CA1078120A - Process for reconstructing a worn tyre through the direct application to the carcass of the tyre of a premoulded tread - Google Patents
Process for reconstructing a worn tyre through the direct application to the carcass of the tyre of a premoulded treadInfo
- Publication number
- CA1078120A CA1078120A CA242,972A CA242972A CA1078120A CA 1078120 A CA1078120 A CA 1078120A CA 242972 A CA242972 A CA 242972A CA 1078120 A CA1078120 A CA 1078120A
- Authority
- CA
- Canada
- Prior art keywords
- tread
- sheet
- carcass
- adhesive material
- tyre
- 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
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D30/00—Producing pneumatic or solid tyres or parts thereof
- B29D30/06—Pneumatic tyres or parts thereof (e.g. produced by casting, moulding, compression moulding, injection moulding, centrifugal casting)
- B29D30/52—Unvulcanised treads, e.g. on used tyres; Retreading
- B29D30/54—Retreading
- B29D30/56—Retreading with prevulcanised tread
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Tyre Moulding (AREA)
- Heating, Cooling, Or Curing Plastics Or The Like In General (AREA)
- Lining Or Joining Of Plastics Or The Like (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides a process for retreading a worn tyre by the direct application to the carcass of the tyre of a premoulded tread. In the process a sheet of adhesive mater-ial is prepared which anchors the tread to the carcass of the tyre.
The sheet is prepared from an admixture comprising, at least one non-vulcanized bonding material, at least one vulcanization accelerator, at least one vulcanizing agent, a high percentage in weight of co-vulcanizing resins, and an agent for the prevention of scorching. The sheet of adhesive material is bonded to the inner surface of the tread by means of rolling and simultaneously with the rolling air trapped between the tread and the sheet of adhesive material is expelled via the perforations formed in the said sheet of adhesive material. The assembly of premoulded tread is applied to the rolling surface of the carcass with the sheet forming an intermediate layer. The assembly and carcass are then enshrouded by a casing in a gas-tight manner and put in a vulcanization oven where vulcanization is effected.
The present invention provides a process for retreading a worn tyre by the direct application to the carcass of the tyre of a premoulded tread. In the process a sheet of adhesive mater-ial is prepared which anchors the tread to the carcass of the tyre.
The sheet is prepared from an admixture comprising, at least one non-vulcanized bonding material, at least one vulcanization accelerator, at least one vulcanizing agent, a high percentage in weight of co-vulcanizing resins, and an agent for the prevention of scorching. The sheet of adhesive material is bonded to the inner surface of the tread by means of rolling and simultaneously with the rolling air trapped between the tread and the sheet of adhesive material is expelled via the perforations formed in the said sheet of adhesive material. The assembly of premoulded tread is applied to the rolling surface of the carcass with the sheet forming an intermediate layer. The assembly and carcass are then enshrouded by a casing in a gas-tight manner and put in a vulcanization oven where vulcanization is effected.
Description
.2~
The present invention relates to a process for retread-ing a worn tyre by the direct application of a premoulded tread to the carcass of t~e tyre.
Conventional processes for retreading worn tyres may be divided into two groups: namely a) Elot processes b) ~ow temperature processes.
In the hot process, the not ye-t vulcan:ized t~ead is applied to a p~eviously rasped carcass. ~lhe assembly of the carcass and the tread is placed inside a special mould and then, with heat provided by steaml hot gas or hot air, the vulcanization reaction is effected at high temperatures. Whilst vulcanlzation is taking place, the design of the tread is also formed and this naturally depends on the shape of the mould.
Such hot processes have various disadvantages. In particular such disadvantages include fast ageing of the finished product because of the high temperatures involved and high plant costs due;to the large number of moulds needed to have a sufficiently flexible production.
While in other hot processes, theaforesaid technology continues to be used, the use of a prevulcanized tread in retreading tyres has been proposed.
This makes it possible to in part, avoid the problem of moulds. However it introduces another substantial difficulty, namely double vulcanization which substantially reduces the mechanical characteristics of the tyre.
In the conventional low temperature processes the tread is applied to the carcass of the tyre to be retreaded, using an intermediate strip of adhesive material. The adhesive strip, having a natural rubber base and containing, inter alia, an accel-erator and a vulcanizing agent, is maintained at a low temperature,protected by a special casing in order to prevent undesired prevulcanization and only when it is to be used may the said . .
~7~
strip be applied to the ~read.
Other low temperature processesUsed, instead of a single strip of adhesive material, two separate strips, again wi-th a rubber base, one of which contains the accelerator and the other, the vulcanizing agent. These particular strips also have to be kept carefully isolated until the time they arè to be used so as to prevent undesired reactions. Durin~ the vulcaniza-tion phase the complete assembly is enclosed in a protective casing which is suitably taut so that it is tightly up ayainst the surface of the tread and the sidewalls of the tyre. The casing is provided with a valve to externally relieve the air trapped between it and the tyre during the fitting of the casing.
This prevents oxidation during the vulcanization or alternations from taking place in the chemical-physical characteristics of the material which is subsequently vulcanized.
The application of t~e strips of adhesive material and of the tread to the carcass of the tyre is carried out through rolling operations performed which favour lateral expulsion of the air trapped between the carcass, the strips o~ adhesive mat-erial and the tread during the application. In particular, theconventional procedure is to effect the rolling operation with a reciprocating motion in a direction diagonal to the surface of the tread at the same time that the tyre is being rotated.
