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Patented Sept. 24, 1946
-
_
2,408,296
[UNITED STATES PATENT; OFFICE ~
.
2,408,296
’ PROCESS OF RECLAIMING' RUBBER
Frank Harris‘s Cotton, East Barnet, and. Percy
Albert Gibbons, London, England; said Gibbons '
assignor to said Cotton
No Drawing. Application August 13, 1943, Serial
No. 498,576. In Great Britain July 3, 1942
8 Claims.
,
1
’
(Cl. 260-720)
,
. This invention relates to a process of reclaim
ing rubber. The objects of the invention-are to
achieve a more rapid plasticisation of vulcanised
'rubber and a more complete recovery from vul
canised rubber waste by a more rapid process O:
than heretofore with fewer steps and less ma
'
'
According ,to a. subsidiary feature of this in
10 there may be added to the‘ softened material a
ber into a ?nely dispersed compounding ingre
>
claims.
vention, at the later stages ‘of the grinding and
heating, operation (or alternatively at an early
stage of the grinding and heating operation)
chinery. Subsidiary aims of the invention are
to conserve materials by converting the textile
?bres frequently associated with vulcanised rub
dient.
peptizers, as this term is described, for example,
in Industrial Chemistry, 1935, volume 27, page
1317 et seq., “Hydrazines as rubber softeners”;
and they will be so denominated in the subjoined
solid-pulverulent powder of the nature of a ?ller
which is absorbedby the rubber ?rst softened
and which thereby assists in‘ thegrinding and
.
This invention includes a process of reclaiming
rubber from vulcanised rubber goods including,
composite material-containing vulcanised rubber
and fabric (like. used tyre covers): which consists
in treating the lmaterial in pieces to heat andto
frictional agitation with- grinding, and shredding
softening of any unpl-asticized particles of vul
canised- rubber that may be present.
‘ '
In carrying the present invention into effect,
the tyres or other forms of rubber scrap are ?rst.
inspected,‘ and sorted into grades, and large
stones, vnails, metal and other foreign materials‘
in. a closed vessel with a controlledquantity of
oxygen, air or other autoxidation promoter sur?
are removed by hand or by mechanical’ means.
cient to allow only the initial desirable autoxi
dation to proceed and to ensure softening of the
vulcanised rubber, the temperature of the mass
being raised to the region of 1802300? C. and
Pneumatic tyre casings arevfreed from metal
either by cutting off the beads or otherwise.
The tyres or other formsof waste rubber are
then cut into suitable sections for, subsequentv
preferably towithin the neighbourhood of 220° C.,
after which the softened mass is subjected to the 25 mechanical treatment. Thus pneumatic tyre
calendering and like processes customary with ‘
casings are conveniently cut by large shears into
raw rubber.
sectionsfrom 2 to, 12 or more inches in length.
;
according to the capacity and mechanical
Preferably the pieces of material to be treated _
' are subjected to preliminary heating to about“
strength of the grinding machine described later. .
150". C. to 190° C. This ‘may be done by direct
v steam heating or it may be done by heating ?rst
in hot water and thereafter in a closedisteam
pan. Preliminaryheating is unnecessary, when I
‘The cut tyre sections orpother forms of wastev
rubber may then be tipped into a tank of water
preferably at 80° to 90° )C., and'maintainecl at‘
that temperature vby wastesteam from the next
the raw'material is in the form of ground waste
vulcanised ' rubber.
'
‘
part of the process.
>
'
’
other formsiof waste vulcanised rubber are fed 9
to a steam pan'or steam-jacketed autoclave pref
vIt is‘a feature of this ‘invention that the pro?
portion of, oxygen; air “or other 'autoxidation pro‘
moter ‘present ‘when the pieces ‘are being. sub?
‘jected to preliminary heating'and are later be
ing’ subjected to frictional agitation and heat is
carefully controlled to avoid resini?cation of
erably ?tted with one or more boltless quick-op- .
crating doors. Therein the waste rubber, which /
mayor may not contain cotton fabric, is heated
vto about 150° C.—l9_0°> 0., by live steam. This
partof the process serves two objects, viz., ?rstly,
to reduce the strength of the rvulcanised rubber
and cotton, thereby lessening the strain it will
the rubber while ensuring the desired softening.
This invention‘ also includes‘a process as in-'
dicated above in which there is added‘ to- the ma- ,
terial under treatment a catalytic softening agent
,
When- warmed througlnthe tyre sectionslor
'
-- _ impose on the grinding machine used in the next
such as phenylhydrazine, ‘thio'ph'enol, aldol-a- ,_
stage; secondly, to ensure a high temperature at
naphthylamine,
the beginning of the next operation, so that the
desired maximumetemperature may bejreached
as quickly as possible. The steam exhausted
from the pan during this operationgoes to heat‘
aldol-p-naphthlamine, ' mer
captobenzthiazole,’ xylyl mercaptan, or naphthyl
?-mercapt'an, which ‘catalytic agent, while the
rubber is in a state of mechanical stress, ac
50
celerates that desirable form of oxygen attack
which causes softening of the rubber, but helps
the water employed atthe previous stage. , - The
preliminary step of heatingv in hot water may be
to suppress the secondary form of oxidation'
which leads to resini?cation or perishingof the
rubber._' '_These"s_oftening agents‘are known as
omitted if desired._
I
c '7
~
The hot tyre sections or other forms of waste
55
I-rubber complete with cotton fabric, if any, are
2,408,296
3
4
discharged directly through a chute or via a con
veyor belt to a large internal mixer of the Bridge
perature is reached in the mixer, a proportion of
a dry powder such as gas-black, soot, china clay,
Banbury, Shaw Intermix, Baker-Perkins Uni
versal, or other similar type, suitably modi?ed,
light magnesium ‘carbonate, kieselguhr, commer
industry for mixing rubber compounds and grind
ing waste rubber.
