Moisture control material

Abstract

Method of manufacturing an active moisture control material, wherein the material is formed from a base board comprising cellulose fibers and having a basis weight in the range of from 50 to 500 g/m2 and having a bulk of at least 1.2 cm3/g, wherein the method comprises a surface treatment of at least one side of said base board with a surface treatment composition comprising carboxymethyl cellulose (CMC) and a metal salt, wherein said surface treatment composition comprises carboxymethyl cellulose in a range of from 2 to 10 weight-% based on the total solid content of said surface treatment composition, and the metal salt in a range of from 10 to 30 weight-% based on the total solid content of said composition.

Claims

1. Method of manufacturing an active moisture control material, wherein the material is formed from a base board comprising cellulose fibers and having a basis weight in the range of from 50 to 500 g/m.sup.2 and having a bulk of at least 1.2 cm.sup.3/g, wherein said method comprises a surface treatment of at least one side of said base board with a surface treatment composition comprising carboxymethyl cellulose (CMC) and a metal salt, wherein said surface treatment composition comprises carboxymethyl cellulose in a range of from 2 to 10 weight-% based on the total solid content of said surface treatment composition, and the metal salt in a range of from 10 to 30 weight-% based on the total solid content of said composition; and wherein said surface treatment composition is applied onto the at least one side of said base board in an amount in a range of from 10 to 150 g/m.sup.2.

2. The method as claimed in claim 1, wherein said surface treatment comprises applying said composition directly onto said at least one side of said base board.

3. The method of claim 1, wherein said surface treatment is any one of a surface sizing and a coating operation.

4. The method of claim 1, wherein the bulk is more than 1.5 cm.sup.3/g.

5. The method of claim 1, wherein the surface treatment composition comprises the metal salt in a range of from 10 to 20 weight-% based on the total solid content of the composition.

6. The method of claim 1, wherein said surface treatment composition is an aqueous suspension, having a dry content in the range of from 2 to 40%.

7. The method claim 1, wherein said metal salt is selected from the group consisting of any one of a sodium chloride, calcium chloride, potassium chloride and sodium nitrate.

8. The method of claim 1, wherein said base board is any one of a paper and a paperboard.

9. The method of claim 1, wherein the basis weight of the base board is in the range of 110 to 500 g/m.sup.2.

10. The method of claim 1, wherein the material is dried subsequent to the application of the surface treatment composition.

11. The method of claim 1, wherein the material is pre-conditioned subsequent to the application of the surface composition.

12. The method of claim 1, wherein the bulk is more than 2.0 cm.sup.3/g.

13. The method of claim 1, wherein said surface treatment composition is an aqueous suspension having a dry content in the range of from 10 to 30%.

14. The method of claim 1, wherein said surface treatment composition is applied onto the at least one side of said base board in an amount in the range of from 30 to 100 g/m.sup.2.

15. Method of manufacturing an active moisture control material, wherein the material is formed from a base board comprising cellulose fibers and having a basis weight in the range of from 50 to 500 g/m.sup.2 and having a bulk of at least 1.2 cm.sup.3/g, wherein said method comprises a surface treatment of at least one side of said base board with a surface treatment composition comprising carboxymethyl cellulose (CMC) and a metal salt, wherein said surface treatment composition comprises carboxymethyl cellulose in a range of from 2 to 10 weight-% based on the total solid content of said surface treatment composition, and the metal salt in a range of from 10 to 30 weight-% based on the total solid content of said composition; and wherein the material is pre-conditioned subsequent to the application of the surface composition.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present solution will now be described, by way of example, with reference to the accompanying drawings.

(2) FIG. 1 illustrates a graph showing absorption capacity.

(3) FIG. 2 illustrates a graph showing desorption capacity.

DESCRIPTION OF EMBODIMENTS

(4) The invention relates to a manufacturing method of an active moisture control material, where a base board is provided with a surface treatment composition, i.e. the surface treatment composition is applied to the base board. In the inventive method at least one side of the base board is provided with the surface treatment composition.

(5) The surface treatment composition may be applied directly onto the base board, for instance in a conventional paper making process. The surface treatment composition may be applied in a surface sizing step, such as a surface press or alternatively as a coating, such as through dispersion coating, blade coating, curtain coating, rod coating, slot-die coating and spray technologies or printing technologies.

(6) Subsequent to the application of the surface treatment composition the material may be dried. The drying process may be any conventional drying method, such as using hot cylinders, air drying or vacuum drying.

(7) The dry content of the material after drying is preferable in the range of 1 to 13%, and most preferably in the range of 2 to 10%.

(8) The base board may be any one of a paper or paper board. The base board may essentially be any type of web type material, where fiber material is produced from non-fossile based raw materials, and which is used in conventional paper or board making processes. The base board may further be made from any type of a cellulose based material.

(9) The base board has a grammage or basis weight in the range of from 50 to 500 g/m.sup.2, preferably in the range of 110 to 500 g/m.sup.2, or even in the range of 175 to 500 g/m.sup.2.

(10) The porosity of the base board may be defined as bulk, which is measured according to standard ISO 534.

(11) The bulk of the base board is preferably more than 1.2 cm.sup.3/g, or preferably above 1.5 cm.sup.3/g, or even more preferred above 2.0 cm.sup.3/g. The paper or paperboard is therefore preferably a so called high-bulk material. The bulk correlates to the porosity of the base board, and thus also the ability of the base board to absorb the surface treatment composition in or into the base board. By applying the surface treatment onto the base board there is therefore formed an active moisture control material. The EU Commission Regulation (EC) No 450/2009 on active and intelligent materials and articles intended to come into contact with food, defines that these active material include absorbing/scavenging systems, releasing systems and systems with substances grafted or immobilized on wall of the packaging.

(12) The surface treatment composition comprises carboxymethyl cellulose (CMC) and a metal salt.

(13) The proportion or amount of CMC in the composition is preferably in the range of 2 to 10 weight-% based on total solid content of said composition.

(14) The composition comprises metal salt in an amount of around 10-30 weight-%, or most preferably around 10-20 weight-% based on total solid content of said composition.

(15) The surface treatment composition may be an aqueous composition with a dry content in the range of from 2 to 40%, and preferably in the range of from 10 to 30%.

(16) The composition is preferably applied onto the surface of the base board in an amount of from 10 to 150 g/m.sup.2, and preferably in the range of from 30 to 100 g/m.sup.2.

(17) The metal salt is preferably chosen from the group of sodium chloride, calcium chloride and potassium chloride, sodium nitrite.

(18) In one embodiment the metal salt is sodium nitrite, due to its capacity for absorbance, especially at desired humidity area of around relative humidity (RH) 65%.

(19) The moisture control properties of the material may be measured and defined as an absorption capacity or velocity of the material from 22° C. and 60% relative humidity to 30° C. and 65% relative humidity, and a desorption velocity or capacity from 22° C. and 60% relative humidity to 35° C. and 15% relative humidity.

(20) It has been shown that the application of CMC and metal salt in these amounts provide good coverage and quality of the end product and yet applicable from a process engineering point of view.

(21) The active control material may be used as a blank or base packaging material to for different types of packages.

(22) The packaging formed from the active moisture control material or the active moisture control material itself, may be pre-conditioned prior to the closing of the package. By pre-conditioning is meant that the material may be for instance pre-moisturized, i.e. made to absorb moisture, such as water, or water mixed with additives, such as PEG.

(23) The moisture content after pre-conditioning or pre-moisturizing may be in the range of 2 to 30%. The moisture content after pre-moisturizing varies depending on the desired relative humidity in for instance the packaging formed from the material.

(24) This pre-conditioning may take place during converting the blank into the packaging material or during filling of the packaging.

(25) The pre-conditioning may be preceded by a drying operation, as described above.

(26) The packaging comprising the active control material may be used for all types of moisture sensitive products, such as cigarettes, medicaments, cosmetics, electronics, metal products, apparel, shoes and food.

(27) In one alternative embodiment the base board may be provided with the surface treatment composition in a moisture control pattern at well-defined areas of the base board, such that it is only this area or pattern that has the active moisture control properties. This may be done by printing process or slot die coating etc.

(28) According to one alternative embodiment a passive barrier material may be provided onto the active moisture control material. Such a passive barrier material may be any one of a synthetic or renewable polymer. Examples of synthetic polymers may be any one of low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP) and polyethylene terephthalate (PET). Examples of renewable polymeras may be so called green polyethylene (PE), green polyethylene terephthalate (PET), polylactic acid and polybutylene succinate (PBS). The passive barrier material may be applied onto the active control material during the manufacturing, for instance as a coating or film layer, or afterwards as a detachable film.

(29) Examples of film application are film lamination, glue lamination, pressure sensitive lamination. The barrier layer may alternatively be applied through dispersion, water or solvent based coating systems. It may also be extrusion coated or extrusion laminated onto the active moisture control material.

(30) In addition to providing the active moisture control material with a passive barrier, it may also be provided with a paper or board layer in a laminate structure, i.e. board/passive barrier/moisture control material. The active moisture control material would be inside the package. This would provide the advantage that stiffness to the package is generated mainly from outer board/paper layer which would not be absorbing moisture to any greater extent.

(31) In view of the above detailed description of the present invention, other modifications and variations will become apparent to those skilled in the art.

(32) However, it should be apparent that such other modifications and variations may be effected without departing from the spirit and scope of the invention.

(33) Absorption and Desorption Tests

(34) A base board comprising was surface sized using three different surface treatment compositions.

(35) Sample no 1 was treated with a surface treatment composition comprising 10% based on total solid content of said composition CMC+30% based on total solid content of said composition NaNO.sub.2, in accordance with the invention, and compared to a base board treated with a coating with almost 100% salt based on total solid content of said composition salt and using Boveda: sodium formate+sodium lactate (Sample no. 5) and a base board treated with only CMC (Sample no. 6).

(36) As can be seen in FIG. 1 the inventive surface sizing (No. 1) has the best absorption capacity (at an increase from RH 60 to RH 70) and in FIG. 2, yet an acceptable desorption capacity (at a decrease from RH 60 to RH 15).