PRODUCTION OF SACK PAPER

• US 20180202111A1
• Filed: 06/24/2015
• Published: 07/19/2018
• Est. Priority Date: 07/04/2014
• Status: Active Grant

• Current Assignee: BillerudKorsnas AB
• Original Assignee: BillerudKorsnas AB
• Inventors: ALMKVIST, Jonas, LINDSTROM, Ove, XENOPOULOS, Constantinos
• Granted Patent: US 10,458,070 B2
• Time in Patent Office: Days
• CPC Class Codes: B31F 1/126 including making of the paper to be crêped
• CPC Class Codes: B65D 31/04 with multiple walls B65D81/3881 takes precedence; for shock absorbing purposes B65D81/03
• CPC Class Codes: B65D 31/14 Valve bags, i.e. with valves for filling
• CPC Class Codes: C04B 28/04 Portland cements
• CPC Class Codes: C04B 40/0039 Premixtures of ingredients
• CPC Class Codes: D21H 17/28 Starch
• CPC Class Codes: D21H 17/29 cationic
• CPC Class Codes: D21H 17/44 cationic
• CPC Class Codes: D21H 19/20 comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: D21H 19/40 siliceous, e.g. clays
• CPC Class Codes: D21H 19/44 characterised by the other ingredients, e.g. the binder or dispersing agent
• CPC Class Codes: D21H 19/82 superposed D21H19/84 takes precedence
• CPC Class Codes: D21H 19/828 two superposed coatings, the first applied being non-pigmented and the second applied being pigmented
• CPC Class Codes: D21H 21/16 Sizing or water-repelling agents
• CPC Class Codes: D21H 21/18 Reinforcing agents
• CPC Class Codes: D21H 27/10 Packing paper packaging materials of special type or form B65D65/38
• CPC Class Codes: Y02W 90/10 Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics

Abstract

There is provided a method of making white sack paper having a grammage of 50-140 g/m2 and a Gurley porosity (ISO 5636/5) of 2-10 s, comprising the steps of: a) providing bleached pulp, such as bleached sulphate pulp; b) subjecting the pulp to high consistency (HC) refining and optionally low consistency (LC) refining to the extent that the sack paper obtains the Gurley porosity; c) adding cationic polymer, such as cationic starch, to the pulp in an amount of 1.5-5.0 kg/ton paper; and d) adding size to the pulp in an amount of 0.4-2.0 kg/ton paper; and e) forming the sack paper from the pulp, wherein less than 2 kg/ton paper of anionic starch is added to the pulp.

Claims

1. A method of making white sack paper having a grammage of 50-140 g/m² and a Gurley porosity (ISO 5636/5) of 2-10 s, comprising the steps of:

a) providing bleached pulp, such as bleached sulphate pulp;

b) subjecting the pulp to high consistency (HC) refining and optionally low consistency (LC) refining to the extent that the sack paper obtains the Gurley porosity;

c) adding cationic starch to the pulp in an amount of 1.5-5.0 kg/ton paper, such as 2-4 kg/ton paper; and

d) adding size to the pulp in an amount of 0.4-1.9 kg/ton paper, such as 0.5-1.5 kg/ton paper, such as 0.7-1.3 kg/ton paper; and

e) forming the sack paper from the pulp,

wherein less than 2 kg/ton paper, such as less than 1.0 kg/ton paper, such as less than 0.5 kg/ton paper of anionic starch is added to the pulp.

2. The method according to claim 1, wherein step e) comprises creping.

3. The method according to claim 1, wherein the method further comprises the steps of:

f) applying a pre-coating composition onto the sack paper to form a pre-coating layer; and

g) applying a barrier coating composition onto the pre-coating layer to form a barrier layer.

4. A white sack paper having a grammage of 50-140 g/m² and a Gurley porosity (ISO 5636/5) of 2-10 s formed from bleached sulphate pulp to which:

cationic starch was added in an amount of 1.5-5.0 kg/ton paper, such as 2-4 kg/ton paper;

size was added in an amount of 0.4-2.0 kg/ton paper, such as 0.5-1.5 kg/ton paper, such as 0.7-1.3 kg/ton paper; and

less than 2 kg/ton paper, such as less than 1 kg/ton paper, such as less than 0.5 kg/ton paper, of anionic starch was added,

and which pulp was subjected to high consistency (HC) refining and optionally low consistency (LC) refining to the extent that the sack paper obtained the Gurley porosity.

5. The white sack paper according to claim 4, wherein the Gurley porosity is 4-10 s, such as 4-8 s, such as 4-7 s, such as 5-6.5 s.

6. The white sack paper according to claim 4, wherein the Cobb 60 S value (ISO 535) of at least one surface is least at least 50 g/m², such as at least 60 g/m², such as at least 70 g/m², such as between 75 and 110 g/m².

7. The white sack paper according to claim 4, wherein the tensile energy absorption index (ISO 1924-3) is at least 1.8 J/g, such as at least 2 J/g, such as at least 2.2 J/g, in both the machine direction (MD) and the cross direction (CD).

8. A multilayered paper material for use in a valve sack for a hydraulic binder, comprising a paper layer composed of the white sack paper according to claim 4 and a moisture barrier coating layer.

9. The multilayered paper material according to claim 8, wherein a pre-coating layer comprising at least 50 wt. % (dry substance) of inorganic filler is provided between the paper layer and the moisture barrier coating layer.

10. A valve sack for a hydraulic binder, such as cement, comprising a ply composed of the white sack paper according to claim 4.

11. A valve sack for a hydraulic binder, such as cement, comprising a ply composed of the multilayered paper material according to claim 8.

12. A multiple-ply valve sack for a hydraulic binder, such as cement, comprising an inner ply composed of sack paper 4-7 and an outer ply composed of the multilayered paper material according to claim 8.

13. Use of a sack according to claim 10 to produce a hydraulic composition, such as concrete, wherein the sack contains a hydraulic binder, aggregates and/or mineral additions.

14. A process for the production of a hydraulic composition comprising mixing water, aggregates and a hydraulic binder, wherein a sack according to claim 10 is used, which sack contains the hydraulic binder and/or the aggregates, said process comprising the following steps:

a) introduction of water and aggregates in a concrete mixer;

b) introduction of the hydraulic binder; and

c) optionally introduction of mineral additions and/or other admixtures, wherein the sack is introduced during step a and/or step b.