JPS58140249A - 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 relates to a multilayer film that is easy to open.

Furthermore, tp shi< has a propylene/α-olefin random copolymer layer on one side with high-density polyethylene as a core material,
A propylene/α-olefin random copolymer layer or an ethylene/α-olefin copolymer layer is laminated on the other side, resulting in low wet impact strength, transparency, and low temperature heat sealing. The present invention relates to a multilayer film that is easy to open.

In general, for packaging of relatively hard contents such as boxed cigarettes, confectionery, and pharmaceuticals, both sides of the base material are mainly made of strong biaxially oriented polypropylene film or cellophane. Alternatively, a three-layer film laminated with a propylene/ethylene random copolymer is used as an overwrap packaging film. However, such a strong three-layer film is not suitable as a packaging material for soft contents such as bread and toilet paper. Vinyl acetate copolymer J&, f
A layered one-E layer film or a high-pressure low-density polyethylene film is used. Among these, the three-layer film based on unstretched polypropylene film 41 has excellent low-temperature heat-sealability and easy-opening properties, and therefore is suitable as an overlap packaging film because the contents can be easily removed.

However, since such a three-layer film is based on pyrene, it has poor cold resistance, and at low temperatures, the bag easily breaks due to impact or pinholes occur. So low temperature ti! If! ! In order to improve the strength, there is a method of adding and mixing polyethylene or ethylene/α-olefin copolymer to polypropylene, or mixing ethylene with propylene by copolymerization). Proposed. On the contrary, as long as polypropylene is kept at 1τ, there is a limit to the improvement in low-temperature impact strength.

- For the purpose of improving the low-temperature impact resistance (i), an ethylene/vinyl acetate copolymer is laminated on both sides of a base material made of a composition of high-density polyethylene and high-pressure low-density polyethylene, or high-pressure low-density polyethylene. However, it has the disadvantage that it is too soft and has poor cutability in bag making machines, and its heat sealing strength is strong and there is a risk of damaging the contents when taking it out. there were.

Therefore, the present inventors used high-density polyethylene as a core material, had a B-Dpylene/rl-olefin random copolymer layer on one side, and a propylene/α-olefin random copolymer layer or an ethylene/α-olefin random copolymer layer on the other side. It has been found that by layering an olefin copolymer layer, a multilayer film having appropriate stiffness, excellent low-humidity impact strength, transparency, low-temperature heat sealability, and easy opening can be obtained, and the present invention reached.

In other words, the present invention is a melt flow system (ASTlvlD).
I238:E) 0.3 to 15.0 g/
10mln, density 0.950 to 0.970g/
l) High-density bore IJ in the range of m' (AsTMD 1 with ethylene (A) as the core material and melt flow lay on one side
238:L) 0.1 to 40 g/10 mj, n
.

Propylene content: 4 to 80% by weight, 11% by weight, heat of crystal fusion from 10 to 8, based on thermal analysis with a differential scanning calorimeter
A random copolymer (B) layer of propylene and an α-olefin having 4 to 10 carbon atoms in the range of θ/g and a layer of the propylene/α-olefin random copolymer (E) or Melt flow rate (AST
MD 1238:E) 0.5 to 20g/10m1n
, a multilayer comprising laminated layers of a copolymer (a) of ethylene and an α-olefin having 4 to 20 carbon atoms and having a density of 0.910 to 0.94087 cm3 and a melting point of 115 to 130'C. It provides film.

The high-density polyethylene (A) used as the core material used in the present invention is melt flow rate-1-(ASTM D 12381
) is 0.3 to 15. [j g / 1 () mj
-n, preferably 0.5 to 7-Og/10 m
], n % density is 0.950 to 0.970 g/C
n13, preferable L (CrJ, 0.950 nishi 0.
965 g/atr' and a homopolymer of ethylene or ethylene and up to 2 mol% of other α-olefins, such as propylene, 1-butene, 1-pentene,
It is a copolymer with 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, etc. If the melt flow rate is less than 0.3 g 710 mln, the melt viscosity is high and molding is difficult, and the surface of the base material becomes rough, resulting in a propylene/α-olefin random copolymer (B) layer described later. A multilayer film with a good appearance cannot be obtained even if these are laminated. On the other hand, the melt flow rate is 15.0 g.
/ 10 min, the melt viscosity is low and the moldability is poor. If the density is less than 0.950 g/cm', the rigidity is low, and when formed into a multilayer film, the stiffness is weak, and the suitability for packaging machines is poor.

A propylene/α-olefin random copolymer (T3) laminated on at least one side of the core material made of the high-density polyethylene (A) and (4, melt flow 1/, -) (A
STM D 12 filter 13: T, ) is 0.1 to 40 g/i I) m i, 71, preferably 1 to 20 g/l fTlmin,, pu[1] content is 43 to 80 g/l %, preferably 1] 6 to 75% by weight, heat of crystal fusion In 10 to 80, Toule/g, based on thermal analysis with a differential scanning calorimeter.
, preferably a random copolymer of propylene in the range of 20 to 70 Joul θ/g and an α-olefin having 4 to 10 carbon atoms, preferably a random copolymer of propylene and 1-butene. If the melt t'-ray-4 is less than 0.1 g or 710 m1n, the melt viscosity is high and the moldability is poor, and if it exceeds 40 g/10 m1n, the melt viscosity is low and the moldability is poor. If the propylene content is less than 43% by weight, the melting point of the copolymer will be low, the heat resistance of the film will be poor, blocking will occur easily, and 80% by weight
% Gj1 film has poor transparency and flexibility, has a high melting point, and has a low 7fi! Poor sealing performance.

The heat of crystal fusion is a value that correlates with the degree of crystallinity of the polymer, but propylene/α-olefin random copolymers with a heat of fusion exceeding 80:1011107g are copolymerized components re-:)l/f- Since the amount of r is small in tf or n-;t L-fins are block copolymerized, transparency and flexibility are poor. On the other hand, a propylene-α-A reflexine random copolymer having a heat of fusion and Ht of 10 Joule/g or less has poor mechanical properties and heat resistance 1fI, and has a sticky feel.

The heat of fusion of the polymer in the present invention is measured by differential scanning heating. I: Specific heat curve of the completely melted state of the copolymer according to *I
This value is calculated using a straight line obtained by directly extrapolating the specific heat curve (expressed in °C) to the low temperature side as a baseline.

The heat of fusion 11 is measured under the following measurement conditions. That is, after leaving the sample at 200°C for 5 minutes, the test was heated at 10°C/min.
Cool to -40°C at a rate of -40°C and leave at -40°C for 5 minutes. After that, at a heating rate of 20°C/m1n - 40°
Measurements are taken from 200°C to 200°C.

A propylene/α-adjacent olefin random copolymer with a propylene content of 43 to 8 [1% by weight] having the properties d as described above is, for example, (a) a composite containing at least 4% magnesium, titanium, and a halogen. (b) an organometallic compound of a metal from Group 1 to Group 3 of the periodic table;
C) Obtained by random copolymerization of propylene and α-olefin using a catalyst formed from an electron donor. Part or all of the electron donor (0) may be fixed to part or all of the complex (a), or may be pre-contacted with the organometallic compound (11) prior to use. Good too. Particularly preferably, part of the electron donor (C) is fixed to the complex (a), and the remaining part is added to the polymerization system as it is or an organometallic compound (
This is an embodiment in which it is used in preliminary contact with b). in this case,
The electron donor immobilized on the complex (aJ) and the electron donor used by directly adding it to the polymerization system or by pre-contacting it with (b) may be the same or different.

In addition, the propylene/α-oleph/inlangum copolymer (B) may include, within the range that does not impair the object of the present invention, among the polypropylene commercially available as a so-called normal propylene random copolymer. Polypropylene having a melt 70-rate of 0.1 to 40 g/10 m1n and a propylene content of 93 to 99 mol % and homogeneous polypropylene may be added.

The propylene/a-olefin random copolymer (E) layer must be laminated on at least one side of the high-density polyethylene (A) that is the core material of the multilayer film of the present invention, and the other side is made of propylene. - An ethylene/α-olefin copolymer (C) layer may be laminated in place of the α-olefin random copolymer ω) layer.

The ethylene/α-olefin copolymer (0) used in the present invention has a melt flow rate (A, STMD123
8:E) is 0.5 to 20 g/10m1n, preferably 1.0 to 10 g/10m1n, density is skin 910 to 0.940 g10n', preferably 0.915 to 0.935 ( t, 7 cm3 and a melting point of 115 to 1,')0'C1 preferably in the range of 115 to 125°C and 4 to 2 carbon atoms (1, preferably 5 to 1)1σ) (r-
It is a copolymer with olefin. Those with a melt flow rate of less than 0.5 g/710 mj,n have a high melt viscosity and are poor in moldability, and those with a GJ melt viscosity of more than 20 g/10 m1n have a low GJ melt viscosity and are poor in moldability. Density is 0.91 tT!
If it is less than 0.94 fl g/10 m1n and made into a film, the surface will be sticky and the oil resistance will be poor.
/lyn' is inferior in transparency and low-temperature heat sealability. The above-mentioned melting point is an increase in lh measured by a differential scanning calorimeter.
A is the highest temperature at a point showing a sharp endothermic peak determined from an endothermic curve at 10°C/m j-n. The ethylene/α-olefin copolymer (0) has one or more sharp endothermic peaks, often two to six sharp endothermic peaks.
The maximum temperature of its sharp endothermic peak, that is, the melting point, is in the range of 115 to 130'C. Melting point is less than 115°C (7) Monoha has poor heat resistance, 130°C
If the temperature exceeds ℃, the low-temperature heat sealability is poor. Further, the α-olefin having 4 to 20 carbon atoms specifically includes 1-butene, 1-pentene, 1-hegisene, 4-methyl-1-
Pentene, 1-octene, 1-decene, 1-hexylidecene, 1-octadecene, or a mixture thereof, and α-olefins having 5 to 18 carbon atoms are particularly preferred as IFLs.
stomach. Copolymers with propylene have poor mechanical strength.

The ethylene/α-olefin copolymer (0) having the above properties used in the present invention is polymerized with ethylene and α-olefin at the required density by a so-called medium/low pressure method using a transition metal catalyst. obtained by At that time, to obtain the desired melt flow rate +
j 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.

Ethylene/α-olefin copolymer (C
), the purpose of the present invention is to obtain a low crystalline ethylene/propylene random copolymer, an ethylene/propylene random copolymer, and
A 1-butene random copolymer or the like may be blended.

The thickness of each layer of the multilayer film of the present invention is not particularly limited, but the thickness of the propylene/α-olefin random copolymer (+ or ethylene/α-olefin copolymer layer) which is the coating layer is usually 1 to 20/l, The thickness is preferably 1 to 10 μm, particularly preferably 1 to 5 μm. If the thickness exceeds 20 μm, low-temperature heat sealing strength and ease of opening tend to be poor. On the other hand, regarding the high-density polyethylene (A) layer serving as the core material, Although not particularly limited, usually 5
The thickness ranges from 5 to 100μ, preferably from 5 to 50μ.

The multilayer film of the present invention, namely (B)/(A)/(
B) or (0) / (A) / (B) As a method for obtaining a multilayer film consisting of Or propylene on one side.
fV・-4 Refine random copolymer (n) J? i. Ethylene on the other side. - There is a method of extrusion lamination of the olefin copolymer (0) layer, and a method of coextrusion molding using a die with a three-layer structure. It is preferable to use a coextrusion molding method because the B) layer or the ethylene/α-olefin copolymer (0) layer can be made thin. The coextrusion molding method is T-, which uses a flat die.
There is a die method and an inflation method using a serular die. Flat die is available in a single manifold format using a black box or in a multi-manifold format.
Either manifold format may be used. As for the die used in the inflation method, any known die can be used.

The multilayer film of the present invention has a propylene/α-olefin random copolymer (13) try laminated on at least one side of the high-density polyethylene (A) layer, so that it has appropriate stiffness, transparency, and low-temperature peat sealing. This results in a multilayer film suitable for overwrap packaging that is flexible and easy to open. In addition, by making one side of the high-density polyethylene (A) layer an ethylene/α-olefin copolymer (C) layer, the above performance can be achieved, and the ethylene/α-olefin copolymer (0) layers can be heat-sealed together. This results in a multilayer film with strong heat-sealing strength, which is suitable as a material for square-bottomed bags, such as those disclosed in JP-A-55-217. However, high density polyethylene (A,
) layers are made of propylene/α-olefin random copolymer (B) and σ) other than M, for example, ethylene/n-17th fin copolymer (0) layer or ethylene/vinyl acetate copolymer layer. A multilayer film with strong heat sealing strength and easy opening cannot be obtained.

The multilayer film of the present invention contains 1/2 inch high-density Boriena.
(A) layer, propylene/alpha-olefin lantum copolymer (B) N and ethylene/(r-olefin co-39) layer (0) in any layer or all layers, a weathering stabilizer,
This book covers various compounding agents that are usually added to polyolefins, such as heat-resistant stabilizers, antistatic d-agents, antifogging agents, antiblocking agents, slip agents, lubricants, pigments, dyes, droplet agents, and nucleating agents. It may be added within a range that does not meet the purpose of the invention.

The multilayer film of the present invention has appropriate stiffness, excellent low-temperature impact strength, transparency, and low-temperature heat sealing (1<l), and is easy to open, so it can be used in square bag packaging, sub-burlap packaging, etc. , can be used in a wide range of fields.

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 70-rate 1.0 g/l 0m as core material
i, r+ and high density polyethylene with a density of 0.95 S E /'71" (hereinafter abbreviated as HD 1-' IC-I)
, melt flow as coating layer L/-) 7.0
Propylene/1-butene random copolymer (hereinafter referred to as PB) with a propylene content of 70 wt.
(abbreviated as R-cho), HD P I'e-cho is 65m
mφ extruder (cylinder temperature 24 [1'C), P E
R-] was melted in two 43 mmφ extruders (cylinder temperature 2 θ' (2) and fed to a five-layer 1-die (240°C) to produce pnn-y-/n Dp+e. −■
/ ]>nu-]: = 6μ/14μ/ 3 /
A five-layer film consisting of Next, the performance was evaluated using the following method.

