GB2120127A

GB2120127A - Method of applying interleaving material to glass sheets

Info

Publication number: GB2120127A
Application number: GB08214039A
Authority: GB
Inventors: Paul Francis Duffer; Joseph David Kelly; Helmut Franz
Original assignee: PPG Industries Inc
Current assignee: PPG Industries Inc
Priority date: 1982-05-14
Filing date: 1982-05-14
Publication date: 1983-11-30
Also published as: GB2120127B

Abstract

A method for applying a powdered interleaving material to a glass surface comprising the steps of: a. dispersing a powdered interleaving material in water to form an aqueous slurry; b. applying said aqueous slurry of the powdered interleaving material to a glass surface; and c. drying the aqueous slurry to obtain a uniform adherent layer of interleaving material on the glass surface, and an article of manufacture which comprises a. a plurality of glass sheets stacked in facing relationship; and b. adherent to the interfacing surface of the glass sheets a uniform distribution of a powdered interleaving material applied by the above method.

Description

SPECIFICATION Method of applying interleaving material to glass sheets The present invention relates generally to the art of separating glass sheets and relates more particularly to the art of applying powdered interleaving material.

It is well known in the art that stacked glass sheets may be protected from surface damage by the use of various interleaving material such as paper or powdered materials such as wood flour, polyethylene, polystyrene or polyacrylates. Powdered materials are preferably finely divided, fairly uniform in size distribution, and freeflowing so that they may be applied by means of conventional, commercially available equipment.

U.S. Patent No. 3,723,312 to Hay discloses using a dedusted agglomerated salicyclic acid, mixed with an inert separator material such as polystyrene beads. This particulate interleaving material may be applied to glass by mechanical dusters or other particulate application equipment known to those skilled in the art of dusting glass with wood flour or other inert particulate interleaving materials.

U.S. Patent No. 4,200,670 to Albach describes a method of treating glass sheets to be stacked by applying water, a stain inhibiting material such as ammonium chloride, and dry particles of a mechanical separator such as wood flour, to such sheets in a plurality of sequential steps. According to one specific embodiment, the water and stain inhibitor are first applied to the glass as an aqueous solution of the latter to provide a wet layer on the sheet surface, and then separately applying a dry particulate layer of a mechanical separator to the wet layer.The method can also be carried out by first spraying the glass surface with water alone, and then separately applying layers of a stain inhibitor and a mechanical separator in dry powdered form to the layer of water; or by first applying a layer of a mixture of dry powdered stain inhibitor and mechanical separator and then spraying this layer of dry material with water.

The present invention involves the application of powdered interleaving material to a glass surface in the form of an aqueous slurry.

According to the present invention a method is provided for applying a powdered interleaving material ton a glass surface comprising the steps of: a. dispersing a powdered interleaving material in water to form an aqueous slurry; b. applying said aqueous slurry of the powdered interleaving material to a glass surface; and c. drying the aqueous slurry to obtain a uniform adherent layer of interleaving material on the glass surface.

The invention includes an article of manufacture which comprises: a. a plurality of glass sheets stacked in facing relationship; and b. adhered to the interfacing surfaces of the glass sheets a uniform distribution of a powdered interleaving material applied by this method.

Although the slurry-applied powdered interleaving is sufficiently adherent to the glass to withstand handling and transporting, it is easily removed by washing prior to further processing operations such as for example coating or laminating, with no adverse effects on such subsequent processing operations.

The powdered interleaving material may be any finely divided support material such as for example vermiculite, polyethylene, polystyrene or polymethylmethacrylate, but is preferably a porous cellulose material such as for example wood floor or rice flour. The wood flour may be applied at a coverage of in the range of 20,000 to 25,000 square feet of glass per pound of wood flour.

In a preferred embodiment of the present invention, a quantity of about 1 to 100 grams, preferably about 10 to 20 grams, of wood flour is dispersed per liter of water. This aqueous slurry is applied to glass surfaces by any conventional technique, preferably by flooding or spraying. The slurry may be dried at elevated temperatures, but preferably is allowed to dry at ambient temperature. Upon drying, the glass surface is uniformly covered with the interleaving material.

In a most preferred embodiment of the present invention the interleaving material is impregnated with, as a stain inhibitor, a strongly acidic organic compound as disclosed in U.S. Serial No. 229,208 filed on 28th January, 11981 by Paul Francis Duffer, Joseph David Kelly and Helmut Franz entitled "Acidified Powdered Interleaving", the disclosure of which is incorporated herein by reference. In an alternate preferred embodiment of the present invention, the slurry comprises a porous support material such as for example wood flour dispersed in an aqueous solution of a strongly acidic organic compound. In these embodiments, the strongly acidic organic compound is characterized as being watersoluble, solid at ambient temperatues, and having a pH less than about 3 when dissolved in water at a concentration of about 1 percent.Suitabie organic acids include the strongly acidic organotin compounds, such as for example organotin halides, especially alkyltin halides e.g. methyltin trichloride, dimethyltin dichloride, trimethyltin chloride and mixtures thereof (e.g. a mixture of 80% by weight of dimethyltin dichloride and 20% by weight of methyltin trichloride. The amount of the alkyltin halide may be for example about 0.1 to 5 percent based on the weight of the water.

