CA1055649A - Treatment of vulcanised rubber - Google Patents
Treatment of vulcanised rubberInfo
- Publication number
- CA1055649A CA1055649A CA291,725A CA291725A CA1055649A CA 1055649 A CA1055649 A CA 1055649A CA 291725 A CA291725 A CA 291725A CA 1055649 A CA1055649 A CA 1055649A
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- CA
- Canada
- Prior art keywords
- rubber
- product
- vulcanised
- alkali
- finely
- 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.)
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Abstract
ABSTRACT OF THE DISCLOSURE
A finely-divided vulcanised rubber is obtained from vulcanized rubber by contacting vulcanized rubber with a fatty acid, contacting the resulting product with a solid alkali and forming a dispersion of the thus obtained product with a liquid which dissolves the alkali but does not affect the rubber; in this way a finely-divided product having a particle size generally less than 20 microns can be obtained and this micronized crumb can be employed in the manufacture of rubber products.
A finely-divided vulcanised rubber is obtained from vulcanized rubber by contacting vulcanized rubber with a fatty acid, contacting the resulting product with a solid alkali and forming a dispersion of the thus obtained product with a liquid which dissolves the alkali but does not affect the rubber; in this way a finely-divided product having a particle size generally less than 20 microns can be obtained and this micronized crumb can be employed in the manufacture of rubber products.
Description
---` 110 55649 This invention relates to rubbers, more especially the invention is concerned with particulate vulcanised, recycled rubber and rubber vulcanisates produced therefrom, and to a method of producing the particulate vulcanised rubber, This application is a divisional of Canadian Patent Application Serial No. 189,037, filed December 27, 1973.
The re-use of vulcanised rubber in a finely-divided form is well-known in the rubber industry. Such material is usually prepared by grinding on a two-roll mill and normally has a particle size such that it will pass through a "40's mesh"
screen (i.e. 388 microns in diameter). It is also well-known that when this crumb is added to a rubber compound, the tensile strength and other important properties of the vulcanisate deteriorate by a substantial amount.
It has now been found that vulcanised natural or synthetic rubber can be finely-divided such that the particle size is generally less than 20 microns, and that this microni~ed crumb can be added to a rubber compound or com-position and the whole vulcanised to give a product whose physical properties are only slightly worse than those given by vulcanisates of that compound.
According to the invention there is provided a method of converting vulcanised rubber into finely-divided vulcanised rubber which comprises the steps of: (1) contacting vulcanised rubber with a fatty acid, (2) contacting the product of step (1) with a solid alkali, and ~3) forming a dispersion of the product of step (2);siuitably the dispersion in step (3) is formed by passing the product of step (2~ together with water through a disc mill, whereafter finely-divided ;~
rubber is removed from the dispersion. The rubber is ~;
comminuted in the disc mill. ~-55&,4~
By means of the present invention ~here is provided, finely divided vulcanised rubber having a particle size of . .
generally less than 20 microns, the properties of its compounds ~ .
being significantly better than those of conventional xeclaimed rubbers~ Preferably at least 9G% of the vulcanised rubber particles have a size of less than 20 microns.
Thus, by means of the invention there is provided a finely-divided, vulcanised, recycled rubber comprised pre-dominantly of particle~q having a particle size less than 20 microns, the particles being further characterized by the property of separating out from an admixture with water.
The invention also provides a non-particulate rubber vulcanisate containing the finely-divided, vulcanised, recycled rubber as the sole rubber component or in admixture with an unvulcanised, non-recycled rubber.
The invention provides a rubber composition containing the finely divided rubber particles as the sole rubber com~
ponent and having properties significantly better than those of similar compositions containing conventional reclaimed rubber4. This rubber composition may be vulcanised to form a vulcanisate having a tensile strength of above 9MN/m2 and pre- :
ferably having a tear strength above 55N/Std, The invention also provides a rubber composition com-prising in admixture the finely divided vulcanised rubber an~
unvulcanised rubber. Depending on the amount of unvulcanised ~- :
rubber in the mixture, this rubber composition may be vulcanised to form vulcanisates containing from 10 to 7~/O by weight of the finely divided vulcanised rubber and with tensile strengths ranging from 23 to 15 MN/m2.
