '' '~ ' ' '' ' '' ' ' ' ' ' ' ' ' '
11~7568~
the C3 - Clg unsaturated acids and acid anhydrides or acid halides thereof.
As specific examples of such unsaturated acids, there can be mentioned such
alpha-beta unsaturated acids as acrylic acid, methacrylic acid, crotonic
acid, isocrotonic acid beta, beta-dimethylacrylic acid, angelic acid, tiglic
acid, and such unsaturated acids as maleic acid, fumaric acid, citraconic
acid, mesaconic acid, itaconic acid, aconitic acid, and oleic acid. On the
other hand, as ~he acid anhydrides or acid halides, included are the anhydri-
des or halides (e.g. acid chloride) of the foregoing unsaturated acids. The
C2 ~ C6 organic radicals are preferred as the radical Rl. Hence, the
C3 - C7 acids, and especially the aliphatic unsaturated acids, are preferred
as the foregoing unsaturated acids. These unsaturated acids and the acid
anhydrides or acid halides thereof can be used either singly or in combina-
tion of two or more thereof. On the other hand, the saturated acids and the
acid anhydrides or acid halides thereof, from which the aforementioned
radical R2 is derived, include the C2 - C19 saturated acids and the acid
anhydrides or acid halides thereof. As specific examples of such saturated
; acids, mention can be made of such saturated acids as formic acid, acetic
acid, propionic acid, butyric acid, palmitic acid and stearic acid. On the
other hand, as the acid anhydrides or acid halides, included are the
a~hydrides or acid halides ~e.g. acid chloride) of the above acids. These
saturated acids and the acid anhydrides or acid halides thereof can be used
either singly or in combination of two or more thereof.
As the polymerizable olefin compound from which the unit expressed
by the foregoing formula ~2) is derived, there can be mentioned the alpha,
beta-unsaturated acids such, for example, as acrylic acid and methacrylic
f acld; the Cl - C18 alkyl esters such? for example, as the methyl, ethyl,
propyl, butyl, decyl, lauryl and stearyl esters of these alpha, beta-
unsaturated acids; cyclohexyl ester`or lower alkyl-substituted cyclohexyl
ester, f~r example, 2-ethylcyclohexyl ester, o the foregoing alpha, beta-
unsaturated acids; the Cl - C8 hydroxyalkyl esters of the alpha, beta-
unsaturated acids such as the 2-hydroxyethyl esters, 2-hydroxypropyl ester
and 2-hydroxybutyl esters of the foregoing alpha, beta-unsaturated acids;
.': '
- 4 - ~
.. . . . . : : - ~
1L~75G~33
the amides or alkyl amides of the foregoing alphaJ beta-unsaturated acids
such as acrylamide, methacryl-amideJ acryl- or methacryldimethylamide and
acryl- or methacryldiethylamide; the Cl - C8 aminoalkyl esters such as the
aminomethyl J aminoethyl and aminobutyl esters of the aforesaid alphaJ beta-
unsaturated acids; the Cl - C8 dialkylaminoalkyl ester such as the dimethyl-
aminoethylJ diethylaminoethyl dimethylaminobutyl and diethylaminobutyl esters
of the aforesaid alpha, beta-unsaturated acids; ~he glycidyl esters of the
foregoing alpha, beta-unsa~ura~ed acids; the tetrahydrofurfuryl esters of the
aforesaid alpha, beta-unsaturated acids; the benzyl esters of the foregoing
10 alpha, beta-unsaturated acids; the polyethylene glycol monoesters such as the
diethylene glycol, triethylene glycol and tetraethylene glycol monoesters of
the aforesaid alpha, beta-unsaturated acids; the nitriles of the foregoing
alpha, beta-unsaturated acids such as acrylonitrile and methacrylonitrile;
vinyl alcohol, methylvinyl alcohol and dimethylvinyl alcohol; the Cl - C~
alkyl esters of vinyl alcohol or the foregoing methyl-substituted vinyl
alcohols such as vinyl acetate, vinyl propionate and vinyl butylate; styrene;
alpha-methylstyrene and vinyl toluene; vinylpyridine; vinylpyrrolidone;
and vinylmethylpyrrolidone.
These polymerizable olefin compourds can be used either singly or
in comhination of two or more thereof.
The above-described dextran ester-olefin compound copolymer of this
invention is insoluble in a wide range of the conventional organic solvents
such, for example, as the alcohol ketones, ethers, esters, aromatic hydro-
carbons, organic acids and organic bases. Hence, its molecular weight cannot
be determined by the usual methods o~ measuring the molecular weight of the
high-molecular-weight compounds. The invention copolymer has a Rockwell
hardness ~M scale~ of above about 20, usually above about 25, and frequently
; as much as about 150. Again, the invention copolymer is insoluble at 50C.
in chloroform, acetone, dimethylformamide, dimethyl sulfoxide, dioxane,
benzene and pyridine.
The proportion of the formula (1) units to the formula ~2) units
in the new copolymer of this invention can be suitably chosen. For example,
. :
. .
.
1~756~33
the usual practice is to use at least about 50, usually about 50 - about
10,000, of the formula ~2) units per 100 formula ~1) units.
