JP5372452B2 - Paperboard manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress or prevent generation of defects of exudation to be generated when a paperboard is processed. <P>SOLUTION: An exudation inhibitor for the paperboard is characterized by comprising 1-30 mass% of one or more polymers selected from the following (a) and (b). (a) a polyvinyl alcohol with a saponification degree of 70-96 mol% and a polymerization degree of 300-4,000, and (b) a polymer with vinyl pyrrolidone units of 70-100 mol% and a weight-average molecular weight of 10,000-500,000. In a method for manufacturing the paperboard having a front layer, a back layer, and one or a plurality of intermediate layers placed between the front layer and the back layer, the method for manufacturing the paperboard has the step of adding the exudation inhibitor into a pulp slurry for the intermediate layer so that the content of one or more polymers selected from (a) and (b) may be 5-500 ppm to the solid content of the pulp. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention relates to a method of manufacturing a plate sheet, and more particularly relates to a method of manufacturing a paperboard occurrence of exudation drawbacks that may occur can be suppressed or prevented when processing the paperboard is paper making multilayer.

With the recent increase in used paper usage rate and waste paper export volume, domestic waste paper circumstances have deteriorated, and interest in countermeasures against defects (stains, stains, etc.) of paper and paperboard has further increased. The following methods are known as methods for preventing defects in paper and paperboard.
(1) A method comprising adding a polymer obtained by reacting an amine and an epihalohydrin to a pulp slurry (see, for example, Patent Document 1)
(2) A method of adding a polymer such as polyallylamine to a pulp slurry (for example, see Patent Document 2)

  In particular, paperboard has a high wastepaper content ratio of 90% or more, and it is considered indispensable to take measures against defects caused by wastepaper. Defects derived from used paper lead to deterioration in the quality of paperboard, for example, causing poor appearance, uneven printing, and poor adhesion during processing. As a defect found in paperboard, for example, a defect derived from an acrylate ester which is a component of an adhesive is common.

Conventionally, in the paperboard which is a multi-layer papermaking, countermeasures for defects are taken only for the pulp slurry for the outer layer for the purpose of preventing the occurrence of defects in the outer layer which is directly touched. On the other hand, the intermediate layer between the front and back outer layers of the paperboard is not a part that is directly touched, so no countermeasures against defects are required, such as pulp cake, waste paper cake, and floater floss generated from the deinking process. Often manufactured using low-quality raw materials.
Japanese Patent Laid-Open No. 62-223394 JP-A-63-264993

  As a problem peculiar to the paperboard, there are a defect caused when processing the produced paperboard, in addition to a defect derived from an adhesive foreign substance such as an acrylate ester, that is, a defect found in the production of the paperboard. For example, a defect such as oil stain (hereinafter also referred to as a seepage defect) may suddenly appear during a heat treatment process at a corrugated board processing company to which paperboard is shipped.

  The present inventors have analyzed the causative substance of the exudation defect in order to elucidate the cause of the occurrence of the exudation defect, and have found that petroleum wax such as paraffin wax is the causative substance. Petroleum waxes are hydrocarbons that are waxy solids at room temperature, and are roughly classified into three types: paraffin wax, microcrystalline wax, and petrolatum according to the Japanese Industrial Standard (JIS K 2235). Petroleum wax is a hydrocarbon having 20 to 50 carbon atoms as a main component, is highly hydrophobic, is a solid that easily melts at 40 to 100 ° C., and has a low melt viscosity. In the papermaking field, petroleum wax is used as a water-repellent agent for waterproof corrugated cardboard used for packaging and transporting foods such as fruits and vegetables, vegetables and fresh fish. Corrugated used paper is often used as a raw material for the intermediate layer of paperboard, and with the increase in recovered paper recovery rate, etc., the opportunity to use waterproof corrugated cardboard as raw material has increased, so problems related to seepage defects have become apparent. It seems to be.

  In order to further search for the layer that causes the bleeding defect, the present inventors peeled the outer layer of the paperboard where the bleeding defect was confirmed, and the blot spread to the intermediate layer. The knowledge that it is larger than the stain of the outer layer was also obtained. That is, it has been clarified that the causative layer of the seepage defect in the paperboard is an intermediate layer, unlike the conventional defect found in the production of paperboard. Petroleum wax melts under temperature conditions above the melting point and penetrates significantly in the surface direction and thickness direction of the paperboard rather than foreign substances derived from adhesives. It seems to be a causative substance of the exudation defect that appears.

  Since the cause of the seepage defect is not known, no technology has been developed to prevent the seepage defect of the paperboard. Accordingly, an object of the present invention is to suppress or prevent the occurrence of a seepage defect that may occur when processing paperboard.

  As a result of diligent research, the present inventors developed a bleed-out inhibitor containing a predetermined amount of the following polymer, and by adding this bleed-out inhibitor to the pulp slurry for the intermediate layer, Succeeded in suppressing or preventing the occurrence of

That is, the present invention is a method for producing a paperboard having a surface layer, a back layer, and one or a plurality of intermediate layers sandwiched between the surface layer and the back layer,
An anti-bleeding agent for paperboard containing one or more polymers selected from the following (a) and (b): a content of one or more polymers selected from (a) and (b) The present invention relates to a method for producing paperboard, comprising a step of adding to the intermediate layer pulp slurry so as to be 5 to 500 ppm.
(A) Polyvinyl alcohol having a saponification degree of 70 to 96 mol% and a polymerization degree of 300 to 4000 (b) A polymer having a vinylpyrrolidone unit of 70 to 100 mol% and a weight average molecular weight of 10,000 to 500,000

Moreover, in this invention , the pulp slurry for the said intermediate | middle layer may contain the pulp which contains 10 mass% or more from corrugated used paper as a raw material.
In addition, the anti-bleeding agent for paperboard containing at least one polymer selected from the above (a) and (b) is also referred to as “the anti-bleeding agent of the present invention” below.

  The anti-bleeding agent of the present invention is not limited to the one that completely prevents the occurrence of exudation defects that may occur when processing paperboard, and the exudation defects are not compared with those that have no countermeasures against exudation defects. Also included are those that reduce the number or reduce the area of the bleed defect, ie, those that suppress the occurrence of the bleed defect.

  According to the present invention, it is possible to suppress or prevent the occurrence of a seepage defect that may occur when processing paperboard, particularly when it is subjected to heat treatment. Therefore, when manufacturing processed products such as cardboard sheets from paperboard, Occurrence of defects, uneven printing, and poor adhesiveness during processing is suppressed or prevented.

Hereinafter, the present invention will be described in detail.
The anti-bleeding agent for paperboard of the present invention contains 1 to 30% by mass of one or more polymers selected from the following (a) and (b).
(A) Polyvinyl alcohol having a saponification degree of 70 to 96 mol% and a polymerization degree of 300 to 4000 (hereinafter also referred to as component (a))
(B) Polymer having a vinylpyrrolidone unit of 70 to 100 mol% and a weight average molecular weight of 10,000 to 500,000 (hereinafter also referred to as component (b)).

  The component (a) used in the anti-bleeding agent of the present invention can be obtained, for example, by saponifying polyvinyl acetate obtained by polymerizing a vinyl acetate monomer. The saponification degree of component (a) is 70 to 96 mol%, preferably 80 to 93 mol%, more preferably 85 to 90 mol%. When the degree of saponification is less than 70 mol% or the degree of saponification exceeds 96 mol%, sufficient bleeding prevention properties cannot be obtained. The component (a) includes one or more structural units derived from other monomers within the range where the saponification degree is 70 to 96 mol% in addition to the vinyl alcohol unit and the unsaponified vinyl acetate unit. You may contain.

Component (a) has a degree of polymerization of 300 to 4000, preferably 500 to 2400. When the degree of polymerization is less than 300, sufficient bleeding prevention properties cannot be obtained, and when the degree of polymerization exceeds 4000, handling becomes difficult. In the present invention, the component (a) in which the degree of polymerization and the degree of saponification are each specified within a specific range is preferable, when the degree of polymerization is high, the higher the degree of saponification, the aggregation of petroleum wax due to the component (a) is preferably suppressed. On the other hand, when the degree of polymerization is low, it is preferable that the degree of saponification is low because the adsorbability of component (a) to petroleum wax is high. In particular, when the degree of polymerization and the degree of saponification of the component (a) satisfy the relationship represented by the following formula, it is preferable that sufficient bleeding prevention properties can be obtained.
(100-X) Y = 5,000-60,000, preferably 6,000-50,000
(In the formula, X is the saponification degree (mol%) of the component (a), and Y is the polymerization degree of the component (a).)

  In addition, the saponification degree and the polymerization degree of the component (a) can be measured based on, for example, JIS K 6726 “Testing method for polyvinyl alcohol”.

  The component (b) used in the anti-bleeding agent of the present invention is a polymer containing vinylpyrrolidone units, and can be obtained, for example, by polymerizing an N-vinyl-2-pyrrolidone monomer. Component (b) is a vinylpyrrolidone unit of 70 to 100 mol%, preferably 80 to 93 mol%, more preferably 85 to 90 mol%. When the vinyl pyrrolidone unit is less than 70 mol%, sufficient bleeding prevention properties cannot be obtained.

  In addition to the vinyl pyrrolidone unit, the component (b) may contain one or more structural units derived from other monomers within a range of 30 mol% or less. Examples of other monomers include nonionic monomers such as (meth) acrylamide, styrene, alkyl (meth) acrylate, olefin, poly (oxyalkylene) allyl alcohol, vinylacetamide, vinylformamide, vinyl acetate, and dialkyl. Aminoalkyl (meth) acrylate, dialkylaminohydroxyalkyl (meth) acrylate, dialkylaminoalkylacrylamide, vinylimidazolium, allylamine, diallylamine, vinylamine or these were quaternized with methyl chloride, ethyl chloride, benzyl chloride, diethyl sulfate, etc. Cationic monomer, (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, vinylsulfonic acid, 2-acryloylamino-2-methylpropanesulfonic acid, hydroxypropanesulfuric acid Phosphate, such as anionic monomer or a salt thereof such as styrene sulfonic acid.

  Of these, nonionic monomers such as (meth) acrylamide, styrene, alkyl (meth) acrylate, olefin, (polyoxyalkylene) allyl alcohol, vinylacetamide, vinylformamide, vinyl acetate, dialkylaminoalkyl ( (Meth) acrylate, dialkylaminohydroxyalkyl (meth) acrylate, dialkylaminoalkylacrylamide, vinylimidazolium, allylamine, diallylamine, vinylamine or cationic quaternized with methyl chloride, ethyl chloride, benzyl chloride, diethyl sulfate, etc. Monomer, particularly preferably (meth) acrylamide, styrene, alkyl (meth) acrylate, olefin, (polyoxyalkylene) allyl alcohol, vinylacetate Bromide, vinyl formamide, nonionic monomers such as vinyl acetate.

  The component (b) has a weight average molecular weight of 10,000 to 500,000, preferably 20,000 to 100,000. When the weight average molecular weight is less than 10,000, sufficient bleeding prevention properties cannot be obtained, and when the weight average molecular weight exceeds 500,000, handling becomes difficult. In addition, the measurement of the weight average molecular weight of (b) component can be performed using a gel permeation chromatography (GPC) apparatus, for example.

  The anti-bleeding agent of the present invention is one or more selected from various polyvinyl alcohols having different saponification and polymerization degrees, and / or the above component (b), which is included in the above component (a). 1 or 2 or more types selected from various polymers having different vinyl pyrrolidone units and different weight average molecular weights. The content of the one or more polymers selected from the component (a) and the component (b) contained in the exudation preventing agent of the present invention is 1 to 30% by mass, preferably 3 to 25% by mass, More preferably, it is 5-20 mass%. When the content is less than 1% by mass, it is economically disadvantageous because it costs transportation, and when the content exceeds 30% by mass, handling becomes difficult. In addition, the numerical value of these content represents the total of content of each polymer, when a bleed-out prevention agent contains 2 or more types of polymers.

  The exudation preventing agent of the present invention can be prepared by mixing one or more polymers selected from the above (a) and (b) with water or the like. In addition to one or more polymers selected from the above (a) and (b), the anti-bleeding agent of the present invention may contain other polymers, surfactants, chelating agents, builders, organics as necessary. You may contain solvents, such as an acid, a pH adjuster, alcohol, an antifoamer, a disinfectant, antiseptic | preservative, a coloring agent, and a fragrance | flavor. The exudation preventing agent of the present invention is useful for suppressing or preventing the occurrence of exudation defects derived from petroleum wax that may be present in the pulp slurry for the paperboard intermediate layer, in other words, for the intermediate layer of paperboard. It is useful as an anti-bleeding agent for addition to the pulp slurry.

  Next, a method for producing paperboard using the anti-bleeding agent of the present invention will be described. The method for producing a paperboard of the present invention is such that the content of one or more polymers selected from the above (a) and (b) is a predetermined concentration with respect to the pulp solid content. And adding to the pulp slurry for the intermediate layer of paperboard.

  The paperboard generally has a surface layer, a back layer, and one or a plurality of intermediate layers sandwiched between the surface layer and the back layer. The surface layer is mainly virgin pulp or DIP (deinked waste paper pulp) having high whiteness and strength. The back layer is mainly waste paper pulp. When the surface strength and size are required, size press coating is performed. When whiteness on both sides is desired, the back layer has the same structure as the surface layer. It is said. The intermediate layer contains more waste paper pulp than the back layer, and is preferably manufactured using only waste paper pulp. Also, in order to conceal the blackness of the intermediate layer, a front and lower layer is provided between the intermediate layer and the surface layer (in some cases between the intermediate layer and the back layer) using a pulp having a slightly lower whiteness than the surface layer pulp. May be. The “intermediate layer” in the present invention includes a layer in which petroleum wax, which is a causative substance of a seepage defect, is feared to be mixed.

  The pulp slurry to which the anti-bleeding agent of the present invention is added contains pulp that is used to produce a paperboard intermediate layer. Examples of such pulp include pulp containing waste paper such as waste newspaper, magazine waste paper, miscellaneous waste paper, and corrugated waste paper as raw materials. In the case of pulp containing 10% by mass or more of corrugated waste paper as a raw material, the effect of the present invention is particularly remarkable. Demonstrated.

  When the anti-bleeding agent of the present invention is added to the pulp slurry for the intermediate layer of paperboard, the content of one or more polymers selected from the above (a) and (b) is 5 to 500 ppm based on the pulp solid content. , Preferably 25 to 350 ppm, more preferably 50 to 200 ppm. When the content of the polymer is less than 5 ppm with respect to the pulp solid content, sufficient bleeding prevention properties cannot be obtained, and even if the content exceeds 500 ppm, the effect corresponding to the content cannot be obtained, and economically. It is disadvantageous.

  The place on the production line when the anti-bleeding agent of the present invention is added to the pulp slurry for the intermediate layer is not particularly limited, and is a filter, a decker, an extractor, a thickener, a refiner, a stock chest, a blender, a mixing chest, Examples include machine chests, fan pumps, seed boxes, screens, inlets, and piping before and after. Among these, a filter, a decker, an extractor, a thickener, a refiner, a stock chest, a blender, a mixing chest, and pipes before and after that are preferable.

  The pulp solid content of the intermediate layer pulp slurry to which the anti-bleeding agent of the present invention is added is not particularly limited as long as it is a general concentration, but is preferably 2 to 15% by mass, more preferably 3 to 5% by mass. It is.

The paperboard production method of the present invention is the same as the known production method except that it has a step of adding the exudation inhibitor of the present invention to the pulp slurry for the intermediate layer, and is used in the known production method. Additives can be used. For example, freeness improver, yield improver, dry paper strength enhancer, wet paper strength enhancer, softener, sizing agent, water repellent agent, anti-braking agent, antiseptic, slime control agent, scale control agent, disinfectant You may use it combining the additive, such as a foaming agent, dye, a sulfuric acid band, a filler, an acid, an alkali, and the oozing-out prevention agent of this invention.
In the method for producing paperboard of the present invention, the paper machine used is not limited, and examples include paper machines such as a circular net, a long net, a short net, a combination, and an on-top.

  The method for producing paperboard of the present invention can be applied to the production of paperboard carried out under acidic, neutral and alkaline conditions, and there is no limitation on the use and type of the paperboard obtained. For example, mixed paper such as food container base paper and printing base paper, corrugated base paper such as liner and medium stencil paper, paperboard board such as white paperboard and colored paperboard, miscellaneous paperboard such as paper tube base paper, etc. Corrugated cardboard paper such as medium stencil paper is preferred.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited by these, unless the summary is exceeded. First, Tables 1 and 2 show components 1 to 13 used in Examples and Comparative Examples. Components 1 to 6 and Components 10 and 11 are polyvinyl alcohols obtained by saponifying polyvinyl acetate. Table 1 shows the saponification degree and polymerization degree of these components. Components 7 to 9 and Component 12 are polymers having vinylpyrrolidone units, Component 13 is a polymer of dimethyldiallylammonium chloride, the monomer units constituting these components and their mol%, and the weight average molecular weight of these components. It shows in Table 2.

(A) Preparation of anti-bleeding agent Ingredients 1 to 13 shown in Table 1 and Table 2 were diluted and mixed with ion-exchanged water, respectively, and Table 3 (Examples 1 to 9) and Table 4 (Comparative Examples 1 to 5). Each of the anti-bleeding agents shown in Table 1 was prepared.

(B) Manufacture of paperboard It was obtained by adding the anti-bleeding agent shown in Table 3 (Examples 1 to 9) and Table 4 (Comparative Examples 1 to 5) at the concentrations shown in Table 3 and Table 4 as well. A liner was produced using a pulp slurry for the liner intermediate layer. Specifically, it is as follows. In addition, the addition density | concentration shown in Table 3 and Table 4 is a density | concentration with respect to the pulp solid content of the components 1-13 in a bleed-out prevention agent. Moreover, each addition density | concentration of the sulfate band shown below, a rosin sizing agent, and a cationized starch is also a density | concentration with respect to pulp solid content. Furthermore, Comparative Example 6 shown in Table 4 is a control example to which no drug was added.

<Surface layer and back layer>
Add 2% by mass of sulfuric acid band, 0.2% by mass of rosin sizing agent, and 1.2% by mass of cationized starch in a machine chest to pulp slurry of 4% by mass of solid waste paper and unbleached kraft pulp. did.

<Intermediate layer>
An anti-bleeding agent was added in a mixing chest to a pulp slurry having a solid content of 4% by mass using corrugated cardboard as a raw material. Further, 2% by mass of sulfuric acid band, 0.2% by mass of rosin sizing agent, and 0.5% by mass of cationized starch were added in a machine chest.

Using the pulp slurry for each of these layers, a surface layer, an intermediate layer, and a back layer are produced by a circular net three-layer paper machine, and these are combined to obtain a basis weight of 80 g / m ^{2 for} the surface layer and 80 g / m for the intermediate layer. ² and a back layer of 80 g / m ² , and a three-layer papermaking liner having a basis weight of 240 g / m ² of the whole paperboard was obtained.

(C) Exudation prevention test Using the liners obtained in Examples 1 to 9 and Comparative Examples 1 to 6, the exudation prevention property was evaluated by the following method, and the results are shown in Table 3 (Example 1). To 9) and Table 4 (Comparative Examples 1 to 6).

  Ten liners cut into a 40 × 25 cm rectangle were heated at 105 ° C. for 10 minutes and allowed to cool for 1 hour. The number of exuding defects having a diameter of 2 mm or more that appeared on the surface layer or the back layer by heat treatment was measured. The exudation prevention rate was calculated according to the following formula.

Bleeding prevention rate:
{(Total number of exudation defects when no drug is added-Total number of exudation defects when a drug is added) / Total number of exudation defects when no drug is added} × 100 (%)

Based on the value of the bleeding prevention rate, the bleeding prevention property was evaluated according to the following criteria.
A: The bleeding prevention rate is 90% or more.
○: The bleeding prevention rate is 70% or more and less than 90%.
Δ: The bleeding prevention rate is 20% or more and less than 70%.
X: The bleeding prevention rate is less than 20%.

  The liner manufactured using the anti-bleeding agent of the present invention had good anti-bleeding properties. On the other hand, in Comparative Example 1, since the addition concentration of polyvinyl alcohol as the component (a) is less than 5 ppm, the bleeding prevention property is poor. In Comparative Example 2, the degree of saponification of the component (a) exceeds 96 mol%, so that the anti-bleeding property is poor. In Comparative Example 3, since the saponification degree of the component (a) is less than 70 mol%, the anti-bleeding property is poor. In Comparative Example 4, since the vinyl pyrrolidone unit of the polymer as the component (b) is less than 70 mol%, the bleeding prevention property is poor. In Comparative Example 5, since neither the component (a) nor the component (b) is added, the bleeding prevention property is poor.

Since the paperboard produced by the method of the present invention has a good anti-bleeding property, it is suitable as a paperboard that is subjected to heat treatment to produce a processed product, or a paperboard that is stored or used in a high-temperature environment. Can be used.

Claims (2)

A method for producing a paperboard having a surface layer, a back layer, and one or a plurality of intermediate layers sandwiched between the surface layer and the back layer,
An anti-bleeding agent for paperboard containing one or more polymers selected from the following (a) and (b): a content of one or more polymers selected from (a) and (b) A method for producing paperboard, comprising a step of adding to the pulp slurry for the intermediate layer so as to be 5 to 500 ppm relative to the intermediate layer.
(A) Polyvinyl alcohol having a saponification degree of 70 to 96 mol% and a polymerization degree of 300 to 4000 (b) A polymer having a vinylpyrrolidone unit of 70 to 100 mol% and a weight average molecular weight of 10,000 to 500,000   The method for producing a paperboard according to claim 1, wherein the pulp slurry for the intermediate layer includes pulp containing 10% by mass or more of corrugated used paper as a raw material.