It will be appreciated that the rubber compositions may contain, in addition to the rubber components, con~entional auxiliary substances such as accelerators, cross-linki:ng agents,
The re-use of vulcanised rubber in a finely-divided form is well-known in the rubber industry. Such material is usually prepared by grinding on a two-roll mill and normally has a particle size such that it will pass through a "40's mesh"
screen (i.e. 388 microns in diameter). It is also well-known that when this crumb is added to a rubber compound, the tensile strength and other important properties of the vulcanisate deteriorate by a substantial amount.
It has now been found that vulcanised natural or synthetic rubber can be finely-divided such that the particle size is generally less than 20 microns, and that this microni~ed crumb can be added to a rubber compound or com-position and the whole vulcanised to give a product whose physical properties are only slightly worse than those given by vulcanisates of that compound.
According to the invention there is provided a method of converting vulcanised rubber into finely-divided vulcanised rubber which comprises the steps of: (1) contacting vulcanised rubber with a fatty acid, (2) contacting the product of step (1) with a solid alkali, and ~3) forming a dispersion of the product of step (2);siuitably the dispersion in step (3) is formed by passing the product of step (2~ together with water through a disc mill, whereafter finely-divided ;~
rubber is removed from the dispersion. The rubber is ~;
comminuted in the disc mill. ~-55&,4~
By means of the present invention ~here is provided, finely divided vulcanised rubber having a particle size of . .
generally less than 20 microns, the properties of its compounds ~ .
being significantly better than those of conventional xeclaimed rubbers~ Preferably at least 9G% of the vulcanised rubber particles have a size of less than 20 microns.
Thus, by means of the invention there is provided a finely-divided, vulcanised, recycled rubber comprised pre-dominantly of particle~q having a particle size less than 20 microns, the particles being further characterized by the property of separating out from an admixture with water.
The invention also provides a non-particulate rubber vulcanisate containing the finely-divided, vulcanised, recycled rubber as the sole rubber component or in admixture with an unvulcanised, non-recycled rubber.
The invention provides a rubber composition containing the finely divided rubber particles as the sole rubber com~
ponent and having properties significantly better than those of similar compositions containing conventional reclaimed rubber4. This rubber composition may be vulcanised to form a vulcanisate having a tensile strength of above 9MN/m2 and pre- :
ferably having a tear strength above 55N/Std, The invention also provides a rubber composition com-prising in admixture the finely divided vulcanised rubber an~
unvulcanised rubber. Depending on the amount of unvulcanised ~- :
rubber in the mixture, this rubber composition may be vulcanised to form vulcanisates containing from 10 to 7~/O by weight of the finely divided vulcanised rubber and with tensile strengths ranging from 23 to 15 MN/m2.
It will be appreciated that the rubber compositions may contain, in addition to the rubber components, con~entional auxiliary substances such as accelerators, cross-linki:ng agents,
- 2 - . :
. ~.. .' ' . . , , ~ ' , . ~
_ ~55~4L9 fillers, antioxidants and softeners.
The manufacture of the micronised crumb according to the method of the invention suitably comprises the following steps:-(1) addition of fatty acid to the vulcanised rubber e.g.oleic acid, stearic acid, tall oll fatty acid or rosin acids, (2) mixing a solid alkali with the product of step (1), and
. ~.. .' ' . . , , ~ ' , . ~
_ ~55~4L9 fillers, antioxidants and softeners.
The manufacture of the micronised crumb according to the method of the invention suitably comprises the following steps:-(1) addition of fatty acid to the vulcanised rubber e.g.oleic acid, stearic acid, tall oll fatty acid or rosin acids, (2) mixing a solid alkali with the product of step (1), and
(3) forming a dispersion of the product of step (2) with a liquid which dissolves the alkali but does not affect the rubber e.g., water, methyl alcohol or ethylene glycol.
In the first step, the vulcanised rubber may be comm~nuted or ~hredded and the resultant coarse crumbs allowed to absorb up to 15% by weight (e.g. 3% by weight) of a fatty acid such as oleic acid. The plasticised vulcanisate may then be sheeted out on a two-roll mill using a tight cap.
In the second step of the process, the solid alkali may be dusted on to the sheet. The solid alkali may be an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, although weaker alkalis or baseA, such as sodium carbonate, or mixtureR of alkalis or bases, such as sodium ;
hydroxide/sodium tetraborate, may also be used. The amount of ~;
alkali used may be 2 to 25 parts by weight per 100 parts by weight of rubber e.g. 10 parts by~ weight of alkali.
The mechanical treatment of the rubber may be con- ;
tinued during or after the addition of the alkali e.g. by extruding the rubber mixture, and the temperature of the rubber mixture at this stage may be higher than in the first step, but it should preferably be kept as low as possible. The comminuting of the rubber with solid alkali may be continued - 3 - ' ., , :: ' . , ' ' ' ~': ' ' ' . ' .' ~ ~55G4~ :, . . .
until the rubber mixture is friable, at which time it is also hydrophilic.
The rubber dispersion of the third step may be obtained by mixing the friable rubber mixture obtained in the second step with water and further comminuting the rubber particles in the resulting mixture by any method effective to produce rubber particles of the required size. A suitable method of comminution is, for example, to pass the aqueous mixture between two discs, one of which may be fixed and the other rotating at constant speed or both of which are rotating either in opposite directions or in the same direction at different speeds. In this way, the rubber particles in an aqueous mixture may be mechanically broken down and stabilized a~ an aqueous disper~ion of the rubber obtained, This a~ueous dispersion of the rubber may issue as a stable creamy paste. To obtain dry powder from this, the paste, possibly after dilution with water, may be coagulated with acid e.g. hydrochloric acid, or other electrolyte e.g. sodium ~;
chloride, or any coagulating technique. It may then be fed into a centrifugal dryer, where the liquid is removed. The product may then be washed with water until the ef~luent from the dryer is neutral to universal indicator paper. Alternatively it is possible to produce the powder merely by separation of the liquid in a centrifugal dryer followed by washing with water until the effluent is neutral. The product is in the form of a fine powder which is preferably dried at a temperature sufficiently low to avoid damaging the structure of the rubber.
It would appear that the mechanical working helps to disperse the fatty acid more uniformly throughout the whole mass. The alkali then reacts with the acid, dispersed within the thin layers, thus resulting in finer particles. It also facilitate~ the formation of a suspension on the addition of
In the first step, the vulcanised rubber may be comm~nuted or ~hredded and the resultant coarse crumbs allowed to absorb up to 15% by weight (e.g. 3% by weight) of a fatty acid such as oleic acid. The plasticised vulcanisate may then be sheeted out on a two-roll mill using a tight cap.
In the second step of the process, the solid alkali may be dusted on to the sheet. The solid alkali may be an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, although weaker alkalis or baseA, such as sodium carbonate, or mixtureR of alkalis or bases, such as sodium ;
hydroxide/sodium tetraborate, may also be used. The amount of ~;
alkali used may be 2 to 25 parts by weight per 100 parts by weight of rubber e.g. 10 parts by~ weight of alkali.
The mechanical treatment of the rubber may be con- ;
tinued during or after the addition of the alkali e.g. by extruding the rubber mixture, and the temperature of the rubber mixture at this stage may be higher than in the first step, but it should preferably be kept as low as possible. The comminuting of the rubber with solid alkali may be continued - 3 - ' ., , :: ' . , ' ' ' ~': ' ' ' . ' .' ~ ~55G4~ :, . . .
until the rubber mixture is friable, at which time it is also hydrophilic.
The rubber dispersion of the third step may be obtained by mixing the friable rubber mixture obtained in the second step with water and further comminuting the rubber particles in the resulting mixture by any method effective to produce rubber particles of the required size. A suitable method of comminution is, for example, to pass the aqueous mixture between two discs, one of which may be fixed and the other rotating at constant speed or both of which are rotating either in opposite directions or in the same direction at different speeds. In this way, the rubber particles in an aqueous mixture may be mechanically broken down and stabilized a~ an aqueous disper~ion of the rubber obtained, This a~ueous dispersion of the rubber may issue as a stable creamy paste. To obtain dry powder from this, the paste, possibly after dilution with water, may be coagulated with acid e.g. hydrochloric acid, or other electrolyte e.g. sodium ~;
chloride, or any coagulating technique. It may then be fed into a centrifugal dryer, where the liquid is removed. The product may then be washed with water until the ef~luent from the dryer is neutral to universal indicator paper. Alternatively it is possible to produce the powder merely by separation of the liquid in a centrifugal dryer followed by washing with water until the effluent is neutral. The product is in the form of a fine powder which is preferably dried at a temperature sufficiently low to avoid damaging the structure of the rubber.
It would appear that the mechanical working helps to disperse the fatty acid more uniformly throughout the whole mass. The alkali then reacts with the acid, dispersed within the thin layers, thus resulting in finer particles. It also facilitate~ the formation of a suspension on the addition of
4 -.. , ~
.
~ 556~9 water if suitable mechanical action is applied.
It is a preferred feature of the method of the invention that the temperature should be k~ept as low as possible at all times, since at temperatures above lOO~C the molecules of natural rubber are known to rupture, giving an inferior material with lower molecular weight. In the case of synthetic rubbers the reactions are more complicated; in some cases material of low molecular weight is formed and in others additional cross-linking occurs after the initial rupture and a material of much ~ -higher molecular weight is produced. In either case the product is inferior to the original material.
Reclaimed rubber or "reclaim" is sometimes used to replace some of the virgin rubber in a compound: this is produced as a re3ult of the effect of high temperature (in excess of 150C) on vulcanised rubber, and gives properties which are markedly inferior to the original vulcanisates (see Example I
below). Commercial reclaims, further, are usually produced in bulk form and cannot raadily be obtained as a powder: with the present tendency to use powdered rubbers and powdered ingredients for automatic weighing and processing, this i9 a further disadvantage of this latter form of recycled rubber~ ;
The invention is illustrated in particular and preferred embodiments by reference to the following Examples.
EXAMPLE I
300 g. of a commercial whole tyre crumb (40 mesh size) are milled for ten munutes on a two roll mill (22 x 44 cm) at a setting of 0.12 mm., with 9g. of oleic acid. A~ this stage 30 g. of powdered solid sodium hydroxide are added evenly to the rubber mix and milling continued for a further ten minutes. The temperature of the mill is 60C.
The product in the form of a dry friable sheet, is removed from the mill and placed in the hopper of a comm~rcial ;;~ : .
~,, . : . ~ . : ,. . . ;
7.5 cm. disc mull. Onto the product is poured sufficient water to wet it (500 ml.). The mill is started with a gap setting on the grinding stones (46 grit carborundum) of 0.5 mm. and a running speed of 4000 rpm. The product issuing from the mill is a stable creamy paste. This is fed directly into a commercial centrifugal dryer where it is retained in a polyester fabric (750 denier) bag. The water is removed centrifugally and the product wash by continuous addition of water to the spin dryer. The washing is continued until the wash water is neutral to universal indicator paper. The product, in the form of a fine powder, is dried under vacuum (10 mm mercury) at 80C.
Example II
Example I was repeated except that the product from the disc mill is diluted with water and neutralised by the addition of dilute (2 N) hydrochloric acid.
The vulcanizates ohtained have similar properties to those prepared by Example I.
For comparison of the fine powder prepared as in Example I with a conventional reclaimed rubber, 100 parts by weight of each of these two materIals were compounded with 2 parts of zinc oxide, 1 part of stearic acid, 1 part of Flectol H, (trademark for polymerized 1,2-dihydro- ;
2,2,4-trimethylquinoline), 0.27 parts of cyclohexyl-benzthiazylsulphenamide, 0.24 parts of diphenylguanidine and 0.53 parts of sulphur. Slabs 150 x 150 x 2 mm were press-moulded to optimum cure at 150C. On testing by standard methods the following results were obtained:-~556~
Table I
Whole Tyre Micronised Reclaim Crumb . .
Tensile Strength 7.4 10.4 (M~/m2 Elongation at Break (%) 360 300 :
Modulus 10~/o (MN/m2i) 1.6 2 4 Modulus 30~/o (MN/m2) 5 7 10.5 ..
Hardness (IRHD) 55 67 ::
Tear Strength (Crescent) (N/Std) 51 58 : .
Taber Abrasion loss : .
(g/1000 cycles) 0.8 0.46 : :
It will be seen that there is a good improvement in :
the tensile strength of the compound made from the micronised product. Improvement is also seen in the taber abrasion and tear strength. :~
For a further comparison of the fine powder with 40's mesh type crumb and conventional reclaimed rubber, 82 parts by weight of each of the three materials were ~.
compounded with lO0 parts of styrene butadiene rubber (Grade 1500), 3 parts of zinc oxide, 3 parts of stearic .
acid, 1 part of Flectol ~ (trademark), 43 parts of HAF
black (high abrasion furnace black), 10 parts of Dutrex R
softener (trademark for an aromatic hydrocarbon concentrate .
derived from petroleum~ 0.~ parts of cyclohexyl-benzthiazylsulphenamide, 0.8 parts of diphenylguanidine ' ' ' .
: .:
.
~55649 and 1.75 parts of sulphur. Slabs 150 x 150 x 2 mm. were press-moulded at a temperature of 150C. for 15 minutes. A similar slab of the base compound (i.e~ without any form of recycled rubber) was also prepared. On testing by standard methods the following results were obtained~
Table II
Whole tyre micronized Type of Additive ~il 40's mesh crumb reclaim crumb 1 . ' ~': "
Tensile Strength 23.7 15.5 15.9 18.7 (MN/m ) Elongation at 580 400 520 490 break (%) Modulus 10~/o 1.5 1.7 1.6 1.6 extension Modulu~ 300/O 8.9 9.7 7.2 8.6 extension Hardness (IRHD) 63 63 62 61 Taber abrasion 0.1345 0.2202 0.2459 0.1454 lo~s (g/1000 ~ ;
cycles) ~-The rubber in column 1 above contained no recycled rubber. The rubbers in columns 2 to 4, all contained recycled rubber, that of column 4 being made in accordance with the invention. It will be ~een that the tensile strength of rubber 4, although lower than that of rubber 1, is superior to that of rubbers 2 and 3. Rubber 4 also has satisfactory abrasion resistanceO
: . :
.
.
.
~ 556~9 water if suitable mechanical action is applied.
It is a preferred feature of the method of the invention that the temperature should be k~ept as low as possible at all times, since at temperatures above lOO~C the molecules of natural rubber are known to rupture, giving an inferior material with lower molecular weight. In the case of synthetic rubbers the reactions are more complicated; in some cases material of low molecular weight is formed and in others additional cross-linking occurs after the initial rupture and a material of much ~ -higher molecular weight is produced. In either case the product is inferior to the original material.
Reclaimed rubber or "reclaim" is sometimes used to replace some of the virgin rubber in a compound: this is produced as a re3ult of the effect of high temperature (in excess of 150C) on vulcanised rubber, and gives properties which are markedly inferior to the original vulcanisates (see Example I
below). Commercial reclaims, further, are usually produced in bulk form and cannot raadily be obtained as a powder: with the present tendency to use powdered rubbers and powdered ingredients for automatic weighing and processing, this i9 a further disadvantage of this latter form of recycled rubber~ ;
The invention is illustrated in particular and preferred embodiments by reference to the following Examples.
EXAMPLE I
300 g. of a commercial whole tyre crumb (40 mesh size) are milled for ten munutes on a two roll mill (22 x 44 cm) at a setting of 0.12 mm., with 9g. of oleic acid. A~ this stage 30 g. of powdered solid sodium hydroxide are added evenly to the rubber mix and milling continued for a further ten minutes. The temperature of the mill is 60C.
The product in the form of a dry friable sheet, is removed from the mill and placed in the hopper of a comm~rcial ;;~ : .
~,, . : . ~ . : ,. . . ;
7.5 cm. disc mull. Onto the product is poured sufficient water to wet it (500 ml.). The mill is started with a gap setting on the grinding stones (46 grit carborundum) of 0.5 mm. and a running speed of 4000 rpm. The product issuing from the mill is a stable creamy paste. This is fed directly into a commercial centrifugal dryer where it is retained in a polyester fabric (750 denier) bag. The water is removed centrifugally and the product wash by continuous addition of water to the spin dryer. The washing is continued until the wash water is neutral to universal indicator paper. The product, in the form of a fine powder, is dried under vacuum (10 mm mercury) at 80C.
Example II
Example I was repeated except that the product from the disc mill is diluted with water and neutralised by the addition of dilute (2 N) hydrochloric acid.
The vulcanizates ohtained have similar properties to those prepared by Example I.
For comparison of the fine powder prepared as in Example I with a conventional reclaimed rubber, 100 parts by weight of each of these two materIals were compounded with 2 parts of zinc oxide, 1 part of stearic acid, 1 part of Flectol H, (trademark for polymerized 1,2-dihydro- ;
2,2,4-trimethylquinoline), 0.27 parts of cyclohexyl-benzthiazylsulphenamide, 0.24 parts of diphenylguanidine and 0.53 parts of sulphur. Slabs 150 x 150 x 2 mm were press-moulded to optimum cure at 150C. On testing by standard methods the following results were obtained:-~556~
Table I
Whole Tyre Micronised Reclaim Crumb . .
Tensile Strength 7.4 10.4 (M~/m2 Elongation at Break (%) 360 300 :
Modulus 10~/o (MN/m2i) 1.6 2 4 Modulus 30~/o (MN/m2) 5 7 10.5 ..
Hardness (IRHD) 55 67 ::
Tear Strength (Crescent) (N/Std) 51 58 : .
Taber Abrasion loss : .
(g/1000 cycles) 0.8 0.46 : :
It will be seen that there is a good improvement in :
the tensile strength of the compound made from the micronised product. Improvement is also seen in the taber abrasion and tear strength. :~
For a further comparison of the fine powder with 40's mesh type crumb and conventional reclaimed rubber, 82 parts by weight of each of the three materials were ~.
compounded with lO0 parts of styrene butadiene rubber (Grade 1500), 3 parts of zinc oxide, 3 parts of stearic .
acid, 1 part of Flectol ~ (trademark), 43 parts of HAF
black (high abrasion furnace black), 10 parts of Dutrex R
softener (trademark for an aromatic hydrocarbon concentrate .
derived from petroleum~ 0.~ parts of cyclohexyl-benzthiazylsulphenamide, 0.8 parts of diphenylguanidine ' ' ' .
: .:
.
~55649 and 1.75 parts of sulphur. Slabs 150 x 150 x 2 mm. were press-moulded at a temperature of 150C. for 15 minutes. A similar slab of the base compound (i.e~ without any form of recycled rubber) was also prepared. On testing by standard methods the following results were obtained~
Table II
Whole tyre micronized Type of Additive ~il 40's mesh crumb reclaim crumb 1 . ' ~': "
Tensile Strength 23.7 15.5 15.9 18.7 (MN/m ) Elongation at 580 400 520 490 break (%) Modulus 10~/o 1.5 1.7 1.6 1.6 extension Modulu~ 300/O 8.9 9.7 7.2 8.6 extension Hardness (IRHD) 63 63 62 61 Taber abrasion 0.1345 0.2202 0.2459 0.1454 lo~s (g/1000 ~ ;
cycles) ~-The rubber in column 1 above contained no recycled rubber. The rubbers in columns 2 to 4, all contained recycled rubber, that of column 4 being made in accordance with the invention. It will be ~een that the tensile strength of rubber 4, although lower than that of rubber 1, is superior to that of rubbers 2 and 3. Rubber 4 also has satisfactory abrasion resistanceO
: . :
.
.
Claims (10)
1. A method of converting vulcanised rubber into finely-divided vulcanised rubber which comprises the steps of:
(1) contacting vulcanised rubber with a fatty acid;
(2) contacting the product of step (1) with a solid alkali;
(3) forming a dispersion of the product of step (2) by passing the product of step (2) together with water through a disc mill, and (4) removing the finely-divided rubber from the dispersion.
(1) contacting vulcanised rubber with a fatty acid;
(2) contacting the product of step (1) with a solid alkali;
(3) forming a dispersion of the product of step (2) by passing the product of step (2) together with water through a disc mill, and (4) removing the finely-divided rubber from the dispersion.
2. A method as claimed in claim 1, in step (1) of which the vulcanised rubber is comminuted or shredded and the resultant comminuted material is allowed to absorb up to 15%
by weight of the fatty acid to plasticise the vulcanised rubber.
by weight of the fatty acid to plasticise the vulcanised rubber.
3. A method as claimed in claim 2, in which the fatty acid is oleic acid.
4. A method as claimed in claim 2, in which the plasticised vulcanised rubber is formed into sheets.
5. A method as claimed in claim 1, in step (2) of which the product of step (1) is dusted with the solid alkali.
6. A method as claimed in claim 2, in step (2) of which the product of step (1) is dusted with the solid alkali.
7. A method as claimed in claim 5 or 6, in which the alkali is sodium hydroxide.
8. A method as claimed in claim 5 or 6, in which the amount of alkali used is 2 to 25 parts by weight per 100 parts by weight of rubber.
9. A method as claimed in claim 5 or 6, in which comminu-tion of the rubber is carried out during or after the contact-ing of the rubber with alkali.
10. A method as claimed in claim 1, in which the finely divided rubber in step (4) is recovered as a dry powder.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB14673A GB1452745A (en) | 1973-01-02 | 1973-01-02 | Rubbers |
| CA189,037A CA1029889A (en) | 1973-01-02 | 1973-12-27 | Treatment of vulcanised rubber |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1055649A true CA1055649A (en) | 1979-05-29 |
Family
ID=25667444
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA291,725A Expired CA1055649A (en) | 1973-01-02 | 1977-11-25 | Treatment of vulcanised rubber |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1055649A (en) |
-
1977
- 1977-11-25 CA CA291,725A patent/CA1055649A/en not_active Expired
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