In such known machines it is the usual prac
tice to cool the mixing cylinder, the rotors and
other parts of these machines by means of water;
but in this process the jacket, rotors, etc., are
heated by means of high temperature steam,
super-heated Water, diphenyloxide" or other- me
powder is rapidly absorbed by the rubber ?rst
softened (e. g. the friction and skim-coat rubber
of a tyre carcase), with which it forms a tough
mix. This tough mix immediately begins to Work
cial silica, or whiting may be added, The pow
?tted with two rotors and used in the rubber C1 der may with advantage be preheated. This
with more effective friction than the softened
rubber could previously exert, against any un
plasticised vulcanised rubber particles. The tem
perature; in the mixer again rises, and in a short
time the» mix is found to be substantially homo
dium to a temperature of 130° 0.4.60“v C. or high
er, cooling being reduced to a minimum by lag
geneous.
ging the jacket and all parts lending them.
selves to this protection. Alternatively the mix-
The amount and nature of the dry powder
requisite at this: stage is dependent upon the
toughness and degree of ageing of the initial vul
canised' rubber. In general the ?ner the par
ticle size of the ?ller the greater its effect in
causing internal friction and heat; the older
and softer the vulcanised waste employed the
less powder has been found necessary. Quanti
ing chamber may be raised to the requisite tem
perature by preliminary working of a batch or
by direct heating.
Within the mixer, the hot
waste rubber is. subjected under heat to the. me
chanical stress resulting from grinding and mix
ing; a. small controlled quantity of oxygen or
air or other oxygenating gas is admitted in order
to bring about desired softening of the vulcan
ised rubber without causing undesired resin
formation. Directly the hot waste'rubber begins
to grind in the heated. internal mixer, friction
between the rubber and. the moving parts of the
machine, and internal friction inv the rubber and
fabric itself, causes rapid rise: of temperature to
ties up to 30% on the weight of the original scrap
have been successfullyv employed with tough.
tyres. The total period of grinding and plas
ticising varies with the charge and also with the
age of the vulcanised rubber under treatment,
but is of the order of'30 minutes.
In a somewhat similar way‘ simultaneous recla
30
mation and compounding may be effected by in
a peak between 190° and 250° C. depending upon
troducing into the mass of- waste rubber in the
the type of waste, the e?iciency of the machine
employed and theconditions of‘ the processing.
With improved methods of heating and of pre
caution against heat losses, peaks beyond this
mixing chamber and at the appropriate moment
range may be expected.
ebonite stock directly from waste vulcanised rub‘
ber and scrap ebonite, both in- the form of large
thev fillers or other material desired to be com
pounded with the reclaim. This is particularly
applicable to such cases as the preparation of
subjection of thevulcanised rubber to mechan
ical stress during heating greatly activates it to
wards oxygen attack and it begins quickly to
soften. Any residual moisture is driven off, and
pieces.
is allowed to escape from the grinding machine.
The attainment of the peak temperature with
in the mixer indicates the approach of the end
of‘ e?ective grinding. It is usually found that‘ at
this stage some at least of. the rubber has mark
edly softened, most if not all of the‘ textile fab
ric (if present) has disintegrated, but a propor
'
The material‘ is discharged from the internal
mixer in a- plastic condition (preferably after the
addition of a little water, 1%—3% just before
discharge or spraying with water to cool-by
latent heat or steam—and to protect the rubber
- against rapid oxidation and possible in-?a'ming)
and may be immediately sheeted and simulta
neously re?ned on closely set rolls such as’ those
of the type commonly used in re?ning reclaimed
rubber made by the alkali process. Where the
presence of metallic or other solid impurities
tion of the rubber may be left as discrete par
ticles in a plastic matrix.
