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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to cellulosic substrates having improved wet
strength and to a method for producing such substrates.
2. Description of the Prior Art
U.S. Pat. 2,834,675, issued May 13, 1958 discloses resinous compositions of
dihaloalkanes and alkylene diamine which may be added to paper pulp to
improve wet strength.
German Patent No. 955,835, published Jan. 10, 1957, discloses processes for
water-proofing paper by adding to the pulp basic products free from
reactive halogen or epoxy groups obtained by condensing polyamides with
cross-linking compounds such as epichlorohydrin or dichloroethane. Such
products also increase the wet strength of paper.
U.S. Pat. No. 2,595,935, issued May 6, 1952, discloses paper products of
improved wet strength containing reaction products of alkylene diamine and
bifunctional or polyfunctional halohydrins such as epichlorohydrin.
These prior art resinous compositions, although increasing wet strength,
have other disadvantages which often makes them commercially
unsatisfactory. For example, a resinous composition prepared by the
reaction of dichloroethane and a alkylene diamine such as ethylenediamine
is unsatisfactory in that it takes a long time to cure, in some instances,
up to a year. It also is very inefficient, requiring appreciable amounts
to obtain adequate wet strength. Likewise, one produced by reacting
epichlorohydrin and a alkylene diamine such as hexamethylenediamine is
less efficient.
Canadian Pat. No. 776,566 discloses wet and dry strength improvers obtained
by reacting a polyamine having the formula
NH.sub.2 (Cm H.sub.2m NH).sub.p CmHm NH.sub.2
where m is an integer from 2 to 4 and p is an integer from 1 to 4 with an
unbranched dihaloalkane of the formula X(CH.sub.2).sub.y X wherein X is a
halogen and y is 2 or 3, and then reacting the amine prepolymer so formed
with an epihalohydrin.
It has however, been found that such products have several grave
disadvantages in that the amine prepolymers can only be prepared at low
ratios of halogen equivalents to amine equivalents because at higher
ratios, the product gels and is useless for further reaction. In addition,
the further reaction with epihalohydrin is also restricted by the need to
avoid gelation. In practice, this means less efficient use of the
expensive amine and epihalohydrin components. Moreover, it is found that
they are much inferior, as wet and dry strength resins, to the resins of
the present invention.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with this invention, it has been surprisingly found that a
cellulosic composition with improved wet strength is provided by treating
a cellulosic substrate with a sufficient amount of a cationic resinous
composition and curing the resinous composition to its insoluble state
after such application. The cationic resinous composition useful in the
production of such improved cellulosic compositions comprise the reaction
product of
(A) an adduct of
(1) a dihaloalkane represented by the formula
##STR1##
wherein X represents chloro, bromo or iodo, R represents hydrogen, hydroxy
or an alkyl group having 1 to 4 carbon atoms, and n is 0 or 1 and
(2) a alkylene diamine represented by the formula
H.sub.2 N C.sub.m H.sub.2m NH.sub.2 Formula II
wherein m is an integer of from 4 to about 15 in a mole ratio of from about
0.5:1 to about 0.95:1 and
(B) an epihalohydrin selected from the group consisting of epichlorohydrin,
epibromohydrin and epiiodohydrin,
in a mole ratio of from about 1.25 to about 2.5 moles of epihalohydrin per
mole of amine group in the adduct.
DETAILED DESCRIPTION OF THE INVENTION
Preferably, the resinous compositions which are applied to cellulosic
substrates in accordance with this invention are produced using water as a
solvent. For ease and convenience, this reaction is run such that the
aqueous solution obtained by reacting the adduct with the epihalohydrin
contains about 40% resin solids. Resin solids of the aqueous solution are
determined by totaling the weight of the reactants employed, and then
dividing by the total weight of the solution including any water added. By
controlling the reaction, aqueous solutions can be obtained having any
desired viscosity. Generally, they have a viscosity at 40% resin solids on
the Gardner-Holdt scale at 25.degree. C. of from A to Z, preferably D to
H.
The aqueous solutions may be adjusted to any resin solids concentration to
facilitate use when applied to cellulosic substrates. Solutions having a
resin solids level of from about 5 to 40%, preferably 20 to 35% and a pH
lower than 6.degree. at 25.degree. C. are stable for extended period of
time, i.e., over 3 months. A pH of 4.5 to 5.5 is preferred. Generally, the
pH is always at least 3, so the solutions can be used in stainless steel
equipment. Aqueous solutions having a high concentration of resin solids
are preferred to reduce costs, when the solutions must be transported long
distances.
