Patent Description:
Tempered and laminated bended glass is extensively used for side-lites, back-lites, laminated windshields and laminated sunroofs for automotive business to provide good resistance to breakage as well as an aesthetically appealing shape that complements the design of the vehicle. In order to perform the bending, sheet glass must be heated to its deformation point and then bent to the required shape. In a typical glass bending technology, a plenum or other suitable means is located below rolls of the conveyors to blow the gas upwardly against the heated sheet of glass that is lifted upwardly against the holder. Pressurized gas such as heated air in the furnace heating chamber is supplied to the plenum. The pressurized gas is forced from the plenum through an array of gas jet pumps which amplify the flow to provide fluid pressure on the underside of the glass sheet in an amount sufficient to lift it above the conveyor into engagement with the holder. A vacuum is drawn with the holder embodiments having the surfaces so as to assist the upwardly blown gas in lifting the sheet of glass off the conveyor. Vertical movement of the holder downwardly prior to the lifting facilitates the lifting of the glass into engagement with the holder and subsequent upward movement of the holder then allows the mould to move under the holder to receive the sheet of glass for bending.

On the other hand, in order to prevent damage to the tooling (e.g. bending moulds, transport rollers) brought into contact with the heated glass plate, the tooling is normally covered by means of a heat resistant separation material, mostly a cloth made out of fibers. The use of textile fabrics out of <NUM>% glass fibers is known. The disadvantage of these glass fiber cloths is that it doesn't resist the mechanical action during the glass shaping process. Also the use of textile fabrics, partially or fully consisting out of metal fibers is known. Using these fabrics as mould coverings, the mechanical action of the bending process is withstand better. <CIT> discloses a heat resistant separation fabric for use as tool covering in the production of car glass. Such heat resistant separation materials can be knitted fabrics, made from yarns spun with stainless steel fibers. Alloys such as AISI <NUM> or AISI <NUM>, AISI <NUM>, or other alloys out of the AISI <NUM> type can be used. <CIT> discloses a knitted fabric comprising steel fibers. The knitted fabric has increased number of stitches to reduce the risks for markings on the glass. Another publication <CIT> discloses the use of a cover for rotating elements supporting a sheet of material like glass or for the element used to bring the sheet of material in the required shape. The cover can be knitted fabric, woven fabric or fiber web built from a nickel-chromium alloy material.

However, during the operation of glass bending, when a glass is not present, e.g. by glass breakage or by some other incidence, upwardly blown gas from the plenum will be sucked by the vacuum drawn from the holder through textile fabrics. The textile fabric will then be exposed to the higher amount of hot oxygen flow that will be inflated in the furnace since the upwardly blown gas is a hot air stream with a temperature, e.g. at about <NUM>. As a result, the temperature of the textile fabric will increase to about or even more than <NUM> what makes that the textile fabric starts to carbonize. This higher temperature together with higher amount of oxygen and the carbonization of the textile fabric may induce burning or combustion of the textile fabric on the tooling.

It is a general object of the invention to avoid the drawbacks of the prior art.

It is a particular object of the invention to provide a heat resistant separation fabric that achieves desirable safety features and appropriate serviceability.

It is another object of the invention to provide a heat resistant separation fabric that is robust and has a long lifetime in multiple time use for use as tool covering in the production of glass products at high temperatures over <NUM>.

Yet another object of the invention to provide a heat resistant separation fabric that can be manufactured by existing process.

The heat resistant separation fabrics for use as tool covering in the production process of glass products, e.g. of car glass, where the tool covering is in contact with glass at a temperature above the softening point of glass can be made from metal fiber yarns.

A heat resistant separation fabric for use as tool covering in the production of glass products at temperatures over <NUM> according to the invention is defined in the independent claim <NUM>. A spun fiber yarn according to the invention is defined in the independent claim <NUM>. A method of using a heat resistant separation fabric according to the invention is defined in claim <NUM>.

