JP5357577B2 - Processed paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide converted paper that has excellent cushioning properties, skid-proof property and surface strength and has excellent processing, laminating and box-making suitability to corrugated board sheet, corrugated board packaging container, interior packaging container, etc. <P>SOLUTION: In the converted paper including base paper and a coated layer arranged at least on one side of the base paper, the coated layer is formed by coating with a coating liquid containing an aqueous resin emulsion, heat foamable particles, pulp and a binder. The aqueous resin emulsion contains an intramolecular carboxy group-containing polymer emulsion. The coated layer surface has a coefficient of static friction of &ge;0.10 and &le;0.25 measured in conformity to JIS-P8147 (1994) and a slip angle of &ge;12 degrees and &le;20 degrees measured in conformity to JIS-P8147 (1994). <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a processed paper, and more particularly to a processed paper excellent in cushioning properties, anti-slip properties and surface strength, and excellent in processing, laminating and boxing suitability to corrugated cardboard sheets, corrugated cardboard packaging containers, interior packaging containers and the like.

  Conventionally, for example, in the packaging of electrical appliances and glass bottles, the product is fixed by using a low-cost and lightweight foamed polystyrene with good moldability in order to alleviate rubbing and impact acting on the internal product. Is generally packaged.

  However, such a polystyrene foam has a disadvantage that it has a large environmental load when discarded. As is well known, if the styrene foam is discarded by incineration, the incinerator will be damaged due to high combustion calories, and air pollution will also occur as black smoke and pollutants. On the other hand, when the expanded polystyrene is discarded by the landfill process, the expanded polystyrene is hardly decomposable and bulky, so that it remains in the soil as it is and shortens the life of the landfill disposal site. Therefore, recently, such fractional collection and recycling of polystyrene foam has been studied, but fundamental measures have not yet been established due to the high cost of collection and recycling. It is a fact.

  In contrast, paper is low in calories burned, generates little smoke and harmful substances due to combustion, and is easily decomposable. Therefore, attempts have been made to develop paper with heat insulation and heat retention instead of foamed polystyrene. ing.

  In particular, various types of foamed paper using foamable microcapsules that foam by heat have been proposed as paper having excellent cushioning properties and slip resistance. Examples of the foamable microcapsules include a low-boiling agent such as butane gas in a fine particle outer shell made of a copolymer of methacrylic acid and styrene, a copolymer of acrylonitrile and styrene, a thermoplastic synthetic resin such as vinylidene chloride, and the like. In particular, a microballoon that is a hollow closed cell is formed by softening the outer shell by heating and vaporizing and expanding the low boiling point solvent (Japanese Patent Publication No. 44-7344). No. publication).

  Conventionally, using such foamable microcapsules, as a method of imparting cushioning and anti-slip properties to paper, an internally-added papermaking method for making paper by mixing thermally foamable particles with pulp raw materials, and paper manufacturing There is known a method of spraying or impregnating thermally foamable particles on a wet paper that retains a large amount of water during the process.

  However, all of the foamed paper produced by such a method has foamable microcapsules foamed so that the entire paper layer becomes porous, and the microballoons in which the microcapsules are foamed prevent the binding between pulp fibers. The paper strength and the peel strength between the paper layers are greatly reduced, which causes the disadvantage that the paper is easily torn or torn.

That is, when the foamed paper obtained above is processed and used as a cushion / anti-slip packaging container,
(A) As a result of the foamed microballoon hindering the bonding between the fibers, the compressive strength and rupture strength as the packaging container are reduced, and the strength necessary for the packaging container cannot be ensured, so that the packaging container is crushed.
(B) The peeling strength between the paper layers is low, and peeling occurs at the joint part and the flap part of the packaging container due to the paper peeling.
(C) The surface strength is weak, and the surface of the packaging container is peeled and torn due to rubbing during transportation and movement.
(D) Since the heat-expandable particles are distributed throughout the paper layer and have a porous property, a large amount of adhesive is absorbed during bonding and box making, and as a result, the adhesive is consumed more than necessary. , Expensive to thrive,
(E) Due to the adhesive absorbed in a large amount in the paper layer, the original heat insulating property of the foamed paper is lowered.
Inconveniences such as this occur, so it is not suitable as a paper for use in a cushion / anti-slip packaging container.

  Therefore, a technique for obtaining foamed paper by applying a coating liquid containing thermally foamable particles on the surface of the paper off-machine or on-machine has been invented (Japanese Patent Laid-Open No. 2008-266799, Japanese Patent Laid-Open No. No. 10-204797, Japanese Patent Laid-Open No. 10-21962). In the production of foamed paper by applying such heat-expandable particles to paper, the heat-expandable particles alone are not fixed to the paper, so a coating liquid consisting of heat-expandable particles and a binder is applied to the paper by a coating machine. After coating, it must be done by heating and foaming.

  However, in this method, the expansion ratio of the heat-expandable particles is suppressed by the binder, and the cushioning property and the anti-slip property that are exhibited when the heat-expandable particles are appropriately expanded are lowered.

  Further, when the addition ratio of the heat-foamable particles is increased, the cost of the foamed paper is increased, and the surface strength and printability of the paper are lowered by the heat-foamable particles.

  Furthermore, the method of applying a coating liquid containing thermally foamable particles on the paper surface is limited to a certain amount or less due to the means of coating, so the thickness of the coating layer is also As a result of being thin and restricting the coating amount of the heat-expandable particles themselves, they are inferior to the aforementioned internal addition method and impregnation method in terms of cushioning properties and anti-slip properties, and have not yet been put into practical use.

Japanese Patent Publication No. 44-7344 JP 2008-266799 A Japanese Patent Laid-Open No. 10-204797 Japanese Patent Laid-Open No. 10-21962

  The present invention has been made in view of these disadvantages, and is excellent in cushioning properties and surface strength, processed paper excellent in processing, bonding and boxing suitability to corrugated sheet, corrugated packaging container, interior packaging container, etc. The purpose is to provide.

The invention made to solve the above problems is
In a processed paper comprising a base paper and a coating layer provided on at least one side of the base paper,
The coating layer is formed by application of a coating liquid containing an aqueous resin emulsion, thermally foamable particles, pulp and binder,
The aqueous resin emulsion contains a polymer emulsifier having a carboxyl group in the molecule,
The static friction coefficient measured according to JIS-P8147 (1994) of the coating layer surface is 0.10 or more and 0.25 or less,
The slip angle measured according to JIS-P8147 (1994) on the coating layer surface is 12 degrees or more and 20 degrees or less.

  Since the processed paper contains pulp in the coating liquid for forming the coating layer, this pulp reduces the foaming suppression action of the thermally foamable particles by the binder, and appropriate and effective thermal foaming. Cushioning property can be improved by foaming the conductive particles. In addition, the processed paper contains an aqueous resin emulsion in the coating liquid, and since this aqueous resin emulsion has a polymer emulsifier having a carboxyl group in the molecule, the strength of the surface can be increased and anti-slip properties can be obtained. Can be improved. Furthermore, the processed paper improves the workability of handling processed paper such as packaging by setting the coefficient of static friction and the sliding angle of the coating layer surface within the above ranges, and prevents the package from being damaged or contaminated by rubbing. It is possible to achieve effects such as improved printing suitability and improved wear resistance of the processed paper itself.

The coating layer includes an undercoat layer provided on the surface of the base paper and at least one overcoat layer provided on the surface of the undercoat layer,
This undercoat layer is formed by applying an undercoat layer coating solution containing thermally foamable particles, pulp and binder,
The topcoat layer may be formed by applying a topcoat layer coating solution containing an aqueous resin emulsion.

  Thus, by providing the coating layer with at least two layers separately from the undercoat layer and the overcoat layer, the above-described action can be more effectively expressed. That is, in the undercoat layer, the cushioning property can be enhanced by the thermally foamable particles and the binder, the surface strength can be enhanced by the overcoat layer, and appropriate sliding suitability can be expressed.

  The blending ratio (dry mass ratio) of the pulp contained in the undercoat layer coating liquid to the heat-foamable particles is preferably 0.1 / 99.9 or more and 5.0 / 95.0 or less, and the heat-foamability. The average particle diameter of the particles is preferably 15 μm or more and 20 μm or less. Thus, by setting the blending ratio of the pulp to the heat-expandable particles and the average particle diameter of the heat-expandable particles within the above range, each heat-expandable particle can be made uniform and suitable foaming can be expressed. Therefore, the cushioning property in the undercoat layer can be further improved.

  The binder contained in the undercoat layer coating liquid may contain styrene / butadiene copolymer (SBR) latex as a main component. Thus, by using SBR latex as the main component of the binder in the coating liquid for the undercoat layer, it is possible to suppress the foaming of the thermally foamable particles by the binder while ensuring the necessary strength and adhesiveness as the binder. And cushioning can be improved.

  The blending ratio (dry mass ratio) of the binder contained in the undercoat layer coating solution to the mixture of thermally foamable particles and pulp is preferably 20/100 or more and 60/100 or less. As described above, the binder in the coating liquid for the undercoat layer has the above-mentioned blending ratio, so that it is possible to foam the thermally foamable particles while ensuring an appropriate adhesive force. it can.

The coating amount of the undercoat layer coating solution is preferably 0.4 g / m ² or more and 10 g / m ² or less in terms of solid content per one side of the base paper. As described above, by setting the coating amount of the coating liquid for the undercoat layer within the above range, the cushioning properties necessary for the undercoat layer can be expressed more effectively.

  In the present invention, the “surface of the undercoat layer” refers to an interface of the undercoat layer provided on the surface of the base paper and an interface opposite to the interface (back surface) in contact with the base paper.

  As described above, according to the present invention, it is possible to obtain a processed paper having excellent cushioning properties, anti-slip properties, and surface strength, which enables processing and sticking to corrugated cardboard sheets, corrugated packaging containers, interior packaging containers, and the like. It is possible to obtain a processed paper excellent in suitability and box making.

  In addition, the processed paper according to the present invention is excellent in cushioning properties and anti-slip properties without taking measures such as bonding of paperboard and foamed paper, so that the process can be simplified. Furthermore, since the processed paper is also excellent in surface strength, it has excellent cushioning properties and anti-slip properties used for transportation, storage and protection, which could not be used because conventional foamed paper has low surface strength. It can be used for packaging containers such as cardboard packaging containers and interior packaging containers, and even when used for such packaging containers, problems such as ruled line cracking do not occur.

  In particular, according to the processed paper, when storing bottles, cans, etc. in the above-mentioned corrugated cardboard container, it is possible to prevent the labels on the surface of the bottles, cans, etc. from being soiled by rubbing with the container surface. Has cushioning properties.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. It should be noted that the processed paper according to the present invention is not limited to the following embodiment, and it is needless to say that the configuration can be changed as appropriate without departing from the scope of the claims.

  The processed paper has a base paper and a coating layer provided on one side of the base paper. This coating layer includes two layers, an undercoat layer provided on the surface of the base paper and an overcoat layer provided on the surface of the undercoat layer. Hereinafter, the base paper, the undercoat layer, and the overcoat layer will be described in this order.

(Base paper)
The base paper is composed of a three-layer paper layer including a surface layer, a back layer, and an intermediate layer disposed between the surface layer and the back layer.

  Since the processed paper is processed and used in packaging containers such as cardboard packaging containers and interior packaging containers that are excellent in heat insulation, protection, and heat retention used for transportation, storage, protection, etc. It is required to have excellent strength for bonding and box making and suitable strength as a packaging container.

  Therefore, the surface layer (1) prevents cracking of ruled lines during processing into corrugated cardboard packaging containers, interior packaging containers, etc. (2) has high surface strength, transports, stores and protects the contents, (3) This layer has coating suitability for a coating liquid containing hollow inorganic particles, thermally foamable particles, and a binder, and (4) ensures printing suitability.

  The surface layer can be produced by adding an appropriate amount of a sulfuric acid band and a sizing agent to the raw pulp, generating a raw slurry, and making the raw slurry.

Examples of surface pulp include hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), softwood unbleached kraft pulp (NUKP), and hardwood semi-bleached kraft pulp (LSBKP) , Chemical pulp such as conifer semi-bleached kraft pulp (NSBKP), hardwood sulfite pulp, conifer sulfite pulp;
Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (PGW), Refiner Grand Pulp (RGP), Thermo Grand Pulp (TGP), Chemi Grand Pulp (CGP), Ground Pulp (GP), Thermomechanical Pulp (TMP), etc. Of mechanical pulp;
Waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, leaflet waste paper, office waste paper, corrugated waste paper, Kami white waste paper, Kent waste paper, imitation waste paper, waste paper waste paper, etc. Or disaggregation, deinking, bleached waste paper pulp;
Various known pulps such as pulps chemically or mechanically produced from non-wood fibers such as kenaf, hemp and straw can be used.

  Among these raw material pulps, hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood to achieve the role of the surface layer of the base paper and various quality characteristics as the base paper in a balanced and efficient manner. Preferred are unbleached kraft pulp (LUKP), softwood unbleached kraft pulp (NUKP), or waste paper pulp made from upper white waste paper, Kent waste paper, tea waste paper, and craft envelope waste paper. In addition, when selecting raw material pulp, it is preferable to mix | blend as much waste paper pulp as possible from the reduction of the energy unit and the load given to an environment.

  Moreover, it is preferable that the raw material pulp of the surface layer contains softwood kraft pulp (NKP). Thus, by containing softwood kraft pulp (NKP) having a long fiber length and a thick fiber, it is possible to effectively prevent crease cracks as well as improving the bursting strength.

  The content of softwood kraft pulp (NKP) in the raw material pulp of the surface layer is preferably 5% by mass to 70% by mass, and particularly preferably 25% by mass to 70% by mass. When the content of NKP in the raw material pulp of the surface layer is smaller than the above range, the fiber length is long and the content ratio of NKP with thick fibers decreases, so that the rupture strength tends to be lowered or the crease line cracking tends to occur during box making. There is. On the other hand, if the content of NKP exceeds the above range, it may cause unevenness in strength due to uneven texture and a decrease in appearance, and may be applied when a coating liquid containing thermally foamable particles, pulp and binder is applied. Since the liquid penetrates very much into the surface of the base paper, there is a risk that a coating layer having cushioning properties and anti-slip properties cannot be efficiently formed.

