JP2003019773A - Packaging film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging film wherein a sufficient tear ability is developed even when a sealant layer is of a monolayer type, without substantially impairing the inherent nature of metallocene PE such as transparency, low temperature heat sealability or anti-blocking by contriving the composition of the sealant layer. SOLUTION: This packaging film is of the laminated film (1) structural type that the sealant layer (12) is formed on at least one side of a base film layer (11). The sealant layer (12) is constituted of a composition (AB) layer which shows the weight ratio of (85:15) to (40:60) between an ethylene/alpha olefin copolymer (A) manufactured by a single site catalyst and an amorphous cycloolefin polymer (B).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a base film layer /
A packaging film having a layer structure of a sealant layer, more specifically, having excellent tearability and having a necessary sealing strength,
The present invention also relates to a packaging film having good blocking resistance.

[0002]

2. Description of the Related Art (a) An ethylene / α-olefin copolymer (hereinafter sometimes abbreviated as "metallocene PE") produced using a single-site catalyst (typically a metallocene catalyst) has a film strength. Since it has a large size and good optical properties such as transparency, low temperature sealing properties, and antiblocking properties, its use has been expanding in recent years as a sealant layer for packaging materials.

(B) In order to improve the easy tearability when used as a packaging material such as a packaging bag, Japanese Patent Application Laid-Open No. 10-24539 filed by the present applicant represents a biaxially stretched synthetic resin. A low density polyethylene (LDPE) layer or a linear low density polyethylene (L
A highly tearable packaging material in which a metallocene-catalyzed low-density polyethylene layer is formed via an LDPE layer is shown.

(C) Japanese Patent Laid-Open No. 2000-326459 describes: -A layer containing a linear low-density polyethylene having a long period of 275 Å or less as measured by a small angle X-ray scattering method (or the linear low-density polyethylene). A layer of a composition containing a and an alicyclic polymer) X, a layer Y of an alicyclic polymer, and a layer Z of a thermoplastic resin are laminated at least, and the layer X is a layer. "Z / X / Y", "Z / X / Y / X / sandwiched between Y and layer Z"
Films having layer configurations such as "Z" are shown. The layer structure of the examples is "polypropylene layer / linear low-density polyethylene (or composition of the same and hydrogenated ring-opening polymer) layer / hydrogenated ring-opening polymer layer".

(D) Japanese Patent Laid-Open No. 2000-334890 discloses that
On at least one side of the layer consisting of an alicyclic structure-containing polymer,
A packaging film is shown having layers of other thermoplastics. A typical example of the alicyclic structure-containing polymer is a hydrogenated product of a norbornene ring-opening polymer. Examples of other thermoplastic resins include amorphous resins such as polyvinyl chloride, polystyrene, high-impact polystyrene, and polyphenylene ether; polyolefin-based crystalline resins such as polyethylene-based crystalline resins and polypropylene-based crystalline resins; polyester-based crystals. It is a crystalline resin such as a crystalline resin and a polyamide-based crystalline resin.

[0006]

In the above method (a), since the sealant layer of the metallocene resin has a large tear strength of the sealant layer itself, its use is promoted in applications requiring easy tearability. Not at all.

[0007] The packaging material of the above (b) has a layer structure of "base film / LDPE (or LLDPE) / metallocene low density polyethylene layer" so that the sealant layer can be easily torn. Since there are two layers, there is a disadvantage that the formation of the sealant layer becomes complicated.

The film of the above (c) is a linear low density film for improving the adhesive strength between the Y layer and the Z layer between the alicyclic polymer layer Y and the thermoplastic resin layer Z. A polyethylene layer (or a layer of a composition of linear low-density polyethylene and an alicyclic polymer) X is interposed. However, since this film is supposed to be stretched, transparency, flexibility and adhesion to other objects are taken into consideration, and there is no description regarding sealing properties, Although there is no description of various uses, it is presumed to be a film suitable as a wrap film or a stretch film. Even if this is not the case, the use of this film as a sealant layer has the disadvantage that the formation of the sealant layer becomes complicated because the layer constitution is at least three layers.

