EP1951955A1

EP1951955A1 - A paper substrate having enhanced print density

Info

Publication number: EP1951955A1
Application number: EP06827277A
Authority: EP
Inventors: Jay C. Song; Sen Yang; Yan C. Huang; Kapil M. Singh; Michael F. Koenig; David B. Shelmidine
Original assignee: International Paper Co
Current assignee: International Paper Co
Priority date: 2005-11-01
Filing date: 2006-11-01
Publication date: 2008-08-06
Anticipated expiration: 2026-11-01
Also published as: PT1951955E; WO2007053681A1; PL1951955T3; ES2402210T3; CA2627050A1; BRPI0619648B1; CN101351596A; EP2511419A1; PL2511419T3; EP2511419B1; JP4995831B2; CA2627050C; ES2455616T3; BRPI0619648A2; MX358994B; MX339400B; PT2511419E; JP2009513843A; EP1951955B1; RU2008121128A

Abstract

The present invention relates to a sizing composition that, when applied to paper substrate, creates a substrate, preferably suitable for inkjet printing, having increased print density, print sharpness, low HST, and/or image dry time, the substrate preferably having high brightness and reduced color-to-color bleed as well. In addition, the present invention relates to a method of reducing the HST of a paper substate by applying the sizing composition to at least one surface thereof. Further, the application relates to methods of making and using the sizing composition, as well as methods of making and using the paper containing the sizing composition.

Description

A PAPER SUBSTRATE HAVING ENHANCED PRINT DENSITY

The present application claims the benefit of priority under 35 USC § 119(e)

to United States Provisional Patent Application 60/732,828 , filed November 1,

2005, which is hereby incorporated, in its entirety, herein by reference.

Field of the Invention

The present invention relates to a sizing composition that, when applied to paper

substrate, creates a substrate, preferably suitable for inkjet printing, having increased

print density, print sharpness, low HST, and/or image dry time, the substrate

preferably having high brightness and reduced color-to-color bleed as well. In

addition, the present invention relates to a method of reducing the HST of a paper

substate by applying the sizing composition to at least one surface thereof. Further, the

application relates to methods of making and using the sizing composition, as well as

methods of making and using the paper containing the sizing composition.

Background of the Invention

InkJet recording systems using aqueous inks are now well known. These

systems usually generate almost no noise and can easily perform multicolor

recordings for business, home and commercial printing applications. Recording sheets for ink jet recordings are known. See for example U.S. Pat. Nos. 5,270,103;

5,657,064; 5,760,809; 5,729,266; 4,792,487; 5,405,678; 4,636,409; 4,481,244;

4,496,629; 4,517,244; 5,190,805; 5,320,902; 4,425,405; 4,503,118; 5,163,973;

4,425,405; 5,013,603; 5,397,619; 4,478,910; 5,429,860; 5,457,486; 5,537,137;

5,314,747; 5,474,843; 4,908,240; 5,320,902; 4,740,420; 4,576,867; 4,446,174;

4,830,911; 4,554,181; 6,764,726 and 4,877,680, which are hereby incorporated, in

their entirety, herein by reference.

However, conventional paper substrates, such as those above remain poor in

balancing good print density, HST, color-to-color bleed, print sharpness, and/or

image dry time. Accordingly, there is a need to provide such high-performance

functionality to paper substrates useful in inkjet printing, especially those substrates

preferably having high brightness.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1: A first schematic cross section of just one exemplified embodiment of the

paper substrate that is included in the paper substrate of the present invention. Figure 2: A second schematic cross section of just one exemplified embodiment of the

paper substrate that is included in the paper substrate of the present invention.

Figure 3: A third schematic cross section of just one exemplified embodiment of the

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have discovered a sizing composition that, when

applied to paper or paperboard substrates, improves the substrate's print density,

color-to-color bleed, print sharpness, and/or image dry time. Further, the paper

substrate preferably has a high brightness.

The sizing composition may contain a pigment. Examples of pigments are

clay, calcium carbonate, calcium sulfate hemihydrate, and calcium sulfate

dehydrate, calcium carbonate, preferably precipitated calcium carbonate, in any

form including ground calcium carbonate and silica-treated calcium carbonate.

When the pigment is a calcium carbonate, it may be in any form. Examples include

ground calcium carbonate and/or precipitated calcium carbonate. Commercially available products that are preferred are those offered as Jetcoat 30 from Specialty

Minerals Inc., Jetcoat MD 1093 from Specialty Minerals Inc., XC3310-1 from

Omya Inc, and OmyaJet B5260, C4440 and 6606 from Omya Inc.

The pigment may have any surface area. Those pigments having a high

surface area are included, including those having a surface area of greater than 20

square meters/gram, preferably greater than 30 square meters/gram, more preferably

greater than 50 square meters/gram, most preferably greater than 100 square

meters/gram. This range includes greater than or equal to 1, 5, 10, 15, 20, 25, 30,

35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 100 square meters/gram, including any

and all ranges and subranges contained therein.

The sizing composition may contain a pigment at any amount. The

composition may include from 0 to 99wt% based upon the total weight of the solids

in the composition, preferably at least 15wt%, more preferably at least 30wt%, most

preferably at least 45wt% pigment based upon the total weight of the solids in the

composition. This range may include 0, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55,

60, 65, 70, 75, 80, 85, 90, 100wt% of pigment based upon the total weight of the

solids in the composition, including any and all ranges and subranges contained therein. The most preferred amount being about 52 wt% pigment based upon the

total weight of the solids in the composition.

The sizing composition may contain a binder. Examples of binders include,

but are not limited to, polyvinyl alcohol, Amres (a Kymene type), Bayer Parez,

polychloride emulsion, modified starch such as hydroxyethyl starch, starch or

derivatives thereof including cationic and oxidized forms and from corn and/or

potato for example, poly aery lamide, modified polyacrylamide, polyol, polyol

carbonyl adduct, ethanedial/polyol condensate, polyamide, epichlorohydrin,

glyoxal, glyoxal urea, ethanedial, aliphatic polyisocyanate, isocyanate, 1 ,6

hexamethylene diisocyanate, diisocyanate, polyisocyanate, polyester, polyester

resin, polyacrylate, polyacrylate resin, acrylate, and methacrylate. While any

combination of binders may be used, one embodiment includes a sizing composition

containing starch or modifications thereof combined with polyvinyl alcohol as

multi-component binder.

When there is a multicomponent binder system, one embodiment relates to a

system including at least starch and deriviates thereof with polyvinyl alcohol. In this

embodiment, the ratio of starch/PVOH solids based on the total weight of the solids

in the sizing composition may be any ratio so long as both are present in the composition. The sizing composition may contain a ratio of starcli/PVOH wt%

solids based on the total weight of the solids in the composition of from 99/1 to

1/99, preferably from 50/1 to 1/5, more preferably at most 10/1 to 1 :2, most

preferably at most 8/1 to 1/1. This range includes 99/1, 50/1, 25/1, 15/1., 10/1, 9/1,

8/1, 7/1, 6/1, 5/1, 4/1, 3/1, 2/1, 1/1, 2/3, 1/2, 1/10, 1/25, 1/50, 1/99, including any

and all ranges and subranges therein. The most preferred starch/PVOH ratio being

6/1.

When polyvinyl alcohol is utilized in the sizing solution and/or in the paper,

polyvinyl alcohol (PVOH) is produced by hydrolyzing polyvinyl acetate (PVA).

The acetate groups are replaced with alcohol groups and the higher the hydrolysis

indicates that more acetate groups have been replaced. Lower hydrolysis/molecular

weight PVOH are less viscous and more water soluble. The PVOH may have a

%hydrolysis ranging from 100% to 75%. The % hydrolysis may be 75, 76, 78, 80,

82, 84, 85, 86, 88, 90, 92, 94, 95, 96, 98, and 100%hdrolysis, %, including any and

all ranges and subranges therein. Preferably, the % hydrolysis of the PVOH is

greater than 90%.

The sizing composition may contain a binder at any amount. The sizing

composition may contain at least one binder from 0 to 99wt%, preferably at least 10wt%, more preferably at least 20wt%, most preferably at least 30 wt% based on

the total weight of the solids in the composition. This range may include 0, 1, 5, 10,

15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 100wt% based on the

total weight of the solids in the composition, including any and all ranges and

subranges contained therein. The most preferred being about 37wt% binder based

on the total weight of the solids in the composition.

In one embodiment, when the sizing composition contains a binder and a

pigment, the weight ratio of the binder/pigment may be any ratio. The binder

pigment weight ratio may be from 99/1 to 1/99, preferably from 50/1 to 1/10, more

preferably from 25/1 to 1/5, most preferably from 10/1 to 1/3. This range includes

99/1, 50/1, 25/1, 10/1, 5/1, 2/1, 1/1, 1/2, 2/3, 1/3, 1/4, 1/5, 10/1, 25/1, 50/1, and

99/1, including any and all ranges and subranges therein. The most preferred

binder/pigment weight ratio is 7/10.

The sizing composition may contain at least one nitrogen containing organic

species. Exemplified nitrogen containing organic species are compounds,

oligomers and polymers are those containing one or more quaternary ammonium

functional groups. Such functional groups may vary widely and include substituted and unsubstituted amines, imines, amides, urethanes, quaternary ammonium groups,

dicyandiamides and the like. Illustrative of such materials are polyamines,

polyethyleneimines, polymers and copolymers of diallyldimethyl ammonium

chloride (DADMAC), copolymers of vinyl pyrrolidone (VP) with quaternized

diethylaminoethylmethacrylate (DEAMEMA), polyamides, cationic polyurethane

latex, cationic polyvinyl alcohol, polyalkylamines dicyandiamid copolymers, amine

glycigyl addition polymers, poly[oxyethylene (dimethyliminio) ethylene

(dimethyliminio) ethylene] dichlorides. Examples of nitrogen containing species

include those mentioned in US Patent Number 6,764,726, which is hereby

incorporated, in its entirety, herein by reference. The most preferred nitrogen

containing species are polymers and copolymers of diallyldimethyl ammonium

chloride (DADMAC).

The sizing composition may contain at least one nitrogen containing organic

species at any amount. The sizing composition may contain the nitrogen containing

species at an amount ranging from 0 to 99wt%, preferably from 0.5 to 50wt%, more

preferably from 1 to 20 wt %, most preferably from 2 to 10 wt% based on the total

weight of the solids in the composition. This range may include 0, 0.5, 1, 2, 3, 4, 5,

6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 100wt%

based on the total weight of the solids in the composition, including any and all ranges and subranges contained therein. In a preferred embodiment, the

composition contains about 8wt% of the nitrogen containing species based on the

total weight of the solids in the composition.

The sizing composition may contain at least one inorganic salt. Suitable

inorganic salts may be monovalent and/or divalent and/or trivalent and may contain

any level of hydration complexes thereof. Exemplified inorganic salts are those

from Groups 1 , 2 and 13 from the Periodic Table of Elements and hydrated

complexes thereof, including monohydrates, dihydrates, trihydrates, tetrahydrates,

etc. The cationic metal may be sodium, calcium, magnesium, and aluminum

preferably. The anionic counterion to the cationic metal of the inorganic salt may be

any halogen such as chloride, boride, fluoride, etc and/or hydroxyl group(s). The

most preferred inorganic salt being sodium chloride.

The sizing composition may contain at least one inorganic salt at any amount.

The sizing composition may contain from 0 to 99wt%, preferably from 0.25 to 25

wt%, more preferably from 0.5 to 5, most preferably from 1 to 3 wt% of the

inorganic salt based on the total weight of the solids in the composition. This range

may include O₅ 0.25, 0.5, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,

70, 75, 80, 85, 90, 100wt% based on the total weight of the solids in the composition, including any and all ranges and subranges contained therein. In a

preferred embodiment, the sizing composition contains about 2.5wt% of the

inorganic salt based on the total weight of the solids in the composition.

The sizing composition may contain at least one optical brightening agent

(OBA). Suitable OBAs may be those mentioned in USSN 60/654,712 filed

February 19, 2005, and USP 6,890,454, which are hereby incorporated, in their

entirety, herein by reference. The OBAs may be commercially available from

Clariant. Further, the OBA may be either cationic and/or anionic. Example OBA is

that commercially available Leucophore BCW and Leucophore FTS from Clariant.

In one embodiment, the OBA contained in the sizing composition is cationic.

The sizing composition may contain any amount of at least one anionic OBA.

The sizing composition may contain anionic OBA at an amount from O to 99wt%,

preferably from 5 to 75wt%, more preferably from 10 to 50 wt%, most preferably

from 20 to 40wt% based on the total weight of the solids in the composition. This

range may include 0, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80,

85, 90, 99wt% anionic OBA based on the total weight of the solids in the

composition, including any and all ranges and subranges contained therein. In a preferred embodiment, the sizing composition contains about 35wt% of anionic

OBA based on the total weight of the solids in the composition.

The sizing composition may contain any amount of at least one cationic

OBA. The sizing composition may contain cationic OBA at an amount from O to

99wt%, preferably from 0.5 to 25wt%, more preferably from 1 to 20 wt%, most

preferably from 5 to 15wt% based on the total weight of the solids in the

60, 65, 70, 75, 80, 85, 90, 99wt% anionic OBA based on the total weight of the

solids in the composition, including any and all ranges and subranges contained

therein. In a preferred embodiment, the sizing composition contains about 8wt% of

cationic OBA based on the total weight of the solids in the composition.

The present invention also relates to a paper substrate containing any of the

sizing compositions described above.

The paper substrate contains a web of cellulose fibers. The source of the

fibers may be from any fibrous plant. The paper substrate of the present invention

may contain recycled fibers and/or virgin fibers. Recycled fibers differ from virgin fibers in that the fibers have gone through the drying process at least once.

The paper substrate of the present invention may contain from 1 to 99 wt%,

preferably from 5 to 95 wt%, most preferably from 60 to 80 wt% of cellulose fibers

based upon the total weight of the substrate, including 1, 5, 10, 15, 20, 25, 30, 35,

40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 99 wt%, and including any and all

ranges and subranges therein.

While the fiber source may be any, the preferable sources of the cellulose

fibers are from softwood and/or hardwood. The paper substrate of the present

invention may contain from 1 to 100 wt%, preferably from 5 to 95 wt%, cellulose

fibers originating from softwood species based upon the total amount of cellulose

fibers in the paper substrate. This range includes 1, 2, 5, 10, 15, 20, 25, 30, 35, 40,

45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 100wt%, including any and all ranges

and subranges therein, based upon the total amount of cellulose fibers in the paper

substrate.

The paper substrate of the present invention may contain from 1 to 100 wt%,

preferably from 5 to 95 wt%, cellulose fibers originating from hardwood species

based upon the total amount of cellulose fibers in the paper substrate. This range includes 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95,

and 100wt%, including any and all ranges and subranges therein, based upon the

total amount of cellulose fibers in the paper substrate.

When the paper substrate contains both hardwood and softwood fibers, it is

preferable that the hardwood/softwood ratio be from 0.001 to 1000. This range may

include 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 15, 20, 25, 30,

35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 200, 300, 400, 500, 600, 700,

800, 900, and 1000 including any and all ranges and subranges therein and well as

any ranges and subranges therein the inverse of such ratios.

Further, the softwood and/or hardwood fibers contained by the paper

substrate of the present invention may be modified by physical and/or chemical

means. Examples of physical means include, but is not limited to, electromagnetic

and mechanical means. Means for electrical modification include, but are not

limited to, means involving contacting the fibers with an electromagnetic energy

source such as light and/or electrical current. Means for mechanical modification

include, but are not limited to, means involving contacting an inanimate object with

the fibers. Examples of such inanimate objects include those with sharp and/or dull

edges. Such means also involve, for example, cutting, kneading, pounding, impaling, etc means.

Examples of chemical means include, but is not limited to, conventional

chemical fiber modification means including crosslinking and precipitation of

complexes thereon. Examples of such modification of fibers may be, but is not

limited to, those found in the following patents 6,592,717, 6,592,712, 6,582,557,

6,579,415, 6,579,414, 6,506,282, 6,471,824, 6,361,651, 6,146,494, Hl, 704,

5,731,080, 5,698,688, 5,698,074, 5,667,637, 5,662,773, 5,531,728, 5,443,899,

5,360,420, 5,266,250, 5,209,953, 5,160,789, 5,049,235, 4,986,882, 4,496,427,

4,431,481, 4,174,417, 4,166,894, 4,075,136, and 4,022,965, which are hereby

incorporated, in their entirety, herein by reference. Further modification of fibers is

found in United States Patent Applications having Application Number 60/654,712

filed February 19, 2005; 11/358,543 filed February 21, 2006; 11/445,809 filed June

2, 2006; and 11/446,421 filed June 2, 2006, which may include the addition of

optical brighteners (i.e. OBAs) as discussed therein, which are hereby incorporated,

in their entirety, herein by reference.

One example of a recycled fiber is a "fine". Sources of "fines" may be found

in SaveAll fibers, recirculated streams, reject streams, waste fiber streams. The

amount of "fines" present in the paper substrate can be modified by tailoring the rate at which such streams are added to the paper making process.

The paper substate preferably contains a combination of hardwood fibers,

softwood fibers and "fines" fibers. "Fines" fibers are, as discussed above,

recirculated and are any length. Fines may typically be not more that 100 μm in

length on average, preferably not more than 90 μm, more preferably not more than

80 μm in length, and most preferably not more than 75 μm in length. The length of

the fines are preferably not more than 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60,

65, 70, 75, 80, 85, 90, 95, and 100 μm in length, including any and all ranges and

subranges therein.

The paper substrate may contain fines at any amount. The paper substrate

may contain from 0.01 to 100 wt% fines, preferably from 0.01 to 50wt%, most

preferably from 0.01 to 15wt% based upon the total weight of the fibers contained

by the paper substrate. The paper substrate contains not more than 0.01, 0.05, 0.1 ,

0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70,

75, 80, 85, 90, 95 and 100wt% fines based upon the total weight of the fibers

contained by the paper substrate, including any and all ranges and subranges

therein. The paper substrate may also contain an internal sizing and/or external sizing

composition. The internal sizing composition may be applied to the fibers during

papermaking at the wet end, while the external sizing composition may be applied

to the fibers via a size press and/or coater. The above mentioned sizing

compositions of the present invention may be the internal and/or external sizing

composition contained by the paper substrate of the present invention.

Figures 1-3 demonstrate different embodiments of the paper substrate 1 in the

paper substrate of the present invention. Figure 1 demonstrates a paper substrate 1

that has a web of cellulose fibers 3 and a sizing composition 2 where the sizing

composition 2 has minimal interpenetration of the web of cellulose fibers 3. Such

an embodiment may be made, for example, when a sizing composition is coated

onto a web of cellulose fibers.

Figure 2 demonstrates a paper substrate 1 that has a web of cellulose fibers 3

and a sizing composition 2 where the sizing composition 2 interpenetrates the web

of cellulose fibers 3. The interpenetration layer 4 of the paper substrate 1 defines a

region in which at least the sizing solution penetrates into and is among the

cellulose fibers. The interpenetration layer may be from 1 to 99% of the entire cross

section of at least a portion of the paper substrate, including I₅ 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 99% of the paper substrate,

including any and all ranges and subranges therein. Such an embodiment may be

made, for example, when a sizing composition is added to the cellulose fibers prior

to a coating method and may be combined with a subsequent coating method if

required. Addition points may be at the size press, for example.

Figure 3 demonstrates a paper substrate 1 that has a web of cellulose fibers 3

and a sizing solution 2 where the sizing composition 2 is approximately evenly

distributed throughout the web of cellulose fibers 3. Such an embodiment may be

to a coating method and may be combined with a subsequent coating method if

required. Exemplified addition points may be at the wet end of the paper making

process, the thin stock, and the thick stock.

The paper substrate may be made by contacting any component of the sizing

solution with the cellulose fibers consecutively and/or simultaneously. Still further,

the contacting may occur at acceptable concentration levels that provide the paper

substrate of the present invention to contain any of the above-mentioned amounts of

cellulose and components of the sizing solution. The contacting may occur anytime

in the papermaking process including, but not limited to the thick stock, thin stock, head box, and coater with the preferred addition point being at the thin stock.

Further addition points include machine chest, stuff box, and suction of the fan

pump. Preferably, the components of the sizing solution are preformulated either

together and/or in combination within a single and/or separate coating layer(s) and

coated onto the fibrous web via a size press and/or coater.

The paper or paperboard of this invention can be prepared using known

conventional techniques. Methods and apparatuses for forming and making and

applying a coating formulation to a paper substrate are well known in the paper and

paperboard art. See for example, G.A. Smook referenced above and references cited

therein all of which is hereby incorporated by reference. All such known methods

can be used in the practice of this invention and will not be described in detail.

The paper substrate may contain the sizing composition at any amount. The

paper substrate may contain the sizing composition at an amount ranging from 70 to

300 lbs/ton of paper, preferably from 80 to 2501bs/ton of paper, more preferably

from 100 to 200 lbs/ton of paper, most preferably from 125 to 175 lbs/ton of paper.

This range includes, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190,

200, 210, 220, 230, 240, 250, 260, 270 280, 290, and 300 lbs/ton of paper, including

any and all ranges and subranges therein. In a preferred embodiment the paper substrate contains a size press applied sizing composition at an amount of 150

lbs/ton of paper substrate.

Given the above mentioned preferred amounts of sizing composition

contained in the substrate of the present invention, combined with the above-

mentioned amounts of pigment, binder, nitrogen containing compound, and

inorganic salt; the amounts of each of the pigment, binder, nitrogen containing

compound, inorganic salt that are contained in the paper may be easily calculated.

For example, if 50wt% of pigment is present in the sizing solution based upon the

total weight of solids in the composition, and the paper substrate contains 1501bs of

the sizing composition/ton, then the paper substrate contains 50% x 1501bs/ton of

paper= 75 lbs pigment/ton of paper, which is 75 lbs/20001bs x 100= 3.75wt%

pigment based upon the total weight of the paper substrate.

The paper substrate contains any amount of at least one pigment. The paper

substrate may contain from 0.5 wt % to 10 wt%, preferably from 1 to 8wt%, more

preferably from 1.5 to 6wt%, most preferably from 2 to 5wt% of pigment based

upon the total weight of the substrate. This range includes 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 and 10wt% of pigment based upon the total

weight of the substrate, including any and all ranges and subranges therein.

The paper substrate contains any amount of at least one binder. The paper

substrate may contain from 0.1 wt % to 7 wt%, preferably from .2 to 5 wt%, more

preferably from 0.3 to 3wt%, most preferably from 1 to 3 wt% of binder based upon

the total weight of the substrate. This range includes 0.1, 0.2, 0.3, 0.4, 0.5, 1, 1.5, 2,

2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, and 7.5wt% of binder based upon the total weight

of the substrate, including any and all ranges and subranges therein.

The paper substrate contains any amount of at least one nitrogen containing

compound. The paper substrate may contain from 0.01 wt % to 5 wt%, preferably

from 0.05 to 2wt%, more preferably from 0.1 to 1.5 wt%, most preferably from 0.25

to 1 wt% of nitrogen containing compound based upon the total weight of the

substrate. This range includes 0.01, 0.02, 0.03, 0.05, 0.07, 0.1, 0.2, 0.3, 0.4, 0.5,

0.6, 0.7, 0.8, 0.9, 1 , 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, and 3wt% of nitrogen

containing compound based upon the total weight of the substrate, including any

and all ranges and subranges therein. The paper substrate contains any amount of at least inorganic salt. The paper

substrate may contain from 0.001 wt % to 3 wt%, preferably from 0.01 to 2.5wt%,

more preferably from 0.02 to 1 wt%₅ most preferably from 0.05 to 0.5 wt% of

inorganic salt based upon the total weight of the substrate. This range includes

0.001, 0.002, 0.005, 0.007, 0.01, 0.02, 0.03, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2,

0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, and 3wt%

of inorganic salt based upon the total weight of the substrate, including any and all

ranges and subranges therein.

The paper substrate may contain any amount of OBA. The OBA may be

cationic and/or anionic. The OBA may be supplied by the sizing composition as

mentioned above and/or within the substrate itself. For example, the OBA may be

premixed with the fibers at the wet end of the papermaking and even before the

headbox. Preferred examples of using OBA:fϊber mixes is found in United States

Patent Applications having Application Number 60/654,712 filed February 19,

2005; 11/358,543 filed February 21, 2006; 11/445,809 filed June 2, 2006; and

11/446,421 filed June 2, 2006, which are hereby incorporated, in their entirety,

herein by reference.

In one embodiment of the present invention, the paper substrate contains internal OBA and externally applied OBA. The internal OBA may be cationic or

anionic, but is preferably anionic. The externally applied OBA may be cationic or

anionic, but is preferably cationic. The externally applied OBA is preferably

applied as a member of the sizing composition at the size press as mentioned above

in the above preferred amounts of OBA. However, external OBA may also be

applied at the coating section.

The paper substrate of the present invention may have any amount of OBA.

In one embodiment, the OBA is present in as sufficient amount so that the paper has

at least 80% GE brightness. The GE brightness is preferably at least 80, 85, 90, 91,

92, 93, 94, 95, 96, 97, 98, 99, and 100%, including any and all ranges and subranges

contained therein.

Further, the paper may have a suitable amount of OBA and other additives

(such as dyes) so that the paper preferably has a CIE whiteness of at least 130. The

CIE whiteness may be at least 130, 135, 140, 145, 150, 155, 160, 65, 170, 175, 180,

185, 190, 195, and 200 CIE whiteness points, including any and all ranges and

subranges therein. In one embodiment, the substrate contains an effective amount of OBA. An

effective amount of OBA is such that the GE brightness is at least 90, preferably at

least 92, more preferably at least 94 and most preferably at least 95% brightness.

The OBA may be a mixture of the above-mentioned internal and externally applied

OBA, whether cationic and/or anionic so long as it is an effective amount.

The density, basis weight and caliper of the web of this invention may vary

widely and conventional basis weights, densities and calipers may be employed

depending on the paper-based product formed from the web. Paper or paperboard of

invention preferably have a final caliper, after calendering of the paper, and any

nipping or pressing such as may be associated with subsequent coating of from

about 1 mils to about 35 mils although the caliper can be outside of this range if

desired. More preferably the caliper is from about 4 mils to about 20 mils, and most

preferably from about 7 mils to about 17 mils. The caliper of the paper substrate

with or without any coating may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17,

20, 22, 25, 27, 30, 32, and 35, including any and all ranges and subranges therein.

Paper substrates of the invention preferably exhibit basis weights of from

about 10 lb/3000ft ² to about 500 lb/3000ft ², although web basis weight can be

outside of this range if desired. More preferably the basis weight is from about 301b/3000ft ² to about 200 lb/3000ft ², and most preferably from about 35 lb/3000ft

² to about 150 lb/3000ft ². The basis weight may be 10, 12, 15, 17, 20, 22, 25, 30,

32, 35, 37, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140,

150, 160, 170, 180, 190, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 500

lb/3000ft ², including any and all ranges and subranges therein.

The final density of the papers may be calculated by any of the above-

mentioned basis weights divided by any of the above-mentioned calipers, including

any and all ranges and subranges therein. Preferably, the final density of the papers,

that is, the basis weight divided by the caliper, is preferably from about 6 lb/3000ft

²/mil to about 14 lb/3000ft ²/mil although web densities can be outside of this range

if desired. More preferably the web density is from about 7 lb/3000ft ²/mil to about

13 lb/3000ft ²/mil and most preferably from about 9 lb/3000ft ²/mil to about 12

lb/3000ft ²ImU.

The web may also include other conventional additives such as, for example,

starch, expandable microspheres, mineral fillers, bulking agents, sizing agents,

retention aids, and strengthening polymers. Among the fillers that may be used are

organic and inorganic pigments such as, by way of example, polymeric particles

such as polystyrene latexes and polymethylmethacrylate, and minerals such as calcium carbonate, kaolin, and talc. Other conventional additives include, but are

not restricted to, wet strength resins, internal sizes, dry strength resins, alum, fillers,

pigments and dyes. Internal sizing helps prevent the surface size from soaking into

the sheet, thus allowing it to remain on the surface where it has maximum

effectiveness. The internal sizing agents encompass any of those commonly used at

the wet end of a paper machine. These include rosin sizes, ketene dimers and

multimers, and alkenylsuccinic anhydrides. The internal sizes are generally used at

levels of from about 0.00 wt. % to about 0.25 wt. % based on the weight of the dry

paper sheet. Methods and materials utilized for internal sizing with rosin are

discussed by E. Strazdins in The Sizing of Paper, Second Edition, edited by W. F.

Reynolds, Tappi Press, 1989, pages 1-33. Suitable ketene dimers for internal sizing

are disclosed in U.S. Pat. No. 4,279,794, which is incorporated by reference in its

entirety, and in United Kingdom Patent Nos. 786,543; 903,416; 1,373,788 and

1,533, 434, and in European Patent Application Publication No. 0666368 A3.

Ketene dimers are commercially available, as Aquapel.RTM. and Precis.RTM.

sizing agents from Hercules Incorporated, Wilmington, Del. Ketene multimers for

use in internal sizes are described in: European Patent Application Publication No.

0629741A1 , corresponding to U.S. patent application Ser. No. 08/254,813, filed

Jun. 6, 1994; European Patent Application Publication No. 0666368A3,

corresponding to U.S. patent application Ser. No. 08/192,570, filed Feb. 7, 1994; and U.S. patent application Ser. No. 08/601,113, filed Feb. 16, 1996.

Alkenylsuccinic anhydrides for internal sizing are disclosed in U. S. Pat. No.

4,040,900, which in incorporated herein by reference in its entirety, and by C. E.

Farley and R. B. Wasser in The Sizing of Paper, Second Edition, edited by W. F.

Reynolds, Tappi Press, 1989, pages 51-62. A variety of alkenylsuccinic anhydrides

are commercially available from Albemarle Corporation, Baton Rouge, La.

The paper substrate may be made by contacting further optional substances

with the cellulose fibers as well. The contacting of the optional substances and the

cellulose fibers may occur anytime in the papermaking process including, but not

limited to the thick stock, thin stock, head box, size press, water box, and coater.

pump. The cellulose fibers, components of the sizing composition, and/or optional

components may be contacted serially, consecutively, and/or simultaneously in any

combination with each other. The cellulose fibers components of the sizing

composition may be pre-mixed in any combination before addition to or during the

paper-making process.

The paper substrate may be pressed in a press section containing one or more

nips. However, any pressing means commonly known in the art of papermaking may be utilized. The nips may be, but is not limited to, single felted, double felted,

roll, and extended nip in the presses. However, any nip commonly known in the art

of papermaking may be utilized.

The paper substrate may be dried in a drying section. Any drying means

commonly known in the art of papermaking may be utilized. The drying section

may include and contain a drying can, cylinder drying, Condebelt drying, IR, or

other drying means and mechanisms known in the art. The paper substrate may be

dried so as to contain any selected amount of water. Preferably, the substrate is

dried to contain less than or equal to 10% water.

The paper substrate may be passed through a size press, where any sizing

means commonly known in the art of papermaking is acceptable. The size press,

for example, may be a puddle mode size press (e.g. inclined, vertical, horizontal) or

metered size press ( e.g. blade metered, rod metered). At the size press, sizing

agents such as binders may be contacted with the substrate. Optionally these same

sizing agents may be added at the wet end of the papermaking process as needed.

After sizing, the paper substrate may or may not be dried again according to the

above-mentioned exemplified means and other commonly known drying means in

the art of papermaking. The paper substrate may be dried so as to contain any selected amount of water. Preferably, the substrate is dried to contain less than or

equal to 10% water. Preferably, the sizing apparatus is a puddle size press.

The paper substrate may be calendered by any commonly known calendaring

means in the art of papermaking. More specifically, one could utilize, for example,

wet stack calendering, dry stack calendering, steel nip calendaring, hot soft

calendaring or extended nip calendering, etc. While not wishing to be bound by

theory, it is thought that the presence of the expandable microspheres and/or

composition and/or particle of the present invention may reduce and alleviate

requirements for harsh calendaring means and environments for certain paper

substrates, dependent on the intended use thereof.

The paper substrate may be microfmished according to any microfinishing

means commonly known in the art of papermaking. Microfinishing is a means

involving frictional processes to finish surfaces of the paper substrate. The paper

substrate may be microfmished with or without a calendering means applied thereto

consecutively and/or simultaneously. Examples of microfinishing means can be

found in United States Published Patent Application 20040123966 and references

cited therein, as well as USSN 60/810181 filed on June 2, 2006, which are all

hereby, in their entirety, herein incorporated by reference. The Hercules Sizing Test Value ("HST") of the substrate is selected to

provide the desired waterfastness characteristics. The HST is measured using the

procedure of TAPPI 530 pm-89. The paper substrate of the present invention may

have any HST. In some embodiments, the HST may be as much as 400, 300, 200,

and 100 seconds. Further, the HST may be is as low as 0.1, 1, 5 and 10 seconds.

However, in a preferred embodiment of this invention, the HST is less than 10

seconds, preferably, less than 5 seconds, more preferably less than 3 seconds HST,

most preferably less than about 1 second. The HST may be 0.001, 0.01, 0.05, 0.1 ,

0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 and 10 seconds,

including any and all ranges and subranges therein. As it is well known to those of

ordinary skill in the art, the HST will vary directly with the basic weight of the

substrate and other factors known to those of ordinary skill in the art. Based upon

the foregoing information, one of ordinary skill in the art can use conventional

techniques and procedures to calculate, determine and/or estimate a particular HST

for the substrate used to provide the desired image waterfastness characteristics.

The paper substrate of the present invention may have any black optical

density as measured by TAPPI METHOD T 1213 sρ-03. The black optical density

may be from 0.5 to 2.0, more preferably from 1.0 to 1.5. The black optical density may be 0.5, 0..6, 0.7, 0.8, 0.9, 1.0, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12,

1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.2, 1.3, 1.4, and 1.5, including any and all

ranges and subranges therein.

From density, one can naturally calculate waterfastness using the following

equation:

(OD of soaked ink area/OD of unsoaked ink area) * 100 = % Waterfastness.

The paper substrate of the present invention may have any waterfastness. The paper

substrate may have a waterfastness of at least 90%, preferably at least 95%, more

preferably greater than 98%, most preferably greater than 100%, including any and

all ranges and subranges therein.

In one embodiment of the present invention, the paper substrate may contain

an effective amount of pigment and binder. An effective amount of pigment and

binder is that which bestows on the paper a black optical density that is at least 1.0,

preferably from 1 to 2, more preferably from 1 to 1.5 and most preferably from 1.1

to 1.3, including any and all ranges and subranges therein. The present invention relates to a method of decreasing the HST of a paper

substrate. Preferably, the above-mentioned sizing composition is contacted with a

substrate having a first HST and containing a web of cellulose fibers and optional

substances mentioned above at a size press or coating section so as to prepare a

paper substrate having a second HST that is less than the first HST and containing

the sizing composition, the web of cellulose fibers, and optional substance. While

the second HST is less than the first HST, the present invention preferably reduces

the first HST by at least 10%, more preferably by at least 25%, most preferably by

at least 50%. This reduction range may be at least 10, 15, 20, 25, 30, 35, 40, 45, 50,

60, 75, 80, 95 and 99% of the first HST, including any and all ranges and subranges

therein.

The present invention is explained in more detail with the aid of the

following embodiment example which is not intended to limit the scope of the

present invention in any manner.

EXAMPLES

Example J-

The following size press formulations were prepared for treating the un-surface sized base paper

The p_igmented size press formulations were applied to an unsurface sized 90 gsm base paper using a rod meteπng size press The target coat weight or pick up is 6 gsm Calendering was done on a steel -to- steel lab calender at room temperature with a nip _pressure of 90 psi The smoothness target is 125 Sheffield smoothness

J _he paper samples from example ] were evaluated forpnnt performance on an Kodak Versamark 5000 digital press ExcelJent pπnt quality were obtained The print density the tnal sam les rovided m example ] are listed m the following table

Example 2:

Paper substrates having a basis weight of 24 lb/1300 square feet were made and a

sizing composition was applied thereto both surfaces of the paper substrate at size

press. The sizing compositions applied to the paper substrate are those according to

the following Table 2.

Table 2

Gen Floe F71 100 (General Chemicals) and Cartafix VXZ (Clariant) are both of the

chemical nature of poly(dadmac) and are nitrogen-containing species.

Amres, a kymene wet-strength resin from Kamira is also nitrogen-containing

species.

Mowiol 28-99 (Clariant) is a version of PVOH, which is 99% hydrolyzed and is of

high molecular weight.

Starch and PVOH were cooked separately and diluted to a solids level of about

15%. Each of the formulation was prepared in accordance with the recipe as

tabulated above and was thoroughly mixed together.

An overall %solids was first arrived at greater than the targeted 15%, because the

rest of the ingredients all have a solids level above 15%.

For each of the formulations, the actual initial %solids was measured and then

diluted, as close as possible, to 15%. Each of the formulations was sent to the 14'

pilot size press, which was pre-configured to C2S puddle operation.

The paper after size press was dried to 4.2 to 5.0% moisture.

The subscript [a] denotes average, which means each of the numbers was averaged

from 4 or even more readings.

The two numbers before and after the slash sign represent readings from the two

sides of the paper, respectively.

InkJet print densities are measured by means of optical densities with an X-

rite densitometer. The density according to TAPPI METHOD T 1213 sp-03 is the

optical -negative logarithm to base 10 of transmittance for transparent material or the reflectance for an opaque material and has the equation Optical Density = log 10

1/R, where R = Reflectance. The following densitometer was used: X-Rite

Densitometer, manufactured by X-Rite Inc. Density is a function of the percentage

of light reflected. From this density procedure, one can easily measure

Waterfastness and % bleed as well using the following equations:

Calculation for % Waterfastness:

(OD of soaked ink area/OD of unsoaked ink area) * 100 = % Waterfastness

Calculation for % Bleed:

[(OD near soaked ink area - OD of paper)/OD unsoaked ink area] * 100 = % Bleed.

Numerous modifications and variations on the present invention are possible

in light of the above teachings. It is, therefore, to be understood that within the

scope of the accompanying claims, the invention may be practiced otherwise than as

specifically described herein.

As used throughout, ranges are used as a short hand for describing each and

every value that is within the range, including all subranges therein.

All of the references, as well as their cited references, cited herein are hereby

incorporated by reference with respect to relative portions related to the subject matter

of the present invention and all of its embodiments

Claims

WHAT IS CLAIMED IS:

1) A sizing composition, comprising

at least one pigment

at least one binder;

at least one nitrogen containing organic species; and

at least one inorganic salt.

2) The sizing composition according to Claim 1 , comprising

at least one pigment

at least two binders;

at least one nitrogen containing organic species; and

at least one inorganic salt.

3.) The sizing composition according to Claim 2, wherein the at least two

binders are polyvinyl alcohol and starch.

4.) The sizing composition according to Claim 3, wherein the polyvinyl

alcohol and starch are present at a starch/polyvinyl alcohol weight ratio of

from δ/l to l/1.

5.) The sizing composition according to Claim 4, wherein the total binder is

present at an amount of at least 20wt%, based upon the total weight of the

solids in of the composition.

6.) The sizing composition according to Claim 4, further comprising from 20

to 40wt% based on the total weight of the solids in the composition of an

optical brightening agent.

7.) The sizing composition according to Claim 4, further comprising an

optical brightening agent.

8.) The sizing composition according to Claim 8, wherein the optical

brightening agent is cationic.

9.) The sizing composition according to Claim 1, comprising

at least one pigment at an amount of at least 30wt% based upon the

total weight of the solids in of the composition

at least one binder at an amount of at least 20wt% based upon the total

weight of the solids in of the composition; at least one nitrogen containing organic species at an amount ranging

from 1 to 20wt% based upon the total weight of the solids in of the

composition; and

at least one inorganic salt at an amount ranging from 0.5 to 5wt%

based upon the total weight of the solids in of the composition.

10.) The sizing composition according to Claim 9, comprising

at least two binders wherein the at least two binders are starch and

polyvinyl alcohol at a weight ratio of from 8/1 to 1/1 starch/ polyvinyl

alcohol; and

an optical brightener.

11.) A paper substrate, comprising the sizing composition according to

Claim 1.

12.) The paper substate according to Claim 11, wherein the substrate has a

print density of at least 1.0 and an HST of not more than 10 seconds.

13.) The paper substrate according to Claim 12, wherein the substrate has a waterfastness of at least 95%.

14.) A paper substrate comprising the sizing composition according to

Claim 4.

15.) The paper substate according to Claim 14, wherein the substrate has a

print density of at least 1.0 and an HST of not more than 10 seconds.

16.) The paper substrate according to Claim 15, wherein the substrate has a

waterfastness of at least 95%.

17.) A paper substrate comprising the sizing composition according to

Claim 9.

18.) The paper substate according to Claim 17, wherein the substrate has a

print density of at least 1.0 and an HST of not more than 10 seconds.

19.) The paper substrate according to Claim 18, wherein the substrate has a

waterfastness of at least 95%.

0.) A paper substrate, comprising the sizing composition according to

Claim 10 and having

a print density of at least 1.0;

an HST of not more than 10 seconds; and

a waterfastness of at least 95%.