BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The invention relates compositions comprising a starch component and papermaking
additives, particularly heat sensitive papermaking additives. The invention further
relates to the application of the compositions to a paper mat at the wet end of the
papermaking process, a method for applying the composition to the paper mat by spraying
and a process for making the composition.
The Related Art
[0002] Additives are generally used in making paper and board to provide desired properties
to the paper and board. In some papermaking processes the additives are applied to
the paper or board with cooked starch. This is particularly the case with additives
having small particle sizes. The use of cooked starch and additives provides a colloidal
suspension which facilitates uniform distribution of the additive in the paper product.
[0003] Colloidal suspensions of cooked starch and additive can be used in the paper pulp
or for a coating. U.S. Patent No. 4,264,325 describes an example wherein an optical
brightening agent is worked into a colloidal solution of cooked starch and water which
is used as size liquor and coated onto paper prior to drying.
[0004] Certain papermaking additives, however, are sensitive to heat. These heat sensitive
papermaking additives will lose some or all of their effectiveness and/or function
when heated at elevated temperatures. When the papermaker desires to use a colloidal
suspension of cooked starch and heat sensitive papermaking additives, the papermaker
must cook the starch prior to incorporating the heat sensitive additive in the colloidal
suspension to avoid losing effectiveness and/or function of the additive. This requires
the papermaker to operate and maintain equipment to cook starch as part of the papermaking
process.
[0005] A composition comprising uncooked starch and heat sensitive papermaking additives
which can be applied to paper within the papermaking process without prior cooking
of the starch, yet provide the benefits of the use of a colloidal suspension of cooked
starch and heat sensitive papermaking additive, would be desired in the art. A method
for applying the uncooked starch and heat sensitive papermaking additives that provides
the benefits of application of cooked starch and heat sensitive papermaking additive
without prior cooking of the starch would also be desired.
[0006] In the present Specification, all parts and percentages are on a weight-by-weight
basis unless otherwise specified. "By weight based on the uncooked starch component"
means the total amount of a particular component of the composition per the total
amount of uncooked starch in the composition.
SUMMARY OF THE INVENTION
[0007] The invention pertains to a composition comprising an uncooked starch component and
papermaking additive, particularly a heat sensitive papermaking additive. The uncooked
starch component and heat sensitive papermaking additive are dry blended. When used
in the papermaking process, the composition is slurried with water and applied to
the paper without cooking the starch component. After application, the paper may be
heated which will cook the starch component; however, we have found that the heat
sensitive papermaking additive is not adversely affected (e.g., does not lose significant,
if any, effectiveness and/or functionality) by heating with the uncooked starch in
the papermaking process, e.g., after being applied to the paper mat.
[0008] The invention further relates to a method for applying the composition comprising
the uncooked starch component and the heat sensitive papermaking additive to the paper
after the paper mat is formed. The uncooked starch component and papermaking additive
can be sprayed onto the paper mat after the mat exits the head box. This type of spray
method is described with respect to the application of starch and fiber mixtures in
the co-pending application owned by the assignee, U.S. Patent Application Ser. No.
10/712,699, filed November 12, 2003 entitled "STARCH AND FIBER MIXTURE FOR PAPERMAKING
AND METHODS OF MAKING PAPER WITH THE MIXTURE", which is incorporated by reference
herein in its entirety.
DESCRIPTION OF THE DRAWINGS
[0009] Fig. 1 is a flow chart showing a papermaking process comprising the application of the uncooked
starch and heat sensitive papermaking additive to a paper mat.
