JP7699688B2 - multilayer paper - Google Patents

Description

The present invention relates to multi-layer paper.

Conventionally, disposable tableware, medical equipment, and furniture have been widely made from molded plastic resin. Although there are alternatives to the conventional plastic resin made from bamboo or wood, these have the drawback of being expensive to manufacture and complicated to manufacture due to the need for molding. Furthermore, because plastic products pollute the ocean and have an impact on the ecosystem of marine life, there has been a demand in recent years from the perspective of environmental protection to establish alternative technologies to plastic tableware, medical equipment, and furniture.

In response to this, conventional art has proposed alternative materials such as paper stirring sticks and spoons with improved water resistance and hot water resistance (see, for example, Patent Document 1). Medical instruments made of a single piece of cardboard folded multiple times and paper furniture made of multiple layers of cardboard have also been proposed (see, for example, Patent Documents 2 and 3).

Patent No. 4355283 Japanese Utility Model Application Publication No. 59-102009 No. 3220813 Publication

However, the above-mentioned conventional techniques are still insufficient in terms of strength and other properties required for applications such as tableware, medical equipment, and furniture.
Therefore, in order to satisfy the strength requirements by laminating a single sheet of cardboard, not only is a lamination process required, which increases costs, but also synthetic materials are required for lamination, making it unsuitable for use in direct contact with the human body.

Therefore, the main objective of this invention is to provide a multi-layered paper that exhibits sufficient strength.

The multi-layer paper of the present invention, which solves the above problems,
The device has a plurality of intermediate layers and a pair of surface layers formed on the front and rear sides of the intermediate layers,
The pulp of the surface layer and the middle layer does not contain recycled paper pulp and contains 80 mass% or more of softwood kraft pulp and hardwood kraft pulp,
Does not contain wet strength agents,
The surface layer has a basis weight of 75 g/m ² to 260 g/m ² per layer, the middle layer has a basis weight of 600 g/m ² to 950 g/m ² as a whole, and the whole has a basis weight of 860 to 1470 g/m ² ;
The tensile strength in the longitudinal direction is 55.00 kN/m or more, the tensile strength in the transverse direction is 44.00 kN/m or more, the bending strength is 10.0 N or more, the bending strength in the longitudinal direction is 5.00 N or more, and the bending strength in the transverse direction is 3.00 N or more,
The intermediate layer is 3 to 7 layers, and the pair of surface layers is 5 to 9 layers in total,
The density is 0.65 to 1.00 g/ ^cm3 .
It is characterized by:

This multi-layered paper has excellent strength properties. In addition, depending on the application, the target object can be obtained from a single sheet of cardboard, rather than a laminated structure, which is advantageous in terms of cost and productivity.

The present invention provides multi-layer paper that exhibits sufficient strength.

The multi-layer paper according to one embodiment of the present invention will be described in detail below.
<Multilayer paper>
The multi-layer paper has a plurality of middle layers and a pair of surface layers formed on the front and back of the middle layers. The number of the middle layers is 3 to 7.

Uses for this multi-layer paper include "tableware," "medical equipment," "furniture," and "stationery." "Tableware" is a broad concept that includes not only tableware such as plates, bowls, chopsticks, cups, coasters, trays, stirrers, spoons, forks, and paper containers, but also cooking utensils such as knives and kitchen knives. "Medical equipment" includes tongue depressors, earpicks, combs, pus trays, and other substitutes for current plastic medical equipment. "Furniture" includes hangers and other substitutes for current plastic furniture. "Stationery" includes clear boards, clips, pens, and other substitutes for current plastic stationery.

The pulp in the surface layer and the middle layer contains 80% or more of softwood kraft pulp and hardwood kraft pulp.
Preferably, no recycled paper pulp is contained. If an excessive amount of recycled paper pulp is contained, a decrease in strength is observed, but if the upper limit is set to 20% by mass, the effect on strength is small.

It is preferable to mix softwood kraft pulp and hardwood kraft pulp, which results in a thicker paper and ensures sufficient strength.
In addition, by setting the mass ratio (%) of the softwood kraft pulp to the hardwood kraft pulp in the surface layers to 5/95 or more and 40/60 or less, the hardwood kraft pulp, which is relatively rigid and easily densified, is contained in a large amount, so that the pair of surface layers can obtain high density and rigid characteristics and have excellent strength. Furthermore, the surface layers can increase the effect of suppressing the penetration of moisture or oil components derived from the target object such as food into the interior.
On the other hand, by setting the mass ratio (%) of the softwood kraft pulp to the hardwood kraft pulp in the middle layer to 20/80 or more and 40/60 or less, the middle layer contains a large amount of softwood kraft pulp, which is highly flexible, and therefore has good flexibility.

(Softwood Kraft Pulp, Hardwood Kraft Pulp)
Here, the softwood kraft pulp includes, for example, unbleached softwood kraft pulp (NUKP), semi-bleached softwood kraft pulp (NSBKP), and bleached softwood kraft pulp (NBKP).
Examples of hardwood kraft pulp include unbleached hardwood kraft pulp (LUKP), semi-bleached hardwood kraft pulp (LSBKP), and bleached hardwood kraft pulp (LBKP). Among these, bleached softwood kraft pulp and bleached hardwood kraft pulp are preferably used from the viewpoint of achieving both the appearance and strength of the product after processing.

For each layer of the multi-layer paper, a suitable combination of chemical pulps such as hardwood sulfite pulp and softwood sulfite pulp may be used as necessary.
When the multilayer paper of the embodiment is used for paper tableware, for example, it is directly in contact with the target object such as food. Therefore, the other pulp used in the multilayer paper is preferably a chemical pulp, and among them, ECF pulp, TCF pulp, and unbleached kraft pulp (UKP) are more preferable. ECF pulp is a chlorine-free bleached chemical pulp produced by bleaching with chlorine dioxide (ClO2) without using chlorine (Cl2). TCF pulp is a completely chlorine-free bleached chemical pulp produced by bleaching with oxygen (O), hydrogen peroxide (P), or ozone (Z) without using chlorine (Cl2). That is, ECF pulp and TCF pulp have an advantage that the chlorine ion content is small or zero, so there is little risk of generating organic chlorine compounds such as dioxins even when incinerated at low temperatures, and as a result, the environmental load can be reduced. In addition, the use of unbleached kraft pulp makes it possible to produce a color similar to that of wood, and by eliminating the bleaching process, it is possible to reduce environmental impact by reducing energy consumption and CO2 emissions.

The multilayer paper of the embodiment has a multi-layer construction that combines a pair of surface layers that are hard and resistant to bending with a flexible middle layer, allowing the surface layers to be dense yet elastic, while suppressing distortion and bending.

(Surface Freeness)
In the multilayer paper of the embodiment, the lower limit of the Canadian Standard Freeness (CSF) of the pulp used in the surface layer is preferably 375 ml, particularly 410 ml. If the CSF of the pulp used in the surface layer is low, the drainage during papermaking of the surface layer of the multilayer paper may be poor, and drying may be difficult. As a result, this may lead to delamination of the surface layer. On the other hand, the upper limit of the CSF of the pulp used in the surface layer is preferably 465 ml, particularly 450 ml. If the CSF is high, it becomes difficult to adjust the pulp fiber orientation in the papermaking machine, which may cause the formation of the multilayer paper to be poor, and the paper strength and rigidity may be reduced for use as a paper container. By mixing and blending softwood bleached kraft pulp and hardwood bleached kraft pulp with high freeness, the multilayer paper can be thicker and have improved rigidity. Here, the Canadian Standard Freeness (CSF) is a value obtained by disintegrating pulp in accordance with the pulp disintegration method of JIS-P8220-1 (2012) to obtain disintegrated pulp, and measuring the disintegrated pulp in accordance with the Canadian Standard Freeness Testing Method of JIS-P8121-2 (2012).

(middle layer)
The multi-layer paper has a plurality of middle layers disposed between the pair of surface layers. The middle layers are composed of softwood kraft pulp and hardwood kraft pulp. The mass ratio (%) of the softwood bleached kraft pulp to the hardwood kraft pulp in the middle layers is 30/70 or more and 40/60 or less. By setting the mass ratio of the softwood kraft pulp to the hardwood kraft pulp in the middle layers to within the above range, the middle layers contain a large amount of softwood kraft pulp, which is highly flexible, and therefore have good flexibility. Therefore, as described above, the multi-layer paper has rigidity and is made of a pair of surface layers, which are hard but tend to break, combined with a flexible middle layer, so that the multi-layer paper has excellent toughness and durability.

(Middle layer freeness)
The lower limit of the Canadian Standard Freeness (CSF) of the pulp used in the middle layer of the multilayer paper of the embodiment is preferably 460 ml, particularly 470 ml. If the CSF is low, the dewatering in the papermaking machine will be poor. Furthermore, the rigidity may be reduced. On the other hand, the upper limit of the CSF of the pulp used in the middle layer is preferably 550 ml, particularly 520 ml. If the CSF is excessively high, there is a risk of little fibrillation, leading to a decrease in strength and interlaminar strength. Furthermore, it is preferable that the Canadian Standard Freeness of the pulp used in the middle layer is higher than the Canadian Standard Freeness of the pulp used in the pair of surface layers, from the viewpoint of ensuring elasticity while maintaining the interlaminar strength of the middle layer.

The total number of the intermediate layers is preferably 3 or more, and more preferably 5. By having the total number of the intermediate layers be 3 or more, the toughness and durability of the multilayer paper can be further improved. From the viewpoint of maintaining the interlaminar strength, the upper limit of the total number of the intermediate layers is preferably 7 or less.
When using a cylinder-net multi-cylinder combined papermaking machine, 3 to 7 layers are suitable in order to maintain interlayer strength during operation.

[Additives]
It is preferable that the multi-layer paper contains a sizing agent and a paper strength agent as papermaking additives in the surface layer and the middle layer.

(Sizing agent)
In order to further suppress the penetration of moisture or oil components derived from food or other objects into the multi-layer paper, a sizing agent can be added to each layer. Examples of sizing agents include styrene-based sizing agents, alkyl ketene dimers (AKD), alkenyl succinic anhydride (ASA), neutral rosin sizing agents, rosin sizing agents, modified rosin emulsion sizing agents, etc. Among these, rosin sizing agents and modified rosin emulsion sizing agents are preferred.

The rosin sizing agent is not particularly limited and is conventionally known in the papermaking field. Examples of rosin-based substances include reinforced rosins obtained by modifying rosins such as gum rosin, wood rosin, and tall oil rosin with α,β-unsaturated carboxylic acids such as fumaric acid, maleic acid, and acrylic acid or their anhydrides, and rosin esters obtained by reacting the rosins with polyhydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, and diglycerin. In the present invention, the rosin-based sizing agent also includes emulsions of these alone or a mixture thereof, and emulsions of these alone and then mixed. Furthermore, emulsions to which various polymers have been added to further improve sizing properties are also included.

The amount of sizing agent added to the surface layer is preferably 0.5 kg/t or more and 5.0 kg/t or less in terms of solids. The amount of sizing agent added to the middle layer is preferably 2.0 kg/t or more and 5.0 kg/t or less in terms of solids. Here, "kg/t" indicates the mass (kg) per ton of pulp. By adding the amount of sizing agent within the above range, water resistance can be improved.

(Paper strength agent)
The multi-layer paper can have a strength enhancing agent (sizing agent) added to each layer. By adding the strength enhancing agent, each layer can be given appropriate strength for use as paper tableware.

As the paper strength enhancer, various known ones such as polyacrylamide resin, polyamide resin, polyamine resin, acrylic resin, melamine resin, urea resin, polyamide epichlorohydrin resin, etc. can be used. Among these, it is preferable to use an amphoteric paper strength enhancer. Examples of amphoteric polyacrylamides include copolymers of acrylamide with the above-mentioned anionic monomer and cationic monomer, Mannich modified products of copolymers of acrylamide with the above-mentioned anionic monomer, and Hoffman decomposition products. According to the findings of the present inventors, amphoteric polyacrylamides are particularly preferable, and since amphoteric polyacrylamides have a self-fixing function, even if they are increased to improve the inter-paper strength, there is no excess of cations, and the modified rosin emulsion sizing agent can be stably fixed.

The amount of paper strength enhancer added to each layer is preferably 12 kg/t or more and 30 kg/t or less in terms of solids. By setting the amount of the paper strength enhancer to be within the above range, various paper strengths such as interlayer strength of multilayer paper can be imparted. If the amount of the paper strength enhancer added is below the above range, the interlayer strength may be insufficient. On the other hand, if the amount of the paper strength enhancer added exceeds the above range, the improvement in interlayer strength will remain almost flat, and further, the yield of the added paper strength enhancer will decrease, which may cause stains and foaming in the papermaking machine system and reduce operability (deterioration of dewatering). As a result, poor drying during the drying process may occur, which may cause delamination.

(Other additives)
The multi-layer paper may also contain various other papermaking additives within the scope of the intended effect of the present invention. Examples of other additives that can be added to the multi-layer paper include known papermaking chemicals.

[Physical properties of multi-layer paper]
(Basic weight)
The basis weight is measured in accordance with JIS-P8124 (2011). The basis weight of each layer of the multilayer paper does not need to be uniform, and the basis weights of the surface layer and middle layer are not particularly limited, but the basis weight of the surface layer is preferably 75.0 g/m2 or more and 260.0 g/m2 or less per layer. The basis weight of the entire middle layer is preferably 600 g/m2 or more and 950 g/m2 or less.

From the viewpoint of obtaining sufficient stiffness, the lower limit of the basis weight of the entire multilayer paper is preferably 750 g/m2, and more preferably 860 g/m2. The upper limit of the basis weight of the entire multilayer paper is preferably 1470 g/m2, and more preferably 1240 g/m2. If the basis weight is high, sufficient stiffness is easily obtained, but the thickness increases, and there is a risk that creases are more likely to occur with the calendar roll during papermaking.

The ratio of the total basis weight of the pair of surface layers to the total basis weight of the multilayer paper is preferably 25.0% or more and 35.0% or less. In a multilayer paper having a pair of rigid surface layers and a flexible middle layer, by setting the ratio of the total basis weight of the pair of surface layers within the above range, it is possible to impart properties that make the paper less likely to bend.

(paper thickness)
The thickness of the paper is measured in accordance with "Paper and paperboard - Test method for thickness and density" described in JIS-P8118 (2014). The thickness of the multilayer paper is preferably 750 μm or more and 20,200 μm or less. By having the thickness of the multilayer paper in the above range, peeling of the paper layers of the multilayer paper can be suppressed.

(density)
The density of the multilayer paper is preferably 0.65 to 1.00 g/cm3, and more preferably 0.73 to 0.85 g/cm3. By having the density of the multilayer paper in the above range, the paper exhibits the contradictory properties of having a high basis weight, excellent rigidity, and being difficult to break. If the density of the multilayer paper is less than 0.65 g/cm3, the paper has a good bending strength, but wrinkles due to handing and delamination may easily occur. On the other hand, if the density of the multilayer paper exceeds 1.00 g/cm3, wrinkles due to handing and delamination are unlikely to occur, but the strength and rigidity may decrease. For example, the density of the multilayer paper can be adjusted by the pulp freeness and ash content of the surface layer or middle layer, or by the calendering process.

(moisture)
The moisture content of the multilayer paper measured in accordance with JIS-P8127 (2010) is preferably 9.0% or more and 11.0% or less. When the moisture content of the multilayer paper is within this range, the flexibility is improved, which improves the workability in a folding machine when manufacturing tableware using the multilayer paper and the effect of suppressing breakage of the folded portion.

(ash)
The ash content is measured in accordance with JIS-P8251 (2003). The ash content of the multilayer paper is preferably 0.1% or more and 10.0% or less. By having the ash content of the multilayer paper in the above range, curl can be adjusted to be flat and a decrease in interlayer strength can be suppressed.

(Surface strength)
The surface strength is measured in accordance with the "Surface Strength Test Method" according to JAPAN TAPPI Paper and Pulp Test Method No. 1 m-72. The lower limit of the surface strength of the multilayer paper is preferably 10 A. When the surface strength of the multilayer paper is within the above range, it is possible to improve the resistance to falling off of the surface layer and the resistance to scratches during transportation and processing.

(Knob size)
The Cobb sizing degree is measured using distilled water at 23°C in accordance with JIS-P8140 (1998). The upper limit of the Cobb sizing degree of the multilayer paper is preferably 50 g/m2. If the Cobb sizing degree of the multilayer paper is equal to or higher than the upper limit, the multilayer paper may absorb moisture and cause rippling or wrinkles.

(Z-axis strength)
The Z-axis strength is preferably 380 kN/mm2 or more as measured in accordance with JAPAN TAPPI Paper and Pulp Testing Method No. 18-1: 2000. By having the above Z-axis strength, it is possible to suppress the occurrence of delamination and wrinkles during the formation of tableware.

(Bending strength)
The bending strength is 10.0N or more, so that when the tip is processed into tableware with sharp edges,
No breaks occur.

(Tensile strength)
The vertical tensile strength is 55.00 kN/m or more and the horizontal tensile strength is 44.00 kN/m or more, so there will be no breakage or twisting when the material is used for furniture, etc. that will be subjected to long-term loads.

(Bending strength)
The bending strength in the vertical direction is 5.00 N or more and the bending strength in the horizontal direction is 3.00 N or more, so that no cracks or the like will occur in the cross section when the material is processed into tableware or the like that requires deep engraving.

This multi-layer paper has excellent strength and durability, making it ideal for use as paper tableware to replace conventional plastic tableware.

[Manufacturing method of multi-layer paper]
The method for producing the multi-layer paper is not particularly limited, but for example, the multi-layer paper can be produced using a known multi-layer papermaking machine according to the following steps.
(1) Pulp fibers are dispersed in water to obtain a slurry, to which additives corresponding to each paper layer are added as necessary and mixed to prepare the paper stock for each paper layer.

(2) Next, using these raw material slurries, a surface layer, a single layer or multiple middle layer and a surface layer are made in a papermaking machine in a neutral range so that the pH of the multi-layer paper is 6 or more and 8 or less.
The papermaking method is not particularly limited, and any known papermaking machine, such as a Fourdrinier, cylinder, hybrid former, or gap former, can be used, but it is particularly preferred to use a cylinder multi-cylinder combined papermaking machine to make a paper with five or more layers. In the papermaking process, a coating liquid can be applied to the surface of the surface layer using a coating device such as a size press, a rod metering size press, or a gate roll coater to form a surface coating layer.

(3) Next, press with a pressure roll to remove moisture.

(4) Next, dry it in a dryer cylinder.
After drying, a smoothing treatment may be performed using a calendaring device such as a nip calendaring machine, a super calendaring machine, a machine calendaring machine, a soft calendaring machine, etc. By performing the smoothing treatment, a high gloss is imparted to the multilayer paper, making it suitable for use in paper tableware with a luxurious feel.

<Other embodiments>
The present invention is not limited to the above-described embodiment, and can be embodied in various other forms including the above-described forms and forms with various modifications and improvements.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

The methods for measuring the physical properties of the examples and comparative examples are as follows.
[Freeness (mL)]
The obtained multilayer paper was disintegrated in accordance with the pulp disintegration method of JIS-P8220-1 (2012) to obtain disintegrated pulp, and the disintegrated pulp was measured in accordance with the Canadian standard freeness test method of JIS-P8121-2 (2012).

[Basic weight (g/m2)]
The measurement was performed in accordance with "Paper and paperboard -- Basis weight measurement method" described in JIS-P8124 (2011).

[Paper thickness (μm)]
Measurements were made in accordance with "Paper and paperboard -- Test methods for thickness and density" described in JIS-P8118 (2014).

[Density (g/cm3)]
Measurements were made in accordance with "Paper and paperboard -- Test methods for thickness and density" described in JIS-P8118 (2014).

[Bending strength]
The bending strength was measured using a digital force gauge (manufactured by Imada Co., Ltd.) under the following test conditions: A test piece with a width of 15 mm and a length of 150 mm was fixed to a three-point bending jig, and the force gauge was lowered. The load at that time was taken as the bending strength (N). The test was performed in an environment of a temperature of 26°C and a humidity of 70%.

[Tensile strength]
The tensile strength is a value measured in accordance with JIS-P-8113 (2006).

[Flexural strength]
The bending strength was measured in accordance with JIS K7171: 2016. The test piece was prepared to have a width of 15 mm and a length of 150 mm.

[Wrinkles caused by hand]
The obtained multilayer paper was wound around a paper tube (diameter 9 inches) and the surface of the multilayer paper was evaluated for wrinkles due to the process as follows. The range of wrinkles due to the process that can be used was determined to be 3 or more.
5: No wrinkles from handling, no abnormalities in appearance.
4: There are some small wrinkles from squeezing, but the appearance is normal.
3: There are wrinkles from handling, but the level is not a problem in appearance.
2: There are wrinkles from handling, and the appearance is problematic.
1: There are noticeable creases all over the surface and the appearance is abnormal.

[Delamination]
The obtained multilayer paper was wound around a paper tube (diameter 9 inches) and the delamination of the surface of the multilayer paper was evaluated as follows. The range of delamination that can be used was determined to be 3 or more.
5: No delamination and no abnormality in appearance.
4: There is some thin delamination in some places, but the appearance is fine.
3: There is delamination between layers, but it is not a problem in appearance.
2: Interlayer peeling is observed, and there is a problem with the appearance.
1: Large interlayer peeling is noticeable and there is an abnormality in appearance.

[Example 1]
(1) The composition of the surface and middle layers is shown below.
(surface)
The following raw materials were added to 100 parts of a pulp slurry having a freeness of 440 ml and a NBKP:LBKP ratio of 10:90.
Rosin emulsion sizing agent: 0.8 kg solids/ton of pulp
Acrylamide-based paper strength agent: 19.0 kg solids/ton of pulp
(middle layer)
The following raw materials were added to 100 parts of a pulp slurry having a freeness of 440 ml and a NBKP:LBKP ratio of 35:65.
Modified rosin emulsion sizing agent: 6.0 kg solids/ton of pulp
Acrylamide-based paper strength agent: 19.0 kg solids/ton of pulp
(2) This pulp slurry was laminated using a wire-part multi-cylinder papermaking machine to form a pair of surface layers and five middle layers, for a total of seven layers. The basis weight of each layer is shown in Tables 1 and 2.
(3) A coating solution containing polyvinyl alcohol and paraffin wax was applied by calendaring to the surface of the surface layer in the following coating amounts to form a surface coating layer, thereby obtaining the multi-layer paper of Example 1.
Polyvinyl alcohol: 0.2 g/m2
Paraffin wax: 0.2 g/m2
Surface sizing agent: 0.6 g/m2

[Examples 2 to 7, Comparative Examples 1 to 5]
Multilayer papers of Examples 2 to 7 and Comparative Examples 1 to 5 were obtained in the same manner as in Example 1, except that the types, contents and physical properties of the raw materials were as shown in Tables 1 and 2.
Comparative Example 4 is a multi-layer paper formed only from a middle layer.

The multilayer paper of the present invention can be suitably used for paper tableware, paper medical instruments, paper furniture, and paper stationery.

Claims (5)

The device has a plurality of intermediate layers and a pair of surface layers formed on the front and rear sides of the intermediate layers,
The pulp of the surface layer and the middle layer does not contain recycled paper pulp and contains 80 mass% or more of softwood kraft pulp and hardwood kraft pulp,
Does not contain wet strength agents,
The surface layer has a basis weight of 75 g/m ² to 260 g/m ² per layer, the middle layer has a basis weight of 600 g/m 2 to 950 g/m ² as a whole, and the overall basis weight is 860 to 1470 g/m ² ;
The tensile strength in the longitudinal direction is 55.00 kN/m or more, the tensile strength in the transverse direction is 44.00 kN/m or more, the bending strength is 10.0 N or more, the bending strength in the longitudinal direction is 5.00 N or more, and the bending strength in the transverse direction is 3.00 N or more,
The intermediate layer is 3 to 7 layers, and the pair of surface layers is 5 to 9 layers in total,
The density is 0.65 to 1.00 g/ ^cm3 .
A multi-layer paper characterized by: The multi-layer paper of claim 1, wherein the mass ratio (%) of the softwood kraft pulp to the hardwood kraft pulp in the surface layer is greater than the mass ratio in the middle layer. The multi-layer paper according to claim 1, wherein the mass ratio (%) of the softwood kraft pulp to the hardwood kraft pulp in the surface layer is 5/95 or more and 40/60 or less, and the mass ratio (%) of the softwood kraft pulp to the hardwood kraft pulp in the middle layer is 20/80 or more and 40/60 or less. The multi-layer paper according to claim 1, in which the amount of paper strength agent added to each layer is 12 kg/t or more and 30 kg/t or less in terms of solid content. Tableware, medical equipment, furniture, and stationery made from the multilayer paper of claim 1.