JPH0376647A - Multilayer film for packing food - Google Patents

Abstract

PURPOSE:To enhance heat sealability and heat seal strength by laminating a heat-seal layer composed of a specific ethylene/butene-1/hexene-1 copolymer to a base material layer through or not through an intermediate layer. CONSTITUTION:A heat-seal layer composed of an ethylene/butene-1/hexene-1 copolmer having density of 0.91g/ml or less is laminated to a base material layer through or not through an intermediate layer. The ethylene/butene-1/ hexene-1 compolymer to be used having density of 0.910g/ml or less is obtained by polymerizing ethylene, butene-1 and hexene-1 in the presence of a ziegler catalyst or chromium type catalyst consisting of a transition metal compound being a main catalyst, an organometal compound being a cocatalyst and a carrier under medium or lower pressure. By this method, even when impurity is present, heat sealability is improved and strong heat-seal strength can be kept even when a heat-sealed surface is exposed to high temp.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a multilayer film for food packaging.

More specifically, the heat-sealing surface of food packaging bags made with this film has good heat-sealing properties even in the presence of contaminants, and has strong heat-sealing strength even when the heat-sealing surface is exposed to high temperatures. The present invention relates to a multilayer film for meat packaging that can be used for meat packaging.

[Conventional technology] Conventionally, raw meat, processed meat, bone-in portions, fish, butter, cheese, etc. have irregular and inconsistent shapes and vary in size, so it has been difficult to find a way to finally adapt them to these shapes. Heat-shrinkable packaging bags are widely used industrially for the purpose of eliminating oxygen inside the packaging bag, extending the shelf life of food, and reducing the volume required for storage. In addition, the packaging material that makes up this heat-shrinkable packaging bag is required to have oxygen barrier properties in order to prevent meat from spoiling due to contact with oxygen, and for this reason, a base material with low oxygen permeability is required. ing.

Furthermore, these base materials usually have poor heat-sealing properties, or even if they can be heat-sealed, they must be kept at a relatively high temperature of 130-160°C, and at such high temperatures, the contents may deteriorate or the base material may deteriorate. The material film is partially distorted,
These base layers are undesirable because they lose commercial value, become partially thin, have weak heat-sealing strength, weaken the base material strength itself, and weaken impact resistance. It is used as a multilayer film by providing a separate heat-sealing layer.

As the resin used for the heat-sealing layer, high-pressure low density polyethylene, ethylene-vinyl acetate copolymer, ionomer, polypropylene, high-density polyethylene, ethylene-α-olefin copolymer, etc. are used. High-pressure low-density polyethylene has a heat welding temperature of around 110°C and can be boiled while containing the contents, and has excellent adhesive strength and stability, but it may have a slight odor. In addition, pinholes may occur at the bent portions due to repeated bending, and air may flow in through the bent portions, causing the food contents to spoil.

Ethylene-vinyl acetate copolymer has excellent low-temperature sealing properties, but when sterilized at high temperatures, the odor increases and the bending pinhole resistance, hot tack properties, heat resistance, and heat sealing strength at high temperatures are insufficient. do not have. Ionomers have excellent heat-sealing strength and hot tack properties, but their adhesive strength is slightly inferior, their extrusion processability is poor, fish eyes and bumps are likely to occur on the film, and the film is stiff when made into a laminated film. When vacuum packaging heavy items such as chilled meat and transporting them, the hardness of the package can rub against the hardness of the package, making it easy for pinholes to form and causing vacuum return. In addition, the presence of water may cause hydrolysis, so it cannot be said that the water resistance is sufficient. Furthermore, mucus adheres to the extrusion die during processing, making processing extremely difficult.

Although polypropylene has strong heat-sealing strength, it has processing disadvantages such as thermal decomposition, easy molecular weight reduction, and large neck-in during T-die processing, and the heat-sealing temperature is too high at 150°C, making it difficult to handle. Its range of use is limited due to its poor cold resistance. Although high-density polyethylene has excellent heat-sealing strength, it has poor low-temperature heat-sealability, and when T-die processing is performed, neck-in is large and workability is poor.

Ethylene-α-olefin copolymers have a heat sealing temperature of 80 to 130°C, which can be selected from a wide range of temperatures depending on the grade, and they have excellent heat sealing strength and impact strength. The heat sealing strength is not sufficient when there is fat content such as lard on the sealing surface, that is, the heat sealing strength is not sufficient for contaminants. The materials used for this purpose have advantages and disadvantages, and none are yet satisfactory.

[Problems to be Solved by the Invention] The present inventor studied the required performance as a material for the heat seal layer of a multilayer film for food packaging, and found that the following performance was required, and found a material that satisfies this. ,
The present invention has been completed.

■Low heat-sealing temperature ■Strong heat-sealing strength at high temperatures ■Strong heat-sealing strength even when heat-sealed parts are contaminated with lard and other fats generated from meat ■Odorless ■Safe for food hygiene - Performance does not change due to the presence of moisture - Pinholes do not occur due to bending - Excellent low-temperature impact properties - Excellent hot tack properties [Means for solving the problem] The present inventors: As a result of intensive research, we selected a polymer from among many polymers that satisfies the performance required for the heat-sealing layer of the multilayer film for food packaging, and as a result of experiments, we found a recently developed polymer with a density of 0. 910g/
It was discovered that an ethylene-butene-1-hexene-1 copolymer having a particle size of mβ or less has the corresponding performance, and the present invention was completed. That is, the present invention provides an ethylene-based material having a density of 0.910 g/mI2 or less in the base material layer with or without an intermediate layer.
This is a multilayer film for food packaging, characterized in that a heat seal layer made of a butene-1-hexene-1 copolymer is laminated thereon.

In the present invention, the base material layer is a material that has a low oxygen permeability so that mainly atmospheric oxygen permeates into the packaging bag and does not cause spoilage of meat, and has heat resistance, tensile strength, impact resistance, and low temperature properties. A base material layer consisting of a single layer or multiple layers made of materials with excellent properties, and the materials constituting these layers include polypropylene, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, nylon 6, nylon 66, nylon. 7. Nylon 10. Nylon 111, Nylon 12, Nylon 610. These include polyethylene terephthalate, polyethylene terephthalate-isophthalate, polybutylene terephthalate, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polycarbonate, etc., and particularly preferred are polyamide, polyvinylidene chloride, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, and polyester. , polyvinylidene chloride is most suitable.

When the base material layer is multi-layered, it can be used in combination with the above resin layer with low oxygen permeability.Other resin layers include high-pressure low density polyethylene, medium density polyethylene, ultra low density polyethylene, high density polyethylene, It can be selected from ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, ionomer polybutene-1, poly-4-methyl-pentene-1, and the like. Further, if necessary, paper, cellophane, metal foil, etc. may be added as a single component layer.

In the present invention, the intermediate layer is a layer installed between the base material layer and the heat-sealing layer, and is provided mainly to promote adhesion between the base material layer and the heat-sealing layer, and is provided if the adhesiveness is sufficient. There's no need. For the intermediate layer, adhesive resin such as ethylene-acrylic acid ester copolymer,
Ethylene-vinyl acetate copolymer, ionomer, low-crystalline ethylene-α-olefin copolymer, conjugated diene-aromatic vinyl copolymer, high-pressure low-density polyethylene, medium-density polyethylene, linear ethylene-α-olefin It is selected from copolymers, acid-modified products, glycidyl-(meth)acrylic-modified products, N-substituted maleimide-modified products, etc.

The ethylene-butene-1-hexene-1 copolymer having a density of 0.910 g/ml or less used in the present invention can be prepared using a known method, that is, using a transition metal compound (compounds such as titanium or vanadium) as a main catalyst; Ethylene, butene-1, and hexene-1 in the presence of an organometallic compound (e.g., organoaluminium), a carrier (e.g., oxide of silicon, titanium, magnesium, etc.) as a Ziegler catalyst, a chromium-based catalyst, etc. as cocatalysts. It is obtained by polymerizing under medium or low pressure.

Polymerization can be carried out in various ways, such as slurry polymerization, gas phase polymerization, and high temperature solution polymerization. A particularly preferred method is that the linear ethylene-butene-1-hexene 1, #: polymer is heated in a fluidized bed reaction zone at a temperature of 10' to 8°C. OOO
At a pressure below K P a, (a) 0.35: 1
~8.0: l (total mole of butene-1 and hexene-1, provided that the molar ratio of butene-1 and hexene-1 is 0.5
A gas mixture containing at least 25 mol % of ethylene, butene-1 and hexene-1 (b) and at least 25 mol % of at least one diluent gas in a molar ratio of ethylene to Mg-Ti (OR ) llL [ED] q [wherein,
R is an aliphatic or aromatic hydrocarbon group having 1 to 14 carbon atoms or COR', where Ro is 1 to
an aliphatic or aromatic hydrocarbon group having 14 carbon atoms, X is selected from the group consisting of CI, Br, I and mixtures thereof; an organic electron donating compound selected from the group consisting of 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 from 2 to 85], diluting said precursor composition with an inert carrier material and having the formula: AI (R' ), tX', L [where Xo is C1 or OR'', Ro and R''
is a saturated hydrocarbon group having 1 to 14 carbon atoms, e is O to 1.5, f is O or 1, and d+e+f=3. activate it,
A process for the continuous production of ethylene copolymers, characterized in that the activation compound is used in an amount such that the molar ratio of total aluminum to titanium in the reaction zone is from 10:1 to 400:1. It is published in Japanese Unexamined Patent Application Publication No. 1983.
It can be made by the method described in detail in Japanese Patent No. 230011.

In the present invention, the thickness of the multilayer film is 20~100μ
and 40 to 80μ is suitable.

- The thickness of the heat-sealing layer must be at least 5μ; if it is less than this, the low-temperature sealing properties will be insufficient, and even if heat-sealing is possible at low temperatures, the adhesive strength will be weak, weak stress,
The heat-sealed surface peels off immediately upon impact, which is undesirable.

In the present invention, foods include raw meat, processed meat, bone-in portions, fresh fish, fish fillets, shellfish, butter, cheese, vegetables, fruits, peanuts, tea, coffee cocoa, ramen, potato chips, mushrooms, rice cakes, It means rakkyo, umebashi, soba, udon, konjac, tofu, jelly, popsicle - fruit juice, sugar, etc.

The multilayer film of the present invention can be produced by co-extruding the resin constituting the base material layer and the resin constituting the heat-sealing layer, or by forming one resin into a film in advance and extruding the other resin thereon and laminating or bonding. It is made by laminating layers. If heat shrinkability is required, the multilayer film is heated to a temperature at which it can be stretched, and stretched at least 1.5 times or more in both the longitudinal and transverse directions.

As the stretching method, either a tenter method or an inflation method is possible, but the inflation method is preferable because it is easy to make the heat shrinkability in the longitudinal direction and the transverse direction the same.

The resins constituting the multilayer film of the present invention include heat-resistant stabilizers, antioxidants, colorants, pigments, carbon black, lubricants, processability improvers, eye mucus prevention agents, slip agents, anti-blocking agents, antifogging agents, Antistatic agents, nucleating agents, etc. may be added depending on the purpose and use. Examples are shown below, but examples of improvements that utilize the technical idea of the present invention do not fall within the scope of the rights of the present invention. be.

[Example] 100 parts of vinylidene chloride-vinyl chloride copolymer (vinylidene chloride 80% by weight, vinyl chloride 2
Prepare a composition consisting of 0% by weight) and 1 part of epoxidized soybean oil, prepare an ethylene-ethyl acrylate copolymer (80*% by weight of ethylene, 20% by weight of ethyl acrylate) as a resin for the intermediate layer, and heat seal. Ethylene-butene-1-hexene-1 copolymer (70% by weight of ethylene, 110% by weight of butene, 120% by weight of hexene) was used as the resin for the layer.
% by weight) was prepared.

Using these resins, blown films were manufactured by air cooling using the following equipment and processing conditions.

(1) Extrusion equipment: ■ Braco blown film processing equipment diameter 40mm x 3 units L/D28 (2) Annular three-layer die: φtsomm die gap: 1. Omm (3) Cold button device with single lip straight and conical collar (4) Discharge amount: 45 kg/h
r (5) Dice temperature = 180℃ (6) Blow ratio: 2.5 Embroidered film base layer thickness 10μ Intermediate layer thickness lOμ Heat seal layer thickness 10μ Aging 1 bag of raw color laminated film in longitudinal direction It was stretched 3 times in the horizontal direction and 3 times in the transverse direction.

, of the film! - Film tear strength: The tear strength in the longitudinal direction is 80 kg and the tear strength in the horizontal direction is 230 kg, which is sufficient for practical use.

- Haze: Measured according to JIS K-6714, and the value is 2.5, which is sufficient for practical use.

・Puncture resistance Two crab legs were tied together and placed in a heat-shrink packaging bag (20 cm long and 15 cm wide) made from laminated film and vacuum packed, but the crab legs did not tear the film.

・Low-temperature embrittlement: Place 1 kg of beef in a heat-shrinkable packaging bag (20 cm long, 15 cm wide) made from laminated film, vacuum pack it, put it in a -50°C refrigerator, take it out after 30 minutes, and pack it to a height of 1 m. I dropped it from the ground, but it didn't break.

・Contaminant heat-sealing property: The heat-sealing strength was measured after lard was made to adhere to the heat-sealing surface of the laminated film and heat-rolled.

23℃: 2800g/15mm 80℃: 2300g/15mm 90℃: 2200g/15mm The above numbers are practical enough. In particular, 90℃ Shows good results even at high temperatures.

Sex: Approximately 7 kg of chilled beef is vacuum-processed. Two wrapped packages as Danbo and its packaging. Dip the product in water three times from a height of 60 cm. After dropping it by hand, use the energization method. Check the bag for pinholes However, pinholes occurred in 50 bags. I counted the number of bags. ○, durable Good pinhole properties.

After making bags using the above-mentioned laminated film with bottle nail resistance and hot tack properties using a vertical billow type automatic bag making and filling machine (manufactured by Yojima Kikai Co., Ltd.), the size of one bag is 14 cm 820 cm, and the bag making speed is 90. When the bags were filled with 200 g of sugarcane at a rate of 200 g per minute, no peeling was observed at the heat-sealed portions of any of the bags.

・Heat seal strength at high temperature: 90' of heat seal part
The heat seal strength in C was measured and was 3100 g/15 mm, so it is sufficiently practical.

* 1 * 2 * 3 * 4 * 5 * 6 The weight percent in the copolymer of ethylene, butene-1, and hexene-1 is 70.2o and 10, respectively, and the density is 0.9
10g/mI2, Ml is 1.0 copolymer ethylene, butene-1, hexene-1 copolymer has a weight percentage of 70.15.15 and a density of 0.9.
10g/mj2, Ml is 1.0 copolymer ethylene, butene-1, hexene-1 copolymer with weight% of each 70. ．． 10°20 and the density is 0
．． Copolymer O having 910 g/mI2 and Ml of 1.0 = tear strength in the longitudinal direction of 50 kg/cm or more, tear strength in the transverse direction of 150 kg/cm or more, and is sufficiently practical.

○ = Measured according to JIS K-6714, and the value is 5 or less.

○=The film was not torn by crab legs according to the test method described in Example ■.

*70=The bag did not break according to the test method described in Example I.

X = Broken bag.

*80=The heat seal strength at 90'C was 400 g/15 mm or more according to the test method described in the example work.

x=400g715mm or less.

*90 = Pinhole occurrence was 0 out of 50 bags according to the test method described in Example ■.

× = 1 or more occurrences of upper pinhole.

*lO○ = No peeling was observed by the test method described in Example Work.

× = Peeling was observed in some parts.

*110 = The heat seal strength of the heat seal portion at 90°C is 700 g/15 mm or more.

X = 700 g / 15 mm or less.

[Operations and Effects of the Present Invention] In the present invention, a specific ethylene-butene-1-hexene-1 copolymer is used as the material for the heat-sealing layer, so a multilayer film for food packaging made with this copolymer will not spoil food. Suppresses oxygen permeation, improves tear strength and impact strength (l-), provides good heat sealing properties even when foreign matter is present on the heat sealing surface, and provides strong heat sealing even when the heat sealing surface is exposed to high temperatures. It maintains its strength and solves problems that could not be solved with conventional packaging bags, making it particularly useful as packaging bags for raw meat and fresh fish.

Claims (5)

[Claims] (1) The density of the base material layer is 0.0 with or without an intermediate layer.
A multilayer film for food packaging, characterized in that a heat seal layer made of an ethylene-butene-1-hexene-1 copolymer of 910 g/ml or less is laminated thereon. (2) The base layer is composed of a single layer or a multilayer selected from polypropylene, polyvinyl chloride, polyvinylidene chloride, polyamide, polyester, polyvinyl alcohol, and ethylene-vinyl alcohol copolymer. The multilayer film for food packaging according to claim 1. (3) A claim characterized in that the intermediate layer is composed of a polymer layer selected from ethylene-acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, ionomer, and low-crystalline ethylene-α-olefin copolymer. Item 1. Multilayer film for food packaging according to Item 1. (4) A so-called catalyst in which a linear ethylene-butene-1-hexene-1 copolymer is produced by a combination of a transition metal compound of Groups IV to VIII and an organic metal of Groups I to III in the periodic table. The multilayer film for food packaging according to claim 1, which is produced by a gas phase/low pressure method using a Ziegler catalyst. (5) The linear ethylene-butene-1-hexene-1 copolymer was heated in a fluidized bed reaction zone at a temperature of 10° to 80°C and
At a pressure of ,000 KPa or less, (a) 0.35:1 ~
8.0:1 (total moles of 1-butene and 1-hexene,
However, the molar ratio of butene-1 and hexene-1 is 0.5:1 to
A gas mixture containing ethylene, butene-1 and hexene-1 in a molar ratio of 2:1) to ethylene and (b) at least 25 mol % of at least one diluent gas with the formula: Mg_mTi(OR)_nX_p[ED ]＿q[in the formula,
R is an aliphatic or aromatic hydrocarbon group having 1 to 14 carbon atoms or COR', where R' is 1 to
an aliphatic or aromatic hydrocarbon group having 14 carbon atoms, X is selected from the group consisting of Cl, Br, I and mixtures thereof; an organic electron-donating compound selected from the group consisting of ethers, cyclic ethers, and aliphatic ketones, m is 0.5 to 56, n is 0.1 or 2, and p is 2 to 116; , q is from 2 to 85], said precursor composition being diluted with an inert carrier material and having the formula: Al(R')_dX '_eH_f [where X' is Cl or OR'', R' and R'' are saturated hydrocarbon groups having 1 to 14 carbon atoms, e is 0 to 1.5, and f is 0 or 1 and d+e+f=3] completely activated with an organoaluminum compound having the following:
A process for the continuous production of ethylene copolymers, characterized in that the activation compound is used in an amount such that the molar ratio of total aluminum to titanium in the reaction zone is from 10:1 to 400:1. The multilayer film for food packaging according to claim 1.