With many types of waste vulcan-i'sed rubber it
makes this necessary the plastic material may be
is‘ desirable, though not essential, to introduce
into the mixer, for example along with the‘ pieces
of tyre or other rubberscrap; a small quantity
of a catalytic softening agent or peptizer which
readily forced through a. strainer of the, worm
extruder or hydraulic extruder type. The re
sulting reclaimed rubber is preferably scraped
from one of the rolls in. the form of’a thin leaf
serves: (a)‘ to simulate the desired form of oxy
or sheet. by means of a robust doctor blade
gen- attack which leads to plasti-cisation- of the
pressed against the roller. The thinly sheeted
vulcanised rubber, and (b) to’ help to suppress
reclaimed rubber may then be rolled, layer upon
subsequent undesirable oxidation. The most suit
layer, upon a rotating drum from. which it can.
able catalyst yet- found is phenyl hydrazine which 60 later be cut in the form of large rectangular
may be used in for example the proportionof
sheets‘. These sheets may be dust'ediwithtalc or
0.05% to 1.0% according to the nature of the raw
‘ china clay to reduce surface tackiness. The
material. Other catalysts are thiophenol, a-ldol
sheetingv rolls may be enclosed in a casing to
a-naphthylamine, aldol-c-naphthylamine, mer
captobenzthiazole, xylyl mercaptan and naph
thyl-B-mercaptan. Several autoxidation cata
which can be fed steam or an inert or reducing
65 gas in order to suppress local; surface oxidation
lysts and reducing agents may be employed to
gether. The introduction of a reducing gas such
as sulphur dioxide oran inert gas such as car
bon dioxide, steam or the decomposition products 70
of. ammonium carbonate, may have advantage in
of the hot plastic mass.
The process of‘the present invention is illus
trated by the following. examples. ,
EXAMPLE I
The; treads were removed from a large num
assisting to suppress undesirable resin-forming
ber of tyres and‘cut‘ into sections‘ each weigh
oxidation during the latter stages of the grinding
ing 2-4 lbs. 110 lbs. of this Waste tread were
and'mixing process.
'
weighed into two perforated iron kettles and the
At or near to-the stage at‘ which peak tem 75 latter charged into a wellelagged steam pan‘.
2,403,296
5
The door was closed by means of. bolts and the _ the tight nip of a two-roll mill of the type nor
mally employed in the rubber industry, the rolls
waste rubber raised .to'a temperature of 174° C.
being hot and geared to vfriction speeds. The
by introducing superheated steam at the highest
pressure available,‘ viz. 80 lbs., per square inch.
reclaimed scrap immediately formed a thin ?lm
round the faster roll and after four passes was
7, At the endof 30 minutes the pressure of steam_
de?ected by means of a doctor blade on to a re
~ in the span was rapidlyreleased and the pan ‘
t
volving drum and built up into sheets approxi
' _ opened as quickly as possible.
mately one inch thick. The ?nished reclaim was
vThe hot and dry scrap was transferred imme
then cut lengthwise, stripped from the drum and
diately to the inner chamber of a No. 3 “Bridge
Banbury” internal mixer. In continuous produc- 10 dusted with clay or talc to remove surface tacki
tion everyrpreca'ution would be taken to‘ ensure
.
ness.
.
1
e
>
V
a
7 ~ _
maximum temperature of the waste and mini-
In appearance, texture and odour it was dif
mum heat losses during the transfer from pan
?cult to distinguish‘the product fromreclaim
to mixer.
prepared by old established methods.
it
_
i
Y
vThe chamber of the internal mixer, contrary 15
' “to the usual practice,>had been raised to as high
.
V
, EXAMPLE 2
a temperature as possible by directing steam
under pressure into the walls, rotors, and sliding
r
_
_ _
Anumber of test rl‘uns Were madenfoer Whwh
the general procedure was the Same as. that
door. Various devices were employed to raise
describedin Example 1- A Small quantity of a
and maintain the temperature of the mixing 20 Catalytic vSoftening agent or peptizer was added
chamber,
‘
‘
' '
‘
'
to the hot mass in the mixing chamber and was
The No. 3 “Bridge-Banbury” mixer has a feed
hoppefabove the mixing chamber and connected
thereto by a vertical rectangular throat in which
found to aid the process of plasticisation, reduc
mg the. time ‘necessary in the mixing chamber
. and the W°rk1ng_0n the lee?ng mills; the “tail
' slides a “floating weight” coupled by a vertical 25 ings” or unreclaimed particles were softer and
'(piston rod to- a piston in a pneumatic cylinder
_ the. proportion of them much reduced.
above the hopper_ The downward pressure on,
I the floating weight may be about 60-80 lbs. per
square inch.
The -.
quantity of peptizer necessary did not exceed
1%, a quarter of this giving most. Satisfactory
The floating weight moves up and
results-
down during the mixing and exercises a pumping 30
action. ‘The floatingweight acts as a con?ning
d‘o'or‘for the contents of the 'mixer_
_
‘
.7
.
i
-
_
The peptlzers employed were phenylhydrazme,
Xylyl mercaptan andmercaptobenzthiazole-_
In the course of these tests the additionof 0.1
to 03%] ammonium carbonftte was tQuQd to ‘be '
The hot, dry and softened sections of waste
tread were rapidly reduced to a ground mass
Pseful 111 suppressmg uhdeslrableoxldation dur
and exposed to the action of a controlled amount 35 me the attual mastwatwn process, the advisa
of air introduced into the mixing chamber dur-
bihty 01‘ otherwlse of Such protection being indi
mg the‘ process by the pumping action of the
cated by the character of the odour arising from
floating weight, ‘this air being the small amount
the mute!‘
which entersv around the weight due to the loose
‘EXAMPLE 3
?t of member in thethroat. and ?lls the avail- 40
In this test 100 lbs. of large sections 'of debeaded
able space in the mixing chambet- WIth the
whole tyres were charged into the steam pan,
, latter fairly fully charged (as, indicated in. the
the ?nished'reclaim containing the Whole of the
Examples set totth in the present Specl?catlon)
decomposed fabric as a ?nely dispersed com
and with th_e_custQmary3cti°n ofthe apparatus,
pounding ingredient. The procedure was sim
the an‘ entering will contam Oxygen amountmg 45 ilar to that described in, Examples 1 and 2 with
the following modi?cations:
Best results-were obtained by the addition of
0.5% of phenylhydrazine to the mass early in
the process and, 0.3% of ammonium carbonate
_. ' to a fraction ofrone per cent of the rubber by
-; weight-—usually less than 0.40 per cent. Largely
due to the ‘friction ensured by the airpressure
f t of 60 lbs., per square'inch on the floating weight,‘
' the temperature rose during this stage from 140° ; 50 towards the end tocounteract the increased tend
totthe neighbourhood of 220° C.
ency' to‘ undesirable’oxidation possibly due to the ‘
The relation...
fairly high proportion of fabric present.
_ . betweenythe temperature recorded at the socket
Although» the temperature reached was some
andvthe actual temperature of the mass of waste
what lower than in Example" 1, viz. ‘210° 0.‘, the
. rubber was ‘determined by discharging‘ the stock
'1 ‘ at a‘ known steady socket temperature and ob ~55 plastic mass discharged gave an‘ excellent'lthin
?lm ‘of reclaim at ‘the ?rst pass through the
serving the temperature of the hot' stock by
“means of thermometers plunged into deep in- ' leafers.
e, A yield of 90% of ?rst grade'reclaim was ob
cisions made in the soft mass. As the" result
of shredding and grinding at hightemperature ‘ stained, the greater part of the remaining 10%
whilst exposed to the action of a limited supply 60 serving as a useful second grade reclaim.
of oxygen, the Waste rubber plasticised and at
EXAMPLE 4
‘ the end of a period not exceeding 30 minutes in
any, of the test runs performed, the waste- was
discharged in the form of large plastic lumps‘
' ' similar in appearance to a compounded carbon
black rubber stock.
For this test 120 lbs. of cable strippings were
cut into long lengths and subjected torthe same
65 procedure as described in Examples land 2 .with
‘y the following modi?cations:
, During the ‘tests a number of methods were
employed to prevent undesirable oxidation occur- _
'- ring when thevery hot reclaimed rubber was‘ '
discharged from the mixer, the addition of a little 70
‘water just'before discharge being found the most
effective by cooling and'simultaneous production
of steam.
'’ The plastic mass was passed through a sheet
'
'
_ As the waste was in the form of tubes of rela
tively thin section the period of preliminary heat
ing in the pan was reduced to 20 minutes. It is
a feature of the‘ process that during the proc
essing the temperature of the waste in the mixer
passes through a maximum and this, together
with the massing indicated ‘by the thumping of
the floating weight, serves as a guide tow the com
ing 'mill and then transferred___immediately to 7s pletion of the test.‘ It was found possible ‘with
7
cable \strippings'to reduce the/period-in'the'mixer
‘and although this sheeted “and- i'ndlcatede- some
to~~20~minutesw There/was every '~ indication that~ -' measure‘ of ‘reclamation
was byenc means com
with- the achievement of'higher initial; tempera= ~ *1 plete.
tures ‘ and a‘ more1 rapid - rise ~the~period “in the
~ Pure‘ oxygen was then conducted from‘a reser
‘ ‘mixer could'be-appreciablyreducewin‘all cases:
~
"The resulting-plastic mass'sheetediwell at the-~
?rst pass "and'»~the second gave--a-recla~im> com
A parable in ‘appearance with any ‘prepared by '~' ~ '
'
other-processes.
'
'"
voir in ‘which itwas'under a pressure of‘40L-atmos
phere‘s‘to the mass of~waste via a vtubei-in the wall
of the mixing-‘chamber? Although the-amount
ogfioxygen- entering-'irepresented--1% byweight on
the waste rubber, ' only a ‘relatively: small ~amount
=1‘ ~A yield ‘of ‘88%'~of ?rst *grade‘reclaimswas ob-“10-“of‘ this came'into actual contact witlr‘the-waste
tained, the balance forming a useful~1~second"\“e 'under the conditions of the‘ experiment.
‘-’ grade.
~ '- "Almost immediately'the- ground massmerged
With- heaivycables- it ~was-found that ‘the addi
into a'plastic mass; showir by-the-movement of
the weight piston, and the temperature rose
the plasticisation processgand gave a softer prod--15 \» rapidly~by about'10°*C. -At~the'*énd of~~15 min
tion of 0.-2%--'of'catalyticrsoftening agent aided
. not, which could be processed with greater ease»: ~ utes- a‘ "plastic mass - was dischargedi which gave
' " ' Thetemperature'of the cableestrippings in the - Manexcellent ?lmof'reclaim-"at'thel?rst pass: The
pan Was in‘ the neighbourhood of 'l70f’fCgand in»-~‘~-~~'wholepro;cess from cold groundwaste to'the ?n
..
. .20
i
ished' ro'llsofnervy reclaimoccupied only’20 min
utes. "I'he yield-amountedito almost 100%.
. ._ ?/EXAMPLE 5
" the‘mix'er:200° C,
~
115 lbs. of 'whole'red pneumatic'tyre inner tubes
.EXAMPLE 8
"without‘metal valves were'charg'ed into the pan " 1>”- 2,000 grams of-vaiblended‘ebatchiofwdebeaded
and'exposed to steam ‘at 171°“Cjfor 20 minutes.‘
The procedure then» followed that described in‘
whole tyres ‘cutrintosecti'ons eachweighing 150'
' 250 grams were ‘placed on a-metal grid: and low
‘ Examplesl ‘and—2,"the plastic massi being dis-- 25 ered into ‘a; steam'jacketed pan=~ The lid was
“charged from the mixer at the'e'nd of 24 min~ ' bolted. down andtheawastel-rubb'ereraised to a
lites.‘ The‘ temperature reached "in the mixer
temperature‘bf 1769C. by'mearis-of high-pres
_ was in the neighbourhood of 210° C.
'
sure steam-~‘(115-‘125 "lbs. per square‘ inch) vto
=T-he 'resultingmlas?ic‘ mass give ‘a thin 116N130 ‘which ‘the waste tyre'sections wereexpo‘sed for
sheet onthe'leafers and an 84% yield of 'reclaim' ' 30~minutesl A free ?ower-steam through the
~r excellent‘ in' appearance after three passes. The
pan in the'?rst instance’removedthe-air present.
' bulk of the remaining 16% served as a useful sec
At the end of this period the ‘pressure of steam
-' ond'grade reclaim.
'
in ‘the-inner pan was-rapidly- released; ‘the pan
opened as qui-cklyasv possible and" the that dry
I‘ The’ addition of‘a verysmall'q‘uantity, 0.1%,
'
.
.
,
.
.
‘3"
waste» transferred» to van intemal- mixer heated
by the methods described in the ‘foregoing’ exam
‘ -*ofplasticisatiOn-but
’ ~of‘v-catalytic' softening
wasagent'j
‘not essential.
aided "the ‘process» 1 ~
'
EXAMPLE 6
ples.
The'temperatures of themixing chamber rose
from
142° C_-to the neighbourhood/‘of 190° C. at
lbs. of bicycle inner. tubes for each-charge. The. ‘*0
.
the
end
of 14’ minutes. ‘At this point~100 ‘grams
.maximumgl-temperatures reachedain the ~~mixer,<...
(‘5 %~)' of hot carbon black of ‘fine particle ‘size and
. rangedbetween-190'i and 220° C.
./ .. A.series- of. test runs. Was'made employing 120‘ .i i _
_
_
> 2 After the initial period of.warm1ng
in
vthe pan.
,. “hi gh’reinforcin g p ro p ertieswas‘introduced‘in two
,it was found possible to“ complete. theprocess in». 5 equal' portions into ‘the mass of ' Waste .rubber.
The grinding effectincreasedand ‘the ‘tempera
the mixer in periods of .less than. 17 minutes.
~~ture rose‘ rapidly to-t-he neighbourhood of 200° C.
. In all-.cases »an.-exce1lent, nervy reclaim was ,.
“As customary in‘all" these-examples a controlled
_ obtained.- readily,
pl‘Odtlct being’
,-..-amount of-lair was
.to
cham
similar tomasticated raw creperubberin its“, "e-"~
'0
:1:0
'f'v
1h
'
_- behaviour-Yon the sheeting mill. Theinclusion of a , ‘ b r durmg the pr cess
‘ smallproportionofcatalyticsoftening agent, e. g 50 Was-added‘, 0.75% with
% 0 'pheny
ydra'zme
the‘ hoti'waste land‘0.25%
with
the
carborr'blac'k.v
The best zresu'lt'was ob
0.2% ofphenylhydrazine; led to avery soft stock,,.»..j..
.
beingobtairied. .Thevulcanized'product was sim-. ‘,
;
ilar to that obtained in the absence-0f .the- cata- ‘
tained using these proportions but a; much’ lower
- proportion would‘ be 'suf?cier'itlyfe?ectiv e.
~Experience~has shown that‘better results are
‘ "obtained; when‘:the"addition"of carbon. black is
I a What lower modulus.
Re?ning was unnecessary with reclaim pre» _I_ done m'orett‘gradually "over ‘an’ extended-‘period of
pared, by this: process from'rbicycle inner tubes._"__, ._ time, better‘ dispersion ‘and grinding ‘action be
ing‘thus'achieved.
Thisappliesequally; to gas mask facesand sim
ilarwaste rubbers. _-The yield :was. almost 100%. ,6. “When itheipla‘stic mass was. discharged at the
0 end’. 01230 jminutesipand.transferred to'the tight
"nip 'of'a‘two-jroll mill‘, a'thin smooth sheet of re
A‘small .internal .mixer was usedrforsthe test; "claim with-1 ‘a matt ‘?nish and‘entirely ‘free from
I.» runs represented'by this-example.- rTherrraw ma. terial-was ground? waste “tyre. tread’ and,‘ no pre
7
..
_
evidence 'of ‘?bre was obtained; It. ‘was extremely
‘easy to‘ handle on'the mill‘ and very ‘easily'rolled,
liminary heating ,was..performed.-~~- 2600,,grams b5 sheete'd'and plied. “Tailingsj’i; e.iunrecl'aimed
of the cold. groundlwaste was-,charged-into the v particles, were largely reduced.
. mixingnhamber of a small internalmixer capable ' "
‘Similar results were obtained using ‘such ?llers
I -of .accommodating..a.maximum .of ‘3200 grams of
" ' as the‘ china clays of ‘?ne particle'sizeof the type
.' the like waste. Theinitial temperature. of the l- I ..repiresen_ted by‘ the proprietory' product- f‘Stock
._ .mixer was 152°. C. ‘.‘Thetemperature. fellas the 170'. 'alite?.’ Qkieselguhrj'andlight. magnesium- carbon
. cold wastewas introduced and then roseto the
' ‘neighbourhood of- 190<200i> C. as. the‘ grinding pro
' ceeded, ‘full air pressure of. 80 lbs. per square inch
. ‘ate; with‘thelast named,.a..much.greater.stiffen
ing effect Was observed leading to increased fric
l
.
tion by. more thorough grinding _. and the. main
..tenance cf-the ‘plasticised scrap at itsmaximum
being
A sample
applied
was
toremoved
the‘. floating
at the
"weight.
end of 10 ~ minutes
7
75 ‘temperature ‘for longer periods.
2,408,296"
. ~
EXAMPLE 9
10
2. WHOLE TYRE RECLAIM (INCLUDINCYFABRIC As
‘a’
COMPOUNDING INGREDIENT)
1000 grams of sections of debeaded whole tyre
and 1500 grams of ebonite scrap in large ‘broken
Speci?c gravity _____________________ _'__' 1.23
pieces were heated to a temperature of 174° C.
:by exposure for 30 minutes to high pressure
Ash
steam, as previously described, and transferred
Chloroform extract ___; _______________ __ 21.3
immediately to the hot chamber of the internal
Cure
mixer;
_
-_
14.4
Acetone extract ______________________ __
'
9.9
’
.
,
The temperature rose from 145° C. to the neigh 10
bourhood of 205° C. at 10 minutes and a plastic
mass was discharged at the end of 19 minutes.
‘
_
A
'
25 mins.
@ 141° C.
‘
‘
.
portion of added sulphur being based on the rub
ber hydrocarbon content of the reclaimed whole
tyre only. Sheets were press cured at 141° C. for
various periods according to the vulcanising char
acteristics of the mix.
,
B
-
. days @ 70° C.‘v
20
‘The stock was made up into mixes, the pro
1
mins.
@ 141° C. Aged samples 11 '
Very good dispersion of ground ebonite,
throughout the mass of the reclaimed whole tyre
had been achieved although small particles, easily 15
broken by grinding, could be observed.
When transferred to the leafer the compound
showed a markedtendency to roll in the nip and
give a‘. rough vsheet of mixed reclaim and dispersed
ground ebonite.
A
B
Tensile strength (lbs.
per square inch) _____ __
>
-__
2, 000
510
Modulus at 300% ______ . _
1, 040
Elongation at break
420
150
.......... __
1, 800
0
760
50
l, 800
______ __
3. RECLAIM FROM CABLE STRIPINGS
Speci?c gravity _______________________ __
Ash
1.39
'
_________________________________ __ 35.3
'
Cure
A
'
Sheets of ebonite of good quality were obtained
without difficulty. These were examined bytwo
B
25 mins.
@ 141° C.
A
B
35 ‘Zr 25 I
mms‘
Aged samples 11 '
@ 141° 0-
days @ 70° C._
ebonite manufacturers and pronounced very- sat- .
isfactory.
'
‘A
.
Simultaneous reclamation and compounding of
‘ waste rubber and ebonite scrap was thus achieved
Tensile strength (lbs.
.
per square inch) .... __
2,500
660 or 540
2,220
760
Elongation at break--.
500
330 or 380
330
100
Modulus at 300% _____ __
1, 200
640 or 460
‘680 '
130.‘
2,000 ________ __
by the new process in less than an hour, no initial
preparation of either scrap being necessary be- ‘
yond the cutting of the whole tyre into sections.
Tests'have been’ made on representative sam
ples of reclaim obtained by the process of this
invention, the results of which aregiven below.
In these tests, the following mixes were employed
the ?gures being parts by weight:
An indication of the good ageing properties of
reclaims prepared by the process of this invention
is given by the retention of tensile properties after
ageing for 11 days at 70°. C.
Processing tests made on the reclaim have
yielded the following data:
(a) The mixing mz'ZZ-.-—The reclaim is easily '
handled on cold or slightly warm rolls. It becomes tacky and difficult’ to remove if the rolls
A
B
Smoked sheet rubber ______________________________ _.
35. 45
.... ._
‘Rnnlnim
40. 00
100. 0
2.50
____ ._
17. 65
____ _.
"
are hot and on a tight nip transfers immediately "
___.
Zinc oxide
___.
Carbon hlnnlr
_____ __
___
___
Stearic acid _____________________________________ ._
l. 70'
“Nonox X” antioxidant
____ .
_60
Sulphur ___________________________________________ -_
Memapfnhenvthiamle
1. 75
5. 0
_ 35
____ _ _
100. 00
105.0
_______ __
The results obtained using particular speci
mens of reclaim will now be given, preceded in
each case by a description and analysis of the
specimen of reclaim used.
to the back. roll.v On opening the nip and 0001- J.
45 ing the rolls it can be readily removed; this ‘is :'
facilitated by the addition of a small proportion‘
of crude rubber.
(b) Compounding.-—The reclaim mixes very
readily with crude rubberand materially aids‘ '
50 the dispersion of added ?llers. Mixing time is "
reduced.
(0) Extruding.--Uncompounded reclaim ex
trudes readily and smoothly. Compounded with
proportions of “Witbro,” a vulcanised oil type of
55 rubber substitute, smooth tubes of large diameter
were extruded with less di?i'culty than standard
stocks for extrusion. The machine should be I
1. TYRE TREAD RECLAIM
maintained just'warm.
Speci?c 1 gravity __>_ ___________________ __
Ash
1.16
_________________________________ __ 10.2
Acetone
extract
_______ _1 _____________ __
9.6 '
Chloroform extract ___________________ __ 15.8
A
.
with
>
sulphur
60 only or in a, fully loaded mix the reclaim stocks
moulded readily, flow in the mould being facil
itated by the character of the reclaim. Soft rub
ber vulcanisates and ebonites were prepared
A
B
25 mins
15 mins.
65 from similar mixes containing crude rubber and
no reclaim.
B
@ 141° 0. Aged samples 11
days @ 70° C.
Tensile strength (lbs.
per square inch) ..... _l
.
which compared favourably with those prepared
Cure
@ 141° C
.
(d) MouZdz'ng.—-Compounded
2, 480
600
2, 400'
cent) _________________ _ _
550
300
360
600
100
Modulus
(at 300% elon
gation) _______________ ._
1, 400
2,000
______ __
Elongation at break (per
.......... .-
We claim:
1. A process of reclaiming rubber from vul
canized rubber scrap, which comprises subject
70 ing a quantity of pieces of scrap material in sub
stantially dry form to intense mechanical action
in a heated. internal mixer, in the presence of
oxygen amounting to a fraction of one per cent
by weight of the scrap material, for a period of
75 from about ten minutes to about thirty minutes
2,408,296 ,_
ll
12
.,
until the temperature of the" mass rises, as a re.- . .i ized rubber scrap, which-comprises subjecting a
sult of'such action, to a, peak jof between about‘
190° C. to about 250°"C.';" discharging the ‘rubber;
quantity of the scrap material'in substantially
dry form tointense mechanicaliaction'in aheat
and quenchingthesame-atabouttha‘same moat :2 Ned internal "mixer, ins‘the presence of'ioxygen
:3
amounting to: a fractionhof one‘ per- cent by:'; "
ment td=coo1.and_protect_itlagainst-rapidoxida
tion. ‘Mr
weight‘oflthe'scrap material,‘ for a" periodv of:
2. A process. of reclaimingwrwbberrirom fvul= '~-‘-‘ from about‘ *ten' minutes "to? about "thirty minutes? '
canized rubber scrap! containing textile ?bers,
until the'temperatureofzthemass rises, as a re4
which comprises subjecting a quantity of the scrap
sult of such action, to a peak at between about‘
material in substantially dry form to intense me- 10 190° C. ‘and about 25090.; :creating .a'non-oxidiz
chanical action in a heated internal mixer, in
ing atmosphere‘ ‘ in: theta. mixer ‘during '1 the: latterl
the presence of oxygen'v'amountingzto a fraction
rubber;.q:and
stages ofxithe quenching;
:“grinding {process}
the‘! same
discharging
at about the:
the;
of one‘per ‘cent by weight: of the scrap material,
for a period-"0t from aboutten-minutes vto~about-~ .same ‘moment to“. cool and‘ protect" it ,zagainstiiw" ‘
thirty minutes until the temperature .of. the-mass 1'15: ,rapidnxidatio'n; : ."i t
rises, as a result of: such action, to a peak at "be-1*
6. A process ofsreclaiming .ruhber'fr‘om Vulcan-2:
tween‘ about/190°: C." and about 250?v cg‘a plastic)‘ ., .ised scrap which: comprisestsubjecting-aquantity»
mass is produced,‘ and the ?ber hasodisintegrated
._ ,of the‘s'crap :material in substantially ‘dry form ton"
Into ?ne particles which,areimpercep-tibleq in the
intense .ime'chanical' "actiontinia heated iinternali
..
mass; discharging the rubber; and quenching 20 mixer in the presence of oxygen, amounting. to. j "
the same at about the same momentctmcooliandt 4.5a fraction of one percent b‘yiweight oftthescr'anvv .
thirtyzhiinuteszuntil
for a periodiofifrom the
about:ten:minutesrto‘about?
itemperature of.'thetmass~ 1'4‘
3. A process of reclaiming rubber from vulcan
ized rubber scrap, which comprises subjecting a
rises as the iresult'oilisuc'h actionwt'o :a peak at I c‘
protect‘. it» againstrapid .oxidati0-n.- -- g _- c >
quantity of. the scrap-material>in~~substantially 25'
dry form to intense mechanical action in a heat
ed internal; mixer; inuthe‘ presence of oxygen
betweenxaboutl90°
charging
the rubber;Ciian‘d
and quenchinga'tthes
about-.250q C.',:dis'—
sa'm‘en. :- :
amountingrto airaction'of. one percent by weight
of the‘sc'rap'material,‘ until the temperature of
againstirrapid
at about: :‘the:‘same
cxidations
momentito;
‘:7
cool sandprot'ect it "
a peak atbetween: about. 19030. and ab'0uts250?
" a quantityaof. the iscraprmaterial :to a preliminary, \ .'
'7. A process?ofvfreclaimingrp
rubber scrap, which comprises
rubber; subjectinga.v
from rvulu. .Lt'
the mass rises, as a result of ‘such action, to 30 canized
heating~;to-ia temperature ;of from 'about»150?, C3? ~.
mately-thestage
C.; addingta, solidatpulverulent
which. peak?ller
temperature
at rapproxir
‘is “
to about="1%9.0° Cwbylive'steam:rexhaustingithe?
reached; continuing the mechanical action until
the temperaturetin: the: mixer-1 again :rises an'dia J35
substantially :ihomogen‘eousirmixa isafformedziidis
,
steam;~ immediately‘ subjecting the§mass in: sub-' 1- .Y.
stantially-drygfor-m to intense mechanical-action '.
‘ -~
-:,:,.
1 small
in a heatediinternalmixer,:>inr-the
amount of oxygemnot exceeding
presence
about.of-a
one; . .
at
charging-,:;the.:
about the same
rubber
momentito"‘codltandfprotecti
;;f.iand quenchings‘th'ei sa'm'e
it La.
,per cent by iweight,:of1the:,scrap.~1materia1; until ‘er.’
the temperature .of the-'mass rises, "as-a result; of .15 ~ '
4. A process of reclaimingi'erubber':from
40 isuch action, to a peak ,atvbetweenr.aboutw190,°: C5‘
canizedzfrubberr;scrap: containing. textiles ?bers "" and about 250° C.; discharging the rubber; and
which- rcomprisesr subjecting . a:1quantity.::of:scrap
quenching the same at about the same moment
material ‘.tO? a; preliminary :heatingzto ia'rtempera
.1; to cool-and protect it against rapid oxidation.
ture ofd‘rom 1about:,150.‘?; C. at?) aboutil90° CFUYM
1 8. A process of reclaiming rubber from Vulcan- *
live steam;rzexhausting thessteam‘; immediately-~ _:-ized rubberzscrapwhich comprises subjecting a..;
subjectingratherimass ':in substantially :dry: form
to intens'ezmechanicalzaction;inc'a?ieated interiia
wouantity of. .the'sc'rapmaterial insubstantial-1y
mixer, in the presence of a small amountco'fii
, internal mixer in the presenceof oxygen; amount
oxygeniinot exceedingcaboutionm pen cent by“
:-dry form tOLintense mechanicalacticn in aheated
ing to-‘a fraction of“ one per ‘cent byrweightx'oi :1.
weight-of thezs‘cra-pzmateriahzuntil theit temperaaJ-O; the scrapg~and< together with a small quantity of
ture of; the1mass rises, as-rairesult; of such action
to a peak at between about 190° C. and about
250° C.;_ ,a plastic ‘mass .is'cproduced} and‘: the tex
tile fiber has disintegrated'i'into ?ne’; particles
.-,a peptizenmuntil the temperature of the mass
wrises as‘the‘re'sult' of such action to a peak at ‘
between. aboutr,190‘? C. and aboute250° 6.1;: dis-,
charging the, rubber; and quenching “the-same
which‘ are; imperceptible in'thé mass; ."discharging 153* at about the same momentnto‘ic0Ql.<and-‘protect:it
the rubbergzwandg quenching: thee same r-at‘r-aboutril I
the
rapidsame
oxidation;
wmomentutpr-"cool: and ‘protectit-against
5. A process of reclaiming rubbercfrom VumaI'F-TTS.‘ »
FRANK‘? HARRISS COTTON.
PERCY ALBERT GIBBONS.
- .
: >
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