As the surface layer of the attached amount is preferably 15 g / ^{m 2} or more 45 g / ^{m 2} or less, 25 g / ^{m 2} or more 40 g / ^{m 2} or less is particularly preferred. When the amount of the surface layer is smaller than the above range, the strength of the surface layer is lowered, and therefore, ruled line cracks, square cracks and the like are likely to occur during box making. On the other hand, when the amount of the surface layer exceeds the above range, an expensive raw material pulp is used for the surface layer as compared with the middle layer, which results in an increase in cost.

In addition, “attachment amount (g / m ² )” means that the layer is peeled by the following procedure, and the basis weight of each layer is measured according to “paper and paperboard—basis weight measurement method” described in JIS-P8124. It is the value. The delamination is performed according to the following procedure. First, each sample obtained from each sample is immersed in water at room temperature for about 1 hour. Next, each sample immersed in water is wound around a round bar of about 10 mmφ starting from a corner, and this round bar is rolled to squeeze each sample. This operation is repeated starting from all four corners of each sample, and ironing force is applied to the sample from each direction. As a result, a part of the layers of each sample is peeled off, and this is used to separate the layers into layers. After delamination, each layer of each sample is sufficiently dried with a hot air dryer or the like and used for the test.

  Further, the freeness of the raw material pulp is preferably 280 cc or more and 530 cc or less, and more preferably 320 cc or more and 430 cc or less. If the freeness of the raw material pulp in the surface layer is smaller than the above range, the fiber length of the raw material pulp will be shortened, so that the burst strength is reduced, and it is easy to cause ruled line cracks and square cracks during box making, while the freeness is in the above range. If it exceeds 1, the fiber length is long, and the binder contained in the coating liquid will permeate the surface layer excessively, making it difficult to keep the thermally foamable particles on the surface, and the thermally foamable particles may peel off. is there.

  Here, “freeness” means that after the sample was disaggregated with a standard disaggregator according to JIS-P8220, the freeness was measured with a Canadian standard freeness tester according to JIS-P8121. Value.

  Next, the middle layer and the back layer will be described. The method for producing the middle layer and the back layer is the same as the method for producing the surface layer. In the specific example, an appropriate amount of a sulfuric acid band and a sizing agent are added to the raw material pulp to produce a raw material slurry, and the raw material slurry is made into paper. Can be done.

  As the raw material pulp for the middle layer and the back layer, various known pulps can be used similarly to the surface layer. Among these, considering the role of the backing layer of the base paper and achieving various quality characteristics in a balanced and efficient manner, hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft Pulp (LUKP), softwood unbleached kraft pulp (NUKP), hardwood semi-bleached kraft pulp (LSBKP), softwood half-bleached kraft pulp (NSBKP), or waste paper pulp made from tea waste paper or kraft waste paper is preferred. In addition, when selecting raw material pulp, it is preferable to mix | blend as much waste paper pulp as possible from the reduction of the energy unit and the load given to an environment.

  Moreover, it is preferable to contain softwood kraft pulp (NKP) in the raw material pulp of a middle layer and a back layer similarly to the surface layer. Thus, by containing softwood kraft pulp (NKP) having a long fiber length and a thick fiber, it is possible to effectively prevent crease cracks as well as improving the bursting strength.

  The content of the softwood kraft pulp (NKP) in the raw material pulp of the middle layer and the back layer is preferably 10% by mass or more and 80% by mass or less, and particularly preferably 40% by mass or more and 60% by mass or less. By setting the content of NKP in the raw pulp of the middle layer and the back layer within the above range, it is possible to effectively improve the bursting strength and to prevent ruled line cracks and square cracks during container packaging of the processed paper.

  Furthermore, the freeness of the raw pulp of the middle layer and the back layer is preferably 280 cc or more and 480 cc or less in consideration of effectively preventing rupture, ruled line cracking, square cracking, etc. during container packaging processing as with the surface layer. In addition, considering prevention of a decrease in tensile strength, it is more preferable that the amount be 300 cc or more and 440 cc or less.

The basis weight of the base paper, but are not limited to, preferably 150 g / ^{m 2} or more 400 g / ^{m 2} or less in Examples, and particularly preferably 170 g / ^{m 2} or more 300 g / ^{m 2} or less. In addition, this "basis weight" is a value measured based on JIS-P8113. If the basis weight of the base paper is smaller than the above range, there is a concern of poor coating suitability at the time of manufacturing the base paper. On the other hand, when the basis weight of the base paper exceeds the above range, it is difficult to process the packaging container because the thickness is too large, which is not preferable.

  The paper making method of the base paper is not particularly limited, and any of acidic paper making method, neutral paper making method and alkaline paper making method may be used. Also, the paper machine is not particularly limited, and various known ones such as a long net paper machine, a twin wire paper machine, a circular net paper machine, and a short net combination machine can be used. .

(Undercoat layer)
The undercoat layer is formed by applying an undercoat layer coating solution containing heat-expandable particles, pulp, and a binder. The undercoat layer can mainly impart cushioning properties to the processed paper.

  These thermally foamable particles are those in which a low-boiling solvent is enclosed in a microcapsule-shaped outer shell composed of a thermoplastic synthetic resin, and generally those having an average particle diameter of 5 μm or more and 30 μm or less are used.

  Examples of the thermoplastic synthetic resin constituting the outer shell of the thermally foamable particles include copolymers such as vinylidene chloride, acrylic acid ester, acrylonitrile, and methacrylic acid ester. Examples of the low boiling point solvent enclosed in the outer shell include isobutane, pentane, petroleum ether, hexane, low boiling point halogenated hydrocarbon, and methylsilane.

  Such heat-expandable particles are heated at 80 to 200 ° C. to evaporate the low-boiling solvent encapsulated to increase the vapor pressure, expand the outer shell to form closed cells, and have a diameter of 4 to 5 times, volume expands 50-130 times.

  In addition, since the temperature of the paper drying process in the paper making process and the paper processing process is 80 to 200 ° C, the thermally foamable particles have a foaming start temperature of 75 ° C or higher and 85 ° C or lower, and a maximum expansion temperature. Is preferably 105 ° C. or higher and 120 ° C. or lower. If the foaming start temperature is less than 75 ° C. and the maximum expansion temperature is less than 105 ° C., the heat-expandable particles expand rapidly due to heat, which may cause operational troubles that contaminate the dryer surface. On the other hand, when the foaming start temperature is 85 ° C. and the maximum expansion temperature exceeds 120 ° C., the thermally foamable particles are not sufficiently expanded, and therefore cushioning properties are hindered.

  The average particle diameter of the thermally foamable particles is preferably 15 μm or more and 20 μm or less. If the average particle size of the heat-expandable particles is smaller than the above range, the thickness of the undercoat layer (cushion layer) cannot be secured sufficiently, and therefore it becomes impossible to prevent damage, and conversely, the average particle size of the heat-expandable particles If the value exceeds the above range, the thickness of the undercoat layer (cushion layer) varies, and the thickness of the undercoat layer (cushion layer) increases more than necessary.

  Examples of such thermally foamable particles include “Matsumoto Microsphere F-30D”, “F-30GS”, “F-20D”, “F-50D” manufactured by Matsumoto Yushi Seiyaku Co., Ltd., Various known products such as “Expancel WU” and “Same DU” sold by Nippon Philite Co., Ltd. can be used, but the particle size of the thermally expandable particles before expansion, coating suitability, and drying process From the viewpoint of foaming property, particularly heat-foamable particles made of an acrylic copolymer are preferable.

  In the drying step, the thermally foamable particles are foamed and expanded by a dryer, and the processed paper is made bulky to give cushioning properties and slip resistance. In addition, it is preferable that the heating for expanding the thermally foamable particles is expanded by foaming to a desired size of the processed paper by one heating.

  The pulp contained in the undercoat layer coating liquid suitably foams the thermally foamable particles and contributes to imparting cushioning properties to the processed paper.

  As the said pulp, the various pulp similar to the raw material pulp used for the surface layer of the above-mentioned base paper can be used. Among these pulps, considering the role given to the cushioning properties of the processed paper and various quality characteristics as the processed paper in a balanced and efficient manner, especially hardwood bleached kraft pulp (LBKP), conifers It is preferable to use waste paper pulp produced from bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), and softwood unbleached kraft pulp (NUKP).

  The mixing ratio (dry mass ratio) of the pulp to the heat-expandable particles in the undercoat layer coating solution is preferably 0.1 / 99.9 or more and 5.0 / 95.0 or less, and 0.5 / 99.5. The ratio is more preferably 1.5 / 98.5 or less. If the blending ratio of the pulp to the heat-expandable particles is smaller than the above range, the entanglement between the foamed particles and the pulp fiber is deteriorated and the adhesive strength is weakened. Conversely, the blending ratio of the pulp to the heat-expandable particles is within the above range. When it exceeds, the coating liquid for undercoat layer will thicken and it will become difficult to coat, and cushioning properties and anti-slip properties will decrease.

  As described above, by adding the thermally foamable particles and the pulp to the coating liquid for the undercoat layer, the undercoat layer can be given a thickness, and thereby cushioning properties can be obtained.

  The binder contained in the coating liquid for the undercoat layer can improve the surface strength of the processed paper, impart appropriate anti-slip properties, and break the ruled line when the processed paper is processed into a packaging container, etc. And the occurrence of paper peeling and tearing due to rubbing with the contents during transportation and storage can be prevented.

  As this binder, for example, various known materials such as vinyl acetate, acrylic, polyvinyl alcohol (PVA), styrene / butadiene copolymer (SBR) latex, starch, and polyacrylamide (PAM) can be used.

  However, since the undercoat layer coating liquid to be applied to the processed paper also contains thermally foamable particles and pulp as described above, the surface strength of the base paper depends on the type and properties of the binder. There is a risk of lowering.

  Moreover, although a binder with high hardness is excellent in the improvement effect of surface strength, it will inhibit expansion | swelling of a thermally foamable particle. That is, since the heat-expandable particles exhibit cushioning properties and anti-slip properties by heating and expanding and foaming as described above, if the expansion of the heat-expandable particles is hindered, the cushioning properties and anti-slip properties are reduced. It becomes impossible to get sex. In addition, the processed paper is often processed into a packaging container. However, when the processed paper is processed into a packaging container and a strong bending force is applied to the ruled line portion (folded portion), the coating layer (undercoat layer) is cracked. Not required.

  For this reason, among the various binders described above, it is particularly preferable to use SBR latex as the main component. That is, SBR has good adhesiveness with thermally foamable particles and pulp, and is excellent in elongation at the time of bending, so that it does not hinder expansion and foaming of thermally foamable particles, and in addition, the processed paper The inconvenience of ruled line cracking when processed into a packaging container is less likely to occur.

  The glass transition temperature of the binder is preferably −50 ° C. or higher and 30 ° C. or lower, and particularly preferably −30 ° C. or higher and 20 ° C. or lower. When the binder is in such a glass transition temperature range, the viscosity during coating of the coating liquid for the undercoat layer is low, it is a soft property with excellent bendability, and after drying it can obtain an appropriate surface strength improvement effect Therefore, the foamability of the heat-expandable particles and the processability of the processed paper are further improved.

  The blending ratio (dry mass ratio) of the binder to the mixture of thermally foamable particles and pulp is preferably 20/100 or more and 60/100 or less, and more preferably 40/100 or more and 50/100 or less. . If the blending ratio (dry mass ratio) of the binder to the thermally foamable particles and the pulp is smaller than the above range, the adhesiveness of the thermally foamable particles and the pulp may be lowered. On the other hand, when the blending ratio (dry mass ratio) of the binder exceeds the above range, the foaming effect of the heat-foamable particles and pulp and the foaming effect of the heat-foamable particles are hardly improved, and the cushioning property and the slip resistance are lowered. Moreover, the manufacturing cost is high.

The thermally foamable particles can be internally added to the raw material pulp of each layer constituting the base paper. However, since the specific gravity of the heat-expandable particles is 0.9 to 1.2 g / cm ³ , it is difficult to uniformly disperse them in the thickness direction during paper making if they are added internally, and cushioning properties can be effectively obtained. I can't. Moreover, in order to obtain desired cushioning properties, it is necessary to add excessively heat-foamable particles. Excessive addition of such heat-expandable particles leads to an increase in production cost, and in terms of quality, surface strength is reduced, various strengths such as compressive strength, burst strength, tensile strength, and tear strength are reduced. In order to cause inconveniences such as a decrease in suitability and the occurrence of curling due to a difference between the front and back sides, it is preferable to form a coating layer by applying a coating solution containing at least thermally foamable particles, pulp and binder.

The coating amount of the undercoat layer coating solution, a solid per base paper sided min, 0.4 g / ^{m 2} or more 10 g / ^{m 2} are preferred, 1 g / ^{m 2} or more 6 g / ^{m 2} or less Particularly preferred. When the coating amount of the undercoat layer coating solution is smaller than the above range, cushioning properties are deteriorated and slip resistance is also lowered. On the contrary, if the coating amount of the coating solution for the undercoat layer exceeds the above range, the undercoat layer (cushion layer) becomes thick and the expansion of the thermally foamable particles is not preferable. Although it is possible to increase the coating amount of the coating solution for the undercoat layer, excessive coating reduces production efficiency and increases the amount of expensive thermally foamable particles. However, there is a risk of a significant increase in cost.

  In addition, as a method of applying the coating liquid for undercoat layer, it can apply by well-known coating means, such as a bar coater, a rod coater, and an air knife. Moreover, it can also print by well-known printing means, such as a gravure printing machine and a flexographic printing machine. Among these, a coating machine such as a rod coater or an air knife capable of arbitrarily changing the coating amount of the coating liquid is preferable.

  Moreover, it is preferable to perform a calendar process on the base paper in the previous step of applying the undercoat layer coating solution. As a result, the surface of the base paper becomes dense, and the coating liquid can be efficiently retained on the surface of the base paper, so that the processed paper can be made more excellent in cushioning properties. Furthermore, the undercoat layer coating solution can be applied after the surface of the base paper is coated with a chemical or various paper coating agents.

(Overcoat layer)
The topcoat layer is formed by applying a topcoat layer coating solution containing at least an aqueous resin emulsion.

  This aqueous resin emulsion is obtained by emulsion polymerization of a radical polymerizable monomer in the presence of a polymer emulsifier having a carboxyl group in the molecule. By using a polymer emulsifier having a carboxyl group in the molecule, an excellent anti-slip property when an overcoat layer is formed is expressed.

  The polymer emulsifier having a carboxyl group in the molecule includes a copolymer of a carboxylic acid and / or an acid anhydride having a radical polymerizable unsaturated double bond and another copolymerizable radical polymerizable monomer. A coalescence can be used conveniently.

  Examples of the carboxylic acid having a radical polymerizable unsaturated double bond include monocarboxylic acids having about 3 to 4 carbon atoms such as (meth) acrylic acid and crotonic acid; maleic acid, fumaric acid, citraconic acid, Examples thereof include dicarboxylic acids having about 4 to 5 carbon atoms such as itaconic acid; monoalkyl esters, monohydroxyalkyl esters, monoamides thereof and the like. Examples of the acid anhydride having a radical polymerizable unsaturated double bond include maleic anhydride, citraconic anhydride, itaconic anhydride and the like.

  Examples of the monoesters, monohydroxyalkyl esters and monoamides of the dicarboxylic acid include the dicarboxylic acid component, a monoalcohol component having about 1 to 18 carbon atoms, which will be described later, or about 2 to 8 carbon atoms. And a monoester compound with an amine component having about 1 to 18 carbon atoms.

  Examples of the monoalcohol component include methanol, ethanol, propanol, butanol, hexanol, octanol, decanol, dodecanol, and octadecanol. Examples of the diol component include ethylene glycol, propylene glycol, butylene glycol and the like. Examples of the amine component include ethylamine, diethylamine, butylamine, hexylamine, octylamine, decylamine, and octadecylamine.

  Among these carboxylic acids and / or acid anhydrides having a radically polymerizable unsaturated double bond, monocarboxylic acids are preferable from the viewpoint of the emulsifying ability of the resulting polymer emulsifier, and acrylic acid or methacrylic acid is particularly preferable. is there.

  The amount of the carboxylic acid and / or acid anhydride having a radically polymerizable unsaturated double bond is preferably such that the acid value of the polymer emulsifier obtained by polymerizing all the monomer components is in the range of 50 to 350. . When the acid value of the polymer emulsifier is less than 50, the slip resistance of the processed paper obtained is lowered. On the other hand, when the acid value of the polymer emulsifier is more than 350, the compatibility with the aqueous wax emulsion described later is lowered. In addition, the slip resistance of the processed paper obtained tends to decrease, which is not preferable.

  Examples of the other copolymerizable radical polymerizable monomers include acrylic monomers, styrene monomers, and maleic monomers.

  Examples of the acrylic monomer include (meth) acrylic acid alkyl ester having 1 to 18 carbon atoms, alkyl amide having 1 to 18 carbon atoms, and hydroxyalkyl ester having 2 to 4 carbon atoms. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, methyl ( Examples include meth) acrylamide, ethyl (meth) acrylamide, butyl (meth) acrylamide, hexyl (meth) acrylamide, and 2-hydroxyethyl (meth) acrylate.

  Examples of the styrene monomer include styrene having about 8 to 10 carbon atoms and derivatives thereof, and specific examples include α-methylstyrene, chlorostyrene, vinyltoluene and the like.

  Examples of the maleic monomer include maleic acid dialkyl esters having 1 to 18 carbon atoms, dialkyl amides having 1 to 18 carbon atoms, and di (hydroxyalkyl) esters having 2 to 4 carbon atoms. Specifically, dimethyl malate, diethyl malate, dibutyl malate, dioctyl malate, bis (2-hydroxyethyl) maleate, dimethylamide maleate, diethylamide maleate, dibutylamide maleate, dioctylamide maleate Etc.

  As a method for producing a polymer emulsifier from a carboxylic acid and / or an acid anhydride having a radical polymerizable unsaturated double bond and other copolymerizable radical polymerizable monomers, polymerization is conducted in an organic solvent. In the presence of an initiator, the monomer component (a carboxylic acid and / or acid anhydride having a radical polymerizable unsaturated double bond and another copolymerizable radical polymerizable monomer) is reacted at a predetermined temperature and After reacting for the reaction time, a method of distilling off the organic solvent can be used.

  Examples of usable organic solvents include ester organic solvents such as ethyl acetate and isopropyl acetate; ketone organic solvents such as acetone and methyl ethyl ketone; lower alcohol organic solvents; glycol and derivatives thereof. On the other hand, usable polymerization initiators include, for example, persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate; organic peroxides such as benzoyl hydroperoxide; azo compounds such as azobisisobutyronitrile. And redox initiators combined with a reducing agent as necessary.

  In addition, when the processed paper obtained by the method of the present invention is used in a field including a heating step in which the processing temperature is 120 ° C. or higher, such as a corrugated paste applying step, the processed paper has heat resistance. From the viewpoint of imparting, the glass transition temperature of the polymer emulsifier is preferably 60 ° C. or higher.

  Next, as the radical polymerizable monomer that is subjected to emulsion polymerization in the presence of a polymer emulsifier, in addition to the acrylic monomer, styrene monomer, maleic monomer, saturated carboxylic acid And vinyl esters. Among these radical polymerizable monomers, acrylic monomers and styrene monomers are preferable because of the dispersibility of the aqueous resin emulsion.

  As the vinyl ester of the saturated carboxylic acid, for example, a vinyl ester of a saturated carboxylic acid having 2 to 18 carbon atoms is used, and specific examples include vinyl acetate, vinyl propionate, vinyl laurate, and vinyl stearate. It is done.

  The radical polymerizable monomer may be used alone or in combination within a range where the glass transition temperature of the resulting polymer is 90 ° C. or lower. When the glass transition temperature of the obtained polymer is higher than 90 ° C., the slip resistance of the processed paper tends to deteriorate, which is not preferable.

  As a method for producing an aqueous resin emulsion using the above-mentioned polymer emulsifier and a radical polymerizable monomer provided for emulsion polymerization, the polymer emulsifier is dissolved in an aqueous solution of an alkali compound and then subjected to emulsion polymerization. A method in which a mixture of a monomer and a polymerization initiator is added and reacted at a predetermined temperature and reaction time is employed.

  In the above-mentioned production method, examples of the alkali compound used for dissolving the polymer emulsifier in the aqueous medium include ammonia, dimethylethanolamine, diethylethanolamine, triethylamine, tributylamine, morpholine, diethanolamine, and triethanolamine. Amines can be used. Moreover, as a polymerization initiator, the thing similar to the polymerization initiator used in order to manufacture the said polymeric emulsifier can be used.

  The blending ratio of the polymer emulsifier to the radical polymerizable monomer (polymer emulsifier / radical polymerizable monomer) in the coating solution for the topcoat layer is preferably 20/80 or more and 50/50 or less, preferably 30/70 or more. Particularly preferred is 45/55 or less. When the blending ratio of the polymer emulsifier is lower than the above range, the stability of the resulting aqueous resin emulsion is lowered. On the other hand, when the blending ratio of the polymer emulsifier exceeds the above range, the slip resistance tends to deteriorate.

