JP2005290590A - Forming paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forming paper consisting of stretchable paper excellent in printing aptitude. <P>SOLUTION: This forming paper consists of the stretchable paper containing ≥0.2 and ≤1.0 wt. % softening agent based on the absolute dry weight of pulp, and also contains ≥0.5 and ≤1.0 wt. % polyacrylamide resin and/or cationized starch as a paper strength-improving agent based on the absolute dry weight of the pulp. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a molding paper that can be three-dimensionally molded by a method such as embossing, press molding, pressure molding, vacuum molding, or the like, and has excellent printability.

  2. Description of the Related Art Conventionally, stretched paper having stretch properties has been used as a molded paper for containers such as food packaging materials and drinking water. This stretched paper is stretched by shrinking the paper by a method such as creping or kulpacking. Also, in recent years, as a method for producing stretched paper having higher stretch properties, a corrugated pre-form is applied, and a hard roll that has ribs on the surface and rotates at a high speed, and a slow and smooth surface. A technique has been proposed in which paper is condensed between a pair of rolls composed of soft rolls that rotate at a speed to impart stretch characteristics simultaneously in the vertical and horizontal directions (Patent Document 1).

In recent years, many such stretched papers have been used as molded papers for paper molded products, and it has been required to print the molded products for design and other purposes. However, as for the forming paper using stretched paper, it has been considered to have strength and water resistance for maintaining the shape of the molded product, but as described above, the shrinkage treatment performed in the production of stretched paper. As a result, wrinkles and grooves are formed on the surface, so that the surface of the paper is uneven, and printing on such base paper is not considered at all, and is not suitable for printing.
Japanese National Patent Publication No. 11-509276

  As a method of imparting printability to such stretched paper, there is a method of treating the stretched paper with a calendar to reduce the surface irregularities, but the problem is that the rigidity of the paper is greatly reduced and the properties as a molded paper are lowered. was there.

  An object of the present invention is to provide a molded paper made of stretched paper having excellent printability.

  In order to achieve the above object, the molded paper according to claim 1 contains a softening agent in an amount of 0.2% by weight or more and 1.0% by weight or less per dry dry weight of pulp, and polyacrylamide as a paper strength improver. It is characterized by comprising stretched paper containing 0.5% by weight or more and 1.0% by weight or less of resin and / or cationized starch with respect to the dry weight of pulp.

  According to a second aspect of the present invention, the stretched paper according to the first aspect of the present invention is such that the stretched paper has a smoothness by microtopography of less than 25 μm when pressurized to 3 MPa, and a difference from that when pressurized by 1 MPa is 40 μm. It is the above.

The molded paper according to claim 3 is characterized in that the stretched paper according to claim 1 or 2 has a bump water absorption of less than 50 g / m ² · 2 minutes.

  According to a fourth aspect of the present invention, the stretched paper according to the first, second, or third aspect has a tensile breaking elongation defined by JIS P 8113 of 10% or more in both the vertical direction and the horizontal direction. It is characterized by being.

  As described above, according to the molded paper according to the present invention, the softening agent is contained in an amount of 0.2% by weight or more and 1.0% by weight or less per dry dry weight of the pulp, so that the cushioning property at the time of printing is improved and the paper strength is improved. Strength and water resistance can be maintained by containing polyacrylamide resin and / or cationized starch in the range of 0.5% to 1.0% by weight per dry dry weight of pulp as an agent. Even with stretched paper, the cushioning property of the paper is improved by the softening agent, the unevenness is easily smoothed by the printing pressure at the time of printing, the paper layer structure is advantageous for ink deposition, and the printability is excellent. In addition, the strength and water resistance of the molded paper can be maintained.

  If the stretched paper has a smoothness by microtopography of less than 25 μm when pressed at 3 MPa, the ink deposit can be sufficiently covered by the printing pressure, and if the difference from when pressed at 1 MPa is 40 μm or more, The cushioning property is high, and the unevenness on the paper surface is easily smoothed by the pressure during printing, and the printability is further improved.

Further, when the stretch paper has a bump water absorption of less than 50 g / m ² · 2 minutes, water resistance is further improved.

  Further, when the stretched paper has a tensile elongation at break specified in JIS P 8113 of 10% or more in both the longitudinal direction and the transverse direction, it can also cope with deep drawing molding that requires large elongation. .

  The best mode for carrying out the molded paper according to the present invention will be described below.

  The molded paper according to the present invention contains a softening agent in the range of 0.2% by weight or more and 1.0% by weight or less per the absolute dry weight of pulp, and is a paper strength improver selected from polyacrylamide or cationized starch. In a range of 0.5 wt% to 1.0 wt% per absolute dry weight of pulp.

  The stretched paper preferably has a smoothness of less than 25 μm when pressed by 3 MPa in the microtopograph method, and further has a difference in smoothness of 40 μm or more when pressed by 1 MPa. When the smoothness value under pressure by this microtopograph method is large, the unevenness on the paper surface is difficult to be smoothed by the pressure at the time of printing, and when the smoothness at the time of 3 MPa pressure is 25 μm or more, the printing pressure is reduced. The ink inking property is remarkably inferior, and if the difference in smoothness between 1 MPa press and 3 MPa press is large, it indicates that the cushioning property of the paper is high, and if the difference is 40 μm or more, printing is performed. This is because ink deposition can be sufficiently covered by pressure.

  The stretched paper is preferably smoothed with a machine calender, soft nip calender, or the like in a normal paper making process in order to obtain a desired smoothness range.

The stretched paper preferably has a bump water absorption of 50 g / m ² · 2 minutes or less. If the water absorption is less than 50 g / m ² · 2 minutes, the water resistance is improved, and the use of the molded paper according to the present invention is exposed to condensed water and rain water such as frozen refrigerated food packaging materials, paper containers, and three-dimensional posters. However, the shape change after molding can be prevented.

  The molded paper according to the present invention is not particularly limited with respect to the raw material pulp, but is a paper having a composition of 100% natural pulp due to waste disposal and environmental load problems against the background of global environmental problems. Is preferred. As the natural pulp, normal paper raw materials such as coniferous or hardwood wood fibers, bast fibers such as cocoons and cocoons, non-wood fibers such as bagasse and kenaf, and cotton fibers can be used. From these papermaking raw materials, chemical pulp (craft pulp, sulfite pulp, etc.) or mechanical pulp (crushed wood pulp, thermomechanical pulp, chemithermomechanical pulp, etc.) is produced and used. Also, deinked pulp made from waste paper may be used.

  These pulps are used singly or in combination, but from the viewpoint of versatility, it is preferable to use bleached kraft pulp of conifers or hardwoods with a Canadian standard freeness (CSF) of about 200 to 400 ml. . Furthermore, in order to provide the characteristics as the desired molded paper, paper making chemicals such as a softening agent, a sizing agent, and a paper strength improver described later are added to make paper.

  The molded paper according to the present invention is composed of the stretched paper as described above. This stretched paper is stretched paper that has been stretched by kulpack processing, crepe processing, or the like. In particular, as disclosed in JP-A-11-509276, a hard roll made of a hard substance and having ribs on its surface in the circumferential direction and rotating at a higher speed than the other, and a soft roll made of a soft substance. The stretched paper is preferably a stretched paper which has a smooth surface and is imparted with a high elongation property by shrinking the wet paper between a pair of soft rolls that rotate at a slower speed than the other.

Moreover, as an elongation characteristic, it is preferable that the tensile breaking elongation prescribed | regulated to JISP8113 is 10% or more of both the vertical direction and a horizontal direction. The basis weight is preferably in the range of 100 g / m ^{2 to} 450 g / m ² .

  The said softening agent used by this invention has the effect | action which inhibits the fiber interfiber coupling | bonding of a pulp, or softens fiber itself. For example, there are surfactants having a hydrophobic group and a hydrophilic group having this action, such as oil-based nonionic surfactants, sugar alcohol-based nonionic surfactants, polyhydric alcohol-type nonionic surfactants. Higher alcohol, polyhydric alcohol and fatty acid ester compound, higher alcohol or higher fatty acid polyoxyalkylene adduct, polyhydric alcohol and fatty acid ester compound polyoxyalkylene adduct, higher fatty acid ester polyoxyalkylene adduct, Fatty acid polyamidoamines and the like can be exemplified, but the compounds and combinations are not limited as long as the cushioning property of paper can be improved.

  In consideration of pulp blending and other internal chemicals, the softener is usually added to the paper stock in the range of 0.1 wt% to 5.0 wt% per pulp dry weight. Although it is good, if the amount of addition increases, the strain and size will decrease. In the use of the molded paper of the present invention, it is necessary to add a softening agent so as to be contained in the range of 0.2 wt% or more and 1.0 wt% or less per the absolute dry weight of pulp.

  The paper strength improver used in the present invention is a polyacrylamide resin and / or cationized starch. Since the paper strength improver increases the Young's modulus of the paper and impairs cushioning properties, the molding paper of the present invention contains 0.5% by weight or more and 1.0% by weight or less per the absolute dry weight of pulp. It is essential.

  Further, the molding paper of the present invention comprises: a rosin sizing agent; a neutral rosin sizing agent; an alkyl ketene dimer (AKD); an alkenyl succinic anhydride (ASA); an internal sizing agent such as a petroleum sizing agent; a polyamide polyamine. Epichlorohydrin-based resin; urea / formalin-based resin; wet paper strength improver such as melamine / formalin-based resin, aluminum sulfate (sulfuric acid band) and the like are added as necessary.

  In addition, a surface treatment agent containing a water-soluble polymer as a main component may be applied for the purpose of improving the surface strength and size properties within a range that does not affect the elongation characteristics. As the water-soluble polymer, those usually used as surface treating agents such as oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol and the like can be used alone or a mixture thereof. In addition to the water-soluble polymer, a paper strength enhancer for the purpose of water resistance and surface strength improvement and an external sizing agent for the purpose of imparting size can be added to the surface treatment agent. As the external sizing agent, styrene / acrylic acid copolymers, styrene / maleic acid copolymers, olefin copolymers, and the like can be used. The surface treatment agent can be applied by a coating machine such as a two-roll size press coater, a gate roll coater, a blade metering coater, or a rod metering coater.

  In order to produce the molded paper of the present invention, as a paper machine, a long paper machine, a twin wire type paper machine such as an on-top former type, a hybrid former type or a gap former type, or a round net multi-cylinder paper machine is known. A public one is used. In order to impart high elongation characteristics, a shrinkage imparting device as disclosed in the above-mentioned Japanese National Patent Publication No. 11-509276 may be installed on a paper machine.

  The molded paper of the present invention may be subjected to a machine calendar process for finishing, but in consideration of adverse effects such as a decrease in paper stiffness due to a decrease in thickness, a linear pressure of 50 kN / m or less is preferable.

  Further, the printability of the stretched paper that is the molded paper of the present invention can be improved by devising printing conditions such as increasing the printing pressure, using a blanket with good cushioning properties, and lowering the ink viscosity. be able to.

  Even if the molded paper of the present invention is stretched paper with irregularities formed on the surface by applying shrinkage, the softening agent improves the cushioning properties of the paper, and the irregularities are easily smoothed by the printing pressure during printing. The paper layer structure is advantageous in terms of meat properties, has excellent printability, and can maintain strength and water resistance as a molded paper.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by these. In the examples, “%” represents “% by weight” unless otherwise specified, and the amount added represents the solid content of pulp.

[Example 1]
The pulp which beaten conifer bleach bleached kraft pulp (NBKP) to CSF 350ml was used for the raw material pulp. To this raw pulp slurry, 0.4% of synthetic rosin sizing agent (trade name: NSP-S, manufactured by Seiko PMC Co., Ltd.) is used as a sizing agent, and polyamide / polyamine epichlorohydrin resin (trade name: WS570) as a wet paper strength agent. 0.2% of Seiko PMC Co., Ltd., 0.5% of polyacrylamide resin (trade name: Polyaclon PD364R, Seiko PMC Co., Ltd.) as a paper strength improver, and softener (trade name) : Size Pine DL-15, manufactured by Arakawa Chemical Co., Ltd.) 0.2%, and pulp slurry adjusted to pH 4.5 with a sulfuric acid band was subjected to paper making with a Ford Liner long net paper machine. After adjusting the wet paper to a moisture content of 35% in the paper, the sheet was subjected to shrinkage treatment by a nip between a pair of grooved metal rolls and rubber rolls with different speeds.

The grooved metal roll has a structure in which a screw having a pitch of 1.25 mm and a depth of 0.8 mm is cut on a circumference of a diameter of 500 mm. The rubber roll has a structure in which a nitrile butadiene rubber having a JIS hardness of A50 is wound around an iron core having a diameter of 500 mm with a thickness of 30 mm. The nip linear pressure during the shrinkage treatment is 60 kN / m. The speed difference is 25% slower for rubber rolls than for metal rolls. The paper web obtained by this treatment was dried with a multi-cylinder dryer and treated with a machine calendar at a linear pressure of 30 kN / m to obtain a molded paper having a basis weight of 250 g / m ² .

  The obtained molded paper was evaluated for tensile strength, elongation at break, water resistance, cushioning property, printability, and strain by the following methods, and are shown in Table 1.

<Tensile strength and tensile elongation at break> Measured according to JIS P8113.

<Water resistance> Based on JIS P 8140, it evaluated in the water absorption test of the bump method.

<Cushion Property> Using a microtopograph (manufactured by Toyo Seiki Seisakusho Co., Ltd.), the cushion property was evaluated by measuring the smoothness (expressed in roughness μm) at a pressure of 3 MPa and a pressure of 1 MPa. Evaluation of cushioning property evaluated that the smoothness at the time of 3MPa pressurization was high, and the cushioning property was good, so that the smoothness improvement width from the time of 1MPa pressurization was large.

<Printing evaluation> Four-color printing was performed with a sheet-fed offset printing machine (Man Roland R304), and the ink inking property was visually evaluated.

<Paper stiffness> The stiffness in the longitudinal direction and the transverse direction was measured by the Taber stiffness tester method defined in JIS P 8125, and evaluated with the geometric mean value.

[Example 2]
Containing softwood bleached kraft pulp (NBKP) and hardwood bleached kraft pulp (LBKP) in the raw material pulp in 70/30, and using pulp that has been beaten to CSF 300 ml as raw material slurry, softener (trade name: PT205, manufactured by Seiko PMC Co., Ltd.) ) Was added in 0.5%, and cationized starch (trade name: Neotac # 30T, manufactured by Nippon Shokuhin Kako Co., Ltd.) was added to the paper strength improver in the same manner as in Example 1 except that 0.5% was added. To obtain a molded paper. Table 1 shows the evaluation of the obtained molded paper.

[Example 3]
Containing 50/50 softwood bleached kraft pulp (NBKP) and hardwood bleached kraft pulp (LBKP) in the raw material pulp, and using a pulp that has been beaten to CSF 250 ml as a raw material slurry, a softener (trade name: KB-115, Kao Corporation) Example 1 except that 1.0% was added and cationized starch (trade name: CATO-302, manufactured by Nippon NSC Co., Ltd.) was added to 1.0% as a paper strength improver. A molded paper was obtained. Table 1 shows the evaluation of the obtained molded paper.

[Comparative Example 1]
The pulp which mix | blended softwood bleached kraft pulp (NBKP) and hardwood bleached kraft pulp (LBKP) in the raw material pulp to 70/30, and beaten to CSF 250ml was used. Synthetic rosin sizing agent (trade name: NSP-S, manufactured by Seiko PMC Co., Ltd.) as a sizing agent, 0.4%, and polyamide / polyamine epichlorohydrin resin (trade name: as a wet paper strength improver) 0.2% WS570, manufactured by Seiko PMC Co., Ltd., and 0.5% polyacrylamide resin (trade name: Polystron 117, manufactured by Arakawa Chemical Co., Ltd.) as a paper strength improver are added to the sulfate band. A predetermined molding paper was obtained by the same method as in the example except that the paper stock adjusted to pH 4.5 was used. Table 1 shows the evaluation of the obtained molded paper.

[Comparative Example 2]
Containing 50/50 softwood bleached kraft pulp (NBKP) and hardwood bleached kraft pulp (LBKP) in the raw material pulp, and using a pulp that has been beaten to CSF 250 ml as a raw material slurry, a softener (trade name: KB-115, Kao Corporation) Product) was added 1.5%, and cationized starch (trade name: Neotac 30T, manufactured by Nippon Shokuhin Kako Co., Ltd.) was changed to 1.0% addition as a paper strength improver. A molded paper was obtained. Table 1 shows the evaluation of the obtained molded paper.

  As shown in Table 1, the stretched papers of Examples 1 to 3 containing a softening agent in the range of 0.2 to 1.0% by weight were compared with Comparative Example 1 containing no softening agent. As can be seen from the results of smoothness due to the above, the cushioning property is good and the smoothness under pressure is good, so that the printability was excellent. As can be seen from the Cobb water absorption of Comparative Example 2, the reduction in size due to the inclusion of the softening agent can ensure the predetermined water resistance within the range of the examples. In addition, by using a paper strength improver in combination, it was possible to compensate for the stiffness, and a molded paper with good printability was obtained.

Claims (4)

  A softener is contained in an amount of 0.2% by weight or more and 1.0% by weight or less based on the dry weight of pulp and 0.5% by weight of polyacrylamide resin and / or cationized starch as a paper strength improver per dry weight of pulp. %, 1.0% by weight or less of stretched paper.   2. The forming paper according to claim 1, wherein the smoothness measured by microtopography is less than 25 [mu] m when pressed at 3 MPa, and the difference from when pressed at 1 MPa is 40 [mu] m or more. The molded paper according to claim 1 or 2, wherein the water absorption of the bumps is less than 50 g / m ² · 2 minutes.   The molded paper according to claim 1, 2 or 3, wherein the tensile breaking elongation defined in JIS P 8113 is 10% or more in both the longitudinal direction and the transverse direction.