JP7097659B2 - Adhesive packaging material for stored items - Google Patents

Description

The present invention relates to a packaging material in which a release agent layer such as silicone is laminated so that an adhesive container does not adhere to the inner surface.

For packaging of products coated with various pastes or adhesives, those having a release agent such as silicone coated on the inner surface are generally used. Since heat sealing cannot be performed on the portion coated with this release agent, a technique for applying the release agent while leaving a heat seal allowance has also been developed (Patent Document 1). The release agent used there is a silicone type, which is laminated on the polyacrylonitrile layer.

In addition, when applying a release agent such as silicone, since silicone is colorless and it is difficult to distinguish between the coated part and the uncoated part, we have also developed a technique to apply a colored release agent on the boundary in a line shape. (Patent Document 2).

Japanese Patent No. 4549732 Japanese Patent No. 5590489

A release agent such as silicone has a weak adhesive force due to its nature, and has a problem that it is easily peeled off when applied to a base material layer such as a film or a sheet. Therefore, it is effective to perform activation treatment such as corona treatment and frame treatment on the surface of the base material layer to which the release agent is applied to improve the adhesiveness of the release agent. Sealing property deteriorates. In particular, polyethylene terephthalate (PET) not only has high heat resistance and transparency, but also has excellent properties as a packaging material such as not absorbing odors unlike polyethylene and polypropylene, but it is subjected to surface activation treatment. And the heat sealability tends to weaken. On the other hand, it is difficult in commercial production to form the surface treatment only at the local position where the release agent layer is formed excluding the heat seal allowance, and in commercial production, it is a reality to treat the entire inner surface of the packaging material. there were.

An object of the present invention is a packaging material in which a layer of a release agent is provided with a heat-sealing allowance left, and the packaging can be satisfactorily heat-sealed with the heat-sealing allowance even if the surface activation treatment including the heat-sealing allowance is performed. It is to provide the material.

As a result of diligent studies to solve the above problems, the present inventors consist of a resin composition obtained by adding styrene-methyl (meth) acrylate-glycidyl methacrylate to polyethylene terephthalate, which was previously developed by the present inventors. Packaging materials with a low degree of crystallization (Patent No. 5593383, etc.) can adhere well to a release agent such as silicone when surface-activated, and exhibit good heat-sealing properties even when surface-activated. Was found, and the present invention was completed based on this finding.

That is, the present invention comprises a resin composition containing 0.1 to 3 parts by mass of a styrene-methyl acrylate-glycidyl methacrylate copolymer with respect to 100 parts by mass of polyethylene terephthalate, and has a crystallinity of 6 to 11. The present invention relates to a packaging material in which the surface of a 5% base material layer is activated and a release agent layer is laminated leaving a heat seal allowance.

INDUSTRIAL APPLICABILITY According to the present invention, PET having good heat resistance and transparency and no absorption of odor can be used as a packaging material for packaging an adhesive container, and the heat sealability is also good, so that the quality of the package is impaired. It is possible to provide packaging materials that can be stably stored without any problems and are easy to take out.

It is a partial cross-sectional view of the packaging material which is one Embodiment of this invention. It is the plan view. It is sectional drawing of the container formed by applying the packaging material which is one Embodiment of this invention.

The PET resin used in the resin composition of the present invention has an intrinsic viscosity of 0.6 to 0.8 dl, which is dissolved in a mixed solvent of phenol: tetrachloroethane = 1: 1 and measured with a Ubbelohde viscometer at 25 ° C. / G, more preferably 0.6 to 0.7 dl / g, still more preferably 0.6 to. It is 065 dl / g. If it is less than 0.6 dl / g, the melt viscosity becomes insufficient and film formation and molding tend to be unstable. On the other hand, when it exceeds 0.8 dl / g, the heat-sealing property is difficult to develop. The PET resin may be used alone or in combination of two or more.

As the PET resin used in the present invention, not only a virgin resin but also a recycled raw material recycled from a molded product may be used as long as the above conditions are satisfied.

