Machine Glazed Paper and Method for Preparing the Machine Glazed Paper

The present disclosure relates to the field of machine glazed paper and a method for preparing the machine glazed paper. More specifically the present disclosure relates to a machine glazed paper for preparing paper sticks.

There is an increasing requirement to minimize the use of single-use plastic items, such as cotton buds and lollipop sticks.

In view of these requirements there is a need to develop materials which may replace the plastics in such items.

Besides being one of the most abundant biopolymers on Earth, cellulose attracts considerable attention due to its high strength and stiffness combined with features like low weight, biodegradability and renewability. Paperbased materials have however traditionally been considered less suitable for replacement of such single-use plastic material, such as for example cotton buds and lollipop sticks, as paperbased items have been considered having low shape stability compared to such plastic items. It has also been difficult to attain a proper sealability without including components negatively affecting the degradability of the items. During manufacturing of such paper component, dusting and blunting have also been causing important issues in the converting machines.

In view of the above, it is an object to prepare an improved material suitable for use in preparing single-use paper sticks.

It is an object of the present disclosure to provide a paper that at least partially overcome the above-described deficiencies. This is achieved by a machine-glazed paper according to claim, use of the machine-glazed paper according to claim, a paper stick comprising or consisting of the machine-glazed paper according to claimand a method for producing the machine-glazed paper according to claim.

According to a first aspect, there is provided a machine glazed paper comprising softwood fibers and starch, the machine glazed paper comprising the starch in an amount within the range of from 0.1 wt. % by weight to 2 wt. % of the dry weight of the machine glazed paper and the amount of softwood fibers of the total amount of fibers is 63 wt. % or more. The machine glazed paper has a Cobb value within the range of from 20 gsm to 50 gsm, as measured according to the standard method ISO 535:2014.

There are increasing demands and legislative requirements to replace plastic single-use items such as cotton bud sticks with biodegradable alternatives. Paperbased materials have however traditionally been considered less suitable for use in making cotton bud sticks or the like, as they have been considered to have low shape stability compared to such plastic sticks. It was found by the present inventors that by using a softwood fiber paper, having a high starch content and a fast water absorption, indicated by the Cobb value, according to the present disclosure, a paper particularly suitable for preparing paper sticks was achieved. The machine-glazed paper has improved sealability and when preparing paper sticks with the paper according to the present disclosure stiffer sticks with an improved straightness, as seen in the length direction of the sticks, but which still resist bending of the sticks without breaking was obtained. It was additionally and surprisingly found that this combination of features at least partly solves the problem of dusting and linting when preparing paper sticks from the paper according to the present disclosure.

The machine glazed paper comprises softwood cellulose fibers, also called long fibers. In native condition, softwood cellulose fibres measure from about 2 to 4 millimetres in length, compared to hardwood fibres ranging from about 0.5 to 1.5 millimetres. Common examples of softwood include pine, fir, spruce, larch and cedar. In paper, after refining the softwood fibers are below 2 mm.

The paper comprises long fibers which enables production of paper sticks having an improved bending resistance and reduced dusting during slitting operations. The high starch content in combination with the high and fast water absorption of the paper has been found by the present inventors to enable an improved tensile strength and sealability of the paper during formation of paper sticks.

Both of the sides of the machine glazed paper, i.e. the glazed and the non-glazed side of the machine glazed paper, have a Cobb value within the range of from 20 gsm to 50 gsm, as measured according to the standard method ISO 535:2014.

The machine glazed paper may have a Cobb value within the range of from 24 gsm to 50 gsm, as measured according to the standard method ISO 535:2014. Optionally, within the range of from 25 gsm to 45 gsm.

The machine glazed paper may comprise the starch in an amount within the range of from 0.2 wt. % by weight to 2 wt. % of the dry weight of the machine glazed paper, preferably 0.4 wt. % to 2 wt. % of the dry weight of the machine glazed paper.

The Cobb value of the paper may be obtained by lowering the amount of sizing agents in the paper, such as to a level of below 0.9 wt. %, optionally to a level of below 0.5 wt. %. Preferably, the amount of sizing agents in the paper may be 0.3 wt. % or below, such as 0.1 wt. % or below. Optionally, the paper is free Alkylketen Dimer (AKD) and Alkenyl Succinic Anhydride (ASA).

The machine glazed paper may comprise rosin in an amount of below 1 wt. %, preferably within the range of from 0.05 wt. % to 0.5 wt. %, based on the dry weight of the machine glazed paper, more preferably within the range of from 0.09 to 0.3 wt. %, based on the dry weight of the machine glazed paper.

The machine glazed paper may comprise Alum (aluminum sulfate) in an amount within the range of from 0.1 wt. % to 1 wt. %, preferably within the range of from 0.1 wt. % to 0.5 wt. %, based on the dry weight of the machine glazed paper.

The machine glazed paper may comprise 4 wt. % or less of fillers, such as 3 wt. % or less of fillers, such as 2 wt. % or less of fillers, preferably 1 wt. % or less of fillers, more preferably 0.5 wt. % or less of fillers, even more preferably 0.2 wt. % or less of fillers, based on the total weight of the paper, preferably the machine glazed paper is free from fillers. A machine glazed paper comprising softwood fibers and having a Cobb value according to the present disclosure comprising with 4 wt. % or less of fillers, based on the total dry weight of the paper, was found favourable with respect to dusting during cutting and blunting of the cutting and slitting tools. It was also found to increase the stiffness of paper sticks produced by the paper.

Optionally, 65 wt. % or more of the fibers in the machine glazed paper are softwood fibers, preferably 75 wt. % or more of the fibers in the machine glazed paper are softwood fibers, more preferably, from 85 wt. % to 100 wt. % of the fibers in the machine glazed paper are softwood fibers.

Optionally, from 95 wt. % to 100 wt. % by weight of the of the fibers in the machine glazed paper are softwood fibers, preferably 100 wt. % of the fibers in the machine glazed paper are softwood fibers.

The fact that 65 wt. % or more of the fibers in the machine glazed paper are softwood fibers, such as from 85 wt. % to 100 wt. % of the fibers in the machine glazed paper are softwood fibers has been found favourable with respect to dusting during cutting of the paper and paper sticks formed by the paper according to the present disclosure.

The machine glazed paper may have a basis weight within the range of from 35 gsm to 100 gsm, preferably within the range of from 38 gsm to 85 gsm. It has been found that the machine glazed paper according to the present disclosure is within these ranges are particularly suitable for forming paper sticks. When using the machine glazed paper of higher basis weight, the stiffness was increased and when using lower ranges, the process of making the paper sticks was negatively affected since an increased number or rolling is needed which increases the complexity and the defect rate of the paper sticks during process.

The softwood fibers may be unbleached softwood fibers. It was surprisingly found that the sealability of the paper, during manufacturing of paper sticks, was improved by using unbleached softwood fibers.

The softwood fibers may alternatively be bleached softwood fibers or a mix between bleached and unbleached softwood fibers.

The machine glazed paper may have an CD/MD ration of from 0.5. This provides an indication that the fibers of the machine glazed paper mainly are oriented in the MD direction. During slitting of the paper, when manufacturing paper sticks, such fiber orientation was found advantageous in that dusting was reduced.

The machine glazed paper may have a MD stretch of from 0.5% to 2%, preferably a MD stretch of from 1% to 1.9%, as measured according to the standard method ISO 1924/3. The fact that the machine glazed paper exhibited a MD stretch of from of from 0.5% to 2% enabled production of stiffer paper sticks by the paper according to the present disclosure.

The machine glazed paper may have a CD stretch of from 1.5% to 6.5%, preferably a CD stretch of from 2% to 5.5%, such as a CD stretch within the range of from 2 to 4.5%, as measured according to the standard method ISO 1924/3. The fact that the machine glazed paper exhibited a CD stretch of from 10 1.5% to 6.5% enabled production of stiffer paper sticks which also resist bending without breakage.

The fact that the first side of the paper is machine glazed provides the paper with enhanced sealing when being an inner side during paper stick production. The non-glazed side of the machine glazed paper may have a roughness of 500 15 ml/min to 2000 ml/min, preferably within the range of from 350 ml/min to 1500 ml/min. The fact that the second side, being the outer side during paper stick production, is a non-glazed side having a roughness of from 350 ml/min to 2000 ml/min, such as 500 ml/min to 2000 ml/min, preferably within the range of from 350 ml/min to 1500 ml/min, provides an improved adherence to, by frictional 20 force, for example the cotton part in a cotton bud. It has also seen providing an improved user handfeel.

The paper may be a non-calendered paper, this provides an increased roughness for the non-glazed side of the paper.

The machine glazed paper may have an air resistance within the range of from 15 to 35 s, as measured according to the standard method ISO 5636 “Paper and board—Determination of air permeance (medium range)—Part 5: Gurley method. It was surprisingly found by the present inventor that the sealing speed of the machine glazed paper is improved when the air resistance of the paper is within the range of from 15 to 35 s.

The machine glazed paper may be for use to prepare paper sticks, such for ear buds or lollipop sticks.

According to a second aspect, the present disclosure relates to a use of the machine glazed paper according to the first aspect for producing a paper stick.

According to a third aspect, the present disclosure relates to a paper stick, such as an ear bud stick or a lollipop stick comprising or consisting of the machine glazed paper according to the first aspect.

According to a fourth aspect, the present disclosure relates to a method for producing the machine glazed paper according to the first aspect, the method comprising the steps of;

providing a suspension comprising softwood fibers and starch, the starch being in an amount within the range of from 0.1 wt. % to 2 wt. % based on total dry weight and the amount of softwood fibers of the total amount of fibers are 63 wt. % or more;

The method may comprise a pre-drying step, between the dewatering step and the glazing step, wherein the fibrous web is pre-dried in the pre-drying step. The moisture content in the fibrous web may be controlled in the pre-drying step, and if needed, the moisture content in the fibrous web may be adapted in the pre-drying step. Optionally, the moisture content is within the range of from 40 to 60 wt. % when entering the glazing unit. This may for example be achieved by adapting the speed and/or the temperature of the drying cylinders.

It was discovered by the present inventors that the adherence to the cylinder in the glazing unit may be improved by controlling the moisture content of the fibrous web in a pre-drying step, and if necessary, adapting the moisture content of the fibrous web to be within a set moisture content range when entering the glazing unit. An unfavourable adherence/rejection of the fibrous web to the cylinder may give rise to a non-uniform drying of the fibrous web and such non-uniform drying was seen to provide a higher roughness value, impairing the sealing of the paper upon preparation of the paper sticks. However, by controlling the moisture content in the fibrous web in the pre-drying step, and adapting the moisture content when needed, the adherence to the cylinder may be improved and also the roughness of the surface, which may lead to an improved sealing of the paper sticks prepared by the machine glazed paper.

The roughness of the first side, i.e. the glazed side may be within the range of from 100 to 400 ml/min.

In the method for producing the machine glazed paper, 65 wt. % or more of the fibers in the machine glazed paper may be softwood fibers, preferably 75 wt. % or more of the fibers in the machine glazed paper are softwood fibers, more preferably, from 85 wt. % to 100 wt. % of the fibers in the machine glazed paper are softwood fibers.

Optionally, from 95 wt. % to 100 wt. % by weight of the of the fibers in the machine glazed paper are softwood fibers, preferably 100 wt. % of the fibers in the machine glazed paper are softwood fibers.

The machine glazed paper may comprise rosin in an amount of below 1 wt. %, preferably within the range of from 0.05 wt. % to 0.5 wt. %, based on the dry weight of the machine glazed paper, more preferably within the range of from 0.09 to 0.3 wt. %, based on the dry weight of the machine glazed paper.

The machine glazed paper may comprise Alum (aluminum sulfate) in an amount within the range of from 0.1 wt. % to 1 wt. %, preferably within the range of from 0.1 wt. % to 0.5 wt. %, based on the dry weight of the machine glazed paper.

The machine glazed paper may comprise 4 wt. % or less of fillers, such as 3 wt. % or less of fillers, such as 2 wt. % or less of fillers, preferably 1 wt. % or less of fillers, more preferably 0.5 wt. % or less of fillers, based on the total weight of the paper, preferably the machine glazed paper is free from fillers. A machine glazed paper comprising softwood fibers and having a Cobb value according to the present disclosure comprising with 4 wt. % or less of fillers, based on the total dry weight of the paper, was found favourable with respect to dusting during cutting and blunting of the cutting and slitting tools. It was also seen increasing the stiffness of paper sticks produced by the paper.

The amount of filler may be measured by means of ash content by the standard method ISO 1762:2001. The type of fillers may be determined by Fourier-transform infrared spectroscopy (FTIR).

In order to prepare a machine glazed paper according to the present disclosure, with such a high percentage of softwood fibers and a low, or no, percentage of fillers, sizing agents etc., it may be necessary to adjust the paper quality run previously in the paper machine to ensure that no fillers, sizing agents or non-softwood fibers from the previous paper quality are introduced into the fiber suspension by means of the waste water.

The machine glazed paper may have a Cobb value within the range of from 24 gsm to 50 gsm, as measured according to the standard method ISO 535:2014. Optionally, within the range of from 25 gsm to 45 gsm.

Optionally, the suspension may comprise the starch in an amount within the range of from 0.2 wt. % by weight to 2 wt. % based on total dry weight, preferably 0.4 wt. % to 2 wt. % based on total dry weight.

The softwood fibers of the suspension may be unbleached or bleached softwood fibers.

The softwood fibers may alternatively be bleached softwood fibers or a mix between bleached and unbleached softwood fibers.

The machine glazed paper may have an CD/MD ration of from 0.5. This is an indication of that the fibers of the machine glazed paper may mainly be oriented in the MD direction, such as that 75 wt. % of the fibers of the machine glazed paper are oriented in the MD direction.

The second side of the machine glazed paper may have a roughness of from 350 ml/min to 2000 ml/min, optionally within the range of from 500 ml/min to 2000 ml/min, preferably within the range of from 350 ml/min to 1500 ml/min. This provides an improved adherence to, by frictional force, for example the cotton part in a cotton bud. It has also seen providing an improved user handfeel.