JPS63173641A - Polyolefine group heat-shrinkable laminated film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a polyolefin heat-shrinkable laminated film, and more particularly to a heat-shrinkable laminated film with excellent low-temperature shrinkability.

(Prior art) Conventionally, polyvinyl chloride film, -lyethylene blown film, -lyethylene stretched film, polypropylene stretched film, polyamide stretched film, etc. are known as heat-shrinkable packaging materials. In terms of price and ease of disposal after use, 4-lyolefin heat-shrinkable films such as polyethylene and polypropylene are preferred. However, among these, polyethylene heat-shrinkable films can be thermally bonded at relatively low temperatures, and especially in the case of linear low-density I-diethylene heat-shrinkable films, the impact strength of the sealed portion is excellent. Although it has characteristics such as excellent transparency,
The disadvantages are that the film is weak and difficult to package at high speeds. On the other hand, polyethylene heat-shrinkable film
Although it has poor low-temperature thermal adhesion, it has good stiffness and is suitable for packaging machines, so it is used as a heat-shrinkable film made by laminating the two, depending on the purpose.

(Problems to be Solved by the Invention) As mentioned above, a film in which a polyethylene-based heat-shrinkable film and an I-dipropylene-based heat-shrinkable film are laminated has a property that the polyethylene film layer has low-temperature thermal adhesion and burrs. Although it is an excellent heat-shrinkable laminated film that has both the stiffness and stiffness of the film layer, its heat-shrinkability at low temperatures is insufficient, so it is suitable for frozen foods, plastic molded products, and other packaged items that cannot be exposed to high temperatures. It had the disadvantage that it could not be used for packaging purposes.

(Means for Solving the Problems) The present inventors have arrived at the present invention as a result of intensive studies in search of a heat-shrinkable film that eliminates the above-mentioned drawbacks.

That is, in the present invention, the density at 25°C is 0.90 to 0.
93, iil 7cm, melt index 0.
Ethylene polymer consisting of ethylene and α-olefin (hereinafter referred to as having a density of 0.90 to 0.93)
(referred to as ethylene polymer A) 100 to 50% by weight,
Density at 25°C is 0.87-0.91117cm3
, 50% by weight or less of an ethylene copolymer with a melt index of 0.2 to 5 g/10 minutes (hereinafter referred to as polyethylene copolymer B with a density of less than 0.91) is an essential component, and a differential scanning calorimeter is used. Regarding the melting curve measured by (DSC), an ethylene polymer composition having an endothermic area below the melting point (endothermic main peak) of 10°C or less of the total endothermic area was melt-extruded and Is the area shrinkage rate at 90°C after stretching more than 20% more than 20% and the thickness unevenness less than 20? It is obtained by melt-extruding a diethylene-based heat-shrinkable film layer (PE) and a resin mainly composed of propylene, and stretching it 2.0 times or more in both length and width.
This is a polyolefin heat-shrinkable laminated film consisting of a ligropyrene-based shrinkable film layer (PP), which is stable in film formation and stretching, has small thickness unevenness, and has excellent low-temperature shrinkability.

The α-olefins copolymerized with ethylene of the ethylene polymer A having a density of 0.90-0.93 used in the present invention are butene-11 pente/-1, hexene-1,
fart! ten-1, octene-1,4-methyl-pentene-
Preferably, one or more selected from the group consisting of 1, decene-1, undecene-1, and dodecene-1; Polymer B contains ethylene and carbon number 4 to 8.
α-olefins such as butene-1, pentene-1,
Copolymers with hexene-1, hegetene-1, octene-1°4-methyl-pentene-1, etc. are used.

The mixing amount of the ethylene copolymer B having a density of less than 0.91 is preferably 50% by weight or less, particularly 10 to 50% by weight. If less than 50% of the ethylene copolymer is mixed, the improvement in low-temperature shrinkability due to K will not be sufficiently obtained, and if it exceeds 50% of K, the resulting film will have a large blocking property and will have difficulty unwinding the film. If the process does not proceed smoothly and the work efficiency is poor, and in severe cases, adhesion and turning occur on the film surface, resulting in low commercial value.

Other resins such as high-pressure I-lyeethylene, ethylene-vinyl acetate copolymer, ionomer, etc. may be mixed with the PE layer raw material resin to the extent that the purpose of the present invention is not adversely affected.

Furthermore, commonly used additives such as slip agents, anti-blocking agents, antifogging agents, and antistatic agents can be appropriately added to the raw material resin.

