FIELD OF THE INVENTION

The present disclosure relates to a novel water disintegrable core to be used as a support for a roll of paper, especially for a toilet paper.

Further, the present disclosure relates to a process for producing such a water disintegrable core.

BACKGROUND OF THE INVENTION

Papers for sanitary or domestic use are usually packaged as core-comprising rolls. Said paper rolls, such as toilet paper roll or paper towel roll, are formed by winding the paper around a core that is generally made of cardboard. Said core is necessary to give robustness to the toilet paper roll to avoid deformations during production, storage, transport and use.

Most of the cores that are used in conventional paper product rolls are disposed in the waste bins since they lead to a blockage of the soil pipe of toilets if they are thrown away down the toilet bowls. However, in recent years consumers desire to throw said cores directly into the toilet bowl due to its ease of use, to avoid use of waste bins and the desire to decrease the amount of wastes produced by consumers. In this manner, the volume of waste to be destroyed or to be stored at dumps will decrease which results in a positive effect on the environment.

One of the most important features that water disintegrable cores must have is the good stiffness characteristics. A core which does not have adequate strength cannot resist crushing by packaging, loading or transportation. This feature directly affects the quality of the products obtained.

Another important feature of a water disintegrable core is its disintegration time in water. Said cores must quickly disintegrate on contact with water in order to avoid the blockage of toilet drain lines.

Water disintegrable cores which are suitable for throwing away down the toilet bowls are known to date. For example, US 2010,167,889 describe a core which disintegrates in water, therefore can be thrown away into the toilet. The core is obtained by winding of tissues, impregnated with starch. However, in said method a lot of tissue layers are required to produce a core having sufficient stiffness. The application of excessive amounts of starch to the tissue layers and high energy consuming drying process makes the production process unfavourable.

The present invention aims to solve the problems raised above, to provide a water disintegrable core which can be thrown directly into toilet bowls and has the advantage of being relatively inexpensive.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide an improved method in order to produce a core to be used as a support for a paper roll which disintegrates quickly upon contact with water and has sufficient mechanical strength.

This object is solved in the present application by using at least one cardboard sheet which is made of unrefined short cellulose fibers and free of a binding agent for the preparation of a water disintegrable core.

In accordance with an embodiment of the invention, the objectives of the invention are successfully achieved by using at least one cardboard sheet which is made of unrefined short cellulose fibers having an average length of between 0.4-2mm.

In accordance with another embodiment of the invention, the water disintegrable core disintegrates in water within 3 minutes, and preferably within 1 minute according to core disintegration time test method by mechanically stirring in a vessel containing water.

In accordance with an embodiment of the invention, the objectives of the invention are successfully achieved with a water disintegrable core with a basis weight of between 100 and 600 g/m ² , preferably between 200 and 450 g/m ² .

In accordance with another embodiment of the invention, the water disintegrable core is made of a cardboard sheet which is made of unrefined short cellulose fibers and which further comprises alkali salts of carboxymethyl cellulose, preferably sodium salt of carboxymethyl cellulose.

The object of the present invention is further to provide a process to prepare said water disintegrable core comprising following steps:

- unrefined short cellulose fibers are provided,

- cellulose fibers are disintegrated in water to form a pulp, - excessive water is removed from the pulp with wet-press,

- remaining water is removed until obtaining 95% solids containing aqueous mixture by weight by means of drying cylinders to obtain cardboard sheets ,

- obtained cardboard sheets are sliced, then said sliced sheets are spirally wounded and adhesively bonded to form a hollow tube,

- Finally said hollow tube is cut to form a water disintegrable core of the present invention.

In accordance with another embodiment of the invention, the water disintegrable core is made of one or more cardboard sheets, preferably containing two cardboard sheets adhered with an adhesive one on the top of the other.

In accordance with another embodiment of the invention, obtained cores can be used as a support in paper product rolls such as toilet paper rolls, paper towel rolls, or the like.

FIGURES

Figure 1. A water disintegrable core of the present invention

Figure 2. Production process of a cardboard sheet used to form the water disintegrable core of the present invention wherein:

1 : water

2: fiber

3: aqueous solution of sodium carboxymethyl cellulose

4: pulp

5: wire section

6: wet press

7: drying cylinders

8: after drying section

9: cardboard sheet DETAILED DESCRIPTION OF THE INVENTION

The present inventors have surprisingly found that a water disintegrable core to be used as a support for a paper roll which quickly disintegrates upon contact with water can be produced by using at least one cardboard sheet which is made of unrefined short cellulose fibers and free of a binding agent in its preparation process.

According to an embodiment of the present invention, the water disintegrable core to be used as a support for a paper roll is produced by using at least one cardboard sheet which is made of unrefined short cellulose fibers having an average length of 0.4-2 mm and which is free of a binding agent.

Short cellulose fibers are defined according to the present application as cellulose fibers having an average of 0.4 - 2 mm, preferably 0.5 - 1.5 mm, and more preferably 0.6- 1 mm of length. Said fibers are not refined, milled or crushed mechanically.

Against the common practice, the cellulose fibers in the paper forming industry used in a method according to the present invention are not subjected to a step of refining. We believe that refining increases the surface area between cellulose fibers resulting in an increase in bonding capabilities of said fibers, which is not a desired effect in case of a disintegrating core product.

According to another embodiment of the present invention, the water disintegrable core of the present invention disintegrates in water within 3 minutes, preferably within 1 minute by mechanically stirring in a vessel containing water in accordance with a core disintegrating time test method as described in the specification herein.

According to another embodiment of the present invention, the water disintegrable core of the present invention disintegrates in water to an extent not clogging the waste water pipeline when it is thrown and flushed into the toilet bowl.

According to the present application, a method for producing a core which disintegrates in water comprises the following steps; a- providing unrefined short cellulose fibers, b- disintegrating cellulose fibers in water to form a pulp, c- removing water from the pulp with wet-press to a water content of less than 60% by weight, d- removing remaining water until obtaining 95% solids containing aqueous mixture by weight by means of drying cylinders to obtain cardboard sheets , e- slicing obtained cardboard sheets, f- spirally winding and adhesively bonding said cardboard sheet to form a hollow tube, g- cutting of said hollow tube to form the water disintegrable core.

The core produced by a method according to the present invention which can disintegrate in water has a basis weight of between 100 and 600 g/m ² , preferably between 200 and 450 g/m ² .

According to an embodiment of the present invention, the method comprises the step of adding an aqueous solution of alkali metal salt of carboxymethyl cellulose to the pulp, wherein the solution has a concentration of at least 0.1 % by weight. Using alkali metal salts of carboxymethyl cellulose helps to improve the stiffness characteristics of the water disintegrable core. In a preferred embodiment, alkali metal salt of carboxymethyl cellulose is sodium carboxymethyl cellulose.

According to another embodiment of the present invention, a method for producing a core which disintegrates in water comprises the following steps; a- providing unrefined short cellulose fibers, b- disintegrating cellulose fibers in water to form a pulp at 4-5% consistency in water by weight, c- adding an aqueous solution of an alkali salt of carboxymethyl cellulose to the pulp, d- removing water from the pulp with wet-press to a water content of less than 60% by weight, e- removing remaining water until obtaining 95% solids containing aqueous mixture by weight by means of drying cylinders to obtain cardboard sheets, f- slicing obtained cardboard sheets, g- spirally winding and sidelongs adhesively bonding said cardboard sheets to form a hollow tube, h- cutting of said hollow tube to form the water disintegrable core.

Pulp consistency or concentration is defined as the weight in grams of oven-dry fiber in 100 grams of pulp-water mixture.

According to another embodiment of the present invention, the weight ratio of sodium salt of carboxymethyl cellulose solution to the unrefined short cellulose fibers is at least 0.1 % by weight in dry state.

According to another embodiment of the present invention, the water disintegrable core comprises two or more cardboard sheets adhered with an adhesive one on the top of the other.

According to another embodiment of the present invention, a method for producing a core which disintegrates in water comprises the following steps; a- providing unrefined short cellulose fibers, b- disintegrating cellulose fibers in water to form a pulp at 4-5% consistency in water by weight, c- adding a 1 % aqueous solution of alkali metal salt of carboxy methyl cellulose to the pulp, d- removing water from the pulp with wet-press to a water content of less than 60% by weight, e- removing remaining water until obtaining 95% solids containing aqueous mixture by weight by means of drying cylinders to obtain cardboard sheets, f- winding the cardboard sheets to form a cardboard coil, g- slicing said cardboard coils into coils having same or different widths, h- adhesively bonding two of said coils one on top of the other to obtain a cardboard coil with two cardboard sheets, and i- immediately spirally winding of said cardboard coil with two cardboard sheets to form a hollow tube, i- cutting of said hollow tube to form a core.

It has been found that a core produced according to a method of the present invention disintegrates in water faster than a similar standard core of the prior art. The term“similar standard core” is understood to mean a core having substantially the same diameter, substantially similar weight and the same length as the core of the invention. The same core has not been specifically treated for becoming a fast disintegrating core and disintegrates in a very long time period which causes clogging of the drain lines.

Furthermore, it has been found that a core produced according to a method of the present invention disintegrates in water in similar time period and shows similar mechanical strength properties as the water disintegrating cores produced with extra starch.

Alkali salt of carboxymethyl cellulose used in a method according to the present invention is soluble in cold water. The molecular weight of sodium salt of carboxymethyl cellulose is from about 150,000 MW; molecular weight to about 400,000 MW, and preferably from about 250,000 MW to about 3000,000 MW. In a preferred embodiment, viscosity of the sodium salt of carboxymethyl cellulose is from about 100 MPa-s to about 1000 MPa-s, and preferably from about 300 MPa-s to about 800 MPa-s, and more preferably from about 400 MPa-s to about 700 MPa-s of %2 aqueous solution of alkali metal salt of carboxymethyl cellulose at 25°C. The degree of substitution of the sodium salt of carboxymethyl cellulose is from about 0.6 to about 1.2, and more preferably about 0.6 to 1. The pH value of of sodium metal salt of carboxymethyl cellulose is 5 or more.

The cellulose fibers used in a method according to the present invention have a fiber length of 0.4 - 2 mm, preferably 0.5 - 1.5 mm, and more preferably 0.6- 1 mm.

Cellulosic fibres suitable for making the core of the present invention may include: hardwood fibres, such as Eucalyptus, maple, birch, aspen, redgum or the like. Preferred fibre type of the present invention examples is eucalyptus tree fibres.

According to the present invention a polyvinyl acetate based adhesive is used in the manufacturing of core for adhering cardboard sheets to one another. The adhesive used in the present application may comprise, PVA based copolymer adhesives, starch, polyvinyl alcohol, and dextrin or mixtures thereof. Preferred adhesive is polyvinyl acetate. The method of the present invention product may comprise application of additional agents, such as cleaning agents, disinfectants or fragrances. These additives can be applied by any methods known from state of the art.

The water disintegrable core produced by a method according to the present invention can be used as a support in paper product rolls such as toilet paper rolls, paper towel rolls, or the like.

EXAMPLES

EXAMPLE 1 : Preparation of water disintegrating core

285 gr of eucalyptus cellulose fibers are disintegrated under stirring in 2 It of water at 12,5% consistency at 10000 RPM to obtain a pulp having fibers with an average length of 0.7 mm. While obtaining said pulp, a 1 % aqueous solution of sodium salt of carboxymethyl cellulose is prepared by adding 28,5 gr of water to 0,285 gr of sodium salt of carboxymethyl cellulose. Obtained aqueous solution of sodium salt of carboxymethyl cellulose is added to the pulp. The pulp mixture is diluted to 4,7% consistency by adding 5750 ml of water. 638 ml of the obtained pulp is diluted to 0,2% consistency by adding 15000 ml of water. Thus obtained 4750 ml of the pulp having a consistency of 0,2 is transferred to the Rapid Kothen Sheet Former for production of handsheets by removing excess water by sieving and subsequent drying at 90°C. Thus, a cardboard sheet having a basis weight of between 280-320 g/m2 is prepared in coil.

Obtained cardboard sheet is cut to appropriate size, spirally winded around itself and sidelongs adhesively bonded with a polyvinyl acetate based adhesive to form the hollow tube. Cutting of hollow tube in appropriate size delivers the water disintegrating core of the present invention with only one cardboard sheet.

EXAMPLE 2: Preparation of Water Disintegrating Core with Two Cardboard Sheets

Cardboard sheets are produced according to Example 1 in coils. One cardboard sheet coil is cut in 85 mm width and another cardboard sheet is cut in 90 mm width. One side of a cardboard sheet is smeared with a polyvinyl acetate based adhesive. Said coils are adhesively bonded to each other one on the top of the other to obtain a cardboard coil with two cardboard sheets. Immediately thereafter said cardboard coil is spirally winded with subsequent forming of a hollow tube. Cutting of the hollow tube in appropriate size delivers the water disintegrating core of the present invention with two cardboard sheets.

TEST METHODS

1 : Core Disintegration Time Tests 5 g of a sample core is put in 2 It of water while mechanically stirring with a spatula. Start time of loosening of web and complete disintegration time of web are recorded.

Table 1 : Measured Disintegration Times of Present Invention Examples and Related Prior Art Samples

As can be seen Ex 1 and Ex 2 core disintegration times are very similar and show close similarity with the starch containing disintegrating core. Starch containing core sample is provided from market. These cores are prepared by impregnation of starch solutions into cellulose web. Regular cores are the ones that made with the regular cellulose web. As regular cores made from this material, these are not disintegrating even within a few days and therefore prone to clogging the sewer pipe.

Consequently with the present invention method prepared cores are disintegrating in proper disintegration times and as fast as in market available starch containing disintegration cores. The present invention products are having the advantage of eliminating the need of use of big amounts of starch and high number tissue layers, therefore simple, feasible and economically advantageous. 2: Strength Tests

A: Physical Strength Test:

A ply of 5x2 cm dimension is clamped by two clamps of the test device and a drawing force is applied onto the ply. The sample cores of present invention are compared with regular core with regard to its physical strength. According to the results obtained the present invention samples are sufficiently strong in comparison to the results obtained regulare core and fulfill market requirements. Cardboard Type | Weight j Thickness | MD Dry Strength j CD Dry Strength |

(gr/m2) (mm) (N/m) (N/m)

I Regular Core | 140 | 0,21 | 5297 j 2437 | Board (One ply) j | \ j

| Core Board of the | 160 | 0,39 j 3147 | 1973 | present invention | [ | j | (One ply) I I I I I

B: Compression Tests: The sample cores of present invention are compared with starch containing core and regular core with regard to its compressive strength by applying a force of weight vertically and horizontally (Box compression test (ISO 12048, ASTM D 642)).

The present invention samples are sufficiently strong against vertical and horizontal pressure applied to a core during manufacturing, storage and transportation, therefore fulfill market requirements.