The cold processesl which are widely used, however have various disadvantages. In particular the strips of adhesive material are likely to slide outside the area in which the ;-tread has to be applied and it is di~ficult to get the final thickness of the strips of adhesive material to be uni~orm because, ~-due to the aforesaid tendency to slide the material accumulates in some places, whilst in others it is in short supply and can even be insuf~icient. Due to the a~orementioned disadvantages, the bond between the tread and the carcass is irregular and areas - -~0'71~
are formed which become unstuck and these considerably shortenthe life of the retreaded tyre.
A further disad~antage, of significant importance, is the air which, during the vulcanization is encapsulated between the protective casing and the tread since, despite the care with which the protective casing is put into position and the techni-cal expedients used, it is not possible to eliminate fully the presence of air inside the said casing and thus a cerkain quantity of air, though oE minimal volume, is always trapped in the interstices of the surface of the tread. r~his notably reduces the heat transmission coefficient, thereby inhibiting proper vulcanizing reticulation. Furthermore, in all the aforesaid low temperature processes, -the strips of adhesive material between the tread and the carcass, whether consisting of one or more layers, have to be kept away from the tread and separate ~rom each another under special ambient conditions, duly protected by a special casing in order to prevent prevulcanization which greatly reduces their adhesi~e properties. Only at the time they are to be used can the strips be applied to the tread or to the carcass of the tyre and this renders the task of the operator extremely long and arduous.
- The present invention pro~ides a process for retreading a worn tyre which is not subject to the aforesaid disadvantages and which comprises the direct application to the carcass of the tyre of a single assemhly comprising a premoulded tread and a strip or sheet of adhesive material, with which assembly the sheet of adhesive material may be prepared and applied to the ;
tread when the tread is being formed, without any danger of pre w lcani2ation, the application of the sheet to the tread is effected without any undesiredsliding occurring and with the optimum certainty of an absence o~ air between the tread and the sheet, and there being essentially no air between the protective c~sin~ a~d the tyre during the vulcanization.
According to the present invention in the low tempera-ture process, the sheet of adhesive material with which to anchor the tread to the carcass of the tyre is prepared from an admixture comprising at least one non-vulcanized bonding material, at least one vulcanization accelerator at least one vulcanizing agent, a relatively high percentage in weight of co-vulcanizing resins, that is about 7.6 to 8.2~ by weight oE the total composition, and an agent for the prevention of scorching, capable o~ vulcanizing the non-vulcanized bondin~ mater.ial at a temperature around 100C
and to stabilize ~he reagents and thus prevent commencement of the vulcanization, up to temperatures of bet.ween 35C and 40C
inclusive, and the sheet of adhesive material is bonded to the inner surface of the tread by rolling and simultaneous perfora-tion of the said sheet so as to expel air trapped between the tread and the sheet of adhesive material, via the perforations in the said sheet of adhesive material.
According to the present invention there~ore there is provided a process for retreading a worn tyre comprising a carcass having side walls and a rolling surface which process comprises providing a pre-moulded tread, preparing a sheet of adhesive material from an admixture comprising at least one vulcanizable ; bonding material, at least one vulcanization accelerator, at least one vulcanizing agent, a high weight percentage of co-vulcanizing resins, and an anti-scorching agent capable of preventing vulca-nization of said sheet at a temperature up to 40C, said sheet being vulcanizable at temperatures of about 100C, forming an assembly by bonding said sheet to an inner surface of said tread by means of rolling during which said sheet is perforated to cause expulsion of air trapped between the tread and the sheet through said perforations, applying the assembly to the carcass with:the adhesive sheet forming an intermediate layer between the tread and the rolling surface of ~ 4 ~
.: . - . . : , . . - . - . ~ :. ~
the carcass enclosing the assembly and carcass with a protective casing which extends around the tread and the side walls in an air-tight manner, and inserting the enclosed assembly and carcass in a vulcanization oven to effect vulcanization.
The present invention will be further illustrated by way of the accompanying drawings :in which:
Fig. 1 is a block flow diagram of the stages in the process for retreading a ~yre accordin~ to one embodiment of the present invention;
Fig. 2 is a schematic side view showing how the assembly of the premoulded tread and the sheet of adhesive material is achieved in the process o~ Fig. l;
Fig. 3 shows a cross sectional view of an assembly of the tread, the sheet of adhesive material, the carcass of the tyre and the protective casing mounted on a supporting rim in the process of Fig. l; and Fig. 4 is a schematic side elevation of the assembly of Fig. 3 in a vulcanizing oven.
The tread 1 is produced in accordance with conventional techniques, preferably giving it a particular section as shown in Fig. 3. In particular the tread 1 is provided with an inner surface la which as will be seen hereinafter, match the rolling surface of the carcass of the tyre 2. The inner surface la is suitably arcuate and has a radius to allow the single assembly constituted by the tread and the sheet of adhesive material to bond perfectly to the pre-treated rolling surface of the carcass
The present invention relates to a process for retread-ing a worn tyre by the direct application of a premoulded tread to the carcass of t~e tyre.
Conventional processes for retreading worn tyres may be divided into two groups: namely a) Elot processes b) ~ow temperature processes.
In the hot process, the not ye-t vulcan:ized t~ead is applied to a p~eviously rasped carcass. ~lhe assembly of the carcass and the tread is placed inside a special mould and then, with heat provided by steaml hot gas or hot air, the vulcanization reaction is effected at high temperatures. Whilst vulcanlzation is taking place, the design of the tread is also formed and this naturally depends on the shape of the mould.
