JPH0585347B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to wrapped film. For more details, please refer to various food products such as vegetables, fruits, fish and shellfish, and livestock meat, as well as prepared products at home, supermarkets, food processing companies, department stores, grocery stores, refrigeration companies, sushi restaurants, soba restaurants, and other restaurants. This invention relates to a polyolefin wrap film used as a packaging material. [Prior art] Conventional wrap films include polyvinylidene chloride, polyvinyl chloride, high-pressure polyethylene, ethylene-vinyl acetate copolymer, polypropylene,
Materials made of linear low-density polyethylene, polybutadiene, etc. have been proposed, and polyvinylidene chloride, polyvinyl chloride, high-pressure polyethylene, polybutadiene, etc. have been put into practical use. Wrap film is used to easily package, protect, store, distribute, and display fresh foods, so it is required to have the following performance characteristics. Since the wrap film covers the article to be packaged and temporarily adheres the wrap films to each other by pressure bonding, it must have an appropriate degree of adhesiveness, and must be easily peeled off when the article is to be removed. In the case of simple packaging for business use, it may be packaged by heat sealing, so it must have good heat sealability. The product form of Wrap Film is 20cm to 45cm wide, 7 to 20μ thick, and 20 to 50m long, wrapped around a paper tube shaft. It comes in a cardboard storage box with a knife attached, so when you want to use it, pull the wrap film out of the box and cut it with a saw-shaped knife. Therefore, the wrap film must be easily cut with relatively low force. In addition, in the case of business-use wrap film, when making cuts with a knife and cutting it, the work efficiency will be poor if the wrap film is not cut cleanly and quickly in the horizontal direction, but it will change direction in the vertical direction midway through the cut and tear. However, this kind of thing is not desirable. Since the content is often food, the material must not contain ingredients that pose a food hygiene problem, and must be heat-proof, waterproof, moisture-proof, air-proof, acid-proof, oil-proof, and have appropriate strength. , stretchability, and shrinkability are required. Furthermore, since it is displayed as a product, transparency, drip-proofing, anti-fogging properties, glossiness, etc. are required so that the contents can be clearly seen. In storage, in order to maintain freshness for a long period of time, ultra-low temperature refrigerators of -50°C have recently come into use, so the low temperature embrittlement resistance of wrap film materials has become an issue. When cooking using a microwave oven, heat resistance is required, and a material that does not cause the film to shrink or tear due to heat is required. Since wrap film is a consumable item, it is desired that the price be as low as possible. Conventionally, wrap films commercially available are mainly made from polyvinylidene chloride, polyvinyl chloride, low density polyethylene, ethylene-vinyl acetate copolymer, polybutadiene, etc. However, when cutting polyvinylidene chloride with a saw blade, the cracks tend to run in arbitrary directions regardless of the user's opinion, resulting in diagonal cuts, and when used in a microwave oven, they may be cut diagonally. There is a problem that the film shrinks greatly and breaks, and in high temperature conditions, it is exposed to hydrochloric acid gas,
There is a risk of generating chlorine gas and vinylidene chloride, which is undesirable from a food hygiene perspective, and there are concerns that it may be carcinogenic. Polyvinyl chloride-based materials are inexpensive and are used commercially, but they tend to whiten when exposed to boiling water and contain large amounts of plasticizers, and have the same problems as polyvinylidene chloride-based materials. In addition, polyvinylidene chloride and polyvinyl chloride contain chlorine, making them flame-retardant and difficult to dispose of.Furthermore, they emit gas harmful to the human body when burned or film-formed, which poses a problem. Low-temperature embrittlement is also poor. To overcome the drawbacks of chlorinated resins, non-chlorinated high-pressure low-density polyethylene has been commercialized, but it lacks tackiness, so a large amount of tackifier must be added to provide the necessary adhesive strength. As a result, the mechanical strength and stiffness of the film are reduced, and the cutting performance with a saw blade is also very poor. Ethylene-vinyl acetate copolymer systems have improved adhesiveness, but have problems with mechanical strength, stiffness, etc. Polypropylene-based materials have excellent heat resistance, but have problems with low-temperature embrittlement resistance, adhesion, and cutability with a saw blade. Linear low-density polyethylene has superior mechanical strength compared to high-pressure processed low-density polyethylene, but when it is formed using a normal blown film processing method, it has poor orientation in the vertical and horizontal directions. It is unbalanced and highly oriented in the longitudinal direction, making it difficult to cut with a saw blade and cannot be used as a wrap film. Furthermore, the film has poor peelability when used after being peeled off from the roll. Although polybutadiene has many excellent properties such as adhesiveness, low-temperature embrittlement, transparency, and cuttability with a saw blade, it has low mechanical strength such as tear strength. Another problem is that it is extremely expensive. The inventor has disclosed in Japanese Patent Application No. 1-26574 that the density is
Linear low density ethylene of 0.910g/ml or less and α-
We focused on the excellent transparency, tear strength, cutting properties, heat resistance, puncture resistance, low-temperature embrittlement, and extensibility of the binary copolymer with Off-in, and investigated its shortcomings by developing an ethylene-vinyl acetate copolymer. I am applying for a wrap film supplemented by merging. However, although the binary copolymer of ethylene and α-olefin used in the present invention has properties superior to other wrap polymers, it does not meet the performance requirements for the severe usage of wrap films, such as puncture resistance. , tensile strength, impact resistance, etc., could not be fully met. [Problems to be Solved by the Invention] Conventional wrapped films have various problems as described above. The present invention has no food hygiene problems, mechanical strength, transparency, adhesiveness, food protection, cuttability with a saw blade, puncture resistance, impact resistance, heat resistance,
The object of the present invention is to provide a wrapped film with excellent heat-sealing properties, and in particular, to provide a wrapped film with improved puncture resistance, impact resistance, and tensile strength. [Means for solving the problem] The present inventor has recently developed a solution with a density of 0.910 g/ml.
The present invention was completed by paying attention to the following linear low-density ethylene-butene-1-hexene-1 copolymer, taking advantage of its excellent properties, and compensating for its drawbacks with an ethylene-vinyl acetate copolymer. That is, the present invention provides: (1) linear ethylene having a density of 0.910 g/ml or less;
A wrap film comprising an intermediate layer made of a butene-1-hexene-1 copolymer and an outer layer made of an ethylene-vinyl acetate copolymer. (2) Linear ethylene-butene-1-hexene-1
The above-mentioned copolymer is produced by a gas-phase, low-pressure method using a so-called Ziegler catalyst, which is a catalyst produced by a combination of a transition metal compound of Group ~ and an organic metal of Group ~ in the periodic table. Rap film. (3) Linear ethylene-butene-1-hexene-1
When the copolymer is heated in a fluidized bed reaction zone at a temperature of 10° to 80°C and a pressure of 7000 KPa or less, (a) 0.35:1 to