Haze (%): A S'l'M Dl 0C1 tensile test: A, 'E'I'M According to 11638, yield point 1 nol 5JJ (hereinafter abbreviated as YS) and tensile strength at break (
(hereinafter abbreviated as 'I'T3) was measured in the longitudinal direction (hereinafter abbreviated as MD) and the transverse direction (hereinafter abbreviated as TD).

Bending rigidity (k (7/17ff2): 140mmX14n
Prepare a mm (7) sample and use Handle O1j4 (
Apply bending stress to the sample using ltOr (ThwjnHA)ber'l; made in the United States) and set rfj to 5+nm.The maximum stress was calculated, and the value divided by the thickness of the sample was calculated as the bending rigidity (kg/cnr2). did. The bending rigidity was determined at two points: MD and I'1) of the sample.

Impact strength (kfl-(:IN/n)1): A r
: TMD 342 DL-) Sea/l' part peel strength (g715 ml+) : -, 7-1 Overlap the lum surfaces, 90'C, 1 (10°C, 110'' (:, 1
20'C, 13 [] "C, 1d Temperature of OoC, 21
After heat-sealing with a seal bar having a width of 5 mm for 1 second at a pressure of g/ay2, it was allowed to cool. A test piece with a width of 15 mm was cut from this, and the strength was measured when the heat-sealed portion was peeled off at a crosshead speed of 200 mm/min.

The results are shown in Table 1.

Example 2 Actual M1 One layer of P used in Example 1]]3R- was melted into a melt 70-L/-) 2g/10mln, density 0.920g
The same procedure as in Example 1 was conducted except that an ethylene/4-methyl-1-pentene copolymer (hereinafter abbreviated as EMO-I) with a melting point of /cm' and a melting point of 121°" (:) was used. The results are shown in Table 1. The peel strength of the heat-sealed part is P 13 R-1.
This is a value measured by heat-sealing the layers together.

Comparative Example 1 Melt 7 was used instead of lIDPE-H used in Example 2.
0-Lee Doa-eup/10m1. Table 1 shows the results of the same procedure as in Example 2, except that polypropylene (product name: Mikata Petrochemical Polypropylene F631, manufactured by Mitsui Petrochemical Industries KK, abbreviated as PI-1) was used. Show G.

Comparative Example 2 In place of the old) PF'-1 used in Example 1, P1)-1 used in Comparative Example 1 was replaced with PBR-■ used in Example 1: L-tyrene/acid-resistant vinyl Polymer (product name x
y<71. -tsu/7 XoP14D5, Mitsui Bo'J'r
The process was carried out in the same manner as in Example 1, except that EVA-I was used. The results are shown in Table 1.

Comparative Example 5 II DI Tfl-I used in Example 2 was replaced with p p , -Tfl-I used in Comparative Example 2 and melt flow rate 4 (< / 10 mj, n (ASTM Di 2
8: E), ethylene content 1ii: '/1 mol%,
A composition (PP-T/KBR-■-70/311 weight ratio) consisting of ethylene/1-/butene random copolymer (hereinafter abbreviated as EBR-1) with a ld point of 73°C was
The same procedure as in Example 1 was performed except for the following. The results are not shown in Table 1.

Comparative Example 4 [i; VA-T used in Comparative Example 2 was used instead of PBR-■ used in Example 1, H]IIP Ii; -1
・4.8g710m]n and density 0.921g 10
t3 (7) High-pressure process low density polyethylene (Product name: Mirason ■24H1 Mitsui Polychemicals KK W: Hereinafter referred to as T+ D
A composition (HDP+c-r) consisting of
/r, DpIc=70/filtration weight ratio) was carried out in the same manner as in Example 1. The results are shown in Table 1.

Claims (1)

[Claims] (1) Melt flow rate (ASTMD 1231L
:+7) 0.3 to 15.0 g, / 10 mj
, n , density 0.95 [1 not 1, 0.970 g
/cyn3 high-density polyethylene (A) as the core material, melt flow rate (ASTM 111238:
L) 0.1 to 40 g/10 mj, n, propylene content 43 to 80 1% by weight, differential scanning thermal 11
Heat of crystal fusion 1o to 80Jo based on thermal analysis of 1 meter
A layer of a random copolymer (B) of propylene in the range of ule/g and an n-olefin having 4 to 10 carbon atoms, and a layer of the propylene/6-7 reflexine random copolymer (B) or melt flow) (A, ST
MD 1238:E) 0.5 stone 20g710m1n
, a copolymer of ethylene and an n-olefin having 4 to 20 carbon atoms and a density of 910 to 0.940 g 10n3 and a melting point of 115 to 130'C (characterized in that the 01 layer is 15ij). multilayer film 0