U.S. patent application number 09/852330 was filed with the patent office on 2001-09-27 for cold water soluble starch aldehydes and the method of preparation thereof.
Invention is credited to Cimecioglu, A. Levent, Eden, James L., Ohlhorst, Bjork, Slete, Douglas J., Solarek, Daniel B..
Application Number | 20010025102 09/852330 |
Document ID | / |
Family ID | 22685215 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010025102 |
Kind Code |
A1 |
Cimecioglu, A. Levent ; et
al. |
September 27, 2001 |
Cold water soluble starch aldehydes and the method of preparation
thereof
Abstract
Stable, cold water soluble, ready for use starch aldehyde
compositions and the method of preparation of such compositions
wherein an aqueous dispersion of a fluidity or converted starch
acetal is hydrolyzed under acidic conditions to form the starch
aldehyde which is then spray dried into a cold water soluble starch
aldehyde powder.
Inventors: |
Cimecioglu, A. Levent;
(Princeton, NJ) ; Ohlhorst, Bjork; (Luzem, CH)
; Solarek, Daniel B.; (Belle Mead, NJ) ; Slete,
Douglas J.; (Augusta, NJ) ; Eden, James L.;
(East Millstone, NJ) |
Correspondence
Address: |
Laurelee A. Duncan
Intellectual Property
NATIONAL STARCH AND CHEMICAL COMPANY
P.O. Box 6500
Bridgewater
NJ
08807-0500
US
|
Family ID: |
22685215 |
Appl. No.: |
09/852330 |
Filed: |
May 9, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09852330 |
May 9, 2001 |
|
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09186503 |
Nov 5, 1998 |
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Current U.S.
Class: |
536/50 ;
536/111 |
Current CPC
Class: |
C08B 31/08 20130101;
D21H 17/29 20130101; C08B 31/125 20130101; D21H 21/20 20130101;
C08B 31/12 20130101; D21H 21/18 20130101 |
Class at
Publication: |
536/50 ;
536/111 |
International
Class: |
C08B 031/08 |
Claims
What is claimed is:
1. A method of preparing a cold water soluble starch aldehyde
composition comprising: a) forming a converted starch acetal having
a water fluidity of from about 30 to 85, an acetal content
represented by a DS of from about 0.005 to 0.25 and a structure
selected from the group consisting of: 5wherein ST is starch; R is
(CH.sub.2).sub.n or a divalent aromatic group where n is 0 to 22;
R.sub.1, R.sub.6 and R.sub.7 are independently selected from the
group consisting of hydrogen and a C.sub.1 to C.sub.22 alkyl, aryl,
aralkyl or alkaryl group; R.sub.2, R.sub.5 and R.sub.8 are
independently (CH.sub.2).sub.m where m from 1 to 6, R.sub.3 and
R.sub.4 are independently hydrogen or an alkyl group having 1 to 6
carbon atoms; R.sub.9 is a divalent organic group containing no
starch-reactive substituents, Y is an anion and A and A' are
independently an alkyl group of 1 to 6 carbon atoms or together
form at least a 5-membered cyclic acetal; b) cooking the acetal
containing starch under acidic conditions to hydrolyze and form a
dispersion of the corresponding starch aldehyde; and c) spray
drying the resulting aldehyde at a pH of from about 4 to 7 to form
a cold water soluble starch aldehyde powder.
2. The method of claim 1 wherein the starch is modified with a
cationic group.
3. The method of claim 2 wherein the spray drying step is a
steam-injection dual or single atomization operation.
4. The method of claim 2 wherein the cooking and spray drying steps
are combined into a continuous jet cooking/spray drying
operation.
5. The method of claim 2 wherein the cationic group is a tertiary
amine or quaternary ammonium ether group.
6. The method of claim 1 wherein the starch acetal has a water
fluidity of from about 50 to 65 and an acetal content represented
by a DS of from about 0.01 to 0.06.
