JP2001054940A - Laminated film and packaging bag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated film prevented from curling at the time of heat seal processing and a packaging bag obtained by the heat seal processing of the laminated film and suitable for use in a filling and packaging machine. SOLUTION: In an unstretched laminated film consisting of at least an outermost layer (A) and an innermost layer (B) and obtained by a water quenching method, the outermost layer (A) is constituted of a polybutylene terephthalate homopolymer (a1) and/or a blend resin of a polybutylene terephthalate copolymer (a2) and polyester (a3) other than polybutylene terephthalate and the innermost layer (B) is constituted of a heat-sealable resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated film and a packaging bag, and more particularly, to a laminated film in which curling is prevented during heat sealing, and a heat-sealing process for the laminated film, which is used in a filling and packaging machine. The present invention relates to a packaging bag suitable for the use of the present invention.

[0002]

2. Description of the Related Art Conventionally, in various types of packaging using a filling and packaging machine, a packaging bag formed by heat-sealing an unstretched laminated film is used regardless of the food field or the non-food field. For example, in the case of food packaging requiring gas barrier properties such as ham and sausage, the unstretched laminated film is preferably made of polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) whose outermost layer is excellent in heat resistance. An unstretched laminated film having an inner layer made of a heat-sealing resin and an intermediate layer made of a gas barrier resin is used.

[0003]

However, the conventional packaging bag as described above has a disadvantage that the open end is curled, which causes a problem when used in a filling and packaging machine. In addition, the above curl is large in the stage of the unstretched laminated film before heat sealing to form a packaging bag, and therefore, in the production of a pillow packaging bag,
In the case of a center seal in which both ends of an unstretched laminated film are overlapped, poor sealing is caused.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a laminated film in which curling is prevented during heat sealing, a heat-sealing process for the laminated film, and a filling and packaging machine. An object of the present invention is to provide a packaging bag which is suitable for use in a device.

[0005]

As a result of extensive studies, the present inventor has found that the curl in the conventional unstretched laminated film (packaging bag) is caused by the type of resin used for the outermost layer. It has been found that curling during heat sealing can be prevented by using a non-stretched laminated film composed of a specific resin and obtained by a specific method.

The present invention has been completed based on the above findings, and a first gist thereof is to provide at least an outermost layer (A)
And an innermost layer (B), which is an unstretched laminated film obtained by a water-cooling quenching method, wherein the outermost layer (A) is
Polybutylene terephthalate homopolymer (a1) and / or
Or a polybutylene terephthalate copolymer (a2) and a polyester other than polybutylene terephthalate (a3)
Wherein the innermost layer (B) is formed of a heat-sealing resin.

A second gist of the present invention is to provide a packaging bag comprising at least an outermost layer (A) and an innermost layer (B) and heat-sealing an unstretched laminated film obtained by a water-cooling and quenching method. The outermost layer (A) is a blend resin of a polybutylene terephthalate homopolymer (a1) and / or a polybutylene terephthalate copolymer (a2) and a polyester (a3) other than polybutylene terephthalate. Wherein the innermost layer (B) is made of a heat-sealing resin.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a laminated film of the present invention will be described. The laminated film of the present invention has at least
It comprises an outermost layer (A) and an innermost layer (B).

One of the features of the present invention is that, as the constituent resin of the outermost layer (A), a polybutylene terephthalate homopolymer (a1) and / or a polybutylene terephthalate copolymer (a2) and a polyester other than polybutylene terephthalate are used. The point is that a blend resin with (a3) is used.
Hereinafter, polybutylene terephthalate is abbreviated as PBT.

As the PBT homopolymer (a1) and the PBT copolymer (a2), known polymers (resins) commonly used in the field of packaging films can be used.
Examples of the copolymer component of the copolymer (a2) include the following components.

That is, as the dicarboxylic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid,
Adipic acid, sebacic acid, oxycarboxylic acid (for example,
P-oxybenzoic acid, etc.), and the glycol component includes ethylene glycol and diethylene glycol.
Propylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol, polyethylene oxide glycol, polypropylene oxide glycol, polytetramethylene oxide glycol and the like. These dicarboxylic acid components and glycol components may be used in combination of two or more. The ratio of the PBT unit derived from terephthalic acid and butylene glycol is usually 70 to 99 mol%, preferably 85 to 99 mol%, and the remainder is a unit derived from the above-mentioned copolymer component.

In the present invention, the PBT copolymer (a2)
Polytetramethylene oxide glycol is recommended as a copolymer component of the above, and its number average molecular weight is preferably in the range of 300 to 6000, and more preferably in the range of 500 to 2,000.