Generally, aqueous solutions of the novel resinous compositions in which
the epihalohydrin is reacted with the adduct in a molar proportion of
epihalohydrin to amino group of the adduct above 2.5:1 are not
thermosetting and those below 1.25:1 generally gel. Preferably, the molar
proportion is from about 1.5:1 to about 2.25:1.
The adducts of this invention obtained by reacting the dihaloalkane with
the alkylene diamine contain essentially linear or branched units with
little or no cyclic units. It is preferred that about 85% of the units of
the adducts be linear or branched with more than 95% being preferred. They
are generally prepared using as a solvent water, water miscible alcohols
or mixtures thereof. Aqueous solutions are clear, pale yellow having a pH
of from about 8 to 11 at 25.degree. C. Any concentration of the adduct can
be used as long as it is suitable for further reaction with the
epihalohydrin. A suitable concentration of adduct is from about 25 to 55%
by weight, based on the total weight of the solution of adduct. Likewise,
the concentration may be adjusted by the addition or removal of solvent to
give any desired viscosity. For example, a viscosity of about A to H on
the Gardner-Holdt scale at 25.degree. C. is suitable for reacting with
epihalohydrin.
Illustrative dihaloalkanes represented by Formula I when n is 0 include
1,2-dichloroethane, 1,2-dibromoethane, 1,2-diiodoethane; and where n is 1
include 1,3-diiodopropane, 1,3-dichloro-2-methyl propane,
1,3-dibromo-2-butyl propane, 1,3-dichloro-2-isobutyl propane,
1,3-dichloro-2-hydroxy-methyl propane, and 1,3-dibromo-2-hydroxy propane.
It is preferred that n be 0 and 1,2-dichloroethane is especially
preferred.
As mentioned, those dihaloalkanes represented by Formula I when reacted
with the proper alkylene diamine of this invention form adducts containing
essentially linear or branched units. .alpha.,.omega.-Dihaloalkanes
containing 4 to 6 carbon atoms between the halo substituents from
piperidine type structures and are not suitable as the major proportions
of the adduct in the practice of this invention. However, adducts
containing cyclic units may be used to replace a portion of the linear or
branched units of the adduct of this invention, i.e., up to about 15 to
20%.
Adducts of this invention possessing substantially the same properties as
the adducts prepared using .alpha.,.omega.-dihaloalkanes represented by
Formula I, which can be prepared in the same maner and are equivalents
thereof are those wherein the .alpha.,.omega.-dihaloalkanes contains over
6 carbon atoms. Such diahaloalkanes include 1,7-dichloroheptane,
1,3-dibromopentane and 1,12-dichlorododecane. Likewise, adducts of this
invention possessing substantially the same properties as the adducts
prepared using .alpha.,.omega.-dihaloalkanes represented by Formula I, or
the equivalent .alpha.,.omega.-dihaloalkanes containing more than 6 carbon
atoms, which can be prepared in the same manner and are equivalents
thereof are those wherein the .alpha.,.omega.-dihaloalkanes have one, two
or more simple substituents, including but not limited to, lower alkyl,
e.g., methyl, ethyl, butyl; nitro; sulfate; sulfonyloxy; carboxy;
carbo-lower-alkoxy, e.g., carbomethoxy, carbethoxy; amido, hydroxy;
lower-alkoxy, e.g., methoxy, ethoxy, and lower-alkanoyloxy, e.g., acetoxy.
Illustrative alkylene diamine represented by Formula II include
1,4-tetramethylenediamine, 1,5-pentamethylenediamine,
1,6-hexamethylenediamine, 1,10-decamethylenediamine,
1,12-dodecamethylenediamine and 1,15-pentadecylmethylenediamine. It is
preferred that m be from 4 to 10 and 1,6-hexamethylenediamine is
especially preferred.
As mentioned, the adducts of this invention contain essentially linear or
branched units. Alkylene diamine represented by Formula II will form these
adducts when reacted with the proper dihaloalkane. Adducts containing a
major proportion of cyclic units are not suitable in the practice of this
invention. However, a minor proportion, i.e., 15 to 20% of the adduct of
this invention may be replaced with adducts containing essentially all
cyclic units.