7. The method of claim 6 wherein the starch is modified with a
cationic group.
8. The method of claim 7 wherein the spray drying is a
steam-injection dual or single atomization operation.
9. The method of claim 7 wherein the cooking and spray drying steps
are combined into a continuous jet cooking/spray drying
operation.
10. The method of claim 6 wherein the cationic group has a DS of
from about 0.005 to 0.25.
11. A cold water starch aldehyde composition comprising a converted
starch aidehyde having a water fluidity of from about 30 to 85, an
aldehyde content represented by a DS of from about 0.005 to 0.25
content and a structure selected from the group consisting of:
6wherein ST is starch or modified starch; R is (CH.sub.2).sub.n or
a divalent aromatic group wherein n is 0 to 22; R.sub.1, R.sub.6
and R.sub.7 are independently selected from the group consisting of
hydrogen and a C.sub.1 to C.sub.22 alkyl, aryl, aralkyl or alkaryl
group; R.sub.2, R.sub.5 and R.sub.8 are independently
(CH.sub.2).sub.m where m is from 1 to 6; R.sub.3 and R.sub.4 are
independently hydrogen or an alkyl group having 1 to 6 carbon
atoms; R.sub.9 is a divalent organic group containing no
starch-reactive substituents and Y is an anion.
12. The starch aldehyde of claim 11 wherein the starch is selected
from the group consisting of corn, potato, sweet potato, wheat,
rice, tapioca, waxy maize, sago, sorghum and high amylose
starch.
13. The starch aldehyde of claim 12 having a water fluidity of from
about 50 to 65 and an aldehyde DS content of from about 0.01 to
0.06.
14. The starch aldehyde of claim 13 wherein the starch is modified
with a cationic group which is a tertiary amine or quaternary
ammonium ether group.
15. In a method of making paper having wet strength, dry strength
and temporary wet strength the step which comprises adding as a
strength aid to the stock at any stage prior to forming a web, an
effective amount of the cold water soluble starch aldehyde powder
of claim 11.
16. The method of claim 15 wherein the starch aldehyde is modified
with a cationic group which is a tertiary amine or a quaternary
ammonium ether group.
17. The method of claim 15 wherein the starch aldehyde has a water
fluidity of from about 50 to 65 and an aldehyde DS content of from
about 0.01 to 0.06.
18. The method of claim 17 wherein the starch aldehyde is modified
with a cationic group which is a tertiary amine or quaternary
ammonium ether group.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to stable, cold water soluble, ready
for use starch aldehyde compositions, their method of preparation
and the use thereof as strength additives in papermaking.
[0002] The term "paper", as used herein, includes sheet-like masses
and molded products made from fibrous cellulosic material which may
be derived from natural sources, synthetics such as polyamides,
polyesters, rayon and polyacrylic resins as well as from mineral
fibers such as asbestos and glass. In addition, paper made from
combinations of cellulosic and synthetic materials are applicable
herein. Paperboard is also included within the broad term
"paper".
[0003] The preparation of aldehyde containing starches and other
polymers and the use of such aldehyde derivatives as wet and dry
strength additives in the paper industry is well known. Oxidative
and non-oxidative methods have been used to introduce aldehyde
groups into polysaccharides such as starch. The oxidative methods
have included: a) treatment of starch with alkali metal bromite or
hydrobromite under carefully controlled conditions as disclosed in
U.S. Pat. No. 3,553,193 issued Jan. 5, 1971 to D. H. LeRoy et al.;
b) oxidizing a carbohydrate with an alkali metal ferrate as shown
in U.S. Pat. No. 3,632,802 issued Jan. 4, 1972 to J. N. BeMiller,
c) enzymatically oxidizing hydroxypropyl galactoglycoside starch
ethers or ethyl galactoglycoside starch ethers with galactose
oxidase as disclosed in U.S. Pat. No. 4,663,448 issued May 5, 1987
to C. W. Chiu; and, d) treatment with periodic acid or periodates
as disclosed in U.S. Pat. No. 3,096,969 issued to J. E. Slager on
Apr. 23, 1963 which shows the preparation of dialdehyde
polysaccharide using periodic acid and U.S. Pat. No. 3,062,652
issued on Nov. 6, 1962 to R. A. Jeffreys et al. which shows the
preparation of dialdehyde gums using periodate or periodic
acid.
