close

Вход

Забыли?

вход по аккаунту

?

Патент USA US2112999

код для вставки
Patented Apr. /5’, 1938
> 2,112,999_' =
UNITED STATES" PATENT "OFFICE
CONDITIONING or cELnuLo'sE FIBER FOB
CONVERSION m'ro- CELLULOSE acn
TATE
~
George A. Richter, Berlin, N. 11.,» assignor to
Brown Company, Berlin, N. 11., a corporation
_
of Maine
No Drawing. Application May z, 1936,
'
-
Serial No. 77,612
-
r: Claims. v(c1. zso-ioi)
This invention relates to the conditioning .of
cellulose ?ber for conversion'into cellulose ace
tate and more particularly to a conditioning
tions prepared from the acetylated product for such purposes as arti?cial silk and mm manu
facture.- Moreover, I have found‘that such a
treatment that activates and otherwise improves - mixture can render cellulose ?ber of the refrac
the cellulose for the acetylating reaction. While tory character ,hereinbefore described satisfac- 5,’
not limited thereto, the conditioning treatment‘ torily. acetylatable by the usual acetylating re
agents. '_I‘he conditioning or activating treat
of the present invention is of especial useful
ness when applied to cellulose ?ber which is more, ment hereof presents the ‘important advantage
or. less refractory toward acetylatingireagents.
Wood‘ pulp which has been puri?ed to high
alpha cellulose content in alkaline liq’uors are
apt to acquire passivity toward acetylating re
agents; and the stronger the alkaline liquor,
the more passive is the pulpapt to become. In
deed, wood pulp which has been re?ned in alkav
line liquor of sufficient strength to be mercer—
/
that there is no'need for washing or otherwise
removing the activating reagents, inasmuch‘ as 10
the hydrogen peroxide leaves no undesirable res
idues in the ?ber and the‘acetic acid ‘can take
part in the'subsequent acetylation. While vari
ous percentages of hydrogen ‘peroxide may be
used in admixture with acetic acid for the acti- 15
vating treatment hereof, it is preferable to use'
izing, say, caustic soda solution'of about 18% or - aqueous hydrogen peroxide solution. -in such
greaterv strength, generally becomes so passive
amount and in such highly concentrated condi
as to require an activating treatment -.;of some ' tion together with glacial acetic acid as to dis
kind
before it can be acetylated with the desired‘ pense with the ~step of dehydrating or drying of 20
20
the activated ?ber, preparatory to acetylation.
smoothness or uniformity of reaction. Again,
sheeted cellulose ?ber, such as pulpboard and Unlike the hydrogen peroxide solution usually
waterleaf paper, ‘is' sometimes poorly responsive _ employed for medicinal or antiseptic purposes,
to acetylation even when it is ?nely shredded
25 prior to acetylation; and its poor responsiveness
may be attributable largely to its overdried con
- dition rather than‘ to the nature of its cellulose
which is of about 3% hydrogen peroxide content,
the hydrogen peroxide solution used herein is 25 '
preferably of much greater strength. Although.
it is di?icult and expensive to preparevery strong
?ber. In this connection, it might be observed _ hydrogen peroxide solutions, aqueous solutions
that it is quite desirable that cellulose ?ber to of about 30% hydrogen peroxide content are;
commercially available at a cost reasonable for 30
be acetylated contain very little moisture,.pref
erably not much' more than about 2% of its dry the purpose hereof, wherefore, I may advan
tageously'use such solutions. To be sure, such .
weight, so as to avoid undue dilution of the acet
ylating reagents. However, in drying pulpboard lsolutions=contain more than twice as‘ much water
or waterleaf'paper to the desired low residual
moisture content, as on the usual steam-heated‘
drier drums of a. papermaking machine, it is fre
quently the case that in getting-'maximum out
put on the machine, ‘the sheet is broughtto a
bone-dry condition, 1. e. overdried, particularly
40 on its surface,‘ Just as it is undesirable to have
much more than about 2% water present in the
cellulose to be acetylated, so a bone-dry condi
solutions in the activating treatment and to add 40,
so little water to the ?ber as to avoid practically
any drying or dehydratiomot the activated ?ber
may spell'a shrunken and dense ?ber structure _
prior to its acetylation.
An illustrative example of the'practice of the
resistant‘ to '.acetylation.