The raw material resin for the polypropylene heat-shrinkable film layer PP used in the present invention is a propylene/ethylene copolymer mainly composed of polypropylene, and a thermoplastic polymer that can be mixed with the copolymer to form a film. A mixture of This propylene/ethylene copolymer contains 2 to 10% ethylene, and thermoplastic polymers that can be mixed with the PK layer raw material resin to form a film include ethylene-hinyl acetate copolymer, ethylene -α-olefin copolymers, low molecular weight polyethylene, low molecular weight polypropylene, polybutene, petroleum resins, ionomers, etc. can be used. - Further, the raw material resin of the I-ligropyrene heat-shrinkable film layer PP may contain an antistatic agent, an antioxidant, a slip agent, an antifogging agent, a dye, a pigment, etc., if necessary.

The ethylene copolymer or its composition used for the polyethylene heat-shrinkable film layer as described above has a melting curve measured by a differential scanning calorimeter (DSC) at a temperature 10°C lower than the melting point (endothermic main peak). The film has an endothermic area of 55% or more of the total endothermic area, and can be easily drawn with Chepler over a wide temperature range.Furthermore, the obtained film is effectively oriented, has excellent low-temperature shrinkability, and has a uniform thickness. It has the characteristic of being small. On the other hand, if it is less than 55 inches, uniformity of stretching cannot be easily obtained, and in order to obtain uniformity, if the stretching temperature is raised, the stretching becomes stable, or the orientation cannot be effectively obtained and it is difficult to obtain uniformity at low temperature. Heat shrinkability becomes insufficient.

The measurement using the differential scanning calorimeter described above was carried out on samples 6 to 8r19.
was sealed in an aluminum tube, heated to 190℃ under a nitrogen stream, kept at this temperature for 1 hour, and then heated at about 10℃/m
After cooling to room temperature with i.n., the heating rate was 10℃/m.
In, the melting curve obtained at a sensitivity of 251,697 seconds is determined.

The method for preparing the polyolefin heat-shrinkable laminated film of the present invention involves first producing each of the heat-shrinkable film layers constituting the film separately by a known method, and then stacking them in a dry laminator or other conventional method. The desired constituent layers may be laminated by a lamination method as described above, or an unstretched laminated film extruded all at once from a coextrusion die placed in the desired constituent layer may be stretched by a known method.

When each of the constituent heat-shrinkable film layers is manufactured separately, the polyethylene-based heat-shrinkable film layer can be manufactured by a known method. I will list and explain in detail.

First, a composition consisting of the above-mentioned ethylene polymer A and ethylene polymer B is heated, kneaded, extruded into a tube shape, and cooled and solidified to obtain an unstretched original fabric.

The obtained Chepler-stretched original fabric is fed to a Chepler-stretching apparatus as shown in FIG. At low temperature, expand and stretch simultaneously 2
Perform axial orientation. The stretching ratio does not have to be the same in the length and width directions, but in order to obtain good physical properties such as strength, it is at least 2 times, preferably at least 2.5 times, in both the length and width directions.

The film taken out from the stretching device can be annealed if necessary, and natural shrinkage of the film obtained by annealing can be suppressed.

Further, the method for producing the polypropylene heat-shrinkable film layer may be almost the same as that for the polyethylene heat-shrinkable film layer described above, but the melting temperature and stretching temperature of the raw resin are 180 to 280°C and 80 to 80°C, respectively. 140°C is preferred.

In addition, the method for coextruding and stretching a diethylene heat-shrinkable film layer and a polypropylene heat-shrinkable film layer involves coextruding them in a chain shape from a coextrusion ring-shaped die arranged in a desired layer order, It is cooled and solidified to form an unstretched original fabric.

The obtained tape-shaped unstretched original fabric is supplied to a Chepler stretching apparatus as shown in FIG. 1, for example, and stretched at a stretching temperature ( Simultaneous biaxial orientation is carried out at A0-140°C).

The stretching ratio and annealing can be appropriately selected as in the case of polyethylene resin.

Further, the layer structure of the heat-shrinkable laminated film of the present invention will be explained. The heat-shrinkable laminated film of the present invention has an ethylene-based heat-shrinkable film layer (hereinafter simply referred to as PE).
Advantages such as low-temperature heat shrinkability, low-temperature heat adhesion, and impact resistance of the IJ propylene-based mature heat-shrinkable film (referred to as the PP layer), and mechanical suitability, stiffness, etc. In particular, the heat-shrinkable laminated film of the present invention is characterized by the use of a PE layer with excellent low-temperature heat-shrinkability, but depending on the application, the structure may be changed as follows. It's convenient. However, the laminated film of the present invention is not limited to this, and may have more layers.

(→ Thermal adhesion, impact resistance, low-temperature shrinkability and Pg layer
Strength of P layer When used for gold, pg layer / PP layer
or PE layer/PP layer ZPE layer) When mainly utilizing the low-temperature shrinkability and impact resistance of the PE layer and the stiffness and mechanical suitability of the PP layer, use the PP layer/PE layer or the PP layer/PE layer/
PP Layer (Example) The present invention will be specifically explained below using Examples, but the present invention is not limited thereto.

The measurement items shown in the examples were obtained by the following method: 610 square-cut films with a heat shrinkage rate of 101 in the vertical and horizontal directions were immersed in a glycerin bath at a predetermined temperature for 10 seconds, and the following formula was used: The average value of 10 sheets was used as the value.

Area shrinkage rate=100-AXB MD shrinkage rate±(10-A)XIO TD shrinkage rate=(10-B)XIO However, A, BV! , MD (longitudinal direction) after immersion, TD
(The length unit in the horizontal direction is cfn).

2. Uneven thickness contact type electronic micrometer (Anritsu Electric (copper 306)
The maximum value (Tm, ri, minimum value (T11n), and average value (T) were calculated using the following formula for the chart in the direction of the 1st circle of the chain measured at a full scale of 8 μs F using C type).

However, the arithmetic mean value of the values read from the chart positions corresponding to 10-intervals on the measuring film.

(Example 1) Density at 25°C is 0.9221/eM, melt index 0.8. ! i′/10 min ethylene-butene-
1 copolymer, the main peak temperature of the melting curve determined by DSC is 126°C, and the endothermic area below 116°C is 63.8% of the total endothermic area.
The mixture is melted and kneaded at 70 to 230°C, extruded through an annular die maintained at 230°C, and cooled by sliding on the outer surface of a cylindrical mandrel in which cooling water is circulated, while the outside is cooled by passing through a water bath. A chape-shaped unstretched film having a thickness of about 66 cm and a thickness of 250 μm was obtained. This unstretched film was used as a raw material and was introduced into a biaxial stretching apparatus shown in FIG.
The film was stretched 4 times in length and width at 5 to 105°C. The stretched film was annealed with hot air at 75° C. for 10 seconds in a chip annealing device, then cooled to room temperature, folded, and rolled up.

During stretching, the stability of the chip was good, with no vertical movement of the stretching point or swinging of the chip, and no uneven stretching conditions such as necking were observed.

The obtained stretched film had a thickness of 16 μm, an area shrinkage rate at 90° C. of 31.5%, and a thickness unevenness of 15 inches.

After applying corona treatment to one side of the stretched film and setting the surface wetting tension to 40 dynes, corona treatment was applied to one side of a 15μ thick propylene heat-shrinkable film (trade name Polyset, manufactured by Kankojin). Dry lamination using Lyester-based two-component adhesive (product name: ff-) 503 and CAT-10: Toyo Morton (made of copper) so that the treated surface and each corona-treated surface adhere to each other. A heat-shrinkable polyolefin laminated film was obtained by baking.

The area shrinkage rate of this laminated film at 90°C is 30,
It was 5chi.

Cut out a film of 30c IR120c* lengthwise and widthwise from this film, make a bag by sealing on three sides with the polyethylene layer facing each other, and make a bag of 17c! After enclosing a set of RX 13 m x 6 glass cracked building blocks, it was passed through a shrink tunnel in which hot air at 110° C. was blown for 10 seconds. If the package is in good condition and is in close contact with the bulging part,
No change was observed in the packaged items.

Example 2 Low-density polyethylene with a density of 0.9201/cm3 at 25°C and a melt index of 2.0.9/10 minutes (trade name: Ultzex 202OL, manufactured by Mitsui Petrochemical) 35% by weight, 25°C The density at is 0.923
/i/cm3, melt index is 0.8.9/10
Low-density polyethylene (product name: NEOSEX 200)
6H1 made by Mitsui Petrochemicals) 35% by weight and a density at 25°C of Q, 904p/cya ultra-low density polyethylene (
Product name: Nymph Bolimaer 〇N2002, manufactured by Sumitomo Chemical) 3
0% by weight was melt-kneaded at 200 to 250°C and extruded downward through an annular die maintained at 250°C. The main peak temperature of the DSC melting curve of this molten mixture was 12
At 0℃, the endothermic area below 110℃ is 6 of the total endothermic area.
It was 0.7chi. The diameter of the slit of the annular die is 75
For parrots, the slit gap was 0.8 m. The extruded molten Chague-like film was slid on the outer surface of a cylindrical mandrel with an outer diameter of 66 mm installed directly below the die, inside of which cooling water at 20°C was circulated, while the outer surface was passed through a water tank. The mixture was cooled with water and cooled to room temperature, and then taken out to obtain a tape-shaped unstretched film with a diameter of about 65 cm and a thickness of 190 μm.

This unstretched film was introduced into a biaxial stretching apparatus shown in FIG. 1 as a raw material and subjected to expansion stretching. The voltage and current of the annular infrared heater of the preheater 4 were adjusted to set the film temperature at the outlet of the preheater to 65°C.

Main heating device 508 annular infrared heaters are divided into four sections, each voltage and current are adjusted to heat the film, and low speed egg roll 2 is supplied with air flowing along the chain from below the main heating device. Pressurized air was fed into the tubular film between .

The tubular stretched film thus obtained is folded and pulled out from the stretching machine, guided to a tape annealing device, where hot air at 75°C is blown from a heating cylinder into the tubular shape.
After annealing for 10 seconds, it was cooled to room temperature in a cooling cylinder, folded again, and taken out to remove the spring color.

The obtained film had a thickness of 20.8 μm and a thickness unevenness of 12 cm.
After corona treatment was applied to both sides of this stretched film and the wetting tension of the surface was set to 39 dynes, a commercially available thickness of 15
A polypropylene heat-shrinkable film (trade name: Polyset, manufactured by Chimkojin Co., Ltd.) of μ is coated with polyester two-component adhesive (trade name: Atocoat 503 and cat (O: Toyo Morton (copper)) and dried. Lamination was performed to obtain a polyolefin heat-shrinkable laminated film.

The heat shrinkage rate of this laminated film at 85°C is 16
．． It was 7 inches long, 18.0 feet wide, and had an area shrinkage rate of 31.7%.

Approximately 2 inches of raw broiler chicken was prepackaged using this film by a fusing seal method, and then passed through a commercially available shrink tunnel in which hot air at 110° C. was blown for about 5 seconds. The film was packaged tightly and there was no particular change in the chicken meat.

Since the laminated film has a polypropylene film layer, it is strong and easy to work at the time of packaging, and the package can be easily transported during shrink wrapping.

Example 3 Density at 25°C is 0.9201/cm3, mek)
(Linear low-density polyethylene with an index of 2.0 and lil/10m1n (Product name: Urtozex 2020
L: Mitsui Petrochemical) 40 parts by weight, density at 25°C 0.923 g/m2, melt-in, II Fuchs 0.89710 min linear low density polyethylene (product name:
Neozex 2006H) 40 parts by weight and ultra-low density ethylene with a density of 0.88 g/cm3 at 25°C (trade name: Tafmer A-4085: manufactured by Mitsui Petrochemicals)
The intermediate layer is a linear polyethylene copolymer mixture consisting of 20 parts by weight, and the crystalline glopyrene-ethylene random copolymer containing 3.5% ethylene is arranged as the innermost layer and the outermost layer. The innermost layer from the coextruded annular die,
The middle layer and the outermost layer were melt-extruded to a total thickness of 180μ, 45μ, 90μ, and 45μ, respectively, and cooled and solidified in the same manner as in Example 2 to produce an unstretched film, and then stretched into a tubular shape with three times the length and width. After stretching, the film was annealed at 7°C to obtain a folded roll of heat-shrinkable film. The obtained film had a thickness of 20 μm, a thickness unevenness of ±5 inches, and a thickness of 8
Thermal shrinkage rate at 5℃ is 16.2 inches long, 16.8 inches wide,
The area shrinkage rate was 30.3 inches.

This laminated shrink film is wrapped around 19511X 10.5
Three volumes of video cassettes each having a size of 0 x 2.7 cIN were prepackaged and passed through a Scherlinck tunnel at 120°C for 5 seconds.

The packaging was well finished and the product had a good appearance.

Because the film is stiff and has good sealing properties, high-speed packaging is possible.

Comparative Example 1 Density at 25°C is 0.918, il/cm3
, melt index 1. O, F/10 min ethylene-butene-1 copolymer, which has a main peak temperature of 120°C on the melting curve by DSC and an endothermic area of 110°C or less that is 49% of the total endothermic area. The polymer was subjected to reverse stretching and annealing using the same method and conditions as in Example 1.

At such low temperatures, the stretched chain swayed, and a necking phenomenon was also observed in the stretched portion. When the stretching temperature was lowered to increase the stability of the stretched stretch, necking became more severe and non-uniformity increased. When the stretching temperature was raised to 103 to 108° C. to alleviate necking, the stretched tube exhibited severe up-and-down movement and rocking, and the stability deteriorated.

The stretched film obtained at a stretching temperature of 103 to 108°C is
The average thickness was 16 μm, the thickness unevenness was 27 inches, and the area shrinkage rate at 90° C. was 15.4 inches.

This film was subjected to corona treatment on a polypropylene heat-shrinkable film (trade name: Polysect, manufactured by Sekoto) with a thickness of 15 μm, and dry lamination treatment was performed in the same manner as in Example 1, but the flatness of the film was poor. As a result, the bonded surface had many wrinkles, making it impractical.Also, the heat shrinkage rate of the obtained laminated film was 13.3 in the vertical direction.
%, width was 14.5 inches, and area shrinkage was 25.9 inches.

(Functions and Effects) Since the polyolefin heat-shrinkable laminated film of the present invention has an ethylene polymer layer having a specific DSC curve, it can be stretched under a wide range of conditions and the stretching conditions can be easily selected, resulting in high orientation. It is possible to obtain a film with a polypropylene-based heat-shrinkable film layer, and it has excellent low-temperature shrinkability. Especially, films to which ultra-low density polyethylene is added have even better low-temperature shrinkability. It has better low-temperature shrinkability than conventional polyolefin heat-shrinkable laminated films, and is stiff due to the presence of this one olefin layer.Furthermore, products with a polyolefin heat-shrinkable film layer placed on the required surface are Due to its slip property, it can be transported smoothly. As described above, the laminated film of the present invention can be used as a packaging material suitable for packaging plastic molded products, raw meat, and frozen foods that are deteriorated by high-temperature treatment.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a biaxial stretching apparatus used in Examples. A...Stretching device Figure 1 1...Unstretched film 2...Low speed Nirag roll 3゛°°High speed Nip roll 4...Preheater 5...Main heater 6...Cooling air ring 7.・Folding roll details

Claims (1)

[Claims] 1. Density at 25°C is 0.90 to 0.93 g/cm
^3, 100 to 50% by weight of an ethylene polymer (A) consisting of ethylene and α-olefin with a melt index of 0.2 to 3.0 g/10 minutes, and a density of 0 at 25°C.
．． Ethylene copolymer (B) 50 with a melt index of 87 to 0.91 g/cm^3 and a melt index of 0.2 to 5 g/10 minutes
Weight% or less is an essential component, and differential scanning calorimeter (DSC)
), an ethylene polymer composition whose endothermic area at a temperature 10°C lower than the melting point (main endothermic peak) is 55% or more of the total endothermic area was melt-extruded, and the melting curve was 2.0 times or more in each length and width. A polyethylene heat-shrinkable film layer (PE) with an area shrinkage rate of 20% or more at 90°C and a thickness unevenness of 20% or less and a resin whose main component is propylene are melt-extruded, and the length and width are 2.
A polyolefin heat-shrinkable laminated film comprising a polypropylene heat-shrinkable film layer (PP) obtained by stretching 0 times or more. 2. The component α-olefin of the ethylene polymer (A) consisting of ethylene and α-olefin is selected from the group consisting of butene-1, pentene-1, hexene-1, and octene-1,4-methylpentene-1. The polyolefin heat-shrinkable laminated film according to claim 1, characterized in that the polyolefin heat-shrinkable laminated film contains at least one type of polyolefin. 3. Polyethylene heat-shrinkable film layer (PE) and polypropylene-based heat-shrinkable film layer (PP) are PE/P
The polyolefin heat-shrinkable laminated film according to claim 1, characterized in that P/PE are laminated in this order. 4. Polyethylene heat-shrinkable film layer (PE) and polypropylene-based heat-shrinkable film layer (PP) are PP/P
The polyolefin heat-shrinkable laminated film according to claim 1, wherein the polyolefin heat-shrinkable laminated film is laminated in the order of E/PP.