CA1179469A - Bonding of plastics materials and apparatus for use in the preparation of plastics materials for bonding - Google Patents
Bonding of plastics materials and apparatus for use in the preparation of plastics materials for bondingInfo
- Publication number
- CA1179469A CA1179469A CA000369672A CA369672A CA1179469A CA 1179469 A CA1179469 A CA 1179469A CA 000369672 A CA000369672 A CA 000369672A CA 369672 A CA369672 A CA 369672A CA 1179469 A CA1179469 A CA 1179469A
- Authority
- CA
- Canada
- Prior art keywords
- flame
- gas
- current
- produced
- burner
- 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
Links
Abstract
ABSTRACT
Pretreatment of a plastics surface by exposure to a hot blue gas flame prior to its bonding to another surface is optimized by adjusting the oxygen content of the gas flame to a value as little in excess as possible of that which produces maximum ionisation of gases within the blue zone of the gas flame. The ionisation in a flame 16 produced in a gas burner 1 results in production of an electric current which can be detected by a current collec-tor 11 and amplified by an amplifier 13.
Pretreatment of a plastics surface by exposure to a hot blue gas flame prior to its bonding to another surface is optimized by adjusting the oxygen content of the gas flame to a value as little in excess as possible of that which produces maximum ionisation of gases within the blue zone of the gas flame. The ionisation in a flame 16 produced in a gas burner 1 results in production of an electric current which can be detected by a current collec-tor 11 and amplified by an amplifier 13.
Description
~ ~'7~
I~PROVEMENTS IN OR REL~TING TO T~E BONDING
0~ PLASTICS ~T~RIALS AND APPARAT~S FOR USE
IN T~E PREPARATION OF PLASTICS ~ATERIALS
~OR BONDING
This inventio~ relates to the bonding of plastics materials a~d more particularly to the preparation of plastics materials for bonding to like or different plastics material or to non-plastics material using an adhesive.
Polypropylene can generally be bonded to itself, or even to other plastics materials or to non-plastics materiaIs, with a bond strength ~hich is adequate for many purposes using an adhesive. This bonding can gener-~lly be improved if the surfaces of the plastics materialsto be bonded are initially subjected to oxidation by exposure to a hot, blue gas flame ~or a few seconds until a dull finish is produced on the plastics materials.
However, despite such oxidative pre-treatments of the plastics surfaces to be adhesively bonded, it has not hither.bo been possible to produce a truly adequate bond capable of withstanding substaDtial stress so that plas-tics products 1ncorporating the bond can be employed for structural purposes.
According to the present invention, there is provided a method for thepre-treatment of plastics surfaces prior to bonding o~ the plastics surfaces to other surfaces by use of an adhesive, which comprises exposing the plastics surface to a hot blue gas flame, the gas flame having an .
J
9~6
I~PROVEMENTS IN OR REL~TING TO T~E BONDING
0~ PLASTICS ~T~RIALS AND APPARAT~S FOR USE
IN T~E PREPARATION OF PLASTICS ~ATERIALS
~OR BONDING
This inventio~ relates to the bonding of plastics materials a~d more particularly to the preparation of plastics materials for bonding to like or different plastics material or to non-plastics material using an adhesive.
Polypropylene can generally be bonded to itself, or even to other plastics materials or to non-plastics materiaIs, with a bond strength ~hich is adequate for many purposes using an adhesive. This bonding can gener-~lly be improved if the surfaces of the plastics materialsto be bonded are initially subjected to oxidation by exposure to a hot, blue gas flame ~or a few seconds until a dull finish is produced on the plastics materials.
However, despite such oxidative pre-treatments of the plastics surfaces to be adhesively bonded, it has not hither.bo been possible to produce a truly adequate bond capable of withstanding substaDtial stress so that plas-tics products 1ncorporating the bond can be employed for structural purposes.