[0010] Fig. 2 is a graph showing brightness gained from an optical brightening agent (y-axis) vs.
amount of optical brightening agent in a handsheet (x-axis) where uncooked pearl starch
and optical brightening agent are sprayed onto the surface of a paper mat.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The composition comprising the uncooked starch component and heat sensitive papermaking
additive composition comprises from about 90% to less than 100%, by weight, of an
uncooked starch component and between more than zero to no more than about 10%, by
weight, of a heat sensitive papermaking additive. When combined with water in the
form of a slurry, the slurried composition comprises from about 0.01% to about 20%,
by weight, uncooked starch component and about 0.01% to about 10%, by weight of the
uncooked starch component, of one or more heat sensitive papermaking additives. The
slurried composition may comprise about 8% to about 12%, by weight, uncooked starch
component and about 0.1 % to about 5%, by weight of the uncooked starch component,
of one or more heat sensitive papermaking additives. The dry mix and slurried composition
may also comprise other papermaking additives that are not considered to be heat sensitive
papermaking additives. The dry mix may consist essentially of or consist of uncooked
starch and heat sensitive papermaking additives.
[0012] Both natural unmodified starch and modified starch can be used for the uncooked starch
component in the composition, each providing equal or about equal performance. Modified
starches may also be used as a dry strength agent in the heat sensitive papermaking
additive component of the invention. Any starch appropriate for use in papermaking
may be used and dextrin, as well as combinations of starch types, dextrin types and
combinations of starches and dextrins. Also, maltodextrins and other forms of carbohydrates
can be used as the starch component. The uncooked starch component comprises material
selected from the group consisting of unmodified starch, modified starch, dextrin,
maltodextrin and combinations thereof.
[0013] Unmodified starch is a commodity chemical produced from the root, stem or fruit from
a number of plants. It is a high molecular weight carbohydrate polymer which is comprised
of linear and branched polysaccharide polymers and it can have moisture content from
about 8% to about 20%, most commonly from about 11 % to about 13%. Starches such as
those derived from corn, wheat, barley, tapioca, rice, potato and/or other suitable
plant source, and the like can be used, as well as hybrids. Blends of starches from
various sources also can be used. Pearl starches and powdered starches may be used.
[0014] Modified starch can be mechanically, chemically or heat modified. Modified starches
have different properties than unmodified starch, including differences in solubility,
film forming, whiteness, gel strength, viscosity stability, adhesivity, resistance
to shear and resistance to freeze-thaw degradation. Starches derived from other genetic
forms of corn, such as high amylose and waxy corn, as well as sorghum varieties, would
also be suitable. Chemically modified starches useful in the invention include modified
oxidized starch such as hypochlorite-oxidized starch, acid thinned starches, cross-bonded
starch, etherified starches, esterified-starches and others which have reduced molecular
weight, high fluidity and/or functional sub groups. Examples of chemically modified
starches which can be used in the invention and are commercially available are SUREBOND®
Industrial Corn Starch or STABLEBOND ® Industrial Corn Starch available from Corn
Products International, Inc., Westchester, Illinois, USA ("Corn Products"). FOXHEAD®
Cationic Starches available from Corn Products and Corn Products' oxidized starch
may also be used in the invention.
[0015] The heat sensitive papermaking additive may be selected from the group consisting
of optical brightening agents, fluorescent agents, dry strength agents, filler particles,
sizing agents, flame retardants, pigments and combinations thereof. Optical brightening
agents that may be used in the invention include BLANKOPHOR® UW liquid and other BLANKOPHOR®
optical brightening agents, available from Bayer Chemicals, Pittsburgh, Pennsylvania,
USA and optical brightening agents from Clariant Corporation, Charlotte, North Carolina,
USA available under the trade name LEUCOPHOR®. Sizing agents useful in the invention
include BASOPLAST® available from BASF Corporation, Mount Olive, New Jersey, USA.
Useful flame retardants include SAFE-T-GUARD® available from FireTech Co., Canyon
Country, California, USA, and useful dry strength agents include the FOXHEAD® modified
starches from Corn Products. Pigments include conventional pigments as well as pigment
types such as solid sphere plastic pigments and hollow sphere plastic pigments, which
are commercially available, such as hollow sphere pigments from Dow Chemical, Midland,
Michigan, USA.
[0016] The dry mix composition comprising starch and heat sensitive papermaking additive
may be made by dry blending the uncooked starch component and heat sensitive papermaking
additive. In one method for making the dry mix, the heat sensitive papermaking additive,
and other optional additives, is added in liquid form into a pneumatic conveyance
line. The liquid droplets are atomized as they enter the conveyance line for drying.
The starch is blown into the pneumatic conveyance line and comes into contact with
the heat sensitive ingredient after the heat sensitive ingredient, and other optional
additives, is atomized in order to dry blend the components. The flow rate of the
starch in the pneumatic conveyance line will determine the rate of addition of heat
sensitive papermaking additive in the pneumatic conveyance line. In an embodiment
of the invention, the air pressure in the pneumatic line is about 60 psi (about 4.2
kg/cm
2) to about 100 psi (about 7.1 kg/cm
2).
[0017] The composition is made up for use at the papermaking facility by adding the uncooked
starch component and heat sensitive papermaking additive composition to water to form
a slurry. The slurry is made by conventional means that would be understood by one
skilled in the art. Generally, the slurry is made by adding the composition to water
so that a homogenous slurry is obtained. The uncooked starch component and heat sensitive
papermaking additives are mixed with water in sufficient quantities and for sufficient
time to thoroughly wet out the starch. The dry mix of uncooked starch component and
heat sensitive papermaking additive is mixed with water in any type of mixing apparatus
at a temperature, such as ambient temperature, so that the starch is not cooked during
the slurrying process.
[0018] The slurry comprising the uncooked starch component and heat sensitive papermaking
additive can be applied as a coating to the paper by conventional means. The slurry
can be applied to a surface of a paper mat, having a top surface and a bottom surface,
during the papermaking process. For example, the uncooked starch component and heat
sensitive papermaking additive slurry can be applied with spraying systems, as well
as with spray bars, curtain coaters, blade coaters, rod coaters, air knife coaters,
roll coaters, size presses, and the like.
[0019] In an embodiment of the invention, the slurry of the uncooked starch component and
heat sensitive papermaking additive is sprayed onto a surface of the paper mat at
the wet end of the papermaking process, such as prior to the nip of the press section.
A papermaking process comprising means for applying the uncooked starch component
and heat sensitive papermaking additive using spraying is shown in
Fig. 1. A pulp and process water stream
1 is sent to a head box
2 by a first means for circulation
3 such as a pump, and the head box
2 deposits the pulp and process water onto the wire screen
4 where the paper web or mat
6, having a top surface
6a and bottom surface
6b, is formed. The pulp and process water is filtered through the mat forming the white
water
5 which is collected in a tray
7 and recycled through the system with or without further processing.
[0020] Referring again to
Fig. 1, the slurry of the uncooked starch component and heat sensitive papermaking additive
is made up in a mixer
8 and sent to a means
9 for applying the slurry of the uncooked starch component and heat sensitive papermaking
additive to the paper mat
6, such as a surface of the paper mat like the top surface
6a. A spray bar or spray nozzle may be used as the means 9. As shown in
Fig. 1, the slurry may be sent through a means for separation
10, such as a filter or pressure screen to remove any large particles, e.g., starch
contaminants. Filters available from RPA Process Technologies USA, Portage, Michigan,
USA may be used. The filter must be properly sealed to prevent pressure drop, particularly
during the cleaning cycle, to provide continuous flow to the means
9 for applying the slurry of the uncooked starch component and heat sensitive papermaking
additive to the paper mats. The accepts
11 from the means for separation
10 are sent to the means
9 for applying the uncooked starch component and heat sensitive papermaking additive
slurry and the rejects
12 are discarded. The uncooked starch component and heat sensitive papermaking additive
slurry is applied to the paper mat
6 after the mat is formed on the wire screen but before the paper mat is further processed
(shown graphically as block
13 in
Fig.1) such as by drying and pressing, like prior to the nip of the press section.
[0021] During the application method, the uncooked starch component and heat sensitive papermaking
additives permeate through the paper mat (e.g., move through the paper mat from the
top surface to the bottom surface) such that at least some of the slurry permeates
to the bottom surface of the paper mat. In this manner, the uncooked starch and heat
sensitive papermaking additive becomes absorbed in the paper mat. The uncooked starch
component prevents the heat sensitive papermaking additive from completely running
through the paper mat. The uncooked starch component also uniformly, or substantially
uniformly, distributes the heat sensitive papermaking additive within the paper mat
and, thus within the finished paper product at the end of the papermaking process.
[0022] During the process for drying the paper mat, the starch component is cooked and gelatinizes,
however, because the drying process does not provide as much direct heat to the heat
sensitive papermaking additive as would occur if the combination of the uncooked starch
component and heat sensitive papermaking additive were directly heated to cook the
starch, the heat sensitive papermaking additive ingredient is not negatively affected
during the heating process and does not loose any or significant effectiveness and/or
function. The papermaker achieves the benefits of the combination of a cooked starch
component and a papermaking additive without the need to separately cook the starch
before adding a heat sensitive papermaking additive. The papermaker does not need
to maintain equipment for cooking the starch and can eliminate a separate starch cooking
step in the papermaking process.
EXAMPLE 1
[0023] Handsheets of paper were made from 100% softwood fibers that were refined in a valley
beater (lab/pilot scale) from Voith Sulzer, Appleton, Wisconsin, USA to about 400
Canadian Standard Freeness ("CSF"). The brightness of the handsheets, without application
of an uncooked starch component and optical brightening agent composition, was determined
to be 75.6 using a Micro S5 brightness/opacity/color meter from Technidyne Corporation,
New Albany, Indiana, USA using the testing procedures described in the operations
manual for the Micro S5 meter.
[0024] A 15% starch slurry was dosed with 5 grams optical brightening agent (BLANKOPHOR®
UW liquid from Bayer Chemicals) per 1000 grams of starch (3005 Pearl Starch from Corn
Products). This slurry was thoroughly mixed and applied to handsheets (made as described
above) using a VEEJET® 8006 spray nozzle from Spraying Systems Co., Wheaton, Illinois,
USA at 275.78 kilopascal (40 psi). The spray nozzle was swept back and forth across
the handsheets (making 2 passes in about 1 second) as soon as the level of the water
dropped below the forming screen of the handsheet mould. Two sheets of blotter paper
and a roll were then used to press the handsheets. The outer sheet of the blotter
paper was then discarded. The handsheet and remaining blotter paper were then placed
in the press felt and run through the roll press. The felt and blotter paper were
removed and the handsheet alone was run through the roll press a final time. The handsheets
were twice run through the roll dryer at 115.56°C (240°F) to cook the starch and dry
the handsheet.
[0025] A 15% starch slurry was dosed with 10 grams of optical brightening agent (BLANKOPHOR®
UW liquid from Bayer Chemicals) per 1,000 grams of starch (3005 Pearl Starch from
Corn Products). This slurry was applied to a handsheet and the handsheet was finished
and dried in accordance with the procedure discussed above with respect to the 5 gram
dose.
[0026] The handsheets having the 5 gram and 10 gram dosages of optical brightening agent
were allowed to condition for a minimum of 24 hours, and were then tested for brightness
using the testing procedures described in the operations manual for the Micro S5 meter
from Technidyne Corporation. Results for brightness are set forth in Table 1. Figure
2 provides a graph of the brightness gained in the handsheet as a result of the addition
of optical brightening agent, based on the average brightness of 75.6 for sheets made
from the same pulp as those in the example, but without having the uncooked starch
and optical brightening agent slurry sprayed on the sheet.
Table 1
Brightness |
Optical Brightening Agent (5 grams) |
Optical Brightening Agent (10 grams) |
UV included |
80.44 |
82.58 |
UV excluded |
76.37 |
76.21 |
FL comp |
4.08 |
6.38 |
[0027] In Table 1, "UV (ultra Violet) included" is the brightness of the paper when exposed
to a light source that contains a fluorescent component. "UV excluded" is the brightness
of the sample when exposed to a light source that has no UV radiation. "FL Comp" is
the amount of brightness added by the inclusion of UV light to the sheet (the difference
between UV Included and UV Excluded).
1. A method of applying heat sensitive papermaking additives to paper during a papermaking
process comprising the steps of
a) providing a dry mix comprising an uncooked starch component and one or more heat
sensitive papermaking additives;
b) adding the dry mix to water to form a slurry without cooking the starch;
c) providing a paper mat having a top surface and a bottom surface;
d) applying the slurry to the top surface of the paper mat and allowing at least some
of the slurry to permeate to the bottom surface of the paper mat; and
e) heating the paper mat after applying the slurry to cook some or all of the starch.
2. The method of Claim 1 wherein the slurry comprises the uncooked starch component in
an amount of from about 0.1 % to about 20%, by weight, and about 0.01 % to about 10%,
by weight of the uncooked starch component, of the heat sensitive papermaking additives.
3. The method of Claim 1 or Claim 2 wherein the heat sensitive papermaking additives
are selected from the group consisting of optical brightening agents, fluorescent
agents, dry strength agents, filler particles, sizing agents, flame retardants, pigments
and combinations thereof.
4. The method of any one of Claims 1 to 3 wherein the uncooked starch component is selected
from the group consisting of unmodified starch, modified starch, dextrin, maltodextrin
and combinations thereof.
5. The method of Claim 4 wherein the unmodified starch or modified starch are derived
from a source selected from the group consisting of corn, wheat, barley, tapioca,
rice, potato and combinations thereof.
6. The method of Claim 4 wherein the unmodified starch or modified starch is pearl starch.
7. The method of any one of Claims 1 to 6 wherein the slurry is applied to the paper
mat by spraying the slurry onto the top surface of the paper mat with a spray bar.
8. The method of any one of Claims 1 to 6 wherein the slurry is applied to the paper
mat by spraying the slurry onto the top surface of the paper mat with a spray nozzle.
9. The method of any one of Claims 1 to 6 wherein the slurry is applied to the paper
mat by means selected from the group consisting of curtain coaters, blade coaters,
rod coaters, air. knife coaters, roll coaters and size presses.
10. The method of any one of Claims 1 to 9 wherein the paper mat is formed by sending
pulp and process water to a head box, having the process water deposited from the
head box onto a wire screen and removing the paper mat from the wire screen.
11. The method of Claim 10 wherein the slurry is applied to the paper mat after the paper
mat is removed from the wire screen.
12. A process for making paper comprising the method of any one of Claims 1 to 9.
13. A process for making paper comprising the method of Claim 10 or Claim 11.
14. Paper made by or obtainable by the process of Claim 12 or Claim 13.
15. A dry mix composition that can be applied to a paper mat in the form of a slurry for
distribution of one or more heat sensitive papermaking additives within the paper
mat comprising from about 90% to less than 100% of an uncooked starch component and
between more than zero to no more than about 10% of a heat sensitive papermaking additive.
16. The composition of Claim 15 wherein the heat sensitive papermaking additives are selected
from the group consisting of optical brightening agents, fluorescent agents, dry strength
agents, filler particles, sizing agents, flame retardants, pigments and combinations
thereof.
17. The composition of Claim 15 wherein the uncooked starch component is selected from
the group consisting of unmodified starch, modified starch, dextrin, maltodextrin
and combinations thereof.
18. The composition of Claim 17 wherein the unmodified starch or modified starch are derived
from a source selected from the group consisting of corn, wheat, barley, tapioca,
rice, potato and combinations thereof.
19. A paper mat comprising a slurry of the dry mix composition of any one of Claims 15
to 18 and water.
20. A process for making a dry mix composition comprising the steps of blowing starch
into a pneumatic conveyance line having an air pressure of about 60 psi to about 100
psi and adding heat sensitive papermaking additive and optional additive in liquid
form into the pneumatic conveyance line wherein the heat sensitive papermaking additive
and optional additive are atomizied as the heat sensitive papermaking additive and
optional additive enter the conveyance line.