JP2023154528A - Sheet for printing and manufacturing method thereof - Google Patents

Abstract

An object of the present invention is to provide a printing sheet with excellent strength and printability.
The present invention provides a printing sheet including a base material and a coating layer provided on one or both sides of the base material, wherein the base material contains a polyolefin resin and an inorganic powder. Provided is a printing sheet, wherein the coating layer contains a predetermined amount of clay, heavy calcium carbonate, styrene-butadiene copolymer, and cationic polyamide resin at a mass ratio of 50:50 to 10:90. do.
[Selection diagram] None

Description

The present invention relates to a printing sheet and a method for manufacturing the same.

In recent years, synthetic paper and the like whose base material surface has been modified depending on the purpose have been widely used as printing sheets (for example, Patent Documents 1 and 2).

As shown in Patent Document 1, the present inventor provided a coat layer containing an acrylic polymer, clay, and heavy calcium carbonate on the surface of the base material constituting the printing sheet, thereby improving the adhesion between the layers. It has been found that printability (quick drying of ink, etc.) can be improved.

Patent No. 7031917 Japanese Patent Application Publication No. 2008-223174

However, there is a further need to improve properties in printing sheets.

Further, the present inventors have found that in the conventional technology, there may be a problem in achieving both the strength (especially adhesive strength) of the coating layer provided on the surface of the base material and the printability.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a printing sheet with excellent strength and printability.

The present inventors have discovered that the above problem can be solved by incorporating predetermined amounts of styrene-butadiene copolymer and cationic polyamide resin in addition to clay and heavy calcium carbonate into the coating layer. This discovery led to the completion of the present invention. More specifically, the invention provides:

(1) A printing sheet comprising a base material and a coating layer provided on one or both sides of the base material,
The base material contains a polyolefin resin and an inorganic substance powder in a mass ratio of 50:50 to 10:90,
The coating layer contains clay, heavy calcium carbonate, styrene-butadiene copolymer, and cationic polyamide resin,
The content of the clay is 43% by mass or more and 63% by mass or less with respect to the coat layer,
The content of the heavy calcium carbonate is 24% by mass or more and 34% by mass or less with respect to the coat layer,
The content of the styrene-butadiene copolymer is 10% by mass or more and 20% by mass or less with respect to the coat layer,
The content of the cationic polyamide resin is 0.3% by mass or more and 0.7% by mass or less with respect to the coat layer,
The degree of cationization of the cationic polyamide resin is 2.00 meq/g or more and 4.00 meq/g or less,
Printing sheet.

(2) The printing sheet according to (1), wherein the polyolefin resin is a polypropylene resin.

(3) The printing sheet according to (1) or (2), wherein the clay has a volume average particle diameter of 0.05 μm or more and 2.00 μm or less.

(4) The printing sheet according to any one of (1) to (3), wherein the heavy calcium carbonate has a volume average particle diameter of 0.05 μm or more and 2.00 μm or less.

(5) The printing sheet according to any one of (1) to (4), wherein the printing sheet is an offset printing sheet.

(6) A method for producing a printing sheet including a coating layer forming step of providing a coating layer on one or both sides of a base material,
The base material contains a polyolefin resin and an inorganic substance powder in a mass ratio of 50:50 to 10:90,
The coating layer contains clay, heavy calcium carbonate, styrene-butadiene copolymer, and cationic polyamide resin,
The content of the clay is 43% by mass or more and 63% by mass or less with respect to the coat layer,
The content of the heavy calcium carbonate is 24% by mass or more and 34% by mass or less with respect to the coat layer,
The content of the styrene-butadiene copolymer is 10% by mass or more and 20% by mass or less with respect to the coat layer,
The content of the cationic polyamide resin is 0.3% by mass or more and 0.7% by mass or less with respect to the coat layer,
The degree of cationization of the cationic polyamide resin is 2.00 meq/g or more and 4.00 meq/g or less,
Production method.

(7) Before the coat layer forming step,
a molding step of extruding the base material into a sheet shape;
After the forming step, a stretching step of stretching the base material;
The manufacturing method according to (6), comprising:

According to the present invention, a printing sheet with excellent strength and printability is provided.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

<Printing sheet>
The printing sheet of the present invention includes a base material and a coating layer provided on one or both sides of the base material, and satisfies all of the following requirements.
- The base material contains a polyolefin resin and an inorganic substance powder in a mass ratio of 50:50 to 10:90.
- The coating layer contains clay, heavy calcium carbonate, styrene-butadiene copolymer, and cationic polyamide resin.
- The content of clay is 43% by mass or more and 63% by mass or less with respect to the coat layer.
- The content of heavy calcium carbonate is 24% by mass or more and 34% by mass or less with respect to the coat layer.
- The content of the styrene-butadiene copolymer is 10% by mass or more and 20% by mass or less based on the coating layer.
- The content of the cationic polyamide resin is 0.3% by mass or more and 0.7% by mass or less with respect to the coat layer.
- The degree of cationization of the cationic polyamide resin is 2.00 meq/g or more and 4.00 meq/g or less.

As a result of extensive studies, the present inventor has found that by blending a styrene-butadiene copolymer and a cationic polyamide resin in the coating layer of a printing sheet in a manner that satisfies the requirements of the present invention, It has been found that both strength and printability can be further improved without impairing the advantages of the sheet (for example, the printing sheet described in Japanese Patent No. 7031917).

