Patent Application
20100136291
The invention relates to a sheet of paper, especially a sheet of absorbent paper made of creped tissue, having an embossed pattern.
The invention relates in particular to a sheet of paper composed of at least a first and a second ply of creped tissue, intended for the field of wiping in a household, domestic or industrial application, that is to say capable of being used as kitchen roll, or towel, for example.
In the field of paper for sanitary or domestic use such as toilet paper or kitchen roll, it is known to produce sheets of paper composed of several plies of absorbent paper, for example made of creped tissue having a basis weight between 12 and 30 g/m2, provided with protrusions that are obtained by embossing.
This is because embossing gives bulk to the sheet and it improves the absorption of liquids, the feel and the softness. Attempts have been made to increase the absorption capacity still further by creating multilayer sheets which are obtained by combining at least two layers, also known as plies, each consisting of at least one of said embossed sheets.
Thus, a multilayer (or multiply) sheet is obtained which has given mechanical properties such as tensile strength and also absorption capacity.
Two methods of embossing and assembling the plies are commonly used depending on the desired properties of the end product.
The first is known in the field by the name “nested”. It consists firstly in embossing each of the plies separately so as to form, at the surface, protrusions which are generally substantially frustoconical or in the form of pyramid frustums. Next, adhesive is applied to the top of the protrusions of one of the plies, and the plies are arranged so that the faces having the protrusions face each other, the protrusions of one being between the protrusions of the other. Finally, the plies are assembled so that the protrusions that have been coated with adhesive nest between the protrusions of the other ply. Thus, the two plies are joined together by spots of adhesive between the tops of the protrusions of one ply and the unembossed regions between the protrusions of the other ply. A structure is produced in which the voids thus formed are able to give the sheet better absorption. Furthermore, the outer faces have a smooth and soft feel due to the hollow regions formed by the back of the protrusions. This technique is illustrated, for example, by Patent U.S. Pat. No. 3,867,225.
The second method of assembly is known in the field under the name “point-to-point”. It differs from the preceding method by the relative arrangement of the two plies. These, after they have been separately embossed, are brought together in such a way as to make the tops of the protrusions, or at least part of these tops, coincide. The plies are joined together by the tops of the protrusions, point-to-point. This technique is illustrated by Patent U.S. Pat. No. 3,414,459.
When the practical realizations of these structures are considered, whether they are of the nested or point-to-point type, the protrusions obtained during embossing are usually produced so as to be distributed in a pattern in which the protrusions are generally aligned in one or more directions, uniformly. Such a pattern makes it possible to obtain a sheet that is homogeneous as regards its mechanical properties.
However, in order to improve user satisfaction, it is important to increase the flexibility, also called “the bulk” of the sheet.
The flexibility of the sheet can be defined as being its ability to deform uniformly when it is placed in the hand of a user, their fingers being stretched out as an extension of their palm and when the user then closes their fingers.
A sheet of paper which has a high flexibility will then deform and bend or curve so as to remain substantially parallel to the shape determined by the inside of the palm of the user's hand.
A sheet of paper that has poor flexibility will fold along one or more lines, each portion of the sheet which extends between two fold lines remaining substantially flat.
A sheet of paper that has high flexibility is more pleasant to use.
Also known is an embossed multiply sheet such as described in Patent Application EP 1 236 830 A1 in which at least one first ply has a first embossed pattern consisting of a first series of first protrusions of frustoconical overall shape projecting from the inner face of the first ply, which in particular form first alignments and the tops of which are joined to the inner face of the second ply opposite each other; the two plies each have a second embossed pattern made up of a second series of second protrusions of frustoconical overall shape projecting from the inner face of the corresponding ply, and in that the tops of the second protrusions of one ply extend opposite and near the tops of the second protrusions of the other ply.
An embodiment of the invention includes an embossed paper sheet with improved absorption of the sheet without however decreasing its mechanical properties and which remains visually attractive.
An embodiment of the invention includes an embossed sheet composed of at least a first and a second ply of creped tissue having a basis weight between 12 and 30 g/m2 according to which the first ply has a first embossed pattern composed of a series of first aligned protrusions of frustoconical overall shape, the tops of which are oriented towards the inside of the sheet, the second ply comprises a first and a second series of protrusions, the tops of which are oriented towards the inside of the sheet, of which the second series have a height greater than that of the first series of protrusions.
In accordance with an embodiment of the invention, the protrusions of the first ply and the highest protrusions of the second ply are nested inside one another, and the lowest protrusions of the second ply are arranged between the protrusions of the first ply so as to create empty spaces between the two plies and promote a rapid absorption of liquid.
According to other features of the invention:
In an embodiment, the invention also provides a pair of engraved rolls for embossing an embossed sheet of which the first roll includes a first series of large pins of frustoconical overall shape that form first juxtaposed sets of concentric circular alignments and second large pins arranged between said concentric sets, and of which the second roll includes a series of large pins of frustoconical overall shape that form second juxtaposed sets of concentric circular alignments, and a series of small pins arranged between said second sets.
In accordance with an embodiment of the invention, the second roll includes, in addition, third pins arranged in the region at the center of the small pins, and in order to emboss the plies, the second rolls are keyed so that the large pins of each roll are nested and the third pins of the second roll and the second large pins of the first roll are also nested.
In an embodiment, the invention provides a process for manufacturing an embossed sheet by means of a pair of rolls such as defined previously.
Other features, details and advantages of the invention will appear on reading the detailed description which follows, for an understanding of which reference will be made to the appended drawings among which:
The sheet 10 of embossed paper has a first upper ply 12 and a second lower ply 14 made of creped tissue, intended for any type of hygiene or household products.
The tissue, having a basis weight between 12 and 30 g/m2, is preferably of the type obtained by conventional wet pressing, known as CWP.
More particularly, the sheet of paper 10 represented in
A first embossed pattern of each ply 12 and 14, of known overall design, is composed of first series of first protrusions 18 and 20, of frustoconical overall shape, projecting from the inner face of the corresponding ply 12, 14 while thus extending towards the inside of the sheet 10.
The first protrusions 18 and 20 in particular form first alignments in shapes, particularly in closed loops which in this instance are circles.
Here, according to
The first series of first protrusions 18 and 20 may be aligned in two main directions so as to define a grid. The two main directions are in this instance perpendicular to one another, and are inclined at 45° relative to the longitudinal L and transverse T directions of the sheet 10 as will be explained in greater detail below.
According to a known technique, the first protrusions 18, 20 forming the components of the first pattern are obtained by embossing the first 12 and second 14 plies of the sheet 10 respectively, by means of a pair of rolls such as that which is commonly known.
Thus, pins corresponding to the protrusions that it is desired to obtain on the first 12 and second 14 plies of the sheet 10 are formed in relief on the outer convex cylindrical face of the associated roll.
In order to produce the series of first protrusions 18 on the first ply 12 of the sheet 10, the embossing roll has, on its convex cylindrical face, a first homologous series of pins in relief and of frustoconical overall shape in relief, which are distributed in concentric circles in the first alignments of the first protrusions 18, so as to produce the corresponding part of the first pattern of the first ply 12.
Similarly, the series of protrusions 20 on the second ply 14 of the sheet 10 is produced by another embossing roll, of which the frustoconical pins in relief can be, are distributed in concentric circles.
In accordance with the teaching of this prior art, the first ply 12 has a second embossed pattern composed of second series of second protrusions 38, of frustoconical overall shape projecting from the inner face of the first ply 12, while thus extending towards the inside of the sheet 10.
The second protrusions 38 are produced in a similar way to the first protrusions 18 and 20, especially by a second series of second pins of frustoconical shape which extend over the convex surface of the second embossing roll.
When they are arranged opposite the protrusions 20 of the second ply 14, the protrusions 38 have a tendency to reduce the height of the protrusions 20: such protrusions are referenced 20′ in
The protrusions 18 of the first ply 12 and the protrusions 20 of the second ply 14 are nested inside one another.
The present invention, including an embodiment of a sheet cut along its thickness, is represented in
The first ply 4 includes a first series of protrusions 20 of frustoconical overall shape of which the tops are oriented towards the inside of the ply 1 and which may be arranged as illustrated in
By way of example, the protrusions 20 may have a height of around 0.8 mm and a surface area at the top of around 2 mm2 with an average density of around 4/cm2. In the particular case represented here, found between the series of circles is around eight first protrusions 20 grouped over a surface area of around 1 cm2.
The second ply 2 includes a first and a second series of protrusions respectively marked 3 and 5, of which the tops are all oriented towards the inside of the sheet, the second series of protrusions 5 having a height greater than that of the first series 3.
By way of illustration, the first protrusions 3 having a rounded surface at the top have a height of around 0.4 mm and a density of around 30 cm2. The second protrusions 5 have a geometry and a density closer to those of the protrusions 20 of the first ply 4.
In accordance with one advantageous aspect of the invention, the second protrusions 5 (the highest) of the second ply 2 are positioned nested with respect to the protrusions 20 of the first ply 4. One particularly favorable arrangement will be described in relation to
Moreover, the first protrusions (the lowest) 3 of the second ply 2 are placed between the protrusions 20 of the first ply, so as to form voids or pockets 6 between the plies which promote the rapidity of the absorption of liquids as is proved especially by the curve from
Such an arrangement of the protrusions improves the hold of the “small” protrusions 3 of the second ply 2 which are here closely held between the largest protrusions 5. The structure thus formed collapses less quickly in the wet state, which accelerates the passage of liquid to the inside of the structure, thus accelerating the rate of absorption of the sheet.
According to
The sets of circles being generally juxtaposed, the outermost circles C4 of said sets are tangent in certain places.
Furthermore, pins 201, of the same type as pins 200 forming the circles, are provided between the sets of circles, and preferably form squares.
The large pins 50 form in this instance sets of three juxtaposed concentric circles.
The small pins 30 are arranged in the areas between the sets of concentric circles; they are engraved in sorts of squares, the center of which includes a large pin 50.
In order to simplify things to a degree, it may be considered that
Thus, the concentric circles C1, C2, C3 and C4 correspond to the sets of circles C′1, C′2, C′3 and C′4, formed by the protrusions 20 of the first ply 4.
Thus, in accordance with an embodiment of the invention, the patterns of each of the plies 2, 4 are complementary, and fitted to one another so as to promote rapid absorption of liquid inside the plies, as is clearly shown by the curves from
The two curves from
In accordance with the tests carried out with respect to the absorption, the sample was laid flat on a porous, sintered glass sheet of which the pore size was determined to be 40 μm. A plate bearing weights was laid on the sample in order to keep the sample flat. The sample was thus slightly compressed. The porous sheet rested on a plate which had, in its center, an orifice of diameter equal to 3 mm into which a flexible tube opened from beneath in order thus to place the volume of the porous sheet in communication with a reservoir of liquid, the height level of which could be adjusted with respect to the level of the porous sheet. The reservoir was itself placed on a balance. This means made it possible to determine the amount of liquid which passed into the sample when the reservoir was raised relative to the porous sheet.
The liquid was water containing 9 g/l of sodium chloride.
The procedure involved impregnating the sample through the porous sheet while lowering the level of the sample relative to the reservoir. The amount of liquid absorbed was measured every ten seconds simply by measuring the loss of water from the reservoir. This was carried out with various weights.
Measurements of the absorption capacity may also be carried out without applying pressure.
In
It is seen that the curve I has a slope that is initially larger than the curve A which means that the sheet according to the invention has an absorption rate that is higher than a sheet according to the prior art.
This feature can be very important, or even determining, for purchasers, and users of this type of product.
Furthermore, the protrusions 20 of the first ply 4 may be joined together by components in relief such as disclosed, for example, in Application EP 1 101 866 A1.
This feature makes it possible to obtain a more pronounced embossed pattern.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0705080 | Jul 2007 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR2008/000878 | 6/23/2008 | WO | 00 | 1/11/2010 |
