METHOD FOR APPLYING STARCH TO A PAPER OR PAPERBOARD WEB
20220243401 · 2022-08-04
Assignee
Inventors
US classification
- 1/1
Cpc classification
C09D103/02
CHEMISTRY; METALLURGY
D21H19/12
TEXTILES; PAPER
C09J103/02
CHEMISTRY; METALLURGY
International classification
D21H19/12
TEXTILES; PAPER
Abstract
The invention relates to a method for applying starch to a paper or paperboard web, the method comprising the steps of: providing an aqueous suspension comprising starch particles and at least 1 wt %, based on the dry solid content of the suspension, of an amphiphilic polymer, creating a foam of the aqueous suspension, and applying the foam to the paper or paperboard web. The invention further relates to a paper or paper board product obtained by the method.
Claims
1. A method for applying starch to a paper or paperboard web, the method comprising the steps of: providing an aqueous suspension comprising starch particles and at least 1 wt %, based on a dry solid content of the aqueous suspension, of an amphiphilic polymer, creating a foam from the aqueous suspension, and applying the foam to the paper or paperboard web.
2. The method according to claim 1, wherein the amphiphilic polymer is selected from a group consisting of: ethyl hydroxyethyl cellulose, hydrophobic modified ethylhydroxyethyl cellulose, hydroxyethyl cellulose, hydrophobic modified hydroxyethyl cellulose, hydroxyproylated cellulose, hydrophobic modified carboxymethyl cellulose, hydrophobic modified starch, hydroxypropylated starch, and combinations or mixtures thereof.
3. The method according to claim 1, wherein the aqueous suspension comprises the amphiphilic polymer in an amount in a range from ≥1 wt % to ≤10 wt %, based on the dry solid content of the suspension.
4. The method according to claim 1, wherein the aqueous suspension comprises the starch particles in an amount in a range from ≥30 wt % to ≤99 wt %, based on the dry solid content of the suspension.
5. The method according to claim 1, wherein the starch particles have a median particle diameter in a range from ≥0.5 μm to ≤200 μm.
6. The method according to claim 1, wherein the aqueous suspension further comprises microfibrillated cellulose.
7. The method according to claim 1, wherein a solid content of the foamed aqueous suspension is ≥5 wt %, based on a total weight of 100 wt % of the foamed suspension.
8. The method according to claim 1, wherein the foam is applied to the paper or paperboard web by a non-impact coating technology selected from a spray coating, a curtain coating, or a foam coating.
9. The method according to claim 1, wherein the foam is applied to a paper or paperboard web having a solid content of less than 50 wt %, based on a total weight of 100 wt % of the paper or paperboard web.
10. The method according to claim 1, wherein the method is a method of surface sizing a paper or paperboard web.
11. The method according to claim 1, wherein the method is a method of dosing starch between plies in a production of a multiply paperboard.
12. A paper or paper board product obtained by the method of claim 1.
13. The paper or paper board product according to claim 12, wherein the paper or paper board product comprises at least one starch layer having a coat weight in a range from ≥0.1 g/m.sup.2 to ≤30 g/m.sup.2.
14. The paper or paperboard product according to claim 12, wherein the paperboard product is a multiply paperboard.
15. The paper or paperboard product according to claim 12, wherein the paperboard product is a surface-sized paper or paperboard.
Description
EXPERIMENTAL MATERIALS AND METHODS
[0047] The materials used for generating the aqueous coating suspensions were uncooked starch particles (barley, Altia Plc, Finland), hydrophobically modified hydroxyethyl cellulose (EHEC, Bermocoll EHM200, AkzoNobel Chemicals AG, Sweden), and Sodium dodecyl sulfate (SDS, Merck KGaA, Germany). The particle size distribution (by volume) of the uncooked starch particles used is shown in Table 1. The particle size was measured at pH around 7 and at a temperature of 23° C. using a Mastersizer 2000 particle size analyser (Malvern, UK).
TABLE-US-00001 TABLE 1 D10 D50 D90 Wet sample 10.9 17.4 26.4 (30 min-1 h 30 min) Stdev 0.1 0.0 0.1
[0048] Cupforma classic 210 gsm was used as substrate. The starch was mixed as received without further treatment into cold water. The foam was generated with A Rollmix BGR 13 (Rollmac, Italy). Coating of the substrate was conducted with a bench coater (rod).
[0049] pH and viscosity of the aqueous suspensions were measured before generating the foam. Viscosity of the foam was measured with a Brookfield digital viscometer (Model DVII+, Brookfield Engineering Laboratories, Inc.) using spindle #6 and speeds of 10 and 50 rpm at the temperatures given in the tables below. For the measurement of the viscosity of the aqueous suspensions spindle #1 and 50 rpm was used, except sample 6, where 10 rpm were used. Solid content was measured with an IR dryer. Sample amount was about 1 g. The foam density was determined by dividing the measured weight of the foam with the measured volume.
Reference Examples 1 and 2
[0050] Reference examples 1 and 2 were performed in which the foaming capacity of aqueous suspensions without addition of a foam generating agent was evaluated in a laboratory trial. The components and properties of the suspensions of reference examples 1 and 2 are summarised in table 2:
TABLE-US-00002 TABLE 2 Example 1 2 Starch, barley, wt % 100 100 EHEC — — SDS — — Foam generation no no Temperature, ° C. 21.1 20.8 Solids, wt % (in the suspension 7 10 before foaming) Coat weight no no Foam density, g/100 ml Brookfield 10 rpm Brookfield 50 rpm pH (liquid) 6.61 6.67 Brookfield 50 rpm, liquid 9.2 9.8 Solids of the foam
[0051] The suspensions of reference examples 1 and 2 did not foam. This confirms that without additives, no foaming is observed.
Examples 3 to 6
[0052] A test series was performed in which the foaming capacity of suspensions comprising uncooked starch particles and amphiphilic polymer in accordance with the invention was evaluated. Experiments were performed using EHEC as foaming agent. The components and properties of the aqueous suspensions of examples 3 to 6 are summarised in table 3:
TABLE-US-00003 TABLE 3 Example 3 4 5 6 Starch, barley, wt % 100 100 100 100 EHEC, wt % 1 5 5 5 SDS — — — — Foam generation yes yes yes yes Temperature, ° C. 21 23 20.5 21 Solids, wt % 7 7 12 18 Coat weight 3.5 3.8 4.2 4.6 Foam density, g/100 ml 14.57 14.98 23 47.56 Brookfield 10 rpm 2100 1400 2200 4600 Brookfield 50 rpm 760 440 920 2360 pH (liquid) 5.7 6.2 6.0 5.78 Brookfield 50 rpm, liquid 11.6 22 64.6 540 Solids of the foam 11.58 17.15
[0053] In addition to pH and viscosity, the solids contents of the foam was measured for examples 5 and 6 providing of aqueous starch solutions with 12 and 18 wt-% solids content, respectively. The solid content was determined with an IR dryer. The sample amount was about 1 g. As can be seen in table 2, the content of starch in the foams of examples 5 and 6 was very high. The EHEC based foams were stable and did not break completely during coating. Further, the breakage of the EHEC foam in coating was more controlled.
[0054] The shows that not only foam coating using uncooked starch is possible to use, but that a tenside-free generation of foam can be achieved, yielding a much higher starch content than expected. This is a significant improvement over the prior art technique using SDS as a tenside.
Reference Examples 11 to 14
[0055] A further test series was performed in which the foaming behavior of aqueous starch solutions with SDS as foaming agent was evaluated. The components and properties of the aqueous suspensions of reference examples 11 to 14 are summarised in table 4:
TABLE-US-00004 TABLE 4 Example 11 12 13 14 Starch, barley, wt % 100 100 100 100 SDS, wt % 1 5 5 5 Foam generation poor poor poor poor Temperature, ° C. 21.6 22.5 20.6 21.4 Solids, wt % 7 7 12 18 Coat weight, gsm 2.4 3.3 2.4 2.3 Foam density, g/100 ml 26.98 13.2 24.43 24.95 Brookfield 10 rpm 840 1400 700 1100 Brookfield 50 rpm 480 560 460 400 pH (liquid) 6.75 7.03 6.92 6.95 Brookfield 50 rpm, 9 9.4 11 11.8 liquid Solids of the foam 6.05 6.52 8.12 9.9
[0056] The foam of reference example 11 using 1 wt % SDS broke almost immediately. However, the foam of reference example 12 using 5 wt % SDS was very stable and did not break when coated with a rod. Increasing the solids content to 12 and 18 wt % in the liquid suspension however did not result in higher solid content of foam when using SDS foams, as can be seen in reference samples 13 and 14 where the solid content of the foams remained low. Also, the water separated quickly. This shows that SDS as foaming agent only provides for poor foam generation with less starch content in the foam.
Reference Examples 15 to 18
[0057] A further test series was performed in which the foaming behaviour of aqueous starch solutions without foaming agent was evaluated. The components and properties of the aqueous suspensions of reference examples 15 to 18 are summarised in table 5:
TABLE-US-00005 TABLE 5 Example 15 16 17 18 Starch, barley, wt % 100 100 100 100 Foam generation no no no no Temperature 21.1 20.8 20.5 21.8 Solids, wt % 7 10 12 18 pH (liquid) 6.61 6.67 6.67 6.77 Brookfield 50 rpm, liquid 9.2 9.8 10.6 12.4
[0058] This reference examples illustrate the increasing viscosity with increasing solid content.