Adducts of this invention possessing substantially the same properties as
the adducts prepared using alkylene diamine represented by Formula II,
which can be prepared in the same manner and are equivalents thereof are
those (1) wherein the alkylene diamine contains more than 15 carbon atoms
such as 1,19-nonadecyldiamine; (2) wherein the alkylene diamine bears one,
two, or more simple substituents including but not limited to lower alkyl,
e.g., methyl, ethyl, butyl; nitro; sulfate; sulfonyloxy; carboxy;
carbo-lower-alkoxy, e.g., carbomethoxy, carboethoxy; amido; hydroxy;
lower-alkoxy, e.g., methoxy, ethoxy and lower-alkanoyloxy, e.g., axcetoxy
or (3) wherein the alkylene diamine contain more than 15 carbon atoms and
bears one, two or more simple substituents described in (2) above.
Epichlorohydrin, epibromohydrin and epiiodohydrin are the epihalohydrins
that may be used in the practice of this invention.
Examples of adducts and resinous reaction products defined by the above
formulae are shown in the following tables.
TABLE I
__________________________________________________________________________
ADDUCT
Dihaloalkane Alkylene diamine
Mole Ratio*
__________________________________________________________________________
A 1,3-dichloro-2-hydroxy propane
+ 1,6-hexamethylenediamine
0.7
B 1,3-dichloro-2-ethyl propane
+ 1,10-decamethylenediamine
0.85
C 1,2-dichloroethane
+ 1,6-hexamethylenediamine
0.90
D 1,3-dichloro-2-butyl propane
+ 1,8-octamethylenediamine
0.6
E 1,2-dibromopropane
+ 1,14-tetradecamethylenediamine
0.95
__________________________________________________________________________
*dihaloalkane:alkylene diamine
TABLE II
______________________________________
RESINOUS REACTION PRODUCT
Sample Adduct* Epihalohydrin
Mole Ratio**
______________________________________
1 A + epichlorohydrin
1.25:1
2 B + epiiodohydrin
1.5:1
3 C + epichlorohydrin
1.75:1
4 D + epibromohydrin
1.25:1
5 E + epichlorohydrin
2.25:1
______________________________________
*From Table I
**Moles of epihalohydrin per mole of amine group in said alkylene diamine
The dihaloalkanes defined by Formula I are reacted with alkylene diamine
defined by Formula II with constant stirring over a prolonged period, care
being taken to control addition of the dihaloalkane to the diamine such
that the exothermic reaction does not cause a substantial rise in the
reaction temperature.
For example, the dihaloalkanes are reacted with the alkylene diamine in the
aforementioned ratios at a temperature range of from about 25.degree. C.
to reflux or above preferably from about 60.degree. C. to 90.degree. C. in
a solvent such as water, water miscible alcohols or mixtures thereof.
Water is preferred. Any suitable solids content of the reactants in the
reaction mixture may be employed. It is most advantageous that initially
they be high, 60 to 90% by weight, based on the total weight of the
reaction mixture.
As the reaction proceeds, the viscosity increases, it is conveniently kept
from G to S on the Gardner-Holdt scale by the addition of solvent.
Viscosity is measured at 25.degree. C. In order to maintain a reasonable
reaction rate any strong base or other acid acceptor may be added to
neutralize any HCl formed. These bases include alkali metal hydroxides or
alkali metal alkoxides.
The reaction is carried out until there are substantially no free
dihaloalkanes present in the reaction mixture.
The adduct may be reacted with epihalohydrin according to the procedure
described in U.S. Pat. No. 2,595,935 which is incorporated herein by
reference.
For example, epihalohydrin is added to the adduct in the presence of a
solvent such as water, water miscible alcohols or mixtures thereof at a
temperature range of from about 25.degree. to 45.degree. C. preferably
from about 25.degree. to 35.degree. C. over a period of 10 minures to 120
minutes preferably 30 minutes to 90 minutes. The solids concentration of
the reactants in the reaction mixture during the reaction is from about
20% to about 60%, by weight, preferably from about 30% to about 40%, based
on the total weight of the reaction mixture. After addition is complete,
the temperature is raised by the addition of heat to about 60.degree. to
about 80.degree. C. Reaction is continued at this temperature range by the
addition of more heat until the resinous reaction product reaches a
viscosity at 40% resin solids measured at 25.degree. C. on the
Gardner-Holdt scale within the order of A to about Z preferably from about
D to about H. The pH is reduced by the addition of a suitable acidic
substance, well known to those skilled in the art such as H.sub.2
SO.sub.4, HCl, etc.
As stated above, the resinous reaction products of this invention are
particularly valuable as wet strength improvers for cellulosic substrates,
particularly paper. Paper, in accordance with this invention, includes all
materials which are encompassed within the ordinary and usual meaning of
the word. Generally speaking, paper includes cellulosic and other
vegetable fibers formed into thin felts or nonwoven sheets.
Aqueous solutions of the resinous compositions are particularly valuable in
increasing the wet strength of paper. Generally, they contain 5 to 40% of
uncured resin solids, preferably 20 to 35%; and 60 to 95%, preferably 65
to 80% by weight of water, based on the total weight of the aqueous
solution. Any concentration of the uncured resin solids may be used to
increase the wet strength of paper except as limited by handling
conditions. Likewise, they can be used at any viscosity except as limited
by handling conditions.
When the resinous compositions are applied to cellulosic paper products of
various types, conventional techniques known to those skilled in the art
may be used. Thus, for example, preformed and partially or completely
dried paper may be impregnated by immersion in, or spraying with, an
aqueous solution of the resin following which the paper may be heated for
about 0.5 to 30 minutes at temperatures of 90.degree. C., to 100.degree.
C. or higher to dry same and cure the resin to a water insoluble
condition. The resulting paper has increased wet strength, and, therefore,
this method is well suited for the impregnation of paper towels, absorbent
tissue and the like to impart wet strength characteristics thereto.
The preferred method of incorporating these resins in paper, however, is by
internal addition prior to sheet formation whereby advantage is taken of
the substantivity of the resins for hydrated cellulosic fibers. In
practicing this method an aqueous solution of the resin in its uncured and
hydrophilic state is added to an aqueous suspension of paper stock in the
beater, stock chest, Jordan engine, fan pump, head box or at any other
suitable point ahead of sheet formation. The sheet is then formed and
dried in the usual manner, thereby curing the resin to its polymerized and
water insoluble condition and imparting wet strength to the paper.
The cationic thermosetting resins herein disclosed impart wet strength to
paper when present therein in amounts of about 0.1-5% or more based on the
dry weight of the paper. The quantity of resin to be added to the aqueous
stock suspension will depend on the degree of wet strength desired in the
finished product and on the amount of resin retained by the paper fibers.
The uncured cationic thermosetting resin incorporated in paper in any
suitable manner, as described above, may be cured under acid, neutral or
alkaline conditions, i.e., at pH's from about 3.0 to 13 by subjecting the
paper to a heat-treatment for about 0.5 to 30 minutes at a temperature
from about 90.degree. to 100.degree. C. Optimum results, however, are
obtained under alkaline conditions. For example, in those applications
where short cure times are required, for example, fine papers such as
sanitary tissues, the resinous compositions may be made alkaline (pH 8-13)
prior to use. Such a pretreatment results in shorter cure times and
increased wet strength. Any strong base may be used such as alkali metal
hydroxides or alkoxides. Sodium hydroxide is preferred.
The following Examples illustrate the invention.
EXAMPLE I
Fifty-eight grams (0.5 mole) of 1,6-hexamethylenediamine is placed in a
4-necked flask equipped with a thermometer, mechanical stirrer, condenser
and an additional funnel. To this is added 10.2 grams of water and the
mixture heated externally to 70.degree. C. Forty-two grams (0.43 mole) of
1,2-dichloroethane is added at a rate slow enough to keep the reaction
temperature below 75.degree. C., .about.3 hours addition time. Water, 8
grams at a time, is added during this 3 hour period to keep the reaction
viscosity below Gardner S. When the addition of 1,2-dichloroethane is
complete, add 8 grams of 50% aqueous sodium hydroxide. Maintain the
reaction at 70.degree. C. until the viscosity reaches Gardner V. At this
point, add 8 grams of water and raise the temperature to 80.degree. C.
Maintain 80.degree. C. until the viscosity reaches Gardner T. Add 315
grams of water and cool the mixture to 25.degree. C. To this mixture, over
a 1 hour period, add 184.8 grams (2 moles) of epihalohydrin allowing the
reaction temperature to raise to 45.degree. C. After an additional hour at
45.degree. C., raise the reaction temperature to 65.degree. C. and
maintain until the viscosity of the solution reaches Gardner D. At this
viscosity, add 9 grams of 98% by weight sulfuric acid and 227 grams of
water. Adjust the final pH to .about.5 and the final solids to 25% with
additional sulfuric acid and water.