According to the present invention, there is provided a method for thepre-treatment of plastics surfaces prior to bonding o~ the plastics surfaces to other surfaces by use of an adhesive, which comprises exposing the plastics surface to a hot blue gas flame, the gas flame having an .
J
9~6
2.
oxygen content as little in excess as possible of that which produces the maximum ionisation of gases within the blue zone of the gas flame whereby a dull adhesive compatible finish is produced on the surface of the plastics material, the oxygen content of the gas at which the maximum ionisation of gases within the blue zone occurs being determined by inserting into the flame a pair of electrically connected curren-t conductors having a gap therebetween, monitoring the minute current produced in the flame and setting the oxygen content of the gas flame to a value as li-ttle as possible in excess of that at which the maximum current or voltage is produced in the flame and conducted therefrom by said current conductors.
According to a second aspect of the invention, there is provided apparatus for use in the preparation of the surface of plastics material to be bonded using adhesive, which comprises a burner for producing a flame for rendering dull the surface of a plastics article to be bonded, the burner having gas inlet means~ gas outlet means, current collector means for posi-tioning within the flame produced by the burner, an amplifier for amplifying the current or voltage produced as a result of ionisation within the flame and means for reading or recording the current or voltage thereby produced.
The method of this irventio-n is particularly ~ell suited to the pre-treatment of polypropyIene surfaces'to be bonded to like or different plas~ics materials. Nevertheless, the method is generally applicable'to: the bonding of piastics materials which benefit from subjecting to surface oxidation and hence dulling before undergoing bonding. The method of the invention has been foun'd to give good results when applied to the pre-treatment of fluorine-containing polymers such as polytetrafluo~thylene, polycarbonates, silicon resins, and melamine-formaldehyde resins. In the case of the last identified plastics,it has been found that the method of the invention places them in a condition in which they can be bonded by means of cyanoacrylate resins which it has not hitherto been possible to employ with such plastics.
In addition to preparing plastics materials for plastics-bonding, plastics materials pre'-trea-ted by the method of the invention may be bonded to 'other materials such as properly degreased me~tals usïng, for example, such silicon adhesives as Silcoset 152 and 153 and Dow Corning RTV
adhesives. Bonding'to brickwork can be achieved using silicon~based sealing compounds which are currently avail-able in the building trade.
When carrying out the method of'the invention, the extent of exposure of a plastics surface'to the blue zone of a flame will depend upon'the particular material being treated and will need to be determined by trial for each particular material. Whilst'the best test of the success of the pre-treatment will lie in sophisticated methods of struckural testing, in pra'ctice,'in fact,'the quality of '30 preparation can generally be evaluated by viewing the appearance of the trea~ed area'~ see`that it has a high degree of dullness and by carrying out simple wetting tests.
In general, it has been foun'd'that'the method of this invention ~produces particularly good results when an . .
organosilicon adhesive which cur'es''to a resilient mass is produced from the adhesive. ' The ionisation which occurs'in'the blue oxidising zone .. . .... ..
- of the treatment flame can'convenien-tly-be determined by ~ k s 4~9 electronic amplification of the minute current produced in the flame when a suitable heat resistant gauze or even a pair of electrically connected wires with a gap therebetween is inserted into the flame to produce a current of the order usually of a few nano amps but which may amount to a few micro amps, depending on the current collector used. Insofar as a gauze may be used, the word "gau~e" is used herein to denote any electric-ally conductive and usually metal structure which ~ever-theless possesses a large open surface area to allow theflame to penetrate therethrough to act on the plastics material being treated. Thus, although gauzes in the conventional sense may be employed, it is also possible to employ perforated or expanded metal sheet structures.
~or a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example only, to the accompany-ing drawings, in which:-~igure 1 in an elevation, partly in section of a burner embodying this invention; and ~ igure 2 is a transverse cross-section through Figure 1 at A-A.