The above-described dextran ester-olefin con~pou~d copolymer of
this invention can be prepared by reacting in the presence or absence or a
polymerization initiator a dextran ester of the following formula ~1')
O O
[C6H72~H)3 ~m~n~ t O.C - R )m t - C - R )n]x (1')
where Rl is a C2 C18 organic radical having the ~C = C~ bond, R2 is a
Cl - C18 alkyl radical, _ is a positive number having a value of O~m~3, _ is
a positive number having a value of O~nc3, with the proviso that m ~ n ~ 3,
and x is a positive number having a value of 5 or more; with a polymerizable
olefin compound of the following formula ~2')
R \ R5
C=C ~2')
I R R6
¦ wherein R3, R4 and R5 are each selected from the group consisti~g of hydrogen
I and CH3, R6 is a member of the gTOUp consisting of -C-O-R ~where R is a
member of the class consisting of hydrogen, Cl - C18 alkyl radicals,
1 20 cyclohexyl radical, lower alkyl-substituted cyclohexyl radical, Cl - C8
s hydroxyalkyl radicals, -N ~R10)2 where the two R10's, which may be the same
or diEferent, are either hydrogen or a Cl - C~ alkyl radical, Cl - C8
aminoalkyl radicals, Cl - C8 dialkylaminoalkyl radicals, glyciclyl radical,
I tetrahydrofuran radical, lower alkyl-substituted tetrahydrofuran radical,
s~ benzyl radical and the-~-CH2CH2- ~ 2CH20H radical where y is a positive
integer fro~ 1 to 10~;
~,: o o O O
t 11 11 0 Q ~\
-C-CN; -OH; -O-C-RU where R~ is a Cl - C8 alkyl radical; ~ ~ ~
~ H ~ ~ ~ and - ~ R where R~ is a
, ~ .
' '
- 6 -
: '
. ,.
~C~7~683
lower alkyl radical.
Further, the starting dextran ester of the foregoing formula (1')
can he prepared by the following process (A) or (B).
Process A.
The compound of formula (1') can be prepared by reac~ing dextran
with either an unsaturated acid of the formula HOOCRl where Rl is a
C2 - C18 organic radical having the `C=C' bond or said unsaturated acid and
a sa~urated acid of the formula H~OCR2 where R2 is a Cl - C18 alkyl radical
or an acid anhydride of said acid, in the presence of an acid catalyst.
Process B.
It is also possible to prepare the compound of formula (1') in the
following manner. Dextran is reacted in a nonacidic liquid medium under
basic conditions with either a compound selected from the group consisting of
an unsaturated acid of the formula HOOCRl where Rl is a C2 - C18 organic
radical having the `C=C' bond and the acid anhydrides and acid halides there-
of or said compound and a compownd selected from the group consisting of a
saturated acid of the formula ~OOCR2 where R2 is a Cl - C18 alkyl radical and
the acid ~nhydrides and acid halides thereof.
Of the compounds of the aforesaid formula (1'), the dextran esters
having the ollowing ~ormula (1") are compounds that have yet to be mentioned
in the literature.
O O
[C6H72~H)3 ~m+n) ~~~~ . C - R )m. ~ n x
wherein Rl is a C2 - C18 organic radical having the `C = C~ bond, R2 is a
Cl - C18 alkyl radical, m i5 a positive number having a value of O~m~3, _ is
a positive number having a value of Ocn~3, with the proviso that m + n~3,
.
and x is a positive number having a value of 5 or more. These compounds can
be prepared by using in Process A the two components of said unsaturated acid
and acid saturated acid or the acid anhydrides thereof, or by using in Process
B a compound of the group consisting of said unsaturated acids and the
derivatives thereoF and a compound of the group consisting of said saturated
.
7 _
- .. . ~ , :
~L~7~68~
acid and the derivatives thereof.
As specific examples of the unsaturated and saturated acids of the
foregoing formulas HOOCRl and COOCR2 or the acid anhydrides or acid halides
of these acids to-be used in the aforementioned Processes A and B, the same
examples previously given in connection with formula ~1) as ~nsaturated and
saturated acids from which the radicals Rl and R2 of the form~lla (1) are
derived and the acid anhydrides and acid halides thereof can be mentioned.
Process A can be carried out in the presence or absence of a
solvent. Examples of usable solvents include dioxane and the aromatic
hydrocarbons such as benzene, toluene and xylene. On the other hand, as the
acid catalyst, preferably used are sulfuric acid, sulfoacetic acid, perchloric
acid and trifuloroacetic anhydride.
As preferred modcs of the Process A, i.e., the case where a mixed
ester of a saturated acid and an unsaturated acid is prepared, there is a
method which comprises reacting dextran with an unsaturated acid of the
formula HOOCRl where Rl is as above defined, and an anhydride of a
saturated acid of the formula HOOCR2, where R2 is as above defined, in the
presence of an acid catalyst selected from the group consisting of sulfuric
acid, sulfoacetic acid and perchloric acid, as well as a method which
comprises reacting dextran with an unsaturated acid of the formula HOOCRl , -
where Rl is as above defined, and a saturated acid of the formula ~OOCR2,
where R2 is as above defined, in the presence of trifluoroacetic anhydride
and sulfuric acid.
On the other hand, the Process B is carried out in a nonacidic
liquid medium under basic conditions. When the nonacidic liquid medium
itself is a basic medium, such, for example, as pyridine, dimethylformamideJ
.
~ormamide, acetamide, quinoline or picoline, it is not especially necessary
that an alkaline substance be copresent for achieving the basic conditio~s.
However, when a nonacidic liquid medium such as dioxane and the aromatic
hydrocarbons such as toluene, benzene and xylene are used, the reaction is
carried out in the copresence of a suitable alkaline substance. As the
alkaline substance for this purpose, ~he organic and inorganic bases can be
.
3L075683
used. For example, usable are such compounds as the alkali metal
hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkali
metal salts of the Cl - C8 fatty acids such as acetic acid, formic acid and
propionic acid, as well as the afore~entioned basic media.
