JP2003138037A - Polyester packaging film and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for packaging having a moderate flexibility and a good strength balance between longitudinal and horizontal directions using a recycled PET resin. SOLUTION: The polyester packaging film comprises a composition wherein a polyethylene terephthalate resin is 50-90 wt.%, a polybutylene terephthalate resin is 5-25 wt.% and a linear low density polyethylene is 5-25 wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the reuse of recovered polyethylene terephthalate resin, and in particular, the recovered polyethylene terephthalate resin is used as a raw material component to which polybutylene terephthalate and linear low density polyethylene are added. The present invention relates to a packaging film which is blended in a specific amount and melt-extruded by an inflation method, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, polyethylene terephthalate resin has been widely used as a material for beverage containers and sheets. In particular, containers made of polyethylene terephthalate resin called PET bottles are superior in terms of lightness, workability, strength, etc., compared to glass, paper and metal containers, and therefore rapidly. The amount of use has been increasing, and it has become a major environmental issue regarding its disposal.
From the viewpoint of effective use of resources, establishment of recycling technology is an urgent task.

From the standpoints of resource protection and environmental protection, various proposals have been made regarding the technology for reusing the recovered polyethylene terephthalate resin (hereinafter referred to as recycled PET resin), but it is said that it has been used. As for the amount of PET bottles and other containers that have become empty, even if the collection is done efficiently, there are still few proposals for powerful technologies that can fully digest the collected PET resin. . That is, when the recovered PET resin is crushed by a crusher and then melt-extruded by an extruder to be processed into pellets as a resin raw material, the intrinsic viscosity is lowered by hydrolysis,
That is, strength physical properties are deteriorated due to the decrease in molecular weight. Therefore, when the recovered PET resin is reused, the application tends to be limited, and the expanded use of the recovered resin has not progressed sufficiently.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to perform PET molding as a raw material for a packaging film, especially a packaging bag, which has a large demand. It is intended to reuse goods.
However, regarding the reuse of the recycled PET resin, when melt extruding using the recycled PET resin, the film moldability is poor, the film is hard and poor in flexibility, and only a film that is easily torn vertically is obtained, which is satisfactory. There is a problem in that the obtained packaging film cannot be obtained. An object of the present invention is to provide a packaging film which uses a recycled PET resin and has appropriate flexibility and has a good strength balance between the longitudinal direction and the lateral direction.

[0005]

Means for Solving the Problems As a result of various studies for solving the above-mentioned problems, the present inventor has blended polybutylene terephthalate and linear low density polyethylene in a specific ratio in recycled PET resin, The present inventors have completed the present invention by finding that a packaging film having improved film moldability, flexibility and excellent strength can be obtained. That is, the gist of the present invention is 50 to 90% by weight of polyethylene terephthalate resin and 5% of polybutylene terephthalate resin.
To 25% by weight and linear low density polyethylene 5 to 25% by weight, a packaging film,
And, a composition of 50 to 90% by weight of polyethylene terephthalate resin, 5 to 25% by weight of polybutylene terephthalate resin and 5 to 25% by weight of linear low density polyethylene was melt extruded from a die having an annular slit by an inflation method and extruded. The method for producing a polyester packaging film is characterized in that the diameter of the molten tubular film is reduced to the diameter of the annular slit or less, and then the tubular film is taken in while being expanded to a blow ratio of 1.5 or more.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The polyethylene terephthalate resin of the present invention (hereinafter,
It is called PET resin. ) Is a polymer obtained by polycondensing terephthalic acid or a terephthalic acid derivative as an acid component and ethylene glycol as a glycol component, and copolymerizing a part of the terephthalic acid component and / or the ethylene glycol component. It also includes a copolymer substituted with a component. Recycled PET resin can be preferably used as the polyethylene terephthalate. Recycled PET resin is usually used by crushing a polyethylene terephthalate beverage container (commonly called PET bottle) and re-pelletizing it. In the re-pelleting process, the intrinsic viscosity (η value) decreased due to water absorption and heat history. Can be used by adjusting by solid-state polymerization. The recycled PET resin can be used by appropriately mixing it with the virgin polyethylene terephthalate.

The intrinsic viscosity [η] of the PET resin is 0.4.
˜1.5 is preferable, and 0.6 to 1.1 is more preferable.
When [η] is less than 0.4, the tensile strength of the flat yarn is weak and longitudinal cracks are likely to occur, and when [η] exceeds 1.5, fluidity is poor during melt extrusion and yarn breakage occurs, which is not preferable.

The polybutylene terephthalate resin of the present invention (hereinafter sometimes abbreviated as PBT) is a polybutylene terephthalate resin obtained by polycondensing terephthalic acid or a terephthalic acid derivative as an acid component and tetramethylene glycol as a glycol component. Copolymers that are a combination and in which a part of the terephthalic acid component and / or the tetramethylene glycol component is replaced with a copolymerization component are also included.

The intrinsic viscosity [η] of the above PBT is 0.6-1.
8 is preferable and 0.8-1.5 is more preferable. When [η] is less than 0.6, PBT has a large crystallinity, so that vertical cracks are likely to occur, and when [η] exceeds 1.8, workability is deteriorated, which is not preferable.

Linear low density polyethylene (hereinafter referred to as LLDP
Called E. ) Is ethylene and α having 3 or more carbon atoms
Is an ethylene / α-olefin copolymer composed of an olefin, and the α-olefin as a comonomer has 3 or more carbon atoms, preferably 4 or more carbon atoms, more preferably 6 to 20 α-olefins, for example, 1 -Hexene,
4-methyl-1-pentene, 1-octene, 1-decene and the like can be mentioned. The polymerization catalyst can be produced using a coordination polymerization catalyst such as a Ziegler catalyst or a metallocene catalyst.

Particularly, it is preferable to use LLDPE having the following physical properties using a metallocene catalyst. 1) Melt flow rate (hereinafter abbreviated as MFR) is 0.
1 to 30 g / 10 min., But 5 to 20 g / 10
min. is preferable. If the MFR is less than 0.1 g / 10 min., The moldability is poor, and if it exceeds 30 g / 10 min. 2) density 0.86~0.94g / cm ^3, preferably 0.89~0.91g / cm ^3. Density is 0.86g
If it is less than / cm ³ , the stretchability is poor and the production is difficult, and if it exceeds 0.94 g / cm ³ , the flexibility is poor and it is not preferable. 3) Maximum peak temperature (Tm) by DSC is 80-12
The temperature is 5 ° C, preferably 90 to 120 ° C. If the maximum peak temperature (Tm) by DSC is less than 80 ° C, the difference from the stretching temperature becomes too small, and if it exceeds 125 ° C, the optimum stretching temperature becomes too high, which is not preferable. 4) The molecular weight distribution (Mw / Mn) is 1.8 to 3.5, preferably 2.2 to 3.0. If Mw / Mn is less than 1.8, the moldability is poor, and if it is 3.5 or more, the stretchability is poor, which is not preferable.

The method for producing the above ethylene / α-olefin copolymer is described in JP-A-58-19309 and JP-A-5-30939.
9-95292, JP-A-60-35005, JP-A-60-35006, and JP-A-60-35.
It can be obtained by copolymerizing ethylene and α-olefin using a metallocene catalyst described in JP-A No. 007, JP-A-60-35008, JP-A-60-35009 and the like.

The blending ratio with the above PET / PBT / LLDPE is in the range of 50 to 80% by weight of PET / 5 to 25% by weight of PBT / 5 to 25% by weight of LLDPE, preferably 60 to 80% by weight of PET / 10 to 20% by weight of PBT. %
/ LLDPE is in the range of 10 to 20% by weight. If the blending ratio of PBT is less than 5% by weight, the flexibility of the obtained film is insufficient and the effect of preventing vertical cracking of the film is insufficient, while if it exceeds 25% by weight, the melt viscosity of the extruder becomes high. However, the film moldability is deteriorated, which is not preferable. Further, if the blending ratio of LLDPE is less than 5% by weight, the effect of improving the moldability and strength of the film is insufficient, while if it exceeds 25% by weight, the heat resistance of the film is lowered, which is not preferable.

In the present invention, the composition of PET, PBT and LLDPE is used to melt-extrude from a die having an annular slit by an inflation method, and the extruded molten tubular film has a diameter smaller than the diameter of the annular slit, Preferably, the diameter of the tubular film is reduced to 0.70 to 0.95 times the diameter of the annular slit, more preferably 0.80 to 0.95 times, and then the blow ratio is 1.5 or more, preferably. Is 2 to 6, more preferably 3
It is characterized in that it is taken up while being expanded within the range of -5. The blow ratio means the ratio of the diameter of the film product to the diameter of the annular slit.

If the diameter of the extruded tubular film in the molten state is larger than the diameter of the annular slit, the molecular orientation in the lateral direction of the film is insufficient, and only a film that is easily torn vertically is obtained, while in the molten state. If the diameter of a certain tubular film is smaller than 0.70 times the diameter of the annular slit, bubbles become unstable, which is not desirable.

If the blow ratio is less than 1.5, the strength of the film in the transverse direction is not sufficiently improved, and vertical tearing is not easily obtained. If the blow ratio is greater than 6, bubbles oscillate. Moldability becomes unstable, which is not desirable.

In the present invention, after the tubular film in a molten state is made smaller than the diameter of the annular slit and then the blow ratio is combined within the above range, a synergistic effect can be obtained as compared with the case where only the blow ratio is within the above range. By virtue of this, the lateral molecular orientation of the film can be strongly caused, whereby the lateral strength of the film can be improved, and a film having a good strength balance between the longitudinal direction and the lateral direction can be obtained.
The thickness of the film is generally 10-100 μm.
m, and preferably in the range of 15 to 50 μm, and is suitable for use in packaging bags.

Further, it is preferable to form the film at a take-up speed / extrusion speed ratio of 3 or more, preferably 4 or more, from the viewpoints of molding stability, strength balance of the forming film, and the like.

The polyethylene terephthalate resin composition used in the present invention includes an antioxidant, an ultraviolet absorber, a light stabilizer, a lubricant, an antistatic agent, a pigment and a flame retardant within the scope of the present invention. Inorganic fillers, nucleating agents, foaming agents, dispersants, and other commonly used additives may be added.

[0020]

Example 1 The recovered PET bottle was crushed, melt-extruded, pelletized, and dried at 160 ° C. for 5 hours. Intrinsic viscosity = 0.65
70 parts by weight of dl / g recycled PET resin (melting point = 254 ° C.), 15 parts by weight of polybutylene terephthalate resin (melting point = 228 ° C.) having an intrinsic viscosity [η] of 0.85, and ethylene produced using a metallocene catalyst. -Α-olefin copolymer (MFR = 2.5 g / 10 minutes, density = 0.92 g
/ Cm ³ , Tm = 115 ° C., Mw / Mn = 2.8) 15
An inflation molding apparatus in which a resin composition in which 4 parts by weight of a masterbatch having a calcium carbonate content of 40% by weight is mixed with a composition in which 50 parts by weight is blended and a die having a 50 mmφ annular slit is attached to a 50 mmφ extruder. Was blown at a melting temperature of 275 ° C. to obtain a film. The film was formed under the conditions shown in Table 1 for the blow ratio, the take-up speed and the film thickness, and the stability was evaluated by the bubble stability and the strength balance of the obtained film.

The bubble stability was evaluated by visually observing the bubble and grading it in three grades: good, moderately good and unstable. Regarding the strength balance, tear the obtained film in the take-up direction by hand, and check whether the direction of the cut is in the vertical direction, the horizontal direction, or the diagonal direction. One-sided one was regarded as defective.

Examples 2 to 5 and Comparative Examples 1 to 3 The same procedure as in Example 1 was carried out except that the molding conditions were changed as shown in Table 1. The results are shown in Table 1.

[Table 1]

[0023]

As described above, the packaging film of the present invention has good moldability and longitudinal splitting by blending a specific amount of polybutylene terephthalate resin and linear low density polyethylene with polyethylene terephthalate resin. It is possible to form a difficult packaging film, and this packaging film has an excellent strength balance in length and width, and is suitably used as a packaging bag.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 67/02 C08L 67/02 // (C08L 67/02 23:06 23:06) B29K 23:00 B29K 23:00 67:00 67:00 B29L 7:00 B29L 7:00 F term (reference) 3E086 AB01 BA02 BA15 BB90 DA08 4F071 AA19 AA45 AA46 AH04 BA01 BB06 BB09 BC01 4F210 AA08 AA24 AA25 AG01 AR12 QA01 QK01 QK05 4061 BB03 GG02

Claims (4)

[Claims] 1. A polyethylene terephthalate resin 50 to
90% by weight, polybutylene terephthalate resin 5 to 25
A polyester packaging film, characterized by comprising a composition of 5% by weight and linear low-density polyethylene of 5 to 25% by weight. 2. A linear low density polyethylene produced by using a metallocene catalyst and having a density of 0.86 to 0.94 g / cm.sup.2.
The polyester packaging film according to claim 1, which is in the range of ³ . 3. A polyethylene terephthalate resin 50 to
90% by weight, polybutylene terephthalate resin 5 to 25
The composition of 5 wt% and linear low density polyethylene of 5 to 25 wt% is melt extruded from a die having an annular slit by an inflation method, and the diameter of the extruded molten tubular film is reduced to the diameter of the annular slit or less. The method for producing a film for polyester packaging is characterized in that the film is blown while being expanded to a blow ratio of 1.5 or more. 4. A method of reducing the diameter of the extruded tubular film in a molten state to 0.70 to 0.95 times the diameter of the annular slit, and then taking it while expanding it to a blow ratio of 2 to 5. The method for producing a film for polyester packaging according to claim 1, which is characterized in that.