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Патент USA US2412296

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Dec. IO, 1946.
c. L. sHAPlRo
2,412,296
A METHOD OF AND APPARATUS FOR DEPOLYMERIZING ACRYLATE RESINS
Filed April 3, 1.944
lN VEN TOR.
6dr/ l. Jhd/:fra
4 free/vi y
Patented Dec. 10, 1946
,_
2,412,296
UNITED STATES PATENT ori-'1cEffÍ> .
2,412,296
METHOD‘OF AND APPARATUS FOR DEPOLY
MERIZING ACRYLATE RESINS
- f
Carl L. Shapiro, Beaver Falls, Pa.
Application April 3, 1944, Serial No. 529,390
7 Claims. ’ (Cl. 260---486)
l
2
The present invention is directed to the treat
ment of acrylate resins such as those made from
methacrylic acid and esters thereof.
Resins of the acrylate type have been in use
for some years and they ñnd a considerable ap
plication in molding of various articles, usually
by injection methods. In the course of such
siderable velocity. Therefore, prior processes
were Adependent upon the dissociation, volatiliza
tion vof the product, and condensation thereof.
The present invention also subjectsthe acrylate
resin to temperatures above the dissociation point
manufacture there is a considerable amount of
Waste acrylate resin which is an important factor
temperature used in the treatment is quite high,
being usually above _400° C._ and Aas _high vas
1000° C. According to prior information,> such
temperatures would, necessarily Ycompletely ,de-_
compose the resin to form useless end products.
In accordance with the present invention, the
in determining the cost of the molded article.
It has been attempted to recover the same by
various methods, among which is the treatment
of the acrylate resin in order to decompose and
for formation of the monomer from the resiniñed
mass.V However, it differs` essentially inthat the
depolymerize the same to form the monomer.À It
time of treatment ofthe acrylate resin is__ex-
was accomplished by placing the resin in a suit
tremely short, usually amatter >of _a small'num
ber of seconds. The heating ofthe resin isl in
tense for the extremely short period of time, and
able vessel and heating it to a temperature
usually between 300° and 400° C., whereby decom
position took place and dry distillation was
the time and temperature are so correlatedas >to
decompose the resin to form a liquid, product,
effected. The condensate from the process was
condensed and consisted to a large extent of the 20 that is, a product which after it is cooled isin
monomer.
the liquid state. This is accomplished Without
However, this process was not capable of com
mercial application for Various reasons. The
monomer was quite impure and contained Various
colored substances which were most difficult to
remove. Also, some of the substances formed in
volatilization- of any substantial amount of the
end products, even though the temperatures used
are far above the boiling points thereof~~ _ "
The invention consists essentially in providing
a trough or other container, having at the bottom
thereof a moving conveyor or belt. The Aacrylate
resin in the desired state vof subdivision, which
may be irregular-shaped pieces of relatively‘small
the decomposition operation and contained in
the monomer tended to interfere with the further
utilization thereof in the making of acrylate
30 size, is fed into the intake end of the trough, that
resins.
In order to overcome this, it was proposed to
treat the relatively impure monomer in order to
further purify the same. This was accomplished
by distillation with steam of the monomer and
the condensing of the distilled product. How CJ Cil
ever, it required rather close control of the op
eration, together with a considerable amount of
equipment in order to fractionate the desired
monomer from other substances present. Also,
various difficulties arise where the acrylate resin 40
contains certain modifying agents which tend to
contaminate the monomer after formation.
The present invention is intended and adapted
is, at the point where the traveling conveyor
enters 'the apparatus.
A' layer of _resin isi-so
placed on the conveyor andwater is sprayed
thereon so as to cover the layer of resin. As the
mixture of Water andresin travels towards the
opposite endl of the trough, there is provideda -
direct flame of high intensity, such as an oxy
acetylene type of flame. The flame cuts through
the Water and acts intensively on the, resin;A
depolymerizing the same, and immediately upon
the reaction taking place the mixture on the _con-_v
veyor is moved out of the zone of reaction‘with
very little vaporization of either the water or
the depolymerized product. The mixture is then
to overcome the difñculties and disadvantages of
prior methods and to provide a method of depoly 45 placed in a suitable vessel Where it is allowed
merizing acrylate resins which is simple and effec
to settle to form two layers, one of which is the
tive and which is capable of quickly depolymeriz
ing said resins With a minimum of labor and
apparatus.
_
_
liquid depolymerized resin.
_
'_
.
The process may be controlled so as to givey any
desired mixture of liquid products. It is possible
It is well known thatl acrylate resins begin to 50 to control the time and temperature of the _reac
tion to give the monomer as the principal orvsole
dissociate when heated to a temperature of about
reaction product. However, for the purpose of
200° C., and that the dissociation, if allowed to
proceed for a suiiicient length of time, will pro
the preseni-Í invention it is not necessary nor even
duce the monomer. At higher temperatures, say
desirable in many cases to decomposethe resin
300°-400° C., this action takes place with a 60n 55 t0 the monomer. In a preferred operation of the`
2,412,296
3
,
invention, the depolymerization is caused to» take
place to form a mixturey of polymers of low mo
4
Y
_
.
.
stances, such as plasticizers, other resins, sta
bilizers, and the like. Usually such additional
substances do not interfere with the operation of
lecular Weight, the mixture being liquid in char
the process and most of them are not unduly de-Y
acter. Usually such polymers contain from 2 to
5 acrylate radicals in the molecule. There may Ul composed in the operation. However, if such de
composition does occur, then a simple distillation
also be present molecules of a higher molecular
operation will remove the liquid polymers and any
weight which are semi-solid in character. Be
cause of the presence of the lower liquid poly
monomer which may be present, from vthe addi-`
tional « substances. However, »the heating step is '
mers, such higher vpolymers are dissolved ktherein
vand a liquid product results. Sucha liquid mix
so short Vthat usually. î'additions contained in .
ture has a boiling point above the boiling point
acrylate resins remain in their initial form. Be-v »
of water, and this facilitates the operation in thatì
¿cause of the short time of treatment, there is
very little if any discoloration in the liquid prod
the tendency to volatilize under vthe high tem-V
peratures used is minimized. -Such .a .product 'has' `
the further advantage that in order 'to 'transform '
the same into an acrylate resin, the zpolyrneriza-`
tion reaction takes place much moreA readily than
with the monomer, with less reagent and in a
shorter time.
nots..> ,In-any'case, lsuch discoloration may be I
'removed by usual color-absorbing materials.
Although the invention has been described by
means ofV a single specific example of the opera.- '
-tion thereof, 'it will be apparent to those skilled’
in the jart that various changes in the details of
l The products of the present invention may be 20 the invention may be made Within the scope of
directly mixed with acrylate resin and themix
ture subjected to molding. Also, it is possible>
tomixthe .products of thepresent invention with
the invention. For .instancethe .apparatus need
notvlbe strictly in the lshape of a trough, but other
equivalent forms may be used. Itis even possible
the scrap acrylate resi-n which in itself is no
to dispense with a trough as such .and construct
longer. useable for furthermolding operationsbe
causeof the chemical changes-taking place ,dur
the traveling conveyorV in such a mannerthat lit
performs the vfunctions ofthe trough._rThe .resin
ing theV molding process. .Such a mixture .has
substantially the qualities of an unmolded mul
may be Vintroduced .into .the apparatus'in thecold
state, but if desired some heating thereof may-
tiple acrylate resin. ÍOr, the .productmay he
be performed in order to facilitate and shorten
mixed with’benzoylperoxide or the like and sub
the depolymerization reaction by the .direct fiame.
In "place of water, other. liquids of suitablechar.
jected topolymerization to form a molding com
position.. l-It .may be made in >any desired form,
such as rods, sheets, .or the like,’and the same
subdivided to give granulesfof the desired size.
acter or aqueous solutions Vmay be used. V>rIfhese
and other changes may be made in `the'details of
the'invention withinthe spiritY thereof, and the
4In the accompanying drawing, constituting .a 35 invention is to be broadly construed and not .to be
limited except by the .character ofthenc'laimsap- .
part hereof, and 'in which 1like reference char
acters Vindicate v.like parts, the single -iigure is a
pended hereto.
perspective view of an apparatus particularly
What .I claim is:
.
.
,
.
adapted for depolymerizing acrylate resins to
l. A method of .depolymerizing acrylate .resins
form liquid polymers «in accordance with thepres 40 which comprises wetting .said resin'with an aque~
ent invention.
Y
'
Y
There is .provided a trough l, the bottom of
which consists of -a travelling conveyor or Abelt 2,
which is held in place by a plate 5 underlying
trough .I. Belt 2 is continuous and .is rotated
around rollers 4; .'I‘he belt .moves from .the in
coming `or intake end `3 of `the trough, to the dis-`
charge end 6.
'.Amethacrylate resin in relatively small sized
pieces is 'introduced'through .funnelr'l at end 310i ~
trough ÍI, forming `a layer -8 von the moving belt.
ThroughA pipe 9 water is .introduced and Ydis
tributed rley spray `lll over material 8. .The
amount of water is-sufiicient to rthoroughly wet
the particles of resin and maybe sufficient »to
form a water layer thereover, as shown at ll.
Through a tube _I2 there is introduceda mixture
of oxygen .and acetylene, forming a series of
frames .I3 projecting downwardly and impinging
upon the >layer 1I l.. At this point depolymeriza
tion takes .place and the mixture of depolymer
ized resin .and water .in the liquid state .passes out
through 6 .and into .container l5. .The material
settles ltherein, forming an upper layer .I6 .of wa
‘ terand alowerlayer 4Il of liquid depolymerized 65
i
ous liquid, subjecting the same tothe actionof
a. direct ilame of relatively high `temperature
above 400° C. fora short time to. decompose said
resin to a liquid, and rapidly >removing said Aprod
uct from 4the zone of Vreaction to prevent volatili
zation of .said product.
„
'
»
'
i2’.` A method of depolymerizingacrylate resins
which comprises subdividing said resin to Aprovide
particles of relatively small lsize, wetting said
resin with an aqueous liquid, subjecting the same
to the action of a direct dame of relatively high
temperature above`400° C.l for alshort time to ole-y
c'ompose saidrresin toa liquid, and rapidly .re
moving said >product from` the `zone. of ‘reaction
to _prevent volatilization oisaid product.
k ` Y '
3. Ainethod of depoly'merizing acrylate .resins
which comprises piacing'saidresin on a travelling
conveyor, wetting .said resin with .an aqueous
liquid, subjecting thev same to 'the action of a4
direct iiame of relatively high temperature above
400° C. for a short time to .decompose said resin
to a liquid, and rapidly removing said productY
from the zoneof reaction toprevent volatilization
of said product.
'
`
'4. yA method of. depolymerizing acrylate .resins
which comprises placing said .resin on a traveling
product.
conveyor, wetting said resin with anaqueous
liquid, passing said mixtureunder av gas .flame
emulsion with the 'liquid monomer or liquid poly»
and during said passage subjecting the .sameto
mer. after .it is depolymerized. The liquid may 75) the .action of said direct name of relatively high.
'Incorporated in the water in pipe .9 may be .a
` detergent or wetting agent whichr willform an
subsequently lbe Yeither separated `mechanically
from .the emulsion or polymerized in the .emul
sion to 'its polymers.
f
'.'Ihe 'invention may be operated vwith acrylate
resins whichhave been vmixed with other `Sub 75
temperature above 400° C.r for a short ltime .to
decompose said .resin vto a liquid, and` rapidly .re-.
moving said product from the Zone of .reaction to
prevent volatilization »of said product.
`
`
45. A method of depolymeriz-ing .acrylate .resins
'
2,412,296
6
which comprises wetting said resin with an aque
ous liquid, subjecting the same to the action of
a direct flame of relatively high temperature
above 400° C. for a short time to decompose Said
resin to a liquid, and rapidly removing said prod
uct from the zone of reaction to prevent volatili
zation of said product, pouring said product into
tively high temperature above 400° C. for a short
time to decompose said resin to a liquid, said ñame
being at the discharge end of said conveyor, and
rapidly removing said product from the zone of
reaction to prevent volatilization of said product.
7. A method of depolyrnerizing acrylate resins
which comprises subdividing said resin to provide
particles of relatively small size, wetting said
a vessel, allowing the same to stand to form an
aqueous layer and a liquid acrylate layer, and
resin With an aqueous liquid, said liquid having
10 a wetting agent dissolved therein, subjecting the
recovering the latter.
6. A method of depolymerizing acrylate resins
same to the action of a direct ñame of relatively
which comprises wetting said resin with an aque
ous liquid, providing a trough, the bottom of
high temperature above 400° C. for a short time
to decompose said resin to a liquid, and rapidly
‘ which is a traveling conveyor, placing said resin
removing said product from the zone of reaction
on the incoming end of said conveyor, subjecting 15 to prevent volatilization of said product.
the same to the action of a direct flame of rela
CARL L. SHAPIRO.
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