Starch-based glue composition

Abstract

A highly homogeneous starch-based glue composition is obtained by enzymatic modification of the starch with a branching enzyme which is supplied in an enzymatically modified starch with high long-term stability. The starch has a viscosity stability index SI of less than or equal to 1.3, calculated by the quotient of viscosity after 14 days and by viscosity after 2 hours after preparation of the starch. The starch is suitable for liquid storage, which is stable in the long-term, of a ready-to-use paste with a high bonding strength.

Claims

1. A glue composition, comprising: an enzymatically branched starch having a viscosity stability index SI of less than or equal to 1.3, calculated by a quotient from viscosity after 14 days and the viscosity after 2 hours after preparation of the glue composition, wherein said starch having a mean molecular weight Mw (weight average), measured by light scattering, of 60 kDa to 3000 kDa; and the glue composition having a viscosity of at least 250 mPas at 22.5 C. and the starch content in the composition is at least 25% (% by weight).

2. The glue composition according to claim 1, wherein said starch has a mean degree of branching of alpha-1,6 branchings of 4 to 12%.

3. The glue composition according to claim 1, wherein said starch has a DE value of 1 at most.

4. The glue composition according to claim 1, wherein said starch is highly homogeneous, with a polydispersity index PDI between 1 and 5.

5. The glue composition according to claim 1, wherein said starch is selected from the group consisting of waxy maize starch, maize starch, potato starch, amylopectin potato starch, rice starch, wheat starch, manihot starch, and sago starch.

6. The glue composition according to claim 1, wherein a proportion of said starch makes up at least 50% of an entire starch fraction of the glue composition.

7. The glue composition according to claim 1, wherein said starch is modified by a branching enzyme which increases a degree of branching compared to unmodified starch and/or lowers polydispersity compared to unmodified starch.

8. The glue composition according to claim 7, wherein said starch branching enzyme is a branching enzyme of Rhodothermus sp.

9. The glue composition according to claim 1, wherein the glue composition is substantially free from low-molecular oligosaccharides with a degree of polymerization of less than 3.

10. The glue composition according to claim 9, wherein a proportion of the low-molecular oligosaccharides is less than 5% by weight of a starch mass.

11. The glue composition according to claim 7, wherein said starch branching enzyme is selected from the group consisting of 1,4--D-glucan and 1,4--D-glucan 6--D-(1,4--D-glucano)-transferase (E.C. 2.4.1.18).

12. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of at least 70 kDa.

13. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of at least 80 kDa.

14. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of at least 90 kDa.

15. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of up to 2500 kDa.

16. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of up to 2000 kDa.

17. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of up to 1500 kDa.

18. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of up to 1000 kDa.

19. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of up to 800 kDa.

20. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of up to 600 kDa.

21. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of up to 400 kDa.

22. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of up to 200 kDa.

23. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of up to 150 kDa.

24. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of up to 140 kDa.

25. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of up to 135 kDa.

26. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of up to 130 kDa.

27. The glue composition according to claim 1, wherein said starch has a mean molecular weight Mw (weight average), measured by light scattering of up to 125 kDa.

28. The glue composition according to claim 1, wherein the glue composition has a viscosity of least 300 mPas at 22.5 C. when said starch content in the composition is at least 25%.

29. The glue composition according to claim 1, wherein the glue composition has a viscosity of least 400 mPas at 22.5 C. when said starch content in the composition is at least 25%.

30. The glue composition according to claim 1, wherein the glue composition has a viscosity of least 500 mPas at 22.5 C. when said starch content in the composition is at least 25%.

31. The glue composition according to claim 1, wherein the glue composition has a viscosity of least 1200 mPas at 22.5 C. when said starch content in the composition is at least 25%.

32. The glue composition according to claim 1, wherein the glue composition has a viscosity of least 1500 mPas at 22.5 C. determined using Brookfield testing procedures.

33. A method of using glue, which comprises the steps of: providing a glue composition according to claim 1, the glue composition functioning as an adhesion promoter; and using the glue composition as a gluing agent or a laminating agent for at least one of paper products, cardboard products, and displays made from paper or cardboard.

34. A glued product, comprising: a glue composition according to claim 1, said glue composition functioning as an adhesion promoter; and a product selected from the group consisting of paper formed from at least two layers and cardboard formed from at least two layers, wherein at least one of said two layers is bonded by said glue composition and at least one of said two layers has a printed or printable flat surface, on a side of said layer opposite a side to be glued.

35. A method for gluing a product, which comprises the steps of: providing a glue composition according to claim 1, the glue composition functioning as an adhesion promoter; and applying the glue composition onto a side of a product to be glued.

36. A method for preparing a glue composition according to claim 1 by enzymatic modification, which comprises the step of: contacting a starting starch with a branching enzyme in an amount with an activity of 50 BEU to 20,000 BEU per gram of the starting starch.

37. The method according to claim 36, which further comprises providing Rhodothermus sp. as the branching enzyme in an amount with an activity of 80 BEU to 10,000 BEU per gram of the starting starch.

38. A method for preparing a glue composition according to claim 1, which comprises the step of: contacting the starch with a branching enzyme and in that a mean molar mass of a desired modified starch product is controlled by a starting amount of the branching enzyme per starting starch (amount by weight).

39. The method according to claim 38, which further comprises providing Rhodothermus sp. as the branching enzyme.

40. A method for preparing a glue composition according to claim 1, which comprises the steps of: modifying enzymatically the starch; and mixing the starch with an aqueous solvent.

41. The method according to claim 40, which further comprises mixing in a filler selected from the group consisting of a silicate, a salt, buffer components, acids, bases and a biocide.

42. A starch-based glue composition, comprising: an enzymatically branched starch obtainable by contacting a starting starch with a branching enzyme with an activity of 50 BEU to 20,000 BEU of starting starch, whereby the glue composition having a viscosity of at least 250 m Pas at 22.5 C. and the starch content in the composition is at least 25% (% by weight).

43. The starch-based glue composition according to claim 42, wherein said branching enzyme is of Rhodothermus sp. with an activity of 80 BEU to 10,000 BEU per gram of the starting starch.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is a graph showing elugrams of different starches: preferred starch in accordance with the invention after branching and commercial reference products (starches shown in accordance with Table 1: MD1, MD2, RD1, EMS1-5);

(2) FIG. 2 is a graph showing a molar mass distribution of some starches in accordance with calculation by light scattering (starches shown: MD1, MD2, RD1, EMS2, EMS3);

(3) FIG. 3 is a graph showing the bond strength measurement of 50% starch solutions after 24 hours with different layer thicknesses (starches shown: MD1, MD2, RD1, EMS3; EMS3_1 is a second batch prepared in accordance with the model of EMS3); and

(4) FIG. 4 is a graph showing a mass spectra of the starches after glucoamylase degradation (starches shown: MD1, EMS3, EMS4; EMS4(d) corresponds to the starch EMS4, the product of which was purified further by dialysis).

DETAILED DESCRIPTION OF THE INVENTION

Example 1

Preparation of a Highly-Branched Starch (Ems3)

(5) Materials:

(6) a. waxy maize starch Maisita 21.007;

(7) b. branching enzyme NS28067, (activity of 50,000 BEU/g solution);

(8) c. sodium hydroxide solution;

(9) d. hydrochloric acid; and

(10) e. filtering aid.

(11) 100 g of waxy maize starch (dry substance) were mixed in with distilled water to form a 10% slurry. This slurry was gelatinized (95 C.) with constant stirring (propeller stirrer). The starch began to gelatinized from a temperature of approximately 70 to 75 C. The temperature of 95 C. was maintained for 1 hour to ensure complete starch digestion. After cooling to 75 C., the pH value of the paste was set to pH 6 (0.1 N hydrochloric acid or 0.1 N sodium hydroxide solution). The enzyme was then added (1,000 BEU/g of starch). In order to obtain other products, 20 BEU/g to 1,000,000 BEU/g were alternatively used. The moment of enzyme addition is defined as the start of the reaction. The initial relatively thick paste became gradually runny after addition of the enzyme. The reaction mixture was held constantly at a temperature of 75 C. and the reaction was terminated after 20 hours. For this purpose, the mixture was brought approximately to pH 3 using hydrochloric acid and was boiled for 30 mins. This raw product was then purified by filtration and dried, the dried product was ground. A liquid starch was produced from part of the purified raw product. This occurs by evaporating water until reaching the desired product concentration.

Example 2

Preparation of the Paste

(12) Distilled water (250 g) was introduced into a 400 ml beaker glass (high type) and, for 40%, 100 g in dry substance (i.DS) were weighed in, and for 50% 125 g starch i.DS were weighed in. Stirring occurred using a Heidolph stirrer and a toothed-disc stirrer (diameter 4 cm). The sample was interspersed quickly, without clump formation where possible, at 1000 rpm and stirred for 10 min. In order to ensure the biological stability of the glues prepared, each glue was mixed with 1% biocide solution based on the starch.

(13) The first viscosity measurements were taken directly after the stirringin process. The glues were then filled into screw-cap jars for storage and stored at constant temperature.

Example 3

Determination of Viscosity

(14) The starch pastes prepared by the above-described method or a liquid starch may be used directly to determine viscosity. Viscosity was calculated with the aid of a Brookfield-RV viscosimeter (DVII+Viscosimeter) at 22.5 C. and at a rotational speed of 100 rpm of spindle 4.

(15) The first measurement was taken directly after preparation of the paste, further measurements being taken after 2 hr, 24 hr, 7 days and 14 days to assess viscosity stability. For this purpose, the stability index value (SI) was used, that is to say the quotient from viscosity after 14 days and 2 hr. Values around 1 demonstrate good viscosity stability: the higher the value, the more pronounced the subsequent thickening. Set samples were given with an SI value greater than 10.

Example 4

Determination of Bond Strength

(16) A hand-held doctor blade was placed on the outer face of a bag paper (SE BL 90 g/m.sup.2) with the desired layer thickness (30, 60 or 120 m), filled with paste (preparation see above) and drawn over the paper. Thereupon, a second paper strip was placed on via its inner paper face. The combined paper was smoothed using the palm of a hand and then smoothed again in a similar manner on the rear face. The bonded paper strips were now slowly drawn away from one another bit by bit by hand (slightly jerkily) until a complete fiber tear (over the entire width of the bond) was established. This period of time is the bonding speed and is given in seconds, wherein a mean value from at least 3 measurements was provided. If, after 150 seconds, still no bonding could be established, the measurement was terminated.

Example 5

Determination of the Molar Mass Distribution

(17) Molar mass distribution was determined by size-exclusion chromatography (SEC, UltiMate 3000, Dionex), in which the molecules are separated in accordance with their hydrodynamic volume over the corresponding column system (Suprema 30.000 +1000 +100 ; 20 m particle size; PSS Mainz).

(18) The scattered light intensity is also proportional to the molar mass in addition to concentration and breaking increment dn/dc. The molar masses (number average Mn and weight average Mw) at the known dn/dc can thus be determined by the combination of a MALLS detector (Multi Angle Laser Light Scattering, measures the scattered light intensity at a number of angles; SLD7000, PSS Mainz) and an RI detector (Refractive Index, determines the concentration, RI-101, Shodex). The polydispersity (breadth of the distribution, PDI=Mw/Mn) and the average degree of polymerization (DPn=Mn/162) were calculated from these values.

(19) For conventional SEC, the system was calibrated using a Pullulan standard set (180-788000 g/mol, Polymer Laboratories).

(20) For digestion, starch was stirred at 2.5% into deionized water and brought to a pH level of pH 7 using hydrochloric acid (1N) or NaOH solution (1N). This aqueous solution was diluted with DMSO at a ratio of 1:1.5 and digested with stirring for 30 min at 100 C. The solution obtained must be homogeneously clear. After cooling, the samples were filtered over a glass fiber filter and are then ready for measurement.

(21) The following HPLC parameters were used for the measurement:

(22) eluent: 0.2 M NaNO.sub.3 solution (with 0.2 mg NaN3)

(23) flow: 0.7 ml/min

(24) injection volume: 80 l

(25) column temp.: 70 C.

(26) running time: 70 min.

Example 6

Determination of the Degree of Branching

(27) In order to determine the degree of branching by means of 1H-NMR spectroscopy, the samples were dissolved in D20 with 1% NaOH and measured at 70 C. In order to determine the degree of branching, the signals were required at 5.6 ppm (1) and 5.3 ppm (2) (solvent D20). Integration occurred via a previous base-line correction. The ratio in percent was calculated as follows:
[integral(2)*100]/[integral(1)+(2)]

(28) The measurements were taken using a Bruker ARX 250 (Bruker ARX 250, 250 MHz 1H-NMR, solvent D20, 70 C.).

Example 7

Preparation of Glue for Gluing Display Cardboard

(29) Formulation: Preparation of Glue for a Roller Application System:

(30) 20 kg 50% liquid starch or stirred-in starch paste of EMS3,

(31) 10 kg of a kaoline suspension (FSG=68%),

(32) 150 g biocide (for example petrocide), and

(33) 400 g 2% sodium hydroxide solution.

(34) The liquid starch was introduced into a container, a kaoline suspension was added, with stirring, and the mixture was stirred for 30 min. The pH value was brought to 9 using sodium hydroxide solution and, for the purposes of storage, a biocide was stirred in.

(35) The glue obtained had the following specifications:

(36) solid content: 56%,

(37) Brookfield viscosity at 25 C. after 24 h: 3650 mPas,

(38) pH value: 9.0, and

(39) bond strength on cardboard (60 m hand-held doctor blade): 24 sec.

(40) The laminating glue thus prepared has the following technical properties:

(41) 1. Excellent adhesion

(42) 2. High bond strength

(43) 3. Low tendency to spatter

(44) 4. High initial tack

(45) 5. Ready to use glue with excellent viscosity stability

(46) 6. Optimal gluing at the edges

(47) 7. No drawbacks during subsequent punching

(48) 8. Very good shear strength.

(49) The following table shows the comparison of the different glues based on different raw materials:

(50) TABLE-US-00001 Dispersion glue Maltodextrin glue EMS glue Solid content [%] 55 55 56 Viscosity [mPas]* 2300 Too thick, gelled 1650 Bond strength [s]** 26 24 *Brookfield viscosity at room temperature after 24 h **Bond strength on cardboard (60 m hand-held doctor blade)

Example 8

Calculation of the Glucoamylase-Resistant Proportion by Enzymatic Degradation with Glucoamylase

(51) The glycoamylase-resistant proportion was prepared as follows:

(52) Glucoamylase was weighed in (final concentration 10 units/ml=1.3 mg/5 ml) and taken up in 5 ml of water (deionised). 100 mg of starch were added and the enzyme reaction was carried out for 16 h at 40 C. (with stirring in the digestion block). The reaction was stopped by heat treatment for 10 min at 100 C. (in a water bath). Undissolved parts were centrifuged off (10 min, 1500 rpm), wherein the liquid was processed further and the precipitate was discarded. 10 times the amount of ethanol was added, in portions, to the liquid. After centrifugation (30 min, 4000 rpm), the liquid was discarded. The precipitate was left to dry and then taken up in 1 ml of water (deionized). Glucoamylase was added again (final concentration 50 units/ml). The second reaction took place for 1 h at 40 C. A heat treatment was then carried out for 10 min at 100 C. (in a water bath). Undissolved parts were centrifuged off (10 min, 1500 rpm). The precipitate was discarded and the liquid was processed further. 10 times the amount of ethanol was added, in portions, to the liquid and the liquid was discarded after centrifugation (30 min, 4000 rpm). This end product was called a glucoamylase-resistant fraction. A product degraded in accordance with the invention (EMS4 (d)) was additionally purified by dialysis before the glucoamylase treatment. Compared to conventional starches (maltodextrin with DE6; also degraded by glucoamylase), an analysis was carried out by means of MALDI-TOF (matrix: trihydroxyacetophenone). The measurement by mass spectrometry was carried out on an Axima TOF2, Shimadzu Biotech Kratos Analytical, Manchester, UK with calibration with single- and double-protonated bovine insulin (+/1 Da). The results of the measurement in the positive ion mode are shown in FIG. 4 and Table 9.

Example 9

Results

(53) The following starch properties and parameters were ascertained on the basis of the above-described methods:

(54) TABLE-US-00002 TABLE 1 Starch comparative products: Abbre- viation Description Raw material MD1 Maltodextrin DE6 Waxy maize starch MD2 Maltodextrin DE15 Maize starch RD1 Roast dextrin Potato starch EMS1 Modification with 20 BEU/g starch Waxy maize starch EMS2 Modification with 100 BEU/g starch Waxy maize starch EMS3 Modification with 1,000 BEU/g starch Waxy maize starch EMS4 Modification with 10,000 BEU/g starch Waxy maize starch EMS5 Modification with 100,000 BEU/g starch Waxy maize starch WMS Native waxy maize starch Waxy maize starch

(55) MD1, MD2, RD1 and WMS are unmodified comparative examples within the scope of the invention. In accordance with the invention, enzymatically modified starches (EMS1-5) were modified in this case with branching enzyme of Rhodothermus obamensis. As shown below, different products were obtained depending on the amount of enzyme used. An extension of the reaction time led to no further change to the molar mass. Of course, less modified starches may also be obtained by stopping the reaction sooner. Particularly high bond strength and/or extraordinary long-term stability were demonstrated in particular in samples EMS2, EMS3 and EMS4.

(56) TABLE-US-00003 TABLE 2 Calculation of the mean molar masses, polydispersity and average degree of polymerization of the starches via conventional SEC: Mw Mn PDI DPn DPw MD 1 27000 2900 9.3 18 167 MD 2 4700 1500 3.1 9 29 RD 1 7660 24 3.2 15 47 EMS 1 1200000 64000 18.8 395 7407 EMS 2 87000 19000 4.6 117 537 EMS 3 43000 13400 3.2 83 265 EMS 4 31000 14700 2.1 91 191 EMS 5 18500 8100 2.3 50 114

(57) Mw: mean molar mass (weight average); Mn: mean molar mass (number average); PDI: polydispersion index (Mw:Mn); Dpn degree of polymerization according to the number average; Dpw degree of polymerization according to the weight average;

(58) TABLE-US-00004 TABLE 3 Calculation of the mean molar masses, polydispersity and average degree of polymerization of the starches via light scattering: Mw Mn PDI DPn DPw MD 1 61200 1800 34 11 378 MD 2 6200 2700 2.3 17 38 RD 1 8700 4500 1.9 28 54 EMS 1 5506000 719000 7.7 4438 33988 EMS 2 234000 66500 3.5 410 1444 EMS 3 104000 67000 1.6 414 642 EMS 4 90700 54000 1.7 333 560 EMS 5 35000 19700 1.8 122 216 WMS >50000000 >5000000 approx. 10 >38000 >300000

(59) Tables 2 and 3 show the shift of the mean molar mass of the starch molecules and the differences depending on measurement method. SEC elugrams and the molar mass distribution by light scattering measurement are also shown in FIGS. 1 and 2. The homogeneous composition of the EMS according to the invention can be clearly seen from this data and yields a narrow, dominant peak.

(60) TABLE-US-00005 TABLE 4 Oligosaccharide proportion of the starch: Glucose Maltose Maltotriose Maltotetraose Maltopentaose Maltohexaose [%] [%] [%] [%] (%) (%) MD1 0.05 1.4 2.2 1.7 1.3 1.3 MD2 2.9 3.3 3.8 3.8 2.8 1.8 RD1 0 0.1 1.4 1.3 0 0 EMS1 0 0.1 <0.1 <0.1 0 0 EMS2 0 0.1 <0.1 <0.1 0 0 EMS3 0.1 0.5 <0.1 <0.1 0 0 EMS4 0.0 1.1 0.8 0.5 0.4 0.4 EMS5 0 0 2 0.9 0.9 0.3 WMS 0 0 0 0

(61) Table 4 shows that hardly any low-molecular oligosaccharides accumulate in the case of enzymatic modification according to the invention of the starting starch.

(62) TABLE-US-00006 TABLE 5 Product parameters: DE value and degree of branching: DE value Degree of branching NMR [%] MD1 6.4 5.1 MD2 13.7 6.1 RD1 6.6 ~7 EMS1 <0.1 4.4 EMS2 <0.1 5.2 EMS3 <0.1 7 to 8 EMS4 <0.1 10.9 EMS5 <0.1 12 WMS <0.1 4.3

(63) According to Table 5, the increasing branching is demonstrated by the enzymatic modification while the DE value remains low. These parameters show a considerable structural difference to conventional industrial starches.

(64) TABLE-US-00007 TABLE 8a Calculation of viscosity and bond strength: BF viscosity Bond 40% 100 rpm strength 40% 2 h 14 d SI 30 m 60 m 120 m MD1 148 356 2.4 58 57 101 MD2 66 66 1.0 No bonding RD1 641 655 1 100 105 >150 EMS1 8300 n.m. >10 14 16 41 EMS2 1048 812 0.8 24 33 67 EMS3 338 369 1.1 45 44 94 EMS4 n.d. n.d. n.d. n.d. n.d. n.d. EMS5 n.d. n.d. n.d. n.d. n.d. n.d. n.d.not determined owing to insufficient amount of material n.m.not measurable owing to excessively high viscosity

(65) TABLE-US-00008 TABLE 8b Calculation of viscosity and bond strength: BF viscosity Bond 50% 100 rpm strength 50% 2 h 14 d SI 30 m 60 m 120 m MD1 550 n.m. >10 22 38 98 MD2 138 197 1.4 76 115 149 RD1 3570 3576 1 49 60 >150 EMS1 n.m. n.m. n.m. n.m. n.m. n.m. EMS2 7080 n.m. >10 17 26 61 EMS3 1770 1480 0.8 34 26 66 EMS4 358 354 1 104 129 >150 EMS5 52 56 1.1 No bonding

(66) Tables 8a and 8b shows the advantageous stability and bonding properties of the EMS starches, in particular of EMS 2, EMS3 and EMS4. These starches exhibited good bonding properties at all measured concentrations and layer thicknesses. While EMS3 and EMS4 exhibited optimal stability and bonding properties in 50% solutions, the optimum was achieved for EMS2 in a 40% composition. Further bonding strength calculations of 50% starch solutions after 24 hours are shown in FIG. 3. The stability index SI can be seen from the quotient of the viscosity calculation after 14 days by the viscosity calculation after 2 hours after preparation of the aqueous starch paste. The first viscosity measurement was taken after 2 hours in order to ensure constant conditions, in particular a constant measurement temperature.

(67) TABLE-US-00009 TABLE 9 m/z numbers of the peaks of the MALDI-TOF mass spectra (FIG. 4) of the glycoamylase degradation products according to Example 8: MD1 EMS4 EMS3 EMS4 (d) 3433 3434 3434 3434 3595 3596 3595 3595 3757 3759 3757 3757 3919 3921 3920 3920 4082 4083 4083 4083 4244 4245 4244 4244 4407 4407 4407 4407 4568 4570 4569 4569 4730 4732 4731 4731 4893 4895 4894 4894

(68) According to these results, there is no noticeable difference in the product structure, derived from the m/z distribution, in the glucoamylase-resistant starch fraction between conventional maltodextrin (MD1) and the enzymatically modified starches. This means that a similar residue remains after treatment with glucoamylase.