DK158778B - PROCEDURE FOR RENOVATING THE TREAD ON A RUBBER - Google Patents

Abstract

According to the process for reconditioning the worn tread of a solid or inflatable tyre, wherein a prefabricated rubber tread is applied by vulcanisation of a binding rubber layer between the tread and the carcass to the latter, the damaged belts of the tyre carcass may also be replaced at the same time. The belts coated with rough rubber, for manufacturing new tyres or for a tyre reconditioning process which have to be carried out at high temperature and pressure conditions, are treated with an activator solution appropriate to the binding rubber. The rough rubber coating of the belt is so transformed that the belt material may be applied with a binding rubber inclusion to replace the damaged belt on the carcass and it may be vulcanised with the layer structure of the tyre blank used to the reconditioning in an over-pressure chamber at a temperature of about 50-95<o>C and at a pressure of 5-6 bars approximately. The belts fabricated according to this process may be used as a base material for manufacturing repair patches.

Description

DK 158778 B

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The invention relates to a method for renovating the tread on a worn pneumatic or solid rubber tire and for renovating or repairing damaged belts in the tire carcass as further specified in the preamble of claim 1.

5 "Heat renovation" is usually and hereinafter referred to as a circular refurbishment and repair method in which raw rubber is vulcanized in a range of 130-190 ° C and at a pressure of 20-50 bar. The vulcanization takes place in a mold in which the 10 rubber seam layers placed all the way around the carcass are formed into the desired tread profile and are compressed and bonded firmly to the carcass. The disadvantages of the heat renovation, namely large mold prices, high investment costs for a minimum equipment of molds, yet limited range of different tire sizes and widths, and tread profiles, large wear on the renovated tread due to relatively poor compression of the rubber structure and / or the forming accumulation of the carcass at high pressure, has long been known.

The above-mentioned known method, where at high pressures in presses, pre-made rubber treads, rubber segments or a rubber base are fixedly fixed to the carcass by vulcanizing a binder rubber layer, is called the "cold renovation method" due to the relatively low vulcanization temperature.

25 High raw material prices and the desire to make more worn tires than hitherto reusable for repair or renovation of the tread means that the renovation companies are also increasingly renovating tires where one or more of the carcass belts are damaged.

30 In connection with the heat renovation, the belts have been renovated for some time, but one must take into account the above-mentioned disadvantages which are peculiar to this renovation.

DK 158778B

veringsmåde. Also in connection with cold renovation, belt renovation experiments have already been carried out. The tests have so far been unsatisfactory and the necessary work effort to obtain a reliable belt overhaul 5 is too great.

In the heat renovation, after removing the damaged belt layers, the metal belts of the most different width coated with raw rubber, embedded in natural rubber or synthetic rubber, are applied to the carcass, which after 10 is coated with raw rubber, after which the tire thus prepared as a whole heated in a mold having the above high temperature and pressure level.

In the cold renovation, a multi-stage method for belt renovation (DE-OS 25 45 463) is known. Here, first, a 15-coated rubber belt is coated with raw rubber on both sides and heated in a flat press with a suitable high temperature and pressure level, so that the belt on both sides is connected with a sufficiently thick, vulcanized rubber layer on which a rough surface can be formed. or a binding surface.

This can be produced either by coating the raw rubber layers with a removable fabric tissue before the vulcanization in the flat press. The fabric tissue impression forms the rough surface when the fabric tissue is pulled off after the vulcanization; or, in a subsequent second method step, the rubber-lined belt is already subjected to a double-sided mechanical backing by grinding or the like to obtain the desired rough surface. The belt thus prepared in one way or another can then be placed on the prepared carcass in a suitable binder car sickness, whereupon the application of the pre-made tread and finally the heating in the pressure chamber at low temperature and pressure level takes place.

Admittedly, this approach allows for reliable and secure belt refurbishment while simultaneously renovating all the way - 3 -

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around, but the large number of necessary process steps means too much work.

