CN114630938B - Multi-layer paper and method for producing same - Google Patents

Multi-layer paper and method for producing same Download PDF

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Publication number
CN114630938B
CN114630938B CN202080073977.XA CN202080073977A CN114630938B CN 114630938 B CN114630938 B CN 114630938B CN 202080073977 A CN202080073977 A CN 202080073977A CN 114630938 B CN114630938 B CN 114630938B
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Prior art keywords
paper
pulp
layer
layers
basis weight
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CN114630938A (en
Inventor
关公人
峯村和美
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Daio Paper Corp
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Daio Paper Corp
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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/30—Multi-ply
    • D21H27/40—Multi-ply at least one of the sheets being non-planar, e.g. crêped
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B29/00—Layered products comprising a layer of paper or cardboard
    • B32B29/002—Layered products comprising a layer of paper or cardboard as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B29/005—Layered products comprising a layer of paper or cardboard as the main or only constituent of a layer, which is next to another layer of the same or of a different material next to another layer of paper or cardboard layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/022—Mechanical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
    • D21F11/06—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the cylinder type
    • D21F11/08—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the cylinder type paper or board consisting of two or more layers
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/02—Chemical or chemomechanical or chemothermomechanical pulp
    • D21H11/04—Kraft or sulfate pulp
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
    • D21H13/10—Organic non-cellulose fibres
    • D21H13/12—Organic non-cellulose fibres from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H13/18—Polymers of unsaturated acids or derivatives thereof, e.g. polyacrylonitriles
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00—Coated paper; Coating material
    • D21H19/10—Coatings without pigments
    • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
    • D21H19/20—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
    • D21H21/18—Reinforcing agents
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/30—Multi-ply
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/26—All layers being made of paper or paperboard
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/546—Flexural strength; Flexion stiffness
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2479/00—Furniture
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2535/00—Medical equipment, e.g. bandage, prostheses, catheter

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Paper (AREA)

Abstract

The present invention provides a multi-layer paper having a sufficient thickness and exhibiting a sufficient strength. A multi-ply paper comprising two or more middle plies and a pair of surface plies formed on the surfaces and the insides of the middle plies, wherein the pulp of the surface plies and the middle plies contains 80% or more conifer sulfate pulp and broadleaf sulfate pulp, the pulp freeness of the surface ply pulp raw material of the surface plies is 375-465 ml, the pulp freeness of the middle plies is 460-550 ml, the middle plies are 3-7 plies, and the overall basis weight of the middle plies is 600-950 g/m 2 The basis weight of each surface layer is 75-260 g/m 2 The overall basis weight of the multi-layer paper is 750-1470 g/m 2 。

Description

Multi-layer paper and method for producing same
Technical Field
The present invention relates to a multi-ply paper and a method of manufacturing the same.
Background
Conventionally, articles molded from plastic resins have been widely used as disposable tableware, medical instruments, and furniture. In place of these conventional plastic resins, there are also bamboo and wooden articles, but there are problems that the manufacturing cost is high and the manufacturing is complicated because molding is required. In addition, plastic products have an influence on marine pollution and the ecosystem of marine organisms, and in recent years, from the viewpoint of environmental protection, it has been demanded to establish alternative technologies for plastic tableware, medical equipment, and furniture.
In contrast, conventionally, as an alternative material, a paper stirring rod and a spoon which improve water resistance and hot water resistance have been proposed (for example, see patent document 1). Medical devices in which one thick paper sheet is folded in a plurality of layers and paper furniture in which a plurality of thick paper sheets are stacked have also been proposed (for example, see patent documents 2 and 3).
Prior art literature
Patent literature
Patent document 1: japanese patent No. 4355283
Patent document 2: japanese laid-open patent publication No. 59-102009
Patent document 3: japanese registered patent publication No. 3220813
Disclosure of Invention
Problems to be solved by the invention
However, in the above-mentioned prior art, strength and the like required for use in tableware, medical instruments, furniture and the like are not yet sufficient.
Therefore, in a method of laminating a single thick paper sheet to satisfy strength and the like, a lamination step is required, which not only causes an increase in cost, but also requires a synthetic material for lamination, and is not suitable for use in direct contact with a human body.
Accordingly, a main object of the present invention is to provide a multilayered paper having a sufficient thickness and exhibiting a sufficient strength.
Means for solving the problems
The multi-layered paper of the present invention which solves the above problems is characterized in that,
it has more than two middle layers and a pair of surface layers formed on the surfaces and the insides of the middle layers,
the pulp of the surface layer and the middle layer contains more than 80% of conifer sulfate pulp and broadleaf sulfate pulp,
the middle layer is 3-7 layers,
the whole middle layer has a basis weight of 600-950 g/m 2 The basis weight of each surface layer is 75-260 g/m 2 The overall basis weight of the multi-layer paper is 750-1470 g/m 2 。
The middle layer is 3-7 layers, a pair of surface layers is 5-9 layers, and the basis weight of each layer is increased, thereby obtaining the whole basis weight of 750-1470 g/m 2 The high basis weight multi-layer paper is difficult to obtain in the prior art.
The multilayered paper has excellent strength characteristics such as bending strength. In addition, in the application, the object is obtained from one thick paper sheet instead of the laminated structure, and the cost and productivity are advantageous.
In addition, the method for manufacturing the multi-layered paper is characterized in that,
in the production of a multi-layered paper having two or more middle layers and a pair of surface layers formed on the front and back surfaces of the middle layers,
using a pulp raw material for a surface layer having a pulp freeness of 375 to 465ml and a pulp raw material for a middle layer having a pulp freeness of 460 to 550ml,
using a cylinder multi-cylinder papermaking machine for 5-9 layers of papermaking, wherein the whole middle layer has a basis weight of 600-950 g/m 2 The basis weight of each surface layer is 75-260 g/m 2 The overall basis weight of the multi-layer paper is 750-1470 g/m 2 。
The cylinder multi-cylinder papermaking machine is a papermaking machine which rotates a cylinder provided with metal wires in a groove and forms a fiber layer by using a pressure difference of water, thereby papermaking paper with thickness, and is formed continuously by one cylinder papermaking machine. The "papermaking" is to overlap wet paper before drying.
Thick paper can be easily obtained by making paper using a cylinder multi-cylinder papermaking machine for making 5 to 9 layers.
In the case of thick paper, there is a concern that some wrinkles may occur due to, for example, calender rolls in the paper making process. In contrast, if the pulp freeness of the pulp raw material for the surface layer is made lower than that of the pulp raw material for the middle layer in advance, for example, the pressurizing force by the calender roll is not concentrated but dispersed, so that the occurrence of partial wrinkles on the surface (similar to wrinkles generated when paper is handled by hand, and thus may be referred to as "handling wrinkles") can be suppressed. As a result, the appearance is improved, and the object is easily obtained from one thick paper.
Effects of the invention
According to the present invention, a multilayered paper having a sufficient thickness and exhibiting a sufficient strength and the like, and a method for producing the multilayered paper can be provided.
Detailed Description
Hereinafter, a multilayered paper according to an embodiment of the present invention will be described in detail.
< multilayer paper >
The multi-layer paper has two or more middle layers and a pair of surface layers formed on the surfaces and the insides of the middle layers. The middle layer is 3-7 layers.
Examples of the use of the multilayered paper include "tableware", "medical equipment", "furniture", "stationery", and the like. Further, "tableware" is a broad concept including not only tableware such as a dish, a bowl, chopsticks, a cup mat, a tray, a stirring bar, a spoon, a fork, paper ware, and the like, but also cooking devices such as a knife, a kitchen knife, and the like. The medical appliance can be replaced by a tongue depressor, an earpick, a comb, a pus basin and other current medical appliances made of plastics. The furniture can be taken as a clothes hanger or other substitutes of the current plastic furniture. The stationery may be replaced with transparent plate, clip, pen, etc.
The pulp of the surface layer and the middle layer contains more than 80% of conifer sulfate pulp and broadleaf tree sulfate pulp.
Preferably no used paper pulp. If the used paper pulp is excessively contained, a decrease in strength is observed, but if the upper limit is 20 mass%, the influence on strength is small.
Preferably, conifer sulfate pulp and hardwood sulfate pulp are mixed. As a result, the paper thickness becomes thicker, and sufficient strength can be ensured.
Further, by setting the mass ratio (%) of the conifer sulfate pulp to the hardwood sulfate pulp in the surface layer to 5/95 to 40/60 inclusive, a large amount of hardwood sulfate pulp which is relatively rigid and easily densified is contained, and therefore, a pair of surface layers can obtain high-density and rigid characteristics and is excellent in strength. The top layer can also enhance the effect of suppressing penetration of moisture or oil components from objects such as food into the interior.
On the other hand, the conifer sulfate pulp having a high softness is contained in a large amount by making the mass ratio (%) of the conifer sulfate pulp to the broadleaf sulfate pulp in the middle layer 20/80 to 40/60 inclusive, and therefore the middle layer has a good softness.
(conifer sulfate pulp, broadleaf sulfate pulp)
The conifer sulfate pulp is, for example, conifer unbleached sulfate pulp (NUKP), conifer semi-bleached sulfate pulp (NSBKP), conifer bleached sulfate process pulp (NBKP).
The broad-leaved tree sulfate pulp is, for example, broad-leaved tree unbleached sulfate pulp (LUKP), broad-leaved tree semi-bleached sulfate pulp (LSBKP), broad-leaved tree bleached sulfate pulp (LBKP). Among these, bleached kraft pulp of conifer and bleached kraft pulp of broadleaf tree are preferably used in view of both the appearance and strength of the processed product.
The layers of the multi-layer paper may be appropriately combined with known various pulps such as broad-leaved tree sulfurous acid pulp and conifer sulfurous acid pulp, as required; or pulp made from non-wood fibers such as Kenaf (Kenaf), hemp, reed, etc., by chemical or mechanical means.
The multilayered paper of the embodiment is, for example, used for paper tableware, and is in direct contact with an object such as food. Therefore, as other pulp used for the multi-ply paper, chemical pulp is preferable, and among them, ECF pulp, TCF pulp, unbleached sulfate pulp (UKP) is more preferable. ECF pulp is prepared without chlorine (Cl) 2 ) From chlorine dioxide (ClO) 2 ) Bleaching the produced chlorine-free bleached chemical pulp. TCF pulp is prepared without using chlorine (Cl) 2 ) Completely chlorine-free bleached chemical pulp produced by oxygen (O), hydrogen peroxide (P), ozone (Z) bleaching. Namely, due to chlorineSince the content of ions is a small amount or 0, ECF pulp and TCF pulp have an advantage that even if they are burned at low temperature, there is a low risk of generating organic chlorine compounds such as dioxins, and as a result, environmental load can be reduced. In addition, by using unbleached sulfate pulp, the color tone of wood can be approximated, and by omitting the bleaching step, energy and CO can be reduced 2 Such an environmental load is reduced.
The multilayer paper according to the embodiment is a multilayer paper-making structure in which a pair of surface layers having hard and hard-to-bend properties are combined with a middle layer having flexibility, and the surface layers have high density, can ensure elasticity, and can suppress deformation and bending.
(degree of surface layer freeness)
In the multi-ply paper of the embodiment, the lower limit of Canadian Standard Freeness (CSF) of the pulp used for the top layer is preferably 375ml, particularly preferably 410ml. When the CSF of the pulp used for the top sheet is low, the drainage property may be deteriorated and the drying property may be difficult at the time of papermaking of the top sheet of the multi-layer paper. As a result, the interlayer of the surface layer may be peeled off. On the other hand, the upper limit of CSF of the pulp used for the surface layer is preferably 465ml, particularly preferably 450ml. When CSF is high, the pulp fiber orientation in the paper machine is difficult to adjust, and the texture of the multi-layer paper is deteriorated, and when the paper machine is used as a paper article, there is a possibility that the paper strength and rigidity are lowered. The multilayer paper is mixed with needle-leaved tree bleached sulfate pulp and broadleaf tree bleached sulfate pulp with high freeness, the thickness of the paper is further increased, and the rigidity can be improved. Here, the Canadian Standard Freeness (CSF) is a value obtained by dissociating pulp according to the dissociation method of pulp of JIS-P8220-1 (2012) to prepare dissociated pulp, and measuring the dissociated pulp according to the canadian standard freeness test method of JIS-P8121-2 (2012).
(middle layer)
More than two middle layers are arranged between the pair of surface layers. The middle layer contains conifer sulfate pulp and broadleaf sulfate pulp as main components. The mass ratio (%) of the bleached conifer sulfate pulp to the broad-leaved sulfate pulp in the middle layer is 30/70 to 40/60 inclusive. When the mass ratio of the conifer sulfate pulp to the hardwood sulfate pulp in the middle layer is in the above range, the middle layer contains a large amount of conifer sulfate pulp having high flexibility, and thus has excellent flexibility. Therefore, the combination of the soft middle layer and the pair of surface layers which are rigid and hard but tend to be easily bent as described above makes the multilayered paper excellent in strength and durability.
(middle layer freeness)
The lower limit of the Canadian Standard Freeness (CSF) of the pulp used in the middle layer of the multi-layer paper according to the embodiment is preferably 460ml, particularly preferably 470ml. When the CSF is low, the dewatering property in the paper machine is poor. Further, the rigidity may be lowered. On the other hand, the upper limit of the CSF of the pulp for the middle layer is preferably 550ml, particularly preferably 520ml. If the CSF is too high, fibrillation is less, and there is a possibility that strength and interlayer strength may be lowered. Further, from the viewpoint of ensuring elastic force while maintaining interlayer strength of the middle layer, it is preferable that the Canadian standard freeness of pulp for the middle layer is higher than that of pulp for the pair of surface layers.
The number of layers of the intermediate layer is preferably 3 or more, and particularly preferably 5. The number of layers of the middle layer is 3 or more, whereby the toughness and durability of the multilayered paper can be further improved. The upper limit of the number of layers of the intermediate layer is preferably 7 layers or less in order to maintain the interlayer strength.
When a cylinder multi-cylinder papermaking machine is used, 3 to 7 layers are preferable from the viewpoint of operation while maintaining the interlayer strength.
[ additive ]
The multi-layer paper preferably has sizing agents and paper strength enhancers added to the top and middle layers as additives for papermaking.
(sizing agent)
In order to further suppress penetration of moisture or oil components from objects such as food into the inside of the multilayered paper, a sizing agent may be added to each layer. Examples of the sizing agent include a styrene sizing agent, alkyl Ketene Dimer (AKD), alkenyl Succinic Anhydride (ASA), a neutral rosin sizing agent, a rosin sizing agent, and a modified rosin emulsion sizing agent. Among these, rosin sizing agents and modified rosin emulsion sizing agents are preferable.
The rosin sizing agent is a conventionally known one in the papermaking field, and is not particularly limited. Examples of the rosin-based material include reinforced rosin obtained by modifying rosin such as gum rosin, wood rosin, and tall oil rosin with α, β -unsaturated carboxylic acid such as fumaric acid, maleic acid, and acrylic acid, or an anhydride thereof; rosin esters obtained by reacting the above rosin with polyhydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, and diglycerin. In the present invention, the rosin sizing agent also includes a sizing agent obtained by emulsifying a rosin-based sizing agent alone or a mixture thereof, and a sizing agent obtained by mixing a rosin-based sizing agent alone after emulsification. In addition, the above emulsified sizing agent includes sizing agents to which various polymers are added in order to further improve sizing manifestation.
The amount of the sizing agent to be added to the surface layer is preferably 0.5kg/t to 5.0kg/t in terms of solid content. The amount of the sizing agent to be added to the middle layer is preferably 2.0kg/t or more and 5.0kg/t or less in terms of solid content. "kg/t" means the mass (kg) of the sizing agent per 1t of pulp. By setting the addition amount of the sizing agent to the above range, the water resistance can be improved.
(paper strength enhancer)
The multi-ply paper may incorporate paper strength enhancers in each ply. By adding the paper strength enhancer, various strengths suitable for use as paper tableware can be imparted to each layer.
As the paper strength enhancer, known various materials such as polyacrylamide-based resin, polyamide-based resin, polyamine-based resin, acrylic resin-based resin, melamine resin, urea resin, polyamide epichlorohydrin resin, and the like can be used. Among these, an amphoteric paper strength enhancer is preferably used. The amphoteric polyacrylamide includes copolymers of acrylamide and the anionic monomer and cationic monomer, mannich (Mannich) modified products of copolymers of acrylamide and the anionic monomer, huffman degraded products, and the like. According to the findings of the present inventors, it is particularly preferable that the amphoteric polyacrylamide has a self-fixing function, and therefore, even if it is added to improve the inter-paper strength, the cation does not become excessive, and the modified rosin emulsion sizing agent can be stably fixed.
The amount of the paper strength agent to be added to each layer is preferably 12kg/t or more and 30kg/t or less in terms of solid content. By setting the addition amount of the paper strength enhancer to the above range, various paper strength such as interlayer strength of the multi-layered paper can be imparted. If the amount of the paper strength enhancer added is less than the above range, the interlayer strength may be insufficient. On the other hand, when the amount of the paper strength enhancer added exceeds the above range, the improvement in interlayer strength becomes substantially smooth, and further, the yield of the paper strength enhancer added is lowered, and dirt, foaming, and the like are generated in the paper machine system, and there is a possibility that the operability (dehydration property) is lowered. As a result, drying failure occurs in the drying step, and interlayer peeling may occur.
(other additives)
In addition, the multilayered paper may contain other various additives for papermaking within a range that does not impair the object effect of the present invention. Examples of other additives that can be added to the multilayered paper include known papermaking agents.
[ physical Properties of Multi-layer paper ]
(basis weight)
Basis weight was measured in accordance with JIS-P8124 (2011). The basis weight of each layer of the multilayered paper is not particularly limited, and the basis weight of the surface layer and the middle layer is preferably 75.0g/m per layer as the basis weight of the surface layer 2 260.0g/m above 2 The following is given. The basis weight of the whole middle layer is preferably 600g/m 2 950g/m above 2 The following is given.
As the lower limit of the basis weight of the whole multi-layer paper, 750g/m is preferable from the viewpoint of obtaining sufficient rigidity 2 More preferably 860g/m 2 . The upper limit of the basis weight of the whole multi-layer paper is preferably 1470g/m 2 More preferably 1240g/m 2 . If the basis weight is high, sufficient rigidity is easily obtained, but the thickness increases, and there is a possibility that the sheet may be folded by a calender roll during paper making, and wrinkles may easily occur.
The ratio of the total basis weight of the pair of surface layers to the basis weight of the whole multi-layer paper is preferably 25.0% to 35.0%. In the multilayered paper having a pair of rigid surface layers and a middle layer having flexibility, the bending resistance can be imparted by setting the ratio of the total basis weight of the pair of surface layers to the above range.
(paper thickness)
The thickness of the paper was measured according to the "test method for paper and board-thickness and density" described in JIS-P8118 (2014). The thickness of the multilayered paper is preferably 750 μm to 2,000 μm. By setting the thickness of the multilayered paper to the above range, peeling of the paper layers of the multilayered paper can be suppressed.
(Density)
The density of the multilayered paper is preferably 0.65 to 1.00g/cm 3 Particularly preferably 0.73 to 0.85g/cm 3 . When the density of the multilayered paper is in the above range, the multilayered paper exhibits the reverse properties of high basis weight, excellent rigidity, and difficulty in bending. The density of the multi-layer paper is less than 0.65g/cm 3 In this case, although the bending strength is developed, there is a possibility that handling wrinkles and interlayer peeling are easily generated. On the other hand, the density of the above-mentioned multi-layered paper exceeds 1.00g/cm 3 In the case of (2), although the process wrinkles and interlayer peeling are less likely to occur, the strength and rigidity may be lowered. For example, the density of the multi-layered paper can be adjusted by the pulp freeness or ash content of the surface layer or the middle layer, and the calendering process.
(moisture)
The moisture content of the multilayered paper measured in accordance with JIS-P8127 (2010) is preferably 9.0% or more and 11.0% or less. By setting the moisture content of the multilayered paper to the above range, flexibility is improved, and therefore, operability in a folding machine and a breaking suppressing effect of a folding portion in producing tableware using the multilayered paper can be improved.
(Ash content)
Ash was measured in accordance with JIS-P8251 (2003). The ash content of the multilayered paper is preferably 0.1% to 10.0%. By setting the ash content of the multilayered paper to the above range, the curl can be adjusted to be flat, and the decrease in interlayer strength can be suppressed.
(surface Strength)
The surface strength was measured according to the "surface strength test method" of JAPAN TAPPI pulp test method No. 1-72. The lower limit of the surface strength of the multilayered paper is preferably 10A. By setting the surface strength of the multilayered paper to the above range, the peeling of the surface layer and the scratch resistance at the stage of conveyance and processing can be improved.
(Cobb sizing degree)
Cobb sizing degree was measured in accordance with JIS-P8140 (1998) using distilled water at 23 ℃. As the upper limit of the Cobb sizing degree of the multilayered paper, 50g/m is preferable 2 . When the Cobb sizing degree of the multilayered paper is not less than the upper limit, the multilayered paper may be subject to waviness and wrinkles due to moisture absorption.
(Z-axis Strength)
Regarding Z-axis intensity, to test method No.18-1 according to JAPAN TAPPI pulp: the Z-axis intensity meter for 2000 measurements is preferably 380kN/mm 2 The above. By having the Z-axis strength, interlayer peeling and wrinkles generated during tableware molding can be suppressed.
(bending Strength)
When the bending strength is 10.0N or more, bending does not occur when the tip is processed into a sharp tableware.
(tensile Strength)
By setting the tensile strength in the longitudinal direction to 50.00MPa or more and the tensile strength in the transverse direction to 40.00MPa or more, breakage and twisting do not occur when furniture or the like to which a load is applied for a long period of time is processed.
(flexural Strength)
By setting the bending strength in the longitudinal direction to 5.00N or more and the bending strength in the transverse direction to 3.00N or more, cracks or the like in the cross section do not occur when the tableware is processed into tableware requiring deep-drawing processing.
The multilayered paper is suitable for paper tableware which has excellent toughness and durability and can replace the existing plastic tableware.
[ method for producing multilayer paper ]
The method for producing the multilayer paper is not particularly limited, and the multilayer paper can be produced by a known multilayer paper machine, for example, through the following steps.
(1) The additive corresponding to each paper layer is added to the slurry obtained by dispersing pulp fibers in water as needed, and mixed to prepare a paper stock for each paper layer.
(2) Next, using these raw material pulps, the surface layer, the single-layer or multi-layer middle layer and the surface layer are made by a paper machine in the neutral zone so that the pH of the multi-layer paper becomes 6 to 8.
The papermaking method is not particularly limited, and a known papermaking machine such as a fourdrinier wire, a cylinder, a hybrid molding machine, a gap molding machine or the like can be used, but a cylinder multi-cylinder papermaking machine is particularly preferably used to perform papermaking in a plurality of layers of 5 layers or more. In the papermaking step, a coating device such as a size press, a rod size press, a gate roll coater, or the like may be used to apply a coating liquid to the surface of the surface layer to form a surface coating layer.
(3) Next, pressing is performed by a pressing roller to remove moisture.
(4) Then, the mixture was dried by a drying cylinder.
After drying, smoothing treatment may be performed using a calender device such as a roll calender (nip calender), a supercalender, a mechanical calender, a soft calender, or the like. By performing the smoothing treatment, the multilayered paper can be given high glossiness and can be suitably used for paper tableware having a high quality feeling.
< other embodiments >
The present invention is not limited to the above-described embodiments, and may be implemented with various modifications and improvements other than the above-described embodiments.
Examples
The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples.
The physical property values of examples and comparative examples were measured as follows.
[ freeness (mL) ]
The resulting multi-layered paper was disintegrated according to the method of disintegration of pulp of JIS-P8220-1 (2012), thereby producing disintegrated pulp, which was measured according to the Canadian Standard freeness test method of JIS-P8121-2 (2012).
[ basis weight (g/m) 2 )]
The measurement was performed according to the "paper and board-based weight measurement method" described in JIS-P8124 (2011).
[ paper thickness (. Mu.m) ]
The measurement was performed in accordance with "test method for paper and board-thickness and density" described in JIS-P8118 (2014).
[ Density (g/cm) 3 )]
The measurement was performed in accordance with "test method for paper and board-thickness and density" described in JIS-P8118 (2014).
[ bending Strength ]
The bending strength was measured by a digital dynamometer (manufactured by Imada, inc.) under the following test conditions. The test piece with the width of 15mm and the length of 150mm is fixed on a three-point bending clamp, so that the dynamometer descends. At this time, the load was set to bending strength (N). The test was performed in a test environment at a temperature of 26℃and a humidity of 70%.
[ tensile Strength ]
The tensile strength was measured in accordance with JIS-P-8113 (2006).
[ bending Strength ]
Flexural Strength according to JIS K7171: 2016. Test pieces were prepared to a width of 15mm and a length of 150mm.
[ treatment of wrinkles ]
The resulting multi-ply paper was wound on a paper tube (diameter 9 inches), and the treated wrinkles on the surface of the multi-ply paper were evaluated as follows. The usable range of the process wrinkles was determined to be an evaluation value of 3 or more.
5: no wrinkles were treated and no appearance was abnormal.
4: small process wrinkles are present in part, but the appearance is not abnormal.
3: the treated wrinkles were present, but at a level where there was no problem in appearance.
2: there are handling wrinkles and appearance problems.
1: the whole surface has obvious treated wrinkles and abnormal appearance.
[ delamination ]
The obtained multilayered paper was wound around a paper tube (diameter 9 inches), and the delamination of the surface of the multilayered paper was evaluated as follows. The usable interlayer peeling range was judged to be an evaluation value of 3 or more.
5: no interlayer peeling and no abnormal appearance.
4: there was thin interlayer peeling in the portion, but the appearance was not abnormal.
3: there was interlayer peeling, but at a level where there was no problem in appearance.
2: there is interlayer peeling and appearance problems.
1: large interlayer peeling was evident, and appearance was abnormal.
Example 1
(1) The proportions of the surface layer and the middle layer are shown below.
(surface layer)
NBKP at a freeness of 440 ml: LBKP is 10:90 parts of 100 parts of pulp slurry were added with the following raw materials.
Rosin emulsion sizing agent: 0.8 kg/pulp t on a solids basis
Acrylamide-based paper strength enhancer: 19.0 kg/pulp t on solids basis
(middle layer)
NBKP at a freeness of 440 ml: LBKP is 35:65 to 100 parts of pulp slurry were added the following raw materials.
Modified rosin emulsion sizing agent: 6.0 kg/pulp t on a solids basis
Acrylamide-based paper strength enhancer: 19.0 kg/pulp t on solids basis
(2) The pulp slurry was formed into a total of 7 layers of a pair of surface layers and 5 layers by a multi-cylinder papermaking machine having a cylinder wire. The basis weights of the layers are shown in tables 1 and 2.
(3) The coating liquid containing polyvinyl alcohol and paraffin wax was roll-coated onto the surface of the top sheet so as to achieve the following coating amounts, thereby forming a top coating layer, and a multi-layered paper of example 1 was obtained.
Polyvinyl alcohol: 0.2g/m 2
Paraffin wax: 0.2g/m 2
Surface sizing agent: 0.6g/m 2
Examples 2 to 7, comparative examples 1 to 5 and reference examples 1 to 4
The multi-layered papers of examples 2 to 7, comparative examples 1 to 5 and reference examples 1 to 4 were obtained in the same manner as in example 1 except that the types, contents and physical property values of the raw materials were as shown in tables 1 and 2.
Comparative example 4 is a multi-layer paper formed only of a middle layer.
Reference examples 1 to 4 are examples of multi-ply papers in which the freeness of pulp was changed.
[ Table 1]
[ Table 2 ]
Industrial applicability
The multi-layered paper of the present invention can be suitably used for paper tableware, paper medical devices, paper furniture, paper stationery.

Claims (10)

1. A multi-layered paper is characterized by comprising at least two middle layers and a pair of surface layers formed on the surfaces and the insides of the middle layers,
the pulp of the surface layer and the middle layer comprises more than 80% of conifer sulfate pulp and broadleaf tree sulfate pulp,
the middle layer is 3-7 layers,
the whole basis weight of the middle layer is 600-950 g/m 2 The basis weight of each surface layer is 75-260 g/m 2 The overall basis weight of the multi-layer paper is 750-1470 g/m 2 ，
In the middle layer, the mass ratio of the conifer sulfate pulp to the broadleaf sulfate pulp is 20/80-40/60, and the addition amount of the paper strength enhancer is 12 kg/t-30 kg/t based on the solid content.
2. The multi-layered paper according to claim 1, which has a bending strength of 10.0N or more.
3. The multi-layered paper according to claim 1, wherein the tensile strength in the machine direction is 50.00Mpa or more and the tensile strength in the transverse direction is 40.00Mpa or more.
4. The multi-layered paper according to claim 1, wherein the bending strength in the machine direction is 5.00N or more and the bending strength in the transverse direction is 3.00N or more.
5. The multi-layered paper according to claim 1, wherein the density of the multi-layered paper is 0.65 to 1.00g/cm 3 。
6. The multi-layered paper according to claim 1, wherein the surface layer has a surface coating layer containing polyvinyl alcohol on the surface of the surface layer.
7. The multi-ply paper of claim 1 wherein the paper strength enhancing agent is polyacrylamide.
8. A method for producing a multi-layered paper, characterized in that, when producing a multi-layered paper having two or more middle layers and a pair of surface layers formed on the front and back surfaces of the middle layers,
using a pulp raw material for a surface layer having a pulp freeness of 375 to 465ml and a pulp raw material for a middle layer having a pulp freeness of 460 to 550ml,
using 5-9 layers of cylinder mould for making paperThe basis weight of the whole middle layer is 600-950 g/m 2 The basis weight of each surface layer is 75-260 g/m 2 The overall basis weight of the multi-layer paper is 750-1470 g/m 2 。
9. The method for producing a multi-layer paper according to claim 8, wherein 12 to 30kg/t of polyacrylamide is added to the pulp raw material for middle layer and the pulp raw material for surface layer.
10. Tableware, medical appliances, furniture and stationery formed from the multi-layered paper of claim 1.
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JP2014141773A (en) * 2012-12-26 2014-08-07 Chuetsu Pulp Kogyo Kk Coated paper for printing
JP2015172260A (en) * 2014-03-11 2015-10-01 北越紀州製紙株式会社 Method of producing white paperboard

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