An actual experimental run of the above procedure yielded 1200 grams of a
solution containing 25% solids and having a pH of 4.5 at 25.degree. C.
EXAMPLE II
Following the procedure of Example I, the adducts and resinous reaction
products set out in Tables III and IV are prepared by substituting for
1,2-dichloroethane, 0.43 mole of 1,2-dibromoethane, 0.43 mole of
1,2-diiodoethane, 0.43 moles of 1,3-dichloro-2-methyl propane, 0.43 mole
of 1,3-diiodo-2-butyl propane or 0.43 mole of 1,3-dichloro-2-isobutyl
propane; or for epichlorohydrin 2 moles of epiiodohydrin, or 2 moles of
epibromohydrin; or for 0.5 mole of 1,5-hexamethylenediamine 0.5 mole of
1,5-pentamethylenediamine, 0.5 moles of 1,7-heptamethylenediamine or 0.5
moles of 1,12-dodecamethylenediamine.
TABLE III
__________________________________________________________________________
ADDUCT
Dihaloalkane Alkylene diamine
Mole Ratio*
__________________________________________________________________________
A 1,2-dibromoalkane
+ 1,6-hexamethylenediamine
0.86:1
B 1,2-diiodoalkane
+ 1,6-hexamethylenediamine
0.86:1
C 1,3-dichloro-2-methylpropane
+ 1,6-hexamethylenediamine
0.86:1
D 1,3-diiodo-2-butylpropane
+ 1,6-hexamethylenediamine
0.86:1
E 1,3-dichloro-2-isobutylpropane
+ 1,6-hexamethylenediamine
0.86:1
F 1,2-dichloroalkane
+ 1,3-pentamethylenediamine
0.86:1
G 1,2-dichloroalkane
+ 1,7-heptamethylenediamine
0.86:1
H 1,2-dichloroalkane
+ 1,12-didecamethylenediamine
0.86:1
__________________________________________________________________________
*Dihaloalkane: alkylene diamine
TABLE IV
______________________________________
RESINOUS REACTION PRODUCT
Adduct* Epihalohydrin Mole Ratio**
______________________________________
1 A + epibromohydrin
2:1
2 B + epiiodohydrin
2:1
3 C + epichlorohydrin
2:1
4 D + epichlorohydrin
2:1
5 E + epichlorohydrin
2:1
6 F + epichlorohydrin
2:1
7 G + epibromohydrin
2:1
8 H + epibromohydrin
2:1
______________________________________
*from Table III
**Moles of epihalohydrin per mole of amine group of the adduct
EXAMPLE III
Following the procedure of Example 1, the adducts and resinous reaction
products set out in Tables III and IV are prepared but at different mole
ratios. They are described in Tables V and VI.
TABLE V
______________________________________
ADDUCT
Adduct Mole Ratio
______________________________________
1 A 0.7:1
2 A 0.8:1
3 A 0.9:1
4 B 0.6:1
5 B 0.5:1
6 B 0.94:1
7 C 0.85:1
8 D 0.6:1
9 E 0.65:1
10 F 0.55:1
11 F 0.78:1
12 G 0.9:1
13 H 0.89:1
______________________________________
TABLE VI
______________________________________
RESINOUS REACTION PRODUCTS
Adduct of Table V
Epihalohydrin
Mole Ratio*
______________________________________
1 A epibromohydrin
2.25:1
2 A epibromohydrin
1.25:1
3 A epibromohydrin
1.6:1
4 B epiiodohydrin
2.45:1
5 B epiiodohydrin
1.45:1
6 B epiiodohydrin
1.9:1
7 C epichlorohydrin
1.85:1
8 D epichlorohydrin
2:1
9 E epichlorohydrin
2.0:1
10 F epichlorohydrin
2.25:1
11 F epichlorohydrin
1.9:1
12 G epibromohydrin
1.8:1
13 H epibromohydrin
1.45:1
______________________________________
*Mole of epihalohydrin per mole of amine group of the adduct.
EXAMPLE IV
To an aqueous pulp slurry of 0.5% consistency and pH of 8.0 composed of
unbleached softwood kraft fibers beaten to a Canadian standard freeness of
455 ml is added the appropriate amount of the thermosetting resin of
Example I. The pulp slurry is readjusted to pH 8 with 1% sodium hydroxide
and stirred briefly to allow the resin to distribute on the pulp. The
fibers are formed into a wet-laid web having a consistency of 34% on a
Noble and Wood lab handsheet machine. The wet sheets are pressed on a
material felt and dried for 2 minutes on a lab down drier at 204.degree.
F. The resulting 2.5 g. 8" .times. 8" handsheet is cut into 1" .times. 8"
strips. The strips are oven cured for 10 minutes at 105.degree. C. The
cured strips are soaked in water for 10 minutes and tested for wet
strength.
An actual run of the above procedure gave the results set out in Table VII.
TABLE VII
______________________________________
Wet Tensile
Sample Resin Level % lb./inch*
______________________________________
1 0 0.6
2 0.25 3.17
3 0.50 5.20
4 0.75 5.91
______________________________________
*measured using Instron Tensile Tester
EXAMPLE V
Following the procedure of Example IV, the resinous reaction products set
out in Table IV are used in place of the thermosetting resin of Example I.
EXAMPLE VI
Following the procedure of Example IV, the resinous reaction products set
out in Table VI are substituted for the thermosetting resins of Example I.
The following Examples are included to demonstrate that the wet strength
resins of the present invention are quite different and superior to those
exemplified by the disclosures in Canadian Pat. No. 776,566.
The Canadian patent describes resins formed by the reaction of a prepolymer
formed from a dihaloalkane and a alkylene diamine poly-alkylene polyamine
of the formula NH.sub.2 (C.sub.m H.sub.2m NH).sub.p C.sub.m H.sub.2m
NH.sub.2 where p is 1 to 4 and m is 2 to 4, and an epihalohydrin.
It has surprisingly been found that such resins are markedly inferior to
resins prepared using as the original amine a simple .alpha.,
.omega.-diamine. Moreover, this superiority is shown whether the resins
are compared on a weight for weight basis or on the basis of the ratio of
epihalohydrin to amine equivalents (E/A) in the reaction.
The Examples illustrating this discovery are in two groups.
The first group of Examples, VII, VIII and IX, illustrate the comparative
processes for the production of the amine prepolymer. Example VII is a
reproduction of the Example in the Canadian patent and covers both
possible interpretations of the instructions, (i.e. staged addition of the
dihaloalkane or "all-at-once"). Example VIII duplicates Example VII with
the difference that an equal weight of hexamethylene diamine is
substituted for the iminobispropylamine (IBPA). Example IX compares the
production of the amine prepolymers of Examples VII and VIII using as
nearly as possible the same ratio of amine equivalent to halide
equivalent, as opposed the same weights of reactants.
The second group illustrates the production of wet strength resins using
the prepolymer prepared according to the processes described in the first
group. Example X shows the production of a wet strength resin according to
the invention and Example XI describes the preparation of a resin with a
similar E/A ratio but with the difference that the prepolymer was based on
IBPA. Table VIII compares the wet strengths of paper treated with the two
resins. Example XII describes the production of a resin using the same
weight of prepolymer as was used in Example X with the difference that the
prepolymer was based on IBPA. Table IX compares the performance of the
Example X and XII resins. Example XIII describes the production of resins
using as the initial amine 1,3-propane diamine. These resins are
comparable with those of Example X on a weight/weight basis and Table X
sets forth a comparison of the performance of the two resins.
EXAMPLE VII
This Example describes the production of an amine prepolymer using
3,3'-iminobispropylamine (IBPA) as the initial amine reactant. In both
methods described the >CHCl/>NH equivalent ratio is 0.589.
Method A
A one liter, four-necked flask equipped with stirrer, thermometer, addition
funnel and condenser was charged with 198 grams (1.509 moles and 4.527
amine equivalents) of IBPA and 90 grams of deionized water. The flask was
heated to 72.degree. .+-. 2.degree. C. and the slow dropwise addition of
dichloroethane (132 grams, i.e., 1.333 moles and 2.667 equivalents of
>CHCl) was initiated. The addition was accompanied by stirring and was
completed in 2 hours.
The temperature of the reaction mixture was gradually raised to 80.degree.
C. for a further four hours. The mixture was diluted by addition of a
further 240 g. of deionized water.
The Gardner viscosity of the product was V and the solids content
(theoretical 50%) was found to be 45.7%. The amine equivalents were found
to be 2.83 meq./g.
