Pilkington Brothers P.l.c.

Smith & Nephew, Inc., Research

Reginald Dunning

Richard J Parry

William D Potter

Andrew C Barclay

A water hardenable cement composition comprising a fluorine-free calcium alumino silicate glass in particulate form in which the individual particulates have a particle size of less than 100 microns consisting essentially of 25-35% silica, 27-35% calcium oxide, 25-40% alumina, up to 4% of an alkali metal oxide, up to 5% of titania, the total amount of alkali metal oxide and titania being 0.5-9%, wherein the ratio of calcium oxide to silica is 0.7:1 to 1:0-7, together with a polycarboxylic acid.

Cement compositions

The invention relates to calciumaluminosilicate glasses. The glasses contain, in weight percent, 25 to 35% silica, 27 to 35% calcium oxide, 25 to 40% alumina, 0 to 4% of alkali metal oxide selected from lithium oxide, sodium oxide and potassium oxide, and 0 to 5% of titanium oxide and a total content of lithium, sodium, potassium and titanium oxides of 0.5 to 9%. The glasses, in finely divided form, react with aqueous polycarboxylic acids and set to a solid mass; cements made from the glass and polycarboxylic acids are useful in splinting compositions.

Fluorine-free calcium-aluminosilicate glasses

A novel calcium fluoroaluminosilicate glass consisting essentially of from 25 to 35% by weight of silicon calculated as silica, from 30 to 40% by weight of aluminum calculated as alumina, from 20 to 35% by weight calcium, calculated as calcium oxide, and up to 9% by weight fluorine (preferably 4-7%) can be associated with a poly(carboxylic acid e.g. as an intimate mixture of glass and acid to constitute a composition curable on contact with water and useful, for example, as a loading on a splinting bandage. Such a bandage preferably has a ratio of set time to gel time from 4:1 to 8:1 with a minimum gel time.

Glass compositions for use in curable compositions

A novel calcium fluoroaluminosilicate glass consisting essentially of from 25 to 35% by weight of silicon calculated as silica, from 30 to 40% by weight of aluminum calculated as alumina, from 20 to 35% by weight calcium, calculated as calcium oxide, and up to 9% by weight fluorine (preferably 4-7%) can be associated with a poly(carboxylic acid) e.g. as an intimate mixture of glass and acid to constitute a composition curable on contact with water and useful, for example, as a loading on a splinting bandage. Such a bandage preferably has a ratio of set time to gel time from 4:1 to 8:1 with a minimum gel time of 60 seconds.

Curable composition comprising a calcium fluoro-alumino silicate glass

Curable compositions

Ophthalmic glass compositions suitable for toughening by the known ion-exchange process have a composition in weight percentages of: SiO.sub.2    58     to  67% Al.sub.2 O.sub.3 4.5     to  8.0% Na.sub.2 O    8.5     to  17% K.sub.2 O    2      to  11% ZnO       0      to  10% ZrO.sub.2    0      to  6.5% TiO.sub.2    0      to  5.0% As.sub.2 O.sub.3 0      to  1% Sb.sub.2 O.sub.3 0      to  1% B.sub.2 O.sub.3 0      to  6% The total of the foregoing constituents amounting to at least 95% of the composition and the balance, if any, being composed of compatible constituents; the composition including an effective amount of either one or both of ZnO and ZrO.sub.2, to promote ion penetration in an ion-exchange toughening process, either one or both of ZrO.sub.2 and TiO.sub.2 being present; the total of Na.sub.2 O + K.sub.2 O being not more than 22%; B.sub.2 O.sub.3 being present when the total of Al.sub.2 O.sub.3 + ZrO.sub.2 exceeds 10%; and the total of ZrO.sub.2 + TiO.sub.2, when TiO.sub.2 is present, being not more than 5.5%. Refractive index n.sub.d is close to the standard value of 1.523 and good penetration of the ion exchange is achieved in toughening, while the expansion coefficient makes the glass compatible with a standard flint glass in fused bi-focal lenses.

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Parbold, near Wigan, United Kingdom

Reginald Dunning