As preferred modes of practicing the Process B, the following modes
can be given by way of illustration. A method which comprises reactiTIg
dextran with either an acid anhydride or acid halide of an unsaturated acid
of the formula HOOCRl , where Rl is as above defined, or said acid
anhydride or acid halide and an acid anhydride or acid halide of a saturated
acid of the formula HOOCR2, where R2 is as above defined, in a basic medium
such as hereinbefore indicated; a method comprising reacting dextran with an
unsaturated acid of the formula HOOCRl , where Rl is as above defined, and
an acid anhydride of a saturated acid of the formula HOOCR2, where R2 is as
above defined, in the aforesaid aromatic hydrocarbon or dioxane medium in the
presence of the aforementioned alkaline substance; and a method which
comprises reacting dextran with an unsaturated acid of the formula ~IOOCR
where Rl is as above defined, and an acid anhydride of a saturated acid of
the formula HOOCR2, where R2 is as above defined, in dimethylformamide in the
presence of one of the aforementioned alkaline substances, of which especially
20 preferred is potassium acetate. In this case, especially preferred is a
procedure consisting of first treating the dextran in~ say, an aqueous
potassium acetate solution, drying the treated dextran and thereafter
carryout the reaction, since by operating in this manner the reaction proceeds
more smoothly.
In preparing the dextran ester of formula (1') it is preferred
that the reaction be carried out without causing a split of the double bond
of the unsaturated acid of the formula ~OOCRl . The reaction can be carried
out in the presence of a polymerization inhibitor, if necessary. As such
poly~erization inhibitor, there can be mentioned such compounds as
30 hydroquinone and para methoxy phenol. The reaction is preferably carried out
at as low a temperature as possible. In the case of the Process A, the
reaction is preferably carried out at below about 40C., and more preferably ~ -
,
_ g
; . - .
756E~3
below about 35C. It is usually carried out at room temperature, but may be
also carried out under cooling, if desired. A temperature ranging between
about 0C. and about ~0C. can usually be employed. The reaction time can
be suitably varied in the range of about 1/2 - 24 hours. In the case of
Process B, a temperature ranging between about 20C. and about 60C. can
be employed. Preferably, a temperature from about 60C. to about 120C. is
employed for shortening the reaction time.
The starting dextran esters, which are obtained as above described,
can be suitably chosen in accordance with the properties that are desired in
the dextran ester-olefin compound copolymer of this invention. For instance,
when it is desired to prepare a copolymer suitable for obtaining shaped
articles having greater mechanical strengths such as flexural and tensile
strengths, preferred is that whose n in formula (1') ~degree of esterifica-
tion of the saturated acid) is of a larger value, for example, one in which
the n ranges between about 1.5 and 3. On the other hand, the value of m
affects the degree of cross-linking o~ the resulting copolymer and the
wettability with respect to tear and humor of shaped article obtained from
this copolymer. When the copolymer is to be used for contact lens or viscera,
consideration is given to the matter of achieving a balance between the
mecha~ical strengths and the foregoing wettability, and the n and m values
preferred in this case are those where about l~n~about 2.5 and about 0.1 m
about 1.5. Of course, since these properties that are ascribable to the
values of m and _ mutually affect each other, these values cannot be decided
unqualifiedly. However, the desirable values of m and n for the starting
dextran ester can be readily determined experimently in accordance with the
intended use of the resulting copolymer.
As the polymerizable olefin cor~ound of the a~orementioned formula
; (2') to be reacted with the foregoing formula ~1') dextran ester, the same ~`
: examples previously given in connection with the formula (2) as polymerizable
ole~in cor~ounds from which the unit of formula ~2) is derived can be
rnentioned.
The invention dextran ester-olefin compound copolymer comprised of
.
- 10 -
-
~1~7~61~3
the ~ormula units (1) and formula units (2) can be obtained by reacting a
compound of the foregoing formula (1') with a compound of the foregoing
formula (2') in the presence or absence of a polymerization initiator. The
reaction can be carried out, for example, by such polymerization processes
as solution, suspension, emulsion and bulk polymerization processes. The
employment of the bulk polymerization process is especially preferred, since
the shaped article of desired form can be obtained in a single operation in
the mold in which it has been cast.
In the case where the solution polymerization process is to be
employed, the dextran ester of formula (1') and the polymerizable olefin
compound of formula (2') are first dissolved in a suitable solvent such, for
example~ as benzene, tolene, xylene) cresol, dioxane, tetrahydrofuran,
cyclohexane, chloroform, dichlorethane, acetone, methyl ethyl ketone,
cyclohexanone, dimethylformamide and dimethyl sulfoxide, in a polymerization
reactor, after which the reaction is carried out in the presence of a
solution polymerization inltiator such, for example, as benzoyl peroxide,
I lauroyl peroxide, di-t-butylperoxyphthalate, azobisisobutyronitrile,
phenylazoallylsulfonic acid and N-nitroso-N-acyl compounds. In this case the
reaction is preferably carried out by heating the reactants for 1-24 hours at
50-200C. in preferably an atmosphere of an inert gas such as nitrogen.
The proportions in which the formula (1') dextran ester and the
formula (2') polymerizable olefin compound are used can be suitably chosen in
accordance with the end desired. While there is imposed no particular
restriction as to the amount in which the solvent is used, in those cases
;
where the viscosity of the reaction soIution rises abnormally with the
progress of the polymerization reaction, it is best to use the solvent in
such an amount as to preclude such a possibility, since such a situation
might cause the reaction to proceed nonuniformly. The use of the polymeriza-
~; tion initiator in an amount of about 0.1% to about 1.5% by weight based on
the total weight of the formula (1') dextran ester and the formula (2')
poIymerizable olefin compound will do.
After completion of the reaction, the product can be separated and
.
.:, - -, ` . , . : : ' ':' :'
~5~83
collected by filtration or centrifugation followed by purification~ if
necessary, and thereafter drying under reduced pressure to obtain the
intended copolymer. If d~sired, the intended product can be separated after
completion of the reaction by such procedures as distilling o~f of the
solvent or by adding a poor solvent for the copolymer, such, for example,
as water, methanol of acetone, to the reaction product and collecting the
intended product in the form of a precipitate.
When the suspension polymerization process is used, the formula ~1')
dextran ester and the formula (2') polymerizable olefin con~ound are dispersed
in a poor solvent, preferably water, after which the reaction is carried out
preferably in an atmosphere of an inert gas such as nitrogen with stirring.