[0004] Non-oxidative methods for preparing aldehyde containing
starches include a) the reaction of granular starch with an
unsaturated aldehyde as disclosed in U.S. Pat. No. 3,519,618 issued
Jul. 7, 1970 to S. Parmerter, and b) the reaction of an amidated
starch or glucopyranosyl compound with glyoxal as shown in U.S.
Pat. No. 3,740,391 issued Jun. 19, 1973 to L. Williams et al.
[0005] Aldehyde containing polymers used as strength additives in
paper are disclosed in U.S. Pat. Nos. 4,508,594 and 4,605,718
issued on Apr. 2, 1986 and Aug. 12, 1986 respectively to R. Jansma
et al. which show aldehyde containing vinyl polymers. Glyoxalated
(meth)acrlyamide polymers are disclosed in U.S. Pat. No. 5,320,711
issued to D. Dauplaise et al. on Jun. 14, 1994.
[0006] U.S. Pat. No. 3,269,964 issued to J. Curtis on Aug. 30, 1966
discloses a water dispersible composition which is the reaction
product of a dialdehyde polysaccharide and a condensation product
of dicyandiamide and formaldehyde. U.S. Pat. No. 3,299,052 issued
to J. Curtis on Jan. 17, 1967 also discloses a water dispersible
composition which is the reaction product between a dialdehyde
polysaccharide and a hypochlorite oxidized polysaccharide.
[0007] Many of the wet strength additives currently used in the
paper industry are synthetic polymers which are aqueous,
ready-for-use liquids. However, they generally have limited storage
stability and shelf life.
[0008] One of the problems associated with the use of aldehyde
containing derivatives is the possibility of crosslinking and
instability that they possess.
[0009] U.S. Pat. No. 4,675,394 issued to D. Solarek et al. on Jun.
23, 1987, discloses aldehyde containing starch derivatives, their
preparation from acetals and their use as paper additives. As
disclosed in the patent, problems associated with the use of
aldehyde derivatives in active form can be avoided by providing the
stable acetal form of the corresponding starch which can be
converted to the starch aldehyde by cooking under acid conditions
just prior to its use. However, this involves an extra conversion
step which must be carried out by the user-customer.
[0010] What is desired is a ready for use starch aldehyde product
which is stable and avoids the need to combine it with other
components or the necessity of performing an extra processing step
prior to its use in papermaking or other application.
SUMMARY OF THE INVENTION
[0011] Now it has been found that a cold water soluble, ready for
use starch aldehyde composition is provided by the process wherein
an aqueous dispersion of a fluidity or converted starch aldehyde is
formed and then spray dried into a cold water soluble powder.
[0012] More particularly, this invention involves a process for the
preparation of a cold water soluble, ready for use starch aldehyde
composition comprising:
[0013] a) forming a converted cationic starch acetal having a water
fluidity of from about 30 to 85 and the structure selected from the
group consisting of 1
[0014] wherein ST is cationic starch; R is (CH.sub.2).sub.n or a
divalent aromatic group wherein n is 0 to 22; R.sub.1, R.sub.6 and
R.sub.7 are independently selected from the group consisting of
hydrogen and a C.sub.1 to C.sub.22 alkyl, aryl, aralkyl or alkaryl
group; R.sub.2, R.sub.5 and R.sub.8 are independently
(CH.sub.2).sub.m where m is from 1 to 6; R.sub.3 and R.sub.4 are
independently hydrogen or an alkyl group having 1 to 6 carbon
atoms; R.sub.9 is a divalent organic group containing no
starch-reactive substituents, Y is an anion such as a halide,
sulfate or nitrate; and A and A' independently are an alkyl group
of 1 to 6 carbon atoms or together form at least a 5-membered
cyclic acetal;
[0015] b) cooking the acetal containing starch under acidic
conditions to hydrolyze and form a dispersion of the starch
aldehyde; and
[0016] c) spray drying the resulting aldehyde at a pH of from about
4 to 7 to form a cold water soluble starch aldehyde powder.
DETAILED DESCRIPTION OF THE INVENTION
[0017] This invention involves stable, cold water soluble starch
aldehyde compositions and the method of preparation of such
compositions. The starch aldehyde is prepared by first providing a
converted starch acetal which is hydrolyzed under acid conditions
to form the starch aldehyde which is then spray dried into a cold
water soluble starch aldehyde powder.
[0018] The starch aldehyde has a structure selected from the group
consisting of: 2
[0019] wherein ST is starch or modified starch; R is
(CH.sub.2).sub.n or a divalent aromatic group wherein n is 0 to 22;
R.sub.1, R.sub.6 and R.sub.7 are independently selected from the
group consisting of hydrogen and a C.sub.1 to C.sub.22 alkyl, aryl,
aralkyl or alkaryl group; R.sub.2, R.sub.5 and R.sub.8 are
independently (CH.sub.2).sub.m where m is from 1 to 6; R.sub.3 and
R.sub.4 are independently hydrogen or an alkyl group having 1 to 6
carbon atoms; R.sub.9 is a divalent organic group containing no
starch-reactive substituents and Y is an anion such as a halide,
sulfate or nitrate.
[0020] Preferably in the above aldehyde structures, n is 0 to 11
and more preferably 0 to 5; R.sub.1, R.sub.6 and R.sub.7 are
methyl; and m is 1 to 2. The starch may be modified with cationic,
anionic, amphoteric, zwitterionic, hydrophobic and nonionic groups
and combinations of such groups. It is preferred that the starch is
modified with a cationic group. Cationization of the starch can be
produced by well known chemical reactions with reagents such as
amino, imino, ammonium, sulfonium or phosphonium groups as
disclosed, for example, in "Cationic Starches" by D. B. Solarek, in
Modified Starches: Properties and Uses, Chapter 8, 1986 and in U.S.
Pat. No. 4,119,487 issued Oct. 10, 1978 to M. Tessler. Such
cationic derivatives include those containing nitrogen containing
groups comprising primary, secondary, tertiary and quaternary
amines and sulfonium and phosphonium groups attached through either
ether or ester linkages. Particularly useful cationic derivatives
are those containing amino or nitrogen groups having alkyl, aryl,
alkaryl, aralkyl or cyclic substituents of up to 18 carbon atoms
and especially 1 to 6 carbon atoms. Preferred derivatives are those
containing the tertiary amino and quaternary ammonium ether
groups.
[0021] The general method for preparing starches containing
tertiary amino groups is described in U.S. Pat. No. 2,813,093
issued Nov. 12, 1957 to C. Caldwell et al. and also in U.S. Pat.
No. 4,675,394 issued Jan. 23, 1987 to D. Solarek et al. The
addition of quaternary ammonium groups to the starch is described
in the previously noted '093 and '487 patents. The preparation of
cationic sulfonium derivatives is described in U.S. Pat. No. 2,989,
520 issued June, 1991 to M. Rutenberg et al. and the preparation of
cationic phosphonium dervivatives is disclosed in U.S. Pat. No.
3,077,469 issued Feb. 12, 1963 to A. Aszalos. The above noted
patents, i.e., '487, '093, '394, '520 and '469 are all incorporated
herein by reference.
[0022] The introduction of the cationic and other derivatizing
groups may be prior to or subsequent to the reaction with the
acetal derivatizing reagent as described herein or the introduction
may be simultaneous with the acetal reagent and other derivatizing
reagents. The amount of cationic group can be varied and generally
a DS (degree of substitution) of from about 0.005 to 0.25 and
preferably from about 0.01 to 0.06 will be used. The term "degree
of substitution" as used herein indicates the average number of
sites per anhydroglucose unit of the starch molecule on which there
are substituent groups.
[0023] The base starch material used herein may be derived from any
plant source including corn, potato, sweet potato, wheat, rice,
tapioca, waxy maize, sago, sorghum and high amylose starch such as
high amylose corn, i.e., starch having at least 45% by weight of
amylose content. Starch flours may also be used as starch
source.
[0024] The starch used in preparing the cold water soluble powders
must be a fluidity or converted starch having a water fluidity (WF)
of from about 30 to 85 and preferably about 50 to 65. The
measurement for water fluidity as described herein is made using a
Thomas Rotational Shear Type Viscometer (manufactured by Arthur H.
Thomas Co., Philadelphia, Pa.) in accordance with standard
procedures as disclosed in Zwiercan et al., U.S. Pat. No. 4,499,116
issued Feb. 12, 1985 which patent is incorporated by reference
herein. The conversion of starch for use in this invention may be
accomplished by known techniques such as acid hydrolysis, oxidation
or enzyme conversion. Acid hydrolysis typically involves treatment
of heated granular starch with mineral acid such as hydrochloric or
sulfuric acid. Oxidation involves treatment of starch with an
oxidizing agent such as sodium hypochlorite or using hydrogen
peroxide and a catalytic amount of manganese salt as disclosed in
U.S. Pat. No. 4,838,944 issued Jun. 13, 1998 to L. Kruger. Enzyme
conversion involves treatment of granular starch slurried in water
using an enzyme, e.g., alpha amylase enzyme at pH of about 5.6 to
5.7. A further description of known starch conversion processes may
be found in "Converted Starches" by O. B. Wurzburg, Modified
Starches, Chapter 2, pp. 17-40, 1986.
[0025] The starch aldehydes of this invention are prepared
non-oxidatively by initially forming the converted starch acetals
and then hydrolyzing them under acidic conditions. The starch
acetals are prepared by reacting a modified or unmodified starch at
a pH of about 9 or above with an acetal reagent which does not
substantially crosslink or oxidize the starch during reaction. It
is important that the starch acetal contain a limited defined
amount of acetal content and this generally is a DS of from about
0.005 to 0.25 and preferably from about 0.01 to 0.06. The method of
preparing the acetals is further described in U.S. Pat. No.
4,675,394 issued Jun. 23, 1987 to D. Solarek et al., which patent
is incorporated herein by reference. It is understood that any
means of adjusting the pH of the aqueous solution may be employed
to attain the desired pH.
[0026] The acetal reagent has the general structure: 3
[0027] wherein Z is an organic group capable of reacting with the
starch molecule to form an ether derivative and is selected from
the group consisting of an epoxide, a halohydrin, an ethylenically
unsaturated group and a halogen; and R.sub.10 is a divalent organic
group containing no reactive substituents. Typical acetal reagents
have the formula: 4
[0028] where R, R.sub.1 to R.sub.8 and A and A' are defined as
above and X is selected from the group consisting of chlorine,
bromine and iodine. In the halohydrin reagent the halogen and
hydroxyl groups may be interchanged.
[0029] The starch aldehydes are prepared from the starch acetals by
simultaneously cooking and hydrolyzing under acidic conditions at a
pH of from about 1 to 6 and preferably about 2 to 3. This may be
done using batch or jet cooking procedures. It is understood that
any means of adjusting pH of the aqueous solution may be employed.
The solids content will depend on the starch fluidity (WF) and
acetal content (DS) and generally will vary from about 1 to 30% and
more particularly from about 5 to 20% by weight. It is understood
that upon hydrolysis, the aldehyde content generated is equal in
degree of substitution (DS) to the initial acetal DS on starch. The
aldehyde content or DS will therefore be from about 0.005 to 0.25
and preferably from about 0.01 to 0.06. U.S. Pat. No. 4,675,394
discloses the method of making starch aldehydes from starch acetals
and also describes the acetal reagents and such patent is hereby
incorporated by reference for such descriptions and methods.
[0030] The starch aldehyde cook or dispersion derived from the
starch acetals, as described herein, are subsequently spray-dried
after adjusting the pH to from about 4 to 7 to convert the starch
aldehyde cook into a stable, ready for use, cold water soluble
powder. Various methods of spray-drying are known and may be used
in this invention. Some spray-drying methods are disclosed and
described in U.S. Pat. No. 5,318,635 issued to J. Kasica et al. in
Jun. 7, 1994.
[0031] One particularly useful spray-drying method is the
continuous coupled jet-cooking/spray-drying process of the type
disclosed in U.S. Pat. No. 5,131,953 issued Jul. 21, 1992 to J.
Kasica et al. and hereby incorporated by reference. This process
comprises the steps of:
[0032] a) forming a slurry or a paste comprising the converted
starch and water;
[0033] b) jet-cooking the aqueous slurry or paste of the starch
with steam at a temperature sufficient to fully disperse or
solubilize the starch;
[0034] c) conveying and introducing under high temperature and
pressure the jet-cooked dispersion or solution into a nozzle of the
spray-dryer;
[0035] d) atomizing the jet-cooked dispersion or solution through
the nozzle of the spray-dryer;
[0036] e) drying the atomized mist of the jet-cooked starch within
the spray- dryer chamber; and
[0037] f) recovering the jet-cooked and spray-dried starch as a
water dispersible or water soluble powder.
[0038] Other useful spray-drying techniques are the
steam-injection/dual and single atomization processes as described
in U.S. Pat. No. 4,280,851 issued Jul. 28, 1981 to E. Pitchon et
al.; U.S. Pat. No. 4,600,472 issued Jul. 15, 1986 to E. Pitchon et
al. and U.S. Pat. No. 5,149,799 issued Sep. 22, 1992 to R. Rubens;
the disclosures of which are all incorporated herein by
reference.
[0039] The temperature and pressure conditions used in the
spray-drying operation can vary depending on the particular starch
material being used and typically the temperature will vary from
about 80 to 220.degree. C. and the pressure from about 20 to 150
psig.
[0040] Ready for use free aldehyde liquids can be generated from
the spray-dried powders by dispersing the powders in water at a pH
of about 2 to 9, preferably 5 to 8 and allowing them to dissolve.
Concentrations up to 20% or higher can be prepared depending on the
fluidity and the acetal content of the base starch.
[0041] The starch aldehyde powders of this invention are useful as
ready for use wet and dry strength additives in papermaking. The
starch aldehyde derivatives may be used as beater additives,
although their addition to the pulp may occur at any point in the
papermaking process prior to the ultimate conversion of the wet
pulp into a dry web or sheet. Thus, for example, they may be added
to the pulp while the latter is in the hydropulper, beater, various
stock chests or headbox. The derivative may also be sprayed onto
the wet web.
[0042] The aldehyde derivatives may effectively be used for
addition to pulp prepared from any type of cellulosic fibers,
synthetic fibers or combinations thereof. Among the cellulosic
materials which may by used are bleached and unbleached soda,
neutral sulfite, semi-chemical chemiground wood, ground wood or any
combinations of these fibers. Fibers of the viscous rayon or
regenerated cellulose type may also be used, if desired.
[0043] Any desired inert mineral fillers may be added to the pulp
which is to be modified with the starch aldehydes herein. Such
materials include clay, titanium dioxide, talc, calcium carbonate,
calcium sulfate and diatomaceous earths. Rosin or synthetic
internal size may also be present, if desired.