Such hot processes have various disadvantages. In particular such disadvantages include fast ageing of the finished product because of the high temperatures involved and high plant costs due;to the large number of moulds needed to have a sufficiently flexible production.
While in other hot processes, theaforesaid technology continues to be used, the use of a prevulcanized tread in retreading tyres has been proposed.
This makes it possible to in part, avoid the problem of moulds. However it introduces another substantial difficulty, namely double vulcanization which substantially reduces the mechanical characteristics of the tyre.
In the conventional low temperature processes the tread is applied to the carcass of the tyre to be retreaded, using an intermediate strip of adhesive material. The adhesive strip, having a natural rubber base and containing, inter alia, an accel-erator and a vulcanizing agent, is maintained at a low temperature,protected by a special casing in order to prevent undesired prevulcanization and only when it is to be used may the said . .
~7~
strip be applied to the ~read.
Other low temperature processesUsed, instead of a single strip of adhesive material, two separate strips, again wi-th a rubber base, one of which contains the accelerator and the other, the vulcanizing agent. These particular strips also have to be kept carefully isolated until the time they arè to be used so as to prevent undesired reactions. Durin~ the vulcaniza-tion phase the complete assembly is enclosed in a protective casing which is suitably taut so that it is tightly up ayainst the surface of the tread and the sidewalls of the tyre. The casing is provided with a valve to externally relieve the air trapped between it and the tyre during the fitting of the casing.
This prevents oxidation during the vulcanization or alternations from taking place in the chemical-physical characteristics of the material which is subsequently vulcanized.
The application of t~e strips of adhesive material and of the tread to the carcass of the tyre is carried out through rolling operations performed which favour lateral expulsion of the air trapped between the carcass, the strips o~ adhesive mat-erial and the tread during the application. In particular, theconventional procedure is to effect the rolling operation with a reciprocating motion in a direction diagonal to the surface of the tread at the same time that the tyre is being rotated.
The cold processesl which are widely used, however have various disadvantages. In particular the strips of adhesive material are likely to slide outside the area in which the ;-tread has to be applied and it is di~ficult to get the final thickness of the strips of adhesive material to be uni~orm because, ~-due to the aforesaid tendency to slide the material accumulates in some places, whilst in others it is in short supply and can even be insuf~icient. Due to the a~orementioned disadvantages, the bond between the tread and the carcass is irregular and areas - -~0'71~
are formed which become unstuck and these considerably shortenthe life of the retreaded tyre.
A further disad~antage, of significant importance, is the air which, during the vulcanization is encapsulated between the protective casing and the tread since, despite the care with which the protective casing is put into position and the techni-cal expedients used, it is not possible to eliminate fully the presence of air inside the said casing and thus a cerkain quantity of air, though oE minimal volume, is always trapped in the interstices of the surface of the tread. r~his notably reduces the heat transmission coefficient, thereby inhibiting proper vulcanizing reticulation. Furthermore, in all the aforesaid low temperature processes, -the strips of adhesive material between the tread and the carcass, whether consisting of one or more layers, have to be kept away from the tread and separate ~rom each another under special ambient conditions, duly protected by a special casing in order to prevent prevulcanization which greatly reduces their adhesi~e properties. Only at the time they are to be used can the strips be applied to the tread or to the carcass of the tyre and this renders the task of the operator extremely long and arduous.
- The present invention pro~ides a process for retreading a worn tyre which is not subject to the aforesaid disadvantages and which comprises the direct application to the carcass of the tyre of a single assemhly comprising a premoulded tread and a strip or sheet of adhesive material, with which assembly the sheet of adhesive material may be prepared and applied to the ;
tread when the tread is being formed, without any danger of pre w lcani2ation, the application of the sheet to the tread is effected without any undesiredsliding occurring and with the optimum certainty of an absence o~ air between the tread and the sheet, and there being essentially no air between the protective c~sin~ a~d the tyre during the vulcanization.
According to the present invention in the low tempera-ture process, the sheet of adhesive material with which to anchor the tread to the carcass of the tyre is prepared from an admixture comprising at least one non-vulcanized bonding material, at least one vulcanization accelerator at least one vulcanizing agent, a relatively high percentage in weight of co-vulcanizing resins, that is about 7.6 to 8.2~ by weight oE the total composition, and an agent for the prevention of scorching, capable o~ vulcanizing the non-vulcanized bondin~ mater.ial at a temperature around 100C
and to stabilize ~he reagents and thus prevent commencement of the vulcanization, up to temperatures of bet.ween 35C and 40C
inclusive, and the sheet of adhesive material is bonded to the inner surface of the tread by rolling and simultaneous perfora-tion of the said sheet so as to expel air trapped between the tread and the sheet of adhesive material, via the perforations in the said sheet of adhesive material.
According to the present invention there~ore there is provided a process for retreading a worn tyre comprising a carcass having side walls and a rolling surface which process comprises providing a pre-moulded tread, preparing a sheet of adhesive material from an admixture comprising at least one vulcanizable ; bonding material, at least one vulcanization accelerator, at least one vulcanizing agent, a high weight percentage of co-vulcanizing resins, and an anti-scorching agent capable of preventing vulca-nization of said sheet at a temperature up to 40C, said sheet being vulcanizable at temperatures of about 100C, forming an assembly by bonding said sheet to an inner surface of said tread by means of rolling during which said sheet is perforated to cause expulsion of air trapped between the tread and the sheet through said perforations, applying the assembly to the carcass with:the adhesive sheet forming an intermediate layer between the tread and the rolling surface of ~ 4 ~
.: . - . . : , . . - . - . ~ :. ~
the carcass enclosing the assembly and carcass with a protective casing which extends around the tread and the side walls in an air-tight manner, and inserting the enclosed assembly and carcass in a vulcanization oven to effect vulcanization.