In accordance withthe present invention, cel-,
lulose ?ber to be acetylated is ?rst put through
lows. Pulpboard or waterleaf paper of a mois
ture content of about 1% or less and umatisi'ac
tion therein is to be avoided, as bone-dryness
an activating treatment .with a mixture of hy
'50
as hydrogen peroxide, but because only a very.
small percentage of hydrogen peroxide, based 35
on dry ?ber,‘ is su?icient when admixed' ‘with’
glacial acetic acid to cause the desired activation
or improvement of cellulose ?ber, it becomes
possible to use such aqueous hydrogen peroxide
drogen peroxide and acetic acid, the mixture
preferably containing as- it's acetic acid compo-‘
nent a fraction of the glacial acetic-acid subse
quently to enter into the acetylating‘reaction.
I have found that such a mixturenot'only ‘greatly
improves the acetylatability of/the ?ber but also
enhances the color and clarity of the usual solu
present invention may be ‘substantially as fol- 45
torily .responsive to 'acetylating reagents may
constitute the raw material. Besides being bone
dry on its surfaces, such sheeted ?ber may be so
composed of wood pulp or cotton ?ber, which,‘
on account of puri?cation in an'alkaline liquor,; _
has taken on passivity‘ toward acetylating
.
agents. For instance, the sheeted ?ber may be
composed of white, highly purified wood pulp, 66
2
9,119,999
speci?cally, mercerized wood pulp which has
glacial acetic acid to appear in the acetylating
been brought to an alpha cellulose content up
reagent together with the catalyst of such re
wards of about 96% in a caustic, soda solution agent; and this larger portion not. only ensures
of 18% or greater strength. Such'a sheet may - a uniform distribution of the peroxide through
be wetted with hydrogen peroxide-acetic, acid out the sheet, but assists in the attainment of
mixture prepared by mixing 3 to 10 parts by a ?nal sheet uniformly and well activated for
1 weight of hydrogen peroxide solution of about the acetylating reaction. Thus, the sheet may
30% strength with 97 to 90 parts by weight of be sprayed or otherwise treated continuously
glacial acetic acid; and about 20 parts of such with the activating mixture as it is coming
'10 a mixture may be substantially uniformly ap
from a papermaking, machine or from a roll
plied to the surfaces of about 100 parts by weight accumulation, whereupon it may be accumu'-~ 10
of the sheeted ?ber. The application of the lated as a roll and kept for a period; or the sheet
mixture may be effected as by spraying the wetted with the activating mixture may be ex
sheet surfaces therewith or by transferring the posed in festoon form to the air either at room
15 mixture to the sheet surfaces from the periph
or elevated temperature. The sheeted ?ber may 15
ery of a so-called "kissing" roll. The treated then be' impregnated with a large additional
a ‘sheet containing less than 2% added water, about amount of glacial acetic acid containing the
0.2 to 0.6% added hydrogen peroxide, and about catalyst/of acetylation. as by running the sheet
17% acetic acid, based on the dry weight of ?ber, continuously through a bath of such acid or by
20 may be kept for about two to eight or even-more dipping separate sheets thereinto. After keeping 20
hours at about 20° to 40° C. to effect the desired the acid-soaked sheet ?ber at a suitable tem
activation of the cellulose, after which period it perature for a substantial period of time, for,
is desirable to add to the sheet as such or after instance, at 40° C. for four or more hours, it may
it has been disintegrated more .of the glacial be acetylated, as hereinbefore described.
25 acetic. acid later to form part of the acetylating
vIt is possible to apply the conditioning or acti 25
- reagents, for instance, as much as about 400%, vating treatment hereof to bulk or shredded
based on the dry weight of the ?ber, together‘ cellulose ?ber, in which case, a substantially uni
with the desired amount of catalyst for the form wetting of the ?ber with the activating mix
acetylating reagent, for instance, about 1 to 2% ture of hydrogen peroxide and glacial acetic acid
30 sulphuric acid, based on the dry weight of the
can be had only when a comparatively large 30
?ber. After the second portion of acetic acid' amount of the mixture, say, about 100% or more,
together with catalyst has been added, it is based on the dry weight of ?ber, is sprayed or
preferable to keep the sheet at about 40° C. for otherwise applied to the- ?ber while fresh ?ber
about 30 to 60 minutes, during ,which time surfaces are being exposed to the spray, for in
35 catalyst ' is given an opportunity to diffuse
stance, while the ?ber is being stirred or tumbled
throughout the sheet and to combine substan
as the spray impinges thereon. In'_ such case, the
tially uniformly with the individual ?bers or hydrogen peroxide content or concentration in
?ber walls. The soaked sheet may then be dis ' the glacial acetic acid may be reduced so as not
integrated or shredded, if this has not already. to incorporate an excessive amount of hydrogen
40 been done, and admixed with acetic anhydrlde peroxide or water into the ?ber. A very uniform 40
and more acetic acid to produce the usual acety- I’ and e?ective' treatment of bulk ?ber with the ac
lating bath or mixture,_ the last addition of tivating mixture can be realized by suspending
glacial acetic acid giving a total glacial acetic the ?ber in many times its own weight of the
acid content of, say, about r100%, based -on the ,. activating mixture; and,’ after a substantially
45 dry weight of the ?ber. As the ?ber is stirred
uniform ?ber suspension has been prepared, as
in the acetylating reagents, it undergoes smooth much as possible of the activating mixture may
, and ‘uniform acetylation so that’ the original
be removed by a centrifuge, squeezing, or simi
~thick ?brous suspension gradually becomes a lar extracting operation. The latter treatment of '
‘ substantially clear cellulose acetate solution the bulk ?ber may be accompanied by the addi
50
from which the cellulose acetate is. precipitated
and‘ recovered as customarily.
The foregoing example lends itself ‘to wide
modi?cation’ as to the concentration of the
tion to the ?ber of so much more than the ap
proximately 2% water content desired in ?ber
intended for acetylation that provision must be
vating mixture applied to the sheeted _ ?ber
made to evaporate or otherwise remove from the
?ber water in excess of about 2%. This may, as
already indicated, be accomplished by exposing _
and/or as to the amount of the mixture infused
the centrifuged or pressed ?ber to the dehydrat
into the ?ber.
ing action of warm air currents.
aqueous hydrogen peroxide ‘solution in the acti
If such concentration and/or
amount is such as to produce in the sheet a
total water content of much greater ‘than about
60 2 to 3%, say 5% or more, basedcn the dry
weight of ?ber, the treated sheet may be exposed to warm air currents for a su?lcient period
of time to reduce the water content to about 2%
and thus to avoid undesirable dilution of the
65 acetylating reagents in which the ?ber is ?nally
acetylated. It is generally; preferable to keep
' the hydrogen peroxide concentration in the acti
vating mixture as high as possible compatible
with the'incorporation into the sheeted ?ber of
70 activating mixture in amount to impart to they
sheet a moisture content not much in excess
of 2% of the dry weight of ?ber. After keep
'
It is possible that the mixture of hydrogen
peroxide and acetic acid herein used for the
purpose of conditioning or activating cellulose 60
?ber for acetylation owes its eifectiveness to a
partial reaction between the acetic acid and the
hydrogen peroxide productive of 'peraoetic acid.
Irrespective of whether peracetic acid is or is
not present in the activating mixture, cellulose 65
?ber is greatly improved in its acetylatability
by such a mixture and, when of a refractory
nature, is transformed thereby toa satisfactory‘
acetylatable state.
I claim:—
'
.
70
1. A process which comprises treating cellulose
?ber with a mixture of hydrogen peroxide and
ing the sheet moistened with the mixture for a acetic acid and then acetylating the treated ?ber
‘while, it .is, as already indicated, desirable to in the presence of not much more than about 2%
75 add thereto ‘another much larger portion of the ‘ water, based on the dry weight of cellulose ?ber. 75
2,112,999 -
2. A process which comprises treating ceilu-_
' lose ?ber with a mixture of concentrated aqueous
adding glacial acetic,acid to the fiber, andacety-' '
lating the resulting ?ber._
_
"
,
10. As a step-product especially adapted for
, acid and then acetylating the treated ?ber in.‘ conversion into cellulose. acetate, cellulose ?ber ._
the presence of not much more than about 2% treated with a mixture composed-substantially 01!
water, based on the dry weight of cellulose ?ber. - ‘hydrogen peroxide, acetic acid, and only a small
3. A process which comprises treating cellulose percentage of- water, based on the dry weight of _
?ber with a mixture of concentrated aqueous
11. As a step-product especially adapted for
hydrogen peroxide solution and glacial acetic
10 acid, adding more glacial acetic acid to the ?ber, conversion into cellulose acetate, cellulose, ?ber
and acetylating the ?ber in the presence of not ‘treated with amixture of hydrogen peroxide-and
much more than about 2% water, based on the glacial acetic acid and containing not much more
dry weight of cellulose ?ber.
than about 2% ‘water, basedvon the dry weight .
4. A process which comprises treating cellu
of'?ben'
.
hydrogen peroxide solution and glacial acetic
?ber.
15 lose ?ber with a mixture of glacial acetic acid .
and a smaller amount of aqueous hydrogen
peroxide solution of about 30% strength and
~
g
a
'
'~ 12. As a step-productespecially adapted for 15
conversion into cellulose acetate, wood pulp of
high alpha cellulose content treated with a mix
then acetylating the treated ?ber in the presence . ture of hydrogen peroxide and acetic acid and
of not much more than about 2% water, based. containing not much more than about 2% mois
ture, based on the dry weight oi pulp.‘
,
13. As a stop-product especially adapted for
5. A process which comprises treating cellu
20 on the dry weight ‘of cellulose ?ber.
20
lose ?ber with a mixture of glacial .acetic acid - conversion ‘into cellulose acetate, white mer- ‘
and a smaller amount of aqueous hydrogen per- . cerized wood, pulp of an alpha cellulose content
oxide solution of about 30% strength, adding ' upwards of about 96% treated with a mixture
more glacial acetic acid to the ?ber, and acetylat-~
of hydrogen peroxide and acetic acidand con 25'
ingthe ?ber in the presence of not much more
taining not much more than about 2% moisture, '
based on thedry weight of pulp.
’
than'about 2% water, based on the dry weight
of cellulose ?ber.
'
6. A process which comprises treating a sub
stantially dry sheet of cellulose ?ber with a mix
ture of glacial acetic acid and concentrated
aqueous hydrogen peroxide solution in amount
to add to the sheet not much more than about
2% water, based on the dry weight of ?ber, and
acetylating the treated ?ber constituting "said
sheet.
'
'7. A process which comprises treating a‘ sub-
stantially dry sheet of cellulose ?ber with a
14. As a step-product especially’ adapted for‘
conversion into cellulose acetate, a sheet of cellu
lose ?ber treated with a- mixture of aqueous hy-'
drogen peroxide solution of about 30% strength
and a larger amount of glacial acetic acid but
containing not much more than about 2.% water,
based on the dry weight off the ?ber.
15. As a step-product-especi'ally adapted .for 35
conversion into cellulose acetate, a sheet of wood
pulp‘of high alpha cellulose content treated with 1
a mixture of aqueous hydrogen peroxide solution
mixture of glacial acetic acid and concentrated ~ of about 30% strength and a larger amount of _
40 aqueous hydrogen peroxide solution in amount to glacial acetic acid but containing ‘not much more 40.
than about 2% water, based on the dry weight
‘ add to ,the sheet not much more than about 2%
water, based on the dry weight of ?ber, adding
more glacial acetic acid to the sheet,‘and acety
lating the treated ?ber constituting said sheet.
8. A process which comprises treating cellu
45
lose ?ber with a mixture of acetic acid and aque
ous hydrogen peroxide solution of suchv water
. content and in such amount to associate with
the ?ber considerably more than 2% water, based
on the dry weight of ?ber, evaporating from the
?ber its water content in excess of about/2%.
of’ pulp.
-
16. As a step-product ‘especially adapteddor Y
conversion into cellulose acetate, a sheet of white
mercerized wood pulp of an alpha cellulose con 45
tent upwards' of about 96% and treated with a
mixture‘ of aqueous hydrogen peroxide solution
of about 30%~strength and -a larger amount or
glacial acetic acid but containing not muchY
more than about 2% ‘water,’ based on the dry
weight of pulp.
'
1
,
1'7. A process which comprises in more
_9-. A process which comprises treating cellu aqueous hydrogen peroxide solutio into sub-1
stantially dry cellulose while'keepingthe water
lose ?ber with a mixture of acetic acid and aque
ous hydrogen peroxide solution of such water‘ content of the cellulose at not muchymore than 55
‘content and in such amount to associate with the about 2%, based on the dry weight or cellu
?ber‘considerably more than 2% water, based lose’, and acetylating the cellulose in the presence _ ‘
on the dry weight of ?ber, evaporatingirom the “of such hydrogen peroxide."
?ber its water content in excess of about'3%,'
GEQRGE A. RICHTER. - _
and acetylating the resulting ?ber. '
Документ
Категория
Без категории
Просмотров
0
Размер файла
478 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа