JP5031211B2 - Polyester composition and film - Google Patents

Description

  The present invention relates to a polyester-based resin composition and an inflation film, and more particularly, a polyester-based resin that can be applied to a recycled polyester resin and a recycled polyolefin resin and can mold an inflation film excellent in transparency and tear strength. The present invention relates to a composition and a film comprising the same.

  A film of polyethylene terephthalate resin (hereinafter referred to as PET resin) is widely used in the field of video tape and the like, and the film is manufactured by casting a PET resin. However, it is difficult to form a film of PET resin by a more general inflation molding method because its melt viscosity is extremely low, and an inflation film is not actually produced from PET resin.

Recently, the technology for recycling used PET bottles has advanced, and the recovery of used polyolefin resin has been carried out in many industrial fields including automobile parts. In general, the regenerated product has a lower molecular weight than that of an unused product, and the mechanical properties are also lowered accordingly. Accordingly, if a new utilization method combining recycled PET resin and recycled polyolefin resin is conceivable while compensating for the effect of physical properties of the recycled product, the social demand of resource recycling can be met.
Therefore, a composition in which a compatibilizing agent having a polar group is blended with a PET resin and a polyolefin resin, and a molded article comprising the same have been developed.

  For example, Patent Document 1 and Patent Document 2 include a phase having at least one functional group selected from the group consisting of ethylene repeating units and a carboxyl group or a derivative group thereof, an epoxy group, a hydroxyl group, and an amino group. Containers have been proposed. Since the acid anhydride group or epoxy group reacts with the terminal hydroxyl group or carboxylic acid group of the PET resin to form a cross-linked structure in the PET resin, as a result, the melt viscosity of the PET resin increases and an inflation film can be formed. .

However, when a compatibilizing agent having an acid anhydride group or an epoxy group is used, the film obtained by the inflation molding method may be inferior in transparency and tear strength.
Japanese Patent Laid-Open No. 2003-238786 JP 2003-342426 A

  Therefore, the present invention relates to a film obtained by inflation molding a resin composition comprising polyester and polyolefin, and a polyester resin composition capable of molding a film having good gloss, excellent transparency and excellent tear strength, and the same. The purpose is to provide a film.

The inventors have conducted intensive studies,
(A) Polyester resin 50 to 90% by weight, (B) Ethylene / α-olefin copolymer 5 to 40% by weight, (C) Binary copolymer 3 to 20 comprising ethylene units and units having ester groups A polyester resin composition comprising: wt% (here, the total amount of A, B, and C is 100 wt%).
Has found that the above problems can be solved, and has completed the invention.

  The (C) is preferably a binary copolymer of ethylene and an acrylate ester, and the acrylate ester is particularly preferably selected from methyl acrylate, ethyl acrylate, and butyl acrylate. Although it is usually preferable to use one acrylate ester, two or more units selected from methyl acrylate, ethyl acrylate, and butyl acrylate may be used.

  Further, a polyester-based resin composition characterized in that the density of the ethylene / α-olefin copolymer (B) is 0.92 (g / cm 3) or less is more preferable. When the density is within this range, the compatibilizing action is further enhanced, and the impact resistance of the resulting resin composition and film is improved, which is preferable. A film obtained by inflation molding of the resin composition of the present invention is preferable because it is excellent in transparency and tear strength.

  The present invention provides a polyester resin composition capable of forming an inflation film excellent in transparency or tear strength, and an inflation film comprising the same. A film obtained by forming the resin composition described above into an inflation film has a pearly luster that is not found in conventional polyester films, and has relatively good transparency. Moreover, since the direction tear strength is strong, which is also a drawback of PET-based alloy films, it is expected to be used in various applications. In addition, although gloss and transparency said here are not completely transparent like the film of 100% of polyester, for example, when it is made into a bag shape, the transparency which can fully confirm the content is shown.

  The blown film provided by the present invention uses polyester resin as a main raw material, and therefore has excellent aroma retaining property of polyester resin, and is suitable for a bag containing a strong odor. When processing into a bag shape, heat sealing at a low temperature is possible, and processing can be easily performed. Further, since the polyester resin has little combustion heat, there is an advantage that the heat load on the incinerator or the like can be reduced when it is finally discarded.

[Polyester resin (A)]
The polyester resin that can be used in the present invention is basically a polycondensate of an aromatic or aliphatic dicarboxylic acid and a diol. In the production, one kind of dicarboxylic acid and one diol are selected, or two kinds are used. The above is selected in combination, and it is produced under ordinary polycondensation conditions in the presence of a catalyst.

  Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, adipic acid, sebacic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, and diphnyl ether-4,4′-dicarboxylic acid. Can do.

  Examples of the diol include ethylene glycol, propylene glycol, 1,4-butylene glycol, neopentyl glycol, cyclohexanedimethanol, 2,2-bis (4-hydroxyphenyl) propane, and the like. In the polycondensation, a hydroxycarboxylic acid such as p-hydroxybenzoic acid may coexist.

  Examples of the polyester resin produced from the dicarboxylic acid and the diol include polyethylene terephthalate (PET) and polybutylene terephthalate. The polyester resin may be a recycled product after once using those molded products, or may be a mixture of an unused product and a recycled product. As the polyester resin, polyethylene terephthalate is preferable.

  These polyester resins are polymers having an intrinsic viscosity (IV) measured in a mixed solvent of phenol / tetrachloroethylene = 50/50 (weight ratio) at 25 ° C. in the range of 0.60 to 0.85 (dl / g). Is suitable for blown film molding.

[Ethylene polymer (B)]
The ethylene polymer that can be used in the present invention is not particularly limited, but among the general ethylene polymers, those belonging to the low density range are preferred. Specifically, the density is desirably 0.92 or less, preferably less than 0.91, and more preferably in the range of 0.87 to 0.91 (g / cm 3). When a polymer in such a density range is used as one component of the film-constituting resin, a sufficient mechanical strength improving effect on the polyester resin can be obtained, and heat sealability at a low temperature can be imparted.

  The ethylene polymer is any polymer having an ethylene unit as a main repeating unit, such as an ethylene homopolymer, an ethylene / α-olefin copolymer, and a copolymer of ethylene and a vinyl monomer. can do.

  Among them, the ethylene / α-olefin copolymer may be a crystalline or amorphous ethylene / α-olefin copolymer, and has crystallinity and properties close to those of an ethylene homopolymer. It may be an ethylene / α-olefin copolymer. Therefore, the monomer composition constituting the ethylene / α-olefin copolymer has a wide range of 70 mol% or more of ethylene units and 30 mol% or less of α-olefin units. Here, the α-olefin can be appropriately selected from the above-mentioned olefins having 3 to 20 carbon atoms, and in particular, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1- Octene is preferred.

  Such an ethylene / α-olefin copolymer in the range from crystalline to amorphous has a Ziegler catalyst, a cyclopentadienyl ring, which is an example of a combination of a vanadium compound or a titanium compound and an organoaluminum compound. It can be produced by using an olefin stereoregular polymerization catalyst such as a metallocene catalyst using a combination of a zirconium compound and an oxyaluminum compound as an example.

  Preferred ethylene polymers are ethylene homopolymers or ethylene / α-olefin copolymers, particularly low density polyethylene, crystalline ethylene / 1-hexene copolymers, amorphous ethylene / propylene copolymers. A polymer, an amorphous ethylene / 1-butene copolymer, and an amorphous ethylene / 1-octene copolymer are preferred. If an ethylene polymer is used as a component of a film-forming resin composition, the resin composition may become white opaque depending on the type of the polymer. If a transparent film is required, the ethylene polymer It is necessary to select the type and blending amount as appropriate.

  The melt flow rate (MFR) is 0.1 to 20, preferably 0.1 to 10, more preferably 0.1, as measured under a load of 190 ° C. and 2.16 kg in accordance with ASTM D-1238. 5-10 (g / 10 minutes). When the value of MFR is within this range, the formability of the inflation film can be improved, the mechanical strength of the film can be increased, and low temperature heat sealability can be imparted.

  Examples of ethylene polymers suitable for actual use include medium- and low-pressure low-density polyethylene including linear low-density polyethylene (L-LDPE), and even if they are unused polymers, they can be recycled. It may be a product.

[Compatibilizer (C)]
The compatibilizer (C) is a binary copolymer composed of an ethylene unit and a unit having an ester group. Examples thereof include an ethylene / acrylic ester copolymer, an ethylene / methacrylic acid ester copolymer, and an ethylene / vinyl acetate copolymer.

  As ethylene / (meth) acrylic ester copolymer, ethylene / methyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / butyl acrylate copolymer, and ethylene / methyl methacrylate copolymer, Examples thereof include an ethylene / ethyl methacrylate copolymer and an ethylene / butyl methacrylate copolymer. (C) is preferably a binary copolymer of ethylene and an acrylate ester. Among them, an ethylene / methyl acrylate copolymer, an ethylene / ethyl acrylate copolymer, and an ethylene / butyl acrylate copolymer are preferable. preferable.

The acrylic acid ester unit of ethylene / acrylic acid ester is preferably blended in an amount of 10 wt% or more, more preferably 20 wt% or more in order to keep the reactivity with the PET resin high. When the acrylic ester content is less than 10 wt%, the resin composition has a low melt viscosity, and the film does not stand up during the formation of an inflation film, or the bubble shakes greatly, making stable molding difficult. The upper limit of the acrylate unit is not particularly defined, but is preferably 30 wt% or less.
As the copolymer, any of random and block polymers can be used, but the random copolymer is more preferable in terms of compatibilizing action.

[Resin composition]
The mixing ratio (% by weight) of each component constituting the resin composition is as follows:
(A) Polyester resin 50 to 90% by weight, (B) Ethylene / α-olefin copolymer 5 to 40% by weight, (C) Binary copolymer 3 to 20 comprising ethylene units and units having ester groups % By weight (here, the total amount of the three components is 100% by weight).
When each component is within this composition range, it is possible to easily form an inflation film, to obtain a film having excellent mechanical strength and heat sealability, and excellent transparency and tear strength.

The range of the resin composition is desirably in the range shown in Table 1, and the constituent components have a configuration of (A) + (B) + (C), and the total amount of each constituent component is 100% by weight in any case. It becomes.

  Various additives can be appropriately added to the resin composition without departing from the object of the present invention. Examples of the additive include an antioxidant, a weathering stabilizer, a light stabilizer, an antistatic agent, an antiblocking agent, a nucleating agent, a lubricant, and a pigment.

[Film production]
Prior to film production, first, a Henschel mixer, a V-blender, a ribbon blender, a tumbler blender, etc. are used to dry blend the above components to a predetermined mixing ratio to prepare a uniform composition, which is a resin composition for forming an inflation film It is a thing. Moreover, it is good also as a pellet-shaped inflation film molding resin composition by adding melt-kneading after that using a single screw extruder, a twin screw extruder, a kneader, a Banbury mixer, a mixing roll, etc.

  When manufacturing the above-described pellet-shaped resin composition, it is desirable that the polyester resin is sufficiently dried before the polyester resin is melt-kneaded in order to avoid hydrolysis of the polyester resin. Alternatively, it is possible to take a method of removing water to a water absorption amount that does not cause deterioration of physical properties by applying a pressure reduction operation from the vent port of the extruder.

  The resin composition from which moisture has been removed in this way is then supplied to an inflation film molding machine. Also in this case, the remaining water can be removed by applying a pressure reducing operation from the vent port provided in the extruder part of the inflation film molding machine in the same manner as in the production of the pellet-shaped resin composition. . The resin composition is melted in the cylinder of the extruder part, the molten resin is extruded from a circular die provided at the tip of the extruder, and then cooled by inflating into a cylindrical shape by adjusting the amount of air, and then folded in half, or An inflation film can be manufactured by separating and winding into one or two sheets. The screw used in the extruder part of the inflation film forming machine is not particularly limited, and cooling is preferably performed by ordinary air cooling. If necessary, stretch orientation in a uniaxial or biaxial direction can be performed thereafter.

[Polyester film]
The inflation film is usually 10 to 200 μm, but in order to keep the transparency characteristic of the present invention high, it is preferable that the film has a thickness of about 10 to 50 μm. When the resin composition in the range shown in Table 2 is employed, stable film formation is possible and various characteristics can be imparted to the film. When the resin composition of the first form, that is, (A) + (B) + (C) is employed, the film has excellent tensile strength, gloss and transparency, and tear strength.

  EXAMPLES Next, although this invention is demonstrated through an Example, this invention is not limited at all by these Examples. The materials used in the examples and comparative examples are as follows.

(1) Polyester resin: Polyethylene terephthalate resin (A):
Intrinsic viscosity (IV) = 0.73 (dl / g)
(2) Ethylene / α-olefin copolymer: linear low density polyethylene (B):
Density = 0.903 (g / cm ³ ), MFR = 1.2 (g / 10 min, 190 ° C.)
(3) Binary copolymer (C) comprising an ethylene unit and a unit having an ester group:
Ethylene / methyl acrylate copolymer, methyl acrylate content = 25wt%
( 4 ) Carboxylic acid-modified ethylene / α-olefin copolymer ( D ):
Maleic acid graft-modified ethylene / propylene copolymer, MFR = 0.3 (g / 10 min, 230 ° C.), density = 0.870 (g / cm ³ )
( 5 ) Epoxy-modified ethylene terpolymer ( E ):
Ethylene / methyl acrylate / glycidyl methacrylate 3 copolymer, methyl acrylate 8 wt%, glycidyl methacrylate 6.5-9 wt%

Here, it shows about the shaping | molding method of the film shown in the Example and the comparative example. The resin composition was a three-component system in which one of the following was added as a compatibilizer to the two components of the polyester resin (A) and the ethylene / α-olefin copolymer (B). Comparison was compatibilizers, binary copolymer consisting of units having a d styrene unit and an ester group (C), carboxylic acid-modified ethylene · alpha-olefin copolymer (D), epoxy-modified ethylene terpolymer One of the polymers ( E ) and blended in the proportions shown in Table 2. Among these, as the polyester resin, in order to prevent hydrolysis during molding, a resin from which moisture was previously removed to 50 ppm was used.

  These three types of resins were dry-blended without being pelletized in advance, and directly supplied to an inflation molding machine (manufactured by Tommy Machinery: Examples and Comparative Examples also using this molding machine). The conditions for forming the inflation film were a cylinder temperature of 270 ° C., a die lip opening of 1 mm, and a take-off speed of 25 m / min. Film formation could be easily performed, and a film having a thickness of 30 μm was obtained. A test piece was cut out from this film, and Elmendorf tear strength, haze, and gloss were measured. The results are also shown in Table 2.

  The physical properties of the cut film were measured using the Elmendle tear test method defined in JISK7128-2, and the film pulling direction (vertical) direction was measured with a light capacity type tester manufactured by Toyo Seiki Co., Ltd. . Haze is measured with a NDH2000 type haze meter manufactured by Nippon Denshoku Industries Co., Ltd., as an index of transparency indicating optical properties, and gloss is measured by Nippon Denshoku under the condition of an incident angle of 60 ° according to the method defined in JIS-Z8741. Measurement was performed with a VG2000 type measuring instrument manufactured by Kogyo Co., Ltd.

Examples will be described below. In each case, the polyester resin was compared with a blended product of 75 wt% so that the polyester resin (A) became a matrix layer.
In Example 1, 20% by weight of an ethylene / α-olefin copolymer (B) and 5% by weight of an ester group-containing ethylene copolymer (C) as a compatibilizer are blended in a polyester resin, and inflation is performed by the above method. A film was formed. As shown in the film physical property column of Table 2, the film was excellent in gloss (gloss) and excellent in tear strength.
In Example 2, the ethylene / α-olefin copolymer was 15 wt%, and the ester group-containing ethylene copolymer was 10 wt%. Also in this case, the film was excellent in gloss and tear strength.

  In the comparative example, as in the example, 75 wt% of the polyester resin was blended so that the polyester resin became a matrix layer. The component of the compatibilizer is changed to the ester group-containing ethylene copolymer (C), and in Comparative Example 1, the carboxylic acid-modified ethylene / α-olefin copolymer (D) is used. In Comparative Example 2, the epoxy-modified ethylene-based 3 The original copolymer (E) was blended in an amount of 3 wt%, and an inflation film was formed in the same manner as in the examples. The results of evaluating film physical properties are shown in Table 2. Molding was smooth in all of the comparative examples, but the gloss of the film was lower than in the examples, the haze was slightly higher, and the transparency was lowered. The tear strength was reduced to 50% or less compared to the examples.

Claims (1)

(A) 70 to 90% by weight of a polyester resin, (B) 5 to 25% by weight of an ethylene / α-olefin copolymer, (C) a binary copolymer 3 to 20 comprising an ethylene unit and a unit having an ester group. % (Where the total amount of A, B, and C is 100% by weight),
The density of the ethylene / α-olefin copolymer (B) is 0.92 (g / cm ³ ) or less,
The binary copolymer (C) is an ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, and Ri der either ethylene-butyl acrylate copolymer, the two Mototomokasane A film obtained by blown film-forming a polyester-based resin composition having an acrylic ester unit content of 20 to 30 wt% in the coalescence (C) .