In this case, a stabilizer such, for example, as calcium carbonate, magnesium
carbonate, alumina and gelatin can be added for facilitating the dispersion
of the components as well as to ensure that the reaction proceeds smoothly.
As the suspension polymerization initiator) a compound which is insoluble in
water but soluble in the formula (2') polymerizable olefin compound, such as
benzoyl peroxide, is preferably used. Howe~er, also usable are those
compounds which are soluble in water but ~insoluble in the polymerizable
` olefin compound such, for example, as ammonium persulfate. Water is
preferably used in an amount of about 3 - 10 fold by volume of the total
amount of the formula (1') dextran ester and the formula (2') polymerizable
olefin compound. On the other hand, the use of the stabilizer in an amount
of not more than 1~ by weight of the foregoing total and the polymerization
initiator in an amount on the order of 0.1 - 1.5% by weight o~ the foregoing
total will do. A reaction temperature of preferably about 40 to 90C. is
used, while the reaction time employed is usually on the order of 1 - 24
hoursG After completion of the reaction, a granular product is separated
followed by purification, if necessary, and thereafter dried to obtain the
intended copolymer.
On the other hand, in ~he emulsion polymerization process the
formula (l') dextran ester and the formula (2') polymerizable olefin compound
~ are suspended in water and, after adding an emulsifier and a polymerization
.
- 12 -
.~ , ' '~.
.
, ~ :. . : '. . ,. . : .
i683
initiator, the reactants are reacted preferably in an atmosphere of an inert
gas such as nitrogen with stirring. Water is used preferably in an amount
about 2 - 5 - fold by volume of the total amount of the formula ~1') dextran
ester and the formula (2') polymeri_able olefin compound. On the other hand,
as the usable emulsifier, included are the surfactants of the group consisting
of the cationic, anionic and nonionic suractants. The surfactant is
preferably used in an amount of about 0.1 - 5% by weight of the total weight
of the formula (1') dextran ester and the formula (2') polymeri7able olefin
compound. As the emulsion polymerization initiator, the water-soluble
polymerization initiators such, for example, as the persulfates, percarbonates
and hydrogen peroxide are preferably used in an amount of about O.l - 1~5%
by weight of the forego~ng total. The reaction is preferably carried out at
a temperature of 20 - 90C. for a reaction time of about 1-24 hours. After
completion of the reaction, either the product can be flocculated by adding -~
an electrolyte such, for example, as sodium chloride, calcium chloride or
sodium sulfate to the reaction solution, or the reaction solution can be
introduced into an organic solvent such, for ex~mple, as methanol to form a
precipitate, which is separated followed by purification, if necessary, and
thereaft0r dried to obtain a powdery copolymer.
Further, when in accordance with a preferred mode of practicing
the inventio~ process the bulk polymerization technique is employed, the
intended product can be readily obtained by either dissolving or swelling the
formula ~ dextran ester in the ormula (2') polymerizable olefin compound
and then carrying out the reaction after adding a polymerization initiator.
In this case the proportion in which the formula ('') dextran ester and the
formula ~2') polymerizable olefin compound are used can be suitably chosen in
ccordance with the end desired. ~sable as the polymerization initiator in
this~process are, for example, benzoyl peroxideJ lauroyl peroxide, di-t-
butyroperoxyphthalate, azobisisbutyronitrile, phenyla~oallylsulfonic acid
and N-nitroso-N-acyl compounds. These polymerization initiators are prefer-
ably used in an amount of about 0.1 - 1.5% by weight based on the total
welght of the formula ~1') dextran ester and the formula ~2') polymerizable
,~,
- 13 -
-~ . . . . . - - : . . . :
~7~83
olefin compound. The bulk polymerization reaction is carried out, if
necessary, under an atmosphere of an inert gas such as nitrogen preferably at
ahOut 30 - 60C. for from several hours to several days, following which the
reaction is best continued for a further period of about 1 - 10 hours at
about 60 - 110C. If in carrying ou~ the reaction a violent polymerization
reaction occurs and bubbles are formed, ~he reaction time should be suitably
prolonged by reducing the amount of the polymerization initiator used and/or
by lowering the reaction temperature. If necessary, the reaction product
can be further annealed a~ about 60 - 90C. for 2 - 24 hours. One of the
important features of the invention process is that the dextran ester
copolymer can be obtained by this bulk polymerization process. In all of the
hereinbefore-described polymerization processes other than the bulk polymeri-
zation process the product is always obtained as powders or granules. Hence,
it is impossible to obtain the product directly in the form of a shaped
article such, for example, as sheets, rods, etc., in the case of the
polymerization processes other than the bulk polymerization process. On the
other hand, since in the case o the bulk polymerization process, the :Eormula
~1') dextran ester and the formula (2') polymerizable olefin compound are
placed from the outset in a mold and, after adding and dissolving therein a
polymerization inltiator, the reaction is carried out by heating the reactants,
this process is extremely advantageous from the standpoint of efficiency
and economy.
Needless to say, the powdery or granular products obtained by the
aforementloned other processes can also be fabricated into a desired shaped
article by processing the powdery or granular products by a suitable molding
~, method such as pressing, injection, extrusion or other methods.
The dextran ester used in the bulk polymerization process must be
one which dissolves in the polymerizable olefin compound or at least is
swelled thereby. As this solubility varies in accordance with the clas-s and
content of the acid radical of the ester, these factoTs should be given
consideration in preparing the dextran ester. For instance, of the herein-
before-described methods of preparing the dextran ester, the Process B is
`'":
:, ,~ ,, : . :
1~7~6~33
especially preferred. Employment of the method of reacting the dextran with
a saturated acid anhydride and an unsaturated acid ln one of the previously
indicated basic solvents, e.g., dimethylformamide, etc., in the presence or
absence of one of the previously indicated alkaline substances such as
potassium acetate, etc., is preferred. ~e employment of this method is an
advantage, because a dextran ester of a quality especially suitable for use
in the bulk polymeri~ation process can be obtained in good yield.
