KR20230043850A - heat seal paper - Google Patents

Abstract

An object of the present invention is to provide a heat-sealing paper that is suitably used for packaging applications such as packaging materials, bags, containers, boxes, cups, lids, and the like, and has heat-sealing properties and good blocking resistance.
As a solution, the present invention has a coating layer containing a thermoplastic resin on at least one side of a paper base material, the coating layer contains at least a pigment as an antiblocking agent, and the blending amount of the pigment in the coating layer is thermoplastic. A heat seal paper containing less than 200 parts by mass per 100 parts by mass of resin is provided.

Description

heat seal paper

The present invention relates to heat-sealing paper, particularly heat-sealing paper having heat-sealing properties that is suitably used for packaging applications such as packaging materials, bags, containers, boxes, cups, lids, and the like.

In recent years, plastic waste has been dealt with as a major problem because there is a concern that plastics that have flowed out as garbage into the environment do not decompose semipermanently and adversely affect the ecosystem. As a countermeasure, it is proposed to replace plastics with paper, which is a material derived from biomass or a biodegradable material.

On the other hand, conventionally, when molding paper packaging materials into packaging materials such as food, bags, containers, boxes, cups, covers, etc., thermoplastic resins represented by polyolefin resins such as polyethylene, polypropylene, and polymethylpentene are extruded. Laminating on a packaging material by a lamination method or the like to impart heat-sealing aptitude is generally performed.

However, in the lamination of these thermoplastic resins, about 10 to 30 g/m 2 of the thermoplastic resin is used, and reduction of the amount of plastic is not sufficient. From this fact, currently, wrapping paper in which a coating layer to be laminated is thinned and reduced in weight is provided by coating a water or solvent dispersion containing a thermoplastic resin dispersion on a paper base material (Patent Document 1 and the like).

However, it is necessary to apply heat in the paint drying step when laminating the coated layer by coating, and when molding paper-made packaging materials into packaging materials such as food, bags, containers, boxes, cups, lids, etc. . At this time, when heat remains after each process (the thermoplastic resin remains softened), there is a problem that blocking occurs and the product becomes defective. In addition, the coated paper is wound in a roll shape and stored until it is formed, but there is a problem in that blocking occurs during long-term storage at room temperature. For this reason, it is necessary to provide a wrapping paper having good blocking resistance and heat sealing ability.

Japanese Patent No. 6580291

An object of the present invention is to provide a heat-sealing paper that is suitably used for packaging applications such as packaging materials, bags, containers, boxes, cups, covers, and the like, and has heat-sealing properties and good blocking resistance.

Means for solving the problems of the present invention are as follows.

1. Have a coating layer containing a thermoplastic resin on at least one side of the paper base material,

The coating layer contains at least a pigment as an antiblocking agent,

A heat seal paper characterized in that the blending amount of the pigment in the coating layer is less than 200 parts by mass with respect to 100 parts by mass of the thermoplastic resin.

2. Have a coating layer containing a thermoplastic resin on at least one side of the paper base material,

The coating layer contains at least wax as an antiblocking agent,

The heat seal paper characterized in that the mixing amount of the wax in the coating layer is 1.2 parts by mass or more with respect to 100 parts by mass of the thermoplastic resin.

3. The heat seal paper described in 1. or 2. characterized by containing both a wax and a pigment as an antiblocking agent.

4. The heat seal paper according to any one of 1. to 3., wherein the coating layer contains a thermoplastic resin having a glass transition temperature of 100°C or lower.

5. The heat seal paper according to any one of 1. to 4., wherein the coating layer contains carnauba wax.

6. The heat seal paper according to any one of 1. to 5., wherein the thermoplastic resin contained in the coating layer is an ethylene acrylic acid copolymer resin.

ADVANTAGE OF THE INVENTION According to this invention, the heat seal paper which is suitably used for packaging applications, has heat sealing ability, and has favorable blocking resistance can be provided. By using a pigment and wax together as an antiblocking agent, required blocking resistance can be imparted depending on circumstances.

The present invention is a heat-seal paper having a coating layer containing a thermoplastic resin on at least one side of a paper base material, wherein the coating layer contains at least one antiblocking agent selected from wax or pigment, and the coating layer is heat-sealed. It relates to a heat seal paper characterized by having sealing aptitude.

(paper materials)

The paper base material is obtained by papermaking a paper stock containing pulp, filler, various auxiliary agents, and the like.

