JP2021070171A - Heat seal paper - Google Patents

Abstract

To provide a heat seal paper having heat sealing suitability and excellent disintegrating property when being recycled that is suitably used for packing applications such as a packing material, a bag, a container, a box, a cup, a lid material especially for food and the like.SOLUTION: A heat seal paper has a heat seal layer containing styrene acrylate-based copolymer resin on a paper substrate.SELECTED DRAWING: None

Description

The present invention relates to a heat-sealing paper having heat-sealing suitability, which is particularly preferably used for packaging materials such as food packaging materials, bags, containers, boxes, cups, and lid materials.

Conventionally, when a paper packaging material is molded into a packaging material such as food, a bag, a container, a box, a cup, a lid material, etc., a thermoplastic resin typified by a polyolefin resin such as polyethylene, polypropylene, polymethylpentene, etc. Is generally laminated on a packaging material by an extrusion laminating method or the like to impart heat seal suitability (Patent Document 1 and the like). However, paper packaging materials in which these thermoplastic resins are laminated are generally treated as non-recyclable contraindicated products because they are inferior in recyclability during recycling, and are collected and recycled as recycled paper raw materials. Can't.

Japanese Unexamined Patent Publication No. 2017-024187

Therefore, the present invention is a heat-sealing paper which is suitable for packaging materials such as foods, bags, containers, boxes, cups, lids, etc., and has heat-sealing suitability and good disintegration property at the time of recycling. The purpose is to provide.

The present invention provides the following [1] to [6].
[1] A heat-sealing paper characterized by having a heat-sealing layer containing a styrene acrylic acid ester-based copolymer resin on a paper base material.
[2] The heat-sealing paper according to [1], wherein the heat-sealing layer is a coating layer.
[3] The heat-sealing paper according to [2], wherein the coating amount (dry weight) of the heat-sealing layer is 3 g / m ² or more and 20 g / m ^{2 or less per side.}
[4] The heat-sealed paper according to any one of [1] to [3], wherein the basis weight of the paper base material is 20 g / m ² or more and 600 g / m ^{2 or less.}
[5] The heat-sealed paper according to any one of [1] to [3], wherein the basis weight of the paper base material is 30 g / m ² or more and 150 g / m ^{2 or less.}
[6] The heat-sealed paper according to any one of [1] to [5], wherein the density of the paper base material is 0.5 g / cm ³ or more and 1.0 g / cm ^{3 or less.}

According to the present invention, it is possible to provide a heat-sealing paper which is suitable for packaging and has heat-sealing suitability and good disintegration property at the time of recycling.

The present invention relates to a heat-sealed paper characterized by having a heat-sealed layer containing a styrene acrylic acid ester-based copolymer resin on a paper base material.

(Paper base material)
In the present invention, the paper base material is a sheet mainly made of pulp (hereinafter, also referred to as "base paper"), and is obtained by papermaking a paper material containing a filler, various auxiliary agents, and the like.
Examples of pulp include broad-leaved bleached kraft pulp (LBKP), coniferous bleached kraft pulp (NBKP), broad-leaved unbleached kraft pulp (LUKP), coniferous unbleached kraft pulp (NUKP), chemical pulp such as sulfite pulp, stone grind pulp, and thermo. Mechanical pulp such as mechanical pulp, wood fiber such as deinked pulp and used paper pulp, non-wood fiber obtained from kenaf, bamboo, hemp and the like can be used, and can be appropriately blended and used. Among these, foreign matter is unlikely to be mixed into the base paper, discoloration is unlikely to occur when the used paper container is used as a raw material for used paper and recycled, and it has a high degree of whiteness during printing. It is preferable to use chemical pulp or mechanical pulp of wood fiber, and more preferably chemical pulp, because the surface feel is good and the utility value is high especially when used as a packaging material. Specifically, the blending amount of chemical pulp such as LBKP and NBKP is preferably 80% or more, and the blending amount of chemical pulp is particularly preferably 100%.

Fillers include talc, kaolin, calcined kaolin, clay, heavy calcium carbonate, light calcium carbonate, white carbon, zeolite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, and aluminum hydroxide. , Inorganic fillers such as calcium hydroxide, magnesium hydroxide, zinc hydroxide, barium sulfate, calcium sulfate, and organic fillers such as urea-formalin resin, polystyrene resin, phenolic resin, and fine hollow particles are used. be able to. The filler is not an essential material and does not have to be used.

Examples of various auxiliary agents include sizing agents such as rosin, alkyl keten dimer (AKD), alkenyl succinic acid anhydride (ASA), polyacrylamide-based polymers, polyvinyl alcohol-based polymers, cationized starch, various modified starches, urea, etc. Dry paper strength enhancer such as formalin resin, melamine / formalin resin, wet paper strength enhancer, retention agent, drainage improver, coagulant, sulfate band, bulking agent, dye, fluorescent whitening agent, pH adjuster, Examples thereof include a defoaming agent, an ultraviolet inhibitor, a fading inhibitor, a pitch control agent, a slime control agent, and the like, and they can be appropriately selected and used as necessary.

The method for manufacturing (paper making) the paper base material is not particularly limited, and is a long net paper machine, a circular net paper machine, a short net paper machine, a gap former type, a hybrid former type (on-top former type), etc. A known manufacturing (paper making) method, such as a twin wire paper machine, and a paper machine can be selected. The pH at the time of papermaking may be any of an acidic region (acidic papermaking), a pseudo-neutral region (pseudo-neutral papermaking), a neutral region (neutral papermaking), and an alkaline region (alkaline papermaking). After that, an alkaline chemical may be applied to the surface of the paper layer. Further, the paper base material may have one layer or may be composed of two or more layers.

Furthermore, the surface of the paper substrate can be treated with various chemicals. Examples of the chemicals used include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agents, water resistant agents, water retention agents, thickeners, lubricants, and the like. These can be used alone or in combination of two or more. Furthermore, these various agents and pigments may be used in combination. Pigments include kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, and satin. Inorganic pigments such as white and organic pigments such as solid type, hollow type, and core-shell type can be used alone or in combination of two or more.

The method of surface treatment of the paper substrate is not particularly limited, but a known coating device such as a rod metering size press, a pound type size press, a gate roll coater, a spray coater, a blade coater, or a curtain coater should be used. Can be done.
The paper base material thus obtained includes high-quality paper, medium-quality paper, coated paper, single-gloss paper, kraft paper, single-gloss kraft paper, bleached kraft paper, glassin paper, paperboard, white paperboard, liner, and the like. Various known ones can be exemplified.

The basis weight of the paper base material can be appropriately selected depending on the desired quality, handleability, etc., but is usually preferably 20 g / m ² or more and 600 g / m ² or less. In the case of heat-sealed paper used for packaging such as packaging materials for foods, bags, containers, boxes, cups, lids, etc., 25 g / m ² or more and 600 g / m ² or less are more preferable, and bags and lids in particular. In the case of heat-sealed paper used for materials or flexible packaging materials described later, those of 30 g / m ² or more and 150 g / m ² or less are more preferable.
The density of the paper base material can be appropriately selected depending on the desired quality, handleability, etc., but usually 0.5 g / cm ³ or more and 1.0 g / cm ³ or less is preferable.

(Heat seal layer)
In the present invention, a heat seal layer containing a styrene acrylic acid ester-based copolymer resin is provided on a paper substrate. The heat seal layer may be provided on both sides of the heat seal paper, but has at least one side.
The heat seal layer is a layer that imparts heat seal suitability, and specifically, is a layer that can be adhered to an object to be bonded by heating and pressurizing. Having heat-sealing suitability makes it easy to mold into a packaging form, maintain its shape, and ensure hermeticity, especially in packaging applications such as packaging materials for foods, bags, containers, boxes, cups, and lid materials. ..

In the present invention, the heat seal layer is preferably a coating layer. By using the heat seal layer as the coating layer, the manufacturing efficiency is improved and the recyclability is improved as compared with the laminating by the extrusion laminating method or the like.

The coating method of the heat seal layer is not particularly limited, and coating can be performed by a known coating apparatus and coating system. For example, examples of the coating apparatus include 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, and the like. 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-sealed paper of the present invention may be used for applications such as contact with foods, water-based coating is preferable from the viewpoint of food safety.

The coating amount (dry weight) of the heat seal layer is preferably ^{3 g / m 2} or more and 20 g / m ^{2 or less per side.} If the coating amount is ^{less than 3 g / m 2} per side, the heat seal suitability is lowered. Further, even if the coating amount ^{exceeds 20 g / m 2} per side, the heat seal suitability is hardly improved and the cost is increased. The heat seal layer may be one layer or may be composed of two or more layers. When the heat-sealing layer is composed of two or more layers, it is preferable that the total coating amount of all the heat-sealing layers is within the above range.

The heat-sealing paper of the present invention can be a heat-sealing paper used for packaging materials such as foods, bags, containers, boxes, cups, lid materials and the like. Among these, it can be suitably used as a bag for foods, a lid material, and a flexible packaging material. The flexible packaging material is a packaging material composed of a highly flexible material, and generally, a thin and flexible material such as paper, film, or aluminum foil is used alone or laminated. Refers to packaging material. The shape refers to a packaging material such as a bag that maintains a three-dimensional shape by containing the contents.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is, of course, not limited to these examples. Unless otherwise specified, parts and% in the example indicate parts by weight and% by weight, respectively. The obtained heat-sealed paper was tested based on the evaluation method as shown below.

(Evaluation method)
(1) Heat seal suitability (heat seal conditions)
Two square test pieces having a side of 100 mm are cut out from the obtained heat-seal paper, and the heat-seal layers are brought into contact with each other to heat at a pressurization temperature of 120 ° C., a pressurization pressure of 2 kgf / cm ² , and a pressurization time of 1 second. Sealed.
When the heat-sealed test piece was peeled off by hand, the peeled portion was visually observed and the heat-sealing property was evaluated according to the following criteria.
〇: Peeling in the paper base material (paper base material is destroyed).
X: Peeled between heat seal layers.
(2) Detachability Prepare a heat-sealed paper with an absolute dry weight of 15 g, immerse it in water so that the concentration of the heat-sealed paper is 1.5% by weight, and use a pulp disintegration tester (manufactured by Kumagai Riki Kogyo Co., Ltd., JIS). The degree of dissociation into the aqueous solution was evaluated when the dissociation was carried out for 30 minutes according to P 8220). If the evaluation is ○, there is no problem in practical use.
[Evaluation criteria]
◯: Pulp fibers are dispersed and good disintegration property △: Slight pulp fiber binding remains ×: Pulp fiber lumps and pulp fiber binding remaining and poor disintegration property

[Example 1]
(Preparation of paper substrate)
Hardwood kraft pulp (LBKP) with a Canadian standard filtrate (CSF) of 500 ml and softwood kraft pulp (NBKP) with a CSF of 530 ml were blended at a weight ratio of 80/20 to prepare raw material pulp.
Polyacrylamide (PAM) having a molecular weight of 2.5 million as a dry paper strength enhancer was added to the raw material pulp at 0.1% per resistance dry pulp weight, and alkyl keten dimer (AKD) was added as a sizing agent at 0.35 per resistance dry pulp weight. %, Polyamide epichlorohydrin (PAEH) -based resin as a wet paper strength enhancer is 0.15% per absolute dry pulp weight, and polyacrylamide (PAM) having a molecular weight of 10 million as a retention agent is added to the absolute dry pulp weight. After adding 0.08% per pulp, the pulp was made with a duoformer FM paper machine at a speed of 300 m / min to obtain a base ^{paper having a basis weight of 39 g / m 2.}
Next, polyvinyl alcohol (PVA117 manufactured by Kuraray Co., Ltd.) prepared to have a solid content concentration of 2% was coated on the obtained base paper with a rod metering size press at a total of 1.0 g / m ^{2 on} both sides, dried, and then chilled. Smoothing was performed using a calendar to obtain a paper substrate having a basis weight of 40 g / m ² and a density of 0.75 g / cm ^3.

(Making heat seal paper)
On the obtained paper substrate, a styrene acrylic acid ester-based copolymer resin (Harville HS-1 manufactured by Daiichi Paint Co., Ltd.) was applied using a bar blade coater so ^{that the coating amount was 10.0 g / m 2 by dry weight.} It was coated on one side and dried to obtain a heat-sealed paper.

[Example 2]
A heat-sealed paper was obtained in the same manner as in Example 1 except that the base paper had a basis weight of 69 g / m ² and a paper substrate having a basis weight of 70 g / m ² and a density of 0.75 g / cm ^{3 was used.}
[Example 3]
The basis weight of the base paper and 119 g / ^{m 2,} a basis weight of 120 g / ^{m 2,} except for using paper substrate of density 0.75 g / cm ^3, in the same manner as in Example 1 to obtain a heat seal paper.

As shown in Table 1, the heat-sealed papers of Examples 1 to 3 had heat-sealing suitability and good disintegration property at the time of recycling.

Claims (6)

A heat-sealing paper characterized by having a heat-sealing layer containing a styrene acrylic acid ester-based copolymer resin on a paper base material. The heat-sealing paper according to claim 1, wherein the heat-sealing layer is a coating layer. The heat-sealing paper according to claim 2, wherein the coating amount (dry weight) of the heat-sealing layer is 3 g / m ² or more and 20 g / m ^{2 or less per side.} The heat-sealed paper according to any one of claims 1 to 3, wherein the basis weight of the paper base material is 20 g / m ² or more and 600 g / m ^{2 or less.} The heat-sealed paper according to any one of claims 1 to 3, wherein the basis weight of the paper base material is 30 g / m ² or more and 150 g / m ^{2 or less.} The heat-sealed paper according to any one of claims 1 to 5, wherein the density of the paper base material is 0.5 g / cm ³ or more and 1.0 g / cm ^{3 or less.}