  The topcoat layer coating liquid may contain a water-dispersible wax emulsion in addition to the aqueous resin emulsion. Thus, by containing a water-dispersible wax emulsion in the coating liquid for topcoat layer, the strength of the topcoat layer can be increased and the water repellency can be enhanced.

  The aqueous wax emulsion is preferably obtained by dispersing a wax having a melting point in the range of 50 to 120 ° C. in water in the presence of an emulsifier. Examples of the wax that can be used here include paraffin wax, microclostalline wax, carnauba wax, montan wax, polyethylene wax, and polypropylene wax.

  The emulsifier used for emulsifying the wax in water is not particularly limited, and any of nonionic surfactants, anionic surfactants, cationic surfactants and the above-described polymer emulsifiers can be used. In order to maintain a high water repellency, the content of the emulsifier in the aqueous wax emulsion is preferably small. For example, the content is preferably 10% by mass or less based on the amount of the wax.

  The blending ratio (aqueous wax emulsion / aqueous resin emulsion) of the aqueous wax emulsion to the aqueous resin emulsion in the coating liquid for the topcoat layer is preferably 2/98 or more and 70/30 or less in terms of solid content mass ratio. Here, the solid content of the aqueous resin emulsion means the total solid content, and the solid content of the aqueous wax emulsion means the wax. When the blending ratio of the aqueous wax emulsion is less than the above range, the slip suitability of the processed paper obtained is lowered. On the other hand, when the blending ratio of the aqueous wax emulsion is more than the above range, the post-processing suitability is degraded, and the paper loss treatment is performed. It is difficult to do so, which is not preferable.

  Here, when the blending ratio of the aqueous wax emulsion is smaller than 5/95 and close to 2/98, the slip suitability tends to deteriorate. Further, as a method for improving the slip suitability in this system, there is a hot press method, which will be described later.

  Further, when the processed paper is used for applications requiring high slipping property and heat resistance, a water-soluble metal complex salt capable of reacting with a carboxyl group is crosslinked in the coating solution for the topcoat layer used in the present invention. By adding as an agent, good results can be obtained.

  Examples of water-soluble metal complex salts that can be used here include polyvalent metals such as Zn, Zr, Sn, and Ti, inorganic acids such as carbonic acid and phosphoric acid, or tannin, gallic acid, humic acid, salicylic acid, benzoic acid, and paraoxybenzoic acid. Examples thereof include those obtained by reacting with an organic acid such as an acid to form a metal complex salt, and further neutralized with amines such as ammonia, ethylenediamine, methylamine, ethylamine, dimethylamine, diethylamine, dimethylethanolamine, and so on.

  Specific examples of the water-soluble metal complex salt include zinc carbonate ammonium, zinc phosphate ammonium, zinc gallate ammonium, zinc humate, zinc benzoate, and similar metal complex salts of tin, zirconium, and titanium. .

  As a method for producing these water-soluble metal complex salts, first, a slurry is prepared by adding an aqueous solution of ammonia, amine or the like to a hydroxide or oxide of a polyvalent metal, and the above acid or its ammonium salt or amine salt is prepared. Can be obtained by water-solubilizing the metal compound.

  The amount of the water-soluble metal complex salt to be used is preferably 0.2 equivalents or more and 1.5 equivalents or less, and 0.5 equivalents or more and 1 equivalent or less with respect to all carboxyl groups present in the coating liquid composition for top coating. 5 equivalents or less are particularly preferred. Such metal cross-linking agent stoichiometrically reacts with one equivalent of one carboxyl group, but the reaction rate is not 100%, so about 1.5 equivalents to crosslink all carboxyl groups. It is preferable to contain. Although the addition of a metal cross-linking agent exceeding 1.5 equivalents is not particularly inconvenient, the effect is almost the same as when 1.5 equivalents are added.

  In addition, various water-soluble resins, water-miscible solvents, antifoaming agents, and the like can be appropriately added to the coating liquid for topcoat coating as long as storage stability, slippage suitability, and disaggregation property are not deteriorated.

  The method for producing the coating liquid for the topcoat layer from these materials is not particularly limited, and for example, a known stirrer such as a high-speed mixer is used, and a predetermined amount of each material is stirred and mixed. can do.

  As a method for applying the top coating liquid, it can be applied to the paper surface by any of a normal roll coater, doctor blade coater, knife edge coater, curtain coater, gravure coater, bar coater and the like.

Furthermore, the coating liquid for the topcoat layer can be applied after a drug or various paper coating agents are applied to the surface of the undercoat layer. In addition, as a coating amount (wet mass) of the coating liquid for top coat layers, 6-20 g / m < ² > is preferable by one time or multiple times of coating, and 10-15 g / m < ² > is more preferable. When the coating amount of the coating liquid for topcoat layer is less than 6 g / m ² , sufficient wear resistance cannot be provided. On the other hand, when the coating amount of the coating liquid for the top coat layer exceeds 20 g / m ² , the wear resistance becomes saturated, and in addition, the slip suitability decreases.

  As a drying method after the coating liquid for topcoat layer is applied, various heaters such as a hot air heater and an infrared heater can be used. In addition, higher slip suitability can be obtained by heating the overcoat layer to the melting point of the wax or higher. As a method for heating the coated surface, a hot air heater or an infrared heater may be used. However, since the amount of heat applied is small, heating is performed by contacting the surface of a hot plate or a hot roll, that is, substantially without applying pressure. The method to do is more effective.

  Furthermore, when the acid value of the polymer emulsifier which is the composition of the coating liquid for the top coat layer of the processed paper is 250 or more and 350 or less, and / or the solid content mass ratio of the aqueous wax emulsion to the aqueous resin emulsion is 2 When the temperature is in the range of / 98 or more and 5/95 or less, the surface temperature is higher than the melting point of the wax and is preferably pressed with a hot roll heated to 90 to 180 ° C. under a linear pressure of 60 to 150 kg / cm. By this method, a processed paper having high slip suitability can be produced.

  The processed paper obtained from these methods has a high surface strength and slipping suitability, excellent post-working suitability, and good disaggregation properties with a smaller coating amount of the topcoat layer coating solution. The processed paper has excellent cushioning properties, anti-slip properties, and surface strength, and is excellent in processing, laminating and boxing suitability for corrugated cardboard sheets, cardboard packaging containers, interior packaging containers, and the like.

  The coefficient of static friction measured according to JIS-P8147 (1994) on the coated layer surface of the processed paper is 0.10 or more and 0.25 or less, and preferably 0.14 or more and 0.20 or less. The sliding angle measured according to JIS-P8147 (1994) on the surface of the coating layer is 12 degrees or more and 20 degrees or less, and preferably 12 degrees or more and 18 degrees or less. By making the coefficient of static friction and sliding angle of the coated layer surface within the above ranges, the processed paper improves the workability of handling processed paper such as packaging, and prevents the package from being damaged or contaminated by rubbing. Such effects as improving printing suitability and improving wear resistance of the processed paper itself can be obtained. In addition, if the static friction coefficient and the sliding angle on the surface of the processed paper are smaller than the above ranges, handling during handling becomes difficult, and conversely, if the static friction coefficient and the sliding angle exceed the above ranges, the wear resistance decreases.

  The processed paper of the present invention is not limited to the above embodiment. For example, the base paper is a processed paper having four layers of a front layer, two layers, and a back layer, and further increases the number of layers of the middle layer. Alternatively, the processed paper may have five or more layers, or the base paper may be a single-layer processed paper. Further, the coating layer may be formed by mixing the coating solution for the overcoat layer and the coating solution for the undercoat layer, and providing one coating layer on the surface of the base paper. Thus, even if it is set as a one-layer coating layer, fixed cushioning property and slipperiness can be expressed, and a work process can be simplified. Furthermore, it is also possible to provide a coating layer on both surfaces of the base paper, and the cushioning property, slip resistance and surface strength of the processed paper are further improved.

  EXAMPLES Hereinafter, although this invention is explained in full detail based on an Example, this invention is not interpreted limitedly based on description of this Example. In addition, in a present Example, the numerical value which shows a mixing | blending, a density | concentration, etc. is a numerical value of the solid content or the mass reference | standard of an active ingredient.

  In order to compare and examine 38 types of processed paper (Examples 1 to 38) according to the present invention and Examples 1 to 38, 6 types of processed paper (Comparative Examples 1 to 6) were prepared. The manufacturing conditions for each sample are shown below. Unless otherwise specified, the raw material composition of each layer of the base paper, the freeness, the chemical addition conditions, etc. are the same.

[Example 1]
[Manufacture of base paper]
<1> Surface layer After blending 30% by weight of softwood bleached kraft pulp (NBKP), 30% by weight of hardwood bleached kraft pulp (LBKP) and 40% by weight of high-quality waste paper pulp, a sulfuric acid band is added to the raw pulp whose disintegration freeness is adjusted to 380cc. 4% by mass and 0.3% by mass of a sizing agent (R50 manufactured by Modern Chemical Industry Co., Ltd.) were added to produce a raw material slurry for the surface layer. Here, “disaggregation freeness (cc)” means that each sample is cut into a size of about 3 cm ² to obtain a test piece having a weight of about 25 g, and this test piece is immersed in 1 liter of water for 24 hours. , In accordance with JIS-P8220, disintegrate for 15 minutes with a standard disintegrator, and visually confirm that the test piece is completely disaggregated, and then in accordance with JIS-P8121, the Canadian standard freeness tester The freeness value measured in the above.

<2> Middle layer (1)
After blending 60% by weight of Kent waste paper pulp (NBKP) and 40% by weight of high-quality waste paper pulp, 4% by weight of sulfuric acid band and sizing agent (R50 manufactured by Modern Chemical Industry Co., Ltd.) were added to the raw pulp whose disintegration freeness was adjusted to 350cc. 3% by mass was added to produce a raw slurry.

<3> Middle layer (2), (3) and back layer 100% by mass of the old paper pulp is adjusted to 230 cc disintegration freeness, and 4% by mass of sulfuric acid band and 0.3% by mass of sizing agent (R50) The raw material slurry was produced.

Using these raw material slurries, the surface layer, the middle layer (1), the middle layer (2), the middle layer (3) and the back layer of the five paper layers are combined with an ultra former (manufactured by Kobayashi Manufacturing Co., Ltd.). The surface layer is 30 g / m ² , the middle layer (1) is 40 g / m ² , the middle layer (2), the middle layer (3), the back layer is 50 g / m ² , and the overall basis weight is 220 g / m ² . A base paper was obtained.

[Adjustment of undercoat coating solution]
A mixture of heat-expandable particles having an average particle size of 20 μm (Matsumoto Oils and Fats Pharmaceutical Co., Ltd., Matsumoto Microsphere F-46) and pulp is prepared, and the glass transition temperature (Tg) is −5 with respect to 100 parts by mass of this mixture. A coating solution was prepared by blending 50 parts by mass of styrene / butadiene copolymer (SBR) latex having a temperature of ° C.

[Adjustment of coating liquid for top coating]
<1> Synthesis of aqueous resin emulsion After charging 400 parts of ethyl acetate into a flask and heating, 50 parts of acrylic acid as a monomer component, 50 parts of methyl methacrylate, 40 parts of styrene and 2 parts of benzoyl hydroperoxide as a reaction initiator. The mixture was added dropwise over 4 hours. Further, polymerization was performed for 2 hours while maintaining the same temperature, and then the solvent was evaporated to obtain a polymer emulsifier.

  In a flask, a polymer emulsifier component comprising 160 parts of the above polymer emulsifier, water 550 parts and 25% aqueous ammonia 50 parts, methyl methacrylate 120 parts, styrene 120 parts (emulsion polymerization component) and benzoyl hydroperoxide as a reaction initiator One part was dropped and emulsion polymerization was performed to obtain an aqueous resin emulsion having a solid content of 40%.

<2> Preparation with aqueous wax emulsion The aqueous resin emulsion and aqueous wax emulsion were stirred and mixed at a ratio of 1: 1 to obtain a coating solution for top coating. As the aqueous wax emulsion, one having a solid content of 45% and a melting point of 61 ° C. using a paraffin wax as the wax was used.

[Manufacture of processed paper]
On one side of the base paper by installing the on-machine a rod coater in a paper machine, was 5 g / m ² coated with the adjusted base coat layer coating solution as described above on one surface per solids, the surface temperature of the dryer cylinders The thermally foamable particles were foamed with an after dryer at about 100 ° C. Thereafter, the prepared coating liquid for topcoat layer was coated twice on the surface of the undercoat layer (total coating amount 12 g / m ² ; wet mass) to obtain a processed paper of Example 1.

[Examples 2 to 29]
Except for changing the average particle size, foaming start temperature, maximum expansion temperature, blending ratio, blending ratio and type of binder, and coating amount in the undercoat layer coating liquid as shown in Table 1, respectively. In the same manner as in Example 1, processed papers of Examples 2 to 29 were obtained.

  In addition, the compounding ratio of the thermally foamable particles and pulp in Table 1 is the dry mass ratio of the thermally foamable particles or pulp to the total dry mass of the thermally foamable particles and pulp. Moreover, PVA in the kind of binder is polyvinyl alcohol. The blending ratio of the binder is the dry mass of the binder with respect to the dry mass of the mixture of the thermally foamable particles and the pulp. The coating amount is the solid content mass of the coating liquid for topcoat layer.

[Examples 30 to 38]
Examples 30 to 34 were obtained in the same manner as in Example 5 except that the coating liquid coating amount for the topcoat layer was changed. A processed paper of Examples 35 to 38 was obtained in the same manner as in Example 5 except that the polymer emulsifier of the aqueous resin emulsion contained in the coating liquid for topcoat layer was changed to the monomer component shown in Table 2 other than acrylic acid. .

[Comparative Examples 1-2]
Processed papers of Comparative Examples 1 and 2 were obtained in the same manner as in Example 5 except that the average particle size of the thermally foamable particles contained in the undercoat layer coating solution was changed as shown in Table 1.

[Comparative Example 3]
A processed paper of Comparative Example 3 was obtained in the same manner as in Example 5 except that the undercoat layer coating solution was changed so as not to contain pulp.

[Comparative Examples 4 to 6]
Comparative Example 4 (coating amount 30 g / m ² ) and Comparative Example 5 (no overcoating layer coating) were obtained in the same manner as Example 5 except that the coating liquid coating amount for the top coating layer was changed. A processed paper of Comparative Example 6 was obtained in the same manner as in Example 5 except that the polymer emulsifier of the aqueous resin emulsion contained in the coating liquid for topcoat layer was changed from acrylic acid to vinyl sulfonic acid.

  About all these Examples and Comparative Examples, the test which evaluates the basic weight, surface strength, and the quality of a sliding angle was done, and the result is shown in Table 1 and Table 2. This evaluation test was performed under environmental conditions of a temperature of 23 ° C. ± 1 ° C. and a humidity of 50 ± 2% in accordance with JIS-P8111.

“Basis weight (g / m ² )” in Tables 1 and 2 is the total basis weight of each sample, ie, the entire processed paper, and is described in JIS-P8142. It is a value measured according to.

  In the evaluation of cushioning properties (feel of touch) in quality evaluation, a mark “◯” indicates a good case, a mark “◎” indicates an excellent case, a mark “Δ” indicates normal, and a mark “×” indicates a bad case.

  The abrasion resistance test is a method in which a frictional action under a certain condition is applied to the surface of a test piece, and the resistance to the friction of the surface is measured, and the surface to be coated is 50 by a method according to JIS-P8136 (1994). The surface condition after the test was visually observed and evaluated according to the following criteria (testing machine: “Gakushin-type abrasion resistance testing machine” manufactured by Toyo Seiki Co., Ltd.).

◎: Paper peeling is not recognized ○: 1/5 or less of the contact surface is peeled △: 1/5 to 1/2 of the contact surface is peeled ×: 2 or more of the contact surface is peeled Is accepted

  The sliding angle means the angle at which the weight attached with the test piece starts to move under a certain condition, and is carried out between the coated surfaces by a method according to the JIS-P8147 (1994) inclination method, and the average value of five times is rounded. (Testing machine: “slip angle measuring device” manufactured by Toyo Seiki Co., Ltd.).

  The coefficient of static friction is the ratio of the frictional force that tries to prevent the initial movement of the paper under a certain condition and the force that is applied perpendicularly to the paper. It is carried out between the coated surfaces by a method according to the JIS-P8147 (1994) horizontal method. Then, the average value of 5 times was rounded to 2 digits after the decimal point (testing machine: “friction resistance measuring device” manufactured by Toyo Seiki Co., Ltd.).

As shown in the quality evaluation column of Table 1, it was found that the processed papers of Examples 1 to 29 according to the present invention were superior to the processed papers of Comparative Examples 1 to 3 in terms of quality. When the average average particle diameter of the thermally foamed particles is 15 to 20 μm, the foaming start temperature of the thermally foamable particles is 75 to 85 ° C., and the maximum expansion temperature is 105 to 120 ° C., the pulp of the thermally foamed particles When the blending ratio with respect to is 95.0 / 5.0 or more and 99.9 / 0.1 or less, when the blending ratio of the binder is 20/100 or more and 60/100 or less, the coating liquid for the undercoat layer is applied. When the amount is 0.4 g / m ² or more and 10 g / m ² or less, the case where the binder is SBR is excellent. Regarding the average particle diameter of the thermally foamed particles, as shown in the comparison of Examples 5 and 29 and Comparative Examples 1 and 2, if the average particle diameter is outside the range of 15 to 20 μm, the thermally foamed particles are formed on the surface of the undercoat layer. It is considered that unevenness remains due to non-uniform foaming and the like, and the friction coefficient and the sliding angle are lowered.

  As shown in the quality evaluation column of Table 2, the processed papers of Examples 30 to 34 according to the present invention are superior in quality in terms of slip angle and static friction coefficient than the processed papers of Comparative Examples 4 and 5. It has been found. The processed paper of Examples 5 and 29 to 33 having a static friction coefficient of 0.10 or more and 0.25 or less and a sliding angle of 12 degrees or more and 20 degrees or less can be used for packaging containers such as interior packaging containers. When the packaging container was used, it was confirmed that there were no inconveniences such as cracks in the ruled line, and that scratches and dirt were prevented from being attached. Among them, the processed papers of Examples 5 and 31 to 33 having a static friction coefficient of 0.14 or more and 0.2 or less and a sliding angle of 12 degrees or more and 18 degrees or less are particularly suitable for workability and scratch / stain prevention. It was confirmed to be excellent. It was confirmed that the processed papers of Comparative Examples 4 and 5 in which the slip angle and the static friction coefficient were out of the above ranges were cracked with a ruled line and had low workability, and the use of scratches and dirt was conspicuous in use.

  Even when the polymer emulsifier of the aqueous resin emulsion contained in the coating liquid for the topcoat layer is changed to a monomer component other than acrylic acid, it has excellent anti-slip properties as shown in Examples 35 to 38. Yes. In the processed paper of Comparative Example 6, since the slip resistance is lowered, it is considered that the carboxyl group in the polymer emulsifier improves the slip resistance. This is probably because when a polymer emulsifier is synthesized using a monomer having no carboxyl group, the contribution as a slip component is high when the monomer remains as an unreacted substance.

  From the above results, the processed paper according to the present invention is excellent in cushioning properties and anti-slip properties, and also has excellent surface strength, and thus can be used because conventional foamed paper has low surface strength. It was used for packaging containers such as corrugated cardboard sheets, corrugated packaging containers, and interior packaging containers with excellent cushioning and slipping properties that were used for transportation, storage, and protection, and I actually tried using them to make packaging containers However, it was confirmed that no inconvenience such as ruled line cracking occurred at all.

Claims (5)

In a processed paper comprising a base paper and a coating layer provided on at least one side of the base paper,
The coating layer comprises an undercoat layer provided on the surface of the base paper and at least one overcoat layer provided on the surface of the undercoat layer,
This undercoat layer is formed by applying an undercoat layer coating solution containing thermally foamable particles, pulp and binder,
This topcoat layer is formed by applying a topcoat layer coating solution containing an aqueous resin emulsion,
The aqueous resin emulsion contains a polymer emulsifier having a carboxyl group in the molecule,
The average particle diameter of the thermally foamable particles contained in the undercoat layer coating solution is 15 μm or more and 20 μm or less,
A processed paper, wherein a slip angle measured according to JIS-P8147 (1994) on the surface of the coating layer is 12 degrees or more and 20 degrees or less. Compounding ratio thermally expandable particles of the pulp contained in the coating liquid for the undercoat layer (dry weight ratio), according to claim 1 is 0.1 / 99.9 to 5.0 / 95.0 or less Processed paper. The processed paper of Claim 1 or Claim 2 in which the binder contained in the said coating liquid for undercoat layers contains a styrene butadiene copolymer (SBR) latex as a main component. Compounding ratio mixture of thermally expandable particles and pulp of the binder contained in the coating liquid for the undercoat layer (dry weight ratio), according to claim 1 is 20/100 or 60/100 or less, claim 2 or claim Item 4. The processed paper according to item 3 . 5. The coating amount of the undercoat layer coating solution is 0.4 g / m ² or more and 10 g / m ² or less in terms of solid content per one side of the base paper. 5. Processed paper.