Method B
A 500 ml flask equipped as is described in Method A was charged with 99.0
grams of IBPA (0.745 mole) and 45.0 grams of deionized water. The flask
was then cooled to about 2.degree. C. and 66.0 grams (0.667 mole and 1.333
equivalents of >CHCl) of dichloroethane were added, with stirring over a
very short span.
The temperature began to rise rapidly but cooling was applied to keep the
temperature below about 75.degree. C. After a reaction time of 2 hours 50
minutes the resin product was cooled and the reaction terminated. 120G. of
deionized water were then added.
The Gardner viscosity of the mixture was D.sup.+ /E.sup.- and the total
solids (theoretical 50%) were found to be 45.86%. The product was found to
contain 3.278 meq/g.
EXAMPLE VIII
This Example describes the production of an amine prepolymer using a
diamine. These methods duplicate the methods described in Example VII
using a similar dichloroethane/amine weight ratio but substituting
hexamethylene diamine for IBPA.
Method A
The apparatus and process steps were as described in Example VII (Method
A), except that the reactants charged were 130.8 g. (0.852 mole) of 75.7%
assay hexamethylene diamine (HMD), 13.2 g. of deionized water and 66 g. of
dichloroethane (0.667 mole, 1.333 equivalent of >CHCl) were added dropwise
over a period of three hours.
The temperature of the reaction mixture, after completion of the addition
of the dichloroethane, was raised to 80.degree. C. over a period of 1.5
hours and maintained at that temperature for 4 hours. The solution was
then cooled, diluted to a theoretical 50% solids by addition of 120 g. of
deionized water.
The Gardner viscosity was found to be B.sup.+ and the solids content was
48.13%. The amine content was determined via titration to be 1.252 meq./g.
Method B
This method duplicates that of Example VII, Method B, except that HMD is
substituted for IBPA.
The reactants charged were 130.8 g (0.852 mole) of 75.7% assay HMD and 13.2
g. deionized water and 66.0 g. (0.667 mole and 1.333 equivalents of >CHCl)
were added at once with stirring. After the reaction the solution was
diluted to a theoretical 50% solids by addition of 120 g. of deionized
water.
The Gardner viscosity was found to be A-1/2 and the actual total solids was
46.63%. The total amine content was determined to be 1.688 meq./g.
It should be noted that in the methods described in Example VIII the
viscosity of the 50% solids solution is substantially lower than the
viscosity of the corresponding products described in Example VII.
EXAMPLE IX
Examples VII and VIII were run at the same weight ratio of amine to
dichloroethane and it was clearly shown that the Gardner viscosity of the
product obtained using HMD was lower than that obtained using IBPA, both
being at the same total solids level.
However, to be complete the comparison should be made at the same
equivalent ratio of chloride to amine groups. In the following Methods A
and B an attempt was made to make such a comparison.
Method A
A half-liter 4-necked flask equipped with condenser, stirrer, thermometer
and addition funnel was charged with 77.2 g. (0.50 mole, 1.0 amine
equivalent) of 75.7% assay HMD (18.76 % water).
Dichloroethane (42.6 g., i.e. 0.43 mole, 0.86 >CHCl equivalent) was added
dropwise over three hours while the temperature was maintained at
72.degree.-73.degree. C. after which the mixture was stirred for a further
45 minutes at 73.degree.-75.degree. C. Thereafter, 8.0 g. of water and 8.0
g. of 50% sodium hydroxide were added and the temperature was raised to
80.degree. C. After a further hour and again after two hours, 8.0 g. of
water were added. Two and a half hours after the last water addition the
reaction terminated.
The mixture had a theoretical 50% total solids (formed 47.8%) and a Gardner
viscosity of C/C.sup.+. The theoretical amine equivalent of the prepolymer
was 1.161 meq/g. and the determined value was 1.374 meq/g.
Method B
This is an attempt to duplicate Method A using IBPA in place of HMD using
the same apparatus and reaction conditions.
The reaction vessel was charged with 58.4 g. (0.445 mole, 1.336 amine
equivalent) of IBPA and 18.8 g. of deionized water. Dropwise addition of
42.6 g (0.43 mole, 0.86 >CHCl equivalent) of dichloroethane took place
over a period of 3 hours. It was necessary to add 8.0 g. of water after 2
hours and on completion of the addition 8.0 g. of 50% sodium hydroxide
were added. After a further hour a further 8.0 g. of water were added and
the temperature was raised to 80.degree. C. Fifteen minutes later 8.0 g.
of water were added and a further 8.0 g. of water fifty-five minutes
later. An hour later the reaction mixture had gelled and the reaction was
discontinued.