Although it is not clear why the combination of styrene-butadiene copolymer and cationic polyamide resin can improve strength and printability, these components improve the compatibility of the resin and other components in the coating layer. It is assumed that this is due to the following.

In the present invention, the term "printing sheet" includes a sheet for printing by any method.
Printing sheets in a preferred embodiment of the present invention include offset printing sheets and laser printer printing sheets.

In the present invention, the "strength of the printing sheet" includes the adhesive strength between the base material and the coating layer in the printing sheet.
According to the present invention, high adhesive strength between the base material and the coating layer in the printing sheet can be achieved.

The strength of the printing sheet can be evaluated by the method shown in the Examples.

In the present invention, "printability of a printing sheet" includes fixing properties and transfer properties of printing (particularly offset printing and laser printer printing).

The printability of the printing sheet can be evaluated by the peel test shown in the Examples.

Hereinafter, the structure of the printing sheet of the present invention will be explained in detail.

(1) Substrate The structure of the substrate of the printing sheet of the present invention is other than that it contains polyolefin resin and inorganic substance powder in a mass ratio (polyolefin resin: inorganic substance powder) of 50:50 to 10:90. There is no particular limitation, and any configuration conventionally known in the paper manufacturing field can be adopted.

In the base material, the mass ratio of polyolefin resin to inorganic powder (polyolefin resin: inorganic powder) is preferably 40:60 to 20:80, more preferably 40:60 to 25:75.
If the structure of the base material satisfies the above requirements, it will have better impact resistance and moldability.

From the viewpoint that the effects of the present invention can be more easily exhibited, the lower limit of the content of the polyolefin resin is preferably 15% by mass or more, more preferably 20% by mass or more, based on the base material.

From the viewpoint that the effects of the present invention can be more easily exhibited, the upper limit of the content of the polyolefin resin is preferably 45% by mass or less, more preferably 40% by mass or less based on the base material.

From the viewpoint that the effects of the present invention can be more easily achieved, the lower limit of the content of the inorganic substance powder is preferably 55% by mass or more, more preferably 60% by mass or more based on the base material.

From the viewpoint that the effects of the present invention can be more easily achieved, the upper limit of the content of the inorganic substance powder is preferably 85% by mass or less, more preferably 80% by mass or less based on the base material.

The constituent components of the base material will be explained in detail below.

(Polyolefin resin)
The polyolefin resin constituting the base material is not particularly limited, and any resin that can be used in the paper manufacturing field can be employed. The polyolefin resins can be used singly or in combination of two or more.

In the present invention, the term "polyolefin resin" refers to a polyolefin resin whose main component is an olefin component unit.
"Mainly composed of olefin component units" means that the olefin component units are present in the polyolefin resin in an amount of 50% by mass or more (preferably 75% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more). It means to be included.
The method for producing the polyolefin resin used in the present invention is not particularly limited, and any method using a Ziegler-Natta catalyst, a metallocene catalyst, a radical initiator (oxygen, peroxide, etc.), etc. may be used. .

From the viewpoint of the balance between mechanical strength and heat resistance, the base material preferably contains polypropylene resin and/or polyethylene resin among polyolefin resins; Most preferably, only polypropylene resin is contained as the resin component.

Examples of the polypropylene resin include resins containing 50% by mass or more of propylene component units.

Examples of the polypropylene resin include propylene homopolymers, copolymers of propylene and other α-olefins (those copolymerizable with propylene), and the like.
Examples of "other α-olefins" include α-olefins having 4 to 10 carbon atoms (ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4- dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene, etc.).
Among the above polypropylene resins, propylene homopolymers are particularly preferred.

The propylene homopolymer includes linear or branched polypropylene exhibiting various stereoregularities (isotactic, syndiotactic, atactic, hemiisotactic, etc.).

The propylene copolymer may be a random copolymer, a block copolymer, a binary copolymer, a tertiary copolymer, or the like. Specific examples include ethylene-propylene random copolymer, butene-1-propylene random copolymer, ethylene-butene-1-propylene random terpolymer, ethylene-propylene block copolymer, and the like.

Examples of the polyethylene resin include resins containing 50% by mass or more of ethylene component units.

Examples of polyethylene resins include high-density polyethylene (HDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), linear low-density polyethylene (LLDPE), ethylene-vinyl acetate copolymer, and ethylene-propylene copolymer. Copolymer, ethylene-propylene-butene 1 copolymer, ethylene-butene 1 copolymer, ethylene-hexene 1 copolymer, ethylene-4 methylpentene 1 copolymer, ethylene-octene 1 copolymer, and the like.

(Inorganic substance powder)
The inorganic substance powder constituting the base material is not particularly limited, and any resin that can be used in the paper manufacturing field can be employed. The inorganic substance powder can be used alone or in combination of two or more types.

The inorganic powder may be synthetic or derived from natural minerals.

Inorganic substance powders include carbonates, sulfates, silicates, phosphates, borates, oxides of metals (calcium, magnesium, aluminum, titanium, iron, zinc, etc.), or powders of hydrates thereof. can be mentioned.
More specifically, calcium carbonate, magnesium carbonate, zinc oxide, titanium oxide, silica, alumina, clay, talc, kaolin, aluminum hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, calcium silicate, aluminum sulfate, magnesium sulfate. , calcium sulfate, magnesium phosphate, barium sulfate, silica sand, carbon black, zeolite, molybdenum, diatomaceous earth, sericite, whitebait, calcium sulfite, sodium sulfate, potassium titanate, bentonite, graphite, and the like.
Among these, calcium carbonate powder is preferred.