While the various polymerization methods have been described
hereinabove with particular reference to an embodimen~ of using a
10 polymerization initiator, it should be understood that the polymeri7ations
can also be performed in the absence of initiators, for example by heating or
by irradiation of ultraviolet rays.
In carrying out the hereinbefore-described various polymeri~ation
processes, it is also possible to carry out the reaction in the copresence of
a coloring agent and a plasticizer by adding these additives to, say, the
formula (2') polymerizable olefin compound before reacting it with the
, dextran ester thereby causing the inco~poration in the resulting copolymer
of these additives.
The invention dextran ester-olefin compound copolymer that has been
20 prepared in the manner described above are difficultly soluble in such organic
solvents as, for example, benzene, chloroform and acetone, which can dissolve
the homopolymers of the starting formula (1') dextran ester and starting
' formula (2') polymerizable olefin compound.
In the accompanying drawings are shown infrared spectra of the
starting dextran ester OlC the hereinafter given Example 1 (Figure 1) and the
reaction product of this ester and methyl methacrylate (Figure 2), as well as
that of a methyl methacrylate polymer (Figure 3).
The principal absorptions exhibîted in the IR spectrum of dextran
ester of ~igure 1 are as follows: ~1) 1750 cm 1 yC=O, 1020 and 1150 cm 1
C-0-C symmetric and antisymmetric stretching vibrations; ~2) 1370 cm 1 ~C'H,
1230 cm 1 yC-O, 1635 cm 1 yC=C, 809 and 835 cm 1 C-H out-of-plane
deformation vibrations of R-CH=CH and R-C=C~I , (4) 3~50 cm ; yOH, 770 and
2 2
.: . !; .' ~ '
~56B3
,.
910 cm : vibration of the pyranose ring, 852 cm 1 ~Cl-H.
- Of these) group ~1) derives from an organic acid ester, group (2),
derives from especially an acetic acid ester, group (3) derives fror,~ acrylic
and methacrylic radicals, and group (4) derives from dextran.
As is apparent from Figure 2 of the accompanying drawings, the
absorption ascribable to ~ C=C~ seen in the IR spectrum of dextran ester
(Figure 1) is not seen in the IR spectrum of the reaction product. On the
other hand, absorptions ascribable to the alpha-l, 6-pyranose ring and ~C=O
or C-CH3 are seen in this spectrum. Further, as hereinbefore indicated, the
reaction product is insoluble in the common solvents for the dextran ester
and methyl methacrylate polymer, which have been used as the starting mater-
ials, and especially in acetone.
It is thus seen from the foregoing facts that the product obtained
by the invention process is a copolymer containing the units of the afore-
mentioned formulas (1) and t2). Since a variety of combinations of these
units are possible, it is impossible to indicate the chemical structure of
the invention product unqualifiedly. ~loweverj by way of illustration, there
can be shown one having a structure such as follows:
..
. .
i :
'"
.~:
,:
- 16 -
, '
: - . .
,, . , ~ .
~75683
!
.~
~:: ~ ~ : `
~ a)
,., __ ,
o-$
." ~ o ~ o o ~
~ ~ O
o
, , 8 ~ `
, ~ N q
0 ~ O ~ .. ,
: " , ' ' '
''` ,
" ~i ~ ~ ' ` ': .
; ~ :
.` : 7 -
.i .
A ~
~75~l~3
The dextran ester copolymer obtained by the invention process
possessing thermoplasticity can be made into shaped articles to be used for
various purposes. It can be used as the starting material for making contact
lens, as well as artificial organs or parts thereof such as artificial blood
vessels, bones, kiclney and cornea, denture and denturebase.
The molding method to be used can be freely chosen. For example,
there is the bulk polymerization process wherein the shaped ar~icle is obtain-
ed directly by carrying out the copolymerization reaction in a mold having
the form of the desired shaped article. Again, there is a method in which
a cast resinous sheet obtained by ~he bulk polymerization process is
processed by application of heat. In the case of the powdery or granular
~pellet) copolymer, such molding methods as injection, extrusion and
compression molding as well as casting from a solution can be employed. In
addition, the monomer-polymer molding method can also be employed.
For instance, in preparing contact lens of a copolymer obtained
by the bulk polymerization process, the following procedures can be employed.
First, for example, an acetic acid-methacrylic acid-acrylic acid mixed ester
of dextran and methyl methacrylate are dissolved at a weight ratio of 1:1 -
10, and preferably 1:2 - 5, in a glass tube, following which the mixture is
heated first for 24 hours at 30 - 40C. and then Eor 4 hours at 80 - 100C.
in the presence of 0.001 - 0.01 part by weight of a polymerization initiator
such as azobisisobutyronitrile to obtain a rod-shaped copolymer. ~fter
annealing the so obtained copolymer or 2~ hours at 80 - 90C., it is cut
into pieces having a suitable thickness, which pieces are polished and
bevel-machined to obtain the contact lens.
The contact lens obtained in this manner is of fhe hard type, but
it diffe~s from the conventional hard contact lens in that the eyes do not
become bloodshot and there is no burning feeling or fogging of the lens.
Thus, the contact lens made of the invention copolymer is characterized by
its possession of excellent properties making possible its use wi~h no
troubIe at all.
When the ~atio of methyl methacrylate/dextran ester is less than
- 18 -
~7~ 33
1.0, the mechanical properties of the resulting contact lens suffer while,
on the other hand, when this value is 10 or more, there is a tendency that
its wearing feel becomes poor. Hence, it is pre~erred that a ratio in the
range from 1 to 10 be used. Further, when the acetic acid content of the
dextran ester is small, the wet durability becomes poor, though its wett-
ability with respect to tears is satis~actory. On the other hand, when the
acetic acid content is too great, the wettability tends to become poor,
though the strength and stability are good. Further, since the acetic acid
content has an effect on the solubility of dextran ester in methyl methacry-
late, a mixture in which the content of acetic acid is 10 - 40%, and
especially 20 - 35%, is preferably used. Again, the contents of unsaturated
acid such as, for example, methacrylic acid and acrylic acid have a bearing
on the solubility of the ester in methyl methacrylate and the degree of
cross-linking of the copolymer and hence its mechanical strengths, etc.
Thus, when the contents of the unsaturated acids are considered from the
overall standpoint, their total content should preferably be in the range of
5-20%.
The mixed dextran ester o acetic acid and acrylic acid or acetic
acid and methacrylic acid can also be copolymerized in the same manner as
hereinbefore described and thereater processed into a contact lens.
Again, a copolymeric powder or granular material o~ methyl
methacrylate and a dextran ester obtained by the suspension polymerization
process, preferably a copolymer of the mixed dextran ester of acetic acid
.
and methacrylic acid, or acetic acid and acrylic acid, or acetic acid,
methacrylic acid and acrylic acid, with methyl methacrylate, can also be
made into a contact lens. The powder or granular material is placed in a
mold where it is pressed at a pressure of 50-400 Kg/cm2 while being hea~ed
at 170 - 250C. to form a product of sheet or rod form, following which this
is submitted to machining operations as cutting, grinding, polishing and
heveling to obtain the co~tact lens.
When a patient's eyes are fitted with contact lenses made in the
aforementioned manner but in which the degree o esterification of the
,
~L0756~33
starting saturated acid from which the ester was prepared was great, on rare
occasions complaints are heard of that feeling of a foreign body being
present In a case such as this, if the contact lenses are given a surface
treatment for a short period of time with an alcoholic alkaline solution
before or after the lenses are submitted to the beveling operation or both
before and after the operation, the lenses can be worn by the patient with-
out imparting that feeling of a foreign body being present. For example,
this feeling can be eliminated by treating the lenses for usually 15-60
; seconds with a mixture of water and alcohol such as meth~nol or ethanol
(preferably of an alcohol concentration of 25-75%)~ in which has been
dissolved an alkali such as caustic soda, sodium carbonate or sodium
bicarbonate to a concentration of preferably 0.1 - 1.0 N. After the
treatment, the lenses should be washed thoroughly with water, dilute boric
acid solution and water, in the order given and, if necessaryJ further washed
for a very short period o~ time ~ith isopropyl alcohol. -;
Next, when a dextran ester is copolymerized with a hydroxyalkyl
metha~crylate, e.g., 2-hydroxyethyl methacrylate (HEMA) or 2-hydroxypropyl
methacrylate, a so-called hydrogel having great hygroscopicity is formed.
As this hydrogel possesses a cross-lin~ed structure, it not only is
hydrophilic but also possesses superior mechanical properties, e.g.J tensile
strength and elasticity. Again, it can also be imparted transparency.
Hence, the foregoing hydrogel is suitable for making artificial organs,
especially soft contact lens. As methods of making a soft contact lens,
for example, that consisting of placing a dextran ester and HEMA as well as
a polymerization initiator such as benzoyl peroxide and, If necessary, a
suitahle amount of MMA in a rotating mold and carrying out the polymeriza-
tion reaction therein to obtain the product, or that cons~sting of polymeri-
zing a dextran ester and HE~ into the form of a rod and then cutting,
,
- polishing, boiling and swelling this copolymer can be employed.
j~ 30 Further, the~foregoing hydrogel cannot only be used as a carrier
of medicmes but also as a molecular sieve for separating substances o~
differing molecular weights.
- 20 -
. ,
: . , - . . : , . .
~L~756~3
The method of analyzing the dextran ester used in the present
invention will now b~ described.
One gram of the sample is placed in 20 ml of 75% H2SO4 and by
leaving it to stand for 2 hours is practically dissolved therein. Fifty ml
of water is then added, after which steam distillation of the solution is
carried out to obtain about 2 liters of a distillate. The following
operations are then carried out in accordance with the class of the ester.
(1) In the case of an ester of an unsaturated acid alone.
The dis~illate is submitted to redox $itration to obtain the amount
contained of the double bonds, after which the conten~ of the unsaturated
acid is calculated.
(2) In the case of a mixed ester of a saturated acid and one class of an
unsaturated acid.
The distillate is divided into two portions. One portion is then
submitted to neutralization titration to obtain the total amount of the acids
contained, while the other portion is submitted to redox titration to obtain
the amount contained of the double bonds, after which the contents of each
acid are calculated from these values.
(3) In the case of a mixed esteT of a saturated acid and two classes of
unsaturated acids.
The distillate is divided into three portions. One of the portions
is then submitted to neutralization titration to obtain the total amount o~
acids contained, while the second portion is submitted to redox titration to
obtain the amount contained of double bonds. On the other hand, the third
portion is concentrated under reduced pressure to about 300 ml, after which
30 microli~ers thereof is submit~ed to gas chromatography (column: 3mm in
diameter and 2.5 meters long, packed with a packing consisting of CELITE 545
coated with 15% SILICON DC 550 and 2% stearic acid; decomposition temperature: ;110C.; carrier gas: HE; detector: hydrogen flame ionization detector).
The ratios of the several components are then obtained from the resulting
chromatogram and a priorly prepared calibration curve. The c~ntents of each
acid are calculated from the foregoing three values.
- 21 -
, : . . ~
-
1~7~3
The following examples will serve to more fully illustrate the
present invention.
Example 1
A mixed solution consisting of 135 grams of acetic anhydride, 375
grams of me~hacrylic acid, 100 grams of acrylic acid, 20 grams of potassium
acetate, 1.6 grams of hydroquinone and 500 grams of dimethylformamide was
heated for 10 minutes at 115C. with stirring. After cooling the solution,
there was added thereto 24.4 grams of dextran treated in advance with a
potassium acetate solution [intrinsic viscosity [~]=0.17~ dl/g before
treatment (measured in water at 25C.)~ ~10 grams calculated as dextran)
fo~lowed by heating the mixture for 30 minutes at 115C. with stirring.
After cooling the resulting reaction solution, it was introduced into 3-fold
amount (volume) of water, after which the precipitated white product was
separated.
-- Next, this product was dissolved in acetone and, after filtering
it, if necessary, introduced into water to obtain a precipitate. After
` repetition of such a purification operation, the product was dried under
reduced pressure to obtain 17 grams of a white powdery product.
The so obtained product was soluble in acetone, chloroform,
dimethylformamide, dimethyl sulfoxide, dioxane, methyl methacrylate and
2-hydroxyethyl methacrylate; swellable in benzene and toluene; and insoluble
in water, methanol and formamide.
Ac0tic acid content=30.3%, methacrylic acid content=9~8% and
acrylic acid content-8.2%.
Specific rotation [~]20=+1~9 (0.3g ~50/50
formamidedimethylformamide solvent mixture 10 ml; the specific rotation of
the~starting d0xtran measured under identical conditions was [~12=+2000)
Five grams of the so obtained acetic acid-methacrylic acid-acrylic
acid mixed ester of dextran was dissolved in 15 grams of methyl methacrylate
in an Erlenmeyer flask. After filtration of the solution with a glass filter~
0.075 gram of azobisisobutyronitrile was added and dissolved therein. The
solution was then transferred to a glass tube having an inside cliameter of
.
- 22 -
. . . - .
.
56~3
14 mm and, a~ter the tube was deaired, it was sealed and heated for 24 hours
in a water bath of 40C. and thereafter for 4 hours in an air h~th of 100C.
After cooling, a transparent, hard rodlike product was wlthdrawn from the
glass tube. This product was then annealed for 2~ hours in an air bath of
80C. The weight o~ this product was 19.5 grams, and it was insoluble in
water, methanol, acetone, chloroformJ dimethylformamide, dimethyl sulfoxide,
dioxane, benzene and toluene. The Vicat softening point of this product was
170C., and its Rockwell hardness (M scale) was 101. The Vicat softening
point was determined in accordance with the ASTM ~ethod D1525, while the
Rockwell hardness was measured in accordance with the ASTM method D785.
Example 2
A mixed solution of 479 grams o~ methacrylic acid, 135 grams of
acetic anhydride, 20 grams of potassium acetate, 500 grams of dimethylforma-
mide and 1.0 gram of hydroquinone was heated ~or 10 minutes at 115C. with
stirring. Next, 2~.~ grams o~ the potassium acetate-treated dextran
~corresponding to lO grams of dextran) as used in Example 1 was added to the
foregoing solution, following which the solution was heated for 3~ minutes
at 115-116C. with stirring. After cooling, the solution was treated as in
Example 1 to obtain 14 grams of a white powdery produc~. The content of
acetic acid was 32.2%, while that of methacrylic acid was 19.0%. This
product was insoluble, in water, methanol and formamide but soluble in
acetone, dioxane, chloroform and dimethyl~ormamide.
Five grams of the acetic acid-methacrylic acid mixed ester of
dextran obtained in this manner and 0.07 gram of azobisisobutyronitrile were
dissolved in 30 grams of methyl methacrylate, after which the solution was
bulk polymerized in a glass tube as in Example 1 to obtain 3~ grams of a
transparent rodlike product. This product was insoluble in water, methanol,
acetoneJ dioxane, chloroform, formamide, dimethyl~ormamide, benzene and
toluene. The Rockwell hardness (M scale~ o~ the product was 1O4J while its
Vicat softening point was 175C.
Exame~
The esterification reaction was carried out under exactly iden~ical
- 23 -
56~33
conditions as in Example 2 but using 400 grams of acrylic acid instead of
methacrylic acid to obtain 12 grams of a white powdery product. The acetic
acid content was 28.1%, while the acrylic acid content was 15.1%.
This product was insoluble in water, methanol and formamide but
soluble in acetone, dioxane, chloroform and dimethylformamide.
Five grams of the so obtained acetic acid-acrylic acid mixed ester
of dextran was used and by opera*ing as in Example 1 was copolymerized with
20 grams of methyl methacrylate to obtain 24 grams o a transpar~nt rodlike
product.
This product was insoluble in water, methanol, acetone, dioxane,
chloroforml formamide, dimethylformamide, benzene and toluene. The product's
Rockwell hardness ~M scale) was 102, and its Vicat softening point was 172~C.
Example 4
Five grams of the acetic acid-methacrylic acid-acrylic acid mixed
ester of dextran obtained in Example 1 was dissolved in 50 grams of
2-hydroxyethyl methacrylate. This was followed by the addition and dissolu-
tion therein of 0.22 gram of azo~isisobutyronitrile, after which the solution
was deaired, placed in an optional mold, sealed and polymerized by heating
for 24 hours at 40C., followed by 4 hours at 60C. and thereafter 2 hours
at 100C. After cooling, the product was removed from the mold. The so
obtained product was transparent and hydrophilic. Its Rockwell hardness
was 98.8, and its Vicat softening point was 111C. Further, its water
absorption was 17.9% ~ASTM ~ 570).
Example 5
A mixed solution of 400 grams of acrylic acid, 135 grams of
acetic anhydride, 100 grams of potassium acetat~, 500 grams o~ toluene and
1.0 gram of hydroquinone was refluxed for 10 minutes. Next, 24.4 grams of
the potassium acetate-treated dextràn ~corresponding to 10 grams of dextran~
used in Example 1 was added, and the reaction was carried out for 30 minutes
at 115~. with stirring. After cooling, the reaction solution was introduced
into water. Next, while adding lu~ps of ice, the pH of the solution was
: adjusted to 4.0 with a caustic soda solution, and the product was separated.
