STARCH-BASED AQUEOUS ADHESIVE COMPOSITIONS AND USES THEREOF

Abstract

The invention relates to starch-based aqueous adhesive compositions and uses thereof. Provided is an aqueous adhesive composition comprising highly branched starch (HBS) obtained by treatment of starch or starch derivatives with a glycogen branching enzyme, and further comprising a carboxymethyl (CM) polysaccharide derivative, such as a carboxymethyl ether of starch, cellulose or a combination thereof. Also provided is a method for adhering a first substrate to a second substrate, comprising applying to at least said first or said second substrate said starch-based adhesive, and a glued or glueable product obtainable thereby.

Claims

1-11. (canceled)

12. A method for preparing an adhesive composition comprising a branched starch with a viscosity shear rate index of more than or equal to 1.2, wherein the viscosity is measured at a temperature of 25 C., comprising mixing enzymatically branched starch with water and at least one carboxymethylated polysaccharide.

13. A method for adhering a first substrate to a second substrate, comprising applying to at least said first or said second substrate a water-based adhesive composition comprising an aqueous adhesive composition comprising highly branched starch (HBS) obtained by treatment of starch or starch derivatives with a glycogen branching enzyme (EC 2.4.1.18), and further comprising a carboxymethyl (CM) polysaccharide derivative, wherein at least one of said substrates is a paper, glass or wood substrate.

14. Method according to claim 13, wherein said first and/or said second substrate are part of a glued or glueable product, preferably wherein the product is selected from the group consisting of paper sacks, paper bags, envelopes, wall paper, gummed tape, spiral and convolute paper tubes.

15. Method according to claim 13, wherein said adhering comprises laminating, preferably wherein said laminating comprises litholaminating, off line paper to paper or paper to board or board to board laminating, graphic board laminating, solid board laminating, honeycomb laminating, aluminum foil laminating or duplex wall paper laminating.

16. A glued, glueable or laminated product obtainable by a method according to claim 14.

Description

LEGEND TO THE FIGURES

[0042] FIG. 1: Shear rate versus Normal stress analysis of an adhesive composition (1) of the prior art comprising fully gelatinised starch (FGS) versus an adhesion composition (2) of the invention comprising highly branched starch (HBS). For details see Example 7.

[0043] FIG. 2: Large Amplitude oscillatory shear (LAOS) analysis of an adhesive composition (1) of the prior art comprising fully gelatinised starch (FGS) versus an adhesion composition (2) of the invention comprising highly branched starch (HBS). Shown are the storage modulus (G) and the loss modulus (G). For details see Example 7.

[0044] FIG. 3: Oscillation Frequency Sweep analysis of an adhesive composition (1) of the prior art comprising fully gelatinised starch (FGS) versus an adhesion composition (2) of the invention comprising highly branched starch (HBS). Shown are the storage modulus (G) and the loss modulus (G). For details see Example 7.

EXPERIMENTAL SECTION

Example 1

Preparation of Highly Branched Starch (HBS)

[0045] HBS was produced by jet cooking. A 17% dry solid potato starch slurry was jet cooked (149-153 C., 8 min residence time, pressure 4 bar). After cooling down to 70 C. and adjusting the pH to 6.1, 1000 units of branching enzyme (measured as the change in the absorbance of a iodine/iodide starch complex at 660 nm) were added per gram dry substance of starch. The branching enzyme used was the product NS28067 of Novozymes, a pilot plant product containing the branching enzyme of Rhodothermus obamensis.

[0046] After 20 h of incubation, the enzyme was inactivated by lowering the pH to 2.5 with 4M HCl. After 35 min the pH was readjusted to 4.5. Then the solution was filtered over a filter with pore size of 2-4 micrometer, followed by ion-exchange (Aquadem E200. Kruger). Finally, the solution was dried by evaporation of the water first at 61 C. and then spray dried at 200 C. (temp out 82 C.). This yielded starch having a degree of branching of 10%.

[0047] The activity of the branching enzyme is determined by monitoring changes in the iodine/iodide/amylose complex as a result of the branching enzyme activity. A substrate solution is prepared by adding 10 mg Amylose type III (Sigma) to 0.5 ml 2 M NaOH, subsequently adding 1 ml ultra pure water and then adjusting the pH by adding 0.5 ml 2 M HCl and 7.8 ml phosphate buffer (pH 7.2). A iodine/iodide stock solution is prepared by adding 0.26 g I.sub.2 and 2.6 g KI to 10 ml ultra pure water. To 100 microliter of this stock solution 50 microliter 2 M HCl is added and 26 ml ultra pure water (stop reagent). The activity of the enzyme is determined by mixing 50 microliter of appropriately diluted enzyme to 50 microliter of amylose substrate solution and incubation this for 30 min at 60 C. Then 2 ml of stop reagent is added and after mixing well the absorbance is measured at 660 nm (the absorbance should be between 0.15 and 0.3). The activity (U/mL) is calculated using the following formula:

U/ml=(ODreferenceODsample)100%dilution/(ODreferenceODblank)/30 min/0.05 ml

Example 2

Branched Starch-Based Adhesive Compositions and their Properties

[0048] This reference example shows the Newtonian behaviour of known HBS-based adhesives.

[0049] Four different types of HBS were prepared. HBS-P denotes highly branched potato starch obtained as described in Example 1 herein above. HBS-WM1 denotes a liquid highly branched waxy maize starch preparation obtained according to Example 1 of US2012/0121873. Since the drying method is not specified in US2012/0121873, two different dried waxy maize preparations were made. HBS-WM2 refers to HBS-WM1 dried using a Compact Anhydro DanMark spray drier operated at an inlet temperature of 250 C. and an outlet temperature of 110 C.

[0050] HBS-WM3 was produced as follows. A 18% dry solid waxy maize slurry was jet cooked at 160 C. After cooling to 70 C. and adjusting the pH to 6.2, 1000 units of branching enzyme (measured as the change in the absorbance of a iodine/iodide starch complex at 660 nm) were added per gram dry substance of starch. The branching enzyme used was product NS28067 of Novozymes. After a 19 h incubation, the enzyme was inactivated by lowering the pH to 2.7 with 10% HCl. After 30 min the pH was readjusted to 4.5 with 10% NaOH. The solution was then filtered over a filter with pore size of 8-12 micrometer, followed by mixed ion-exchange (AMBERLITETm MB20 Resin) chromatography. Finally the solution was spray dried (250 C. to 110 C. on a Compact Anhydro DanMark spray drier). This yielded starch having a degree of branching of 10%. Each of the HBS preparations was dissolved by adding the product in about 10 seconds (in a steady flow) to demineralised water (251 C.) in a plastic beaker (90 mm), while being stirred at 1000 rpm with a 3-propeller stirrer (60 mm) for 30 minutes. After defoaming (30 min. 5 rpm), the adhesive compositions were brought onto a refraction of 50%.

[0051] Brookfield viscosityThe viscosity of the solution (201 C.) is determined with a digital Brookfield DV-I viscosimeter (mPa.Math.s) using the correct applicable spindle at 20 rpm during 15 seconds (or five revolutions)

[0052] StabilityFor determining the viscostability of the liquid adhesive solution, the solution is preserved by addition of 0.1% Proxel BZ plus from Lonza and stored at 201 C. during a certain period and every few days the viscosity the solution (201 C.) is registered.

[0053] AdhesionWet tackThe wet tack of the adhesive solution is determined with a Fipago-Adhesion tester (PKL system) in a conditioned room (RH=502%, T=231 C.). A thin adhesive film (standard 60 gm) of liquid adhesive (231 C.) is applied with a wire winded rod on the smooth side of a standard kraft paper stripe (Natural machine-glazed kraft paper (one smooth and shiny side, one matt side) Manufacterer: Sopal Doetinchem, The Netherlands; Gurley porosity: 72 s; PPS smoothness (smooth side): 3.42 m; Cobb.sup.60: 24 g/m.sup.2; Grammage: 85 g/m.sup.2; Dennison wax test: 18; 30200 mm). After the open time is exceeded (standard 5 s) the glued paper strip is placed on another piece of paper (kraftliner Pitea Royal Brown, Manufacterer: Kappa Smurfit, Sweden; Supplier: Fipago, The Netherlands (Fipago 2006 kraftline); Grammage: 200 g/m.sup.2; Cobb.sup.1800: 86 g/m.sup.2; Dennison wax test: 18; 60100 mm) by means of a metal pressure roller (standard 500 g). After the close time is exceeded (standard 3 s) the two pieces of paper are separated from each other. The wet tack is given as work (cJ) needed to separate the pieces of paper is measured.

[0054] AdhesionSetting timeFor determining the setting time of the adhesive the above method for determining the wet tack is followed, where as the open time is set on 0 seconds and the closed time is varied (standard in the interval 0 . . . 20 seconds, but can be longer if fibre tear has not yet occurred). Every adhesive is characterized by at least five different closed times, yielding a more or less sigmoid curve. This curve represents the work needed to overcome the bond strength as function of closed time. Results are given as work (cJ). The value for the setting time (s) is the time where the peel strength of 40 cJ is exceeded.

[0055] RheologyA flow curve of an adhesive is recorded by a Physica Rheolab MC 100 Rheometer. 1.5 ml adhesive under cone and plate MK 22, gap: 0.05mm, Temperature: 25 C.

[0056] Profile: [0057] 1.sup.st interval:. Shear rate ramp log: 0.1 . . . 1000 s.sup.1: 30 points 6 s (180 s) [0058] 2.sup.nd interval:. Shear rate: 1000 s.sup.1: 10 points 6 s (60 s) [0059] 3.sup.rd interval:. Shear rate ramp log: 1000 . . . 0.1 s.sup.1 30 points 6 s (180 s)

[0060] Depending on resistance of the liquid, the maximum of 1000 s.sup.1 is sometimes not reached (maximum torque is exceeded).

[0061] Compatibility: 100 ml of the adhesive is stored in a well closed glass jar at 20 C. The adhesive is evaluated 1 day and 1 week after preparation. Incompatibility can be recognized by the appearance of two layers or a buttermilk structure at the wall of the glass jar. Compatibility is indicated with +, incompatibility is indicated with .

[0062] Table 1 shows the various properties of the compositions.

TABLE-US-00001 Composition 1 2 3 4 HBS-P 100 g HBS-WM 1 165 g HBS-WM 2 100 g HBS-WM 3 100 g water 100 g 35 g 100 g 100 g Properties: Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C. 1 day after preparation 3150 2860 2850 4530 Refraction [%] 49.7 50.0 49.9 49.9 pH 4.16 1.68 1.80 5.98 Appearance trans- trans- trans- trans- parant parant parant parant Wet Tack 60 m [5.3] 5 5.5 5 9.7 Setting time 60 m 12.5 12.5 11.5 9.5 Time till 40 cJ Rheology Physical viscosity [mPa .Math. s] Interval 1-1000 Shear rate 10 s1 1910 1919 1970 3018 Shear rate 500 s1 1912 1854 1812 2802 Viscosity index Shear rate 10/500 1.00 1.03 1.09 1.08

[0063] The above results demonstrate that HBS originating from potato or waxy maize both show a Newtonian behaviour.

Example 3

Water-Based Adhesive Compositions comprising HBS and CM polysaccharide

[0064] This example describes the effects of cellulose derivatives on the rheology of a HBS-containing adhesive composition. The HBS was prepared from potato starch as described in Example 1. Five different cellulose ethers were tested. Methocel 254 is a HPMC (hydroxypropylmethylcellulose) from Dow Chemicals. Natrosol 250 HR is a HEC (hydroxyethyl cellulose) from Ashland. Gabrosa P200G is a CMC (carboxymethylcellulose) from AkzoNobel. Klucel HIND is a HPC (hydroxypropylcellulose) from.Ashland. Walocell MKX 40000 PF01 is a HEMC (hydroxyethylmethylcellulose) from Dow Chemicals. The components were mixed and dissolved in demineralised water at 25 C. during stirring at 1000 rpm for 30 minutes. And thereafter defoamed at 25 C. by stirring at 5 rpm for 30 minutes. Table 2 below shows the composition and properties of the adhesive compositions.

TABLE-US-00002 TABLE 2 Screening of applicability of various cellulose ethers as rheology-modifying additive. HBS-CE Composition 1 2 3 4 5 6 HBS.sup.3 34.3 g 34.3 g 34.3 g 34.3 g 34.3 g 34.3 g water 48.3 g 48.3 g 48.3 g 48.3 g 48.3 g 48.3 g HPMC 0.8 g HEC 0.8 g CMC 0.2 g HPC 0.8 g HEMC 0.8 g Color transparant Transparant Transparant transparant Transparant Transparant Properties: Brookfield viscosity [mPa .Math. s] 20 rpm. 20 C., 1 day after preparation 500 940 .sup.4 980 .sup.4 1700 .sup.600 .sup.4 780 .sup.4 Refraction [%] 41.5 .sup.43.9 .sup.43.4 41.3 42.3 .sup.42.7 Compatible with HBS n.a. .sup.1 .sup.1 + .sup.2 .sup.1 Rheological behavior Newtonian n.a. n.a. Shear-thinning Newtonian n.a. Physica viscosity [mPa .Math. s] Interval 1-1000 Shear rate 10 s1 401 1051 522 Shear rate 500 s1 378 457 429 Shear rate 1000 s1 381 429 428 Viscosity index Shear rate 10/500 1.06 2.30 1.22 Shear rate 10/1000 1.05 2.45 1.22 .sup.1 Separation of cellulose ether and HBS (top layer cellulose ether, bottom layer HBS) was observed .sup.2 Turbid mixture .sup.3Potato starch based .sup.4 After homogenization of the mixture

[0065] As is clear from Table 2, only the adhesive compositions comprising carboxymethylated cellulose (column 4) displayed a good compatibility with HBS and a desirable shear-thinning behavior.

Example 4

Water-Based Adhesive Compositions comprising HBS and Starch

[0066] In this example, twenty different starch derivatives were screened at a concentration of 2% by weight of the HBS. Table 4 summarizes their effects on rheological behaviour and the compatibility with HBS.

TABLE-US-00003 TABLE 4 Screening of starch derivatives Rheological Starch Modification behaviour Compatibility source Chemical Physical mixture with HBS potato Acetylated distarch Drumdried Newtonian phosphate potato Distarchphospate Drumdried Newtonian potato Acetylated distarch Drumdried Newtonian phospate potato Distarch phospate Drumdried Newtonian (+emulsifier) potato Hydroxypropylation Spray cooked Newtonian potato Acetylated distarch Drumdried Newtonian adipate waxy Extruded Newtonian potato potato Hydroxypropylated Drumdried Newtonian distarch phosphate potato Hydroxypropylation Newtonian potato Oxidization Drumdried Newtonian potato Sodium octenyl Drumdried Newtonian succinate potato Acid degraded (+Na-3) Drumdried Newtonian wheat Drumdried Newtonian + waxy Peroxide degraded (+filler) Drumdried Newtonian + potato potato Oxidization and Newtonian + hydroxyethylation maize Carboxymethylated Drumdried Shearthinning + and crosslinked potato Carboxymethylated Extruded Shearthinning + waxy Carboxymethylated Extruded Shearthinning + potato potato Carboxymethylated, Drumdried Shearthinning + hydroxypropylated and crosslinked potato Carboxymethylated Drumdried Shearthinning + and crosslinked

[0067] The results shown in Table 4 demonstrate that, also for starch-based polysaccharides, the presence of carboxymethyl groups is important to confer a shear-thinning rheology and/or compatibility to a HBS-based adhesive.

Example 5

Exemplary Shear-Thinning HBS-Based Adhesives

[0068]

TABLE-US-00004 TABLE 5 Composition: 1 2 3 HBS 245 g 245 g 245 g SOLVITOSE C5 2.5 g QUICKSOLAN SPR 5.0 g Water 345 g 345 g 345 g Properties: Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C., 2 h after preparation 570 1170 1355 Refraction [%] 41.3 41.6 41.9 pH 5.4 5.8 5.2 Wet Tack 60 m [5.3] 2 2.75 3 Setting time 60 m 16 15.5 15 [Time till 40 cJ [s] Viscosity-stability Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C. After 2 hours 515 1075 1340 After 4 weeks 585 1220 1365 Viscosity-stability index [4 weeks/2 hours] 1.14 1.13 1.02 Rheological behavior Newto- Shear- Shear- nian thinning thinning Physical viscosity [mPa .Math. s] Interval 0.1-1000 Shear rate 10 s1 443 988 963 Shear rate 500 s1 440 741 710 Shear rate 1000 s1 441 713 683 Viscosity index Shear rate 10/500 1.01 1.33 1.36 Shear rate 10/1000 1.00 1.39 1.41

[0069] The results in Table 5 demonstrates that addition of the CM-polysaccharides Solvitose C5 or Quicksolan SPR to HBS results in the desired rheological behavior without sacrificing the relevant adhesive properties like wet tack, setting speed and stability.

Example 6

Various Types and Dosages of CM Polysaccharide Show the Beneficial Rheological Effect

[0070] This example further demonstrates the effect of type and dosage (based on dry weight) of carboxymethyl polysaccharide. The carboxymethyl polysaccharides tested were Solvitose C5 (CM potato starch from AVEBE), Quicksolan SPR (CM amylopectin potato starch from AVEBE), Gabrosa T 4000 C (CM cellulose from AKZO NOBEL) and Finnfix 2 (CM cellulose from Metsa-Serla).

[0071] All compositions with carboxymethyl polysaccharide derivative additions result in the desired rheological behaviour while relevant adhesive properties like wet tack, setting speed and stability were retained or even improved. By using different types and/or dosages of carboxymethyl polysaccharides, the adhesive properties (viscosity, rheology, wet tack and setting speed) can be optimized to the specific demands of the various possible applications.

TABLE-US-00005 TABLE 6A Solvitose C5 in the range of 1.0 to 3.9 w % Composition: 1 2 3 4 HBS 245 g 245 g 245 g 245 g SOLVITOSE C5 2.5 g 5 g 10 g Water 345 g 345 g 345 g 345 g Properties: Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C., 2 h after preparation 570 1005 2315 8580 Refraction [%] 41.3 42.1 42.3 43.0 pH 5.4 5.4 5.7 6.1 Wet Tack 60 m [5.3] 2 3 4 7 Setting time 60 m [0, . . .] Time till 40 cJ [s] 16 16.5 16.5 16.5 Viscosity-stability Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C. After 2 hours 515 1005 2315 8580 After 4 weeks 585 1200 2425 8950 Viscosity-stability index [4 weeks/2 hours] 1.14 1.19 1.05 1.04 Rheological behavior Newto- Shear- Shear- Shear- nian thinning thinning thinning Physical viscosity [mPa .Math. s] Interval 0.1-1000 Shear rate 10 s1 443 842 1834 5499 Shear rate 500 s1 440 688 1096 2120 Shear rate 1000 s1 441 658 1002 1778 Viscosity index Shear rate 10/500 1.01 1.22 1.67 2.59 Shear rate 10/1000 1.00 1.28 1.83 3.09

TABLE-US-00006 TABLE 6B Quicksolan SPR in the range of 3.9 to 9.3 w % Composition: 1 2 3 4 5 HBS 245 g 245 g 245 g 245 g 245 g QUICKSOLAN SPR 10 g 15 g 20 g 25 g Water 345 g 345 g 345 g 345 g 345 g Properties: Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C., 2 h after preparation 570 2615 4100 5670 7260 Refraction [%] 41.3 43 43.4 43.9 44.1 pH 5.4 5.63 5.82 5.98 6.13 Wet Tack 60 m [5.3] 2 6 9 11 12 Setting time 60 m [0, . . .] Time till 40 cJ [s] 16 14 14 14 13 Viscosity-stability Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C. After 2 hours 515 2615 4100 5670 7260 After 4 weeks 585 2580 3960 5590 7080 Viscosity-stability index [4 weeks/2 hours] 1.14 0.99 0.97 0.99 0.98 Rheological behavior Newto- Shear- Shear- Shear- Shear- nian thinning thinning thinning thinning Physical viscosity [mPa .Math. s] Interval 0.1-1000 Shear rate 10 s1 443 1866 2649 3822 4712 Shear rate 500 s1 440 932 1215 1580 1867 Shear rate 1000 s1 441 860 1100 1402 1655 Viscosity index Shear rate 10/500 1.01 2.00 2.18 2.42 2.52 Shear rate 10/1000 1.00 2.17 2.41 2.73 2.85

TABLE-US-00007 TABLE 6C Gabrosa T 4000 C in the range of 0.1 to 2.0 w % Composition: 1 2 3 4 5 HBS 245 g 245 g 245 g 245 g 245 g GABROSA T 4000 C 0.25 g 1 g 2.5 g 5 g Water 345 g 345 g 345 g 345 g 345 g Properties: Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C., 2 h after preparation 570 650 1190 2900 8800 Refraction [%] 41.3 42.3 42.5 42.2 42.2 pH 5.4 5.2 5.2 5.3 5.4 Wet Tack 60 m [5.3] 2 4 7 18 27 Setting time 60 m [0, . . .] Time till 40 cJ [s] 16 16.5 14.5 13.5 10 Viscosity-stability Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C. After 2 hours 515 650 1190 2900 8800 After 4 weeks 585 795 1515 3740 10780 Viscosity-stability index [4 weeks/2 hours] 1.14 1.22 1.27 1.29 1.23 Rheological behavior Newto- Shear- Shear- Shear- Shear- nian thinning thinning thinning thinning Physica viscosity [mPa .Math. s] Interval 0.1-1000 Shear rate 10 s1 443 522 1244 1986 3910 Shear rate 500 s1 440 448 543 700 943 Shear rate 1000 s1 441 439 505 627 811 Viscosity index Shear rate 10/500 1.01 1.16 2.29 2.84 4.15 Shear rate 10/1000 1.00 1.19 2.46 3.17 4.82

TABLE-US-00008 TABLE 6D Finnfix 2 in the range of 7.5 to 16.9 w % Composition: 1 2 3 4 5 HBS 245 g 245 g 245 g 245 g 245 g FINNFIX 2 20 g 30 g 40 g 50 g Water 345 g 345 g 345 g 345 g 345 g Properties: Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C., 2 h after preparation 570 2175 4030 7180 12300 Refraction [%] 41.3 43.6 44.4 45.1 45.8 pH 5.4 5.5 5.6 5.6 5.6 Wet Tack 60 m [5.3] 2 4 4 5 6 Setting time 60 m [0, . . .] Time till 40 cJ [s] 16 15 16 16 16 Viscosity-stability Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C. After 2 hours 515 2175 4030 7180 12300 After 4 weeks 585 2270 4280 7870 14600 Viscosity-stability 1.14 1.04 1.06 1.10 1.19 index [4 weeks/2 hours] Rheological behavior Newto- Shear- Shear- Shear- Shear- nian thinning thinning thinning thinning Physica viscosity [mPa .Math. s] Interval 0.1-1000 Shear rate 10 s1 443 1656 2777 4768 7948 Shear rate 500 s1 440 1296 1998 2910 4355 Shear rate 1000 s1 441 1210 n.a. n.a. n.a. Viscosity index Shear rate 10/500 1.01 1.28 1.39 1.64 1.83 Shear rate 10/1000 1.00 1.37 n.a. n.a. n.a.

TABLE-US-00009 TABLE 6E Additional example showing the impact of the type of CM polysaccharide used (Brookfield viscosity between 2000-3000 mPa .Math. s). Composition: 1 2 3 4 HBS 245 g 245 g 245 g 245 g GABROSA T 4000 C 2.5 g SOLVITOSE C5 5 g QUICKSOLAN SPR 10 g FINNFIX 2 20 g Water 345 g 345 g 345 g 345 g Properties: Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C., 2 h after preparation 2900 2315 2615 2175 Refraction [%] 42.2 42.3 43.0 43.6 pH 5.3 5.7 5.6 5.5 Wet Tack 60 m [5.3] 18 4 6 4 Setting time 60 m [0, . . .] Time till 40 cJ [s] 13.5 16.5 14 15 Viscosity-stability Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C. After 2 hours 2900 2315 2615 2175 After 4 weeks 3740 2425 2580 2270 Viscosity-stability index [4 weeks/2 hours] 1.29 1.05 0.99 1.04 Rheological behavior Shear- Shear- Shear- Shear- thinning thinning thinning thinning Physical viscosity [mPa .Math. s] Interval 0.1-1000 Shear rate 10 s1 1986 1834 1866 1656 Shear rate 500 s1 700 1096 932 1296 Shear rate 1000 s1 627 1002 860 1210 Viscosity index Shear rate 10/500 2.84 1.67 2.00 1.28 Shear rate 10/1000 3.17 1.83 2.17 1.37

Example 7

Advantage of HBS Over Other Starch Derivatives

[0072] This examples demonstrates the surprising advantages of a composition of the invention comprising HBS and CM polysaccharide over known aqueous starch-based adhesives comprising carboxymethylcellulose. U.S. pat. No. 4,272,295 relates to starch based adhesives, for example, for use in the manufacture of corrugated and laminated paper and board, and in particular to starch based adhesives requiring low heat-energy consumption for forming satisfactory bonds.

[0073] Example 1 of U.S. Pat. No. 4,272,295 discloses a lyophilic colloid consisting of 90% by weight of fully gelatinized starch and 10% by weight of carboxymethyl cellulose. The data herein below show that replacement of the fully gelatinized starch with highly branched starch unexpectedly provides an adhesive with completely different properties and an improved rheological profile.

Methods:

[0074] 1. In a glass beaker of 400 mL 175.7 gram of water and 2.0 gram of caustic soda were added. The beaker was put in a water bath of 55 C. [0075] 2. Whilst stirring with 1000 rpm 8.33 gram of a lyophilic colloid consisting of 90% by weight of either fully gelatinised starch (Passeli WA 4; comparative example) or HBS (example of the invention) and 10% by weight of carboxymethyl cellulose (Gabrosa P 400 G) was dispersed into the solution. The mix was stirred for 10 minutes in water bath of 55 C. [0076] 3. 133.3 grams of commercial wheat starch was slurried in 200 grams of water and added whilst stirring with 1000 rpm to the colloid solution. [0077] 4. The mixture was heated in the water bath of 55 C. until viscosity increased to 28 seconds (STEIN HALL CUP). [0078] 5. Immediately the mixture was taken out of the water bath and at room temperature 0.83 gram of Boric Acid was added and after 1 minute mixing 0.33 gram of sodium silicate (38 DEGBe) was added.

[0079] After 1 day storage at 20 C. the Brookfield viscosity, pH, dry solids were determined and the rheological profile characterized with a flow curve, LAOS (Large Amplitude Oscillatory Shear) and an Oscillation Frequency Sweep.

Analytic Procedures:

[0080] RheologyA flow curve of an adhesive is recorded by a Haake Mars III Rheometer. Measure geometry: C60/2 Ti L L10 010. gap: 0.100 mm, 2.5 ml adhesive, temperature: 20 C.

[0081] Profile: [0082] 1. CR; 10.00 1/s; t 30.00 s; #30 [0083] 2. CR; 0.000 1/s; t 3.00 s; #10; [0084] 3. Reset normal force [0085] 4. CR; 1.000 1/s-1000. 1/s log; t 160.00 s; #16 [0086] 5. CR; 1000. 1/s-1.000 1/s log; t 160.00 s; #16

[0087] RheologyA LAOS of an adhesive is recorded by a Haake Mars III Rheometer. Measure geometry: C60/2 Ti L L10 010. gap: 0.100 mm, 2.5 ml adhesive, temperature: 20 C.

[0088] Profile: [0089] 1. CS; 0.000 Pa; t<300.00 s; [0090] 2. CR; 0.000 1/s; t 3.00 s; #10 [0091] 3. Reset normal force [0092] 4. CD; 0.01000-100.0- log; f 1.000 Hz; t - - -; #21 [0093] 5. CD; 0.01000-100.0- log; f 1.000 Hz; t - - -; #21

[0094] RheologyAn oscillation frequency sweep of an adhesive is recorded by a Haake Mars III Rheometer. Measure geometry: C60/2 Ti L L10 010. gap: 0.100 mm, 2.5 ml adhesive, temperature: 20 C.

[0095] Profile: [0096] 1. CS; 0.000 Pa; t<300.00 s [0097] 2. CR; 0.000 1/s; t 3.00 s; #10 [0098] 3. CD-AS; 0.04000-; 10.00 Hz 1.000 Hz log; t - - -; #6 [0099] 4. CD-AS; 0.04000-; 1.000 Hz 0.01000 Hz log; t - - -; #3

Results

[0100] Table 7 and FIGS. 1, 2 and 3 show that the use of HBS instead of fully gelatinized starch in a lyophilic colloid results in an adhesive with a yielding behaviour which acts like a gel instead of a polymeric solution. A gel-like behaviour is very desirable for adhering two substrates (e.g. at laminating) because due to this behaviour delamination during drying of the adhesive will be avoided or minimized. In contrast, the adhesive with the polymeric solution behaviour continues to flow and will not withstand low load during drying resulting in delamination.

TABLE-US-00010 TABLE 7 Composition Comp. example Invention Starch in lyophilic colloid Fully gelatinized Highly branched starch (FGS) Starch (HBS) Properties: Brookfield viscosity [mPa .Math. s] 20 rpm, 20 C. 1 day after preparation 18350 9100 pH 12.1 12.0 Dry solids [%] 22.6 22.7 Rheology HAAKE MARS Flowcurve [mPa .Math. s] Interval 1-1000 Shear rate 10 s1 5300 4850 Shear rate 1000 s1 233 132 Viscosity index Shear rate 10/1000 22.7 36.7 LAOS .sup.1 Type I Type III .sup.1 Reference: Large Amplitude oscillatory shear behavior of complex fluids investigated by a network model: a guideline for classification. Hoon Goo Sim, Kyung Hyun Ahn, Seung Jong Lee. Journal of Non-Newtonian Fluid Mechanics, 112 (2003), 237-250

[0101] FIGS. 1, 2 and 3 illustrate the rheological properties of the comparative example (Composition 1; FGS) and the example of the invention (Composition 2; HBS).

[0102] As is shown in FIG. 1, with the use of HBS (almost) no change in normal stress is observed. In contrast, with Composition 1 a positive normal stress builds up which is known to be undesirable and promotes uneven application of the adhesive due to the formation of ribs. (Reference: Effects of non-newtonian fluids on the ribbing instability. L. Pauchard, F. Varela Lopez, M. Rosen, C. Allain, P. Perrot, M. Rabaud 3rd European Symposium on Advances in Coating and Drying of Thin Films. Erlangen 1999). It was also observed that with the use of HBS an abrupt decrease of the viscosity is observed near a stress of 60 Pascal (yielding behaviour) whereas a composition according to U.S. Pat. No. 4,272,295 shows a gradual decrease of the viscosity (data not shown).

[0103] FIG. 2 shows the results of the Large Amplitude Oscillatory Shear (LAOS) analysis, which is useful to characterize nonlinear properties of complex fluids. LAOS characterization is considered as a rigorous test for rheological models and quality control. It was found that comparative Composition 1 with fully gelatinized starch is classified' as a type I, strain thinning. Type I are polymer like solutions and this is in correspondence with the observed Normal stress development. Composition 2 with HBS however is classified .sup.1 as type III, weak strain overshoot. Type III is not as common as type I behaviour, and a Type III response is typical for complex fluids which have a temporary network. Hence, the LAOS analysis also demonstrates a major effect of using HBS on the rheological properties of the colloid. In particular, the Type III behaviour is especially desirable for application of the colloid in (high speed) machinery in the paper industry.

[0104] FIG. 3 shows the Oscillation Frequency Sweep. Formulation 2 behaves like a typical gel; the elastic component (G) is almost frequency independent and has a finite magnitude. In contrast, Composition 1 behaves like a polymer like solution; at (very) low frequencies the elastic component vanishes and it will flow like a liquid.

[0105] In conclusion, all three characterizations show a distinct difference in rheological behaviour between Compositions 1 and 2. Composition 1 flows like a polymer solution, whereas Composition 2 shows a yielding behaviour and acts like a gel.

[0106] One skilled in the art will recognize and appreciate that a gel-like behaviour is very desirable for adhering two substrates (e.g. at laminating) because delamination will be avoided or minimized due to this behaviour.