Stable initiator system

Details Stable initiator system Stable initiator system

2000-03-22

2002-07-02

Seidleck, James J. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Compositions to be polymerized by wave energy wherein said...

C522S064000, C522S172000, C522S099000, C524S858000, C524S837000, C524S866000, C524S916000

Reexamination Certificate

active

06414049

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to the use of photoiniators. More particularly, it relates to the stabilization of photoinitiators useful in processes for making ophthalmic lenses.
Ophthalmic lenses such as contact lenses are often made in processes that employ photoinitiated polymerization reactions. UV and visible radiation are most frequently used to initiate cure in these reactions. It is often desirable to prepare a mixture of materials together with an initiator or initiator system (where initiation involves more than one component) and other additives that will ultimately form the lens upon completion of the reactions. These types of mixtures are referred to as the “monomer mix” in this context. Stability of the initiator can be a crucial factor in the working time and shelf life of the monomer mix. Increasing the working time of the monomer mix is desirable since it reduces the need for preparation of starting materials and the possibility of introducing lot to lot and intra-lot variations in lens production. Acylphosphines are an interesting and useful class of initiators for free radical polymerations of the type frequently used to made ophthalmic lenses. Reaction mechanisms for many of these materials are described in Reaction Mechanism of Monoacyl- and Bisacyiphoine Oxide Photoinitiators Studied by
31
P,
13
C-, and
1
H-CIDNP and ESR, Ursul Kolczak, Gunther Rise, Kurt Dietliker, and Jacob Wirz, 118 J. Am. Chem. Soc., 6477 (1996). Bisacylphosphines and their use are further described in U.S. Pat. No. 5,534,559 and JP-A-8-259642 incorporated herein by reference.
Unfortunately, this class of compounds tends to be unstable in a variety of environments lessening its potential as an active initiator. EP 849,296 proposes a method of stabilizing bisacylphosphine initiators used in the production of urethane (meth)acrylate polymers used for coatings. The method involves combining the monomer components together with the initiator in the presence of a tertiary amine and in the absence of a tin component. Japanese patents JP-A-4-6125; JP-A-296315; JP-A8-127630 propose similar methods of stabilizing monoacylphospine photoinitiators in the presence of a tin compound used as a polymerization catalyst.
Unfortunately, these solutions are not desirable when applied to monomer mixes used to make ophthalmic lenses because of the potentially deleterious effect they may have on various components of the monomer mix. This is particularly true where the monomer mix is used to make silicone hydrogel lenses.
A new method for stabilizing acylphosphine initiators is desirable.
SUMMARY OF THE INVENTION
The invention is a stable monomer mix for making ophthalmic lenses. The stable monomer mix is made by admixing a monomer mixture, an initiator, and an acid.
In another aspect of the invention a silicone hydrogel monomer formulation is made by admixing a silicone hydrogel forming mixture, an initiator, and an acid.
In yet another aspect of the invention, a method of stabilizing an initiator system comprises lowering the pH of the initiator system.
In yet another aspect of the invention, a process for stabilizing a silicone hydrogel monomer formulation in an admixture of a reactive silicone macromer and a photoiniator comprises admixing an acid with the admixture of macromer and photoinitiator.
DETAILED DESCRIPTION OF THE INVENTION
The initiators of this invention are those having the following structure:
wherein, R
1
, R
2
, and R
3
are each independently H or a C
1-12
substituted or unsubstituted alkyl cycloalkyl, or aromatic moiety provided that at least one of R
1
, R
2
and R
3
has the following structure:
and is attached to the P at the acyl carbon, and wherein, R
4
-R
8
are independently, H or a C
1-3
substituted or unsubstituted alkyl or alkoxy moiety.
In each case, where an R
1
-R
8
group is substituted, the substituent can comprise a hydroxy or C
1-4
alkyl alkoxy, alkenyl, or alkynyl group. Substitution with hetero atoms such as nitrogen, sulfur, and halo atoms is possible but is not favored.
It is preferred that R
1
and R
2
are both Structure II moieties with R
4
and R
8
substituents. It is most preferred that R
4
and R
8
are methoxy groups. It is further preferred in this embodiment that R
3
is a C
1-10
alkyl alkoxy, or alkenyl group substituted with C
1-2
alkyl groups; most preferably a substituted pentyl group.
In the most preferred embodiment, R
1
and R
2
are both Structure II moieties with R
4
and R
8
being methoxy groups; R
1
is a trimethyl pentyl group. Thus, the most preferred embodiment has the following structure:
Theses initiators can be used alone or in combination with other initiators such as benzoin methyl ether, 1-hydroxycyclohexyl phenyl ketone, Irgacure 1850 brand photoinitiator, 1-hydroxy cyclohexyl phenyl ketone (commercially available as “Irgacure 184”); 2-benzyl-2-n-dimethylamino-1-(4-morpholinophenyl)-i-butanone (commercially available as “Irgacure 369”); 1-hydroxycyclohexyl phenyl ketone (50% by weight) plus benzophenone(commercially available as “Irgacure 500”); 4-(2-hydroxyethoxy) phenyl-(2-hydroxy propyl)ketone (commercially available as “Irgacure 2959”); 2,4,6-Trimethyl benzoyl diphenyl phosphineoxide (TPO) (50% by weight) plus 2-hydroxy-2-methyl-1-phenyl-propan-1-one (HMPP) (50% by weight) (commercially available as “Darocur 4265”); 2,2-dimethoxy-2-phenylacetophenone (BDK) (commercially available as “Irgacure 651”); bis (n1-2,4-cyclopentadien-1-yl), bis (2,6-difluoro-3-(IH-pyrrol-1-yl)phenyl) Titanium (CGI-784); 2-methyl-1-(4-(methylthio)phenyl)-2-morpholino propan-1-one (MAP) (commercially available as “Irgacure 907”); 2-hydroxy-2-methyl-1-phenyl-propan-1-one (HMPP) (commercially available as “Darocur 1173”); or mixtures thereof. Mixtures that include a UV and visible light initiator system are preferred as they permit more flexible use of UV blockers in the monomer mix.
The stabilizers useful in this invention are acids. These are preferably weak organic acids but may include strong inorganic acids as well as Lewis acids. Additionally, precursors capable of generating acids in the reaction mixture can also be used. The most preferred acids are acetic acid, formic acid, propionic acid, and acrylic acid.
The inorganic acids include, for example, hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, hydroiodic acid, hydrofluoric acid, sulfurous acid, nitric acid, nitrous acid, phosphorous acid, perchloric acid, chloric acid, chlorous acid, iodic acid, bromic acid, arsenic acid, carbonic acid, selenium hydride, tellurium hydride, phosphonic acid, hypophosphoric acid, diphosphonic acid, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid, selenic acid, selenious acid, telluric acid, tellurous acid, arsenious acid, antimonic acid, antimonous acid, borofluoric acid, etc.
The organic acids include, for example, the sulfonic acids such as hydroxymethanesulfonic acid, trifluoromethanesulfonic acid, beta-bromoethanesulfonic acid, allylsulfonic acid, 2-methyl-2-[(1-oxo-2-propenyl)amino]-1-propanesulfonic acid, D-10-camphorsulfonic acid, benzenesulfonic acid, m-nitrobenzenesulfonic acid, m-benzenedisulfonic acid, methanesulfonic acid, ethanesulfonic acid, 2-hydroxyethanesulfonic acid, 2-(cyclohexenylamino)methanesulfonic acid, (3-cyclohexenylamino)methanesulfonic acid, p-ethylbenzenesulfonic acid, alpha-naphthalenesulfonic acid, beta-naphthalenesulfonic acid, p-toluenesulfonic acid, p-chloromethylbenzenesulfonic acid, p-phenolsulfonic acid, 2-pyridylhydroxymethanesulfonic acid, 2,6-naphthalenedisulfonic acid, etc.; the organic sulfinic acids such as benzenesulfinic acid, p-toluenesuifinic acid, etc.; the organic phosphoric acids such as phenylphosphonous acid, butyphosphonous acid, methylphosphonous acid, dibenzenephosphinic acid, dibutylphosphinic acid, benzenephosphonic acid, methylphosphonic acid, phenylphosphinic acid, methylphosphinic acid, dibenzenethiophosphinic acid, dibutylthiophosphinic acid, benzenethiophosphonic acid, methylthiophosphonic acid, phenylthiophosphinic acid, methy

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