The polyester (a3) other than PBT is not particularly limited, but may be polyethylene terephthalate (PET) and / or polyethylene naphthalate (PE).
N) is recommended. As PET and PEN, known polymers (resins) commonly used in the field of packaging films can be used.

In the blend resin constituting the outermost layer (A), the proportion of the PBT homopolymer (a1) and / or the PBT copolymer (a2) and the polyester (a3) other than PBT is determined by the ratio of the PBT in the blend resin. The concentration of the other polyester (a3) is usually 5 to 95% by weight, preferably 30 to 90% by weight.

The outermost layer (A) preferably contains an anti-blocking agent composed of organic fine particles or inorganic fine particles from the viewpoint of blocking resistance during storage of the packaging bags in a laminated state.

Examples of the antiblocking agent comprising the above-mentioned organic fine particles include polystyrene, polyethylene, polyamide, polyester, polyacrylate, polymethacrylate, epoxy resin, polyvinyl acetate, polyvinyl chloride and the like. Fine particles which may contain a crosslinking agent composed of a polymer or the like are included. On the other hand, examples of the antiblocking agent composed of the above-mentioned inorganic fine particles include talc, kaolin, silica, calcium carbonate, glass powder and the like.

The average particle size of each of the above anti-blocking agents is usually about 1 to 10 μm.
It is usually from 100 to 10,000 ppm, preferably from 1,000 to 5,000 ppm, based on the resin. In the present invention, an anti-blocking agent comprising organic fine particles is recommended, and particularly, fine particles of polyacrylate or polymethacrylate are preferably used.

The innermost layer (B) is made of a heat-sealing resin, and specific examples thereof include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), and polypropylene (P).
P), ethylene-vinyl acetate copolymer (EVA), ethylene-methacrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer Polymer (EAA), ethylene-ethyl methacrylate copolymer (EMAA), adhesive polyethylene,
Examples include ionomer resin, saponified EVA, linear low-density polyethylene (L-LDPE), or a copolymer thereof. Among these, linear low-density polyethylene (L-
LDPE) is preferred.

Linear low density polyethylene (L-LDPE)
Is a copolymer of ethylene and an α-olefin having 3 to 13 carbon atoms (ethylene content: 86 to 99.5 mol%), and has a low and medium density different from LDPE produced by a conventional high pressure method. It is polyethylene. High pressure LDPE and LL
The structural difference from DPE is that the former has a multi-branched molecular structure and the latter has a linear molecular structure.
In the production of LLDPE, α copolymerized with ethylene
-Examples of the olefin include butene-1, pentene-1, hexene-1, octene-1, and 4-methylpentene-1. These copolymerizations are carried out by a low to medium pressure method using a so-called Ziegler-Natta type catalyst or metallocene catalyst.

If the specific examples of the above LLDPE are represented by trade names, Unipol (UCC), Dourex (Dow Chemical), Screa (DuPont Canada), Marlex (Philips), Neozex and Ultrazex (Mitsui Petrochemical) ), Nisseki Linilex (Nippon Petrochemical), Stamilex (DSM) and the like.

A gas barrier resin layer (C) is disposed between the outermost layer (A) and the innermost layer (B) as required, for example, for food packaging requiring gas barrier properties. Is done. Examples of the constituent resin of the gas barrier resin layer (C) include polyamide (PA), saponified ethylene-vinyl acetate copolymer (EVOH), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polycarbonate (PC). No. Among these, polyamide (PA) or saponified ethylene-vinyl acetate copolymer (EVOH) is preferred, and polyamide (PA) is particularly preferred.

In the present invention, a polyamide obtained by polycondensation of (1) a lactam having three or more ring members, (2) a polymerizable ω-amino acid, and (3) a polyamide material of diamine and dicarboxylic acid is used. Can be done.

Examples of the lactam having three or more rings include ε-caprolactam, enantholactam, α-pyrrolidone, α-piperidone and the like.
Specific examples of amino acids include 6-aminohexanoic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, and 9-aminononanoic acid.

Specific examples of the diamine include hexamethylene diamine, nonamethylene diamine, undecamethylene diamine, dodecamethylene diamine, and meta-xylylene diamine. Examples of the dicarboxylic acid include terephthalic acid. , Isophthalic acid, adipic acid, sebacic acid, dodecane dibasic acid, glutaric acid and the like.

Specific examples of the polyamide used in the present invention include nylon 4, 6, 7, 8, 11, 12, 6.6,
6 ・ 10, 6 ・ 11, 6 ・ 12, 6T, 6/6 ・ 6, 6
/ 12, 6 / 6T, 6I / 6T and the like.

In a preferred embodiment of the present invention, an adhesive resin layer is disposed between the above-mentioned layers. The adhesive resin layer is usually composed of a modified polyolefin resin (APO). Such APO is produced by copolymerizing and / or graft-polymerizing an α, β unsaturated carboxylic acid or a derivative thereof on a polyolefin resin containing an ethylene component and / or a propylene component as a main component.

Examples of the above polyolefin resin include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene- Ethyl acrylic acid copolymer, ethylene-
And sodium acrylate copolymer.

Examples of the α, β-unsaturated carboxylic acid or its derivative to be copolymerized include acrylic acid, methacrylic acid, methyl methacrylic acid, sodium acrylate, zinc acrylate, vinyl acetate, glycidyl methacrylate and the like. , Within the range of 40 mol% in the molecular chain. Examples of the copolymer-modified polyolefin resin include an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene-ethyl acrylic acid copolymer, and an ethylene-sodium acrylate copolymer.

The above-mentioned grafted α, β-unsaturated carboxylic acid or a derivative thereof includes, for example, acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, fumaric acid, acid anhydrides of these, or acids thereof. And the like. Among these modifying compounds, maleic anhydride is particularly preferred. The amount of grafting is selected from the range of 0.01 to 25% by weight, preferably 0.05 to 1.5% by weight, based on the polyolefin resin.

The grafting reaction is carried out according to a conventional method, usually by melt-mixing a polyolefin resin and an α, β-unsaturated carboxylic acid or a derivative thereof at a resin temperature of 150 to 300 ° C. At the time of the graft reaction, 0.001-0.05% by weight of an organic peroxide such as α, α′-bis-t-butylperoxy-p-diisopropylbenzene is blended in order to carry out the reaction efficiently. Is good.

In the above non-laminated film, the outermost layer (A) has a thickness of usually 5 to 100 μm, preferably 10 to 100 μm.
７０70 μm, the thickness of the innermost layer (C) is usually 20-100
μm, preferably 30 to 70 μm, and the thickness of the gas barrier resin layer (B) is usually 5 to 50 μm, preferably 10 to 10 μm.
It is 30 μm. In a preferred embodiment, the thickness of the adhesive resin layer disposed between the layers is usually 2 to 30 μm.
m, preferably 5 to 15 μm.

Another feature of the present invention resides in the use of an unstretched laminated film obtained by a water cooling and quenching method. That is, it is necessary to employ a water-cooled quenching method instead of the air-cooling method as the co-extrusion molding method of the unstretched laminated film. Here, the water-cooled quenching method generally refers to a method in which a film extruded from a die is guided to a water tank arranged below the die, cooled, and then wound. Specifically, usually, a water tank provided with a size ring therein is arranged below the annular die, and a facility is used in which an inner plate and a winding roll are sequentially arranged below the water tank. Then, a plurality of types of raw resin are co-extruded from an annular die so that stretching does not substantially occur, and the resin is cooled by passing between size rings, and then the cylindrical body of the laminated film is wound through an inner plate. It is supplied to a roll, folded, and wound up as a double film.

When the air cooling method is used instead of the water cooling and quenching method, the effects of the present invention cannot be achieved as shown in the comparative examples described later. Here, the air cooling method generally refers to a method in which a film extruded from a die is guided above the die, cooled by blowing cooling air, and then wound. Specifically, usually, an air ring that blows cooling air is arranged above the annular die, and a facility is used in which an inner plate and a winding roll are sequentially arranged above the air ring, and A plurality of types of raw resin are co-extruded from an annular die so that stretching does not substantially occur, and the resin is passed through an air ring and cooled, and then the laminated film cylinder is supplied to a take-up roll through an inner plate. Fold it up and wind it up as a double film.

The laminated film of the present invention obtained as described above is a substantially unstretched film, and in a preferred embodiment, the heat shrinkage in the length direction (MD) and the width direction (TD) (JIS K 6734). ) Is 5% or less.

The laminated film of the present invention is preferably used for various types of packaging bags since curling during heat sealing is prevented. For example, in the case of manufacturing a pillow packaging bag, poor sealing is not caused in a center seal performed by overlapping both ends of an unstretched laminated film.

Next, the packaging bag of the present invention will be described.
The packaging bag of the present invention is manufactured by heat sealing the end of the cylindrical body of the laminated film obtained as described above. Heat sealing is a known technique usually performed as gusset processing, and a preferred embodiment thereof is as follows.

That is, this is a processing method in which the end of the cylindrical body is folded and sealed. In the case of ordinary gusset processing, the end of the cylindrical body is formed in a rectangular shape, and two opposite sides thereof are substantially centered. Then, the other two sides are overlapped with each other and heat-sealed with a linear heat-sealing bar along the end.

The packaging bag of the present invention is used for packaging industrial products such as electronic parts and foods such as ham and sausage.
Particularly, it is suitably used for food packaging. And since the open end of a container (gusset bag) does not curl, there is no trouble at the time of material filling by a filling and packaging machine.

[0039]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention.

Examples 1-4 The outermost layer blend resins (B) 1-1 listed in Table 1 below
And B (8 μm) / APO (6) by a water-cooled quenching method (downward water-cooling molding method) using a 5-layer co-extrusion annular die.
μm) / NY: Nylon 6 (16 μm) / APO (6 μm)
m) / L-LDPE (44 μm) to produce a laminated film cylinder having a layer structure. At this time, 2,000 fine particles of polymethyl methacrylate (PMMA) having an average particle size of
0 ppm was blended and used. The extrusion temperature was 240 ° C, the water cooling temperature was 28 ° C, and the winding speed was 15 m / min. And
The obtained cylindrical body was slit to a predetermined length, and gusset processing was performed on one end of the cylindrical body along with a linear heat seal along the end to obtain a gusset bag.

Further, a 100 mm square sheet-like test piece (laminated film) was sampled from the above-mentioned cylindrical body, and was subjected to a temperature of 23 ° C.
The curl property after being left in a room with a humidity of 50% for 24 hours was evaluated in the following manner. That is, the test piece is placed on a horizontal table, and when it becomes cylindrical, its diameter (mm) is measured.
When stopping at the bending stage, the bending height (mm) is measured. On the other hand, the presence or absence of curling at the open end of the gusset bag obtained above was also visually observed. Table 2 shows the results.
“Inside” in the table means the innermost layer (heat-sealing resin) side.

[0042]

[Table 1]

Comparative Examples 1 to 3 Except that the type of the resin in the outermost layer was changed as shown in Table 2,
A laminated film and a gusset bag were obtained in the same manner as in Example 1, and their curling properties were evaluated. The results are shown in Table 2. The raw material resin of the outermost layer was mixed with 2000 ppm of PMMA fine particles having an average particle diameter of 6 μm as in Example 1.

Comparative Examples 4 to 7 Laminated films and gusset bags were obtained in the same manner as in Example 1 except that the air-cooling method was used instead of the water-cooling and quenching method, and their curling properties were evaluated. The results are shown in Table 2.

[0045]

[Table 2]

[0046]

According to the present invention described above, a laminated film in which curling is prevented during heat sealing and a packaging bag obtained by heat sealing the laminated film and suitable for use in a filling and packaging machine. Is provided, and the industrial value of the present invention is great.

 ────────────────────────────────────────────────── ─── Continued on front page F term (reference) 3E064 AA01 BA27 BA28 BA29 BA30 BA54 BA55 BB03 BC18 EA30 4F100 AK01B AK04 AK06 AK07 AK25H AK41A AK42A AK42J AK48 AL01A AL05A AL07 AR00C BA02 BA03 BA04 BA05 BA07 BA01 BA10 JA07A JD02C JL04 JL12B YY00A

Claims (10)

[Claims] 1. At least an outermost layer (A) and an innermost layer (B)
Wherein the outermost layer (A) comprises a polybutylene terephthalate homopolymer (a1) and / or a polybutylene terephthalate copolymer (a2). And a polyester (a3) other than polybutylene terephthalate, wherein the innermost layer (B) is made of a heat-sealing resin. 2. The copolymer (a2) having a polybutylene terephthalate unit ratio of 70 to 99 mol%.
3. The laminated film according to item 1. 3. The laminated film according to claim 1, wherein the copolymer component unit of the copolymer (a2) is a polytetramethylene oxide glycol having a number average molecular weight of 300 to 6000. 4. The laminated film according to claim 1, wherein the polyester (a3) is polyethylene terephthalate and / or polyethylene naphthalate. 5. The laminated film according to claim 1, wherein the concentration of the polyester (a3) other than polybutylene terephthalate in the blend resin constituting the outermost layer (A) is 5 to 95% by weight. 6. The laminated film according to claim 1, wherein the resin layer (A) contains an anti-blocking agent. 7. A gas barrier resin layer (C) disposed between an outermost layer (A) and an innermost layer (B).
The laminated film according to any one of the above. 8. The laminated film according to claim 1, which is for packaging bags. 9. At least an outermost layer (A) and an innermost layer (B)
Wherein the outermost layer (A) is a polybutylene terephthalate homopolymer (a1) and / or a polybutylene terephthalate homopolymer (a1). It is composed of a blend resin of a butylene terephthalate copolymer (a2) and a polyester (a3) other than polybutylene terephthalate, and the innermost layer (B) is composed of a heat sealing resin. Packaging bag. 10. The packaging bag according to claim 9, which is for food packaging.