The above-mentioned packaging film (d) is also easy to tear,
It is described that the film is excellent in properties such as transparency, self-adhesion and tensile elongation, and is particularly suitable for a packaging film such as a wrap film and a stretch film.
And, even if it is not preferable, when this film is used as a sealant layer, there is a disadvantage that the formation of the sealant layer becomes complicated because the layer constitution is at least two layers.

The present invention has been made to solve the above-mentioned problems of the prior art, and by devising the composition of the sealant layer, the transparency and the low temperature heat seal originally possessed by metallocene PE are improved. The purpose of the present invention is to provide a packaging film capable of exhibiting sufficient easy tearability even in a single-layer sealant layer without substantially impairing properties such as anti-blocking property and anti-blocking property. .

[0011]

The packaging film of the present invention is a laminated film (1) having a constitution in which a sealant layer (12) is provided on at least one surface of a base film layer (11), The sealant layer (12) has a weight ratio of the ethylene / α-olefin copolymer (A) produced by a single site catalyst and the amorphous cycloolefin polymer (B) of 85: 1.
It is characterized by comprising a layer of the composition (AB) of 5 to 40:60.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

<Ethylene / α-olefin copolymer (A)
In the present invention, as the ethylene / α-olefin copolymer (A), a copolymer produced by copolymerizing ethylene and α-olefin in the presence of a single site catalyst is used.

Here, the α-olefin has 4 carbon atoms.
~ 8, such as butene-1, penten-
1, hexene-1, 4-methylpentene-1, heptene-1, octene-1 and the like. The content of α-olefin in the copolymer (A) is often 1 to 5 mol%, for example.

The single-site catalyst means a catalyst in which cyclopentadiene having a single active site is arranged (for example, a zirconium metallocene catalyst), and a multi-site having a plurality of active sites such as Ziegler catalyst used for producing low density polyethylene. It is to be contrasted with a catalyst.

More specifically, the single-site catalyst includes: metallocene, that is, two substituted or unsubstituted cyclopentadienyl rings and various transition metals (periodic table IVb.
Group, Vb group or VIb group metal, especially titanium or zirconium), a transition metal component composed of a complex, and an organoaluminum component (in particular, aluminoxane), which is a general term for the catalyst, It is represented by a formula. (Cp) ₂ MR ₂ (In the formula, Cp is a substituted or unsubstituted cyclopentadienyl ring, M is a transition metal, and R is a halogen atom or an alkyl group.)

Aluminoxane is obtained by reacting an organoaluminum compound with water, and includes linear aluminoxane and cyclic aluminoxane. These aluminoxanes are used alone or in combination with other organoaluminums.

Copolymerization of ethylene and α-olefin using a single site catalyst is carried out by polymerization in a liquid monomer or in a gas phase method in the presence of a single site catalyst in an organic solvent.

The above ethylene / α-olefin copolymer
The density of (A) is 880-920kg / m ³ Preferred to be
Good More preferable range is 890 to 915 kg / m³ And
It Density is 880kg / m³ If it is less than the resin composition
Mechanical strength tends to decrease, while the density
920kg / m³ If it exceeds the
Poor low temperature sealing and flexibility, and poor pinhole resistance
Tend to do.

Further, the melt flow rate (MFR, JIS K 7210 of the above ethylene / α-olefin copolymer (A) is used.
In accordance with, measured at 190 ℃, load 2160g) is 0.1
It is preferably in the range of up to 20 g / 10 min. This is because when the MFR is too small, the film-forming property of the sealant layer tends to deteriorate, while when the MFR is too large, the physical properties of the sealant tend to deteriorate.

Since the ethylene / α-olefin copolymer (A) is produced by using a single site catalyst, it is characterized in that the molecular weight distribution Mw / Mn becomes narrow. At this time, Mw / Mn is preferably 1 to 2.5, particularly preferably 1 to 2. When the molecular weight distribution is narrowed in this way, the proportion of low molecular weight portions is reduced, the film becomes less sticky, and the antiblocking property is improved.

<Amorphous cycloolefin polymer (B)> The amorphous cycloolefin polymer (B) is a polymer having an alicyclic structure in the main chain synthesized from cycloolefins as a monomer, Typically, highly reactive norbornenes are used as cycloolefins. Polymer
(B) is a polymer of norbornene-based monomer or a copolymer of norbornene-based monomer and a vinyl-based monomer copolymerizable therewith, and the norbornene ring-opening polymer is hydrogenated. It is particularly preferable that

The above amorphous cycloolefin polymer (B)
The glass transition point Tg of is preferably 100 ° C. or lower, and particularly preferably 90 ° C. or lower. If the Tg exceeds 100 ° C, the amorphous cycloolefin polymer (B) may not be softened even if the ethylene / α-olefin copolymer (A) is melted during the sealing operation, resulting in poor sealing suitability. There is. Further, the processing temperature of the resin composition (AB) of the present invention (about 180 to 240 ° C. in the case of film formation, 2 in the case of extrusion lamination).
It is difficult to process at about 50 to 320 ° C., and fish eyes or the like may occur, which may cause a problem in appearance. On the other hand, the lower limit of the glass transition point Tg is about 50 ° C., and if Tg is lower than that, it becomes too soft and the easy-open property may be impaired.

<Composition (AB)> The composition (AB) of the present invention is a composition of the above ethylene / α-olefin copolymer (A) and the above amorphous cycloolefin polymer (B). Consists of.
The mixing ratio of the copolymer (A) and the polymer (B) at this time is set to 85:15 to 40:60 by weight.
When the proportion of copolymer (A) is higher than this range (polymer
When the proportion of (B) is less than this range)
When the bag using (AB) as the sealant layer has poor tearability, on the other hand, when the proportion of the copolymer (A) is less than this range (when the proportion of the polymer (B) is more than this range), There is a high possibility that the heat sealability will be deteriorated or the flexibility will be deteriorated to cause bag breakage.

In the composition (AB), additives (antistatic agents, antioxidants, ultraviolet absorbers, light stabilizers) that are added as necessary during film formation are used as long as the heat sealability is not impaired. , Colorants, lubricants, antifogging agents, etc.).

<Laminated Film (1), Bag Making> FIG. 1 is a front view showing an example of a bag made from the laminated film (1) of the present invention. FIG. 2 is an XX section view of the bag of FIG.

The packaging film of the present invention, that is, the laminated film (1) comprises a base film layer (11) / sealant layer (12).
Layer structure or sealant layer (12) / substrate film layer
It has a layer structure of (11) / sealant layer (12).

Examples of the substrate film layer (11) include film layers of polypropylene, polyester, polyamide and the like, and these are preferably uniaxially or biaxially stretched films (particularly biaxially stretched films). These general-purpose films may be laminated in a plurality of layers, and if necessary, a barrier layer such as oxygen or water vapor, for example, an inorganic layer such as metal (aluminum or the like), silica, or alumina, polyvinylidene chloride, ethylene. -A layer that imparts a function, such as a resin layer such as a vinyl alcohol copolymer, may be laminated.

In the present invention, the above-mentioned ethylene / α is used as the sealant layer (12) of the laminated film (1).
-A layer of the above composition (AB) comprising the olefin copolymer (A) and the above amorphous cycloolefin polymer (B) is used.

The sealant layer (12) can be produced by once producing a film from the composition (AB) and then used for lamination with the substrate film (11), and the composition (AB Can be melt extrusion coated to form the sealant layer (12).

Since the laminated film (1) (packaging film) is obtained in this manner, the bag is formed by facing the sealant layer (12) side of the laminated film (1) and heat-sealing necessary parts. It can be manufactured. At this time, bag-making may be performed using two laminated films (1), or one laminated film (1) may be half-folded and half-cut to perform bag-making. When making a bag, make a bottom gusset or side gusset bag by folding the laminated film (1) into a W shape or sandwiching a tape-like film from the side that becomes the bottom side or the side side in a V shape. May be.

