CONTAINER OF GLASS AND METHOD FOR ITS MANUFACTURE
A container of glass and a method for chemically prestressing such a container of glass are provided. The container of glass includes a hollow body with an internal volume, a wall with an inside surface, which borders the internal volume of the hollow body, and an outside surface opposite the inside surface. The wall has, at least in a partial region, a zone with compressive stress formed bordering the outside surface, as a result of which the outside surface is compression-prestressed at least in a partial region. The inside surface of the wall opposite this partial region is free from compressive stresses and is under tensile stress.
1 . A container of glass, comprising:
a hollow body having has an internal volume and a wall, the wall having an inside surface that borders the internal volume and an outside surface opposite the inside surface; and
a zone of compressive stress (CS) in the wall at the outside surface so that the outside surface is compression-prestressed at least in a partial region, wherein the wall at the inside surface opposite the partial region is free from compressive stresses.
2 . The container of claim 1 , wherein the wall has a middle between the outside surface and the inside surface, and wherein the middle has a tensile stress (CT) that is greater than or equal to 0 MPa and less than or equal to 20 MPa.
3 . The container of claim 2 , wherein the wall at the inside surface opposite the partial region is under tensile stress (IST).
4 . The container of claim 2 , wherein the tensile stress in the middle is within a range of +/−10% of the tensile stress at the inside surface.
5 . The container of claim 1 , wherein the wall further comprises a feature selected from a group consisting of an opening, a rolled edging, a neck, a shoulder, a heel, a floor, and any combinations thereof.
6 . The container of claim 5 , the zone of compressive stress is formed adjacent to the feature.
7 . The container of claim 1 , wherein the hollow body is a body selected from a group consisting of a bottle, an ampoule, a syringe, and a cartridge.
8 . The container of claim 1 , wherein the inside surface has a tensile stress (IST) that is greater than or equal to 0 MPa and less than or equal to 30 MPa.
9 . The container of claim 8 , wherein the zone of compressive stress (CS) in the wall at the outside surface and the tensile stress (IST) at the inside surface satisfy:
0.3*(CS×DOL)/( t −DOL)<IST<0.7*(CS×DOL)/( t −DOL),
wherein DOL denotes a depth of the zone of compressive stress, t denotes a thickness of the wall, CS denotes compressive stress on the outside surface, and IST the tensile stress (IST) at the inside surface.
10 . The container of claim 1 , wherein the zone of compressive stress has a depth that is not more than 15% of a thickness of the wall.
11 . The container of claim 1 , wherein the zone of compressive stress has an alkali content that monotonously decreasing from a region remote by 0.5 μm from the outside surface up to a region remote by 0.5 μm from the inside surface.
12 . The container of claim 1 , wherein the wall at the inside surface is free from an additional concentration of alkali species introduced by the zone of compressive stress up to a depth of at least 100 μm from the inside surface.
13 . The container of claim 12 , wherein the depth is up to at least 200 μm.
14 . The container of claim 1 , wherein the wall at the inside surface has a region at least opposite the partial region that has an average content of K 2 O+Na 2 O up to a depth of 500 μm that is not more than 13% by weight.
15 . The container of claim 1 , wherein the zone of compressive stress (CS) a thermal zone of compressive stress or a chemical zone of compressive stress.
16 . The container of claim 1 , wherein the container comprises a borosilicate glass or an alumino-silicate glass.
17 . A container of glass, comprising:
a hollow body made of a borosilicate glass or an alumino-silicate glass, the hollow body being a shape selected from a group consisting of a bottle, an ampoule, a syringe, and a cartridge, the hollow body having an internal volume, an inside surface that borders the internal volume, and an outside surface opposite the inside surface; and
a zone of compressive stress (CS) formed from a concentration of alkali species in the outside surface,
wherein the inside surface is free from compressive stresses and is free from the concentration of alkali species up to a depth of at least 100 μm from the inside surface.
18 . The container of claim 17 , wherein the wall has a middle between the outside surface and the inside surface, and wherein the middle has a tensile stress (CT).
19 . The container of claim 17 , wherein the inside surface opposite the zone of compressive stress is under tensile stress (IST).
20 . The container of claim 17 , wherein the hollow body further comprises a feature selected from a group consisting of an opening, a rolled edging, a neck, a shoulder, a heel, a floor, and any combinations thereof, the zone of compressive stress being formed only up to the feature.
21 . A method for chemically prestressing a container of glass, comprising:
immersing only an outside surface of a glass hollow body in a saline bath comprising potassium nitrate (KNO 3 ) at a temperature of at least 400° C. and below a glass-transition temperature of the glass hollow body for a duration of 1 to 24 hours so that a compressive stress is generated only on the outside surface.
22 . The method of claim 21 , further comprising sealing an opening of the hollow glass body prior to the immersing step.