JPS58160147A - Coextruded multilayer 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 The present invention provides a coextruded multilayer film made of ethylene resin,
More specifically, we produce packaging bags for medium and heavy items with excellent impact resistance, opening properties, and heat-sealing strength by using high-pressure low-density polyethylene as the core material and laminating ethylene $α-olefin copolymer layers on both sides. The present invention relates to a coextruded multilayer film suitable for.

Traditionally, paper bags have been used to package relatively heavy items such as rice, wheat, feed, cement, fertilizer, sugar, etc. Paper bags have excellent rigidity and loadability, but have poor tear resistance and Because of its poor impact resistance and water resistance, some use high-pressure low-density polyethylene (hereinafter referred to as HPPK), which has excellent tear resistance and water resistance.
) films are used as packaging bags for medium and heavy items. However, HPPI: 'The film has poor impact resistance, so it requires a certain degree of thickness.
It also has the disadvantage of poor opening properties. On the other hand, high-density polyethylene (hereinafter sometimes referred to as HDPK) film has excellent rigidity, but is slippery and has poor loading properties. On the other hand, so-called linear low-density polyethylene (LL
A film made of a copolymer of ethylene and α-olefin called DPI (sometimes called DPI) has been used as a general packaging film in recent years because of its excellent transparency, tear strength, impact strength, and low-temperature heat sealability. is in the spotlight. However, although such LLDPE film is excellent as a general packaging film, when used for packaging medium and heavy items, the strength of the heat-sealed portion is surprisingly low.
It has been found that for use in the same purpose, a thickness greater than that of the HPP'E film is required. Therefore, the present inventors investigated a film suitable for packaging medium and heavy items that has excellent impact resistance, opening properties, and heat seal strength, and found that HPPK
It was found that a coextruded multilayer film in which LLDPI films were laminated on both sides of a PP film was suitable for this purpose, and the present invention was achieved.

That is, the present invention has a melt flow rate of 0.1 to 10
g/10m1n and density 0.920 to 0.940
A melt flow rate of 0.1 to 1 is applied to one side of the core material made of high-pressure low-density polyethylene (A) in the range of g/cm3.
0g/10min% density 0.920~0.940g 7cm3 and melting point 115~130
°C copolymer (B) layer of ethylene and α-olefin having 4 to 20 carbon atoms, melt flow rate 0.1 to 10 g/lQmin, density 0.910 to 0.930 g 7 cm3 on the other side. and melting point 115 to 1
To provide a coextruded multilayer film suitable for packaging medium and heavy goods, characterized by laminating layers of a copolymer (C) of ethylene at 30°C and an a-olefin having 4 to 20 carbon atoms. It is something.

The high-pressure low-density polyethylene (A) used for the core material of the coextruded multilayer film of the present invention is melt flow ray) 0.
1 to 10 g/1.0m1n and density 0.920
It is an ethylene polymer obtained by radical polymerizing ethylene in the range of 0.940 g to 7 cm3 under high pressure. Melt flow rate is 0.1 g710m
If it is less than 1n, the melt viscosity is high and the moldability is poor;
If it exceeds g/10 m1n, the melt viscosity is low, the moldability is poor, and the mechanical strength is reduced, so it is not preferable.

If the density is less than 0.920 g/ate3, the rigidity will be low and the film will be soft, so it is not preferable.
．． If it exceeds 940 g/csj', the mechanical strength, particularly the impact strength, decreases, which is not preferable. The melt flow rate in the present invention is a value measured according to ASTM D 1238, E. In addition, the high-pressure low-density polyethylene (A
) is not limited to ethylene homopolymers, but also small amounts of 10
A copolymer with vinyl acetate of up to % by weight may also be used.

Ethylene used on one side of the coextruded multilayer film of the present invention.
The α-olefin copolymer (B) has a melt flow rate of 0.1 to 10 g/I Qmin, preferably 0.1 to 5 g/10 m1n%, and a density of 0.920.
to 0.940 g 101t3, preferably 0.9
25 to 0.940g/3 and melting point 115 to 1
It is a copolymer of ethylene and an α-olefin having 4 to 20 carbon atoms, preferably an α-olefin having 6 to 18 carbon atoms, at 30°C, preferably 120 to 130°C. Melt flow rate is 0.1, g/10m1n
Anything less than 10g has a high melt viscosity and poor moldability.
/10 min is undesirable because the melt viscosity is low, the moldability is poor, and the mechanical strength is also reduced. If the density is less than 0.920 g/cytt3, the rigidity of the film will decrease, blocking will easily occur when it is made into a bag, and the heat sealing strength will decrease, so it is not preferred. If the density exceeds 0.940 g/att3, the low-temperature heat-sealability and impact strength will be poor, and the transparency will also be impaired, which is not preferable. Those with a melting point of less than 115°C have poor heat resistance, tend to block when made into bags, and have poor opening properties. Those with a melting point exceeding 130°C have poor low-temperature heat sealability. The melting point in the present invention refers to a heating rate of 10°C/10°C measured by a differential scanning calorimeter (DSC).
This is the highest temperature at a point showing a sharp endothermic peak determined from the endothermic curve at min. Ethylene α used in the present invention
-Olefin copolymers (2) and (0) have one or more, often two to five, sharp endothermic peaks. a- having 4 to 20 carbon atoms copolymerized with ethylene;
Specifically, the olefin is 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-tetradecene, 1-octadecene, or a mixture thereof. Those copolymerized with propylene are not preferred because they have poor mechanical strength and heat seal strength. In particular, copolymers with α-olefins having 6 or more carbon atoms are preferred because they have excellent impact resistance.

