WO2011160049A1

WO2011160049A1 - Reduced solids adhesive composition and related methods

Info

Publication number: WO2011160049A1
Application number: PCT/US2011/040927
Authority: WO
Inventors: Leonard Jannusch; Lawrence L. Micek
Original assignee: Cargill, Incorporated
Priority date: 2010-06-18
Filing date: 2011-06-17
Publication date: 2011-12-22

Abstract

The present invention relates generally to improved adhesive compositions that contain a reduced amount of solids, and using this improved adhesive composition in a process for making products such as corrugated paperboard. In one aspect, the process produces consistently high quality corrugated paperboard and eliminates or considerably reduces common defects such as warping, washboarding, and brittle paperboard, while using significantly less adhesive than the current corrugating process. In another aspect, the addition of less water to the corrugated paperboard allows less energy to be used to dry the corrugated paperboard.

Description

REDUCED SOLIDS ADHESIVE COMPOSITION AND RELATED METHODS

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of the United States Provisional Patent

Application No. 61/356,234, filed June 18, 2010, entitled REDUCED SOLIDS ADHESIVE COMPOSITION AND RELATED METHODS, which is hereby incorporated by reference in its entirety.

FIELD

[0002] The present invention relates generally to improved adhesive compositions that contain a reduced amount of solids. Aspects of the present invention are particularly directed to using this improved adhesive composition in a process for making products such as corrugated paperboard. In one aspect, the process produces consistently high quality corrugated paperboard and eliminates or considerably reduces common defects such as warping, washboarding, and brittle paperboard, while using significantly less adhesive than the current corrugating process. In another aspect, the addition of less water to the corrugated paperboard allows less energy to be used to dry the corrugated paperboard.

BACKGROUND

[0003] The commonly used corrugating process utilizes a liner paper such as Kraft liner paper (a strong paper made largely of bleached or unbleached sulfate pulp used to line corrugated paperboard) that unwinds from a paper roll and passes over a pre-heat roll before going into a single facer gluing section. A medium such as a Kraft medium is unwound from a paper roll and passes under a steam shower before passing into the corrugating rolls to become a corrugating medium having flute tips. The corrugating rolls are at a temperature of

approximately 300 degrees Fahrenheit (°F) (about 149°Celsius). After corrugation, the adhesive from the adhesive applicator roll is applied to the flute tips of the corrugated medium, and the fluted corrugated medium is bonded to the single face liner paper at the combining roll.

[0004] The adhesive typically used in the corrugating process of the Stein Hall system consists of a mixture of gelatinized starch (sometimes referred to as the carrier starch), and an ungelatinized starch (sometimes referred to as the secondary starch). The Stein Hall formulation commonly includes sodium hydroxide and borax to decrease the gelatinization temperature of the ungelatinized secondary starch and to increase the viscosity of the adhesive at the flute after gelatinization. The Stein Hall adhesive typically used is currently formulated at a total solids of 22 -26 percent by weight (% by wt.) or even higher.

[0005] The Stein Hall adhesive is set with heat and pressure from the combining roll and the corrugating roll as well as heat from the Kraft liner paper that has passed over the pre-heat roll. This heat causes the adhesive viscosity to increase because water is absorbed by the secondary starch as it is gelatinized by the water in the formula while in the presence of heat.

[0006] At the other end of the corrugator, the other side of the fluted corrugated medium picks up adhesive onto the flute tips by application from a glue applicator roll of the starch adhesive. A second Kraft liner (sometimes referred to as the double backer liner), is unwound from a paper roll and passed over the pre-heat roll, and is then bonded to the fluted corrugated medium at the flute tips with the adhesive, thereby forming a corrugated paperboard. The heat from the double backer liner gelatinizes the secondary starch and creates a high viscosity gel at the flute-liner interface. The corrugated paperboard then passes through an extended hot plate section which further evaporates water and increases the bond strength of the fluted paper to the single facer and double backer liners. Currently, the Stein Hall adhesive is used at an application rate of approximately 2-3 pounds per thousand square feet (msf) of C-flute single- wall corrugated paperboard produced.

[0007] Applying the appropriate amount of heat to the liner paper at the pre-heat rolls is critical to the production of defect-free paperboard. Too much, too little, or an uneven amount of heat applied can result in defects in the paperboard. For example, too much heat can result in brittle paperboard. This excess heat can cause the water to be evaporated too rapidly from the liner paper, resulting in the loss of bonding due to the secondary starch having insufficient water available to gel. In addition, the liner paper itself can be damaged by excessive heating. Too little heat can result in a defect called "washboarding", when the liner paper may be excessively saturated in the flute area where the adhesive is applied, resulting in uneven paper shrinkage between the adhesive area over the flutes and the area between the flutes where no adhesive is applied. Unbalanced or uneven heat can result in a defect called "warping" of the corrugated paperboard due to the liner papers having different amount of shrinkage upon exiting the hot plate section. These defects in turn cause problems in the conversion of the corrugated paperboard to boxes. Jamming from warping can occur as the corrugated paperboard cannot pass through the box conversion machine, thereby causing loss of production time. Washboarding often causes poor print quality on corrugated paperboard resulting in unacceptable box quality. In the current corrugating process, the correct amount of heat is difficult to maintain as the corrugator speed varies from idling at 50 feet per minute to over 1,000 feet per minute at full speed.

SUMMARY

[0008] One embodiment is directed toward an adhesive composition, comprising a starch compound, a borate, an alkaline hydroxide, and a rheology modifier. In one embodiment, the starch compound is a gelatinized starch, an ungelatinized starch, or combinations thereof, the borate is sodium borate, sodium tetraborate, disodium tetraborate, or combinations thereof, the alkaline hydroxide is sodium hydroxide; and the rheology modifier is a synthetic polymer, a naturally occurring polymer, or combinations thereof. The rheology modifier comprising a synthetic polymer can be carboxymethylcellulose, hydroxyethylcellulose, polyacrylic acid, polyvinylacrylic acid, polyacrylamide, polyvinyl alcohol, polyoxyethylene, or combinations thereof. The rheology modifier comprising a naturally occurring polymer can be xanthan gum, guar gum, or combinations thereof. In one embodiment, the rheology modifier is

carboxymethylcellulose.

[0009] Another embodiment is directed toward an adhesive composition, comprising a starch compound, a borate, an alkaline hydroxide, and a rheology modifier, where the adhesive composition further comprises water. In a further embodiment, the starch compound comprises 10-21% by wt., the sodium borate compound comprises 0.10-0.30% by wt, the alkaline hydroxide comprises a 50% solution of sodium hydroxide comprising 0.95-1.10%) by wt., the rheology modifier comprises a 0.5%> solution comprising 1.30-1.60%) by wt., and the water comprises 75-85%> by wt. of the adhesive composition. In an alternative embodiment, the rheology modifier comprises less than 20%> by wt. of the adhesive composition.

[00010] In a second embodiment, a process for producing a corrugated paperboard product is disclosed using a reduced amount of an adhesive composition comprising the steps of providing a liner paper and a medium, further comprising corrugating the medium to form a corrugated medium; preparing a reduced solids adhesive composition comprising a starch compound that is 10-21%o by wt.; a sodium borate compound that is 0.10-0.30%> by wt.; a 50%> Sodium Hydroxide solution comprising 0.95-1.10% by wt; a 0.5% rheology modifier solution that is 1.30-1.60% by wt.; and water that is 75-85% by wt. of the adhesive composition;

applying the adhesive composition to the liner paper, which has been heated to a temperature of between 70°C to 120°C, and combining the liner paper and corrugated medium to form a corrugated paperboard product.

[0001 1] In another embodiment, the amount of adhesive composition applied to the liner paper, corrugated medium, or both, is reduced by up to 50% as compared to the amount used by a standard process for making a corrugated paperboard product. In an alternative embodiment, the amount of adhesive composition applied to the liner paper, corrugated medium, or both, is in the range of 0.5 lbs. per 1 ,000 sq. ft. (msf) of corrugated paperboard produced up to 1.8 msf. In yet another embodiment, the process further comprises applying a controlled amount of water to the liner paper and maintaining the liner temperature in the range of between 70°C to 90°C.

DETAILED DESCRIPTION

SELECTED DEFINITIONS

[00012] As used herein, the following terms shall have the following meanings:

The term "adhesive composition" as used herein refers to the compound used to bond at least one liner paper to at least one corrugated medium. The adhesive composition is typically a starch-based compound with other compounds to modify the viscosity and rheology of the composition.

[00013] The term "starch" as used herein refers to a carbohydrate consisting of a large number of glucose units joined together through glycosidic bonds as a polysaccharide. Starches can be modified chemically or used without modification (i.e., naturally occurring). Modified starches are native starches which have been modified e.g. by enzymatic, chemical and/or heat treatment and include, by way of example only, oxidised starches, acid-thinned starches, esterified starches, etherified starches, dextrins, maltodextrins, cross-linked starches and so on.

[00014] The term "borate" as used herein refers to a chemical compound containing boron ions, including sodium borate, sodium tetraborate, and disodium tetraborate.

[00015] The term "alkaline hydroxide" as used herein refers to a compound that contains the anion OH. This can include compounds such as sodium hydroxide, potassium hydroxide, calcium hydroxide, and the like.

[00016] The term "gelatinized starch" as used herein refers to a starch compound where heat or chemicals such as an alkali or hydroxide are applied or added to it. It is sometimes referred to as the primary or carrier starch as it is often the first starch compound added to the adhesive composition.

[00017] The term "ungelatinized starch" as used herein refers to a starch compound that has not been exposed to chemical or heat treatment to increase its viscosity. It is sometimes referred to as the secondary starch as it is often added later to the adhesive composition.

[00018] The term "synthetic polymer" as used herein refers to a compound that is chemically made and can be used as a rheology modifier. Synthetic polymer compounds can include carboxymethylcellulose, hydroxyethylcellulose, polyacrylic acid, polyvinyl acrylic acid, polyacrylamide, polyvinyl alcohol, and polyoxyethylene.

[00019] The term "naturally occurring polymer" as used herein refers to a compound that is found in nature that can be used as a rheology modifier. Naturally occurring polymer compounds can include xanthan gum and guar gum.

[00020] The term "corrugated paperboard product" as used herein refers to the product comprising at least one liner paper and at least one corrugated medium. The corrugated paperboard product can be single face (one corrugated medium bonded to one liner paper), single wall (one corrugated medium bonded between two liner papers) or double wall (two layers of corrugated medium between three liner papers).

[00021 ] The term "liner paper" as used herein refers to a homogenous sheet of paper that is used to form a corrugated paperboard product. The liner paper typically is bonded to the corrugated medium at the flute tips. Examples of liner paper can include Kraft liner or recycled liner.

[00022] The term "medium" as used herein refers to the starting material of chemical or semi-chemical pulp or waste paper that is used to make the corrugated medium. Examples of medium can include semi-chemical, recycled or Kraft medium.

[00023] The term "corrugated medium" as used herein refers to the medium after it has passed through corrugating rolls that form wave shapes into the medium.

[00024] The term "flute tip" as used herein refers to the top of the waves that are formed in the medium after it has run through the corrugating rolls.

ADHESIVE COMPOSITIONS AND METHODS

[00025] The present invention discloses a significantly lower solids Stein Hall adhesive composition comprising at least one starch compound, sodium hydroxide, borax, water, and a rheology modifier. The starch compound can include a gelatinized starch and an ungelatinized starch. The rheology modifier can be a high molecular weight water soluble polymeric material. The rheology modifier can be either a synthetic polymer or a naturally occurring polymer.

Examples of synthetic high molecular weight water soluble polymeric materials are

carboxymethylcellulose, hydroxyethylcellulose, polyacrylic acid, polyvinylacrylic acid polyacrylamide, polyvinyl alcohol, and polyoxyethylene. Examples of naturally occurring high molecular weight water soluble polymeric materials include xanthan gum and guar gum.

[00026] The rheology modifier in the Stein Hall adhesive composition of the present invention modifies the rheology of the composition in such a manner that up to a 50% decrease in the amount of adhesive composition is applied. For example, this can be accomplished by setting the metering gap on the adhesive composition applicator rolls to be decreased by up to 50%, thereby lowering the amount of adhesive placed on the flute tip by up to 50%.

[00027] In addition, by lowering the solids level of the Stein Hall composition from the typical levels of 22 - 26% solids by weight (% wt. solids) or higher down to less than 20% solids, preferably less than 18%_> wt. solids, preferably less than 15% wt. solids and preferably in the range of between 10-14% wt. solids, the adhesive film will split in such a way as to leave less starch and water deposited on the flute tip than with higher solids adhesives. This results in reducing the amount of adhesive composition used by up to 30% as adhesive commonly used. Alternatively, the adhesive usage rate of adhesive composition added to the liner paper or flute tip of the corrugated medium can be as low as 0.5 pounds per thousand square feet of corrugated paperboard produced. As a result of the modified rheology of the adhesive composition, at this low application rate, the adhesive composition runs cleanly in the glue applicator without spattering or slinging. This lower amount of splattering or slinging will also result in less maintenance time cleaning the areas on the corrugators around the double backer and the single facer gluing sections.

[00028] In conjunction with the application of this adhesive composition, good temperature control of the liner papers in the range of 70-120°C and more particularly in the range of 70-90°C is important.

[00029] One method to maintain this temperature range and optimum moisture level of 6- 8%o of the paper is to apply a controlled amount of water to the paper and then exposing the side of the paper coated with water to heating cylinders commonly found on corrugators. This can assist in maintaining the temperature in the range of interest. As an example, this may be done by using a thin-film liquid metering machine known as a WaterDeck™, designed and manufactured by Kohler Coating, Inc. By controlling the temperature to the range mentioned above, the paper temperature and moisture levels are maintained so that reduced amounts of adhesive can be applied.

[00030] Reduction of adhesive application is achieved both by reducing the solids of the Stein Hall adhesive and by addition of the rheology modifier to the Stein Hall adhesive composition. The addition of this rheology modifier to Stein Hall composition results in Stein Hall adhesives formulations of low solids and controlled rheology so that low adhesive add-ons may be achieved. This low adhesive add-on results in less water added to the corrugated paperboard, enabling the production of corrugated paperboard with reduced defects resulting from washboarding and warping.

EXAMPLES

[00031 ] Aspects of certain compositions and methods in accordance with aspects of the invention are illustrated in the following examples.

[00032] The following examples are formulations of a standard Stein Hall formula at 25% solids, a standard Stein Hall formula containing polymeric material (such as

Carboxymethylcellulose) with 25% solids, and a reduced solids Stein Hall adhesive composition containing rheology modifiers with solids levels of about 20%.

SUBSTITUTE SHEET (RULE 26) Standard Stein Hall Standard Stein Hall Stein Hall Recipe

Recipe Recipe with Polymer with Polymer at 20% solids

Water 1,100 1b 27.50% 1050 lb 26.25% 1108 1b 27.70% 0.5% Carboxymeihylcellutose Solution 50 lb 1.25% 52.4 lb 1.31% (Akucell AF 3285 from Akzo Nobel)

CO

c Pearl Dent Starch 112 lb 2.80% 112 1b 2.80% 117.6 lb 2.94%

CO Heat 50 - 59°C

CO

_ 50% Sodium Hydroxide Solution 37 lb 0.93% 371b 0.93% 38.8 lb 0.97%

H Quench Water 1,812 1b 45.30% 1,812 1b 45.30% 1952 1b 48.80%

H Borax (5 Mole) 14 1b 0.35% 141b 0.35% 11.2 1b 0.28% m Reheat 32 - 44°C

i£ Pearl Dent Starch 9251b 23.12% 9251b 23.12% 720 1b 18.00% m Mix 8 minutes

m

—

73

C

I- m

isj 25% solids 25% solids 20.4% solids

[00033] The following examples show various formulations of an adhesive composition with reduced amounts of solids, ranging from about 11% to about 19%. The reduced amount of solids in the adhesive composition allows less adhesive composition usage in the process saving on product and allowing a more consistent product to be produced with less warping, washboarding and brittle paperboard.

SUBSTITUTE SHEET (RULE 26)

Claims

CLAIMS We claim:

1. An adhesive composition, comprising: a starch, a borate, an alkaline hydroxide, and a rheology modifier.

2. The composition of claim 1 , wherein the starch is a gelatinized starch, an ungelatinized starch, or combinations thereof; wherein the borate is sodium borate, sodium tetraborate, disodium tetraborate, or combinations thereof; wherein the alkaline hydroxide is sodium hydroxide, potassium hydroxide, calcium hydroxide; and wherein the rheology modifier is a synthetic polymer, a naturally occurring polymer, or combinations thereof.

3. The composition of claim 2, wherein the rheology modifier comprises a synthetic polymer further comprising carboxymethylcellulose, hydroxyethylcellulose, polyacrylic acid, polyvinyl acrylic acid, polyacrylamide, polyvinyl alcohol, polyoxyethylene, or combinations thereof and wherein the naturally occurring polymer comprises xanthan gum, guar gum, or combinations thereof.

4. The composition of claim 3, wherein the rheology modifier is carboxymethylcellulose.

5. The composition of claim 2, wherein the adhesive composition further comprises water.

6. The composition of claim 6, wherein the starch compound comprises 10-21 % by wt.; wherein the sodium borate compound comprises 0.10-0.30% by wt., wherein the alkaline hydroxide comprises a 50% solution of Sodium Hydroxide comprising 0.95-1.10% by wt., wherein the rheology modifier comprises a 0.5% solution comprising 1.30-1.60% by wt., and wherein the water comprises 75-85% by wt. of the adhesive composition.

7. The composition of claim 6, wherein the rheology modifier comprises less than 20% by wt. of the adhesive composition.

8. A process for producing a corrugated paperboard product using a reduced amount of adhesive composition, comprising the steps of: providing a liner paper and a medium, further comprising corrugating the medium to form a corrugated medium;

preparing a reduced solids adhesive composition comprising: a starch compound comprising 10-21 % by wt.; a sodium borate compound comprising 0.10-0.30% by wt.; a 50% sodium hydroxide solution comprising 0.95-1.10% by wt.; a 0.5% rheology modifier solution comprising 1.30-1.60% by wt.; and water comprising

75-85% by wt. of the adhesive composition;

applying the adhesive composition to the liner paper, which has been heated to a temperature of between 70°C to 120°C, and corrugated medium; and combining the liner paper and corrugated medium to form a corrugated paperboard product.

9. The process of claim 8, wherein the amount of adhesive composition applied to the liner paper, corrugated medium, or both, is in the range of 0.5 lbs. per 1,000 sq. ft. of corrugated paperboard produced (msf) to 1.8 msf.

Stein Hall Recipe Stein Hall Recipe Stein Hall Recipe

with Polymer at 18% solids with Polymer at 15% solids with Polymer at 11% solids

Water 1152 lb 12001b 30.00% 13001b 32.50%

0.5% Carboxymethylcellulose Solution 54 lb 56.8 lb 1.42% 62 lb 1.55% (Akucell AF 3285 from Akzo Nobel)

Pearl Dent Starch 1221b 1281b 3.20% 140 lb 3.50% Heat 50 - 59°C

50% Sodium Hydroxide Solution 40 lb 421b 1.05% 44 lb 1.10%

Quench Water 1982.41b 2086 lb 52.83% 2129.21b 53.23%

Borax (5 Mole) 9.6 lb 7.21b 0.18% 4.8 lb 0.12% Reheat 32 - 44°C

Pearl Dent Starch 640 lb 4801b 12.00% 320 lb 8.00% Mix 8 minutes

18.6% solids 15.1% solids 11.3% solids

[00034] As stated above, the foregoing is merely intended to illustrate various embodiments of the present invention. The specific modifications discussed above are not to be construed as limitations on the scope of the invention. It will be apparent to one skilled in the art that various equivalents, changes, and modifications may be made without departing from the scope of the invention, and it is understood that such equivalent embodiments are to be included herein. All references cited herein are incorporated by reference as if fully set forth herein.

SUBSTITUTE SHEET (RULE 26)