Ethylene, butene-1 and hexene-1 in a molar ratio of 8.0:1 (total moles of butene-1 and hexene-1, where the molar ratio of butene-1 and hexene-1 is 0.5:1 to 2:1) to ethylene. 1 and (b) at least 25 mol % of at least one diluent gas with the formula: Mg _n Ti (OR) _o X _p [ED] _q [wherein R is 1 to 14 carbon atoms] an aliphatic or aromatic hydrocarbon group having atoms or COR', where R' is an aliphatic or aromatic hydrocarbon group having 1 to 14 carbon atoms, and X is Cl, Br, ED is an organic electron-donating compound selected from the group consisting of alkyl esters of aliphatic or aromatic acids, aliphatic ethers, cyclic ethers, and aliphatic ketones, and m is selected from the group consisting of I and mixtures thereof; 0.5 to 56, n is 0.1 or 2, p is 2 to 116, and q is 2 to 85]; The precursor composition is diluted with an inert carrier material and has the formula: Al(R') _d X' _e H _f [where X' is Cl or OR'' and R' and R'' are 1 to 14 is a saturated hydrocarbon group having carbon atoms, e is 0 to 1.5, f is 0 or 1, and d+e+f=3], and the activated compound is completely activated with an organoaluminum compound having The total aluminum to titanium molar ratio in the reaction zone is 10:
The above-mentioned wrapped film is produced by a continuous method for producing an ethylene copolymer, characterized in that it is used in an amount of 1 to 400:1. (4) The ethylene-vinyl acetate resin in the outer layer has a melt index of 0.3 to 3 g/10 min and a vinyl acetate content of 5 to 20% by weight, and the relationship between melting point (MP) and vinyl acetate content (VA) is MP= It is expressed as 114 to 1.44VA (MP unit is °C, VA unit is wt%), and the molecular weight distribution (w/n) is less than 4 (where w is the weight average molecular weight and n is the number average molecular weight). Lap film above. (5) The wrap film as described above, wherein the inner layer is a linear ethylene-butene-1-hexene-1 copolymer as shown in claim 3, and the outer layer is an ethylene-vinyl acetate copolymer as shown in claim 4. . The ethylene-butene-1-hexene-1 copolymer used in the present invention can be produced by the method disclosed in JP-A-59-230011. The ethylene-vinyl acetate copolymer used in the present invention preferably has M1 in the range of 0.3 to 3 g/10 min. If M1 is smaller than 0.3, there is a drawback that during film forming, too much load is placed on the extruder and productivity cannot be improved. Furthermore, if M1 is greater than 3.0, problems may arise in the tensile strength of the film, resistance to tearing due to sharp corners, etc., which is undesirable. Further, the content of vinyl acetate is 5 to 25% by weight, preferably 10 to 20% by weight. If it is less than 5% by weight, the clinging property will not be exhibited, and the extensibility, flexibility, and transparency will be insufficient, which is not desirable. If it exceeds 25% by weight, heat resistance, tensile strength, resistance to tearing due to sharp corners, etc. will be insufficient, which is not desirable. The relationship between the melting point (MP) and the vinyl acetate content (VA) of the ethylene-vinyl acetate copolymer used in the present invention is as follows: MP = 114-1.44VA (MP is in °C, VA is in wt%). Particularly preferred are those having a molecular weight distribution (w/n) of less than 4 (where w is the weight average molecular weight and n is the number average molecular weight, measured by gel permeation chromatography (GPC)). It is. The reason for this is that when compared at the same VA%, the melting point is 2-5°C higher than that of general ethylene-vinyl acetate copolymers, so heat resistance is improved. Further, when w/n is less than 4, a particularly tough film can be obtained and there is little odor. It is desirable to add an antifogging agent to the ethylene-vinyl acetate copolymer of the present invention, such as a glycerin aliphatic ester, a sorbitan aliphatic ester, a polyglycerin fatty acid ester, a propylene glycol fatty acid ester, an ethylene oxide adduct, or an adduct thereof. Mixtures of are particularly preferred, although other antifogging agents can also be used. By using a linear ethylene-butene-1-hexene-1 copolymer with a density of 0.910 g/ml or less as an intermediate layer, the present invention has heat resistance that can withstand up to about 130°C and is transparent. The properties of wrap film include flexibility, flexibility, low temperature resistance, puncture resistance, impact resistance, and cutability with a saw blade.
By using an ethylene-vinyl acetate copolymer as the outer layer, the wrap film is provided with clinging properties to the object to be wrapped, self-adhesion of the wrapped films to each other, heat fusion properties, extensibility, etc., and when each wrap film is constituted by itself. This provides a wrapped film with excellent properties that compensate for the shortcomings of both. Plastics conventionally used as wrap film materials other than the linear ethylene-butene-1-hexene-1 copolymer with a density of 0.910 g/ml or less of the present invention, such as polyvinylidene chloride, polyvinyl chloride, high pressure When using processed polyethylene, polypropylene, polybutadiene, linear ethylene-α-olefin copolymer (so-called L-LDPE) with a density of 0.910 g/ml or more as the intermediate layer,
Effects like those of the present invention cannot be obtained. That is, polyvinylidene chloride, polyvinyl chloride, etc. contain chlorine, which causes problems when incinerated, high-pressure polyethylene, polypropylene, and L-LDPE have problems with transparency, flexibility, low-temperature properties, etc., and polybutadiene is expensive. It is very high, and its tear strength, heat resistance, oil resistance, etc. are also insufficient. Ethylene with an intermediate layer density of 0.910g/ml or less
When the wrapped film is composed only of butene-1-hexene-1 copolymer, it has better transparency, clinging properties, self-adhesiveness, extensibility, and antifogging properties than when the outer layer is supplemented with ethylene-vinyl acetate copolymer. , antistatic properties, etc. are inferior, and the cost is higher than ethylene-vinyl acetate copolymer, so it is better to use it together with the cheaper ethylene-vinyl acetate copolymer than to use it alone, which reduces the overall cost of the wrap film. Can be lowered and is desirable. The wrap film of the present invention is molded using a coextrusion molding machine using a resin composition to form an intermediate layer and an outer layer. For example, they are laminated and molded by a known method such as an inflation method using a circular die or a T-die method using a flat die. The thickness of the wrapped film of the present invention is 10 to 50 microns, preferably 12 to 20 microns. If it is thinner than 10μ, it will be inconvenient to handle and the strength will be insufficient, which is not desirable. If it is thicker than 50 μm, there will be no performance problem as a wrapped film, but it will be disadvantageous in terms of cost, which is not desirable. Ethylene-butene-1 with a density of 0.91 g/ml or less
The thickness of the intermediate layer made of -hexene-1 copolymer is 3 to 30μ, preferably 5 to 15μ. If it is thinner than 3μ, the wrap film will have insufficient heat resistance, mechanical strength, etc., which is not desirable. Also,
If it is thicker than 30μ, it is not desirable because it has poor transparency and is disadvantageous in terms of cost. The thickness of each ethylene-vinyl acetate copolymer layered on both surfaces of the intermediate layer is 2 to 20 microns, preferably 5 to 15 microns.
If the film is thinner than 2μ, self-adhesiveness, clinging properties, and transparency cannot be imparted to the wrap film.
Undesirable. Moreover, if it is thicker than 20μ, the heat resistance and mechanical strength of the wrap film will be impaired, which is not desirable. Examples Raw Materials Intermediate layer: An ethylene-butene-1-hexene-1 copolymer (DEFD-1064 manufactured by Nippon Unicar Co., Ltd.) prepared by a gas phase low pressure method with a density of 0.910 g/ml and M1 = 1.0 was used. Both outer layers: An ethylene-vinyl acetate copolymer (DQDJ-1868 manufactured by Nippon Unicar) made by a high-pressure method with a density of 0.94 g/ml and M1 = 2.5 was used. An antifogging agent and sorbitan monooleate (manufactured by Riken Vitamin) were added at a concentration of 2% by weight. Method for producing blown film A blown film was produced by rapid cooling using the following equipment and processing conditions. (1) Extrusion equipment: Inflation film processing equipment made by Placo Co., Ltd. Diameter 40mm x 3 units L/D28 (2) Annular three-layer die: φ150mm Die gap: 1.0mm (3) Cooling equipment: Single lip straight and conical With collar (4) Discharge rate: 45Kg/hr (5) Die temperature: 180℃ (6) Blow ratio: 4.5 Manufactured wrap film Outer layer (1) Thickness 5μ Intermediate layer Thickness 5μ Outer layer (2) Thickness 5μ Wrap film evaluation Γ Film tear strength: longitudinal tear strength is 35
Kg/cm, and the tear strength in the transverse direction is 110 Kg/cm, which is sufficient for practical use. Γ Haze: Measured according to JIS K-6714, and the value is 2.5, which is sufficient for practical use. Γ Cutting property: When cutting continuously in the horizontal direction of the film with a saw blade, the film was cut cleanly. Γ Heat resistance: Curry rice at 120°C was placed in a polypropylene tray and wrapped, but the film did not tear due to heat. Γ Self-adhesiveness: Although the films were pressed together and left to stand, they remained in that state and did not peel off. Γ Puncture resistance: Crab legs were bundled and placed in a tray and wrapped in wrap film, but the film was not torn by the crab legs. Γ Low temperature embrittlement: Put the parsley in a tray, wrap it with wrap film, and put it in the refrigerator at -50℃ for 30 minutes.
After several minutes, I took it out and dropped it from a height of 1 meter, but it did not break. Γ Extensibility: Put an apple with a diameter of 10cm in a tray,
I wrapped the wrap film so that it was stretched by about 20% from its original shape, but it was finished neatly with no wrinkles or shrinkage. Examples 2 to 6 and Comparative Examples 1 to 7 The same experiments as in Example 1 were conducted by changing the raw materials and layer thicknesses of the intermediate layer and both outer layers of Example 1 as shown in the table, and the output We evaluated the rough film.

【table】

【table】

[Table] [Effects of the present invention] In the present invention, specific ethylene-butene-
Since the middle layer is made of 1-hexene-1 copolymer and both outer layers are made of ethylene-vinyl acetate copolymer, each layer is combined to take advantage of the excellent properties of both. An ideal wrapped film with excellent tear strength, haze, cuttability, heat resistance, self-adhesiveness, puncture resistance, low-temperature embrittlement resistance, and extensibility was obtained. In particular, the tear strength and puncture resistance are even better than those using an ethylene-butene-1 copolymer as the intermediate layer, which was conventionally considered to be excellent.

Claims (1)

[Claims] 1. Linear ethylene with a density of 0.910 g/ml or less
A wrap film comprising an intermediate layer made of a butene-1-hexene-1 copolymer and an outer layer made of an ethylene-vinyl acetate copolymer. 2 Linear ethylene-butene-1-hexene-1
A claim in which the copolymer is produced by a gas-phase, low-pressure method using a so-called Ziegler catalyst, which is a catalyst produced by a combination of a transition metal compound of group ~ and an organic metal of group ~ in the periodic table. 1. The wrap film described in 1. 3 Linear ethylene-butene-1-hexene-1
When the copolymer is heated in a fluidized bed reaction zone at a temperature of 10° to 80°C and a pressure of 7000 KPa or less, (a) 0.35:1 to
8.0:1 (total mole of butene-1 and hexene-1, however, the molar ratio of butene-1 and hexene-1 is
(b) at least ethylene, butene-1 and hexene-1 in a molar ratio of 0.5:1 to 2:1)
25 mol % of at least one diluent gas with the formula: Mg _n Ti (OR) _o X _p [ED] _q [wherein R is an aliphatic or is an aromatic hydrocarbon group or COR′,
where R' is an aliphatic or aromatic hydrocarbon group having 1 to 14 carbon atoms, X is selected from the group consisting of Cl, Br, I and mixtures thereof, and ED is an aliphatic or aromatic hydrocarbon group an organic electron-donating compound selected from the group consisting of alkyl esters of acids, aliphatic ethers, cyclic ethers, and aliphatic ketones, m is 0.5 to 56, n is 0.1 or 2, and p is 2 to 116 and q is 2 to 85], the precursor composition is diluted with an inert carrier material and the formula: Al(R _{′ ) d} , f is 0 or 1, and d+e+f=3], and the activation compound is added to a total aluminum to titanium molar ratio of 10:1 to 1 in the reaction zone.
2. The wrapped film according to claim 1, which is produced by a continuous method for producing an ethylene copolymer, characterized in that the ethylene copolymer is used in an amount of 400:1. 4 The ethylene-vinyl acetate resin in the outer layer has a melt index of 0.3 to 3 g/10 min and a vinyl acetate content of 5 to 20% by weight, and the relationship between melting point (MP) and vinyl acetate content (VA) is MP = 114- 1.44VA (MP unit is °C, VA unit is wt%), and the molecular weight distribution (w/n) is less than 4 (where w is the weight average molecular weight and n is the number average molecular weight). 1. The wrap film described in 1. 5. The wrap film according to claim 1, wherein the inner layer is the linear ethylene-butene-1-hexene-1 copolymer according to claim 3, and the outer layer is the ethylene-vinyl acetate copolymer according to claim 4.