Referring to the drawings, a burner embodying this invention comprises an angled meta:L, for example copper, tube 1 h~ving an inlet tube 2 for gas and air passing through one end thereof and being closed at the opposite end 3. The inlet tube 2 is closed at its inner end and formed with a plurality of circumferentially disposed outlets 4 thereby ensuring an even distribution of combus-tion mixture within the tube 1 and helping to ensure thatan even distribution of combustion mixlure within the tube 1 and helping to ensure that an even fiame height is achieved. Be~-ond an angle 5 provided in the tube 1, the tube 1 is surrounded by a copper tube 6. Over a portion o~ its length and width at which it is covered by the copper tube 6, the inner tube 1 is formed with an opening 7 which is matched by an opening 10 in the copper tube 6 ~7~9 . 5 and over which double thickness openin~ is la;id a stain-less steel ~ine mesh gæuze 8. The gauze is held iD
position by an outer tube 9 around the cop~er tube 6 aDd pre~erablY made of aluminium the high thermal conduc~ g of which prevents the setting up of excessive temperature along the edge o~ the flame. As can be seen from ~igure 2, the opening 7 in the inner tube 6.is narrower tha~ the corresponding opening lO in *he copper tube 6.
Spæc.ed aPart ~rom the gau2e 8 is a suitable supported lG met~ gauze 11 ~ ch will g~nerally be much~oarser than the gauze 8 ?nd from which exte~d~ a lead l, to 2 current amplifier 13 fitted with a microammeter 14. ~ne amplifier 13 is additionælly connected through a lead 15 to the copper Lube 1.
i~ U7hen the gas burner is in use, ~ 7'~ture of gas and ~ir is ~ed into the angled copper tube l through the inlet lube 2 and outlets 4. As it emerges from the an~led copper tube through the openings 7 and lO and is ignited, æ flame 16 whose configuration is shown be~ter ~C~ iD Figure 2 is produced. This elongate flame is pla~ed.
over the sur~ace of a sheet of plas~ics material which is to undergo.adhesive bonding to achieve dulling of tne surface. The metal gauze lO is posi*ioned in the flame produced, preferably in the blue p~rt thereof, and ionisa-2~ tion which *akes place i~ the flame and whi~h is at a ma~imNm in the b.lue.part thereof is conducted *o the -amplifier 13 ~nd.~h~.:amplifier current thereby pro~uced is re-ad o~f by means of the micro~mmeter 14. In ~ccord-`ance with this inventioD, cont~ol of the flame is e~fec+ed ~C uDtil, for a particular combination of gas for exam?le ~ropane or butane, and oxidising gas, generall~- air or ox~gen, ionisation is at a maximum and hence optimum pre-treatment of the plastics materi~l is obtained.
A machine may be constrllcted for the flame trea.men~
of zones along the edges of sheet plastics material, for example sheet pol~7prop~7lene~ according to this inventioD.
~or this purpose, two of the burners shown iD the accompan~-~ ~ ~t7~
.. . 6 ing drawings may be disposed on a carriage having areversible drive mechanism to carry them at a substantially uniform rate along the edge to be treated. When the carriage is in its normal rest position, the burner flames play upon the respective ion collector gauzes and the minute current generated is electronically amplified as ~forementioned to enable the optimum flame conditions to be established prior to setting the carriage in motion to effect pre-treatment of the sheet plastics material.
10~lthough reference has been made herein in connection with the drawings to the detection of a current as such, since a voltage is concomitantly set up~ it is equally . possible to use a voltage amplifier and a voltmeter to eslablish when maximum ionisation of gases takes place in 1~ the flame and set the o~ygen content of the combustible gases accordingly.
oxygen content as little in excess as possible of that which produces the maximum ionisation of gases within the blue zone of the gas flame whereby a dull adhesive compatible finish is produced on the surface of the plastics material, the oxygen content of the gas at which the maximum ionisation of gases within the blue zone occurs being determined by inserting into the flame a pair of electrically connected curren-t conductors having a gap therebetween, monitoring the minute current produced in the flame and setting the oxygen content of the gas flame to a value as li-ttle as possible in excess of that at which the maximum current or voltage is produced in the flame and conducted therefrom by said current conductors.