It should be noted that using an even higher >CHCl/>NH equivalent ratio,
0.783, HMD gave an amine-prepolymer with a Gardner viscosity of C/C.sup.+
whereas the IBPA prepolymer gelled at an equivalent ratio of 0.644.
However, the reaction mixture did not gel when the same ratio was only
0.589, (Example VII, Method A), though the Gardner viscosity did reach V.
It is apparent therefore that using a diamine it is possible to reach a
higher >CHCl/>NH ratio than is possible using an iminobis-amine such as
IBPA. This in turn means that the amine is used more efficiently in
producing the amine prepolymer.
EXAMPLE X
This Example illustrates the production of a wet strength resin using the
prepolymer of Example VIII (Method A).
A reaction vessel fitted with condenser, thermometer, stirrer and dropping
funnel was charged with 38.75 g. of the amine prepolymer prepared in
Example VIII, (Method A), and 31.46 g. of epichlorohydrin (0.340 mole,
epichlorohydrin/amine ratio - E/A = 1.70) were added dropwise with
stirring over an hour. The temperature rose during the reaction from an
initial 25.degree. C. to 60.degree. C. after 3 hours and was held at this
temperature for a further 11/2 hours. After 31/2 hours and again after 4
hours 1.6 g. of 50% aqueous sodium hydroxide were added. After 41/2 hours
total reaction time the reaction was killed by addition of 30 g. of
deionized water and 2.2 g of 96% sulphuric acid.
The total solids - the reaction mixture was found to be 26.86% (32.2% is
theoretical) and the Gardner viscosity of this mixture was E. The product
yield was 83.4% of theoretical.
EXAMPLE XI
This Example is a re-run of Example X using as the amine prepolymer the
product of Example VII (Method A).
The same apparatus as was used in Example X was charged with 36.45 g. of
the amine prepolymer product of Example VII (Method A). To this prepolymer
were added 39.33 g. (0.425 mole) of epichlorohydrin, giving the same E/A
ratio of 1.70.
After 2 hours, 40 minutes the reaction was nearing gelation and was killed
by addition of 30.0 g. of deionized water and 3.0 g. of 96% sulphuric
acid.
The Gardner viscosity, at 25.48% solids. (theoretical is 34.35%) was
E.sup.+ /F.sup.- and the yield was 74.2% of theoretical.
The resin produced according to this Example was compared in terms of its
wet strength with the resin produced according to Example X.
The wet strength was measured by the method described in Example IV except
that the pulp was a 50:50 bleached hardwood/softwood Kraft blend with a
Canadian Standard Freeness of 452, the pH of the slurry was 7 and the web
consistency was 36.1%. The samples were divided into two lots: those for
uncured and those for cured wet strength testing. The latter were cured at
90.degree. C. for 15 minutes. Before testing in an Inston Tensile Tester
each sample was soaked in deionized water for 10 minutes. The results are
set forth in Table VIII.
TABLE VIII
______________________________________
Wet Strength (lbs/in)
Application
Uncured Cured
Resin of: Level lbs/ton
(Average of 4)
(Average of 4)
______________________________________
Example X 5 1.95 3.10
(Invention)
.10 2.85 4.53
15 3.62 5.56
Example XI
5 1.45 2.23
(Comparative)
10 2.00 3.06
15 2.52 3.55
______________________________________
It will be observed that the wet strength of papers treated with the resins
of the invention are very much better than those prepared by the process
of this Example XI. This factor plus the greater yield obtained in the
process of Example X by comparison with Example XI and the better
controllability of the viscosity changes make the resin of Example X much
superior to that of Example XI. This effect is the more surprising in that
the same E/A ratio was used to prepare each resin.
EXAMPLE XII
As indicated above the resins produced in Examples X and XI were compared
on the basis of their identical E/A ratio. However, they necessarily used
different weights of the amine prepolymer. This Example describes the
production of a wet strength resin that is produced using the amine
prepolymer of Example VII (Method A) in a weight ratio to epichlorohydrin
that is substantially the same as was used in Example X. The major
difference between this reaction and that described in Example X is that
this is run at 30% total solids instead of 50% total solids. This change
was essential because an attempt to run at the higher figure resulted in a
gelled-up reaction.
The apparatus used in Example X was charged with 40.8 g. (0.28 potential
amine equivalents) and 94.79 g. of deionized water. E | | |