The object of the invention is to simplify the renovation or repair of damaged belts by the cold renovation of a tread.

In order to solve this task, the invention is directed to proceed as indicated in the characterizing part of claim 1.

No raw rubber-coated belts have so far existed that are vulcanizable at the low temperature and pressure level of the usual low-temperature renovation 10 with sufficient rubber-metal bonding. In connection with the invention, the following is carried out: A rubber-coated carcass belt or similar reinforcement insert of metal wires or mold material for heat renovation is changed in such a simple manner in the form of a soaking with an accelerator solution. that they are adapted to the working conditions of commercially available, for cold renovation determined binder rubber and thus allow a deviation from their actual purpose 20. The soaking of the raw rubber-coated belt or belt sections is very simple to carry out in comparison with the cold-renovation conditions, where a press is required to vulcanize the belt material and the raw rubber, either by fabrication or by brushing and grinding. of the pre-vulcanized belt material.

Among other things, the accelerator solution shortens the vulcanization time of the raw rubber coating so that this designation is properly selected. It has been found that the bonding between rubber and metal is extremely good, although no heat renovation is carried out in the proper sense of the belt enclosing raw rubber. One with the said

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- 4 - accelerator solution treated section of a raw rubber coated belt is placed after the removal of the damaged belt (s) on the carcass, after which the coating of the carcass with the usual binder rubber layer and with the 5 pre-fabricated tread and finally heating the temperature thus prepared to cold and pressure level is going on.

The method according to the invention can optionally be carried out by renovating all the way around or by repairing tires 10 with belt renovation or partial belt renovation or by exclusively complete or partial renovation of belts on carcasses or in the manufacture of belt repair patches with belt inserts. In any case, a raw rubber-coated belt section after treatment with the accelerator solution 15 is applicable in such a manner as a belt-vulcanized belt section after the production of rough surfaces on the top and bottom. Here, there is a decisive advantage in the method according to the invention.

In the current cold renovation systems, a 20 binder rubber with more or less divergent composition is used; therefore, the person skilled in the art must determine at all times the composition of the accelerator solution depending on the binder rubber used. The required components may be specified at intervals, and those skilled in the art must determine from these interval statements the correct composition of the binder rubber to be used, e.g. by trial.

For a typical binder, according to the invention, the accelerator solution has the following composition: 30 1000 grams Pureoluene 120 grams Tetramethylthiurammonosulfide 60 grams N, Ν'-diphenylthiourea 30 grams Sulfur, normally 180 grams N-phenyl-N'-isopropyl-p-phenylenediamine

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The accelerator solution should in principle be applied to the raw rubber coating until saturated. The treatment can be particularly easily carried out when the accelerator solution after its preparation is diluted with the pure solution in the weight ratio 5 10:80.

Belt material treated according to the invention with accelerator solution is stock-resistant according to the nature of raw rubber and accelerator solution for approx. 6 months. Therefore, belts can be stocked ready for 10 belt renovation. Prepared belt material can either be manufactured by the vulcanizer itself if the necessary conditions for manufacture exist in the company, or the material may alternatively be made by the manufacturer of the renovation material, which makes the necessary adjustment of the accelerator solution to the common binder material used in the system used and the treatment of the belt material. a suitable accelerator solution and finally the delivery to the vulcaniser. Therefore, the method according to the invention can also be carried out as claimed in claim 4.

Also the manufacture of repair patches of raw rubber-coated steel cord or nylon fabric, especially for truck tires and large tires, e.g. for construction machinery is possible by the method according to the invention. Repair patches of any size and thickness as well as angular layers of metal or plastic wires can be made in this way.

The invention also allows for incorporation of additional protective sections of belt sections treated by the method of the invention during a circular renovation. Additional layers of protection make the tires insensitive to damage, especially when using the tires in places with metal debris. Additional protective layers may also be placed between the profiled sheets on non-profiled tires when layered. In addition, the invention enables - 6 -

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the application of shoulder dressings by using belt layers having a wire angle of 0 ° to reduce the rolling resistance.

The method of cold renovation according to the invention enables many uses and treatments, as well as improvements in parallel with the overhaul of a tire which has hitherto not been possible or only possible with relatively high costs.

Some examples are given below: When renovating a tread on a worn pneumatic or solid rubber tire, it is also desirable to carry out a belt renovation, first removing the damaged belts from the tire carcass. Thereafter, the required belt sections are cut from the commercially available, and themselves for heat renovation calculated raw rubber coated belt material of suitable length. When removing multiple belt layers, a similar number of belt sections are prepared.

Then, the belt section is soaked with an accelerator solution, the composition of which has already been described, up to 20 saturation. is applied by immersion in a bath or with a brush or by means of a spray gun on both sides of the raw rubber section of the belt.

After approx. After 30 minutes, the accelerator solution is withdrawn and dried onto the surface of the raw rubber coating so that the belt section is prepared for further processing according to the cold renovation method according to a known system.

The belt section thus treated is now placed on the prepared carcass, which is suitably coated with a thin binder rubber layer. In any case, the belt section of the carcass or even before placement must receive a binder rubber embedment.

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- 7 - The belt sections may consist of narrow or wide belts. Commercial belts have a width of 90-220 mm with a thread angle of 18-22 °. Depending on the width of the carcass, several narrow belts can be used, preferably with overlap, if necessary. also only one single wide belt. For larger-width tires, the width of commercially available belts is not sufficient, so multiple belts must be placed side by side and formed the subsequent belt length while covering the joint site by appropriate lateral displacement.

On top of the belts placed on the carcass, there is then applied the bonding rubber layer common in cold renovation, which is to form the bond between the carcass and a tread. Then, the finished tread is placed as a whole or a length at a time depending on the size and width of the tires and profiles. Care must be taken that no air enclosures are formed during the formation of the carcass layer or that, if they cannot be avoided, these are removed.

Thereafter the heating of the thus-coated carcass is carried out in the vacuum room at a pressure and heat treatment carried out during cold renovation at a temperature below 95 ° C and at a pressure of 5-6 bar. The carcass may be enclosed by a casing, but a so-called casing-free method may also be used, e.g. according to DE-PS 17 97 113. In any case, the binder jaw forms an insoluble connection with the carcass and with the raw sections of the belt sections and in the usual way with the tread itself. It is of particular importance that the belt, as well as binder rubber and 30 finished tread, placed in a single workflow during simultaneous renewal of the tread surface by means of a new pre-made tread is inextricably incorporated into the carcass in a precisely predetermined position.

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To facilitate easier application of the accelerator solution, the accelerator solution is diluted with the above or another composition appropriately in the 10:80 weight ratio with the pure solution.

The pure solvent used to prepare the accelerator solution and for its dilution preferably has the following composition:

Molecular weight 92

Color (Saybolt) + 30 10 Density at 15 ° C, g / ml 0.871

Boiling point (range) at 1013 mbar (769 torr), ° C 1.0 incl. 110.6

Evaporation rate (ether = 1) 6

Solidification point, ° C

15 Doctor Test Negative

Corrosion (Cu) Negative

Kauri-butanol value 1-2 + SO2 Nothing

Flash point, ° C +5 20 Vapor pressure at 25 ° C, mbar (1 mbar = 0.75 torr) 38

Surface tension at 20 ° C

mN / m (dyn / cm) 28

Kinematic viscosity, 10_6m2 / s (cSt) at 20 ° C 0.68

The accelerator solution must be stored in dark bottles or containers, as it can be decomposed by exposure to sunlight. For maintaining the adhesive force of the accelerator solution treated belt material which is of importance 30. for later bonding, the belt material must be wrapped airtight in foil.

Regarding the effects of the accelerator solution, it should be further emphasized that even in the case of over-vulcanization, there is no deterioration of rubber - 9 -

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The adhesive properties of the coating, since a low temperature level is used for the vulcanization. The rubber coating of the belt material also provides additional aging protection when treated with accelerator solution.

5 In the manufacture of steel belts with raw rubber coatings, the rubber manufacturers prefer, as raw rubber blend, two mixing systems, which are referred to as "Co system" and "RFS system". The Co system contains Co-naphthenate as an adhesive aid, and for this purpose the RFS system uses resorcin, hexamethylenetetramine in conjunction with silicic acid filler. With the latter system, a better aging resistance can be obtained, while the adhesive between rubber and metal has slightly lower values, while the conditions are the other way around with the Co system.

Typical raw rubber mixtures for steel belt coatings for both systems have e.g. the following composition:

Co-system RFS system NR-RSS 1 - 100.00 parts by weight 100.00 parts by weight

Stearic acid - 1.50 parts by weight 1.50 parts by weight

Softener, aromatic - 2.50 parts by weight 20 Haerusen - 2.00 parts by weight 2.00 parts by weight

Zinc Oxide - 8.00 parts by weight 8.00 parts by weight Carbon N N 330 - 60.00 parts by weight 48.00 parts by weight ASM-IPPD - 2.50 parts by weight ASM-PBN - 2.00 parts by weight ---- 25 Co-naphthenate 8% - 3 , 00 parts by weight ----

Resorcin - 2.50 parts by weight

Hexamethylenetetramine - 1.50 parts by weight

Silica Filler - 15.00 parts by weight

Accelerator DCBS - 0.70 parts by weight 0.70 parts by weight 30 Sulfur - insoluble 80% - 5.00 parts by weight_5.00 parts by weight 182,20 parts by weight 189,20 parts by weight

A steel belt coating which can be used in accordance with the invention as well as the two above-mentioned mixtures and which belong to -

DK 158778B

The co-system, but having a somewhat changed composition, is hereinafter indicated with the physical properties obtained by a 20 minute vulcanization at a temperature of 150 ° C: 5 NR-RSS3 - 100.00 parts by weight Tensile strength in MPa = 17

Stearic acid - 1.00 parts by weight Stretch in% = 420

Colophonium - 1.50 parts by weight Module-300 in MPa = 11

Zinc oxide - 10.00 parts by weight Further tearing carbon black N 330 - 50.00 parts by weight resistance in KN / m = 17 XO Co-naphthenate - 2.50 parts by weight Hardness in Sh-A = 64 ASM - IPPD - 2.00 parts by weight Elasticity at

Accelerator MBS - 0.70 parts by weight 70 ° C in% = 58

Sulfur Su - 4.70 parts by weight HBU Δ T in K = 25 172.40 parts by weight 15 A typical raw rubber coating for a truck radial tire with a textile belt, which is also suitable for the treatment according to the invention, has the following composition and after a 20 minute vulcanization at a temperature of 150 ° C the following physical properties are obtained: 20 NR-RSS3 - 100.00 parts by weight Tensile strength in MPa = 18

Stearic acid - 2.50 parts by weight Extensibility in% = 380

Colophonium - 1.50 parts by weight Module-300 in MPa = 8

Haerus - 0.20 parts by weight

Pine tar - 6.00 parts by weight tearing resistance in KN / m = 18 25 Zinc oxide - 8.00 parts by weight Hardness in Sh-A = 71 Carbon black N330 - 55.00 parts by weight Elasticity of ASM-IPPD - 1.00 parts by weight 70 ° C in% = 51 ASM-PBN - 1.00 parts by weight of HBU Δ T in K = 39

Accelerator MBS - 1.40 parts by weight 30 Sulfur Su - 4.00 parts by weight 180.60 parts by weight

The invention will be further explained in connection with the drawing. This shows in graphical form the results obtained in comparative experiments with a reversal test.

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By means of a Monsanto rheometer 100 a reversal test is performed on three samples, in particular to assess the raw rubber material after the treatment with an accelerator solution according to the invention in comparison with an untreated material and in comparison with a suitable binder rubber. In the reversion test, a sample of raw rubber is vulcanized and, depending on the time, the elastic torque of the sample subjected to torsion is measured. In the drawing, the approximately horizontal lines extending from the left edge of the image to the center of the image should be added as a continuation of the three curves at the right edge of the image. In this way, despite a time scale of only 12 minutes, a viewing time of 15 18-19 minutes is obtained.

Curve 1 shows a raw rubber mixture for coating a steel belt material for a heat renovation by the aforementioned Co system, which, like the other two samples, has been heated to a temperature of 170 ° C. Curve 2 relates to the same material which, however, before the test has been treated with the said accelerator solution. Curve 3 finally shows the reversal test for a binder rubber designed for cold renovation.

The raw raw rubber shows the typical slow increase in the torque value depending on the time resulting from its heat recovery determination. In this way, over-vulcanization is prevented. The same material, however treated with the accelerator solution of the invention, shows a distinctly different relationship, namely a much faster vulcanization, very similar to the vulcanization of the binder rubber. Because of the high temperatures, the binder rubber shows a marked decrease, which is equivalent to over-vulcanization, ie with some decomposition.

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Particularly important in this comparison test is the constant high level of torque values for the raw rubber treated with accelerator solution. Also, over a very long period of time, in comparison 5 with untreated raw rubber, there is practically no decrease, so that despite accelerator solution there is no danger of over-vulcanization.

Claims (4)

A method for renovating the tread on a worn pneumatic or solid tire and for renovating or repairing damaged belts on the tire carcass, where the damaged belts or belt parts are removed from the carcass 5 and replaced, and where a layer is applied to the prepared carcass. binder rubber, upon which is placed a prefabricated rubber tread as a whole or segmentally, avoiding or removing gaseous inclusions between the applied layers, and subjecting the thus prepared blank to vulcanization of the binder sheet to a pressure chamber. and heat treatment at a temperature of 50-95 ° C and at a pressure of 5-6 bar, characterized in that at least one portion of a belt for heat renovation and coated with raw rubber 15 is soaked until saturation by one or more application times. of an accelerator solution tuned to the binder cushion of: 1000 g Rentoluene 20-240 g tetramethyl thiurammonosulfide 20 10-180 gr N, Ν'-diphenylthiourea 0-300 gr Sulfur, normally 0-500 gr N-phenyl-N'-isopropyl-p-phenylenediamine, whereupon the accelerator solution is dried and the thus prepared dried belt section with a binder rubber layer of : 25 Natural rubber or? styrene butadiene rubber or polybutadiene or a mixture thereof 100 parts by weight Silicic acid and carbon black 30-80 parts by weight 30 Softener 5-10 parts by weight Sulfur and sulfur emitting agent 0.8-4.5 parts by weight Anti-aging agent 0.8-4.0 parts by weight Accelerator 0.5-3.5 parts by weight Coresin 1.0-15.0 parts by weight - 14 - DK 158778B sooner or later is placed on the carcass, upon which the layer structure of the binder rubber layer and the tread is formed, and the blank is then subjected to pressure and heat treatment for the vulcanization of both the binder rubber layer and the raw rubber coating of the belt or belts. Process according to claim 1, characterized in that the accelerator solution after its preparation is diluted in the weight ratio 10:80 with the pure solution. Method according to claims 1-2, characterized in that the belt section is coated on one or both sides with a 0.5-2.0 mm thick binder rubber layer. Method according to claim 1, characterized in that the raw rubber of the belt or belt section is treated with accelerator solution in such a way that the raw rubber is vulcanizable together with the binder rubber.