According to the invention, there is provided a heat resistant separation fabric for use as tool covering in the production of glass products at temperatures over <NUM>, wherein the heat resistant separation fabric is made of fiber yarns, and wherein said fiber yarns comprise metal fibers out of a first material consisting of:.

Preferably, said first material contains <NUM> to <NUM> weight percent Fe. More preferably, said first material contains <NUM> to <NUM> weight percent Fe. For instance, said first material may contain <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> weight percent Fe. The first material contains limited amount of Fe which can be oxidized into iron oxide. Iron oxide is detrimental to the properties of the heat resistant separation fabric.

Moreover, said first material may also contain any one or more than one of silicon (Si), manganese (Mn), and copper (Cu), each in a range between <NUM> weight percent to <NUM> weight percent, and preferably between <NUM> weight percent to <NUM> weight percent.

In addition, the first material may contain any one or more than one of the following elements, e.g. carbon (C), nitrogen (N), cobalt (Co), magnesium (Mg), neodymium (Nb), phosphorus (P), sulphur (S), tin (Sn), titanium (Ti), vanadium (V) and tungsten (W), each less than <NUM> weight percent and preferably less than <NUM> weight percent, e.g. between <NUM> weight percent to <NUM> weight percent.

The heat resistant separation fabrics according to the present invention can be made from different fiber yarns. The heat resistant separation fabrics according to the present invention can also be made from blends of metal fiber yarns with any other heat resistant fibers, e.g. glass or ceramic fibers. The fiber yarns according to the present invention may comprise carbon fibers or silica fibers. For instance, the heat resistant separation fabric is made from a spun fiber yarn. The spun fiber yarn may comprises an intimate blend of staple fibers. The intimate blend comprises staple fibers out of said first material and staple fibers out of a second material having a different composition than the above first material. The spun metal fiber yarn of the invention can be a plied yarn, e.g. a two-ply or a three-ply yarn, e.g. as disclosed in <CIT>. Preferably, each of the plies of the yarn can comprise an intimate blend of staple fibers, wherein the intimate blend comprises staple fibers out of the first material and staple fibers out of a second material having a different composition than the first material. More preferably, all plies of the plied yarn have the same fiber composition. In a preferred embodiment, the spun metal fiber yarn consists out of an intimate blend of staple fibers out of the first material and staple fibers out of a second material having a different composition than the first material.

As an example, the spun metal fiber yarn is a plied yarn. The plied yarn comprises at least one ply comprising or consisting out of a single yarn out of staple fibers out of the first material; and at least one ply comprising or consisting out of a single yarn out of staple fibers out of a second material.

As another example, the spun metal fiber yarn may comprise or consist out of a core-sheath metal fiber yarn. The core of the yarn comprises or consists out of staple fibers out of the first material; and the sheath comprises or consists out of staple fibers out of a second material.

Yet another example, the metal fiber yarn comprises a strand. The strand comprises or consists out of staple fibers out of the first material. The strand is wrapped with a strand comprising or consisting out of staple fibers out of a second material.

The second material can be a stainless steel alloy of the <NUM> series according to ASTM A313. Preferred examples are <NUM>, <NUM> and <NUM> (according to ASTM A313). The second material can also be any other heat resistant material like glass, silica, carbon, ceramic and/or basalt.

As an example, in the yarn, the weight ratio of fibers out of the first material to the weight ratio of the fibers out of the second material is at least <NUM>, more preferably at least <NUM>.

In preferred embodiments, the heat resistant separation fabric consists out of spun metal fiber yarns out of said first material. It means that all yarns in the fabric are out of fibers out of the first material, i.e. the heat resistant separation fabric does not comprise other fiber yarn than said metal fiber yarns out of said first material.

Surprisingly, the heat resistant separation fabrics according to the present invention have shown significant flame retardant properties. When they are covered on tooling used in car glass production at temperatures over <NUM>, the heat resistant separation fabric has prolonged lifetime.