[0044] The proportion of the starch aldehyde derivative to be
incorporated into the paper pulp may vary in accordance with the
particular pulp involved and the properties desired. In general, it
is desired to use about 0.05 to 15% and preferably about 0.1 to 5%
of the derivative by weight based on the dry weight of the pulp.
Within the preferred range, the precise amount which is used will
depend upon the type of pulp being used, the specific operating
conditions, the particular end use for which the paper is intended
and the particular property to be imparted. The use of amounts
greater than 5% is not precluded, but is ordinarily unnecessary in
order to achieve the desired result.
[0045] The following examples will more fully illustrate the
embodiments of this invention. In the examples, all parts and
percentages are by weight and all temperatures in degrees Celsius
unless otherwise noted.
EXAMPLE 1
[0046] Preparation of converted cationic starch acetals by a
consecutive reaction:
[0047] A native waxy maize starch was first converted using
manganese catalyzed hydrogen peroxide oxidation. The starch (5000
g) was slurried in 7500 ml of water and 1333 g of aqueous sodium
hydroxide (3%) were introduced slowly to adjust the pH of the
mixture to 11.0 to 11.7. Potassium permanganate solution (12.5
g;2%) was added and allowed to mix for 15 minutes and this was
followed by addition of 46.7 g hydrogen peroxide (30% solution).
The mixture was stirred at room temperature for 16 h and a sample
was taken which was measured to be 65 WF.
[0048] Sodium sulfate (2000 g) was added to this slurry of
converted starch followed by 357.2 g of
3-chloro-2-hydroxypropyltrimethylammonium chloride (as 65%
solution) together with 333.5 g of sodium hydroxide (as 21%
solution) simultaneously via mixing through an in-line mixer. The
reaction was then allowed to proceed at 40 to 45.degree. C. for 16
h. A small aliquot of the reaction mixture was removed at this
stage and analyzed to contain 0.33% cationic nitrogen
(DS=0.038).
[0049] The pH of the reaction was adjusted to 11.0 to 11.5, if
necessary, by adding 4.5% sodium hydroxide solution containing 10%
sodium sulfate. An Acetal Reagent, 427.9 g (as 95.6% active) of
2-chloro-N-(2,2-dimethoxy- ethyl)-N-methylacetamide was then added
all at once, and the slurry was stirred at 40 to 45.degree. C. for
a further 16 h. The pH of the mixture was maintained during this
period between 11.0 to 11.5 using periodic additions of the
above-mentioned sodium hydroxide/sodium sulfate solution. The pH of
the mixture was then reduced to 8 to 9 using 10% HCI. The product
was filtered off, washed extensively with water whose pH was
adjusted to 8 to 9, and dried. It was analyzed to contain total
nitrogen of 0.75%. Therefore, the nitrogen content due to starch
bound acetal reagent was calculated to be 0.42% (DS=0.049).
EXAMPLE 2
[0050] Preparation of cold water soluble cationic starch aldehydes
by a two-step batch process:
[0051] The fluidity cationic starch acetal prepared in Example 1
above was converted into the free aldehyde form by cooking its 15%
solids slurry at pH 2.5 and 90 to 100.degree. C. for 30 minutes
followed by rapid cooling. The pH was adjusted with aqueous
sulfuric acid. Concentration of the starch dispersion was adjusted
to 8 to 10% range by adding appropriate amount of water during the
cooling process. The pH of the cooled cationic starch aldehyde
dispersion was then slowly raised using aqueous NaOH to 4 to 5 for
storage.
[0052] The cationic starch aldehyde dispersion prepared above was
spray dried using a conventional drier equipped with wheel type
atomizer. Inlet and outlet temperatures of the drier were 150 to
220.degree. C. and 80 to 125.degree. C. respectively, and
dispersion feed temperature was 75 to 80.degree. C. The resulting
product was a cold water soluble cationic starch aldehyde powder,
which was stable and easily redispersible for use in papermaking
and other applications.
EXAMPLE 3
[0053] Preparation of cold water soluble cationic starch aldehydes
by a continuous jet-cooking spray-drying process:
[0054] The converted cationic starch acetals prepared in Example 1
were also converted into cold water soluble cationic starch
aldehydes using a process in which a continuous starch jet-cooker
was coupled to a spray-drier. In this one-step operation, starch
acetals were cooked and hydrolyzed to starch aldehydes
simultaneously in the jet-cooking portion of the apparatus followed
by being sent immediately to a spray-drier without having been
cooled and thus converted to cold water soluble powders in a single
continuous manner. A 12% solids slurry of the cationic starch
acetal prepared in Example 1, with its pH adjusted to 2.0 with
sulfuric acid, was cooked through a steam heated jet-cooker at a
rate of 0.25 gpm and at 300 to 310.degree. F. temperature and 60 to
70 psi internal pressure. The resulting cationic starch aldehyde
dispersion whose pH was raised to 4 to 5 by in-line addition of
aqueous sodium hydroxide, was then sent to a spray-drier equipped
with a two-fluid type atomization nozzle without cooling and
depressurization. The spray-drying portion of the process was
carried out at 460 to 465.degree. F. and 230 to 240.degree. F.
inlet and outlet temperatures respectively and a steam atomization
pressure of 120 psi, and yielded an easily redispersible, stable
and cold water soluble form of the cationic starch aldehyde.
EXAMPLE 4
[0055] The cold water soluble cationic starch aldehyde powders
prepared in Examples 2 and 3, following dissolution in water were,
tested and evaluated for wet tensile strength in 18 lb/3300 sq. ft
handsheets made from 100% Northern Softwood Kraft pulp (650 CSF) on
a Noble and Wood Sheet Mold. The addition level of the starch was
10 lb/ton. One inch (1") wide strips were cut from the handsheets
and tested for wet tensile strength at the breaking point and had
an average strength of 293 g/inch and 272 g/inch for powders
obtained in Examples 2 and 3 respectively. In comparison, an
untreated strip yielded an average of 20 g/inch. Likewise treated
strips also showed an enhanced dry strength over untreated strips,
giving dry breaking tensile strengths in ranges of 2000 to 2100
g/inch and 1400 to 1500 g/inch respectively. Table 1 summarizes
properties and testing results of additional cold water soluble
cationic starch aldehydes prepared.
1TABLE 1 Cold water soluble cationic starch aldehyde powders.
Cationic Acetal Wet Fluidity Substitution Substitution strength
Sample (WF) (DS) (DS) (g/inch) 1 38 0.041 0.056 228 2 44 0.038
0.061 278 3 52 0.038 0.056 271 4 55 0.038 0.054 292 5 57 0.037
0.052 281 6 58 0.037 0.054 278 7 64 0.034 0.053 292 8 68 0.038
0.054 282 9 73 0.037 0.052 211
EXAMPLE 5
[0056] To show the stability properties of the cold water soluble
cationic starch aldehyde derivatives of this invention, the storage
stability of the powder Samples 7 and 9, described in Example 4,
were determined at room temperature by comparing the handsheet wet
strength tests overtime. The results are summarized in Table 2. The
results clearly show the favorable stability properties exhibited
by these cold water soluble powders as no significant wet tensile
strength reduction took place over an extended period of 4 months
to one year.
2TABLE 2 Room temperature stability of cold water soluble cationic
starch aldehyde powder Samples 7 and 9 described in EXAMPLE 4
Sample 7 Sample 9 Time wet strength wet strength (Months) (g/inch)
(g/inch) 0 292 211 1 363 -- 2 315 277 3 387 258 4 330 328 10 -- 218
12 -- 206
* * * * *