When the heat seal paper of the present invention is used for contact with food, it is preferable to use materials suitable for food safety, such as approved as food additives or FDA certified, as each material of the paper base material.

As the pulp, chemical pulp of wood such as bleached kraft pulp (NBKP), unbleached kraft pulp (NUKP) of softwoods, bleached kraft pulp (LBKP) of hardwoods, unbleached kraft pulp (LUKP), sulfite pulp (SP), Grand Pulp (GP), Refiner Grand Pulp (RGP), Stone Grand Pulp (SGP), Chemi Grand Pulp (CGP), Semi Chemical Pulp (SCP), Thermo Mechanical Pulp (TMP), Chemi Thermo Mechanical Pulp (CTMP), etc. Known pulps such as mechanical pulp of wood, non-wood pulp obtained from kenaf, bagasse, bamboo, hemp, straw, etc., used paper pulp obtained from waste paper and ink contained in waste paper removed in the deinking process It is possible to use them in an appropriate combination. Among these, chemical pulps such as LBKP and NBKP, which do not easily contain foreign substances, are preferred, and those with a small amount of used paper pulp are preferred. Specifically, it is preferable that the blending amount of the chemical pulp is 80% or more, and it is particularly preferable that the blending amount of the chemical pulp is 100%. Further, the blending amount of used paper pulp is preferably 10% or less, more preferably 1% or less, and most preferably not included.

As the filler, talc, kaolin, calcined kaolin, clay, ground calcium carbonate, light calcium carbonate, white carbon, zeolite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide , inorganic fillers such as zinc hydroxide, barium sulfate, and calcium sulfate, and organic fillers such as urea-formalin resin, polystyrene resin, phenol resin, and microscopic hollow particles can be used. In addition, a filler is not an essential material and does not need to be used.

Examples of various adjuvants include sizing agents such as rosin, alkyl ketene dimer (AKD), and alkenyl succinic anhydride (ASA), polyacrylamide-based polymers, polyvinyl alcohol-based polymers, cationized starch, various modified starches, urea formalin resins, Dry strength enhancers such as melamine and formalin resin, wet strength enhancers, yield agents, water retention improvers, coagulants, sulfuric acid bands, bulking agents, dyes, optical whitening agents, pH adjusters, antifoaming agents, UV inhibitors, anti-fading agents, pitch control agents, A slime control agent etc. can be exemplified, and it can be used by selecting suitably as needed.

The manufacturing (papermaking) method of the paper substrate is not particularly limited, and a known manufacturing (papermaking) method such as a twin wire papermaking machine such as a long net paper machine, a long net paper machine, a short net paper machine, a gap former type, and a hybrid former type (on-top former type) , the paper machine can be selected. In addition, the pH at the time of papermaking may be any of an acidic region (acidic grassland), a quasi-neutral region (pseudo-neutral grassland), a neutral region (neutral grassland), and an alkaline region (alkaline grassland), and after papermaking in an acidic region, the stratum You may coat an alkaline agent on the surface of. In addition, the paper base material may be one layer or may be constituted by a multilayer of two or more layers.

In addition, it is possible to treat the surface of the paper base material with various chemicals. Examples of the agent used include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agent, water-resistance agent, water retention agent, thickener, lubricant, and the like, these alone or in combination with two More than types can be mixed and used. Moreover, you may use these various chemicals and pigments together. As pigments, kaolin, clay, engineered kaolin, dilaminated clay, heavy calcium carbonate, precipitated calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, satin white, etc. Inorganic pigments and organic pigments such as solid-type, hollow-type, or core-shell type may be used alone or in combination of two or more.

The surface treatment method of the paper substrate is not particularly limited, but a known coating device such as a rod metering size press, a pond type size press, a gate roll coater, a spray coater, a blade coater, and a curtain coater can be used.

As the paper base material obtained in this way, various known papers such as fine paper, medium quality paper, coated paper, one-side glazed paper, kraft paper, dyed kraft paper, bleached kraft paper, glassine paper, cardboard, white paper, liner, etc. that can be exemplified.