.
- 2~ -
. . .
.:
~7561~3
The product was washed with a large amount of water, filtered off and dried
under reduced pressure to obtain 11 grams of a whita powdery product~ The
content of acetic acid of this product was 21.2%, while that of acrylic acid
was 10.6%. This procluct was insoluble in water, methanol, acetone and
formamide but soluble in dioxane, chloroform and dimethylformamide.
Five grams of the so obtained acetic acid-acrylic acid mixed ester
of dextran was dissolved in 500 ml of dioxane in a 4-necked flask, following
which 50 grams of methyl methacrylate was added dropwise while introducing
nitrogen. 0.55 grams of benzoyl peroxide was then added, and the inside
temperature was raised to 65C., at which temperature the reaction was
carried out for 10 hours. After cooling, the reaction solution was introduced
into methanol, and ~he precipitate was separated by filtration, washed in
methanol and dried under reduced pressure. The dried product was then
extracted by the Soxhlet method using acetone, after which the residue was
dried to obtain 45 grams of a white product. This product wàs insoluble in
water, methanol, formamide and dimethylformamide.
Fxample 6
, Five grams of the acetic acid-methacrylic acid-acrylic acid mixed
ester of dextran obtained in Example 1 was dissolved in 50 grams of methyl
methacrylate in a 3-necked flask, after which 0.11 gram of azobisisobutyroni-
trile was added and dissolved therein. When this solution was heated for
2 hours at 65C. with stirring, a viscous solution was obtained. lhis solu-
tion was immediately cooled and introduced into a mold prepared by bringing
together two sheets of glass. After closing the mold, it was heated in an
air bath for 10 hours at ~5C., then 2 hours at ~0C., and thereafter 2 hours
at 100C. After cooling the mold~ the product was taken out. Thus was
obtained a transparent product of sheet form. This product had a Rockwell
hardness ~ scale) of 100 and a Vicat softening point of 170C
Example 7
The rodlike copolymer obtained in Example 1 was cut with a lathe
rotating at 2000 rpm. A prescribed curvature was then established for the
cut pieces by concavo-convex machining the pieces at the same rpm. Next,
- 25 -
.. . . . .
1~1568~
these pieces were fitted into pit dishes of a lens polisher a~d polished
under the conditions of an under part rotation of 200 rpm and upper part rota-
tion of 15 rpm. Then the edge of the lenses were beveled with a bevelling
machine to obtain the contact lenses.
The following dyeing test was conducted for examining the wetting
property of the surface of the contact lens made in the manner described
above. ~he contact lens was treated in an aqueous solution con~aining 3% of
SUMINAL MILLING RED RS, 0.02% of glacial acetic acid and 0.1% of ammonium
acetate. As control, a commercially available hard contact lens was submitted
to the same treatment. When the dyeabilities of the ~wo were compared, the
contact lens of the present invention was dyed to a red color, whereas the
control lens was not dyed at all, thus demonstrating that in the case of the
contact lens of the present invention there is an increase in the hydrophili-
city of the lens surface and an împrovement in its wetting property.
Further, when for testing the durability of the invention contact
lens it was immersed in an isotonic salt solution and, after holding it
therein for 120 days at 25C., taken out and its base curve was measured
with a contact gauge manufactured by Leitz Company, while its power was
measured with a lens meter manufactured by Topcon Company, Japan, there was
no change in either the base curve or the power. Thus, the durability was
found to be satisfactory.
Next, a clinical test was conducted using the invention contact
lens. A patient having the following vision and unable to use the commerci-
ally available hard contact lens due to eye pains when fitted therewith was
fitted with the following contact lens obtained in this Example.
Vision.
Left eye vision......... 0.04 ~l.OxS-6.25)
Right eye vision~....... 0.04 ~l.OxS-6.25)
Contact lenses used.
Base cur~e PowerSizeCorrected vision
Left eye 730 -4.508.8 1.0
Right eye 730 -4.758.8 1.0
.
- 2~ -
. .
., . " . , . : . . ~ . .
~75~83
When observations were carried out over a period of 180 days, it
was found that even though the lenses were worn 12 hours per day there were
no complaints of unpleasantness in either eye, normal vision was restored and
there was no change at all in the base curve as well as power of the contact
lenses.
Example 8
Contact lenses were obtained by operating as in Example 7~ using
the rodlike copolymer obtained in Example 2.
A clinical test was conducted using the so obtained contact lenses.
10 A patient having the following vision and unable to use the commercially
availa~le hard contact lenses due to the eyes becoming bloodshot when fitted
therewith was fitted with the following contact lenses obtained in this
Example.
Vision.
Left eye vision........ 0.02 ~1.0 x S - ~.50)
Right eye vision....... 0.02 (1.0 x S - 4.00)
Contact lenses used.
Base curve Power Size Corrected vision
Left eye 820 -3.0 8.8 1.0
Right eye 800 -4.0 8.8 1.0
While the lens could be worn with no trouble in the case of the
left eye, the patient complained of some unpleasantness in the case of the
right eye.
So, the contact lens fitted to the right eye was removed and, after
immersion for 20 seconds in a solution obtained by dissolving caustic soda
in 30% aqueous methanol to a concentration of 0.25 N, was thoroughly washed
in water~ 0.5 N aqueous boric acid solution and water, in the order given,
and flnally in isopropylalcohol.
When the so treated and washed lens was again worn in the righ~
eye, there was no complaint at all of unpleasarltness.
~ urther, even after the lenses were worn for 180 days, there was no
abnormality as to the vision and the wearing feel, and there was no change
in the base curve and power of the contact lenses.
- 27 -
, - : ' ' '
,