Limiting Oxygen Index (LOI) testing is used to measure flame retardant properties of the material. According to EN ISO <NUM>-<NUM>, Limiting Oxygen Index (LOI) is defined as the minimum concentration of oxygen, expressed as volume, in a mixture of oxygen and nitrogen that will support flaming combustion of a material. Previous LOI studies focus mostly on plastic and textiles. Generally, textiles having LOI values of <NUM> vol% or less burn rapidly, those having values in the range of <NUM> to <NUM> vol% burn slowly, and those with LOI more than <NUM> vol% exhibit some level of flame retardancy in air, which has an oxygen concentration of about <NUM> vol%.

The LOI of the heat separation fabric according to the invention is in general more than <NUM> vol%, for some examples is even more than <NUM> vol%, and for some preferred embodiments is even more than <NUM> vol%. The inventive heat resistant separation fabric presents an excellent flame retardant property.

On the other hand, the invention fiber fabric also provides better corrosion resistance, and comparable tensile strength than other available heat resistant separation fabric used in the same application.

In preferred embodiments, the equivalent diameter of the staple fibers out of the first material is between <NUM> and <NUM>, preferably between <NUM> and <NUM>. With equivalent diameter of the staple fibers is meant the diameter of a circle that has the same cross sectional area as the cross section of the fiber that is not necessarily having a circular cross section.

In preferred embodiments, the equivalent diameter of the staple fibers out of the second material is between <NUM> and <NUM>, preferably between <NUM> and <NUM>.

In a preferred embodiment, the staple fibers out of the first material and the staple fibers out of the second material have substantially a same equivalent diameter, e.g. <NUM>.

Preferably, the staple fibers out of the first material and/or the staple fibers out of the second material are manufactured using the known bundled drawing technology, as is e.g. described in in <CIT>.

Preferred yarn counts of the spun metal fiber yarn are between <NUM> and <NUM> (meaning between <NUM> tex and <NUM> tex), more preferably between <NUM> and <NUM> (meaning between <NUM> tex and <NUM> tex). Preferably, such yarns are two ply or three ply yarns.

The heat resistant separation fabric can be used as tool covering in the production of glass products at temperatures over <NUM>, more preferably over <NUM>. The heat resistant separation fabric comprises or consists out of spun metal fiber yarns as in any embodiment of the invention. Preferably, the heat resistant separation fabric has a specific weight between <NUM> and <NUM>/m<NUM>, more preferably between <NUM> and <NUM>/m<NUM>.

As an example, the heat resistant separation fabric can be felts or tapes, e.g. quench tape. In a preferred embodiment, the heat resistant separation fabric can be a knitted (e.g. a weft knitted fabric), a woven or a braided fabric. <CIT>, <CIT>, and <CIT> disclose some fabric constructions of such heat resistant separation fabrics.

In an exemplary embodiment, the heat resistant separation fabric is a weft knitted fabric comprising or consisting out of spun metal fiber yarns as in the invention, for covering a mould for bending glass plates at elevated temperatures of at least <NUM>, e.g. of at least <NUM>.

In another exemplary embodiment, the heat resistant separation fabric is a sleeve, preferably a knitted sleeve, more preferably a weft knitted sleeve, for covering a roller.

According to the invention, there is provided a method of using a heat resistant separation fabric as in the invention. The method comprises the step of covering tooling in glass production with the heat resistant separation fabric. In use the temperature of the heat resistant separation materials is higher than <NUM>, preferably higher than <NUM>, more preferably higher than <NUM>. The tooling covered with the heat resistant separation fabric is brought in contact with glass panels. Such tooling can e.g. be rollers for the transport of glass panels or moulds for bending glass panels.

A metal fiber yarn that has been spun out of <NUM>% by weight out of a first material. The first material has the following composition:.

In addition, the material may contain one or more than one of the following elements, e.g. carbon (C), nitrogen (N), cobalt (Co), magnesium (Mg), neodymium (Nb), phosphorus (P), sulphur (S), tin (Sn), titanium (Ti), vanadium (V) and tungsten (W), each less than <NUM> wt%.

The metal fibers have an equivalent diameter of about <NUM>. The metal fibers have been made by means of bundled drawing. The bundles of fibers of continuous length made via bundled drawing have been transformed into staple fibers by means of stretch breaking. The yarns have been spun by means of ring spinning, on a long staple type ring spinning frame. The yarns have been ply twisted into a two ply yarn of count <NUM>/<NUM> (<NUM>*<NUM> tex). The plied yarn has been knitted into a single jersey fabric of <NUM>/m<NUM> that has been tested. This is sample A for the comparative testing.

The behavior of sample A has been compared with a sample of the same fabric construction but where the spun yarns consisted for <NUM>% out of <NUM> equivalent diameter fibers out of <NUM>-related alloy (sample B for the comparison). The <NUM>-related alloy has the same specification as alloy <NUM> (according to ASTM A <NUM>) but with a modified nickel content (between <NUM> and <NUM> % by weight), a modified chromium content (between <NUM> and <NUM> % by weight) and a modified molybdenum content (between <NUM> and <NUM> % by weight).

Both metal fiber types of sample A and sample B have been made by means of bundled drawing, as is e.g. described in <CIT>.

Inventive sample A showed the benefit that it can be removed from a tooling after use in hot glass processing, and be put on again and re-used for multiple times. A comparison was made at <NUM>. Sample B showed much less lifetime in multiple use than sample A.

Limiting Oxygen Index (LOI) is measured for sample A and B. Sample B has a measured LOI of <NUM> vol% oxygen and flame time of <NUM> seconds. Sample A showed significantly better flame retardant property than sample B: there was no ignition at sample A at <NUM> vol% oxygen, which is the maximum oxygen volume that can be applied safely in the test.

Sample A showed excellent heat resistant properties at high temperature. After keeping the sample during <NUM> hours at <NUM>, the sample still showed a good appearance and good performance characteristics, such as strength and elongation of the sample in tensile loading. Sample A and sample B have been tested in cyclic impact loading mode at a temperature of <NUM>. Inventive sample A showed a comparable wear and less damage in the cyclic impact loading test than sample B.

Sagging is the heat resistant separation fabric coming somewhat loose from the surface of the tooling when the tooling is brought in use at high temperature. Sagging is believed to be caused by creep phenomena in the fibers. Sagging can cause quality problems in glass that is contacted by a sagging fabric. In sagging simulation, a fabric is clamped in a ring. The ring with the clamped sample is put in an oven at high temperature (here <NUM>), a plunger is pushed into the fabric until a specific force is attained, after which the plunger is withdrawn. This is repeated <NUM> times. Sagging is expressed as the increase in distance the plunger has to travel before it touches the fabric and force is build up. In the sagging test, sample A behaviors lightly better than sample B: Sample B showed a result of <NUM>, whereas sample A showed a result of <NUM>.

Sample A has been analyzed via Scanning Electron Microscopy (SEM) after heating it to <NUM> in air. Surprisingly, it was observed that the fibers out of the first material had not been much attacked by the heating in air.

Claim 1:
A heat resistant separation fabric for use as tool covering in the production of glass products at temperatures over <NUM>, wherein the heat resistant separation fabric is made of fiber yarns, and wherein said fiber yarns comprise metal fibers out of a first material consisting of:
<NUM> to <NUM> weight percent chromium,
<NUM> to <NUM> weight percent nickel,
<NUM> to <NUM> weight percent molybdenum,
<NUM> to <NUM> weight percent iron,
optionally one or more than one of silicon, manganese, and copper, each in a range between <NUM> weight percent to <NUM> weight percent, and
optionally one or more than one of carbon, nitrogen, cobalt, magnesium, neodymium, phosphorus, sulphur, tin, titanium, vanadium and tungsten, each less than <NUM> weight percent.