The basis weight of the paper substrate can be appropriately selected depending on the desired quality, handling, etc., but is usually preferably 20 g/m 2 or more and 600 g/m 2 or less. In the case of heat seal paper used for packaging such as food packaging materials, bags, containers, boxes, cups, cover materials, etc., it is more preferable that it is 25 g / m 2 or more and 600 g / m 2 or less, especially bags, cover materials, Or, in the case of heat seal paper used for flexible packaging materials described later, 30 g/m or more and 150 g/m or less, and in the case of heat seal paper used for containers, boxes, and cups, 150 g/m or more It is more preferable that it is 350 g/m<2> or less. In addition, a flexible packaging material is a packaging material composed of a material rich in flexibility as a structure, and generally refers to a packaging material in which thin and flexible materials such as paper, film, and aluminum foil are individually or bonded together. In addition, the shape refers to a packaging material such as a bag that maintains a three-dimensional shape by putting the contents therein.

In addition, the density of the paper base material can be appropriately selected depending on the desired quality, handling properties, etc., but it is usually preferably 0.5 g/cm 3 or more and 1.0 g/cm 3 or less.

(coating layer)

The coating layer contains a thermoplastic resin and at least one antiblocking agent selected from wax or pigment. The coating layer can be provided on both sides of the heat seal paper, but it is provided on at least one side.

The coating layer has heat sealing aptitude. Having heat-sealing ability means being able to adhere to an adhesion target by heating and pressurizing. Having heat-sealing aptitude makes it easy to mold into a packaging form, maintain a shape, and secure sealing properties, especially in packaging applications such as food packaging materials, bags, containers, boxes, cups, lids, and the like.

・Thermoplastic resin

As the thermoplastic resin used in the present invention, those used for forming the heat seal layer in the papermaking field can be used without particular limitation, and, for example, those having a glass transition temperature of 100° C. or less can be used. The glass transition temperature of the thermoplastic resin is preferably -20°C or more and 85°C or less. Moreover, it is preferable that the melting point of a thermoplastic resin is 80 degreeC or more and 120 degreeC or less. As the thermoplastic resin, for example, low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polypropylene (PP), polyvinyl acetate (PVAc), polyester resins (PEs), ethylene meta Acrylic acid copolymer resin (EMAA), ethylene methyl acrylate copolymer resin (EMA), ethylene acrylic acid copolymer resin (EAA), ethylene vinyl acetate copolymer resin (EVA), styrene acrylic acid ester copolymer resin, polylactic acid resin and the like can be used. In addition, thermoplastic resin can be used 1 type or in mixture of 2 or more types. Among these, ethylene acrylic acid copolymer resins having high heat-sealing ability are preferred.

・Anti-blocking agent

The heat seal paper of the present invention contains a pigment or wax as an antiblocking agent. It is also possible to include both pigments and waxes as antiblocking agents.

(Pigment)

The pigment used in the present invention is not particularly limited, and kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, precipitated calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid , inorganic pigments such as silicate, colloidal silica, and satin white, and organic pigments such as dense, hollow, or core-shell type. In addition, 1 type or a mixture of 2 or more types can be used for a pigment. Among these, ground calcium carbonate is preferable because it does not impair heat sealing ability and is excellent in blocking resistance.

In the present invention, the blending amount of the pigment is less than 200 parts by mass and more preferably 150 parts by mass or less based on 100 parts by mass of the thermoplastic resin in dry weight. When the blending amount of the pigment is 200 parts by mass or more, the heat sealing temperature may become too high, or the heat sealing may take time. Moreover, it is preferable to contain 50 parts by mass or more of the pigment with respect to 100 parts by mass of the thermoplastic resin in dry weight, and it is more preferable to include 80 parts by mass or more. When the blending amount of the pigment is less than 50 parts by mass, the blocking resistance may be insufficient.

(wax)

The wax used in the present invention is not particularly limited, and paraffinic waxes mainly composed of alkane compounds, natural oil-based waxes derived from animals and plants such as carnauba and lanolin, silicone-containing waxes containing silicones or silicone compounds, and fluorine compounds. A fluorine-containing wax containing may be used. Waxes can be used alone or in combination of two or more. Among these, carnauba wax is preferred.

In the present invention, the blending amount of the wax is 1.2 parts by mass or more, preferably 1.5 parts by mass or more, and more preferably 2.5 parts by mass or more with respect to 100 parts by mass of the thermoplastic resin in dry weight. If the blending amount of the wax is less than 1.2 parts by mass, blocking resistance may not be sufficiently obtained. In addition, it is preferable to contain 15 parts by mass or less of wax, more preferably 10 parts by mass or less, based on dry weight to 100 parts by mass of the thermoplastic resin. Even if the compounding amount of the wax exceeds 15 parts by mass, the blocking resistance hardly improves and the cost increases.

Pigments and waxes are both antiblocking agents, and while pigments mainly contribute to blocking resistance in a heated state such as during processing, wax mainly contributes to blocking resistance during long-term storage. By using a pigment and wax together as an antiblocking agent, required blocking resistance can be imparted depending on circumstances. The mixing ratio of the pigment and the wax can be adjusted according to the conditions requiring blocking resistance, and for example, 1 part by mass or more and 200 parts by mass or less of the wax can be used with respect to 100 parts by mass of the pigment in dry weight.

The coating method of the coated layer is not particularly limited, and can be coated with a known coating device and coating system. For example, as a coating apparatus, a blade coater, a bar coater, an air knife coater, a curtain coater, a spray coater, a roll coater, a reverse roll coater, a size press coater, a gate roll coater, etc. are mentioned. Further, examples of the coating system include water-based coating using a solvent such as water, solvent-based coating using a solvent such as an organic solvent, and the like. Since the heat seal paper of the present invention is sometimes used for applications in contact with food or the like, water-based coating is preferable from the viewpoint of food safety.

The viscosity of the coating solution, the concentration of solid content, and the like can be appropriately adjusted depending on the coating device and coating system to be used.

It is preferable that the coating amount (dry weight) of the coating layer is 3 g/m 2 or more and 20 g/m 2 or less per side. When the coating amount is less than 3 g/m 2 per side, the heat sealing ability decreases. Further, even if the coating amount exceeds 20 g/m 2 per side, the heat-sealing ability hardly improves, and the cost increases. The coating layer may consist of one layer or a multilayer of two or more layers. When the coated layer is constituted by a multilayer of two or more layers, it is preferable to make the total coating amount of all the coated layers within the above range.

The heat seal paper of the present invention may have a coating layer and a paper base material, and may have other layers such as a peeling layer, a printing layer, a light shielding layer, a water resistance layer, an oil resistance layer, a water vapor barrier layer, a gas barrier layer, and the like. It is preferable to have a peeling layer between the and the paper base material. By having a peeling layer, occurrence of coating defects such as pinholes and streaks in the coating layer can be reduced, and water resistance and oil resistance can be improved.

The heat-sealing paper of the present invention can be used as a heat-sealing paper used for packaging such as food packaging materials, bags, containers, boxes, cups, lids, and the like.

Example

(Assessment Methods)

(1) Heat sealing aptitude

(Heat sealing conditions)

Two square test pieces with a side of 100 mm were cut out from the obtained heat seal paper, the coated layers were brought into contact with each other, and heat-sealed at a press temperature of 160° C., a press pressure of 2 kgf/cm 2 and a press time of 0.5 seconds.

When the heat-sealed test piece was peeled off by hand, the peeled portion was observed with the naked eye, and the heat-sealing aptitude was evaluated based on the following criteria.

A: Peeling within the paper substrate (the paper substrate is destroyed)

B: Peeling between coating layers

(2) Blocking A

This is an evaluation that assumes the storage of products in a warehouse or the like.

The coating layers were brought into contact with each other according to ASTM D918-81, Standard Test Method for Blocking Resistance of Paper and Peperboard, and the degree of blocking after storage at 60°C and RH75% for 24 hours was evaluated. If the evaluation is A or B, there is no problem in practice.

[Evaluation standard]

A: No blocking

B: It has mild blocking and can be easily peeled off.

C: Strongly blocked and cannot be easily peeled off

(3) Blocking B

It is an evaluation assuming sticking when a heated coating layer contacts each equipment in the case of manufacturing or processing a product.

A humidity-adjusted sample (23°C, RH50%) is passed through a hot roll press machine (roll pressure 0.5 MPa, processing speed 2 m/min, arbitrary roll temperature) so that the coated surface and the metal roll come into contact, The degree of sticking to the metal roll was evaluated. If the evaluation is A or B, there is no problem in practice.

[Evaluation standard]

A: When the roll temperature is 70°C, no sticking is observed, and no damage to the coated surface is observed.

B: When the roll temperature is 60°C, no sticking is observed and no damage to the coated surface is observed.

C: When the roll temperature is 60°C, damage to the coated surface is observed, such as sticking of the coated layer to the metal roll and peeling of the coated layer from the metal roll.

[Example 1]

(Preparation of coating liquid for coating layer)

A thermoplastic resin (made by Michelman: MICHEM PRIME 498345N.S) and kaolin (manufactured by Imeris: Varisurf HX, aspect ratio 95) were prepared so as to be 100.0/100.0 parts, respectively, in solid mass ratio, to obtain a coating solution for the coating layer.

(Manufacture of heat seal paper)

The coating liquid for the coating layer was coated on one side of a paper base material (cup base paper having a basis weight of 200 g/m 2 ) by a bar blade method so that the coating amount in dry weight was 10.0 g/m 2 and dried to obtain heat seal paper.

[Example 2]

Heat seal paper was obtained in the same manner as in Example 1, except that the pigment was changed to ground calcium carbonate (FMT-100 manufactured by Pimatech Co., Ltd.).

[Example 3]

A heat seal paper was obtained in the same manner as in Example 1, except that the pigment was precipitated calcium carbonate (TunexE, manufactured by New Lime Co., Ltd.).

[Example 4]

Examples except that the coating liquid for the coating layer was prepared so that the thermoplastic resin (manufactured by Michelman: MICHEM PRIME 498345N.S) and carnauba wax (manufactured by Michelman: MICHEM LUBE 160RPH.S) were 100.0/2.9 parts, respectively, in terms of solid mass ratio. In the same manner as in 1, heat seal paper was obtained.

[Example 5]

Heat seal paper was obtained in the same manner as in Example 4, except that the solid content mass ratio of the thermoplastic resin to the wax was 100.0/6.1 parts.

[Example 6]

The coating liquid for the coating layer was a thermoplastic resin (manufactured by Michelman: MICHEM PRIME 498345N.S), kaolin (manufactured by Imeris: Varisurf HX), and carnauba wax (manufactured by Michelman: MICHEM LUBE 160RPH.S) in solid mass ratio. Heat seal paper was obtained in the same manner as in Example 1, except that each was prepared to be 100.0/100.0/2.9 parts.

[Comparative Example 1]

Heat seal paper was obtained in the same manner as in Example 1, except that a coating liquid for a coating layer containing only a thermoplastic resin (manufactured by Michelman: MICHEM PRIME 498345N.S) was used.

[Comparative Example 2]

Heat seal paper was obtained in the same manner as in Example 1, except that the solid content mass ratio of the thermoplastic resin and kaolin was 100.0/200.0 parts.

[Comparative Example 3]

Heat seal paper was obtained in the same manner as in Example 1, except that the mass ratio of the solid content of the thermoplastic resin to the wax was 100.0/1.1 part.

The heat seal papers obtained in Examples 1 to 6 of the present invention had excellent blocking resistance. The heat seal papers obtained in Examples 1 to 3 containing a pigment as an antiblocking agent have excellent workability, and the heat seal papers obtained in Examples 4 and 5 containing a wax as an antiblocking agent have particularly excellent long-term storage properties did In addition, the heat seal paper obtained in Example 6 containing both a pigment and a wax as an antiblocking agent was excellent in both long-term storage and workability.

The heat seal paper obtained in Comparative Example 1 containing no antiblocking agent and the heat seal paper obtained in Comparative Example 3 in which the amount of wax as an antiblocking agent was small were inferior in blocking resistance. The heat seal paper obtained in Comparative Example 2 having a large amount of pigment as an antiblocking agent had excellent blocking resistance, but was inferior in heat sealing ability from the beginning.

Claims (6)

having a coating layer containing a thermoplastic resin on at least one side of the paper base material;
The coating layer contains at least a pigment as an antiblocking agent,
The heat seal paper characterized in that the blending amount of the pigment in the coating layer is less than 200 parts by mass with respect to 100 parts by mass of the thermoplastic resin. having a coating layer containing a thermoplastic resin on at least one side of the paper base material;
The coating layer contains at least wax as an antiblocking agent,
The heat seal paper characterized in that the mixing amount of the wax in the coating layer is 1.2 parts by mass or more with respect to 100 parts by mass of the thermoplastic resin. According to claim 1 or 2,
A heat seal paper comprising both a wax and a pigment as an antiblocking agent. According to any one of claims 1 to 3,
Heat seal paper, characterized in that the coating layer comprises a thermoplastic resin having a glass transition temperature of 100 ℃ or less. According to any one of claims 1 to 4,
Heat seal paper, characterized in that the coating layer contains carnauba wax. According to any one of claims 1 to 5,
Heat seal paper, characterized in that the thermoplastic resin contained in the coating layer is an ethylene acrylic acid copolymer resin.