Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
i 1069tjS6 l,, . , . l
INTRODUCTIO~
I¦ Native starch is insoluble in cold water but forms a c~lloidal
¦Isolution in hot water (above the gelatinization te~peratures) Upon
cooling from a hot solution, native gelatinized starch tends to
retrograd~ to a rigid gel or stiff paste upon aging. This paste
possesses only limited adhesive properties and remains partly insol-
uble even upon re-heating. This phenomenon is commonly known as
retrogradation or "paste-back," and is generally believed to be
caused by precipitation of amylose from the starch solution on
~- cooling. Retrogradation is most pronounced in starches o~ cereal
grains such as corn~ rice, wheat, etc., and t~ a somewhat lesser
degree in starches o root materials such as tapioca, sweet potato,
potato, etc., and to an even lesser extent in the waxy varieties of
corn and sorghum starches which contain relatively little amylose.
Obviously, the tendency to retrograde limits, and in many
instances negates, the usefulness of native starch solutions. ~or
example, native starch is of little use a9 an adhesive because ~f
the marked decrease in adhesive properties and the lack of tack
after retrogradation.
The pro~lem of gelling is further aggravated when the. starch
is subjected to partial depolymerization, as is commonly done for
~ modifying the solids viscosity relationship so that the viscosity
I of the cooked paste is reduced below that of the native starch.
Such depolymerization is customarily done by treatment with acid,
by treatment with alpha-amylase or 5tarch-thinning enzymes, or by
treatment with an oxidizing agent. Unfortunately, for the most
cereal and r t ztarches, zuch depolymerization treatm-nts ncreaoe
.~ .
~'
' ' 106965~i
the tendency of the cooked starch to undergo viscosity increase on aging
and gelling. This increased tendency may be a serious limitation in
the selection and use of the depolymerized starch. Where the tPndency
toward viscosity increase on aging or cooling is too great, or if the
starch paste tends to gel on aging or cooling, the usual remedy is to
select the still thinner or more highly modified starch which shows this
thickening or gelling tendency to a lesser degree. However, these thinner
starches are more highly depolymerized and, consequently, are less effective
as regards the strength and surface improvements imparted to the paper or
textile on which they are used.
In general, all cereal starches, both modified and unmodified,
can be classed as "gellable". Furthermore, for any particular starch,
modified starch or starch derivative, the retrogradation or gelling
properties are well known to those skilled in the art, and, therefore,
there should be no difficulty in selecting those starches which can be used
most advantageously in the starch size compositions of this invention.
THE INVENTION
In accordance with the invention, an improved starch paste which
is reduced in its tendency to gell and which has lower viscosity at a
given solids level is afforded, which paste contains from between 5 to 40%
by weight of starch and from 0.01 to 5% by weight, based on the weight of
the starch of a modified fatty alcohol which has been reacted with from 2 to
10 moles of ethylene oxide, the remainder of the paste being water, and the
modified fatty alcohol having been added to the starch prior to
gelatinization thereof.
.' .
, .'
. .
,
.
: , ' , ' : ~.
1069~;56
The Fatty Al.cohol
ili The fatty alcohol additive is prepared by ethoxylating a
¦ifatty alcohol with from between 1 - 20 moles of ethylene oxide.
Preferably the amount of ethylene oxide u~ed to treat the fatty
jalcohol is 2 - 10 moles. I,
¦ The atty alcohols contain from between 10 - 22 carbon atoms
¦in chain length. They are preferably mixed fatty alcohols which
¦contain between 12 - 16 carbon atoms. Such mixed fatty groups may
¦be obtained from either animal fats or vegetable oils. These fatty
groups may be straight or branch chained and may contain certain
side chain constituents such as hydroxyl groups. Typical commercial
materials that wor~ exceedingly well in the practice of the inventior
is a Cl 2 - Cl 5 alcohol reacted with 9 moles of ethylene oxide.
Another material is a Cl 2 - Cl 4 mixed fatty alcohol which has been
ethoxylated with about 3 moles of ethlene oxide.
~ he invention is applicable to preparing starch paste from
any gellable starch or modified starch. The invention works partic-
ularly well in treating starch paste made from pearl starch modified
during its cooking with ammonium persulfate. This type of starch is
discussed in detail in the disclosure of U.S. 3,211,564. The eth-
oxylated fatty alcohols described above are capa~le of sta.bilizlng
starch pas~s which have a starch content ranging between 5 ~ ~0% hy
weight. The amount of ethoxylated fatty alcohol used to stabilize
the starch paste may vary between 0.1% to 5% based on the weight of
the starch with dosages ranging between 0.1 to 1% by weight givirlg
excellent results in most cases.
; _4_
(
'. ~0696S6
xamples
To illustrate the invention, the following are given by way
of example.
~, In many paper mills that utillze starch paste as a sizing
¦Imaterial, it is customary to prepare such paste by means of a jet
¦¦cooker. These cookers which operate at temperatures up to 350F.
and, in some instances, under press~re, are capable of preparing
~starch paste or sizes in a matter of a few seconds of reaction time.
All of the examples were prepared using a laboratory jet cooker in
a ~emperature range of 240F. to 285F. The particular starch used
was a pearl starch that was modified using ammonium persulfate as
per U.S. 3,211,564.
In all instances the various additive5 te~ted Were admixe~
with the starch prior to its being gelatinized and be~ore its admix-
tui-e with the water.
In addition to testing ethoxylated fatty alcohols of the
type used in the practice of the invention, certain of the tests
presented hereinafter utilized commercial starch paste stabilizers.
The various materials tested are listed below:
Composition No. 1:
Cl 2 - Cl 5 alcohol reacted with 9 m~les of
ethylene oxide;
1 Compo~ition No. 2:
¦ Cl 2 - Cl 4 alcohol reacted with 3 moles of
ethylene oxide;
Composition No. 3:
The mono glyceride of stearic acid;
~,
. ,
! ' C
~l 106~3tiS~
,` . . I
Composi.ti~n ~o. 4:
Calcium stearate.
il In all of the above tests the starch pastes were prepared at
j~the concentrations indicated and allowed to cool to room tempera-
ture. They were then reheated to 50C. and measured at different
¦~Brookfield viscosities using different RPM's. After taXing these
measurements, the paste was allowed to cool t~ 25UC. and the viscos-
ities were again remeasured, again using a Brookfield Viscosimeter, .
¦¦me results these tests are presented below in ~rables I and II: ¦
. ,. .~
.
' .
u) ~ l
~ ~0696S6
O ~.'æ ~. S . N
co' ~~ V~ n
, O
U~ U7 Ul
!T~
r~
O ~ O ~ 0~ 0
.
o a o o o~
. u~ l N ~
' U U)~1 ~57 . ~ O
o ~ N
, 11~
.. 1 ~ ~
~ 11~~0 U) O t~
~1
O OOOOO O
O ~ ~ ' O
'1 tO 1~') 0 a~ d' ' 10
H . ~ N ~ d' N
~ 8 :~
~ H ~1 O d'r-1 N ~O
O
' I O ~P O O IJ~
X . In
~ C)
. I ~
O OO' O O O
N N d ~
~` ~ o o o o o ~ o
~ ~ x æ ~ ~ ~
.~ ou~ u~ o u~ Q
n r~ N (~ ~') a O
,,, .
I ~ ~ ~ ~ ~n ,
E~
)
.
~06~656
O ~ ~1 ~ ~ ~ ,~ ~ ~ O `D ~ O ~ CO ~ O
O ~~ o ~ co GO ~ aJ ~1
~ ~ . .
. o oo . . ,~
~1 O
o ~ ~ o~
O ~ ~ ~ ~ ~ ~ ~1 ~ ~ ~ C~l
.
~ ~ o ~ ~l o ~
~ ~o ~ ~
H
~1 . ' ' ~)
~1 1-~ ~
,: ' . . `
'. ' : ~ I , "
. ', ''
"' ' , '~
. I . ,' " .
., . ` , ~ ~ .
o ~7 ~
, U~ .. . , ' ,
,~ '
~ ~ 1 0 0 0 0 0 0 ~J
J~ h ~ . S~
` : , :
,~J . O
tQ O . . . . . . . ., . . . .. . . . . c,~
" ` ` ` ') , .) ,
1,
l 10696S6 (
Based on the above, it is evident that a stabilized starch
composition with l~wered viscosities is afforded.
The invention is subject to various modifications without
departing from the spirit thereof. In certain instances it is
~ossible to add the ethoxylated fatty alcohol to the starch after
cooking or gelatinization although pre-addition is preferred.
Unmodified as well as modified starches can ~e used.
Having thus described my invention, it is claimed;