The styrene-methyl (meth) acrylate-glycidyl methacrylate copolymer used in the present invention preferably has an epoxy value of 0.5 to 4.0 meq / g as measured by the method of ASTM-D1652. A more preferable epoxy value is 1.0 to 2.5 meq / g. If the epoxy value is less than 0.5 meq / g, sufficient melt viscosity cannot be maintained for film formation and molding, the crystallinity does not decrease to a desired range, and sufficient heat sealability is not exhibited. On the other hand, if it exceeds 4.0 meq / g, the recombination between PET molecules proceeds excessively, which causes problems such as the frequent occurrence of gel foreign substances during film formation and molding.

Examples of the styrene-methyl (meth) acrylate-glycidyl methacrylate copolymer are described in JP-A-2005-154690, for example, John Krill of BASF Japan Co., Ltd., Alfon of Toagosei Co., Ltd., etc. Is commercially available. The styrene-methyl (meth) acrylate-glycidyl methacrylate copolymer may be used alone or in combination of two or more.

When molding the PET base material layer of the present invention as a single film, it is preferable to add a molding aid. Molding aids include saturated and unsaturated fatty acids with about 10 to 20 carbon atoms such as stearic acid, lauric acid, lysinolic acid and octylic acid, alkali metals such as lithium, magnesium, calcium, barium and zinc, and alkaline earth. Metal salts with metals such as metals and zinc groups are preferable. Specific examples thereof include lithium stearate, magnesium stearate, calcium stearate, barium stearate, zinc stearate, calcium laurate, barium laurate, zinc laurate, barium ricinolate, zinc ricinolate, zinc octylate and the like. However, calcium stearate, which has excellent safety and hygiene, is most suitable as a packaging material for foods and medical products.

In addition to the above, a dispersion aid (which has the effect of moistening the surface of the particles of the molding aid and making the dispersion uniform) may be added to the resin composition of the present invention. The auxiliary agent is preferably a higher fatty acid ester having a polyfunctional epoxy group. Typical auxiliaries include epoxidized soybean oil and epoxidized flaxseed oil.

In addition, a softening agent can be added to applications that require flexibility. The softening material refers to a material that has an affinity for PET resin and is highly flexible. Specific examples thereof include ethylene- (meth) acrylic acid ester copolymers and copolymer polyesters. Preferable examples of the former include ethylene glycidyl methacrylate copolymer and ethylene-butyl acrylate. Suitable examples of the latter are polyesters with reduced crystallinity, such as terephthalic acid-ethylene glycol-1,4-cyclohexanedimethanol copolymers, polyester hard components and polyether soft components copolymers. And so on. These are commercially available and can be used.

The resin composition of the present invention may further contain other substances as long as the effects of the present invention are exhibited.

The blending ratio of the resin composition of the present invention is 0.1 to 3 parts by mass, preferably 0.5 to 2 parts by mass of the styrene-methyl acrylate-glycidyl methacrylate copolymer with respect to 100 parts by mass of the PET resin. 5 parts by mass, more preferably 1 to 2 parts by mass, 0.05 to 1.5 parts by mass when adding a molding aid, preferably 0.1 to 1 part by mass when adding a softening material. 3 to 20 parts by mass, preferably 5 to 10 parts by mass is suitable.

The base material layer of the present invention is obtained by forming or molding the above resin composition. The reason why the film-forming and molded products of the present invention have heat-sealing properties is unknown, but the carboxyl group at the terminal of the molecular chain and styrene- (meth) acrylic contained in a small amount in the PET resin due to heating during film formation and molding. The reaction in which the epoxy group of the methyl methacrylate-glycidyl methacrylate copolymer is bonded, the hydrolysis reaction of PET by a small amount of water contained in the PET resin, and the carboxyl group generated by the hydrolysis reaction and the epoxy group are present. It is considered that the bonding reaction and these reactions proceed at the same time, and the heat sealability is exhibited by increasing the polymer weight and lowering the degree of crystallization of PET suitable for film formation and molding. For this purpose, it is possible to use a film forming or molding apparatus equipped with a vent type melt extruder to heat and compress the resin composition in the melt extruder to perform film formation and molding while dehydrating and degassing. preferable.