If necessary, a fitting type wire fastener (4) is preliminarily attached to a portion of the laminated film (1) on the opening side of the bag.
It is possible to make the opened bag mouth re-sealable by providing.

In order to facilitate the tearing of the bag, it is usual to provide a notch (3) at the tear start position of the heat-sealing portion (2) of the bag after bag making.

<Use> The packaging container such as a bag obtained from the above laminated film (1) is useful for various uses such as food packaging and pharmaceutical packaging. In particular, since the following characteristics originally possessed by the copolymer (A) can be utilized in the sealant layer (12) without being impaired, it is suitable for liquid sachet packaging. -The sealing start temperature is low and the sealing condition range is wide. -Has excellent hot tack properties (hot peeling = difficulty in peeling from the molten state during sealing to solidification by cooling). -Excellent impact strength and pressure resistance at low temperatures.・ Good sealing property with liquid.・ Since the low molecular weight part of the copolymer (A) is small, it does not become sticky and has excellent blocking resistance.Therefore, a powder treatment that is normally performed (spraying powder such as corn starch to prevent blocking) is required. It can be omitted. Therefore, it is possible to use the powder-treated packaging containers such as silicon wafers, photographic fixing liquids, and toner packaging for undesired applications. When packaging pharmaceuticals and foods, improve safety and hygiene and packaging containers. Improves the production environment and the work environment for filling and packaging.

<Action> When the above-mentioned ethylene / α-olefin copolymer (A) only layer is used as a sealant layer, the sealant layer itself has a large tear strength, and therefore, an application which requires easy tearability in a packaging bag. Not suitable for.

On the other hand, when the above-mentioned layer of only the amorphous cycloolefin polymer (B) is used as the sealant layer, although the sealant layers are apparently adhered to each other, the heat seal strength is insufficient, so that the practicality is high. Come to lack.

In accordance with the present invention, however, the composition (A
When the sealant layer (12) is formed from B), the amorphous cycloolefin polymer (B) is mixed with the ethylene / α-olefin copolymer (A) having a low melting point. High strength heat sealing is possible without being affected. This mechanism is not always clear, but when heat-sealing using the sealant layer (12) of the laminated film (1), the polymer (B) is softened between the sealant layers (12) facing each other even at a low heat-sealing temperature. Because of the copolymer
The copolymer (A) in one sealant layer (12) becomes a polymer due to the molecular motion due to heat when (A) is melted during heat sealing.
(B) The other sealant layer without being disturbed by the molecular mass
It is considered that it does not enter the (12), and as a result, the interface between the sealant layers (12) and (12) disappears, which does not cause an adverse effect in sealing.

The copolymer (A) and the polymer (B) have low compatibility, and the resin composition (AB) is used as a sealant layer.
In the state formed in (12), the polymer (B) in the copolymer (A)
Since it exists in the state of sea island, it is considered that the tearability is lowered, that is, the tearability can be improved while maintaining the low temperature heat sealability of the copolymer (A).

[0039]

EXAMPLES The present invention will be further described with reference to examples. Hereinafter, “parts” means parts by weight. MFR is the melt flow index.

<Preparation or Preparation of Film for Sealant Layer (12)> Example 1 As an example of the ethylene / α-olefin copolymer (A) produced with a single-site catalyst, ethylene copolymer manufactured by Mitsui Chemicals, Inc. A polymer "Evolew SP0540" was prepared. The characteristic values of this ethylene copolymer are as follows.・ Density: 905kg / m ³・ MFR: 4g / 10min (190 ℃, 2160g) ・ Melting point: 93 ℃ ・ Comonomer: Hexene-1

As the amorphous cycloolefin polymer (B), a norbornene ring-opening polymer hydrogenated product "ZEONOR750R" manufactured by Nippon Zeon Co., Ltd. was prepared. The characteristic values of this amorphous cycloolefin polymer are as follows.・ Density: 1000kg / m ³・ MFR: 24g / 10min (measured at 280 ℃) ・ Glass transition point Tg: 70 ℃

The above ethylene / α-olefin copolymer
(A) 80 parts and amorphous cycloolefin polymer (B) 20 parts were dry-blended and then fed to an inflation molding machine to perform inflation film formation at a cylinder setting temperature of 200 ° C. and a die setting temperature of 180 ° C. A film having a thickness of 50 μm was obtained.

Example 2 A blending ratio of the ethylene / α-olefin copolymer (A) and the amorphous cycloolefin polymer (B) was 50:50 by weight.
Example 1 was repeated except that the value was 50 (however, in this Example 2, the die set temperature in the inflation molding machine was 190 ° C.) to obtain a film having a thickness of 50 μm.

Comparative Example 1 As the ethylene / α-olefin copolymer (A), "SP0540" manufactured by Mitsui Chemicals, Inc. was used alone and supplied to an inflation molding machine to set the cylinder temperature to 200.
Inflation film formation at ℃, die set temperature 180 ℃,
A film having a thickness of 50 μm was obtained.

Comparative Example 2 The blending ratio of the ethylene / α-olefin copolymer (A) and the amorphous cycloolefin polymer (B) was 90: by weight.
Example 1 was repeated except that the number was changed to 10 to obtain a film having a thickness of 50 μm.

Comparative Example 3 Amorphous cycloolefin polymer (B) in Example 1
("ZEONOR750R" manufactured by Nippon Zeon Co., Ltd.)
The T-die film having a thickness of 50 μm was provided by ZEON CORPORATION.

<Physical property evaluation method> The physical properties of the films for the sealant layer (12) of Examples 1 to 2 and Comparative Examples 1 to 3 were measured or evaluated as follows. -For tear strength, Elmendorf tear load was measured according to JIS K 7128. -Regarding tensile properties, the strength at break and the elongation at break were measured according to JIS K 7127.・ The sealing characteristics are as follows: sealing pressure 0.2 MPa, sealing time 1 second,
Seal bar width 10 mm, peeling speed 300 mm / min, test piece 1
The heat seal strength was measured under the condition of a width of 5 mm. -For linear cutability, after notching (3) on the film, it was torn with a finger and it was examined whether the tear line was a straight line.

<Results> The results are shown in Table 1. In the table, MD means the machine direction and TD means the transverse direction. 3 to 5 show the relationship between the blend ratio and the measured values of Elmendorf tear load, strength at break, and elongation at break.

[0049]

[Table 1]      Comparative Example 1 Comparative Example 2 Example 1 Example 2 Comparative Example 3   (A) :( B) Weight ratio 100: 0 90:10 80:20 50:50 0: 100   Elmendorf   Tear load (N) MD 6.6 5.1 2.8 0.4 0.9   TD 6.6 5.9 1.8 0.3 1.0   Breaking strength (MPa)                 MD 49 18 22 25 52   TD 48 22 21 23 51   Elongation at break (%)                 MD 600 380 248 130 14   TD 600 463 413 197 12   Heat seal strength   (N / 15mm) 100 ℃-9.2 9.7 7.1 0             110 ° C 7.5 10^#       10 11 0             120 ° C 7.8 9.4^#     11 12 0             140 ° C 8.6 9.5^#     11 12 11   160 ° C 9.3 11 ^# 12 ^# 13 ^# 12   Linear cutability MD-× ○ ○ ×   TD-× ○ ○ ×                           (Note) The # mark is cut off at the time of sealing.

<Analysis> From Table 1, in Examples 1 and 2, the tear strength was small in both MD and TD,
Therefore, the sealant layer (1
It can be seen that the bag having 2) can be easily torn and opened with a finger while ensuring the necessary sealing strength.

From the comparison between Example 1 and Example 2,
By adjusting the blend ratio of ethylene / α-olefin copolymer (A) and amorphous cycloolefin polymer (B) to an appropriate ratio, the tear strength can be adjusted while ensuring the required seal strength. You can see that you can.

On the other hand, in Comparative Example 1, since the sealant layer (12) was composed of a film of ethylene / α-olefin copolymer (A) only, the tear strength was improved in both MD and TD. Has a large sealant layer (12)
It is difficult to tear and open the bag having the tongue with a finger. Also, the heat seal strength is smaller than that of the example.

In Comparative Example 2, the ethylene / α-olefin copolymer (A) and the amorphous cycloolefin polymer were used.
The ratio of the latter in (B) is too small, so the tear strength is too high. And the tear line is also not straight.

In Comparative Example 3, since the sealant layer (12) was composed of the film of the amorphous cycloolefin polymer (B) only, the heat seal strength was considerably weakened and a sufficient heat seal as a bag was obtained. There is a disadvantage in that it is not possible or because there is no flexibility, there is a high risk that a bag will break or a pinhole will occur. And the tear line is also not straight.

Although the present invention has been described with reference to the embodiments, the present invention is not limited to these and various modifications can be made without departing from the spirit of the present invention. For example, the sealant layer (12) may be laminated not only on one side of the base film layer (11) but also on both sides, and these sealant layers (12) may be the same resin or different resins. . Further, the packaging container to which the packaging film of the present invention is applied is not limited to a packaging bag, and can also be used as a film for a lid material for trays, cups, toner cartridges and the like.

[0056]

In the present invention, since the composition of the sealant layer (12) is specially devised, the ethylene / α-olefin copolymer (A) produced by a single site catalyst is used.
It is designed such that even if it is a single-layer sealant layer, sufficient tearability is exhibited without substantially impairing the properties such as transparency, low temperature heat sealability, and antiblocking property originally possessed by.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a bag made from the laminated film (1) of the present invention.

2 is an XX section view of the bag of FIG. 1. FIG.

FIG. 3 is a graph showing a relationship between a blend ratio and an Elmendorf tear load measurement value.

FIG. 4 is a graph showing a relationship between a blend ratio and a measured value of breaking strength.

FIG. 5 is a graph showing a relationship between a blend ratio and a measured value of elongation at break.

[Explanation of symbols]

(1) ... laminated film, (11) ... Base film layer, (12) ... Sealant layer, (2)… Heat seal part, (3)… notch, (4)… Line fastener

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 23/08 C08L 23/08 4J040 45/00 45/00 65/00 65/00 C09J 7/02 C09J 7 / 02 Z 123/08 123/08 145/00 145/00 165/00 165/00 C09K 3/10 C09K 3/10 ZF term (reference) 3E086 AB01 AC07 AC16 AC22 BA04 BA15 BA33 BB22 BB51 BB90 4F100 AK01 AK01A AK02B AK02C AK02G AK63B AK63C AK63G AL01B AL01C AL05B AL05C AT00A BA02 BA03 BA06 BA07 BA10A BA10B BA10C GB15 JA15B JA15CJL00 JL12B JL12C JL14 CA01 CA04 A04A00 A05A04A05 AB05 AC02A04 AB05 AC02J04A01 AB05 AC02B06A02 JB01 LA02 LA06 NA06 PA23

Claims (5)

[Claims] 1. A laminated film having a structure in which a sealant layer (12) is provided on at least one surface of a base film layer (11).
(1), the sealant layer (12), ethylene-α-olefin copolymer (A) and amorphous cycloolefin polymer (B) produced by a single-site catalyst
A packaging film comprising a layer of the composition (AB) in a weight ratio of 85:15 to 40:60. 2. The packaging film according to claim 1, which is a laminated film (1) for forming a packaging container by heat-sealing necessary parts using a sealant layer (12). 3. The packaging film according to claim 1, wherein the ethylene / α-olefin copolymer (A) has a density of 880 to 920 kg / m ³ . 4. The packaging film according to claim 1, wherein the amorphous cycloolefin polymer (B) has a glass transition point Tg of 100 ° C. or lower. 5. The packaging film according to claim 1, wherein the amorphous cycloolefin polymer (B) is a hydrogenated product of a norbornene ring-opening polymer.