According to a second aspect of the invention, there is provided apparatus for use in the preparation of the surface of plastics material to be bonded using adhesive, which comprises a burner for producing a flame for rendering dull the surface of a plastics article to be bonded, the burner having gas inlet means~ gas outlet means, current collector means for posi-tioning within the flame produced by the burner, an amplifier for amplifying the current or voltage produced as a result of ionisation within the flame and means for reading or recording the current or voltage thereby produced.
The method of this irventio-n is particularly ~ell suited to the pre-treatment of polypropyIene surfaces'to be bonded to like or different plas~ics materials. Nevertheless, the method is generally applicable'to: the bonding of piastics materials which benefit from subjecting to surface oxidation and hence dulling before undergoing bonding. The method of the invention has been foun'd to give good results when applied to the pre-treatment of fluorine-containing polymers such as polytetrafluo~thylene, polycarbonates, silicon resins, and melamine-formaldehyde resins. In the case of the last identified plastics,it has been found that the method of the invention places them in a condition in which they can be bonded by means of cyanoacrylate resins which it has not hitherto been possible to employ with such plastics.
In addition to preparing plastics materials for plastics-bonding, plastics materials pre'-trea-ted by the method of the invention may be bonded to 'other materials such as properly degreased me~tals usïng, for example, such silicon adhesives as Silcoset 152 and 153 and Dow Corning RTV
adhesives. Bonding'to brickwork can be achieved using silicon~based sealing compounds which are currently avail-able in the building trade.
When carrying out the method of'the invention, the extent of exposure of a plastics surface'to the blue zone of a flame will depend upon'the particular material being treated and will need to be determined by trial for each particular material. Whilst'the best test of the success of the pre-treatment will lie in sophisticated methods of struckural testing, in pra'ctice,'in fact,'the quality of '30 preparation can generally be evaluated by viewing the appearance of the trea~ed area'~ see`that it has a high degree of dullness and by carrying out simple wetting tests.
In general, it has been foun'd'that'the method of this invention ~produces particularly good results when an . .
organosilicon adhesive which cur'es''to a resilient mass is produced from the adhesive. ' The ionisation which occurs'in'the blue oxidising zone .. . .... ..
- of the treatment flame can'convenien-tly-be determined by ~ k s 4~9 electronic amplification of the minute current produced in the flame when a suitable heat resistant gauze or even a pair of electrically connected wires with a gap therebetween is inserted into the flame to produce a current of the order usually of a few nano amps but which may amount to a few micro amps, depending on the current collector used. Insofar as a gauze may be used, the word "gau~e" is used herein to denote any electric-ally conductive and usually metal structure which ~ever-theless possesses a large open surface area to allow theflame to penetrate therethrough to act on the plastics material being treated. Thus, although gauzes in the conventional sense may be employed, it is also possible to employ perforated or expanded metal sheet structures.
~or a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example only, to the accompany-ing drawings, in which:-~igure 1 in an elevation, partly in section of a burner embodying this invention; and ~ igure 2 is a transverse cross-section through Figure 1 at A-A.
Referring to the drawings, a burner embodying this invention comprises an angled meta:L, for example copper, tube 1 h~ving an inlet tube 2 for gas and air passing through one end thereof and being closed at the opposite end 3. The inlet tube 2 is closed at its inner end and formed with a plurality of circumferentially disposed outlets 4 thereby ensuring an even distribution of combus-tion mixture within the tube 1 and helping to ensure thatan even distribution of combustion mixlure within the tube 1 and helping to ensure that an even fiame height is achieved. Be~-ond an angle 5 provided in the tube 1, the tube 1 is surrounded by a copper tube 6. Over a portion o~ its length and width at which it is covered by the copper tube 6, the inner tube 1 is formed with an opening 7 which is matched by an opening 10 in the copper tube 6 ~7~9 . 5 and over which double thickness openin~ is la;id a stain-less steel ~ine mesh gæuze 8. The gauze is held iD
position by an outer tube 9 around the cop~er tube 6 aDd pre~erablY made of aluminium the high thermal conduc~ g of which prevents the setting up of excessive temperature along the edge o~ the flame. As can be seen from ~igure 2, the opening 7 in the inner tube 6.is narrower tha~ the corresponding opening lO in *he copper tube 6.
Spæc.ed aPart ~rom the gau2e 8 is a suitable supported lG met~ gauze 11 ~ ch will g~nerally be much~oarser than the gauze 8 ?nd from which exte~d~ a lead l, to 2 current amplifier 13 fitted with a microammeter 14. ~ne amplifier 13 is additionælly connected through a lead 15 to the copper Lube 1.
i~ U7hen the gas burner is in use, ~ 7'~ture of gas and ~ir is ~ed into the angled copper tube l through the inlet lube 2 and outlets 4. As it emerges from the an~led copper tube through the openings 7 and lO and is ignited, æ flame 16 whose configuration is shown be~ter ~C~ iD Figure 2 is produced. This elongate flame is pla~ed.
over the sur~ace of a sheet of plas~ics material which is to undergo.adhesive bonding to achieve dulling of tne surface. The metal gauze lO is posi*ioned in the flame produced, preferably in the blue p~rt thereof, and ionisa-2~ tion which *akes place i~ the flame and whi~h is at a ma~imNm in the b.lue.part thereof is conducted *o the -amplifier 13 ~nd.~h~.:amplifier current thereby pro~uced is re-ad o~f by means of the micro~mmeter 14. In ~ccord-`ance with this inventioD, cont~ol of the flame is e~fec+ed ~C uDtil, for a particular combination of gas for exam?le ~ropane or butane, and oxidising gas, generall~- air or ox~gen, ionisation is at a maximum and hence optimum pre-treatment of the plastics materi~l is obtained.
A machine may be constrllcted for the flame trea.men~
of zones along the edges of sheet plastics material, for example sheet pol~7prop~7lene~ according to this inventioD.
~or this purpose, two of the burners shown iD the accompan~-~ ~ ~t7~
.. . 6 ing drawings may be disposed on a carriage having areversible drive mechanism to carry them at a substantially uniform rate along the edge to be treated. When the carriage is in its normal rest position, the burner flames play upon the respective ion collector gauzes and the minute current generated is electronically amplified as ~forementioned to enable the optimum flame conditions to be established prior to setting the carriage in motion to effect pre-treatment of the sheet plastics material.
10~lthough reference has been made herein in connection with the drawings to the detection of a current as such, since a voltage is concomitantly set up~ it is equally . possible to use a voltage amplifier and a voltmeter to eslablish when maximum ionisation of gases takes place in 1~ the flame and set the o~ygen content of the combustible gases accordingly.
Claims (14)
1. A method for the pretreatment of a plastics surface prior to bonding of the plastics surface to another surface by use of an adhesive, which comprises exposing the plastics surface to a hot blue gas flame having an oxygen content as little in excess as possible of that which produces the maximum ionisation of gases within the blue zone of the gas flame whereby a dull adhesive compatible finish is produced on the surface of the plastics material, the oxygen content of the gas at which the maximum ionisation of gases within -the blue zone occurs being determined by inserting into the flame a pair of electrically connected current conductors having a gap therebetween, monitoring the minute current produced in the flame and setting the oxygen content of the gas flame to a value as little as possible in excess of that at which the maximum current or voltage is produced in the flame and conducted therefrom by said current conductors.
2. A method as claimed in claim 1, wherein said current conductors form part of a heat resistant metal gauze inserted into the flame.
3. A method as claimed in claim 1, wherein, in order to determine the oxygen content of the gas at which the maximum ionisation of gases within the blue zone occurs, the gases undergo combustion in an elongate burner having gas inlet means for a combustible gas and for an oxidising gas and gas outlet means, said pair of electrically connected current conductors being positioned in relation to the gas outlet means so as to lie within a flame produced in the burner, and means for reading or recording the current or voltage produced within the flame.
4. A method as claimed in claim 3, wherein the position of said inlet means is at one end of the elongate burner, the opposite end of which is closed, the gas outlet means being constituted by an elongate slot in a lateral wall surface of the burner.
5. A method for the pretreatment of a plastics surface prior to bonding of the plastics surface to another surface by use of an adhesive, which comprises exposing the plastics surface to a hot blue gas flame, the gas flame having an oxygen content as little as possible in excess of that which produces the maximum ionisation of gases within the blue zone of the gas flame whereby a dull adhesive compatible finish is produced on the surface of the plastics material, the oxygen content of the gas at which maximum ionisation of gases within the blue zone occurs being determined by inserting a pair of electrically connected current conductors with a gap therebetween into the flame, monitoring the minute current produced in the flame, usually with electronic amplification, and setting the oxygen content of the gas flame to a value as little as possible in excess of that at which the maximum current or voltage is produced in the flame and conducted therefrom by said current conductors, which current conductors form part of a heat resistant metal gauze inserted into the flame.
6. A method as claimed in claim 5, which is applied to the pretreatment of a polypropylene surface.
7. A method as claimed in claim 6, wherein, in order to determine the oxygen content of the gas at which the maximum ionisation of gases within the blue zone occurs, the gases undergo combustion in an elongate burner having gas inlet means for a combustible gas and for an oxidising gas and gas outlet means, said pair of electrically connected current conductors being positioned in relation to the gas outlet means so as to lie within a flame produced in the burner, and means for reading or recording the current or voltage produced within the flame.
8. A method as claimed in claim 7, wherein the position of said inlet means is at one end of the elongate burner, the opposite end of which is closed, the gas outlet means being constituted by an elongate slot in a lateral wall surface of the burner.
9. A method as claimed in claim 8, wherein the elongate burner is reinforced in the region of said gas outlet means by means of a metal sleeve tube fitted thereover and having an elongate slot aligned with said elongate slot.
10. A method as claimed in claim 1, wherein the said current conductors are positioned in the blue part of the flame.
11. A method as claimed in claim 5, wherein the said current conductors are positioned in the blue part of the gas flame.
12. Apparatus for use in the generation of an electric current, which comprises a gas-fuelled burner for producing a flame, current collector means for positioning in the flame produced by the burner, an amplifier for amplifying the current or voltage produced as a result of ionisation within the flame and means for reading or recording the current or voltage thereby produced.
13. Apparatus as claimed in claim 12, wherein said current collector means is a heat resistant metal gauze.
14. A method as claimed in claim 5, wherein, in a subsequent working step, the plastic surface which has been pretreated is bonded to another surface by means of an organosilicon adhesive.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000369672A CA1179469A (en) | 1981-01-29 | 1981-01-29 | Bonding of plastics materials and apparatus for use in the preparation of plastics materials for bonding |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000369672A CA1179469A (en) | 1981-01-29 | 1981-01-29 | Bonding of plastics materials and apparatus for use in the preparation of plastics materials for bonding |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1179469A true CA1179469A (en) | 1984-12-18 |
Family
ID=4119032
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000369672A Expired CA1179469A (en) | 1981-01-29 | 1981-01-29 | Bonding of plastics materials and apparatus for use in the preparation of plastics materials for bonding |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1179469A (en) |
-
1981
- 1981-01-29 CA CA000369672A patent/CA1179469A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |