HK40000646B - Coreless roll of absorbent sheet and method for manufacturing the same - Google Patents

Description

Coreless roll of absorbent sheet and method for producing the same

Technical Field

The present invention relates to a coreless roll of absorbent sheet products such as napkins, toilet paper, paper towels, etc. In one aspect of the present invention, the coreless roll is provided in a compressed form. The present invention also relates to a method for making the coreless roll.

Background Art

Rolls of absorbent sheet products are widely used in modern society. Rolls of toilet paper, towels, such as household (kitchen) paper towels or hand towels, are staple items of commerce.

Rolls of household absorbent sheet products, such as toilet paper, typically consist of a continuous web of absorbent material spirally wound onto a prefabricated core made of a rigid material such as cardboard or glued paper. The core defines an axial hollow channel that is centrally located relative to the roll and extends from one edge of the roll to the other. This axial hollow channel enables the consumer to easily mount the roll on the spindle of a roll holder. However, such cores are expensive, require storage space, and require additional manual handling. Furthermore, the core remains after the absorbent sheet product has been used, thereby increasing the risk of blockage in sewage systems.

To solve these problems, "coreless" rolls and rolls with water-soluble cores have been developed. The most important properties of these products are their resistance to collapsing and their flexibility/elasticity.

"Slump" refers to a phenomenon that occurs when the absorbent sheet product that makes up the first inner coil of a roll (i.e., the coil that forms the axial hollow channel at the beginning of winding) is no longer stably held so that the axial hollow channel is clearly defined. Coreless rolls are often associated with an increased risk of "slump." Collapse typically occurs during the coreless roll manufacturing process, when the temporary core is removed after winding is complete, or during storage and transportation of the finished product. Collapse can make it difficult to mount the roll on the spindle of the roll holder. Furthermore, collapse often creates a perception among consumers that the product is of lower quality.

The advantage of a "pliable" roll is that it can be provided in a compressed form, which requires less space during storage and transportation. As a result, storage and transportation costs can be significantly reduced. The roll can be returned from its compressed (elliptical) form to its uncompressed (cylindrical) form by applying pressure along the longer diameter of the compressed (elliptical) form (i.e., perpendicular to the axis of the roll).

However, when the roll returns from its compressed to uncompressed form, the absorbent sheet product comprising the first inner coil must be stably retained. That is, the axial hollow channel must open and remain clearly defined as the roll returns to its cylindrical shape. Therefore, the roll must possess flexibility and a certain level of elasticity, allowing the axial hollow channel to reopen in a clearly defined manner as the roll returns to its cylindrical shape. This requires the first inner coil to re-open and stably retain the axial hollow channel. As a result, there should be no noticeable difference in appearance between the roll returning from its compressed to uncompressed form and the roll that was not previously compressed.

The prior art describes methods for obtaining flexible rolls of absorbent sheet products that can be provided in compressed form.

WO 2009/027874 A1 discloses a roll consisting of a nonwoven tissue web spirally wound around a flexible core. The flexible core is composed of a polymer sheet of a synthetic polymer, which is connected to the inner layer of the nonwoven tissue web by a connecting mechanism such as an adhesive, thermal bonding, etc. The flexible core is characterized in that the tensile strength in the machine direction is higher than the tensile strength of the nonwoven tissue web. As a result, the roll has flexibility for packaging and storage purposes.

However, polymer sheets made of synthetic polymers must be prepared, stored, and handled manually. Furthermore, during industrial production, the continuous web of absorbent material travels at speeds of approximately 10 m/s. This makes the introduction and connection of the polymer sheet to the inner layer of the nonwoven tissue web technically complex and difficult to implement at the speeds required for industrial production.

WO 95/13183 A1 discloses a roll of elongated material having a core at the center of the roll. The core is essentially made of a plurality of coils of elongated material, which are fixed together by adhesives such as polyvinyl acetate, polyacrylate, latex, starch, polyvinyl alcohol, etc. WO 95/13183 A1 also discloses a method for manufacturing such a roll in a compressed form. More specifically, WO 95/13183 A1 shows that an adhesive solution is sprayed or applied to the first coil of conventional winding. After being fully wound and removed from the reel, the roll is immediately compressed into an elliptical or oval cross-sectional form. The document teaches that the roll can be opened from a compressed position by applying pressure on the "shorter" side of the ellipse.

However, adhesives such as those described in WO 95/13183 A1 (e.g., latex, starch, polyvinyl alcohol, etc.) produce a rigid core consisting of many coils of glued-together elongated material. Consequently, the resulting core lacks flexibility and exhibits low elasticity. Consequently, after the coil has been compressed, it is difficult to reopen the axial hollow channel in a manner that results in a well-defined axial hollow channel.

Furthermore, the first inner loop of elongated material (i.e., the loop of elongated material forming the core) is held together by adhesive adhesion. The peel force required to separate the first inner loop is typically greater than the tear strength of the elongated absorbent material. Consequently, it is difficult to separate the first inner loop without tearing the elongated absorbent material to which the adhesive is applied. Consequently, it is impossible to use the elongated absorbent material along its entire length, for example, up to the final sheet.

WO2011/126707A2 discloses a water-based adhesive for roll paper, which comprises (A) saccharide, (B) viscosity modifier and (C) diol and/or triol. It is said that the adhesive of WO2011/126707A2 has good initial adhesion when wet and has good peeling ability when dry. However, due to the presence of saccharide, the paper on which the adhesive is applied shows a certain rigidity. As a result, the roll paper product lacks flexibility and, after the roll is compressed, it is difficult to reopen the axial hollow channel in a manner that causes a clearly defined axial hollow channel. In addition, the adhesive contains viscosity modifier (B) as an essential component. According to the teaching of this application, viscosity modifier (B) can be selected from polyvinyl pyrrolidone polymers with a weight-average molecular weight in the range of 25,000 to 400,000 and/or oxyalkylene polymers such as polyethylene oxide (PEO) with a weight-average molecular weight in the range of 300,000 to 3,500,000. PEO with such high molecular weight is neither particularly elastic nor water soluble.

Furthermore, since paper materials generally have a good absorption capacity for liquids, it is often difficult to dry out the water contained in the adhesive, so the final roll product is never completely dry. As a result, the paper material to which the adhesive is applied exhibits a certain stickiness, which creates an unpleasant feeling among consumers.

It is therefore an object of the present invention to provide a coreless roll of absorbent sheet product that combines excellent collapse resistance with improved flexibility and resiliency.

Another object of the present invention is to provide a roll of absorbent sheet product that can be used over substantially its entire length (ie substantially up to the last sheet) and prevents clogging of sewage systems.

According to a further preferred aspect of the present invention, the coreless roll of the absorbent sheet product may be provided in a compressed form, wherein after the roll has been compressed the axial hollow channels may be reopened in such a way that well-defined axial hollow channels are generated.

Another object of the present invention is to provide a method for making coreless rolls of such absorbent sheet products.

Summary of the Invention

The present invention relates to a coreless roll of absorbent sheet product, such as napkins, toilet paper, paper towels, etc., made from a continuous web of absorbent material having a first end and a second end, the continuous web of absorbent material being wound to define an axial hollow channel centrally located relative to the coreless roll and extending from one edge to the other of the coreless roll, with the first end being located on the outside of the roll and the second end being located in the axial hollow channel;

Wherein the continuous web of absorbent material comprises a coating composition comprising a specific polymer, the continuous web of absorbent material comprising the coating composition is preferably obtained by applying the coating composition to the second end.

The present invention also relates to such coreless rolls provided in a compressed form.

The present invention also relates to a method for producing a coreless roll of an absorbent sheet product, comprising the following steps: - conveying a continuous web of absorbent material having a first end and a second end, said continuous web preferably consisting of one tissue paper ply or 2 to 6, in particular 2 to 5, superimposed tissue paper plies;

- applying a coating composition comprising a specific polymer to said second end;

- spirally winding the continuous web of absorbent material to produce a log of web of absorbent material, winding the continuous web of absorbent material to define an axial hollow channel centrally located with respect to the log and extending from one edge to the other of the log, with the first end being located outside the log and the second end being located within the axial hollow channel;

- cutting the log into a plurality of coreless rolls;

- Optionally, compressing the coreless roll in a direction perpendicular to the axial hollow channel to produce a coreless roll in a compressed form.

In one aspect of the present invention, the polymer used in the coating composition of the present invention has:

(i) a glass transition temperature of less than 20°C, preferably less than 15°C, more preferably less than 10°C, more preferably less than 5°C, more preferably less than 0°C, more preferably less than -5°C, more preferably less than -10°C; and

(ii) a melting point greater than 20°C, more preferably greater than 25°C, more preferably greater than 30°C, more preferably greater than 35°C, more preferably greater than 40°C, more preferably greater than 45°C.

In another aspect of the present invention, the second end of the continuous web of absorbent material comprises a coating composition comprising a specific polymer, the second end comprising said coating composition preferably being obtained by applying a coating composition comprising said polymer to the second end, wherein said polymer has:

(i) a glass transition temperature below 0°C, preferably below -5°C, in particular below -10°C; and

(ii) a melting point greater than 35° C., preferably greater than 40° C., in particular greater than 45° C.,

(iii) optionally having a solubility in water at 25°C of at least 40 g/l.

In another aspect of the present invention, the continuous web of absorbent material comprises a coating composition comprising a specific polymer, and the continuous web of absorbent material comprising the coating composition is preferably obtained by applying a coating composition comprising a polymer represented by the following formula to the second end:

However, in the above formula, n represents an integer having an average value of 10 to 5000, preferably 10 to 2500, more preferably 20 to 1000, more preferably 30 to 200, more preferably 50 to 150 or 50 to 100.

The coreless roll of the absorbent sheet product of the present invention is characterized by its excellent resistance to collapse, as well as its excellent flexibility and elasticity. In addition, the coreless roll of the present invention also exhibits excellent disintegration in water and can be used over its entire length.

The present invention includes the following embodiments ("items"):

1. A coreless roll of absorbent sheet product, formed from a spirally wound continuous web of absorbent material having a first end and a second end, the web of absorbent material being wound to define an axial hollow channel centrally located relative to the coreless roll and extending from one edge to the other of the coreless roll, with the first end being located on an outside of the roll and the second end being located within the axial hollow channel;

wherein the continuous web of absorbent material comprises a coating composition comprising a polymer, wherein the polymer has:

(i) a glass transition temperature of less than 20°C, preferably less than 15°C, more preferably less than 10°C, more preferably less than 5°C, more preferably less than 0°C, more preferably less than -5°C, more preferably less than -10°C; and

(ii) a melting point greater than 20°C, more preferably greater than 25°C, more preferably greater than 30°C, more preferably greater than 35°C, more preferably greater than 40°C, more preferably greater than 45°C.

(In this embodiment, the difference between the glass transition temperature and the melting point is preferably at least 10°C, more preferably at least 15°C, more preferably at least 20°C, more preferably at least 35°C, even more preferably at least 50°C)

2. The coreless roll according to item 1, wherein the second end of the continuous web of absorbent material comprises the coating composition, and wherein the polymer has:

(i) a glass transition temperature below 0°C, preferably below -5°C, more preferably below -10°C; and

(ii) a melting point greater than 35°C, preferably greater than 40°C, more preferably greater than 45°C, and

(iii) optionally having a solubility in water at 25°C of at least 40 g/l.

3. The coreless roll according to item 2, wherein the coreless roll is obtained by applying the coating composition to the second end of the continuous web of absorbent material.

4. A coreless roll of an absorbent sheet product, formed from a spirally wound continuous web of absorbent material having a first end and a second end, the web of absorbent material being wound to define an axial hollow channel centrally located relative to the coreless roll and extending from one edge to the other edge of the coreless roll, with the first end being located on an outside of the roll and the second end being located within the axial hollow channel;

wherein the continuous web of absorbent material comprises a coating composition comprising a polymer, wherein the polymer conforms to the following formula:

However, in the above formula, n represents an integer having an average value of 10 to 5000, preferably 10 to 2500, more preferably 20 to 1000, more preferably 30 to 200, more preferably 50 to 150 or 50 to 100.

5. The coreless roll of item 4, wherein the second end of the continuous web of absorbent material comprises the coating composition.

6. The coreless roll according to item 5, wherein the coreless roll is obtained by applying the coating composition to the second end of the continuous web.

7. The coreless roll of any one of items 1, 2, 3, 4, 5, or 6, wherein the coating composition comprises:

(a) at least 50 wt%, preferably at least 65 wt%, more preferably at least 80 wt% of said polymer;

(b) not more than 50 wt %, preferably not more than 35 wt %, more preferably not more than 20 wt % of other additives such as plasticizers, reinforcing agents, fragrances and dyes;

(c) optionally water in an amount of no greater than 10 wt%, preferably no greater than 5 wt%; each based on the total weight of the coating composition.

8. The coreless roll of any one of items 1, 2, 3, 4, 5, 6 or 7, wherein the coating composition is applied in the form of a melt or in the form of an aqueous solution after addition of water.

9. The coreless roll according to any one of items 1, 2, 3, 7 or 8, wherein the polymer is a polyether polyol, preferably a polyether polyol selected from polyethylene glycol, polypropylene glycol and mixtures thereof, more preferably polyethylene glycol.

10. The coreless roll of any one of items 1, 2, 3, 4, 5, 6, 7, 8 or 9, wherein the polymer has a number average molecular weight of 800 to 250,000, preferably 1,000 to 50,000, more preferably 1,500 to 15,000, more preferably 1,500 to 10,000, more preferably 2,000 to 7,500, for example 2,500 to 4,000.

11. The coreless roll of item 9 or 10, wherein the polymer is polyethylene glycol having a number average molecular weight of 800 to 250,000, preferably 1,000 to 20,000, more preferably 1,500 to 10,000, more preferably 2,000 to 7,500, more preferably 2,500 to 6,500, even more preferably 2,500 to 4,000.

12. The coreless roll of any one of items 1 to 11, wherein the coating composition does not contain sugars.

13. A coreless roll according to any one of items 1 to 12, wherein the axial hollow channel has a circumference, the coating composition is applied circumferentially, and preferably applied so that the resulting coating covers at least 10% of the second end, preferably at least 20% of the second end, preferably at least 50%, even more preferably at least 75%, for example at least 95%.

14. The coreless roll of any one of items 1 to 13, wherein the coating composition is applied continuously in the machine and axial directions, or intermittently in the machine and/or axial directions.

15. The coreless roll of any one of items 1 to 14, wherein the second end consists of at least one turn, preferably at least 2 turns, more preferably at least 3 turns, for example 3 to 50 turns, for example 3 to 30 turns or 4 to 40 turns, preferably 3 to 30 turns, one turn being one loop of the continuous web spirally wound around the axial hollow channel.

16. The coreless roll according to any one of items 1 to 15, wherein the amount of polymer is 0.1 to 20 g/roll, preferably 0.1 to 10 g/roll, more preferably 0.1 to 5 g/roll, especially 0.5 to 2 g/roll.

17. The coreless roll according to any one of items 1 to 16, wherein the web of absorbent material consists of one tissue layer or 2 to 6, in particular 2 to 5, superimposed tissue layers.

18. The coreless roll of any one of items 1 to 17, which is in compressed form.

19. The coreless roll according to any one of items 1 to 18, which is an absorbent product selected from the group consisting of napkins, towels such as household towels, kitchen towels or hand towels, toilet paper, wipes, handkerchiefs and facial tissues, wherein the absorbent product is preferably toilet paper.

20. A method for producing a coreless roll of an absorbent sheet product, comprising the steps of:

- transporting a continuous web of absorbent material having a first end and a second end, the continuous web preferably consisting of one tissue layer or 2 to 6, in particular 2 to 5, superimposed tissue layers;

- optionally, cutting the continuous web of absorbent material substantially transversely to the machine direction to produce individual but connected sheets;

- applying a coating composition as defined in any one of items 1 to 16 to the second end;

- spirally winding the continuous web of absorbent material to produce a log of absorbent material web, the web of absorbent material being wound so as to define an axial hollow channel centrally located with respect to the log and extending from one edge to the other of the log, with the first end being located on the outside of the log and the second end being located in the axial hollow channel;

- Cutting the log into a plurality of coreless rolls.

21. The method of claim 20, further comprising the following step:

- Compressing the coreless roll in a direction perpendicular to the axial hollow channel to produce a coreless roll in a compressed form.

22. Use of the coreless roll according to any one of items 1 to 18 as toilet paper, household towels, kitchen towels, wipes, facial tissue, handkerchiefs or napkins.

Insofar as the present description refers to “preferred” embodiments/features, combinations of these “preferred” embodiments/features are also to be considered disclosed, insofar as these combinations of “preferred” embodiments/features are technically meaningful.

Hereinafter, in the present description and claims of the invention, the use of the term "comprising" is to be understood as disclosing the term "consisting of" as a more restricted embodiment, insofar as this makes technical sense.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 - shows a schematic diagram in perspective view of a coreless roll according to the invention.

Figure 2 - Schematic diagram showing a side view of a coreless roll according to the invention. The second end as shown in Figure 2 has three loops.

Figure 3 - Schematic representation of the second end of an unwound continuous web of absorbent material according to the present invention. The grey shading in Figure 3 represents the coating composition that is continuously applied to the second end.

Figures 4a and 4b - Schematic representation of the second end of an unwound continuous web of absorbent material according to the present invention. The grey shading in Figures 4a and 4b represents the coating composition intermittently applied to the second end as stripes and dots respectively.

Figures 1 to 4 give an overview of the terminology used in relation to the coreless roll of the present invention. In Figures 1 to 4, the following reference numerals indicate:

(1) Coreless roll

(2) A continuous web of spirally wound absorbent material

(3) Axial hollow channel

(4) Edge

(5) First end

(6) Second end

(7) Coating composition

(8) Punch line

Figure 5 - Schematic diagram showing a cross-sectional view of a converting machine (9) illustrating the production of a coreless roll according to one embodiment of the present invention. Figure 5 shows the application of a coating composition to a continuous web of absorbent material by spraying.

Figure 6 - shows a schematic diagram of a cross-sectional view of a processing machine (9) illustrating the production of a coreless roll according to another embodiment of the present invention. Figure 6 shows the application of a coating composition to a continuous web of absorbent material by roller coating.

DETAILED DESCRIPTION

1. Coreless roll

The coreless roll of the absorbent sheet product of the present invention is made from a spirally wound continuous web of absorbent material having a first end and a second end.

The continuous web of absorbent material is preferably made of base tissue paper, which can be obtained by conventional wet pressing or through-air drying (TAD) manufacturing methods or other manufacturing methods. As "base (original) tissue paper"("tissue paper web"), we understand a single-ply base tissue paper obtained from a tissue paper machine. The base tissue paper has a low basis weight in the range of 10-60 g/ ^m2 , preferably 10-30 g/ ^m2 .

The term "ply" as used herein refers to one or more layers of tissue paper in a final tissue product (eg toilet paper) obtained after processing ("converting") one or more base tissue paper webs.

Based on the potential compatibility of the manufacturing method (wet forming), it is considered as "tissue" in papermaking technology. The production of tissue paper is distinguished from paper production by its extremely low basis weight and significantly higher tensile energy absorption index.

The tensile energy absorption index is derived from the tensile energy absorption, which is related to the volume of the test specimen prior to testing (length, width, and thickness of the specimen between the grips before tensile loading). Paper and tissue also typically differ in their elastic modulus, a material parameter that characterizes the stress-strain properties of these planar products.

The high tensile energy absorption index of tissue paper results from either external or internal creping. The former is caused by the compression of the paper web adhered to the drying cylinder by the action of the creping blade, or in the latter case by the speed difference between two wires ("fabrics"). This causes the still moist, plastically deformable paper web to break up internally by compression and shearing, making it more stretchable under load than uncreped paper. A high tensile energy absorption index can also be achieved by imparting a 3D structure to the tissue paper with the help of the wires themselves. Most of the typical functional properties of tissue paper and tissue paper products come from a high tensile energy absorption index (see DIN EN 12625-4 and DIN EN 12625-5).

Typical properties of tissue papers include their ready ability to absorb tensile stress energy, their drapability, good fabric-like flexibility, often referred to as overall softness, high surface softness, high specific volume with appreciable thickness, and high liquid absorbency, as well as, depending on the application, suitable wet and dry strength and an interesting visual appearance of the product's outer surface. These properties allow the use of tissue papers, for example, as cleaning cloths (e.g., household towels), hygiene products (e.g., toilet paper, hand towels) and wipes (e.g., cosmetic wipes, facial tissues).

According to one embodiment of the invention, the continuous web of absorbent material preferably consists of 1 tissue layer or 2 to 5 superimposed tissue layers.

Tissue paper can be made from papermaking fibers according to the "conventional process", such as the production of "dry-laid creped tissue" or "wet-laid creped tissue" or "structured tissue processes", such as the through-air drying (TAD) production process, the production of uncreped through-air drying (UCTAD) tissue, or alternative production processes, such as Voith's Advanced Tissue Molding System (ATMOS), Georgia Pacific's Energy Efficient Technologically Advanced Drying eTAD, or Metso Paper's Structured Tissue Technology SST. Hybrid processes such as NTT (New Textured Tissue), which are modifications of the conventional process, can also be used.

The conventional dry creping manufacturing method includes the following steps:

- pressing and drying the wet paper fibers in sheet form on large diameter heated cylinders (also known as Yankee dryers); and

- The dried paper fiber sheet is then separated and creped by means of a metal doctor blade applied relative to the cylinder, crosswise to the direction of rotation of the cylinder.

The creping operation creates undulations in the sheet crosswise to its direction of travel. The creping operation increases the thickness of the sheet, imparts elasticity to the sheet and gives it contact properties (soft touch).

The TAD manufacturing method comprises the following steps:

- molding a sheet of wet paper fibers onto the fabric; and

- The sheet is then at least partially dried by passing a stream of hot air through it.

The dried sheet may then be creped.

Furthermore, in the production of tissue webs (a preferred embodiment of the continuous absorbent material web to be used), the method described in PCT/EP2015/059326 (filing date: April 29, 2015; title: "Tissue paper comprising pulp fibers originating from Miscanthus and method for manufacturing the same," incorporated herein by reference) can be used. Specifically, reference is made to the description of Item 3 on pages 22 to 27 of that application and the details of the TAD process disclosed therein (e.g., 3-D shaped fabrics, permeable drying cylinders, etc.). The parameters described in that paragraph are also valid for use with ATMOS technology.

Once tissue paper is manufactured, a unique manufacturing operation known as a converting operation is typically employed to form tissue products (i.e., paper towels, toilet paper rolls, bathroom tissue, wipes, kitchen paper rolls, handkerchiefs, etc.).

In another embodiment of a continuous web of absorbent material, the absorbent material is a "nonwoven." The term "nonwoven" is commonly used in the art and can be further defined in the manner described in ISO 9092:2011, also for the purposes of the present invention. Typical nonwoven manufacturing technologies include air-laid, spunbond, dry-laid, and wet-laid long-fiber technologies. The nonwoven web used in accordance with this embodiment can be a single-layer or multi-layer web.

According to a preferred aspect of this embodiment, the web based on absorbent nonwoven material used for the coreless roll of the present invention comprises cellulosic fibers. In this case, the content of cellulosic fibers is at least 20 wt%, more preferably at least 50 wt%, for example at least 80 wt%, based on the total weight of all fibers present in the nonwoven web. In these cases, the remaining fibers are non-cellulosic fibers, such as synthetic fibers.

The above-mentioned papermaking fibers (which may also be referred to as "cellulose fibers") can be made from virgin and/or recycled pulp raw materials. The cellulose fibers useful in the present invention generally contain, as the primary structural component, long-chain fibrous cellulose moieties present in naturally occurring cellulose-containing cells, particularly those of lignified plants. Preferably, the fibers are isolated from lignified plants by a digestion step to remove or reduce the content of lignin and other extractables, and an optional bleaching step. The cellulose fibers may also be derived from non-wood sources, such as annual plants.

Suitable cellulose fibers that can be used can be regenerated types (e.g., Lyocell), although other types of pulp are preferably used. The pulp used can be a primary fiber material ("virgin fiber") or a secondary fiber material (regenerated pulp). The pulp can come from a source that does not contain lignin or has low lignin, such as cotton linters, esparto grass (alfa), bagasse (e.g., cereal straw, rice straw, bamboo, or hemp), kemp fibers, miscanthus fibers, or flax (also referred to as "non-wood fibers" in the specification and claims). Preferably, the pulp is made of lignocellulosic material such as softwood (usually derived from conifers) or hardwood (usually from deciduous trees).

Either "chemical pulp" or "mechanical pulp" can be used, with chemical pulp being preferred.

According to DIN 6730, "chemical pulp" is a fibrous material obtained from plant raw materials, from which most non-cellulose components have been removed by chemical pulping without substantial mechanical aftertreatment. "Mechanical pulp" is a general term for fibrous materials produced entirely or almost entirely from wood by mechanical means, optionally at elevated temperatures. Mechanical pulp can be subdivided into purely mechanical pulps (groundwood pulp and refined mechanical pulp) and chemically pretreated mechanical pulps, such as chemimechanical pulp (CMP) or chemi-thermomechanical pulp (CTMP).

In the present invention, referring to Figures 1 and 2, a continuous web (2) of absorbent material is spirally wound to define an axial hollow channel (3) located centrally relative to the roll (1) and extending from one edge (4) of the roll to the other edge (4). As "axial hollow channel", we understand a tubular opening extending through the roll along its central axis. The axial hollow channel enables the end user to mount the roll on the spindle of a roll support. When the roll is mounted on the spindle of the roll support, the absorbent material is dispensed from a first end (located outside the roll) while allowing the roll to rotate freely about its central axis. The axial hollow channel has a diameter of 10 mm to 70 mm, preferably 20 mm to 50 mm.

In the present invention, the axial hollow channel (3) extends from one edge (4) to the other edge (4) of the coreless roll. The coreless roll of the present invention has a cylindrical circumferential surface and opposite flat ends (i.e., edges) formed when the log is cut into multiple rolls at the end of the winding process. Therefore, as "edge", we understand the flat portion located on one side of the roll perpendicular to its central axis.

In the present invention, the continuous web (2) of absorbent material has a first end (5) and a second end (6). The first end (5) is located outside the roll, and the second end (6) is located in the axial hollow channel (3). Therefore, the continuous web of absorbent material consists of the first end and the second end and the middle part located between these ends in the machine direction. The combined length of the first end, the second end and the middle part defines the length of the continuous web of absorbent material forming one roll. In the coreless roll of the present invention, the continuous web of absorbent material comprises the coating composition specified in the present application. The continuous web of absorbent material is preferably obtained by applying the coating composition to the second end. This results in a continuous web of absorbent material in which the remaining part (i.e. the first end and the middle part) is preferably substantially or completely free of the coating composition. Therefore, the obtained continuous web of absorbent material can be distinguished from known continuous webs of absorbent material (e.g., lotion toilet paper) in which the same coating composition (e.g., lotion) is applied to the entire continuous web.

However, this does not exclude applying a coating composition in the sense of the invention to a second end of the continuous web of absorbent material while additionally applying a washing liquid (which must be different from the coating composition) to one side of the entire continuous web of absorbent material.

Other embodiments of coreless roll manufacturing that also use the concepts of the present invention relate to a continuous web of absorbent material obtained by applying a coating composition to its second end, wherein a portion of the remaining portion (i.e., the first end and the middle portion), preferably less than 20%, more preferably less than 10%, and more preferably less than 5% of the total area of the remaining portion, also carries said coating composition.

In one embodiment, the second end (6) consists of at least one turn, preferably at least two turns, more preferably at least three turns, for example 3 to 50 turns, for example 3 to 30 turns or 4 to 40 turns, preferably 3 to 30 turns. As a "turn", we understand one turn of the continuous web wound helically around the axial hollow channel. Figure 2 shows, for example, three turns at the second end (6) of the web.

In one embodiment, the coreless roll of the present invention is provided in a compressed form. By "compressed form," we understand a roll having an elliptical cross-section. When the roll is in compressed form, the axial hollow channel assumes the form of a thin, generally elliptical slit and no longer accommodates the shaft of the roll holder. As a result, the roll requires less space, and storage and transportation costs can be reduced. The coreless roll of the present invention can be returned from the compressed (elliptical) form to the uncompressed (cylindrical) form by applying pressure along the longer side (diameter) of the elliptical roll, i.e., perpendicular to the roll axis.

2. Coating composition

In the present invention, a coating composition comprising a specific polymer is preferably applied to the second end of the continuous web of absorbent material. The specific polymer is described in more detail in Section 2.1 below. Thus, the polymer may be characterized by properties (i), (ii), and preferably (iii), or may be defined by formula (I).

In one embodiment, the coating composition useful in the present invention comprises:

(a) at least 50 wt%, preferably at least 65 wt%, more preferably at least 80 wt%, more preferably at least 85 wt%, more preferably at least 90 wt%, more preferably at least 95 wt% of said polymer;

(b) no more than 50 wt %, preferably no more than 35 wt %, more preferably no more than 20 wt %, more preferably no more than 15 wt %, more preferably no more than 10 wt %, more preferably no more than 5 wt % of other additives such as plasticizers, reinforcing agents, fragrances and dyes;

(c) optionally water in an amount of not more than 10 wt %, in particular not more than 5 wt %;

Each is based on the total weight of the coating composition.

In another embodiment, the coating composition consists of these ingredients in the indicated amounts.

In a preferred embodiment, the coating composition consists of at least 95 wt%, preferably at least 98 wt% of the polymer and optionally water in an amount of not more than 5 wt%, preferably not more than 2 wt%. In a further preferred embodiment, the coating composition consists of the polymer.

The coating composition can be applied in the molten state to the continuous web of absorbent material (particularly its "second end") after heating to a temperature equal to or above the specified melting point, for example by spraying, roller coating, slot die application or any other suitable application method known in the art.

In another preferred embodiment, the coating composition is applied as an aqueous solution. This means that water is added to the coating composition and serves as a solvent for the polymer and other additives (if present). The aqueous solution of the coating composition preferably contains the polymer in an amount of at least 5 wt%, preferably at least 10 wt%, and more preferably at least 30 wt%, based on the total weight of the aqueous solution.

Water is preferably present in an amount greater than 20 wt%, more preferably greater than 35 wt%, more preferably greater than 50 wt%, based on the total weight of the aqueous solution.

The aqueous solution of the coating composition may be applied as is (preferably at room temperature) to the continuous web of absorbent material (particularly the "second end" thereof), for example by spraying, rolling or any other suitable application method known in the art.

After application of the aqueous solution, the continuous web of absorbent material may be dried, for example by prolonged storage under ambient conditions or other suitable techniques known in the art. Depending on the water content, such a drying step may not be necessary, as the web of absorbent material will itself remove water from the aqueous solution, leaving the coating composition on the web.

In a preferred embodiment, the coating composition of the present invention does not contain carbohydrates. The term "saccharide" should be understood broadly and includes monosaccharides, disaccharides, oligosaccharides (at least 3 saccharide units) and polysaccharides such as starch or cellulose, as well as carbohydrate-based polymers such as cellulose ether derivatives such as carboxymethylcellulose (CMC) and methylcellulose.

In the present invention, the coating composition is applied to at least one of the two sides of the continuous web, i.e., the upper and/or lower side of the continuous longitudinal web, or between the base tissue layers forming the web. The "upper" side is understood to be the side of the continuous web that faces the outside of the roll when the web is spirally wound. In a preferred embodiment, the coating composition is applied to the lower side, i.e., the side facing the axial hollow channels.

The coating composition is preferably applied to the continuous web before it is spirally wound to form a roll. As a result of the winding, the coating composition is applied circumferentially relative to the axial hollow channel. In the present invention, the coating composition is preferably applied to the web in such a manner that at least 50%, preferably at least 75%, and in particular at least 95% of the total area of the second end (i.e., the area bearing the resulting coating) is coated.

If the coating is applied to the second end of the web intermittently in the machine and/or axial direction, e.g. with respect to individual turns of the web around the axial hollow channel, i.e. when viewed from the edge of the roll, if one or more turns are not completely coated, it is also preferred that the area with the resulting coating accounts for at least 10% of the total area of the second end, preferably at least 20% of the total area, more preferably at least 35%, more preferably at least 50% of the total coated area, preferably at least 75% and in particular at least 95% of the total area of the second end.

In the present invention, the coating composition may be applied to the second end of the continuous web to provide a full or partial coating. By "full coating" we understand a coating that is applied continuously in the machine and axial (cross) directions, i.e., the second end of the web does not include any uncoated portion (see, e.g., FIG3 ).

By "partial coating," it is understood that the coating composition is applied to a continuous web in such a manner that it partially covers the surface of the web (i.e., its second end). For example, partial coating occurs if the coating is applied intermittently in the machine and/or axial directions to the second end of the web. The coating composition can be applied to the web to form a predetermined coating pattern. There are no particular limitations on the predetermined coating pattern. The partial coating can form continuous (e.g., stripes, lines, or ripples) or discrete deposits (e.g., dots, squares, circles, or any other geometric shape).

In one embodiment of the partial coating, the coating is applied intermittently in the machine and/or axial direction, e.g.

- continuously in the machine direction, but intermittently in the axial (cross) direction, for example in the form of one or more parallel stripes extending in the machine direction (see for example Figure 4a).

- continuously in the axial (cross) direction, but intermittently in the machine direction, for example in the form of one or more parallel stripes extending in the axial direction, i.e. from one edge of the roll to the other,

- intermittently in the machine and axial (cross) directions, for example in the form of parallel stripes crossing each other.

In one embodiment of partial coating, as shown in Figure 4b, the coating is applied intermittently in the form of dots. The dots may form a regular or irregular pattern as a result of, for example, spraying or roller coating.

In one embodiment, the coating composition is applied intermittently so as to cover at least 35% of the second end surface, preferably at least 50% of the second end surface, more preferably at least 75%, for example at least 95% of the total second end surface.

2.1 Polymer

In the present invention, the coating composition comprises a specific polymer, which is essential for achieving the technical effects of the present invention.

In one embodiment, the polymer used in the present invention is characterized in that it has:

(i) a glass transition temperature of less than 20°C, preferably less than 15°C, more preferably less than 10°C, more preferably less than 5°C, more preferably less than 0°C, more preferably less than -5°C, more preferably less than -10°C; and

(ii) a melting point greater than 20°C, more preferably greater than 25°C, more preferably greater than 30°C, more preferably greater than 35°C, more preferably greater than 40°C, more preferably greater than 45°C;

(iii) optionally having a solubility in water at 25°C of at least 40 g/l.

The polymers used in the present invention preferably have (i) a glass transition temperature below 0°C, preferably below -5°C, and more preferably below -10°C. The glass transition temperature defines the change/transition in the mechanical properties of the polymer. When the temperature is below the glass transition temperature, the polymer tends to assume a relatively hard and brittle state similar to glass. However, when the temperature is above the glass transition temperature, the polymer assumes a more elastic state, such as a rubbery state, which contributes to the advantageous mechanical properties of the coreless roll, particularly its resistance to collapse when compressed and the flexibility/elasticity of the coating.

Furthermore, the polymers used in the present invention preferably have (ii) a melting point greater than 35° C., preferably greater than 40° C., more preferably greater than 45° C. This property ensures that the polymer can be applied as a hot melt in one embodiment and hardens at room temperature.

In a preferred embodiment, the polymer used in the present invention exhibits (iii) a solubility in water at 25° C. of at least 40 g/l, preferably 200 g/l, and in particular 500 g/l. The solubility of the polymer in water ensures that the absorbent sheet product of the present invention (in particular toilet paper, etc.) has good flushability and biodegradability. Due to the relatively high solubility of the polymer, it dissolves or at least quickly forms a dispersion when in contact with water in the sewage system. As a result, clogging of the sewage system can be effectively prevented. For other embodiments of coreless rolls that are not typically disposed of through the sewage system, such as napkins, towels such as household towels, kitchen towels or hand towels, toilet paper, wipes and facial tissues, feature (iii) is not necessary, but is preferred.

The polymer used in the present invention is selected so as to satisfy the conditions of (i) glass transition temperature and (ii) melting point, and preferably also satisfy the condition of (iii) solubility in water.

The definition of "polymer" according to the present invention also includes blends of at least two different polyether polyols, in particular blends of polyethylene glycol and polypropylene glycol. The term "polymer" should also encompass copolymers composed of at least two different ether glycols, in particular copolymers of ethylene glycol and propylene glycol. Preferably, the individual polymers in such blends meet criteria (i), (ii), and optionally (iii).

As previously mentioned, the polymer's (i) glass transition temperature and (ii) melting point together contribute to the polymer's elastic behavior at room temperature (typically in the range of 20° C. to 25° C.) where coreless rolls are typically used. Furthermore, when the polymer is used in the coating composition of the present invention, the polymer provides a rolled absorbent sheet product that simultaneously exhibits excellent collapse resistance, flexibility, and elasticity.

The glass transition temperatures and melting points described above are therefore to be understood as peak temperatures, which can be determined by dynamic mechanical analysis (DMA) under the conditions specified in the examples.

DMA is a technique that applies an oscillating (sinusoidal) force to a material sample, such as a polymer, and measures the resulting displacement. This measurement can determine the strain (stiffness) and damping of the material, which are typically recorded as "modulus" and "tan δ." More specifically, "tan δ" represents the ratio of the loss modulus to the storage modulus of a material. Therefore, by measuring the phase lag of the displacement compared to the applied force, the damping properties of the material can be determined. When tan δ is plotted against temperature, the glass transition temperature and melting point of the material can be observed as peaks because the material absorbs energy when it undergoes a glass transition and when it melts.

The (i) glass transition temperature and (ii) melting point of the polymer used in the present invention can be measured by using, for example, a dynamic mechanical analyzer DMA 8000 available from .

In one embodiment, the polymer is a polyether polyol, preferably a polyether polyol selected from polyethylene glycol, polypropylene glycol and mixtures thereof, more preferably polyethylene glycol.

In one embodiment, the polymer has a number average molecular weight of 800 to 250,000, preferably 1,000 to 50,000, more preferably 1,500 to 15,000, more preferably 1,500 to 10,000, more preferably 2,000 to 7,500, for example 2,500 to 4,000.

In a preferred embodiment, the polymer is polyethylene glycol having a number average molecular weight of 800 to 250,000, preferably 1,000 to 20,000, more preferably 1,500 to 10,000, more preferably 2,000 to 7,500, more preferably 2,500 to 6,500, even more preferably 2,500 to 4,000.

The number average molecular weight of the polymers used in the present invention can be determined by techniques known in the art, such as gel permeation chromatography (GPC).

In another embodiment, the polymer used in the present invention can be represented by the following formula (I):

In the above formula, n represents an integer having an average value of 10 to 5000, preferably 10 to 2500, more preferably 20 to 1000, more preferably 30 to 200, more preferably 50 to 150 or 50 to 100. Preferably, n represents an integer having an absolute value of 10 to 5000, preferably 10 to 2500, more preferably 20 to 1000, more preferably 30 to 200, more preferably 50 to 150 or 50 to 100.

In the present invention, the amount of polymer in the coating composition is set so that the polymer is applied to the second end in an amount of 0.1 to 20 g/roll, preferably 0.1 to 10 g/roll, more preferably 0.1 to 5 g/roll, and particularly 0.5 to 2 g/roll. If the amount of polymer applied to the second end is less than 0.1 g/roll, the desired properties of flexibility and elasticity, as well as excellent collapse resistance, may not be fully achieved. Conversely, if the amount of polymer applied to the second end is greater than 20 g/roll, the roll exhibits excellent collapse resistance, as well as flexibility and elasticity, but the manufacturing cost may be increased.

2.2 Additives

plasticizers

The coating composition of the present invention may include a plasticizer, such as a known ester plasticizer. The plasticizer may contribute to the film-forming properties of the coating composition. The plasticizer is selected to be compatible with the polymer described above. In one embodiment, the coating composition of the present invention does not contain a plasticizer.

One type of plasticizer may be used alone, or two or more types may be used in combination.

From the viewpoint of stability over time, the plasticizer content in the coating composition of the present invention is preferably not more than 20 wt %, more preferably not more than 10 wt %, still more preferably not more than 5 wt % of the entire solid content concentration.

Enhancer

The coating compositions of the present invention may include a reinforcing agent.

In one embodiment, the coating composition of the present invention does not contain reinforcing chemical additives, such as strength resins, for example, water-soluble cationic or anionic polymers described below. When the coating composition includes reinforcing agents, water-soluble cationic polymers and/or water-soluble anionic polymers known in the art can be used.

Other additives

The composition of the present invention may contain various types of known additives as appropriate, as long as the effects of the present invention are not inhibited. Examples include perfumes, colorants, surfactants, antifouling and antibacterial agents, and inorganic or organic fillers.

One of these may be used alone, or two or more may be used in combination.

3. Absorbent products

The coreless roll of the present invention has many applications in the field of hygiene or household absorbent products. In particular, the roll of the present invention can be an absorbent sheet product selected from the group comprising napkins, towels such as kitchen towels or hand towels, toilet paper, wipes and facial tissues.

In the present invention, the absorbent sheet product consists of a continuous web of absorbent material having a first end and a second end, the continuous web consisting of at least one layer of base tissue having a typical basis weight of 8-60 g/ ^m2 , preferably 10-30 g/ ^m2 .

In one embodiment, the continuous web of absorbent material is a single-layer web made of tissue paper, or a multi-layer web made of, for example, 2 to 5 superimposed tissue paper layers. To obtain a multi-layer absorbent sheet product, a base tissue paper layer is combined in a processing step to the final number of layers, which can be, for example, 2 to 5, depending on the target properties of the final product. The total basis weight of the resulting multi-layer web is preferably not more than 120 g/m ² , more preferably less than 65 g/m ² , for example less than 55 g/m ² .

In the present invention, the second end of the continuous web is coated with the coating composition of the present invention (i.e., a coating composition comprising a polymer as described above) and spirally wound to form a roll of absorbent sheet product, such as a toilet paper roll. The coating composition can be applied to the second end using techniques known in the art. Examples of such well-known techniques include "spray coating" and "roller coating."

In the present invention, the coating composition is applied to at least one of the two sides of the continuous web, ie the upper side and/or the lower side of the continuous longitudinal web, or between the base tissue layers forming the web.

When the web is a multi-layer web, for example, a web having 2 to 5 stacked tissue layers, the coating composition can be applied to one or both sides of one or more layers, for example, all layers. In one embodiment, the coating composition is applied to one of the outer layers of the web, preferably the outer layer facing the axial hollow channels in the final absorbent sheet product (i.e., the outer layer that is closest to the axial hollow channels). The outer layer can be coated on one or both sides, preferably on its lower side, i.e., the side facing the axial hollow channels.

The absorbent sheet product of the present invention is preferably selected from napkins, paper towels such as kitchen towels or hand towels, toilet paper, wipes and facial tissues. As "toilet paper" we understand a soft and firm base tissue paper used for cleaning the buttocks after using the toilet (sometimes also called "bathroom paper").

The invention also relates to the use of the coreless roll as toilet paper, household towels, kitchen towels, cleaning paper, facial tissue or napkins.

According to a preferred embodiment, the absorbent sheet product is a toilet paper consisting of 2 to 5 superimposed tissue layers (e.g. 2 to 4 tissue layers), wherein the coating composition is applied to at least one outer layer of the continuous web, preferably on the underside of the outer layer closest to the axial hollow channels.

The size of the coreless roll of the present invention is not limited and depends largely on the intended absorbent sheet product. For example, a single roll may have a diameter (edge diameter) of 5 cm to 50 cm, preferably 8 cm to 20 cm. The axial hollow channel may have a diameter of 10 mm to 70 mm, preferably 20 mm to 50 mm. The width of the roll (i.e., the distance from one edge to the other) may range from 60 mm to 800 mm, preferably 70 mm to 400 mm, for example, 80 mm to 150 mm.

The continuous web of absorbent material forming the absorbent sheet product preferably has a total length in the machine direction of 1 to 60 m, preferably 1.5 to 50 m, for example 2 to 40 m. Optionally, the web can be partially cut in the machine direction so that it consists of continuous individual but connected sheets. The individual sheets can have a length (in the machine direction) of 80 to 300 mm, for example 100 to 250 mm, and particularly 100 to 200 mm.

4. Manufacturing method of coreless roll and absorbent product

The invention also relates to a method for producing a coreless roll as described above and below, comprising the following steps:

(A) conveying a continuous web of absorbent material having a first end and a second end, which is optionally composed of 1 tissue layer or 2 to 5 superimposed tissue layers;

(B) applying a coating composition to the second end;

(C) spirally winding the continuous web of absorbent material to produce a log of absorbent material web, the web of absorbent material being wound to define an axial hollow channel centrally located relative to the log and extending from one edge to the other edge of the log, with the first end located on the outside of the log and the second end located within the axial hollow channel;

(D) optionally, severing the continuous web of absorbent material in a direction substantially cross-machine direction to produce individual but connected sheets;

(E) Cutting the log into a plurality of coreless rolls.

According to one embodiment of the present invention, the method for manufacturing the coreless roll comprises another step:

(F) compressing the coreless roll in a direction perpendicular to the axial hollow channel to produce a compressed coreless roll.

The coreless rolls of the present invention can be manufactured using commercially available converting machines. Suitable converting machines are available, for example, from Paper Converting Machine Company (PCMC), Europe.

The following process description relating to machine modules/units should be understood as an example of a machine suitable for manufacturing the rolls of the present invention. It is also possible to use another machine/unit known in the art.

In the present invention, referring to Figures 5 and 6, the method for manufacturing the coreless roll includes the following steps:

(A) Transporting a continuous web (19) of absorbent material having a first end and a second end.

The continuous web (19) of absorbent material used in the present invention consists of one or more layers of base tissue paper having a basis weight of 8 to 60 g/ ^m2 , preferably 10 to 30 g/ ^m2 . The base tissue paper is usually provided as large parent rolls (15) and (16) with a width of 1.80 m to 7 m obtained from a tissue paper machine. The parent rolls (15) and (16) are installed on the unwinding units (10) and (11) of the processing machine (9). The number of parent rolls to be used corresponds to the number of layers in the target absorbent sheet product. In Figures 5 and 6, a two-layer toilet paper roll (1) is produced using two parent rolls (15) and (16), each providing one layer of toilet paper (18A) and (18B).

The layers (18A) and (18B) are fed from the unwinding units (10) and (11) to an embossing unit (12) where the layers are superimposed and combined (bonded) to produce a continuous web (19) of absorbent material.

The embossing unit comprises an engraving cylinder (20) and a mating rubber cylinder (21), which rotate in opposite directions and optionally include a glue dispenser (not shown). The engraving cylinder can be engraved with a microstructure pattern combining various embossing tips. The engraving cylinder can print single-stage or double-stage engravings into the superimposed layers.

The glue dispenser (if any) typically includes a large vat (storage for glue), an applicator cylinder, and an impregnation cylinder. The applicator cylinder is adjacent to the superimposed base tissue layer relative to the engraving cylinder. The impregnation cylinder (not shown) picks up the adhesive in the large vat and transfers the adhesive to the applicator cylinder (not shown). The applicator cylinder is configured to apply a certain pressure on the engraving cylinder at the distal end of the protrusion of the embossed web. Under the determined pressure, the adhesive passes through the web and bonds the layers. The amount of adhesive used for layer bonding is preferably 0.1 g/m ² to 5.0 g/m ² , preferably 0.2 g/m ² to 1.0 g/m ^2. An example of a suitable adhesive for layer bonding is 1004 available from HB Fuller, Europe.

The embossing step described above is used to combine the layers of base tissue and also to emboss or micro-emboss at least one layer to produce an aesthetic effect or to vary the thickness, softness or pliability of the resulting continuous web (19).

(B) applying the coating composition to the second end of the continuous web to form a full or partial coating. The coating composition is applied to the second end by techniques known in the art. In the present invention, spraying or roller coating may be used, among other techniques.

By "spraying," we understand the coating composition to be applied to the continuous web as a dispersion of fine droplets in a gas (i.e., a spray). The spray is typically produced using a nozzle (spray gun) with a fluid channel, which is operated when subjected to a mechanical force that atomizes the liquid. The droplets can have a size of 1 μm to 1000 μm, for example, 10 μm to 400 μm.

The processing machine (9) can be equipped with one or more spray guns (23A), for example 1 to 8 spray guns, which can be placed at any position in the processing line, as long as it makes sense to take into account the desired result (coating of the second end). The one or more spray guns (23A) can be placed before the embossing unit (12) so that the coating composition (22) is applied, for example, to the outer layer or between the layers. Preferably, the one or more spray guns (23A) are placed between the cutting module (27) and the winding module (28) so that the coating composition (22) is applied to the underside of the outer layer (as shown in Figure 5).

The spraying system comprises one or more spray guns (23A), a large vat (24) and a pipe (25) for feeding the coating composition (22) from the large vat to the one or more spray guns (23A). Optionally, the spraying system is equipped with a heating system (e.g., a heating jacket, a heat gun, etc., not shown) that heats the coating composition in the large vat (24), the pipe (25) and/or the one or more spray guns (23A) so that the composition remains in a liquid state during spraying. In particular, the heating system can heat the coating composition at a temperature above the melting point of the polymer used in the composition.

Spray guns suitable for spraying the coating composition of the invention are available, for example, from Walther Spritz- und Lackiersysteme GmbH, Germany.

By "roll coating", we understand that the coating composition is directly applied to the second end by the application roller. "Roll-to-roll coating" and "reverse roller coating" belong to the well-known technology that can be used for the present invention. Referring to Figure 6, the roller coating system includes a dipping cylinder and an applicator cylinder (23B), a large cylinder (24) and a pipe (25) that feeds the coating composition (22) from the large cylinder to the dipping and applicator cylinder (23B). The roller coating system optionally includes a heating system (not shown) as described above. As long as it is meaningful, the roller coating system can be placed in any position of the processing line. The roller coating system can, for example, be placed on the embossing unit in the following manner: the applicator cylinder (23B) is close to the engraving cylinder (20) or another cylinder (as shown in Figure 6).

One or more spray guns (23A) or roller coaters (23B) may be adjusted to apply a continuous coating in the machine and axial directions, or to apply intermittent coatings (eg, stripes, dots, etc.) in the machine and/or axial directions.

(C) Spirally winding the continuous web (19) to produce a log of absorbent material web (34).

A continuous web (19) is fed from an embossing unit (12) to a rewinding unit (13), where the web (19) is spirally wound to produce logs of absorbent material web (34). The rewinding unit (13) comprises a punching module (26), a cutting module (27), a winding module (28), and an extraction module (33). The rewinding unit (13) winds the continuous web (19) into a plurality of logs (34).

A winding module (28) is provided for winding a continuous web (19) to produce a log (34) of the web. The winding module (28) can be of the peripheral type (center winding) or the surface type (surface winding). The winding module comprises a rolling surface (29), a first winding roller (30), a second winding roller (31), a third winding roller (32) and a temporary core supplier (not shown). The log is formed by winding the continuous web onto a temporary core (36), which maintains a well-defined axial hollow channel. Before a new log production cycle begins, the core supplier sequentially provides the temporary core (36) via the rolling surface (29). The temporary core (36) can be made of plastic or cardboard, for example. At the start of a new production cycle, the second end of the web (19) can be picked up onto the temporary core (36) using "fleet glue" (pickup glue).

During winding, the log (34) is held in position by rotating first, second and third winding rollers (30), (31) and (32) in contact with the surface of the log (34). One of the winding rollers (30), (31) and (32) can impart a rotational motion to the log (surface winding).

Once the desired log diameter is reached (corresponding to a substantially defined web length or number of individual sheets), the continuous web (19) is cut, the produced logs (34) are separated from the web (19), and the production of new logs is subsequently started.

The cutting unit (27) is arranged to cut the web according to regularly spaced cutting lines substantially transverse to the machine direction. The cutting of the web takes place at the changeover stage, i.e. when the first log is finished at the end of a log production cycle and before the winding of the second subsequent log begins at the start of a new log production cycle.

The cutting lines (not shown) are lines formed in the axial direction along the thickness of the web (19). Two consecutive cutting lines define the total web length forming one roll. The distance between two consecutive cutting lines, i.e. the roll length, is determined depending on the target product. Typically, the roll length and roll diameter are selected based on, for example, the number of layers forming the web, the basis weight of the individual layers, etc. A single roll of absorbent sheet product can have a total web length in the machine direction of 1 m to 60 m, preferably 1.5 m to 50 m, for example 2 m to 40 m.

The manufactured log (34) is then provided to an extraction module (33), which is configured to extract a temporary core (36) from the log (34) after the log winding is completed. After extraction, the temporary core (36) can be returned to the core supplier.

When the coating composition used in the method of the present invention is an aqueous solution as described above, the produced log can be dried after separation from the absorbent material web and before extraction of the temporary core. The produced log can also be dried after extraction of the temporary core.

The produced logs are preferably dried until the moisture content of the tissue paper forming the logs does not exceed 10% of the total weight of the logs, preferably 5% of the total weight of the logs. For example, the produced logs can be dried by storing the logs at room temperature (20° C. to 25° C.) and RH (relative humidity) 10% to 60% for 12 hours.

(D) Optionally, severing the continuous web (19) of absorbent material substantially transverse to the machine direction to produce individual but connected sheets.

Before being spirally wound by the winding module (29) as described above, the continuous web (19) reaches a perforation module (26), if any, which is arranged to provide the web (19) with regularly spaced perforation lines (8) substantially transverse to the machine direction (i.e. axial direction) to produce a single but connected sheet (as shown in Figures 3, 4a and 4b).

The perforation line (8) is a line formed in the axial direction along the thickness of the web (19) and comprising alternating perforated and non-perforated sections (i.e., two perforated sections are separated by an non-perforated section and vice versa). Each non-perforated section forms a connecting region between two consecutive parts of the continuous web. Each perforated section forms a separating region between two consecutive parts of the continuous web. Taking into account the width of an individual roll, for example 10 cm to 30 cm, the length of the non-perforated/perforated sections can be 1 mm to 15 mm, preferably 4 mm to 10 mm. Other perforation lines are also possible, if this makes sense.

The two continuous perforation lines (8) define the length of a single sheet in the final absorbent sheet product. The distance between the two continuous perforation lines, i.e., the sheet length, is determined depending on the target product. A single sheet can have a length in the machine direction of 80 mm to 300 mm, for example, 100 mm to 250 mm. For example, a piece of toilet paper can have a length of 80 mm to 200 mm, and a towel paper such as a household (kitchen) towel or hand towel can have a length of 80 mm to 300 mm.

(E) Cutting the manufactured log (34) into a plurality of coreless rolls (1).

After winding, the log (34) is fed to a log cutting unit (14), wherein the log (34) is cut parallel to the machine direction by a plurality of log saws (35) into a plurality of individual rolls (1). The plurality of log saws (35) are regularly spaced apart in the axial direction so that the log (34) is cut into a plurality of individual rolls (1) having a defined width in the axial direction (i.e. the distance from one edge to the other). The width of the individual rolls (1) is 60 mm to 800 mm, preferably 70 mm to 400 mm, for example 80 mm to 150 mm.

The control module (37) is connected to the punching module (26), the cutting module (27) and the spraying or roller coating system via an interface (38). The control module (37) controls the operation of the punching module (26) and the cutting module (27). In particular, the control module (37) triggers the cutting module (27) to cut the web (19) during the transition phase between two consecutive logs. In addition, the control module (37) controls the operation of the punching module (26) outside the transition phase.

In addition, the control module (37) controls the operation of the spray or roller coating system, i.e., the coating composition is appropriately applied (sprayed or rolled) to the second end of the continuous web (19). The coating composition can be appropriately applied to the second end by sending, for example, a start/stop signal to the application (spray or roller coating) system, the signal being determined based on the length of the target product and machine parameters such as operating speed.

The various rollers (17) are appropriately positioned to control the path of the continuous web (19) along the processing machine (9) within and between the various units.

(F) Optionally, the roll is compressed in a direction perpendicular to the axial hollow channel to produce a coreless roll in a compressed (oval) form (not shown).

By "compression," we understand the application of pressure to the coil in a direction perpendicular to the axial hollow channel, in order to produce a coil with an elliptical cross-section that requires less storage space. Coil compression is preferably performed immediately after winding is terminated. Suitable devices known in the art can be used to perform the compression. In the present invention, two converging, synchronously driven conveyor belts, pneumatic or hydraulic platens, or other devices, such as those described in WO 95/13183, can be used.

Thereafter, the individual coreless rolls (1) are packaged and prepared for shipping (not shown).

Example

5. Examples

The following test methods are used to evaluate absorbent materials, polymers, and manufactured coreless rolls.

5.1. Basis weight

Basis weight is determined according to EN ISO 12625-6:2005, Tissue paper and tissue products, Part 6: Determination of basis weight.

5.2. Thickness (Caliper)

The measurement is performed using a precision micrometer (0.001 mm accuracy) according to a modified method based on EN ISO 12625-3:2014, Part 3. For this purpose, the distance between a fixed reference plate and a parallel pressure foot is measured. The diameter of the pressure foot is 35.7 ± 0.1 mm (10.0 ^cm² nominal area). The applied pressure is 2.0 kPa ± 0.1 kPa. The pressure foot can move at a speed of 2.0 ± 0.2 mm/s.

An apparatus that may be used is a thickness gauge model L&W SE050 (available from Lorentzen & Wettre, Europe).

The tissue product to be measured was cut into pieces of 20 x 25 cm and conditioned in an atmosphere of 23°C, 50% RH (relative humidity) for at least 12 hours.

For the measurement, a sheet is placed under the pressure plate, which is then lowered. The sheet's thickness is then read 5 seconds after the pressure stabilizes. The thickness measurement is repeated nine times, with additional samples processed in the same manner.

The average of the 10 values obtained was taken as the thickness of one sheet of the measured tissue paper product (eg, two-ply toilet paper) ("single sheet thickness").

5.3. Glass transition temperature and melting point

The measurement was performed by a dynamic mechanical analyzer DMA 8000 (available from PerkinElmer, Germany) equipped with a Material Pocket and a 1 L Dewar.

The polymer to be measured was added to the Material Pocket of the analyzer. The Material Pocket was mounted in the fixture of the analyzer (single cantilever bending geometry). The measurement was then performed from -120°C to 75°C with a gradient of 3°C/min and a frequency of 1.0 Hz.

The recorded tan delta response of the polymer is then plotted as a function of temperature. The glass transition temperature and melting point of the polymer are observed as peaks in the tan delta curve.

5.4. Number average molecular weight

The measurements were performed by gel permeation chromatography (GPC) using a PL-GPC 50 integrated GPC/SEC system equipped with a PL aquagel-OH MIXED 8 μm column 7.5×300 mm (both available from Agilent Technologies, Europe). The GPC system was calibrated using a PEG-10 EasiVial calibration available from Agilent Technologies.

A sample of the polymer to be measured was dissolved in an eluent (water) at a concentration of 2 mg/ml. The sample was injected (injection volume: 100 μL) and run at a flow rate of 1.0 mL/min using water as the eluent. The residence time (min) of the polymer was recorded as the peak. The number average molecular weight of the polymer was determined by comparing the recorded residence time with the residence time of the standard (calibrated) polymer.

5.5. Compression resistance

The measurement is carried out by means of a vertical dynamometer equipped with a 1 kN load cell. A device that can be used is the dynamometer model ZwickiLine Z1.0 (available from Zwick Roell, Europe).

For the measurement, the roll is placed horizontally between pressure plates, with the applied pressure perpendicular to the axial hollow channel. The roll is compressed between the plates at a constant speed of 60 mm/min. The compressive force is measured and plotted against the displacement of the load cell. The compressive force recorded at the first inflection point of the curve is considered the roll's compression resistance. Repeat the compression resistance measurement five times using additional samples.

The average of the five values obtained was taken as the compression resistance of the measured roll.

5.6. Peel force

The measurements are performed by means of a vertical dynamometer equipped with a shaft and maxillary jaw. The device that can be used is a dynamometer model ZwickiLine Z1.0 (available from Zwick Roell, Europe) equipped with a 10 N load cell.

For the measurement, the first inner coil of a coreless tissue roll is placed on the mandrel, and the outermost sheet is inserted into the upper jaw. The coil is unwound at a constant speed of 60 mm/min. The peel force required to separate the sheets forming the coil is measured and plotted against the displacement of the load cell. During the displacement interval, the maximum and average forces required to delaminate the sample are recorded. The peel force measurement is then repeated five times using additional samples.

The average value of the five maximum force values obtained was taken as the peeling force of the first inner ring.

5.7. Disintegrability

Disintegrability was determined according to NF Q34-20: 1998, Sanitary and Domestic Articles - Bathroom Tissue - Determination of Disintegration.

5.8. Raw materials, chemical materials and processing machinery

Absorbent materials

A two-ply base tissue paper (manufactured by SCA) having a basis weight of 42 g/ ^m2 and a thickness of 0.41 mm was used as the continuous web of absorbent material in the following examples.

A two-ply base tissue (continuous web) was prepared by combining one ply of base tissue to a final ply number (2) using conventional converting machinery as follows:

A first unwinding unit provides a first layer of base tissue paper from a first parent roll with a width of 0.6 m. A second unwinding unit provides a second layer of base tissue paper from a second parent roll with a width of 0.6 m. The two layers of base tissue paper are fed to the embossing unit. In the embossing unit, the base tissue papers are superimposed and combined (bonded) using an adhesive to form a continuous web of absorbent material. An engraving cylinder performs a double-layer engraving in the superimposed absorbent base webs. The adhesive used for layer bonding is 1004 in an amount of 0.5 g/ ^m² .

The resulting two-layer continuous web of absorbent material is fed to a rewinding unit.

Chemical Materials

The chemical materials used in the following examples are listed below:

For coating compositions:

Polyethylene glycol "PEG3000" from Sigma-Aldrich, number average molecular weight of approximately 3000 (determined by GPC); based on available data for other molecular weights, the estimated glass transition temperature is approximately -22°C and the melting point is approximately 53°C;

>Polyethylene glycol "PEG6000" from Sigma-Aldrich, number average molecular weight of approximately 6000 (determined by GPC), glass transition temperature of -22.7°C, and melting point of 58.7°C (determined by DMA);

> Starch Avedex W60 from Avebe;

Carboxymethyl cellulose (CMC) 7M1C from Ashland;

Adhesive:

>1004 from H.B. Fuller (for layer bonding);

> Tissue Tak 604 from Henkel ("fugitive adhesive" for winding).

Processing machines

A conventional tissue paper converting machine is suitable for making two-ply toilet paper. The machine comprises two unwinding units, an embossing unit, a rewinding unit and a log cutting unit.

The embossing unit consists of an engraving cylinder, a matching rubber cylinder, and a glue dispenser. The engraving cylinder can be engraved with a microstructured pattern using a combination of various embossing tips. The glue dispenser consists of a large vat, an applicator, and a dipping cylinder.

The rewinding unit consists of a punching module, a cutting module, a winding module, and a take-off module. The punching module consists of a punch roller and a stationary support roller. The cutting module consists of a cutting roller and a stationary support roller.

The rewinding unit is also equipped with a spraying system consisting of four spray guns model WA520 (available from Walther Pilot) with a nozzle diameter of 1.5 mm and an atomizing air pressure of 4 bar, a large vat, and pipes that supply the coating composition from the large vat to the spray guns. In addition, the spraying system includes a heating system that maintains a constant temperature of 60°C for the coating composition in the large vat, pipes, and spray guns.

A spray gun is placed between the cutting module and the winding module so that the coating composition is sprayed onto the underside of the continuous web of absorbent material upstream of the cutting line where the log begins, thereby defining the first web end (i.e. the turn of the log/roll adjacent the axial hollow channel).

The log cutting unit includes a plurality of log saws.

The various rollers are positioned appropriately to control the path of the absorbent web along the processing machine, within and between the different units. The absorbent web travels into the processing machine according to the machine direction (MD) from the unwinding unit, to the embossing unit, to the rewinding unit and to the web cutting unit.

The control module is connected to the punching module, the cutting module and the spray gun through an interface. The control module controls the operation of the punching module and the cutting module, and the appropriate spraying of the coating composition to the second end.

The machine speed was maintained at 100 m/min throughout the test.

Reference example (refer to toilet paper)

In order to obtain the desired coreless roll of toilet paper, a double-layered continuous web of absorbent material is produced as described above, transferred from the embossing unit and fed into a rewinding unit.

In the rewinding unit, the continuous web first reaches a perforation module, which clamps the web to provide perforation lines oriented transversely to the machine direction (MD) and regularly spaced relative to the cross direction (CD). The perforated sections measure 4 mm, while the unperforated sections measure 1 mm. The distance between two perforation lines is 123 mm.

After clamping, the absorbent material web reaches the winding module, where it is picked up onto a temporary core (outer diameter: 38 mm) using Tissue Tak 604 as a "fugitive adhesive." The web is then wound onto the core to form a log with a diameter of 101 mm (corresponding to a sheet with 150 holes).

The produced logs were separated from the absorbent material web by a cutting module which cut the web transversely to the MD.The produced logs were stored at 20-22°C and 50% relative humidity for a period of 12 hours.

After storage, the temporary core is extracted from the log by an extraction module.The produced log is cut parallel to the MD into individual rolls of 350 mm width by a plurality of log saws.

Example 1 (Toilet paper with PEG3000)

The coating composition was prepared by dissolving polyethylene glycol (PEG3000) having a number average molecular weight of 3000 in water at a concentration of 50 wt %. The resulting coating composition was supplied to a spray gun and applied at room temperature.

In order to obtain the desired coreless roll of toilet paper, a coreless roll was produced in the same manner as described in the above reference example, except that: after clamping/cutting and before winding the web, the coating composition was applied (sprayed) by a spray gun to a length of about 600 mm (i.e., about 5 sheets) upstream of the cutting line.

The amount of PEG3000 applied to the second end (length: 600 mm) was 1.5 g/roll (the amount given corresponds to the amount of PEG3000 on 600 mm of a single roll obtained after cutting the log)

Example 2 (toilet paper with PEG6000)

The coating composition was prepared by dissolving polyethylene glycol (PEG6000) having a number average molecular weight of 6000 in water at a concentration of 33 wt %. The resulting coating composition was supplied to a spray gun and applied at room temperature.

A coreless roll was produced in the same manner as in Example 1 using the coating composition described above.

The amount of PEG6000 applied to the second end (length: 600 mm) was 1.1 g/roll.

Comparative Example 1 (Toilet Paper with Starch)

A coating composition was prepared by dissolving starch (Avedex W60) in water at a concentration of 33% by weight. The resulting coating composition was fed to a spray gun and applied at room temperature.

A coreless roll was produced in the same manner as in Example 1 using the coating composition described above.

The amount of starch applied to the second end (length: 600 mm) was 1.0 g/roll.

Comparative Example 2 (Toilet Paper with Carboxymethyl Cellulose)

A coating composition was prepared by diluting CMC in water at a concentration of 3 wt %. The resulting coating composition was supplied to a spray gun and applied at room temperature.

A coreless roll was produced in the same manner as in Example 1 using the coating composition described above.

The amount of CMC applied to the second end (length: 600 mm) was 0.1 g/roll.

According to the procedures explained above, the properties of the toilet paper rolls obtained in Reference Example, Examples 1 and 2, and Comparative Examples 1 and 2 were evaluated. The results are shown in Table 1 below.

Table 1

These test data demonstrate that the use of the coating composition according to the present invention results in increased compression resistance while maintaining acceptable roll peel force. Toilet paper with greater compression resistance is also less prone to collapse. Furthermore, rolls according to the present invention can be unwound to the final sheet without tearing and/or damaging the sheet (i.e., no perforation and/or sheet damage occurs during peel force measurements).

In contrast, using a coating composition containing starch or CMC provides a roll in which the sheets of the first inner turn adhere firmly to each other (glue). As a result, it is impossible to unwind the roll without tearing and/or damaging the last sheet.

Claims (18)

1. A coreless roll of an absorbent sheet product, made of a continuous web of absorbent material spirally wound with a first end and a second end, the web of absorbent material being wound to define an axially hollow channel located at the center relative to the coreless roll and extending from one edge of the coreless roll to the other edge, and the first end being located on the outside of the roll and the second end being located in the axially hollow channel. The second end of the continuous web of the absorbent material comprises a coating composition containing a polymer, wherein the polymer is a polyether polyol selected from polyethylene glycol, polypropylene glycol, and mixtures thereof, wherein the polymer has: (i) a glass transition temperature below 20°C; and (ii) Melting point greater than 20°C; and The coating composition therein does not contain sugars. 2. The coreless roll according to claim 1, wherein the polymer has: (i) Glass transition temperature below 0 °C; and (ii) Melting point greater than 35°C, and (iii) Optionally, it has a solubility of at least 40 g/L in water at 25°C. 3. The coreless roll of claim 1, wherein the coreless roll is obtained by applying the coating composition to a second end of a continuous web of the absorbent material. 4. The coreless roll of claim 1, 2, or 3, wherein the coating composition comprises: (a) at least 50 wt% of the polymer; (b) Other additives not exceeding 50 wt%; (c) Any amount of water present, not exceeding 10 wt%; Each is based on the total weight of the coating composition. 5. The coreless roll of claim 1, 2 or 3, wherein the coating composition is applied in melt form or in aqueous solution form after the addition of water. 6. The coreless roll of claim 1, wherein the polymer has a number-average molecular weight of 800 to 250,000. 7. The coreless roll of claim 6, wherein the polymer is polyethylene glycol having a number average molecular weight of 800 to 250,000. 8. The coreless roll of claim 1, 2 or 3, wherein the polymer conforms to the following formula: In the above formula, n represents an integer with an average value between 10 and 5000. 9. The coreless roll of claim 1, 2 or 3, wherein the axial hollow channel has a periphery and the coating composition is applied circumferentially. 10. The coreless roll of claim 1, 2 or 3, wherein the coating composition is applied continuously along the machine and axial directions, or intermittently along the machine and/or axial directions. 11. The coreless roll of claim 1, 2 or 3, wherein the second end consists of at least one turn, which is a loop around the continuous web of material spirally wound around the axial hollow channel. 12. The coreless roll of claim 1, 2 or 3, wherein the amount of polymer is from 0.1 to 20 g/roll. 13. The coreless roll of claim 1, 2 or 3, wherein the web of the absorbent material consists of one thin paper layer or two to six stacked thin paper layers. 14. The coreless roll according to claim 1, 2 or 3, wherein it is in a compressed form. 15. The coreless roll of claim 1, 2 or 3, wherein it is an absorbent product selected from the group consisting of napkins, towels, toilet paper, wipes, handkerchiefs and facial tissues. 16. A method for manufacturing a coreless roll of absorbent sheet product, comprising the following steps: -Transfer a continuous web of absorbent material having a first end and a second end; - Optionally, the continuous web of the absorbent material is cut transversely to the machine direction to produce individual but connected sheets; - Apply the coating composition as defined in any one of claims 1 to 12 to the second end; - A continuous web of absorbent material is spirally wound to create a circular web of absorbent material, the web of absorbent material being wound to define an axial hollow channel located at the center of the circular web and extending from one edge of the circular web to the other edge, with the first end located on the outside of the circular web and the second end located in the axial hollow channel. - Cut the round material into many coreless rolls. 17. The manufacturing method of claim 16, further comprising the following step: - The coreless roll is compressed along a direction perpendicular to the axial hollow channel to produce a compressed coreless roll. 18. Use of the coreless roll according to any one of claims 1 to 14, for use as toilet paper, household towel paper, kitchen towel paper, wiping paper, facial tissue, handkerchief paper or napkin.