Organic acids such as, for example, citric, malic or tartaric acid are preferred if the treated glass is to be tempered without washing, since these acids will completely burn off, leaving no residue on the surface of the tempered glass sheet.

The present invention will be further understood from the description of the following specific Examples.

EXAMPLE I An aqueous slurry is formed by dispersing 1 gram of wood flour per 100 millilitres of water which contains 1 percent by weight of a mixture of 80 percent by weight dimethyltin dichloride and 20 percent by weight methyltin trichloride. The slurry is applied to glass at ambient temperature and allowed to dry. The volume of slurry is such that the coverage rate is about 20,000 square feet of glass per pound of wood flour. A uniform distribution of interleaving material on the glass surface is obtained. Treated glass sheets are stacked and exposed to 140"F (about 60 C) at 100 percent relative humidity for accelerated staining tests. The glass surfaces are free of stain after more than 45 days of exposure to the test conditions.Moreover, the interleaving material is sufficiently adherent to remain on the glass throughout handling and transportation, but is easily removed by conventional washing techniques prior to subsequent processing such as coating or laminating.

EXAMPLE II An aqueous slurry is formed by dispersing 1 gram of wood flour per 100 millilitres of water which contains 2 percent by weight boric acid. The slurry is applied to glass sheets at ambient temperatures, and dried to leave a uniform layer of interleaving material on the glass surfaces. Treated glass sheets are stacked and subjected to accelerated staining tests as in the previous Example. The glass survived for 85 days without major stain damage.

EXAMPLE 111 Glass treated with an aqueous slurry of wood flour in 1 percent citric acid withstood more than 34 days of accelerated test conditions without heavy staining.

EXAMPLE IV Glass treated with an aqueous slurry of wood flour and 1 percent tartaric acid survived 34 days of accelerated testing in excellent conditions.

EXAMPLE V Glass treated with an aqueous slurry of rice flour and 2 percent boric acid remained in excellent condition after 59 days of accelerated staining tests.

The above examples are offered to illustrate the present invention. Various modifications, such as the use of other powdered interleaving materials, with or without stain inhibiting materials, and various concentrations and application techniques, are included within the scope of the invention, which is defined by the following claims.

Claims

1. A method for applying a powdered interleaving material to a glass surface comprising the steps of: a. dispersing a powdered interleaving material in water to form an aqueous slurry; b. applying said aqueous slurry to the powdered interleaving material to a glass surface; and c. drying the aqueous slurry to obtain a uniform adherent layer of interleaving material on the glass surface.

2. A method according to claim 1 wherein the powdered interleaving material is wood flour.

3. A method according to claim 2 wherein the wood flour is dispersed in water at a concentration of about 1 to 100 grams per litre.

4. A method according to claim 3 wherein the wood flour is dispersed in water at a concentration of about 10 to 20 grams per litre.

5. A method according to any of claims 1 to 4 wherein the aqueous slurry further comprises a stain inhibitor.

6. A method according to claim 5 wherein the stain inhibitor is a strongly acidic organic compound.

7. A method according to claim 6 wherein the stain inhibitor is an organotin compound.

8. A method according to claim 7 wherein the organotin compound is methyltin triclhle- ride, dimethyltin dichloride, trimethyltin chl- ride or a mixture thereof.

9. A method according to claim 8 wherein the organotin compound is a mixture compris- ing 80 percent by weight dimethyltin dichloride and 20 percent by weight meihyltin "dri- chloride.

10. A method according to claim 9 wherein the aqueous slurry comprises about gram of wood flour per 100 millilitres of water.

11. A method according to claim 7, 8, 9 or 10 wherein the aqueous slurry comprises about 0.1 to 5 percent of the organotin compound based on the weight of the water.

12, A method of applying a powdered interleaving material to a glass surface substantially as herein described with reference to and as illustrated in any of the Examples.

1 3. An article of manufacture which comprises; a. a plurality of glass sheets stacked in facing relationship; and b. adhered to the interfacing surfaces of the glass sheets a uniform distribution of a pow dered interleaving material applied by a method as claimed in any of the preceding claims.

1 4. An article according to claim 13, wherein the interleaving material is wood flour applied at a coverage of in the range of 20,000 to 25,000 square feet of glass per pound of wood flour.