The screw compression ratio of the extruder is preferably 1.8 to 3.5 from the viewpoint of dehydration and degassing efficiency. The compression ratio of the screw is expressed by the volume ratio of the groove portion per pitch of the screw supply portion and the measuring portion, and indicates the degree to which the molding material is compression-kneaded in the molten state. The melt extrusion temperature is preferably equal to or higher than the melting point of the PET resin, preferably 260 ° C to 350 ° C, and preferably 260 to 280 ° C from an economical point of view.

As the film formation of the film or sheet to be the base material layer, T-die film formation, inflation film formation, or the like can be used. Hereinafter, the case of inflation film formation will be described in detail. The inflation film formation may be either an upward air-cooled type or a downward water-cooled type, but an upward air-cooled type that can easily increase the blow ratio and the film forming speed is preferable. A suitable blow ratio is 1.1 to 4.0, preferably 1.5 to 3.0. If it is less than 1.1, the industrial production efficiency is lowered, while if it exceeds 4.0, excessive stretching orientation is applied to the film or sheet, which causes an inhibition of heat sealability. In inflation film formation, a film or sheet is expanded to form a film, and this expansion ratio is called the blow ratio.

Blow ratio = Cylindrical film diameter / Dice diameter = (Film width x 2 / π) / Dice diameter.

Further, in order to suppress an increase in crystallinity due to slow cooling, it is preferable to cool the film at a rapid and low temperature. The tubular film or sheet discharged from the die is primarily cooled by cooling air at 5 to 30 ° C, further flattened by a nip roll at around 60 ° C, and then both ends of the flat tubular shape are cut to form a piece of cloth. It is wound up and the film formation is completed.

Since the film or sheet formed on the film is laminated with a release agent layer in a subsequent process, one surface is subjected to a surface activation treatment. This surface activation treatment is performed by an oxidation treatment to generate a functional group such as a carbonyl group to enhance the adhesive force of the release agent, and is performed by a corona discharge treatment, a frame treatment, an ozone treatment, a plasma treatment, or the like. These treatment conditions may be normal treatment conditions, and for example, in the case of corona discharge, a preferable discharge treatment is 20 to 100 W / min / m ² .

In order for the release agent to be stably fixed on the surface treated by this surface activation treatment, the surface tension measured by the wet tension measuring method of JIS K6768 exceeds 40 dynes and is 80 dynes or less, preferably 45 dynes. It is desirable that the amount is 60 dyne or less.

The thickness of the obtained film or sheet is about 10 to 1000 μm, about 20 to 150 μm for a bag, usually about 30 to 100 μm, and about 500 to 1000 μm for a container, usually about 700 to 900 μm. ..

These films and sheets can be quickly sealed from the outside by low-temperature heat sealing, and have heat resistance that can be used for high-pressure steam sterilization at 145 ° C. or higher and microwave heating.

The substrate layer such as a film or sheet obtained by forming or molding the resin composition of the present invention or the container formed from the substrate layer has a melting enthalpy ΔH _m detected by differential scanning calorimetry (DSC) analysis. It is preferable that the crystallization degree χ _C obtained from the crystallization enthalpy ΔH _CL by the following formula (a) is 6 to 11.5%. A more preferable degree of crystallinity is 6.0 to 9.5%.

χc = 100 × (ΔH _m − ΔH _CL ) / 140 ・ ・ ・ (a)

As the release agent laminated on the base material layer, a silicone-based adhesion inhibitor or the like is used, and the thickness of the release agent layer is about 0.5 to 3 g / m ² , usually about 0.8 to 1.2 g / m ² . be.

The release agent layer is formed leaving a heat seal allowance and is provided on the surface in contact with the adhesive container. It is not necessary to provide a part that does not come into contact with the adhesive storage item.

The width of the heat seal allowance may be as long as the airtightness can be ensured by the heat seal, and varies depending on the weight of the stored items, etc., but is usually about 5 to 20 mm.

The technique of providing the peeling layer locally can be performed by using a printing technique such as gravure printing.

In the packaging material of the present invention, the base material layer may be a single layer, but various layers can be laminated on the surface opposite to the release agent layer depending on the use thereof. Examples include a gas barrier layer, a PET resin layer, a PBT resin layer, a polyamide resin layer, a polyolefin resin layer, and a polystyrene resin layer.

The packaging can be in various forms such as bags and containers depending on the application, and the bags are also heat-formed sheets and films such as 2-way, 3-way, 4-way seal bags, pillow bags, and gusset bags. It may have any form having a heat-sealed portion, such as a container made of a combination and a container made of a combination of heat-formed sheets.
Examples of the implementation mode of the packaging material of the present invention are shown in FIGS.

In the packaging material of FIG. 1, the upper surface of the base material layer 1 is subjected to corona discharge treatment to form a surface treatment layer 2, and a release agent layer 3 is provided on the surface treatment layer 3 in a grid pattern as shown in FIG. The surface treatment layer 2 between the agent layers 3 is exposed to form the heat seal allowance 4.

FIG. 3 shows the packaging material of FIG. 1 cut out for each section and processed into a long box-shaped container 5 by compressed air molding, and the release agent layer 3 is formed on the surface in contact with the adhesive paste-like container 6. positioned. A lid material 7 is heat-sealed on the upper edge of the flange-shaped container 5.

Regardless of the heat sealing means, a heat plate type, an impulse type, a high frequency type, an ultrasonic type, or the like can be used. The heat seal strength varies depending on the material to be filled and the required characteristics, but is usually about 10 to 40 N / 15 mm width, preferably about 15 to 35 N / 15 mm width.

The packaged object to be packaged with the packaging material of the present invention is not particularly limited, but a viscous material is suitable. The packaging material of the present invention can also be used as this release paper), paste products in the food, electrical materials and other industries (convenient to take out from the bag), and paste-like pet food (retort specifications are possible. ), Products in the kneading industry such as seasoned shavings (improved peelability makes it convenient to take out), urethane-based and olefin-based hot melts and adhesives, adhesive rolls (end face peeling sheet is no longer required, and can be stored as it is after use. It can be used for packaging such as). The packaging material of the present invention can maintain good heat-sealing strength even at a high temperature such as 150 ° C. to 180 ° C. when the object to be packed is filled. In this respect, it is particularly effective for packaging hot melt adhesives and the like.

Polyethylene terephthalate resin (MA-2101M manufactured by Unitica, density 1340 kg / m ³ , melting point 255 ° C., intrinsic viscosity 0.62 dl / g) 100 parts by mass of styrene-methyl (meth) acrylate-glycidyl methacrylate copolymer (weight average) This film obtained by molding a resin composition (HS-PETclear) containing 1.8 parts by mass of molecular weight 10800, epoxy value 1.8 meq / g, Tg 52 ° C. and 0.3 parts by mass of calcium stearate into a film having a thickness of 80 μm. The degree of crystallization of was 8.5%.

One side of this film was subjected to corona discharge treatment and cut to a width of 15 mm, and the two films were heat-sealed for 1 second at a heat sealing temperature of 150 ° C. and a load of 0.2 MPa in accordance with JISZ0238 by combining the corona discharge treated surfaces.
The obtained heat seal strength is shown in Table 1.

For comparison, PET-G (glycol-modified product) (manufactured by Tamapoli, "Hytron PG"), which is also a PET amorphous product, was also subjected to corona discharge treatment under the same conditions, and the treated surfaces were combined and heat-sealed. It is also shown in Table 1.

INDUSTRIAL APPLICABILITY According to the present invention, a packaging material for an adhesive container can be manufactured inexpensively and efficiently, so that it can be widely used as a packaging material for an adhesive container.

1 Base material layer 2 Surface treatment layer 3 Release agent layer 4 Heat seal allowance 5 Container 6 Container 7 Cover material

Claims (3)

A base material having a crystallinity of 6 to 11.5% and comprising 0.1 to 3 parts by mass of a styrene-methyl acrylate-glycidyl methacrylate copolymer with respect to 100 parts by mass of polyethylene terephthalate. A packaging material in which the surface of the layer is activated and a release agent layer is laminated on the activated surface leaving a heat seal allowance. The packaging material according to claim 1, wherein the release agent is silicone. The packaging material according to claim 1 or 2, wherein the surface activation treatment is a corona discharge treatment or a frame treatment.

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