The calcium carbonate may be either heavy calcium carbonate or light calcium carbonate. From the viewpoint of easily achieving good adhesive strength with the coating layer, the base material preferably contains heavy calcium carbonate, and the inorganic powder contained in the base material is preferably composed of heavy calcium carbonate. More preferred.

Note that "heavy calcium carbonate" is calcium carbonate obtained by mechanically pulverizing (dry method, wet method, etc.) a natural raw material (limestone, etc.) containing CaCO ₃ as a main component.
"Light calcium carbonate" is calcium carbonate prepared by a synthetic method (chemical precipitation reaction, etc.).
Therefore, heavy calcium carbonate and light calcium carbonate are clearly distinguished from each other.

The shape of the inorganic substance powder is not particularly limited, and may be any of particles, flakes, granules, fibers, etc. Further, these shapes may be uniform shapes obtained by a synthetic method or the like, or irregular shapes obtained by grinding natural minerals or the like.

The inorganic substance powder is preferably in the form of particles or fibers.

When the inorganic substance powder is in the form of particles, the average particle diameter thereof is preferably 0.01 μm or more and 50.0 μm or less, more preferably 1.0 μm or more and 10.0 μm or less, and even more preferably 1.0 μm or more and 5.0 μm or less. It is. In particular, it is preferable that the particle size distribution does not contain particles with a particle size exceeding 50.0 μm.
When the requirements for the average particle diameter meet the above requirements, it is easy to suppress the increase in viscosity during kneading with the polyolefin resin, and the moldability is likely to be good.

In the present invention, the "average particle diameter" means a value calculated from the results of measuring the specific surface area by an air permeation method according to JIS M-8511. As the measuring device, for example, a specific surface area measuring device model SS-100 manufactured by Shimadzu Corporation can be preferably used.

When the inorganic substance powder is fibrous, the average fiber length thereof is preferably 3.0 μm or more and 20.0 μm or less, more preferably 0.2 μm or more and 1.5 μm or less.
When the inorganic substance powder is fibrous, the aspect ratio is usually 10 or more and 30 or less.

In the present invention, "average fiber length" and "average fiber diameter" mean values measured using an electron microscope.
In the present invention, "aspect ratio" means the ratio of average fiber length to average fiber diameter (average fiber length/average fiber diameter).

The surface of the inorganic substance powder may be previously subjected to surface treatment in order to improve its dispersibility and reactivity. Examples of surface treatment methods include physical methods (such as plasma treatment) and chemical methods (methods using coupling agents and surfactants).
Examples of the coupling agent include a silane coupling agent and a titanium coupling agent. The surfactant may be anionic, cationic, nonionic, or amphoteric, and includes, for example, higher fatty acids, higher fatty acid esters, higher fatty acid amides, higher fatty acid salts, and the like.

(Other additives in base material)
In addition to the above-mentioned components, other additives may or may not be blended in the base material, if necessary. Other additives include, for example, pigments, lubricants, plasticizers, coupling agents, fluidity improvers, dispersants, antioxidants, ultraviolet absorbers, flame retardants, stabilizers, antistatic agents, blowing agents, etc. Can be mentioned.
These additives can be used alone or in combination of two or more.
The type and content of these additives can be appropriately set depending on the desired effect.

(Other configurations of base material)
Various other configurations of the base material are not particularly limited.

The base material may have a single layer or multiple layers.

When the base material is multilayered, layers can be provided for any purpose. For example, a sealant layer for improving the adhesion between the base material and the coat layer, a protective layer, a shielding layer, an adhesive layer, etc. may be provided on the surface of the base material on which the coat layer is not provided.
However, when the base material is multilayered, at least one layer among the layers must satisfy the requirements for the base material according to the present invention, and preferably all the layers satisfy the requirements for the base material according to the present invention.

The base material may be a stretched sheet or an unstretched sheet.
In the case of a stretched sheet, it may be stretched in a uniaxial direction or a biaxial direction, such as vertically or horizontally.

The size of the base material is not particularly limited, and may be an appropriate size as a printing sheet depending on the intended use of the printed material.

The thickness of the base material is not particularly limited, and is usually 10 μm or more and 300 μm or less, preferably 25 μm or more and 200 μm or less.

The base material may be surface-treated on one or both sides, if necessary. The surface treatment may be applied to the entire or part of the surface of the base material.
Preferred surface treatments include treatment by an oxidation method, treatment by a roughening method, primer treatment, etc. from the viewpoint of improving the adhesion with the coating layer provided on the surface of the base material.
Examples of the oxidation method include corona discharge treatment, flame treatment, plasma treatment, glow discharge treatment, chromic acid treatment (wet type), flame treatment, hot air treatment, ozone/ultraviolet irradiation treatment, and the like.
Examples of the roughening method include a sandblasting method and a solvent treatment method.

(2) Coat layer The coat layer is provided on one or both sides of the base material.
The coating layer may be provided on the entire surface of the base material, or may be provided on a part of the surface. However, from the viewpoint of easily achieving the effects of the present invention, it is preferable that the coating layer be provided on the entire surface of the base material.

The coating layer of the printing sheet of the present invention may be the surface to be printed (printing surface).

The present inventor has discovered that the presence of clay and heavy calcium carbonate in the continuous phase made of acrylic polymer in the coating layer improves adhesion and adhesion with the base material, improves weather resistance, and lowers the surface area. It has been found that improvements in resistivity (ease of printing), whiteness, quick drying, etc. can be achieved (Japanese Patent No. 7031917).
In addition, the present inventor believes that this effect is due to the effect of improving adhesion (anchor effect) at the bonding interface between the base material and the coating layer, which is caused by the fine irregularities formed by clay and heavy calcium carbonate. It was found that this was a contributing factor (the same publication).

However, the above technology has room for improvement in achieving both the strength of the coat layer (particularly adhesive strength) and printability (particularly offset printing suitability).
Therefore, as a result of further study by the present inventor, in addition to clay and heavy calcium carbonate, styrene-butadiene copolymer and cationic polyamide resin are blended into the coating layer in a predetermined ratio. It has been found that by doing so, it is possible to achieve both the strength of the coat layer and printability.
It has also been found that such a coat layer does not easily impair the adhesion improvement effect (anchor effect) at the bonding interface between the base material and the coat layer.

In addition, in the present invention, the acrylic polymers described in Japanese Patent No. 7031917 (for example, (meth)acrylic acid, (meth)acrylic acid ester, (meth)acrylamide, and (meth)acrylonitrile are added to the coating layer. A mode in which a polymer obtained as a main monomer component) is blended is not excluded.
However, in the present invention, it is preferable that the coating layer does not contain an acrylic polymer.

The constituent components of the coating layer will be explained in detail below. Note that the numerical values for the composition of the coating layer mean dry mass unless otherwise specified.

(Clay)
The clay content is 43% by mass or more and 63% by mass or less based on the coat layer.

The lower limit of the content of clay is preferably 45% by mass or more, more preferably 47% by mass or more based on the coat layer, from the viewpoint of easily improving the printability of the coat layer and also easily achieving the above-mentioned anchor effect. It is.

The upper limit of the content of clay is determined from the viewpoint of easily increasing the strength of the coat layer (especially adhesive strength), providing sufficient water resistance to the coat layer, and easily obtaining a good appearance. , preferably 61% by mass or less, more preferably 59% by mass or less.

In the present invention, "clay" includes clay minerals with a layered structure and clay minerals without a layered structure (imogolite, allophane, etc.). One kind of clay can be used alone or two or more kinds can be used in combination.

Clay minerals with a layered structure include swelling minerals (smectite, vermiculite, montmorillonite, bentonite, illite, hectorite, halloysite, saponite, beidellite, stevensite, nontronite, smectite, mica, brittle mica, sericite). sericite), illite, glauconite, hydrotalcite, etc.), non-swellable minerals (kaolinite, kaolingite, serpentine, pyrophyllite, talc, chlorite, etc.) chlorite), zeolite (zeolite, etc.).

The clay may be any of natural clay, synthetic clay, and organic clay.

The organic clay is not particularly limited, but clay (natural products, synthetic materials, etc.) that has been organically modified with an organic agent is preferable.

As the organic agent, any organic agent that can organicize clay can be used. For example, hexylammonium ion, octylammonium ion, 2-ethylhexylammonium ion, dodecylammonium ion, lauryl ammonium ion, octadecyl ammonium ion, dioctyl dimethyl ammonium ion, trioctyl ammonium ion, dioctyl dimethyl ammonium ion, trioctyl ammonium ion, Examples include octadecyldimethylammonium ion, triotadecylammonium ion, and the like.

From the viewpoint of easily achieving the effects of the present invention, the clay preferably contains kaolin clay (having a viscosity mainly composed of kaolinite), and more preferably consists of kaolin clay.

The particle size of the clay is not particularly limited, and can be appropriately set depending on the thickness of the coat layer to be formed.

The volume average particle diameter of the clay is preferably 0.05 μm from the viewpoint that the effects of the present invention are easily achieved and furthermore, the dispersibility within the coating layer, the adhesion to the base material, the printability, and the antistatic property are likely to be good. The thickness is 2.00 μm or more, more preferably 0.10 μm or more and 1.70 μm or less, even more preferably 0.20 μm or more and 1.50 μm or less, and still more preferably 1.00 μm or less.

In the present invention, the "volume average particle diameter" (MV) means the 50% diameter (D50) in the volume-based integrated fraction of particle diameter distribution measurement based on laser diffraction scattering method.

The closer the particle size of the clay is to uniformity, the more uniform the in-plane properties of the coating layer become, so it is preferable.

The shape of the clay is not particularly limited, and may be spherical, ellipsoidal, flat, irregular, or the like.
However, from the viewpoint of dispersibility in the coating layer, it is preferable that the shape is close to spherical (for example, the aspect ratio (longer axis/breadth axis) is preferably 5 or less, more preferably 3 or less, still more preferably 2 or less). .

The specific gravity of the clay is not particularly limited, but from the viewpoint of dispersibility within the coating layer, it is preferably 1.5 or more and 3.0 or less, more preferably 2.0 or more and 2.8 or less.

(Heavy calcium carbonate)
The content of heavy calcium carbonate is 24% by mass or more and 34% by mass or less with respect to the coat layer.

The lower limit of the content of heavy calcium carbonate is preferably 26% by mass or more, more preferably 28% by mass, based on the coating layer, from the viewpoint of easily improving the printability of the coating layer and also easily achieving the above-mentioned anchor effect. % by mass or more.

The upper limit of the content of heavy calcium carbonate is determined from the viewpoint that it is easy to increase the strength (especially adhesive strength) of the coat layer, and furthermore, it is easy to impart sufficient water resistance to the coat layer and obtain a good appearance. It is preferably 32% by mass or less, more preferably 30% by mass or less.

As the heavy calcium carbonate contained in the coating layer, the same ones as those explained in the above section (Inorganic substance powder) can be used.

The volume average particle diameter of heavy calcium carbonate is preferably 0.05 μm or more and 2.00 μm or less.
When the volume average particle size of heavy calcium carbonate satisfies the above range, the adhesive strength between the base material and the coating layer is easily improved compared to the case where light calcium carbonate having the same particle size is used. The reason for this is thought to be that in heavy calcium carbonate having such a volume average particle diameter, the particles are difficult to fall off and the anchoring effect due to the irregular shape of the particles can be expressed well.

The lower limit of the volume average particle diameter of heavy calcium carbonate is preferably 0.07 μm or more, from the viewpoint of sufficiently expressing the above-mentioned anchor effect and further improving the smoothness of the coating layer and the glossiness of the sheet. More preferably, it is 0.10 μm or more, and still more preferably 0.20 μm or more.

The upper limit of the volume average particle diameter of heavy calcium carbonate is preferably 1.50 μm or less, more preferably 1.00 μm or less, and still more preferably 0.0 μm or less, from the viewpoint of easily improving the adhesiveness between the base material and the coating layer. It is 50 μm or less.

The surface of the heavy calcium carbonate may be surface-treated in advance in order to improve its dispersibility and reactivity. As the surface treatment method, the same method as that explained in the above section (Inorganic substance powder) can be used.
From the viewpoint that the effects of the present invention can be easily achieved, fatty acid surface treatment is preferable as a surface treatment method.

(Styrene-butadiene copolymer)
The content of the styrene-butadiene copolymer is 10% by mass or more and 20% by mass or less based on the coat layer.

The lower limit of the content of the styrene-butadiene copolymer is preferably 12% by mass or more based on the coating layer, from the viewpoint of easily improving the printability of the coating layer and the strength (especially adhesive strength) of the coating layer. , more preferably 14% by mass or more.

The upper limit of the content of the styrene-butadiene copolymer is preferably 18% by mass or less based on the coating layer, from the viewpoint of easily improving the printability of the coating layer and the strength (especially adhesive strength) of the coating layer. , more preferably 16% by mass or less.

In the present invention, the "styrene-butadiene copolymer" is also referred to as "SBR" and is a copolymer of styrene and 1,3-butadiene. The styrene-butadiene copolymer can be used alone or in combination of two or more.

The lower limit of the styrene content in the styrene-butadiene copolymer is preferably 10% by mass or more, more preferably 15% by mass or more.

The upper limit of the styrene content in the styrene-butadiene copolymer is preferably 50% by mass or less, more preferably 45% by mass or less.

The lower limit of the glass transition temperature (Tg) of the styrene-butadiene copolymer is preferably -66°C or higher, more preferably -20°C or higher.

The upper limit of the glass transition temperature (Tg) of the styrene-butadiene copolymer is preferably 40°C or lower, more preferably 0°C or lower.

The styrene-butadiene copolymer may be modified or unmodified. Examples of modified styrene-butadiene copolymers include carboxy-modified styrene-butadiene copolymers.

(Cationic polyamide resin)
The content of the cationic polyamide resin is 0.3% by mass or more and 0.7% by mass or less based on the coat layer.

The lower limit of the content of the cationic polyamide resin is preferably 0.4% by mass with respect to the coat layer, from the viewpoint of easily improving the printability of the coat layer and the strength (especially adhesive strength) of the coat layer. The content is more preferably 0.45% by mass or more.

The upper limit of the content of the cationic polyamide resin is preferably 0.6% by mass with respect to the coat layer, from the viewpoint of easily improving the printability of the coat layer and the strength (especially adhesive strength) of the coat layer. The content is preferably 0.5% by mass or less.

In the present invention, "cationic polyamide resin" means a cationic copolymer having an amide bond in the main chain, and more specifically, a cationic polyamide resin having a cationic degree of 2.00 meq/g or more. It means a polyamide resin with a content of 4.00 meq/g or less.
The cationic polyamide resins can be used alone or in combination of two or more.

In the present invention, "degree of cationization" means the content of cationic groups in the molecule (unit: meq/g). The degree of cationization is determined by colloid titration.

The lower limit of the degree of cationization of the cationic polyamide resin is preferably 2.20 meq/g or more, more preferably 2.40 meq/g or more, from the viewpoint of easily achieving the effects of the present invention.

The upper limit of the degree of cationization of the cationic polyamide resin is preferably 3.80 meq/g or less, more preferably 3.60 meq/g or less, from the viewpoint of easily achieving the effects of the present invention.

Examples of the cationic polyamide resin include polyamine polyamide epichlorohydrin, cationic polyacrylamide, diallyldimethylammonium chloride amide copolymer, dicyandiamide diethylene triamine polycondensate, polyacrylamide resin, polyamide epoxy resin, and modified polyamide resin. .

The cationic polyamide resins can be used alone or in combination of two or more.

The cationic polyamide resin may be a commercially available one, such as "Violaze Resin SPI-203(50)H" (degree of cationization: 3.00 meq/g, manufactured by Taoka Chemical Industry Co., Ltd.).

The cationic polyamide resin may be modified or unmodified.

(Other additives in the coating layer)
In addition to the above-mentioned components, other additives may or may not be blended in the coating layer, if necessary. Other additives include, for example, crosslinking agents, surfactants, pH adjusters, thickeners, fluidity improvers, antifoaming agents, foam inhibitors, mold release agents, penetrants, pigments, and optical brighteners. , ultraviolet absorbers, antioxidants, preservatives, antifungal agents, waterproofing agents, ink fixing agents, curing agents, weather-resistant materials, and the like.
These additives can be used alone or in combination of two or more.
The type and content of these additives can be appropriately set depending on the desired effect.

Examples of crosslinking agents include aldehyde compounds, melamine compounds, isocyanate compounds, zirconium compounds, titanium compounds, amide compounds, aluminum compounds, boric acid, borates, carbodiimide compounds, oxazoline compounds, etc. It will be done.

From the viewpoint that the effects of the present invention are easily exerted, the coating layer substantially contains fine particles other than clay and heavy calcium carbonate (particularly fine particles having a volume average particle diameter of 0.05 μm or more and 2.00 μm or less). Preferably, it does not contain or does not contain at all. Examples of such fine particles include polymer fine particles ((meth)acrylate resin particles represented by polymethyl methacrylate particles, etc.), zinc pyrithione, zinc oxide, and the like.

(Other configurations in the coat layer)
Other configurations of the coating layer are not particularly limited.

The thickness of the coat layer (thickness in a dry state) is not particularly limited, and is usually 1 μm or more and 10 μm or less, preferably 2 μm or more and 8 μm or less, and more preferably 3 μm or more and 5 μm or less.
When the thickness of the coat layer is within the above range, the coat layer sufficiently functions as an ink-receiving layer and easily exhibits ink-receptive properties (good colorability, color development, etc.). Furthermore, the printing sheet tends to have good properties such as water resistance, surface antistatic property, and adhesion to ink.

The thickness of the coating layer (thickness in a dry state) may be, for example, 1% or more and 15% or less of the thickness of the base material.

(3) Application of printing sheet The printing sheet of the present invention can be used for printing by any printing method. Preferred printing methods include offset printing and laser printer printing.

In the present invention, "offset printing" is a printing method in which ink applied to a plate is transferred to an intermediate transfer body (such as a blanket) and then printed on a printing medium (the printing sheet of the present invention).

In the present invention, "laser printer printing" is a printing method in which a pattern formed on the surface of a photoreceptor drum using a coloring material (toner) is transferred onto a printing medium (printing sheet of the present invention).

The printing conditions for the printing sheet are not particularly limited, and any conventionally known printing machine, agent (base treatment agent, etc.), and various processes (base treatment process, printing process, drying process, etc.) can be employed.

The printing site on the printing sheet is not particularly limited, and may be, for example, a part or the entire surface of the coating layer.

<Method for manufacturing printing sheets>
The method for manufacturing the printing sheet of the present invention is not particularly limited, and any method including a step of providing a coat layer on one or both sides of the base material (coat layer forming step) can be adopted.

A preferred embodiment of the printing sheet manufacturing method of the present invention includes at least the following two steps.
(Step 1) Step of obtaining a base material by extrusion molding a resin composition containing a polyolefin resin and an inorganic substance powder in a mass ratio of 50:50 to 10:90 (Step 2) One side of the base material or A process of forming a coating layer on both sides by applying and drying a coating solution containing clay, heavy calcium carbonate, styrene-butadiene copolymer, and cationic polyamide resin.

(About process 1)
The method for forming the base material is not particularly limited, and includes a method of forming each component constituting the base material into a sheet shape using a molding machine (such as an extrusion molding machine) to obtain the base material.

The components constituting the base material may be mixed before being charged into the molding machine from the hopper, or may be mixed simultaneously with molding using the molding machine.

For melt-kneading the components constituting the base material, it is preferable to use a twin-screw kneader from the viewpoint of achieving uniform dispersibility and high shear stress.

The molding temperature in step 1 is preferably higher than the melting point of the polyolefin resin and lower than +55°C, more preferably higher than the melting point of the polyolefin resin and lower than the melting point +55°C, even more preferably polyolefin, since the higher the temperature, the more likely the odor is to be generated. The melting point of the polyolefin resin is +10°C or higher and the melting point of the polyolefin resin is +45°C or lower.

The base material may be stretched (longitudinally and/or horizontally stretched) at any time before the coating layer forming step. Stretching reduces the density of the base material, making it easier to obtain a base material with good whiteness.
The stretching may be uniaxial stretching, biaxial stretching (sequential biaxial stretching, simultaneous biaxial stretching, etc.), or multiaxial stretching (stretching by tubular method, etc.). Among these, biaxial stretching is preferable from the viewpoint that the effects of the present invention are easily exhibited.

(About process 2)
Examples of a method for providing a coat layer on one or both sides of a substrate include a method in which a coating liquid containing each component constituting the coat layer is applied to the surface of the substrate and dried.

The form of the coating liquid is not particularly limited, but may be one in which each component constituting the coating layer is dispersed or dissolved in a solvent. Examples of the solvent include water, organic solvents, and the like.
The coating liquid in the present invention is preferably an aqueous emulsion in which each component constituting the coating layer is dispersed in water.

The method for producing the aqueous emulsion is not particularly limited, and conventionally known methods such as emulsion polymerization can be employed.
Furthermore, an aqueous emulsion can also be prepared by using emulsion type components as raw materials for the coating layer. Examples of emulsion-type components include styrene-butadiene latex (styrene-butadiene copolymer emulsion).

To prepare the coating liquid, each component is mixed with a solvent for 1 to 5 minutes using a stirrer or a dispersion machine (e.g., wet colloid mill, edged turbine, paddle blade, etc.) under rotation conditions of 500 to 3000 rpm. One example is a method of dispersion.
Note that a dispersant may be added to prevent agglomeration of clay and heavy calcium carbonate. However, since the clay and heavy calcium carbonate each have approximately the same specific gravity, the clay and heavy calcium carbonate are unlikely to be unevenly distributed in the coating solution, and are generally easy to disperse uniformly.

As for the coating method, the coating liquid is applied to the surface of the substrate by an appropriate method (microgravure, roll coating, blade coating, bar coating, brush coating, spray coating, dipping, etc.), and then the coating layer is applied. Methods include drying and curing. The temperature for drying or curing the coat layer may be, for example, 90° C. or higher and 120° C. or lower.

(Other processes)
After the above "Step 2", the obtained printing sheet can be used for printing. The printing sheet may be subjected to a quality confirmation process, a packaging process, etc., as necessary.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples.

<Preparation of printing sheet>
A printing sheet was produced by the following method.

(1) Preparation of materials The materials for the base material and the coating layer were prepared as follows. Note that all numerical values in the table are equivalent amounts of the active ingredient.

(Base material)
Polyolefin resin: polypropylene homopolymer (melting point 160°C)
Inorganic substance powder: heavy calcium carbonate powder (average particle size by air permeation method according to JIS M-8511: 2.00 μm)

(Coat layer material)
The material of the coat layer is as follows.

[Clay]
Clay-1: Kaolin clay (volume average particle diameter 0.29 μm, specific gravity 2.5)
Clay-2: Kaolin clay (volume average particle diameter 1.50 μm, specific gravity 2.6)

[Heavy calcium carbonate]
Calcium carbonate-1: Heavy calcium carbonate (volume average particle diameter 0.01 μm, specific gravity 2.6)
Calcium carbonate-2: Heavy calcium carbonate (volume average particle diameter 0.15 μm, specific gravity 2.6)
Calcium carbonate-3: Heavy calcium carbonate (volume average particle diameter 3.00 μm, specific gravity 2.6)
Calcium carbonate-4: light calcium carbonate (volume average particle diameter 1.00 μm, specific gravity 2.6)

[Styrene-butadiene copolymer]
Styrene-butadiene copolymer-1: Styrene-butadiene latex ("JSR SBLTX, grade 0696", carboxy-modified emulsion, particle size: 170 nm, Tg: -12°C, manufactured by JSR Corporation)
Styrene-butadiene copolymer-2: Styrene-butadiene latex (“JSR SBLTX, grade 0589”, unmodified type emulsion, particle size: 220 nm, Tg: 0°C, manufactured by JSR Corporation)

[Polyamide resin]
Polyamide resin-1: Cationic polyamide resin ("Violaze Resin SPI-203 (50) H", degree of cationization: 3.00 meq/g, manufactured by Taoka Chemical Industry Co., Ltd.)
Polyamide resin-2: Anionic polyamide resin

(2) Preparation of base material Add the base material material to an extrusion molding machine (T-die extrusion molding device equipped with twin screws, φ20 mm, L/D=25) in the proportions shown in the "Base material" section in the table. After kneading at a temperature of 220°C or lower, it is formed into a sheet using a T-die at a forming temperature of 220°C, and biaxially stretched (3.5 times vertically x 5 times horizontally) while being rolled up using a take-up machine. A base material (128 mm long x 80 mm wide, 200 μm thick) was obtained.

(3) Formation of coat layer Clay, calcium carbonate, styrene-butadiene copolymer, and polyamide resin are mixed together with a dispersion medium (water) in the proportions shown in "Coat layer" in the table using an edged turbine. The mixture was stirred and mixed at 3000 rpm for 3 minutes to obtain a coating liquid (aqueous emulsion).
The resulting coating liquid was applied to the entire surface of one side of each base material by a microgravure method, and then dried at 110°C to obtain a base material provided with a coating layer (thickness: 8 μm).
In addition, the numerical value of the composition of "coat layer" in the table is a value of dry mass.

<Evaluation of printing sheets>
The strength of the coating layer and the printability of the printing sheet were evaluated using the following method. The results are shown in the "Evaluation" section of the table.

(Strength of coating layer)
The strength of the coat layer was evaluated by the following method. In this example, the adhesive strength of the coat layer to the base material was evaluated as the strength of the coat layer.

[Evaluation method of coating layer strength (adhesive strength)]
In order to evaluate the strength (adhesive strength) of the coat layer to the base material, a peel test using an adhesive tape was conducted by the following method.
As the adhesive tape, a cellophane adhesive tape (width: 24 mm) conforming to JIS Z1522:2009 was used.

(1) An adhesive tape with a length of about 75 mm was taken out.
(2) Adhesive tape was applied to the entire coating layer of each printing sheet, and the adhesive tape was rubbed with a finger so that the entire coating layer was visible. When scrubbing, press with the palm of your finger instead of using your nails.
(3) Within 5 minutes after applying the adhesive tape, the end of the adhesive tape was lifted and peeled off. When peeling off, the coating layer was completely peeled off in 0.5 to 1.0 seconds so that the peeling direction and the coating layer formed an angle of about 60°.
(4) After peeling off the adhesive tape, it was visually confirmed whether the coat layer was attached to the printing sheet, and the strength of the coat layer was evaluated based on the following evaluation criteria.
The less peeling of the coat layer from the printing sheet, the higher the strength (adhesive strength) of the coat layer.

[Evaluation criteria for strength of coat layer (adhesive strength)]
A: No peeling of the coating layer was observed.
B: Less than 20% of the coating layer was peeled off.
C: 20% or more of the coating layer was peeled off.

(Print suitability)
Offset printing suitability and laser printer (LBP) printing suitability were evaluated by the following methods.

[Evaluation method for offset printing suitability]
A test pattern was printed on each printing sheet (the surface provided with the coat layer) using an oil-based offset ink using an offset printing machine ("RMGT920", manufactured by Ryobi MHI Graphic Technology Co., Ltd.).
Visual observation was made within 30 seconds after printing was completed, and offset printing suitability (ink fixability and ink quick drying property) was evaluated based on the following criteria.

[Evaluation criteria for offset printing suitability]
A: The entire test pattern was printed, and no bleeding or misalignment of the print was observed.
B: Although the entire test pattern was printed, some bleeding and misalignment of the print was observed.
C: The entire test pattern is not printed (discontinuities, blurring, etc. are observed), and/or blurring or misalignment of the print is clearly observed.

[Evaluation method of laser printer (LBP) printing suitability]
Color and monochrome test patterns were printed on each printing sheet (the surface provided with the coat layer) using a laser printer ("Versant 80 Press", manufactured by Fuji Xerox Co., Ltd.).
Visual observation was made within 30 seconds after completion of printing, and LBP printing suitability (toner fixability) was evaluated based on the following criteria.

[Evaluation criteria for laser printer (LBP) printing suitability]
A: The entire test pattern was printed, and no toner peeling was observed.
B: The entire test pattern was printed, but some toner peeling was observed.
C: The entire test pattern is not printed (breaks, blurring, etc. are observed), and/or toner peeling is clearly observed.

As shown in the table, the printing sheet that met the requirements of the present invention had good strength and printability.

Claims (7)

A printing sheet comprising a base material and a coating layer provided on one or both sides of the base material,
The base material contains a polyolefin resin and an inorganic substance powder in a mass ratio of 50:50 to 10:90,
The coating layer contains clay, heavy calcium carbonate, styrene-butadiene copolymer, and cationic polyamide resin,
The content of the clay is 43% by mass or more and 63% by mass or less with respect to the coat layer,
The content of the heavy calcium carbonate is 24% by mass or more and 34% by mass or less with respect to the coat layer,
The content of the styrene-butadiene copolymer is 10% by mass or more and 20% by mass or less with respect to the coat layer,
The content of the cationic polyamide resin is 0.3% by mass or more and 0.7% by mass or less with respect to the coat layer,
The degree of cationization of the cationic polyamide resin is 2.00 meq/g or more and 4.00 meq/g or less,
Printing sheet. The printing sheet according to claim 1, wherein the polyolefin resin is a polypropylene resin. The printing sheet according to claim 1, wherein the clay has a volume average particle diameter of 0.05 μm or more and 2.00 μm or less. The printing sheet according to claim 1, wherein the weighted calcium carbonate has a volume average particle diameter of 0.05 μm or more and 2.00 μm or less. The printing sheet according to any one of claims 1 to 4, wherein the printing sheet is an offset printing sheet. A method for producing a printing sheet including a coating layer forming step of providing a coating layer on one or both sides of a base material,
The base material contains a polyolefin resin and an inorganic substance powder in a mass ratio of 50:50 to 10:90,
The coating layer contains clay, heavy calcium carbonate, styrene-butadiene copolymer, and cationic polyamide resin,
The content of the clay is 43% by mass or more and 63% by mass or less with respect to the coat layer,
The content of the heavy calcium carbonate is 24% by mass or more and 34% by mass or less with respect to the coat layer,
The content of the styrene-butadiene copolymer is 10% by mass or more and 20% by mass or less with respect to the coat layer,
The content of the cationic polyamide resin is 0.3% by mass or more and 0.7% by mass or less with respect to the coat layer,
The degree of cationization of the cationic polyamide resin is 2.00 meq/g or more and 4.00 meq/g or less,
Production method. Before the coat layer forming step,
a molding step of extruding the base material into a sheet shape;
After the forming step, a stretching step of stretching the base material;
The manufacturing method according to claim 6, comprising: