Production of sack paper

• US 10,458,070 B2
• Filed: 06/24/2015
• Issued: 10/29/2019
• Est. Priority Date: 07/04/2014
• Status: Active Grant

• Current Assignee: BillerudKorsnas AB
• Original Assignee: BillerudKorsnas AB
• Inventors: Almkvist, Jonas, Lindstrom, Ove, Xenopoulos, Constantinos
• Primary Examiner(s): Fortuna, Jose A
• Application Number:
  US15/322,589
• Publication Number:
  US 20180202111A1
• Time in Patent Office: 1,588 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, per ISO 5636/5, of 2-10 s, comprising the steps of:

a) providing bleached pulp;

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

c) adding cationic starch to the pulp in an amount of 1.5-4 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 0.5 kg/ton paper of anionic starch is added to the pulp.

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

ping.

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. The method according to claim 1, wherein the pulp comprises bleached sulphate pulp.

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

cationic starch was added in an amount of 1.5-4 kg/ton paper;

size was added in an amount of 0.4-2.0 kg/ton paper; and

less than 0.5 kg/ton paper of anionic starch was added,

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

6. The white sack paper according to claim 5, wherein the Gurley porosity is 4-10 s.

7. The white sack paper according to claim 5, wherein the Cobb 60 S value, per ISO 535, of at least one surface is least at least 50 g/m².

8. The white sack paper according to claim 5, wherein the tensile energy absorption index, per ISO 1924-3, is at least 1.8 J/g in both a machine direction and a cross direction.

9. 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 5 and a moisture barrier coating layer.

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

11. A valve sack for a hydraulic binder, comprising a ply composed of the multilayered paper material according to claim 9.

12. A valve sack for a hydraulic binder, comprising a ply composed of the white sack paper according to claim 5.

13. A multiple-ply valve sack for a hydraulic binder, comprising an inner ply composed of sack paper according to claim 5.

14. The multiple-ply valve sack of claim 13, further comprising an outer ply having a moisture barrier coating layer.

15. The white sack paper according to claim 5, wherein the pulp comprises bleached sulphate pulp.