CA1036823A - Method of strengthening glass containers - Google Patents
Method of strengthening glass containersInfo
- Publication number
- CA1036823A CA1036823A CA210,487A CA210487A CA1036823A CA 1036823 A CA1036823 A CA 1036823A CA 210487 A CA210487 A CA 210487A CA 1036823 A CA1036823 A CA 1036823A
- Authority
- CA
- Canada
- Prior art keywords
- glass
- container
- synthetic resin
- coating
- bottles
- Prior art date
- Legal status (The legal status 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 status listed.)
- Expired
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- Surface Treatment Of Glass (AREA)
- Details Of Rigid Or Semi-Rigid Containers (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A glass container is provided with a compressive stress layer at its exterior surface by the replacement of sodium ions in the glass surface with potassium ions of larger atomic diameter and the container is then provided with a plastic enveloping sheath of a thickness of .003" up to about 0.010"
to provide a shock resistant, shard-retaining envelope for the container, where said sheath is applied while said container is at temperature of approximately 300° F. to 600° F.
A glass container is provided with a compressive stress layer at its exterior surface by the replacement of sodium ions in the glass surface with potassium ions of larger atomic diameter and the container is then provided with a plastic enveloping sheath of a thickness of .003" up to about 0.010"
to provide a shock resistant, shard-retaining envelope for the container, where said sheath is applied while said container is at temperature of approximately 300° F. to 600° F.
Description
This invention relates to glass containers and particularly to a method of producing glass containers of greatly increased effective strength and shock resistance by a combination of ion exchange treatment of the outer surface of the container to provide a compressive stress layer and a subsequent jacketing of the container with a syn-tehtic resin coating of such -thick-ness as to form an enveloping shock resistant sheath.
Ion exchange strengthening of glass surfaces to strengthen *he same by producing a compression layer at the glass surface is known in the art. For instance, Poole et al United States Patent 3,607,172, dated September 21, 1971, discloses a method of producing such a compres.sive layer in soda lime glass by spraying hot glass containers with a water solution of a potas-sium salt to substitute potassium ions for sodium ions a-t -the glass surface, the potassium ions having a larger atomic diameter than the sodium ions.
Also, application of a synthetic resin coating to glass bottles is known in the art. Representative patents showing such coatings are Smith et al United States Patent 3,362,843, dated January 9, 1968 and Clock United States Patent 3,415,673, dated December 10,1968. In the latter patent glass containers are dipped in polyethylene solutions to provide an adherent substrata and are then provided with a coating of e-thylene-acrylic acid copolymer to a thickness of about.010" by spraying the coating material on the glass article with an electrostatic powder spray gun, then heating the article to fuse the power to -the glass article. ~
'`~
1 In a Poole et al United States Patent 3,743,491, dated July 3, 1973, there is disclosed a method of strengthening glass articles by ion exchange treatment and also rendering the articles abrasion-resistant by applying polyethyene or similar synthetic resin materials to the glass surface after firstlreating the la-tter with metal oxides such as tin oxide or various titanates to provide a surface to which -the final polyethylene coa-ting will adhere. In this method the polyethylene coating is rela-tively thin and con-tributes nothing to the strength or shock resistance of the container, being provided solely to make the container surface lubricious and thus render the same resistant to abrasion.
The treatment of glass containers to render them abrasion resis-tant by applying a metal oxide coating to the glass con-tainer while the same is in a heated condition and then treating the same with a polyethylene or other polymer coating after the glass has cooled to approximately 200 F. is widely practiced and well known. Eowever, the so-called "cold end" coating of polyethylene or other polymer is not in any sense comparable to the resin of -the present invention. In conventional abrasion resistant treatment the final polyethylene coating is molecular in thickness and is physically unmeasurable, being of the order of a small fraction of a micron. This coating is applied merely to give the article surface lubricity and does not in any sense form a physical film or envelope of any strength characteristics whatever.
SUMMARY OF TEE INVENTION
In practising the method of the present invention -the glass surface is first subjected to ion exchange -treatment to produce 1036~Z3 1 a compressive surface layer by substituting ions of larger atomic diameter for ions of smaller atomic diameter. This may be effected as fully described in the aforementioned U. S. Patent 3,607,~72 wherein a water solution of tripotassium phosphate is sprayed on the hot glass surface a-t a temperature a-t or slightly below the s-train point of the glass so that the solution pyrolyzes to deposit the po-tassium salt on the glass surface. The glass is then cooled gradually so -that its temperature remains sufficiently high for a period of time which is long enough to permit effective ion ex-change.
Other potassium salts may be employed, for instance, di-potassium hydrogen phosphate or potassium carbonate, although -tri-potassium phosphate is believed to be of superior effectiveness.
Subsequen-t to the ion exchange strengthening step a laye~ of plas-tic material i9 applied of sufficient -thickness to form a protective plastic envelope a~out -the article, such envelope having a minimum thickness of approximately .003" and preferably from .004" to .010". The only upper limitation on thickness of the plastic shea-th is one of economy of material and cost of appli-cation.
Glass con-tainers being treated in accordance with the method of -the present invention do not require the abrasion resistance treatment described above and disclosed in Patent 3,743,491 unless there is a substantial delay between the ion exchange strengthening step and the final provision of the plastic sheath, in which case the abrasion resistance treatment will prevent scratching of the strengthened glass surface prior -to the final plastic sheath application.
~03~;~23 Since the glass is subjected to the potassium salt solu-tion spray at a temperature in the general range of 1000 F. and is then gradually cooled to a temperature of approximately 20Q F., and since the plastic application in preferred embodiments des-cribed later herein requires the glass to be at a temperature of approximately 600 F., it is desirable to effect the plastic coating treatment by interruption of the cooling process which occurs during p~ssage of the articles through the usu~l annealing lehr, such interruption occurring when the glass reaches the proper temperature for plastic application.
In one broad aspect the present invention provides the method of producing a strengthened soda-lime glass container com-prising replacing alkali-metal ions in an exterior surface thereof with larger alkali-metal ions with the glass at an elevated tem-perature below the strain point thereof to produce a compression layer of glass at such surface, and subsequently forming on said surface a synthetic resin coating of a thickness of at least 0.003" up to about 0.010" to provide a protective, shock-resisting, shard-retaining encapsulating sheath for said container, said synthetic resin coating being applied with said container at an elevated temperature between approximately 300 and 600 F.
EMBODIMENTS OF THE INVENTION
In practising the present invention bottles are sprayed with a water solution of tripotassium phosphate while the bottles are at or slightly below 1000 F., the approximate strain point of soda lime glass of the constituency commonly used in beverage bottles, for instance. The bottles may be thus treated shortly after they leave the bottle forming machines at a point when they are at the above approximate temperature. The bottles may be sprayed at lower temperatures but are then preferably raised in temperature to approximately 1000 F., and held at such tempera-ture for about five minutes and then coolei in about fif-teen ~ -5 j c~
I,inutes. This "soaking" period is required to effect the proper degree of substitution of potassium ions for sodium ions in the glass surface. All of the foregoing is set forth more fully in the above cited Poole et al United States Patent 3,607,172.
Other methods which exchange larger ions for smaller ions in the glass surface may also be employed to produce the desired -5a-jc/,, _ compressive layer in the glass surface by chemical means.
Dipotassium hydrogen phosphate and potassium carbonate are other potassium salts which may be employed although strengthening is believed to be achieved to the fullest extent by the employment of the aforesaid tripotassium phosphate. Following the "soaking"
period the bottles are washed to remove excess salt from the glass surface.
Following the foregoing ion exchange strengthening of the glass article the plastic jacket or sheath is applied. By way of example, powdered plastic materials which may be employed are so-called ionomers which are ionic polymers, the term being generally applied to that class of poly~,ers in which ionized carboxyl groups create ionic cross links in the intermolecular structure. A representative ionomer resin is one manufactured by E.I. DuPont de Nemours & Co. Inc. by whom it is identified as "Surlyn-AD 5001".
This resin, ground to 100 mesh or finer, can readily be applied by the use of an electrostatic 5pray gun and in such application the bottles are heated or held at a surface temperature of approximately 600 F. The spray guns are operated with a controlled standard air pressure, a controlled cascade pressure, and a constant particle charge having a potential of 70,000 volts (70 Kv.). In the tests and demonstrations made in demonstrating the effectiveness of the present invention the spray gun tip was maintained at a distance of 12" from the bottle surface, the bottles being rotated on their vertical axes and electrostatic spraying was effected for various time periods from 2 seconds to 7 seconds. The bottles were then permitted to cool to room temperature.
ywl/Jo -6-~0368Z3 1 Another representative plastic material which has been employed in tests and demonstrations of the present invention is cellulose acetate butyrate of 150 mesh par-ticle size. This material may be purchased from Eastman Chemical Products, Inc.
by whom it is identified as Tenite CAB Powder Formula 7400-W.
This material may be applied with the same electrostatic spray gun technique described in the previous example and with the bottles at approximately the same temperature.
It has been found that plastic sheaths having a thickness of from .004" to .010" give good results although a sheath thickness as low as .003" may be employed with satisfactory result.
The foregoing two resin compositions and others may be applied by employing fluidized bed techniques in place of the electrostatic spray gun of the foregoing examples. In flui-dized bed application the powdered plastic material is main-tained in a fluidized co~dition by an ascending column of dry air and the heated article is exposed to the fluidized powdered plastic material for several seconds or until the desired thicXness of coating is achieved. The plastic particles coming into contact with the heated surface of the glass bottle or - other article fuse to form a smooth continuous coating after being removed from the bed.
A full description of fluidized bed coating techniques will be found in "Technical Proceedings of the Forty-Ninth Annual Conven-tion, American Electroplaters Society, June 24-28, 1962", beginning at page 99 thereof. Asthere shown, the temperature of the article to be coated varies somewhat with various plastic powders. T~.lith polyethylene the required - 1 temperature of -the article is from 300 to 500 F. with cellu-lose acetate butyrate from 500 - 600 F. The required temperature for applying other common thermoplastic resins is given at page 102 of the aforesaid ar~icle.
The best results are substantially -the same with either of the foregoing plastic coatings and whether the same be applied by electrostatic spray gun application, or by means of a fluidized bed. It is likewise immaterial from a breaking strength standpoint whether the bottles, in addition to the 10 ion exchange strengthening, are treated for abrasion resistance in accordance with the aforesaid U. S. Patent 3,743,491 or not.
The following are average test results of a large number of 12-oz. lightweight beer bottles dropped to land on their bottoms:
With untreated bottles or bottles having the standard h tin oxide hot end trea-tment and polyethylene acid end treat-ment, filled and capped, bottles broke a* an average drop height of 2'5".
Encapsulation of the above bottles, whether otherwise 20 untreated or whether they have the above abrasion resistance treàtment, increased the drop height at which breakage occurred to 3', the thickness of the plastic sheath or en-capsulation being .004~l.
Bottle~, either plain or having abrasion resistance treatment, when subjected to the foregoing tripotassium phos-phate ion exchange strengthening, broke at an average drop height of 4'4".
The same ion exchange s-trengthened bottles with a sub-sequent encapsulating plastic sheath of a thickness of .004 1 broke at an average drop height of 5'8".
In addition to the increase in effective strength and shock resistance of the foregoing treatment, the plastic sheath or envelope renders the containers safer in handling and transpor-tation since the plastic sheath retains the bottle contents and bottle fragments or shards in instances where the glass containers become broken.
As stated above, the foregoing treatments were applied to a large number of 12-oz. lightweight amber beer bottles. ~he term "lightweight" is used here to describe conventional non-returnable bottles which are lighter in weight than convention-al multiple trip bottles. However, the improvement in breaking strength produced by the combination of ion exchange strength-ening and plastic encapsulation of the present invention is of such degree that beverage bottles and similar glass containers may be further materially lightened in weight by manufacturing them with thinner walls;than has heretofore been practicable.
The saving thus effected in material cost offsets to a substan-tial degree the cost of the plastic employed in encapsulating the containers.
The increase in strength of bottles treated in accord-ance with the present invention as reflected in the increased drop height at which the average bottle drops as se-t forth above is highly beneficial but does not tell the full story of the importance of the combined ion exchange strengthening and plastic encapsulation which are inherent in the present inven-tion. Bottles which have been strengthened by ion exchange treatment which provides a compressive stress layer at the surface of the bottle may initially resist breakage when _g_ 1036t}Z3 1 .dropped from a given height but are very likely to become chipped and such chipping removes the compressive stress layer at the chipped area so that subsequent dropping from much lesser heights would result ink~eakage.
In addition to the advantages discussed earlier herein the plastic encapsulation prevents this type of surface chipping o the bottle and thus preserves the compressive stress layer and consequently the initial streng-thening resulting from the above ion exchange treatment. Thus the practical strength increase and resistance to breakage of the bottles are very much greater than is indicated by the above test figures.
A further advantage in treating glass containers accord-ing to the present invention, which has been briefly alluded to above, resides in the fact that when encapsulated bottles do break, despite the ion exchange strengthening which forms part of the present invention, the glass fragments or shards are retained within -the plastic capsule and generally speaking the con-tents of broken bottles are likewise retained within the encapsulating sheath.
Preferred embodiments of the present invention have been described herein to illustrate the underlying principles of the invention but it is to be understood -hat numerous modi-fications may be made without departing from the broad spirit and scope of the invention.
I' --10--
Ion exchange strengthening of glass surfaces to strengthen *he same by producing a compression layer at the glass surface is known in the art. For instance, Poole et al United States Patent 3,607,172, dated September 21, 1971, discloses a method of producing such a compres.sive layer in soda lime glass by spraying hot glass containers with a water solution of a potas-sium salt to substitute potassium ions for sodium ions a-t -the glass surface, the potassium ions having a larger atomic diameter than the sodium ions.
Also, application of a synthetic resin coating to glass bottles is known in the art. Representative patents showing such coatings are Smith et al United States Patent 3,362,843, dated January 9, 1968 and Clock United States Patent 3,415,673, dated December 10,1968. In the latter patent glass containers are dipped in polyethylene solutions to provide an adherent substrata and are then provided with a coating of e-thylene-acrylic acid copolymer to a thickness of about.010" by spraying the coating material on the glass article with an electrostatic powder spray gun, then heating the article to fuse the power to -the glass article. ~
'`~
1 In a Poole et al United States Patent 3,743,491, dated July 3, 1973, there is disclosed a method of strengthening glass articles by ion exchange treatment and also rendering the articles abrasion-resistant by applying polyethyene or similar synthetic resin materials to the glass surface after firstlreating the la-tter with metal oxides such as tin oxide or various titanates to provide a surface to which -the final polyethylene coa-ting will adhere. In this method the polyethylene coating is rela-tively thin and con-tributes nothing to the strength or shock resistance of the container, being provided solely to make the container surface lubricious and thus render the same resistant to abrasion.
The treatment of glass containers to render them abrasion resis-tant by applying a metal oxide coating to the glass con-tainer while the same is in a heated condition and then treating the same with a polyethylene or other polymer coating after the glass has cooled to approximately 200 F. is widely practiced and well known. Eowever, the so-called "cold end" coating of polyethylene or other polymer is not in any sense comparable to the resin of -the present invention. In conventional abrasion resistant treatment the final polyethylene coating is molecular in thickness and is physically unmeasurable, being of the order of a small fraction of a micron. This coating is applied merely to give the article surface lubricity and does not in any sense form a physical film or envelope of any strength characteristics whatever.
SUMMARY OF TEE INVENTION
In practising the method of the present invention -the glass surface is first subjected to ion exchange -treatment to produce 1036~Z3 1 a compressive surface layer by substituting ions of larger atomic diameter for ions of smaller atomic diameter. This may be effected as fully described in the aforementioned U. S. Patent 3,607,~72 wherein a water solution of tripotassium phosphate is sprayed on the hot glass surface a-t a temperature a-t or slightly below the s-train point of the glass so that the solution pyrolyzes to deposit the po-tassium salt on the glass surface. The glass is then cooled gradually so -that its temperature remains sufficiently high for a period of time which is long enough to permit effective ion ex-change.
Other potassium salts may be employed, for instance, di-potassium hydrogen phosphate or potassium carbonate, although -tri-potassium phosphate is believed to be of superior effectiveness.
Subsequen-t to the ion exchange strengthening step a laye~ of plas-tic material i9 applied of sufficient -thickness to form a protective plastic envelope a~out -the article, such envelope having a minimum thickness of approximately .003" and preferably from .004" to .010". The only upper limitation on thickness of the plastic shea-th is one of economy of material and cost of appli-cation.
Glass con-tainers being treated in accordance with the method of -the present invention do not require the abrasion resistance treatment described above and disclosed in Patent 3,743,491 unless there is a substantial delay between the ion exchange strengthening step and the final provision of the plastic sheath, in which case the abrasion resistance treatment will prevent scratching of the strengthened glass surface prior -to the final plastic sheath application.
~03~;~23 Since the glass is subjected to the potassium salt solu-tion spray at a temperature in the general range of 1000 F. and is then gradually cooled to a temperature of approximately 20Q F., and since the plastic application in preferred embodiments des-cribed later herein requires the glass to be at a temperature of approximately 600 F., it is desirable to effect the plastic coating treatment by interruption of the cooling process which occurs during p~ssage of the articles through the usu~l annealing lehr, such interruption occurring when the glass reaches the proper temperature for plastic application.
In one broad aspect the present invention provides the method of producing a strengthened soda-lime glass container com-prising replacing alkali-metal ions in an exterior surface thereof with larger alkali-metal ions with the glass at an elevated tem-perature below the strain point thereof to produce a compression layer of glass at such surface, and subsequently forming on said surface a synthetic resin coating of a thickness of at least 0.003" up to about 0.010" to provide a protective, shock-resisting, shard-retaining encapsulating sheath for said container, said synthetic resin coating being applied with said container at an elevated temperature between approximately 300 and 600 F.
EMBODIMENTS OF THE INVENTION
In practising the present invention bottles are sprayed with a water solution of tripotassium phosphate while the bottles are at or slightly below 1000 F., the approximate strain point of soda lime glass of the constituency commonly used in beverage bottles, for instance. The bottles may be thus treated shortly after they leave the bottle forming machines at a point when they are at the above approximate temperature. The bottles may be sprayed at lower temperatures but are then preferably raised in temperature to approximately 1000 F., and held at such tempera-ture for about five minutes and then coolei in about fif-teen ~ -5 j c~
I,inutes. This "soaking" period is required to effect the proper degree of substitution of potassium ions for sodium ions in the glass surface. All of the foregoing is set forth more fully in the above cited Poole et al United States Patent 3,607,172.
Other methods which exchange larger ions for smaller ions in the glass surface may also be employed to produce the desired -5a-jc/,, _ compressive layer in the glass surface by chemical means.
Dipotassium hydrogen phosphate and potassium carbonate are other potassium salts which may be employed although strengthening is believed to be achieved to the fullest extent by the employment of the aforesaid tripotassium phosphate. Following the "soaking"
period the bottles are washed to remove excess salt from the glass surface.
Following the foregoing ion exchange strengthening of the glass article the plastic jacket or sheath is applied. By way of example, powdered plastic materials which may be employed are so-called ionomers which are ionic polymers, the term being generally applied to that class of poly~,ers in which ionized carboxyl groups create ionic cross links in the intermolecular structure. A representative ionomer resin is one manufactured by E.I. DuPont de Nemours & Co. Inc. by whom it is identified as "Surlyn-AD 5001".
This resin, ground to 100 mesh or finer, can readily be applied by the use of an electrostatic 5pray gun and in such application the bottles are heated or held at a surface temperature of approximately 600 F. The spray guns are operated with a controlled standard air pressure, a controlled cascade pressure, and a constant particle charge having a potential of 70,000 volts (70 Kv.). In the tests and demonstrations made in demonstrating the effectiveness of the present invention the spray gun tip was maintained at a distance of 12" from the bottle surface, the bottles being rotated on their vertical axes and electrostatic spraying was effected for various time periods from 2 seconds to 7 seconds. The bottles were then permitted to cool to room temperature.
ywl/Jo -6-~0368Z3 1 Another representative plastic material which has been employed in tests and demonstrations of the present invention is cellulose acetate butyrate of 150 mesh par-ticle size. This material may be purchased from Eastman Chemical Products, Inc.
by whom it is identified as Tenite CAB Powder Formula 7400-W.
This material may be applied with the same electrostatic spray gun technique described in the previous example and with the bottles at approximately the same temperature.
It has been found that plastic sheaths having a thickness of from .004" to .010" give good results although a sheath thickness as low as .003" may be employed with satisfactory result.
The foregoing two resin compositions and others may be applied by employing fluidized bed techniques in place of the electrostatic spray gun of the foregoing examples. In flui-dized bed application the powdered plastic material is main-tained in a fluidized co~dition by an ascending column of dry air and the heated article is exposed to the fluidized powdered plastic material for several seconds or until the desired thicXness of coating is achieved. The plastic particles coming into contact with the heated surface of the glass bottle or - other article fuse to form a smooth continuous coating after being removed from the bed.
A full description of fluidized bed coating techniques will be found in "Technical Proceedings of the Forty-Ninth Annual Conven-tion, American Electroplaters Society, June 24-28, 1962", beginning at page 99 thereof. Asthere shown, the temperature of the article to be coated varies somewhat with various plastic powders. T~.lith polyethylene the required - 1 temperature of -the article is from 300 to 500 F. with cellu-lose acetate butyrate from 500 - 600 F. The required temperature for applying other common thermoplastic resins is given at page 102 of the aforesaid ar~icle.
The best results are substantially -the same with either of the foregoing plastic coatings and whether the same be applied by electrostatic spray gun application, or by means of a fluidized bed. It is likewise immaterial from a breaking strength standpoint whether the bottles, in addition to the 10 ion exchange strengthening, are treated for abrasion resistance in accordance with the aforesaid U. S. Patent 3,743,491 or not.
The following are average test results of a large number of 12-oz. lightweight beer bottles dropped to land on their bottoms:
With untreated bottles or bottles having the standard h tin oxide hot end trea-tment and polyethylene acid end treat-ment, filled and capped, bottles broke a* an average drop height of 2'5".
Encapsulation of the above bottles, whether otherwise 20 untreated or whether they have the above abrasion resistance treàtment, increased the drop height at which breakage occurred to 3', the thickness of the plastic sheath or en-capsulation being .004~l.
Bottle~, either plain or having abrasion resistance treatment, when subjected to the foregoing tripotassium phos-phate ion exchange strengthening, broke at an average drop height of 4'4".
The same ion exchange s-trengthened bottles with a sub-sequent encapsulating plastic sheath of a thickness of .004 1 broke at an average drop height of 5'8".
In addition to the increase in effective strength and shock resistance of the foregoing treatment, the plastic sheath or envelope renders the containers safer in handling and transpor-tation since the plastic sheath retains the bottle contents and bottle fragments or shards in instances where the glass containers become broken.
As stated above, the foregoing treatments were applied to a large number of 12-oz. lightweight amber beer bottles. ~he term "lightweight" is used here to describe conventional non-returnable bottles which are lighter in weight than convention-al multiple trip bottles. However, the improvement in breaking strength produced by the combination of ion exchange strength-ening and plastic encapsulation of the present invention is of such degree that beverage bottles and similar glass containers may be further materially lightened in weight by manufacturing them with thinner walls;than has heretofore been practicable.
The saving thus effected in material cost offsets to a substan-tial degree the cost of the plastic employed in encapsulating the containers.
The increase in strength of bottles treated in accord-ance with the present invention as reflected in the increased drop height at which the average bottle drops as se-t forth above is highly beneficial but does not tell the full story of the importance of the combined ion exchange strengthening and plastic encapsulation which are inherent in the present inven-tion. Bottles which have been strengthened by ion exchange treatment which provides a compressive stress layer at the surface of the bottle may initially resist breakage when _g_ 1036t}Z3 1 .dropped from a given height but are very likely to become chipped and such chipping removes the compressive stress layer at the chipped area so that subsequent dropping from much lesser heights would result ink~eakage.
In addition to the advantages discussed earlier herein the plastic encapsulation prevents this type of surface chipping o the bottle and thus preserves the compressive stress layer and consequently the initial streng-thening resulting from the above ion exchange treatment. Thus the practical strength increase and resistance to breakage of the bottles are very much greater than is indicated by the above test figures.
A further advantage in treating glass containers accord-ing to the present invention, which has been briefly alluded to above, resides in the fact that when encapsulated bottles do break, despite the ion exchange strengthening which forms part of the present invention, the glass fragments or shards are retained within -the plastic capsule and generally speaking the con-tents of broken bottles are likewise retained within the encapsulating sheath.
Preferred embodiments of the present invention have been described herein to illustrate the underlying principles of the invention but it is to be understood -hat numerous modi-fications may be made without departing from the broad spirit and scope of the invention.
I' --10--
Claims (5)
1. The method of producing a strengthened soda-lime glass container comprising replacing alkali-metal ions in an exterior surface thereof with larger alkali-metal ions with the glass at an elevated temperature below the strain point thereof to produce a compression layer of glass at such surface, and subsequently forming on said surface a synthetic resin coating of a thickness of at least 0.003" up to about 0.010" to provide a protective, shock-resisting, shard-retaining encapsulating sheath for said container, said synthetic resin coating being applied with said container at an elevated temperature between approximately 300°
and 600° F.
and 600° F.
2. The method of claim 1 wherein said coating is formed by maintaining the container at an elevated temperature of approxi-mately 600° F. and spraying powdered thermoplastic synthetic resin particles upon said glass container surface by means of an electrostatic spray gun.
3. The method of claim 1 wherein said coating is formed by maintaining the container at an elevated temperature of approximately 600° F. and passing the same through a fluidized bed of synthetic resin in powdered form.
4. The method according to claim 1 wherein the synthetic resin comprises an ionomer resin.
5. The method according to claim 1 wherein the synthetic resin comprises cellulose acetate butyrate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA210,487A CA1036823A (en) | 1974-10-01 | 1974-10-01 | Method of strengthening glass containers |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA210,487A CA1036823A (en) | 1974-10-01 | 1974-10-01 | Method of strengthening glass containers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1036823A true CA1036823A (en) | 1978-08-22 |
Family
ID=4101267
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA210,487A Expired CA1036823A (en) | 1974-10-01 | 1974-10-01 | Method of strengthening glass containers |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1036823A (en) |
-
1974
- 1974-10-01 CA CA210,487A patent/CA1036823A/en not_active Expired
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