The present invention will be further illustrated by way of the accompanying drawings :in which:
Fig. 1 is a block flow diagram of the stages in the process for retreading a ~yre accordin~ to one embodiment of the present invention;
Fig. 2 is a schematic side view showing how the assembly of the premoulded tread and the sheet of adhesive material is achieved in the process o~ Fig. l;
Fig. 3 shows a cross sectional view of an assembly of the tread, the sheet of adhesive material, the carcass of the tyre and the protective casing mounted on a supporting rim in the process of Fig. l; and Fig. 4 is a schematic side elevation of the assembly of Fig. 3 in a vulcanizing oven.
The tread 1 is produced in accordance with conventional techniques, preferably giving it a particular section as shown in Fig. 3. In particular the tread 1 is provided with an inner surface la which as will be seen hereinafter, match the rolling surface of the carcass of the tyre 2. The inner surface la is suitably arcuate and has a radius to allow the single assembly constituted by the tread and the sheet of adhesive material to bond perfectly to the pre-treated rolling surface of the carcass
2 of the tyre.
The preparation of the rolling surface of the carcass 2 of the tyre involves rasping operations with which all residual parts of the tread to be reformed are removed from the carcass of the tyre 2. The rasping operation is par~icularly intense adjacent the sidewalls of the carcass 2 of the tyre an~ at the -~ . . . . .. . . .
- 1~713~
conclusion of these rasping operations, the rolling surface 2a is arcuate, substantially as shown in Fig. 3, with a radius of curvature R.
The radius R is considered when forming the tread 1 so that the inner surface la of -the tread is arcuate with a radius of curvature Rl identical to the radius I~. The surfaces la o~
the tread 1 and 2a of the carcass 2 of the tyre are thus on the same planes and match each other.
This operating stage avoids the substantial problem which is experienced when preparing the tread.and the carcass of : :
the tyre on the basis of conventional c~rtain techniques, whereby the tread is provided with a perfectly flat inner surface and the adhesive material is built up in the areas close to the sidewalls .
of the carcass of the tyre, so as to bring the rolling surface into the right condition to receive the tread.
The process according to the invention requires the preparation of a sheet of adhesive material 3 to be applied to -`
the tread at the time it is being formed, so that the single assembly of the tread and the sheet of adhesive material can ~:
subsequently be stored without the risk of any kind of reaction occurring. These characteristics are obtained by dosing reagents : . :
which allow the sheet of adhesive material to be produced with /.. ~:.
a high percentage of co-vulcanizing resins and also by a suitable percentage of an anti-scorching agent which prevents the previously . ~.:
mentioned undesired reactions from taking place. The reagents :
used in the production of the sheet of adhesive materialmay varyboth qualitatively and quantitatively depending upon the composition ~
of the tread. By way of an example, the composition by weight is . -- given below of the reagents for producing a standard sheet of :. -adhesiye material suitable for most of the tyres currently on . .::
the market: .
"' .
~(~'7~
COMPONE:NTS P RTS IN WEIGHT
Natural rubber or polyisoprene 100 zinc oxide 5-10 Stearic acid 0.5-1.2 Anti-oxidant (Poly 2-3-4 trimethyl dihydroquinaldine) Anti-ozonant (N-phenyl - N - cyclohexyl para 1-2 phenylendiamine) Pine tar 5-10 Co-vulcanizing resins (Polyhalethyl phenol) 15 Adhesive agents (liquid coumarone/indene resin) 10 suna weld (Polymer 780) 10 Insoluble.. Sulphur 3~5 Accelerators (diphenyl guanadine and 1-3 mercaptobenzothiazole) High structure carbon black 30 Anti-scorching agent (supplied under the trademark 0,05 Santocard PVI) The high percentage of co-vulcanizing resins produces a stabiliæed product which retains indefinitely its adhesive properties. If the lower figure of the ranges is taken, the percentage by weight of the co-vulcanizing resins is 8.2~ and7 if the higher figure is taken the percenta~e by weight of co-vulcanizing resins is 7.6%.
The addition of a suitable percentage of an agent for the prevention of scorching prevents undesired prevulcanization and makes it possible for the sheet of adhesive material 3 to be -applied to the tread 1 and the properties of the assembly of the ; tread and the sheet of adhesive material to remain unchanged. ~ .
The sheet 3 produced in accordance with the composi-tion given above and subjected to "Monsanto" rheometric:tests, using a sample vulcaniæed at 100C, gave the following physical characteristics as a function of time: :
, ' , .
~- 7 - : ~
I .~, ~ ' ~7~
2h 3h 4h Modulus at 300~ 63 64 85 Tensile stress 238 237 235 Ultimate elongation 640 610 560 Shore Test A 46 49 53 ~
. :-- 7a -. .
' ~ ~7t~Z~
The stages for the produc~ion o~ ~he sheet of adhesive material comprise precomminuting/mixing the mixture for the rubber with the combined action of mechanical processing/temperature and the use of peptization means until a degree of viscosity is obtained such that in the subsequent mixing with reinforcing, charging and vulcanizing substances, these may be suitably broken up in the mixture; a first un-operative stage for a period of approximately 12 hours; dosing and mixing of the components that form the mixture (excluding the vulcanizing agents and the accelerators) in open mixers at low temperature; a second un-oper- ~-ative stage for approximately 12 hours to allow perfect diffusion of the reagents and the inert bodies forming the mixture; mixing -in the mixture the accelerators and the vulcanizing agents in an open mixer at low temperature suitably 30 - 40C; calendering -in sheets of a small thickness; and cutting of the sheets to a size corresponding to the dimensions of the tread on which they will be applied.
Once the sheet 3 has been prepared in accordance with the aforesaid method, it is applied to the smoothed surface la of the premoulded tread 1, over the contact surface of which a special rubber base bonding solution is spread.
In the process according to the invention, as shown in Fig. 2, the application of the sheet of adhesive material 3 to the -; tread 1 requires the tread 1 and the sheet 3 to be passed ~etween normal drive and pressure rollers 17 and between two rollers 4 and 5, the latter having over its full rolling sur~ace a series of sharp tips 6 dimensioned to perforate the sheet 3 until the - surface la of the tread 1 is reached.Subsequently, inside a vacuum chamber 7, expulsion of the air trapped between the tread 1 and the sheet of adhesive material 3 is expelled via the perfor-ations in the sheet 3 and the air is purged from the perforations.
Prior to the assembly of the tread 1 and the sheet of -- - - -,: . ~ :
adhesive material 3 leaving the chamber 7, the free surface o~
the sheet 3 has a protective film 3a of polythene or some other synthetic material applied to it to prevent air ~rom returning to the perforations in the sheet 3 and to conserve the chemical physical characteristics of the sheet 3 against dust and extra- ~;
neous bodies~
In the retreadin~ stage o~ a tyre, the assembly of the tread 1 and the sheet of adhesive material 3 is thus pre-formed ready to be applied to the rolling surface of the previously rasped, smoothed and solution treated carcass 2 of the tyre.
The application is effected in accordance with conventional tech-niques and without there being any risk of the assembly slipping over the carcass 2 of the tyre~ this mainly being due to the fact that the sheet 3 already forms a unitary body with the tread l.
Upon completion of this stage, the tyre is mounted also according to conventional techniques, on a special rim lO
subsequent to the placement of a protective casing 8 around the tyre so as to enshroud the tread l and the sidewalls 9 of the tyre, ~0 with its edges maintained tightly pressed against the sidewalls by the rim 10. The protective casing 8 is provided with a valve ll which allows the air trapped inside the casiny at the time -of fitting on to the tyre to be discharged externally. When -this stage has been completed, the tyre is then placed inside a ~ulcanizing oven 12.
In the process o~ the present invention~ prior to commencement of the actual vulcanization, the protective casing 8 is ~onnected to a vacuum apparatus 14 via a pipe 13 so as to fully purge ~ir from the inslde of the casing 8, even air that normally trapped in the interstices of the tread l. Then by means of a pipe 15, air is passed inside the carcass 2 of the -tyre or into an inner tube 16 in the said tyre, until a pressure is buil~. up which roughly corresponds to the normal workiny pressure of the tyre.
The oven 12 is set in operation to cause ~ulcanization suitably at an optimum temperature of 100C with a suitable heating fluid preferably hot air or steam. The oven 12 is pressurized at a pressure slightly below that of the tyre until the necessary conditions are reached which give rise to the vulcanization reaction, providing a per~ect union between the tread 1 and the carcass 2 of the tyre, with the physical-chemi~al characteristics of the vulcanized material being ~ully guaranteed.
The presence of the anti-scorching agent in the sheet .
of adhesive material 3 advantageously provides an initial retard-ation in the vulcanization reaction, so as to allow the operator to intervene, even after the operation of the oven 12, particular-ly in cases where some handling error is detected subsequently to the placing inside the oven 12 of the tyre prepared for :
vulcanization.
"Monsanto" rheometric tests carried out at 100C show that unlike the sheets of conventional adhesive mate~.ial, the sheet produced in accordance with the process of the present .; invention remains perfectly stabilized at temperatures up to .
35C ~ 40C, delaying the commencement of the vulcanization by approximately 20 - 30 minutes.
~ .
. 30 -- 10 -- :: .
.. . . .. . . .. . . .. . . .
- .- - -, - - . . . .- , ,
The preparation of the rolling surface of the carcass 2 of the tyre involves rasping operations with which all residual parts of the tread to be reformed are removed from the carcass of the tyre 2. The rasping operation is par~icularly intense adjacent the sidewalls of the carcass 2 of the tyre an~ at the -~ . . . . .. . . .
- 1~713~
conclusion of these rasping operations, the rolling surface 2a is arcuate, substantially as shown in Fig. 3, with a radius of curvature R.
The radius R is considered when forming the tread 1 so that the inner surface la of -the tread is arcuate with a radius of curvature Rl identical to the radius I~. The surfaces la o~
the tread 1 and 2a of the carcass 2 of the tyre are thus on the same planes and match each other.
This operating stage avoids the substantial problem which is experienced when preparing the tread.and the carcass of : :
the tyre on the basis of conventional c~rtain techniques, whereby the tread is provided with a perfectly flat inner surface and the adhesive material is built up in the areas close to the sidewalls .
of the carcass of the tyre, so as to bring the rolling surface into the right condition to receive the tread.
The process according to the invention requires the preparation of a sheet of adhesive material 3 to be applied to -`
the tread at the time it is being formed, so that the single assembly of the tread and the sheet of adhesive material can ~:
subsequently be stored without the risk of any kind of reaction occurring. These characteristics are obtained by dosing reagents : . :
which allow the sheet of adhesive material to be produced with /.. ~:.
a high percentage of co-vulcanizing resins and also by a suitable percentage of an anti-scorching agent which prevents the previously . ~.:
mentioned undesired reactions from taking place. The reagents :
used in the production of the sheet of adhesive materialmay varyboth qualitatively and quantitatively depending upon the composition ~
of the tread. By way of an example, the composition by weight is . -- given below of the reagents for producing a standard sheet of :. -adhesiye material suitable for most of the tyres currently on . .::
the market: .
"' .
~(~'7~
COMPONE:NTS P RTS IN WEIGHT
Natural rubber or polyisoprene 100 zinc oxide 5-10 Stearic acid 0.5-1.2 Anti-oxidant (Poly 2-3-4 trimethyl dihydroquinaldine) Anti-ozonant (N-phenyl - N - cyclohexyl para 1-2 phenylendiamine) Pine tar 5-10 Co-vulcanizing resins (Polyhalethyl phenol) 15 Adhesive agents (liquid coumarone/indene resin) 10 suna weld (Polymer 780) 10 Insoluble.. Sulphur 3~5 Accelerators (diphenyl guanadine and 1-3 mercaptobenzothiazole) High structure carbon black 30 Anti-scorching agent (supplied under the trademark 0,05 Santocard PVI) The high percentage of co-vulcanizing resins produces a stabiliæed product which retains indefinitely its adhesive properties. If the lower figure of the ranges is taken, the percentage by weight of the co-vulcanizing resins is 8.2~ and7 if the higher figure is taken the percenta~e by weight of co-vulcanizing resins is 7.6%.
The addition of a suitable percentage of an agent for the prevention of scorching prevents undesired prevulcanization and makes it possible for the sheet of adhesive material 3 to be -applied to the tread 1 and the properties of the assembly of the ; tread and the sheet of adhesive material to remain unchanged. ~ .
The sheet 3 produced in accordance with the composi-tion given above and subjected to "Monsanto" rheometric:tests, using a sample vulcaniæed at 100C, gave the following physical characteristics as a function of time: :
, ' , .
~- 7 - : ~
I .~, ~ ' ~7~
2h 3h 4h Modulus at 300~ 63 64 85 Tensile stress 238 237 235 Ultimate elongation 640 610 560 Shore Test A 46 49 53 ~
. :-- 7a -. .
' ~ ~7t~Z~
The stages for the produc~ion o~ ~he sheet of adhesive material comprise precomminuting/mixing the mixture for the rubber with the combined action of mechanical processing/temperature and the use of peptization means until a degree of viscosity is obtained such that in the subsequent mixing with reinforcing, charging and vulcanizing substances, these may be suitably broken up in the mixture; a first un-operative stage for a period of approximately 12 hours; dosing and mixing of the components that form the mixture (excluding the vulcanizing agents and the accelerators) in open mixers at low temperature; a second un-oper- ~-ative stage for approximately 12 hours to allow perfect diffusion of the reagents and the inert bodies forming the mixture; mixing -in the mixture the accelerators and the vulcanizing agents in an open mixer at low temperature suitably 30 - 40C; calendering -in sheets of a small thickness; and cutting of the sheets to a size corresponding to the dimensions of the tread on which they will be applied.
Once the sheet 3 has been prepared in accordance with the aforesaid method, it is applied to the smoothed surface la of the premoulded tread 1, over the contact surface of which a special rubber base bonding solution is spread.
In the process according to the invention, as shown in Fig. 2, the application of the sheet of adhesive material 3 to the -; tread 1 requires the tread 1 and the sheet 3 to be passed ~etween normal drive and pressure rollers 17 and between two rollers 4 and 5, the latter having over its full rolling sur~ace a series of sharp tips 6 dimensioned to perforate the sheet 3 until the - surface la of the tread 1 is reached.Subsequently, inside a vacuum chamber 7, expulsion of the air trapped between the tread 1 and the sheet of adhesive material 3 is expelled via the perfor-ations in the sheet 3 and the air is purged from the perforations.
Prior to the assembly of the tread 1 and the sheet of -- - - -,: . ~ :
adhesive material 3 leaving the chamber 7, the free surface o~
the sheet 3 has a protective film 3a of polythene or some other synthetic material applied to it to prevent air ~rom returning to the perforations in the sheet 3 and to conserve the chemical physical characteristics of the sheet 3 against dust and extra- ~;
neous bodies~
In the retreadin~ stage o~ a tyre, the assembly of the tread 1 and the sheet of adhesive material 3 is thus pre-formed ready to be applied to the rolling surface of the previously rasped, smoothed and solution treated carcass 2 of the tyre.
The application is effected in accordance with conventional tech-niques and without there being any risk of the assembly slipping over the carcass 2 of the tyre~ this mainly being due to the fact that the sheet 3 already forms a unitary body with the tread l.
Upon completion of this stage, the tyre is mounted also according to conventional techniques, on a special rim lO
subsequent to the placement of a protective casing 8 around the tyre so as to enshroud the tread l and the sidewalls 9 of the tyre, ~0 with its edges maintained tightly pressed against the sidewalls by the rim 10. The protective casing 8 is provided with a valve ll which allows the air trapped inside the casiny at the time -of fitting on to the tyre to be discharged externally. When -this stage has been completed, the tyre is then placed inside a ~ulcanizing oven 12.
In the process o~ the present invention~ prior to commencement of the actual vulcanization, the protective casing 8 is ~onnected to a vacuum apparatus 14 via a pipe 13 so as to fully purge ~ir from the inslde of the casing 8, even air that normally trapped in the interstices of the tread l. Then by means of a pipe 15, air is passed inside the carcass 2 of the -tyre or into an inner tube 16 in the said tyre, until a pressure is buil~. up which roughly corresponds to the normal workiny pressure of the tyre.
The oven 12 is set in operation to cause ~ulcanization suitably at an optimum temperature of 100C with a suitable heating fluid preferably hot air or steam. The oven 12 is pressurized at a pressure slightly below that of the tyre until the necessary conditions are reached which give rise to the vulcanization reaction, providing a per~ect union between the tread 1 and the carcass 2 of the tyre, with the physical-chemi~al characteristics of the vulcanized material being ~ully guaranteed.
The presence of the anti-scorching agent in the sheet .
of adhesive material 3 advantageously provides an initial retard-ation in the vulcanization reaction, so as to allow the operator to intervene, even after the operation of the oven 12, particular-ly in cases where some handling error is detected subsequently to the placing inside the oven 12 of the tyre prepared for :
vulcanization.
"Monsanto" rheometric tests carried out at 100C show that unlike the sheets of conventional adhesive mate~.ial, the sheet produced in accordance with the process of the present .; invention remains perfectly stabilized at temperatures up to .
35C ~ 40C, delaying the commencement of the vulcanization by approximately 20 - 30 minutes.
~ .
. 30 -- 10 -- :: .
.. . . .. . . .. . . .. . . .
- .- - -, - - . . . .- , ,
Claims (6)
1. A process for making a storable assembly for use in retreating a worn tire by direct application to the carcass of the tire of a premolded tread having an inner surface which process comprises preparing a sheet of adhesive material, with which to anchor the tread to the carcass of the tire comprising at least one vulcanizable bonding material, at least one vulcanization accelerator, at least one vulcanizing agent, a relatively high percentage of covulcanizing resins, that is, about 7.6 to 8.2%
by weight of the total composition, and an anti-scorching agent, which agent jointly with said resins being able to vulcanize said vulcanizable bonding material at a temperature of about 100°C and to render the component stable and thus to prevent commencement, up to temperatures of between 35°C and 40°C, of any vulcanization reaction with said sheet of adhesive material in adherence to said inner surface of the tread; bonding said sheet of adhesive material directly to said inner surface of the tread, free of any release member therebetween through a rolling operation while contempor-aneously perforating only said sheet in order to allow escape of air trapped between said tread and said sheet of adhesive material via perforations made in said sheet thereby providing an assembly of the tread and the sheet of adhesive material; and subjecting said sheet in place on said tread to suction for removing air from said perforations in said sheet of adhesive material.
by weight of the total composition, and an anti-scorching agent, which agent jointly with said resins being able to vulcanize said vulcanizable bonding material at a temperature of about 100°C and to render the component stable and thus to prevent commencement, up to temperatures of between 35°C and 40°C, of any vulcanization reaction with said sheet of adhesive material in adherence to said inner surface of the tread; bonding said sheet of adhesive material directly to said inner surface of the tread, free of any release member therebetween through a rolling operation while contempor-aneously perforating only said sheet in order to allow escape of air trapped between said tread and said sheet of adhesive material via perforations made in said sheet thereby providing an assembly of the tread and the sheet of adhesive material; and subjecting said sheet in place on said tread to suction for removing air from said perforations in said sheet of adhesive material.
2. A process according to Claim 1, including apply-ing a protective film to the free surface of said sheet immedi-ately after purging of air from between said tread and said sheet of adhesive material and prior to the cessation of the suction action for the purging of the air.
3. A process as claimed in Claim 1, including applying the assembly to the carcass with the adhesive sheet forming an intermediate layer between the tread and the rolling surface of the carcass, enclosing the assembly and carcass with a protective casing which extends around the tread and the side walls in an air-tight manner, and inserting the enclosed assembly and carcass in a vulcanization oven to effect vulcanization.
4. A process according to Claim 3, in which the carcass and assembly enclosed with the protective casing is placed in the vulcanizing oven, the said protective casing is connected to a vacuum apparatus to create a vacuum in the inside of the said protective casing before vulcanization.
5. A process as claimed in Claim 3, in which the premoulded tread has its inner surface transversely arcuate and of a radius of curvature the same as the radius of curvature of the rolling surface.
6. A process as claimed in Claim 3, in which the rolling surface is prepared by rasping before application of said assembly thereto.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT03314/75A IT1028591B (en) | 1975-01-21 | 1975-01-21 | PERFECTED PROCEDURE FOR THE REBUILDING OF A WORN TIRE BY APPLICATION DIRECTLY TO THE TIRE HOUSING OF A PRE-PRINTED TREAD |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1078120A true CA1078120A (en) | 1980-05-27 |
Family
ID=11104798
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA242,972A Expired CA1078120A (en) | 1975-01-21 | 1976-01-05 | Process for reconstructing a worn tyre through the direct application to the carcass of the tyre of a premoulded tread |
Country Status (15)
| Country | Link |
|---|---|
| JP (1) | JPS5193982A (en) |
| AR (1) | AR206369A1 (en) |
| AT (1) | AT349918B (en) |
| BR (1) | BR7508773A (en) |
| CA (1) | CA1078120A (en) |
| CH (1) | CH591947A5 (en) |
| DE (1) | DE2553975A1 (en) |
| ES (1) | ES443860A1 (en) |
| FR (1) | FR2298429A1 (en) |
| GB (1) | GB1503027A (en) |
| IL (1) | IL48815A (en) |
| IT (1) | IT1028591B (en) |
| NL (1) | NL7515035A (en) |
| SE (1) | SE428279B (en) |
| SU (1) | SU938734A3 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4092196A (en) * | 1976-03-22 | 1978-05-30 | The Goodyear Tire & Rubber Company | Retreading and rebuilding of radial tires |
| DE3333523C2 (en) * | 1983-09-16 | 1986-06-26 | Bandag Inc., Muscatine, Ia. | Method for renewing the tread of a tire and for renewing damaged belts of the carcass of the tire |
| DE3404940C2 (en) * | 1984-02-11 | 1997-05-07 | Ellerbrock Reifenrunderneuerun | Method and device for renewing the side walls of vehicle tires on one or both sides by applying a new rubber layer by means of shapeless vulcanization |
| WO1987003842A1 (en) * | 1985-12-19 | 1987-07-02 | Built-Rite Productions Pty. Limited | Refurbishment of fibreglass panels |
| ITTO20060102A1 (en) * | 2006-02-14 | 2007-08-15 | Bridgestone Corp | METHOD AND PLANT FOR THE CONSTRUCTION OF A TREAD STRIP |
| DE102006029959B4 (en) * | 2006-06-29 | 2010-04-08 | Siemens Ag | Method for producing a plate-shaped insulation support provided with an adhesive layer for a gradient coil of a magnetic resonance apparatus, and device for producing such an insulation support |
| US8632647B2 (en) * | 2008-08-27 | 2014-01-21 | Michelin Recherche Et Technique S.A. | Method of controlling tread shrinkage during curing |
| EP3094501A4 (en) * | 2014-01-16 | 2017-09-06 | Bridgestone Americas Tire Operations, LLC | Tire with laminate and method of making same |
| EP3072673B1 (en) * | 2015-03-24 | 2018-02-07 | Bridgestone Corporation | Pre-vulcanized tread strip assembly useful for the cold retreading of a tyre |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1206149B (en) * | 1960-11-29 | 1965-12-02 | Hoechst Ag | Process for the production of laminated bodies |
| NL277764A (en) * | 1961-05-01 | |||
| FR1370425A (en) * | 1962-10-04 | 1964-08-21 | Bandag Inc | Retreading method and apparatus |
| FR1525435A (en) * | 1967-05-08 | 1968-05-17 | Bandag Inc | Single-layer material for retreading tire casings and method of using this material |
| DE2145574C3 (en) * | 1971-09-11 | 1978-12-21 | Vakuum Vulk Holdings Ltd., Nassau | Method and binding rubber layer for renewing the tread of a worn pneumatic or solid rubber tire |
-
1975
- 1975-01-01 AR AR261830A patent/AR206369A1/en active
- 1975-01-21 IT IT03314/75A patent/IT1028591B/en active
- 1975-12-01 DE DE19752553975 patent/DE2553975A1/en not_active Withdrawn
- 1975-12-02 GB GB49535/75A patent/GB1503027A/en not_active Expired
- 1975-12-02 FR FR7537683A patent/FR2298429A1/en active Granted
- 1975-12-02 SE SE7513550A patent/SE428279B/en not_active IP Right Cessation
- 1975-12-03 CH CH1570175A patent/CH591947A5/xx not_active IP Right Cessation
- 1975-12-11 AT AT939875A patent/AT349918B/en not_active IP Right Cessation
- 1975-12-23 NL NL7515035A patent/NL7515035A/en not_active Application Discontinuation
- 1975-12-24 ES ES443860A patent/ES443860A1/en not_active Expired
- 1975-12-29 JP JP50159637A patent/JPS5193982A/en active Pending
- 1975-12-30 SU SU752306352A patent/SU938734A3/en active
- 1975-12-31 BR BR7508773A patent/BR7508773A/en unknown
-
1976
- 1976-01-05 CA CA242,972A patent/CA1078120A/en not_active Expired
- 1976-01-09 IL IL48815A patent/IL48815A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| IL48815A0 (en) | 1976-03-31 |
| SE7513550L (en) | 1976-07-22 |
| AT349918B (en) | 1979-05-10 |
| NL7515035A (en) | 1976-07-23 |
| SE428279B (en) | 1983-06-20 |
| JPS5193982A (en) | 1976-08-18 |
| ES443860A1 (en) | 1977-04-16 |
| FR2298429A1 (en) | 1976-08-20 |
| IL48815A (en) | 1977-11-30 |
| CH591947A5 (en) | 1977-10-14 |
| BR7508773A (en) | 1977-04-05 |
| FR2298429B1 (en) | 1981-04-30 |
| GB1503027A (en) | 1978-03-08 |
| SU938734A3 (en) | 1982-06-23 |
| AR206369A1 (en) | 1976-07-15 |
| ATA939875A (en) | 1978-09-15 |
| DE2553975A1 (en) | 1976-07-22 |
| AU1009776A (en) | 1977-07-14 |
| IT1028591B (en) | 1979-02-10 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |