WO2004085322A1 - A method of manufacturing silica glass parts for lamp assemblies - Google Patents

A method of manufacturing silica glass parts for lamp assemblies Download PDF

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Publication number
WO2004085322A1
WO2004085322A1 PCT/IB2004/050286 IB2004050286W WO2004085322A1 WO 2004085322 A1 WO2004085322 A1 WO 2004085322A1 IB 2004050286 W IB2004050286 W IB 2004050286W WO 2004085322 A1 WO2004085322 A1 WO 2004085322A1
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WO
WIPO (PCT)
Prior art keywords
product
binder substance
silica glass
injection molding
silica powder
Prior art date
Application number
PCT/IB2004/050286
Other languages
French (fr)
Inventor
Gerrit J. W. R. Dorman
Geert G. C. Weijers
Sebastianus N. G. Cuppen
Original Assignee
Koninklijke Philips Electronics N.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2004085322A1 publication Critical patent/WO2004085322A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B19/00—Other methods of shaping glass
    • C03B19/06—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction

Definitions

  • the invention relates to a method of manufacturing silica glass parts for lamp assemblies, i.e. parts having silica glass as a main component of its material. Such parts are, for example, the reflector of the lamp and the transparent envelope of the lamp.
  • Parts for lamp assemblies must often fulfil certain special requirements, so that they have to be produced from special materials to comply with such requirements.
  • a special material is silica glass, which has an extremely low coefficient of expansion, can resist a high temperature, and can be transparent.
  • These properties, separately or in combinations, are required for certain parts for lamp assemblies, for example parts of incandescent halogen lamps and high-pressure discharge lamps.
  • the low coefficient of expansion allows large local temperature differences in the material.
  • the transparent envelope (bulb) of the lamp is produced from silica glass.
  • Such an envelope is produced by deformation of silica glass material when heated to a high temperature.
  • silica glass material is available on the market in the shape of a tube.
  • the silica glass tube is heated up to a temperature between 1600 °C and 1800 °C, and then the material is deformed in a fast operation by a special deforming apparatus whereby, for example, a pinch can be produced which closes the tube.
  • a pinch can be produced which closes the tube.
  • the object of the invention is to provide a method of manufacturing silica glass parts for lamp assemblies wherein the part can have a relatively complex shape, which method can be utilized in mass manufacture.
  • the method of manufacturing silica glass parts for lamp assemblies comprises a step of mixing crystalline or amorphous silicon dioxide powder, hereinafter referred to as silica powder, with a binder substance, a step of supplying the mixture of silica powder and binder substance to an injection molding apparatus so as to produce a shaped product by injection molding, a step of removing the binder substance from said product, and a step of sintering the product at a high temperature.
  • the production is thus divided into two stages.
  • the product is given the required shape, which may be any shape that can be obtained in an injection molding operation, and in the second stage the product is given the properties of silica glass.
  • silica powder is mixed with a binder substance so as to obtain a mixture which is suited to undergoing an injection molding operation.
  • a binder substance is polyethylene mixed with polyethylene glycol. It was found that mixing of equal volumes of such a binder substance and silica powder yields a material that can be injection-molded into a product of relatively complex shape.
  • the binder substance is removed from the material of the shaped product. Depending on the kind of binder substance, this removal may take place by heating of the product and/or by someother operation or process.
  • the material of the shaped product is sintered through heating of the material, so that the final silica glass product is obtained.
  • the binder substance is at least partly soluble in a liquid, preferably in water.
  • the polyethylene glycol can be removed at least partly by immersing the shaped product into water, in which the polyethylene glycol is dissolved.
  • the remainder of the binder substance, including the polyethylene may be removed by heating of the product. Subsequently the material of the shaped product can be sintered as said before.
  • the amount of silica powder relative to the total amount of silica powder and binder substance is between 30 % and 70 % by volume, more preferably between 40 % and 60 %.
  • said high temperature during the sintering operation is between 1000 °C and 1800 °C, more preferably between 1300 °C and 1650 °C.
  • other substances or additives are applied to said mixture of silica powder and binder substance up to an amount of 40 % by volume.
  • Such other substances (additives) may be boron oxide and/or aluminum oxide, the object being to facilitate the sintering operation of the material or to modify some material properties, e.g. the coefficient of expansion.
  • Arrow 1 indicates the supply of silica powder with additives to a mixing device 2.
  • the silica with additives is produced by a grinding operation of a pre-melted glass, in this example made of silicon oxide, aluminum oxide and boron oxide.
  • the ratio of the quantities supplied to the mixing device 2 is 82 % silica, 8 % aluminum oxide, and 10 % boron oxide by volume.
  • the binder substance is a granulate material containing polyethylene and polyethylene glycol in a ratio of 50 % polyethylene granules and 50 % polyethylene glycol granulesley volume.
  • injection molding is a well-known process and is described, for example, in US-A-4507254. The process will not be further elucidated here.
  • the result of the injection molding process is a shaped product, for example a reflector of a lamp.
  • the material of the injection-molded product is still a mixture of silica glass and other substances.
  • the next operation in the method is the removal of the other substances, so that only silica glass and the desired additives remain in the material of the shaped product. Therefore, as indicated with arrow 7, the shaped product is immersed in water in a device 8. At least part of the polyethylene glycol in the material of the shaped product will dissolve in the water, whereby the material of the shaped product becomes more or less porous. Arrow 9 indicates the removal of the polyethylene glycol from the material. Subsequently, as indicated by arrow 10, the shaped product is brought into a device 11 in which it is heated so as to remove the remainder of the polyethylene glycol and all of the polyethylene from the material of the shaped product, as indicated by arrow 12.
  • the shaped product is heated for a period of 180 minutes to a temperature of 500 °C in air for this purpose.
  • the material of the shaped product is silica glass and aluminum oxide and boron oxide, but in a porous and fragile condition, so the shaped product should be carefully supplied to the sintering device 13, as indicated by arrow 14.
  • the material of the shaped product is heated to a temperature of 1550 °C for a period of 60 minutes in a hydrogen/helium mixted atmosphere, after which a non-porous, or low-porous product remains.
  • the lowering of the porosity during the treatment in the sintering device 13 will cause the product to shrink accordingly.
  • the degree of shrinkage can be predetermined, so that a product having the required dimensions can be obtained by choosing the correct (excess) dimensions of the shaped product leaving the injection molding device 5.
  • Arrow 15 indicates the final silica glass part as it leaves the sintering device 13, which product can have a relative complicated shape and narrow-tolerance dimensions.
  • the described method for manufacturing a silica glass part for a lamp assembly is only an example; a great many variations of the described method are possible.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Dispersion Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Glass Compositions (AREA)
  • Non-Portable Lighting Devices Or Systems Thereof (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)

Abstract

A method of manufacturing silica glass parts for lamp assemblies comprises of mixing silica powder with a binder substance, the step of supplying the mixture of silica powder and binder substance to an injection molding apparatus to produce a shaped product by injection molding, the step of removing the binder substance from said product, and the step of sintering the product at a high temperature. Other substances like boron oxide and/or aluminium oxide may be applied to the mixture up to an amount of 40 % by volume.

Description

A method of manufacturing silica glass parts for lamp assemblies
The invention relates to a method of manufacturing silica glass parts for lamp assemblies, i.e. parts having silica glass as a main component of its material. Such parts are, for example, the reflector of the lamp and the transparent envelope of the lamp.
Parts for lamp assemblies must often fulfil certain special requirements, so that they have to be produced from special materials to comply with such requirements. Such a special material is silica glass, which has an extremely low coefficient of expansion, can resist a high temperature, and can be transparent. These properties, separately or in combinations, are required for certain parts for lamp assemblies, for example parts of incandescent halogen lamps and high-pressure discharge lamps. In particular the low coefficient of expansion allows large local temperature differences in the material.
It is usual in halogen lamps to produce, for example, the transparent envelope (bulb) of the lamp from silica glass. Such an envelope is produced by deformation of silica glass material when heated to a high temperature. To that end, silica glass material is available on the market in the shape of a tube. To produce said envelope, the silica glass tube is heated up to a temperature between 1600 °C and 1800 °C, and then the material is deformed in a fast operation by a special deforming apparatus whereby, for example, a pinch can be produced which closes the tube. However, only silica glass parts having a relatively simple shape can be produced by such a material-deforming operation.
To produce silica glass parts having a more complicated shape, other shaping techniques can be utilized such as material removing operations, for example grinding. However, such techniques have other disadvantages and limitations. There is a need for an alternative technique for producing silica glass parts having a relatively complex shape and suitable for high- volume production.
The object of the invention is to provide a method of manufacturing silica glass parts for lamp assemblies wherein the part can have a relatively complex shape, which method can be utilized in mass manufacture.
The accomplish said object, the method of manufacturing silica glass parts for lamp assemblies comprises a step of mixing crystalline or amorphous silicon dioxide powder, hereinafter referred to as silica powder, with a binder substance, a step of supplying the mixture of silica powder and binder substance to an injection molding apparatus so as to produce a shaped product by injection molding, a step of removing the binder substance from said product, and a step of sintering the product at a high temperature.
The production is thus divided into two stages. In the first stage, the product is given the required shape, which may be any shape that can be obtained in an injection molding operation, and in the second stage the product is given the properties of silica glass.
In the first stage, silica powder is mixed with a binder substance so as to obtain a mixture which is suited to undergoing an injection molding operation. For example, such a binder substance is polyethylene mixed with polyethylene glycol. It was found that mixing of equal volumes of such a binder substance and silica powder yields a material that can be injection-molded into a product of relatively complex shape.
After the injection molding operation, the binder substance is removed from the material of the shaped product. Depending on the kind of binder substance, this removal may take place by heating of the product and/or by someother operation or process. In the second stage, after removal the binder substance, the material of the shaped product is sintered through heating of the material, so that the final silica glass product is obtained.
In one preferred embodiment, the binder substance is at least partly soluble in a liquid, preferably in water. In the above-described binder substance the polyethylene glycol can be removed at least partly by immersing the shaped product into water, in which the polyethylene glycol is dissolved. The remainder of the binder substance, including the polyethylene, may be removed by heating of the product. Subsequently the material of the shaped product can be sintered as said before.
Preferably, the amount of silica powder relative to the total amount of silica powder and binder substance is between 30 % and 70 % by volume, more preferably between 40 % and 60 %.
Preferably, said high temperature during the sintering operation is between 1000 °C and 1800 °C, more preferably between 1300 °C and 1650 °C.
In one preferred embodiment, other substances or additives are applied to said mixture of silica powder and binder substance up to an amount of 40 % by volume. Such other substances (additives) may be boron oxide and/or aluminum oxide, the object being to facilitate the sintering operation of the material or to modify some material properties, e.g. the coefficient of expansion. The invention will now be explained with refernce to an example of a method of manufacturing a silica glass part for a lamp assembly, in which reference is made to the accompanying drawing. The drawing is only a schematic diagram.
Arrow 1 indicates the supply of silica powder with additives to a mixing device 2. In this example, the silica with additives (other substances) is produced by a grinding operation of a pre-melted glass, in this example made of silicon oxide, aluminum oxide and boron oxide. The ratio of the quantities supplied to the mixing device 2 is 82 % silica, 8 % aluminum oxide, and 10 % boron oxide by volume.
Arrow 3 indicates the supply of a binder substance to the mixing device 2. In the example, the binder substance is a granulate material containing polyethylene and polyethylene glycol in a ratio of 50 % polyethylene granules and 50 % polyethylene glycol granulesley volume.
After being mixed in the mixing device 2, the substances are supplied to an injection molding apparatus 5, as indicated by arrow 6. Injection molding is a well-known process and is described, for example, in US-A-4507254. The process will not be further elucidated here. The result of the injection molding process is a shaped product, for example a reflector of a lamp. The material of the injection-molded product is still a mixture of silica glass and other substances.
The next operation in the method is the removal of the other substances, so that only silica glass and the desired additives remain in the material of the shaped product. Therefore, as indicated with arrow 7, the shaped product is immersed in water in a device 8. At least part of the polyethylene glycol in the material of the shaped product will dissolve in the water, whereby the material of the shaped product becomes more or less porous. Arrow 9 indicates the removal of the polyethylene glycol from the material. Subsequently, as indicated by arrow 10, the shaped product is brought into a device 11 in which it is heated so as to remove the remainder of the polyethylene glycol and all of the polyethylene from the material of the shaped product, as indicated by arrow 12. The shaped product is heated for a period of 180 minutes to a temperature of 500 °C in air for this purpose. After the removal of the other substances, the material of the shaped product is silica glass and aluminum oxide and boron oxide, but in a porous and fragile condition, so the shaped product should be carefully supplied to the sintering device 13, as indicated by arrow 14. In the sintering process in device 13, the material of the shaped product is heated to a temperature of 1550 °C for a period of 60 minutes in a hydrogen/helium mixted atmosphere, after which a non-porous, or low-porous product remains.
The lowering of the porosity during the treatment in the sintering device 13 will cause the product to shrink accordingly. However, the degree of shrinkage can be predetermined, so that a product having the required dimensions can be obtained by choosing the correct (excess) dimensions of the shaped product leaving the injection molding device 5.
Arrow 15 indicates the final silica glass part as it leaves the sintering device 13, which product can have a relative complicated shape and narrow-tolerance dimensions.
The described method for manufacturing a silica glass part for a lamp assembly is only an example; a great many variations of the described method are possible.

Claims

CLAIMS:
1. A method of manufacturing silica glass parts for lamp assemblies comprising the following steps: silica powder is mixed with a binder substance; the mixture of silica powder and binder substance is supplied to an injection molding apparatus so as to produce a shaped product by injection molding; the binder substance is removed from said product; the product is sintered at a high temperature.
2. A method as claimed in claim 1, characterized in that other substances are applied to said mixture up to an amount of 40 % by volume.
3. A method as claimed in any one of the preceding claims, characterized in that the binder substance is at least partly soluble in a liquid.
4. A method as claimed in claim 3, characterized in that said liquid is water.
5. A method as claimed in any one of the preceding claims, characterized in that the amount of silica powder, relative to the total amount of silica powder and binder substance, is between 30 % and 70 % by volume, preferably between 40 % and 60 %.
6. A method as claimed in any one of the preceding claims, characterized in that said high temperature is between 1000 °C and 1800 °C, preferably between 1300 °C and 1650 °C.
PCT/IB2004/050286 2003-03-24 2004-03-18 A method of manufacturing silica glass parts for lamp assemblies WO2004085322A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP03100748.7 2003-03-24
EP03100748 2003-03-24

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WO2004085322A1 true WO2004085322A1 (en) 2004-10-07

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007079001A1 (en) * 2005-12-31 2007-07-12 Corning Incorporated Powder injectionmolding method of glass and glass-ceramics
EP3950609A1 (en) 2020-08-04 2022-02-09 Sick Ag Optoelectronic sensor, glass lens and method for manufacturing a glass lens
CN113429118B (en) * 2021-06-17 2022-05-24 贵州航天电器股份有限公司 Glass blank powder injection molding process

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4352390A (en) * 1978-12-04 1982-10-05 Sherwood Refractories, Inc. Precision silica cones for sand casting of steel and iron alloys
JPH04349130A (en) * 1991-05-27 1992-12-03 Nitto Chem Ind Co Ltd Production of quartz glass molded body

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4352390A (en) * 1978-12-04 1982-10-05 Sherwood Refractories, Inc. Precision silica cones for sand casting of steel and iron alloys
JPH04349130A (en) * 1991-05-27 1992-12-03 Nitto Chem Ind Co Ltd Production of quartz glass molded body

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
"Ceramics and glasses - Engineered Materials Handbook", 1987, ASM INTERNATIONAL, USA, XP002283775 *
PATENT ABSTRACTS OF JAPAN vol. 0172, no. 05 (C - 1051) 22 April 1993 (1993-04-22) *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007079001A1 (en) * 2005-12-31 2007-07-12 Corning Incorporated Powder injectionmolding method of glass and glass-ceramics
EP3950609A1 (en) 2020-08-04 2022-02-09 Sick Ag Optoelectronic sensor, glass lens and method for manufacturing a glass lens
DE102020120565A1 (en) 2020-08-04 2022-02-10 Sick Ag Photoelectric sensor, glass lens and method of making a glass lens
CN113429118B (en) * 2021-06-17 2022-05-24 贵州航天电器股份有限公司 Glass blank powder injection molding process

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