Process for the preparation of a diol

Details Process for the preparation of a diol Process for the preparation of a diol

2001-10-15

2003-08-26

Barts, Samuel (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C560S205000

Reexamination Certificate

active

06610895

ABSTRACT:

The present invention relates to a process for the preparation of a diol. The diol may be used subsequently used as a monomer for the preparation of a polymeric device or material such as a hemocompatible coating, medical device, water soluble polymer material, paint, water borne coating or an ocular device (such as a contact lens).
Polymers made from polymerisable monomers have wide spread applications. For example, polymers are used as additives for coating applications, such as paints and adhesives. Polymers are also used to prepare lenses, such as contact lenses.
Polymers are prepared by polymerising one or more types of polymerisable monomers, such as by emulsion polymerisation, solution polymerisation, suspension polymerisation or bulk polymerisation. The monomer(s) may be polymerised in the presence of optional ingredients such as any one of emulsifiers, stabilisers, surface active agents, initiators (such as photoinitiators), inhibitors, dispersants, oxidising agents, reducing agents, viscosity modifiers, catalysts, binders, activators, accelerators, tackifiers, plasticizers, saponification agents, chain transfer agents, surfactants, fillers, dyes, metal salts, and solvents.
There are numerous references on polymerisation of polymerisable monomers. For example, some teachings may be found in “Emulsion Polymerization: Theory and Practice” by D. C. Blackley (published by Wiley in 1975) and “Emulsion Polymerization” by F. A. Bovey et al. (published by lnterscience Publishers in 1965). For example, a polymer can be prepared from monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, styrene, butadiene, ethylene, vinyl acetate, vinyl esters, C
9
, C
10
and C
11
tertiary monocarboxylic acids, vinyl chloride, vinyl pyridine, vinyl pyrrolidine, vinylidene chloride, acrylonitrile, chloroprene, acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid.
Examples of further teachings on polymerisation of polymerisable monomers may be found in “Vinyl and Related Polymers” by C. E. Schildknecht (New York: John Wiley & Sons 1952) and “Monomeric Acrylic Esters” by E. H. Riddle (New York: Reinhold Publishing Corp. 1954), and by A. G. Alexander (J. Oil Colour Chemists' Association [1962] 45 12) and G. G. Greth and J. E. Wilson (J. Appl Polymer Sci [1961] 5 135).
More recent teachings regarding polynerisation methods may be found in EP-A-0622378, EP-A-0634428, EP-A-0623632, EP-A-0635522, EP-A-0633273, EP-A-0632157, EP-A-0630908, EP-A-0630641, EP-A-0628614, EP-A-0628610, EP-A-0622449, EP-A-0626430 and EP-A-0625529.
As mentioned above, one particular application of polymers is in the preparation of lenses, especially contact lenses or intraocular lenses. Examples of teachings for the preparation of contact lenses may be found in EP-A-0359539, which discloses a method of forming a soft contact lens. Other documents that describe the preparation of contact lenses include WO-A-9502617 which discloses a contact lens made from a vinyl polymer bearing phosphonium groups, JP-A-06313009 which discloses a contact lens made from a polymer having a terminal phosphoryl-choline group, WO-A-9429756 which discloses a gas permeable ocular lens made from a block copolymer and a second polymer component, WO-A-9409042 which discloses a contact lens comprising polymer and a UV absorbing constituent, and WO-A-9211407 which discloses a tinted contact lens comprising a polymer and a dye wherein the lens is prepared by incorporating a dye into a hydrophilic polymer while the polymer is being formed. Further documents describing preparing contact lenses and the like from polymerisable monomers include EP-A-0574352, EP-A-0439394, EP-A-0378511 and EP-A-0424520.
Whilst polymers can be fairly easily prepared from polymerisable monomers there can be a problem in reliably and cheaply obtaining suitable monomers in a satisfactory pure form. In this regard, many desired polymerisable monomers are supplied with impurities. These impurities can be detrimental to the final product and so they have to be eliminated before the polymerisation reaction to form the desired polymer.
Impurities which is particularly problematic are compounds which act as cross-linkers during the polymerisation of the monomer. The presence of cross-linkers prevents and/or inhibits the formation of straight chain polymers. Moreover, the presence of cross-linkers in a monomer may prevent the solubilisation of polymers formed therefrom.
Another example of such a monomer is glyceryl methacrylate (GMA) which is a preferred monomer for preparing contact lenses. Examples of documents mentioning the use of such a monomer include U.S. Pat. No. 5,236,969, JP-A-04335007, GB-A-2180243 and EP-A-0100381. There are two major problems with GMA. First, the impurities often vary from batch to batch and so make it difficult to have a standard purification protocol. Second, GMA is a very expensive monomer.
There have been attempts to prepare GMA from other monomers, such as isopropylideneglyceryl methacrylate (IPGMA). One such process for preparing GMA is disclosed in U.S. Pat. No. 4,056,496 wherein the process includes reacting IPGMA with sulphuric acid and hydroquinone for a period of 16 hours.
Another process for preparing GMA, also mentioned in U.S. No. 4,056,496, includes the hydrolysis of glycidyl methacrylate (GYMA) by treating GYMA with concentrated sulphuric acid for 6 days (M. F. Refojo [1965] Journal of Polymer Science 9 pp 3161-3170). This process is particularly disadvantage because the addition of mineral acid to GMA may result in the formation of glyceryl dimethacrylate which is a cross-linker, and various other dimethacrylates.
The distillation of GMA to prepare purified GMA is also practised in the art. Distillation is however both difficult and costly. GMA is high boiling and therefore costs of distillation are high. Distillation typically gives losses of 15-20% of the product to be purified. Moreover, GMA may polymerise during distillation and valuable monomer lost. Yet further, the equipment which may be required to perform the distillation e.g. falling film evaporator, is expensive.
Clearly these prior art methods are very labour intensive and include the use of hazardous chemicals, including toxic chemicals and flammable solvents, and hazardous process steps.
Further prior art methods for preparing GMA polymers are disclosed in U.S. Pat. No. 4,338,419, FR 8207595, WO 93/0841 and Ezrielev et al, Vysokomol. Soedin, Ser. B, 20(10), 777-9, Hild, Makromol. Chem, 177, 1947-1972 (1976) and Beinert et al, Die Makromolekulare Chemie, 175, 2069-2077 (1974).
U.S. Pat. No. 5,532,289 discloses a process for forming a soft contact lens. According to the claims of this patent the lens is formed from a copolymer consisting essentially of 2,3-dihydroxypropyl methacrylate (i.e. glyceryl methacrylate [GMA]) and 2-hydroxyethyl methacrylate. Hydroxyethyl methacrylate is sometimes referred to as HEMA. The process of U.S. Pat. No. 5,532,289 requires a pre-distillation step wherein GMA is distilled. Hence, the process of U.S. Pat. No. 5,532,289 is laborious and costly.
WO 98/07055 discloses a process of preparing an ocular device (such as a contact lens) consisting essentially of GMA and HEMA, the process comprising the following steps: a) copolymerising a second monomer and a first monomer having attached to it a modifier group, thereby to form a first polymer having associated with it the modifier group; and b) modifying all or some the modifier group associated with the first polymer to form a second polymer different from the first polymer thereby to form the ocular device consisting essentially of GMA and HEMA.
The present invention seeks to overcome the problems associated with the known processes for preparing polymers.
According to a first aspect of the present invention there is provided a process for the preparation of a polymerisable monomer of formula I
comprising the step of contacti

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