Ethylene/α-olefin copolymer (B
) and (phrase) are obtained by polymerizing ethylene and a-olefin in a ratio that gives the required density by a so-called medium-low pressure method using a transition metal catalyst.In this case, a desired melt flow rate is obtained. For this purpose, a molecular weight regulator such as hydrogen may be used. Polymerization can be carried out by various methods such as slurry polymerization, gas phase polymerization, and high-temperature solution polymerization.

The ethylene/α-olefin copolymer (0) used on the other side of the coextruded multilayer film of the present invention has a melt 70-rate of o, i to 10 g/I Qmin, preferably 0.1 to 5 g/10 m1n%. Density 0.910 to 0.9 s o g/Cttt', preferably 0.91
0 to 0.925 g/Crjl' and a melting point of 115 to 160°C, preferably 115 to 125°C, and an α-olefin having 4 to 20 carbon atoms;
Preferred is an α-olefin copolymer having 6 to 18 carbon atoms.

If the melt flow rate is less than O-1 g/10 m1n, the melt viscosity is high and the moldability is poor, and the melt flow rate is less than 10 g/1
If it exceeds 0 min, the melt viscosity is low, the moldability is poor, and the mechanical strength is also reduced, which is not preferable. If the density is less than 1,910g/cIM3, the film surface tends to become sticky and there is a risk of blocking, so it is undesirable.If the density exceeds 0.950g/cI113, there is little impact strength improvement effect and it should be loaded in bags. It is not desirable because it is slippery when you do it. Those with a melting point of less than 115°C have poor heat resistance, and those with a melting point of more than 130°C are undesirable because the impact strength of the film decreases.

The molecular weight distribution of the ethylene/α-olefin copolymer used in the present invention is not particularly limited, but one with a narrow molecular weight distribution, for example, a ratio of weight average molecular weight/number average molecular weight determined by gel permeation chromatography of 6 It is preferable to use the following, since it is possible to obtain a coextruded multilayer film having excellent impact resistance and transparency.

The thickness of each layer of the coextruded multilayer film of the present invention is +, ), 9, 4. Limited Awagaika 1, Ah, Nya・ 1
1. In order to obtain a film suitable for packaging medium and heavy goods with well-balanced strength and impact resistance, ethylene/α-olefin copolymer (B)/high pressure low density polyethylene (A)/ethylene/α - The thickness of the olefin copolymer (C) is preferably 5 to 30μ/20 to 70μ/20 to 70μ, particularly 10 to 20μ/40 to 60μ/
Preferably, the thickness is in the range of 40 to 60μ.

If the thickness of the ethylene/α-olefin copolymer (B) layer, which is the outer layer, is less than 5 μm, the stiffness of the film will decrease slightly, and
Even if the thickness exceeds 50 μm, the resin in the heat-sealed portion will be thinned by the sealing material when heat-sealed, so the effect will be small. If the thickness of the high-pressure low-density polyethylene that is the intermediate layer (core material) is less than 20 μm, the melt tension when forming the coextruded multilayer film tends to be low, and the formability of the film tends to be poor, and it is difficult to heat-seal the film. In this case, there is a risk that it will not be possible to suppress the decrease in heat sealing strength due to the decrease in the thickness of the ethylene-α-olefin copolymer (B). On the other hand, if the thickness exceeds 70 μm, there is no particular problem, but it is not economical. If the thickness of the ethylene/α-olefin copolymer (0) layer, which is the outer layer, is less than 20μ, there is a risk that the impact resistance will decrease.On the other hand, if the thickness exceeds 70μ, there is no particular problem, but it is not economical. Not.

The coextruded multilayer film of the present invention consists of the above-mentioned ethylene/α-olefin copolymer (B), high-pressure low density polyethylene (A
) and ethylene/α-olefin copolymer (c) are melted in separate extruders, and then various known multilayer gooeys,
For example, single manifold WT-die with black box, multi-manifold T-die,
Alternatively, it can be fed to a multilayer circular die to obtain a three-layer flat or tubular film.

Any or all of the high-pressure low-density polyethylene layer and each ethylene/α-olefin copolymer layer used in the coextruded multilayer film of the present invention may contain a weathering stabilizer, a heat-resistant stabilizer, an antistatic agent, and an antifogging agent. Various additives that are normally added to polyoleain, such as anti-blocking agents, lubricants, nucleating agents, slip agents, and pigment dyes, may be added to the extent that the purpose of the present invention is not impaired.

In order to use the coextruded multilayer film of the present invention as a packaging bag for medium/heavy goods, ethylene/a-olefin copolymer (B)
The bag should be made so that the layers are on the inside.

For example, if it is a flat film, the bottom or mouth is sealed after side sealing or center sealing, or the bag is made by stacking two films and sealing on three sides, or if the film is a tubular film, the bottom or opening is sealed. One method is to seal the mouth.

The coextruded multilayer film of the present invention has excellent impact resistance, opening property, heat seal strength, tear resistance, etc., and has good stackability.
Medium and heavy items such as rice, wheat, feed, cement, fertilizer, sugar, etc.
Among these, it is suitable as a packaging film for heavy items such as feed, cement, and fertilizer.Depending on the application, it has the advantage of being thinner than conventional high-pressure low-density polyethylene films and having excellent storage stability. .

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way unless the gist of the invention is exceeded.

Example 1 Melt flow rate 1.5g7 as inner layer resin (B)
An ethylene/4-methyl-1-pentene copolymer (hereinafter referred to as ICMP) with a density of 10 m1n, a density of 0 to 930 g/cr, a t3, and a melting point of 124°C was used as an intermediate layer resin @
] as melt flow sheet) 0.2 g/10m1
n and a density of 0.930 g/- (hereinafter referred to as HPPK-process), and a resin for the outer layer (C
j) as melt flow sheet) 2-Og 710 w
in s density 0.915g/cIII3 and melting point 124
°C (119 °C, 101 °C with Nemoheek?) Ethylene/4-methyl-1-pentene copolymer (hereinafter referred to as ICMP)
ICMP-1 and HPPIC-1), respectively.
1 and IMF-1 using a 50mmφ extruder (cylinder temperature 170°C) and a 5Qmmφ extruder (cylinder temperature 170°C).
) and 50mmφ extruder (cylinder temperature 170°C)
), then a three-layer circular die (die diameter 20Q)
mm, die temperature 170'C, die lip 2.0mm), folding width 450mm'iKMP-1/HPPIC
-1/IMP-1+7) Thickness 10μ15oμ/40μ(
A coextruded multilayer film with a total thickness of 100μ) was obtained.

The multilayer film was cooled with air at 20° C. using an air ring. The performance of the obtained multilayer film was evaluated by the following method.

Tensile test: Tensile strength at break (kg1017') and elongation at break (%) in the longitudinal and transverse directions were measured using JXS Z 1702.

Impact strength: Measured by method A of ASTM D1709.

Heat sealing strength: Using an impulse sealer, sealing pressure 1.5 kQ/Cl! After sealing under the conditions of 2.75V x 0.5 seconds, a short S-shaped test piece with a width of 15 mm was taken from the film sample including the heat-sealed part and the tensile speed was 500.
A tensile load was applied at a rate of mm/min, and the strength of the heat-sealed portion was measured.

Tear strength: Tear strength in the longitudinal and transverse directions was measured using J-Ko S Z 1702.

Rigidity: Prepare a test piece with a length of 140 mm x width of 70 mm,
Handle -0-Meter (T'hwing
'Albert (USA)' was used, and the slit width was 2cm.
A bending stress was applied to the test piece, and the maximum stress was determined, which was determined as the rigidity (g). Note that the rigidity was measured in the longitudinal and lateral directions of the sample.

Blocking property: The blocking power between the inner layer resins was measured according to ASTM D 1895.

Friction coefficient (static friction coefficient: μ8, dynamic friction coefficient = μk): A
The coefficient of friction between the outer layer resins was measured using STM D 1894, and the loadability was evaluated.

The results are shown in Table 1.

Example 2 The thickness of each layer in Example 1 is ICMP-1/HPPj! The same procedure as in Example 1 was performed except that the knee 1/IC door (P-seal: 10μ, 150μ/60μ) was used. The results are shown in Table 1.

Example 3 The thickness of each layer in Example 1 is E M P-1/HP P K
-1/IMF-1: The same procedure as in Example 1 was performed except that the values were 20μ/60μ/70μ. The results are shown in Table 1.

Comparative Examples 1 and 2 The same procedure as in Example 1 was conducted except that EiMP-1 and HPPB-1 used in Example 1 were each used to form a film with a thickness of 150 μm. Display the results first.

Claims (1)

[Claims] (1) Melt flow rate 0.1 to 10 g'
/ 10 min and density 0.920 to skin 940g
/cIII3 high pressure low density polyethylene (A)
Melt 70-rate 0.1-10 g/10 min% density 0.920-0.
Copolymer o3) ytj of ethylene and α-olefin having 4 to 20 carbon atoms and melting point 115 to 130°C and melt flow rate 0.1 on the other side.
to 10 g/10 min % density 0.910 to 0.950 g/atr' and melting point 115 to 150°C copolymer (0) of ethylene and a-olefin having 4 to 20 carbon atoms. A coextruded multilayer film characterized by: