JP2838120B2 - Polyethylene resin composition and laminated film thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention is for forming a film which is excellent in transparency and well-balanced in stiffness, impact strength, anti-blocking property, heat sealing property and hot tack property. The present invention relates to a polyethylene resin composition and a laminated film using the composition.

<Conventional technology> At present, the packaging materials used for packaging foods, pharmaceuticals, miscellaneous goods, industrial goods, etc. are very diverse,
Most of them are high-pressure low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-α-
A polyolefin resin such as an olefin copolymer is used as the heat seal layer.

These resin layers are usually used by laminating with other appropriate base film. When forming a laminated film, a laminating method such as a dry laminating method, a wet laminating method, a sand laminating method, a hot melt laminating method, Known techniques such as coextrusion, extrusion lamination, and combinations thereof can be employed.

Generally, for packaging materials, to protect the contents,
Mechanical strength such as heat seal strength, impact strength, tensile strength, and tear strength, barrier functions such as moisture proof and gas barrier properties, thermal functions such as heat resistance and cold resistance, as well as low temperature sealability, hot tack, and waist Many functions are required, such as packaging strength such as strength and slipperiness.

In the case of a laminated film, these properties vary greatly depending on the choice of the base material, but similarly, the function of the packaging material varies greatly depending on the choice of the resin used for the sealant layer.

When wrapping is performed at high speed, the film needs to have enough stiffness to withstand high-speed running, and a film that can be heat-sealed at a low temperature is required to enable heat sealing at high speed. In general, a high-pressure low-density polyethylene film has relatively good heat-sealing properties at low temperatures, but has low rigidity, and is not suitable for high-speed packaging such as automatic packaging.

To compensate for this, high-density polyethylene and polypropylene have been blended, but these blends have the drawbacks of lowering transparency, lowering tear strength, and increasing the heat sealing temperature. Have.

On the other hand, a polypropylene film is excellent in transparency and stiffness, but is extremely inferior in low-temperature sealability.

In general, low-temperature sealing of polypropylene is carried out by lowering the melting point by copolymerizing a small amount of ethylene, but this is not sufficient.

In addition, the ethylene-vinyl acetate copolymer film has excellent low-temperature sealability, good heat-sealing strength and impact strength, but is less stiff than the high-pressure low-density polyethylene and is inferior in terms of hot tack. I have.

In contrast, ethylene / α-olefin copolymers are
It is excellent in mechanical properties, heat sealing properties, hot tack properties, foreign substance sealing properties, etc., and has come to be widely used as a sealant material.

As a technique using an ethylene / α-olefin copolymer as a sealant material, for example, JP-A-58-120654 can be mentioned.

It is claimed that this is a composition comprising an ethylene / α-olefin copolymer and an ethylene / vinyl acetate copolymer and has excellent hot tack properties.

However, since the composition is blended with an ethylene / vinyl acetate copolymer, it has low rigidity and inferior anti-blocking property. Thus, at present, various polyolefin resins generally used for the sealant layer of the laminated packaging material include:
Each has advantages and disadvantages and is not always satisfactory.

<Problems to be Solved by the Invention> Ethylene / α-olefin copolymers have come to be widely used as sealant materials, but they do not have the necessary functions in a well-balanced manner.
-When the film is processed under quenching conditions such as the die method, the crystal growth is suppressed, so the transparency of the film is relatively good, but the stiffness and anti-blocking property are poor, When the film is processed under slow cooling conditions as in the air-cooled inflation method, the growth of crystals improves the stiffness and the anti-blocking property but deteriorates the transparency.

As described above, transparency, stiffness, and anti-blocking properties are important properties as a packaging material, but these are usually contradictory items, and it has been considered difficult to improve them at the same time.

The present invention seeks to improve these simultaneously.

<Means for Solving the Problems> The present inventors have conducted intensive studies and found that ethylene having a melt flow rate of 0.1 to 5 g / 10 min and a density of 0.905 to 0.940 g / cm ³ and an α-olefin having 3 to 18 carbon atoms. Ethylene / α-olefin copolymer (A) consisting of: more than 95% by weight and 99.5% by weight or less and a melt flow rate of 0.1 to 2
0 g / 10 min, a high-density polyethylene (B) having a density of 0.945 g / cm ³ or more consisting of 0.5% by weight or more and less than 5% by weight, and
The ratio MFR _A / MFR _B with a melt flow rate MFR _B has a melt flow rate MFR _A high density polyethylene of the ethylene · alpha-olefin copolymer (A) (B) is characterized in that 8.8 to 0.1 It has been found that the polyethylene resin composition for film molding retains the original function of the ethylene / α-olefin copolymer and can simultaneously improve transparency, stiffness and anti-blocking properties, The first invention has been reached. Furthermore, they have found that a laminated film using the resin composition for at least one surface layer is extremely useful as a packaging material, leading to the second invention.

The ethylene / α-olefin copolymer (A) used in the present invention is defined as ethylene and α-olefin having 3 to 18 carbon atoms.
-Obtained by polymerizing an olefin using a transition metal catalyst. The copolymerization reaction is usually carried out at a polymerization temperature of 30 to 300 ° C., at a normal pressure to a polymerization pressure of 3000 kg / cm ² , in the presence or absence of a solvent, in a gas-solid, liquid-solid or homogeneous liquid phase. Is done.

As the α-olefin, propylene, butene-1,4
-Methylpentene-1, hexene-1, octene-1, decene-1 and the like are used, but those having 4 to 10 carbon atoms are preferable. These α-olefins can be used alone or in combination of two or more.

In the present invention, the high-density polyethylene (B) is a homopolymer of ethylene and / or ethylene and 3 carbon atoms.
To 10 α-olefins, which can be selected from those commercially available as high-density polyethylene.

 Hereinafter, each item will be described.

(1) Melt flow rate and MFR _A / MFR _{B In the} present invention, the melt flow rate (MFR) is JIS K
The MFR (MFR _A ) of the ethylene / α-olefin copolymer ( _A ) is 0.1 as measured by the method specified in 6760.
Or 5g / 10min. MFR _A 0.1g / 10m
Those with less than in are inferior in moldability due to high melt viscosity, and
Those exceeding 5 g / 10 min are also inferior in moldability because the melt tension is small.

The MFR (MFR _B ) of the high-density polyethylene (B) to be blended with the copolymer (A) in an amount of 0.5% by weight or more and less than 5% by weight must be 0.1 to 20 g / 10 min. MFR _B is 01.g / 10
When the composition is less than min, when the composition is formed into a film, fish eyes are formed on the film. When the composition exceeds 20 g / 10 min, smoke is intensely generated during film processing, which is not practical.

Also, the ratio MFR _A / MFR _B of the copolymer (A) to the high-density polyethylene (B) must be 0.1 to 8.8, and in other ranges, the miscibility is poor. During inflation processing, bubbles may be perforated,
Even in the T-die processing, troubles such as film breakage occur at the time of high-speed processing, and transparency and impact strength also become poor in physical properties.

(2) Density In the present invention, the density is measured after annealing at 100 ° C. for 1 hour in accordance with JIS K6760, and the copolymer (A) has a density of 0.905.
Or 0.940 g / cm ³ and 0.905 g / cm ³
If it is less than 10, the film becomes weak and the suitability for automatic filling as a product is poor.

On the other hand, if it exceeds 0.940 g / cm ³ , the temperature at which the heat sealing property and the hot tack property are developed increases, and the automatic filling speed decreases.

The density of the high-density polyethylene (B) needs to be 0.945 g / cm ³ or more. If it is less than 0.945 g / cm ³ , the effect of blending the high-density polyethylene is insufficient, and the effect of improving transparency is particularly low. unacceptable.

(3) Composition ratio The resin composition of the present invention contains more than 95% by weight of the copolymer (A) and not more than 99.5% by weight, and
% By weight or more and less than 5% by weight.

If the high-density polyethylene (B) is more than 5 wt%, the temperature at which heat sealability and hot tack properties are developed will increase, and the automatic filling speed will decrease. If it is less than 0.5 wt%, the blending effect of the high-density polyethylene will decrease. I can't get it.

As the mixing method, each component is dry-blended using a mixer such as a Henschel mixer or a tumbler blender in the above-mentioned range, and after mixing, it is further melt-kneaded with a single-screw extruder or a multi-screw extruder. A method of granulating, a method of melt-kneading and granulating with a Banbury mixer, a kneader, a roll mill or the like can be employed.

(4) Laminated film The film made of the resin composition of the present invention has excellent transparency, and is excellent in rigidity, impact strength, anti-blocking property, heat sealing property, hot tack property, and has excellent properties as a sealant material. Have.

Therefore, a packaging film suitable for various uses can be obtained by bonding with various substrates. As these substrates, any polymer having a film forming ability, paper, aluminum foil, cellophane, or the like can be used.

As the polymer, for example, high-density polyethylene,
Medium, low density polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylate copolymer, ionomer, polypropylene, poly-1-butene, poly-4-
Olefin polymers such as methyl-1-pentene, vinyl polymers such as polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylate, polyacrylonitrile, nylon 6, nylon 66, nylon 7, nylon 10, nylon 11, nylon 12, polyamides such as nylon 610, polymetaxylylene adipamide, etc., polyesters such as polyethylene terephthalate, polyethylene terephthalate / isophthalate, polybutylene terephthalate, polyvinyl alcohol, ethylene vinyl alcohol copolymer,
Polycarbonate and the like can be mentioned. These substrates can be appropriately selected depending on the purpose and the article to be packaged.
For example, in the case of foods in which the packaged product is easily corroded, resins having excellent transparency, rigidity, and gas permeation resistance, such as polyamide, polyvinylidene chloride, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, and polyester, are used. Selected. For confectionery, fiber packaging and the like, polypropylene or the like having good transparency, rigidity and moisture permeation resistance can be selected as the outer layer. If the substrate is a polymer, it may be uniaxially or biaxially stretched.

Examples of a method for producing a laminated film in which a film composed of the resin composition of the present invention and the above-mentioned base material are bonded to each other include a lamination method such as a dry lamination method, a wet lamination method, a sand lamination method, a hot melt lamination method, a coextrusion method, Known techniques such as an extrusion lamination method and a combination thereof can be employed.

Further, the resin composition of the present invention contains an antioxidant, a lubricant, an anti-blocking agent, an antistatic agent, a drip-free agent, a weathering agent, a pigment,
Various compounding agents such as dyes and fillers, which are usually used by adding to polyolefins, may be compounded within a range not to impair the object of the present invention. Further, high-pressure low-density polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylate copolymer, ethylene / methacrylic acid copolymer, etc. may be blended within a range not to impair the object of the present invention. .

Since the resin composition of the present invention is excellent in transparency and has a good balance of stiffness, impact strength, anti-blocking property, heat sealing property, and hot tack property, at least a layer of the resin composition is required. The laminated film on the surface layer on one side consists of confectionery, snacks, instant noodles, sprinkles,
It can be suitably used for the packaging of dry foods such as powdered soups, meat products such as ham, sausage, livestock meat, various foods such as marine products such as konjac, pickles, miso, liquid soups, liquid detergents and liquid chemicals.

<Examples> Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist thereof.

First, methods for measuring physical properties in the following examples and comparative examples will be described.

(1) Density According to the method specified in JIS K6760. After annealing for 1 hour in water at 100 ° C., the density was measured.

(2) Melt flow rate (MFR) In accordance with the method specified in JIS K6760.

(3) Haze (cloudiness) The method specified in ASTM D1003 was followed. The smaller this value is, the better the transparency is.

(4) 1% secant modulus (MD) or its perpendicular direction (TD)
A 2cm wide specimen is cut out, attached to a tensile tester at a distance of 6cm between the chucks, pulled at a speed of 5mm / min, and the stress at 1% elongation is calculated by the formula of 100 x (stress) / (cross-sectional area). Calculated.

(5) Dart impact strength According to method A of ASTM T1709.

(6) Blocking the sealant layer of the laminated film,
Under a load of 7kg / 200cm ^2, 23 ℃ sample was subjected to conditioning for 20 hours at 40 ° C., under a RH 50%, at Toyo Seiki vertical peelable blocking tester, load shift speed
A peeling force was applied at 20 g / min, and the force required for peeling was measured.

(7) Heat sealability The polyethylene layers of the two composite films are combined, and a seal width of 10 mm is applied using a tester heat sealer under the conditions of a seal surface pressure of 1.0 kg / cm ² and a seal time of 1.0 second.
Heat sealing. Heat sealing is performed in the same manner while changing the temperature of the seal bar (heat sealing temperature) by 5 ° C. From this, a specimen having a width of 15 mm is cut out at right angles to the sealing surface, and the 180 ° peel strength is measured at a speed of 200 mm / min using a Shopper type tensile tester.

(8) Hot tackiness The polyethylene layers of the composite film cut to a width of 15 mm are combined, and a load of 30 g is applied to one side via a pulley. Using a heat sealer manufactured by Tester Sangyo, heat seal with a seal width of 20 mm is performed under the conditions of a seal surface pressure of 1.3 kg / cm ² and a seal time of 0.3 second. Since the load drops at the same time as the end of the seal, and the peeling force due to the load is applied to the seal surface 0.14 seconds after the end of the seal, the actual peeled length is measured. The same test is performed by changing the temperature of the seal bar (heat sealing temperature) in steps of 5 ° C.

Example 1 Sumikasen αCS2010 manufactured by Sumitomo Chemical Co., Ltd. (comonomer is hexene-1, MFR = 2.4 g / 10 min, density = 0.912 g / cm ³ )
To 91wt%, Nissan polyethylene 1010 (MFR = 0.97g / 10m
in, density = 0.948 g / cm ³ ) 1 wt%, 5 wt% of 10 wt% of natural silica MB prepared using CS2010 as a base polymer,
And 2w also made with CS2010 as base polymer
3% by weight of MB of erucamide at a concentration of t% was blended in a tumbler.

This blend was put into a 65 mm extruder (screw L / D = 32) manufactured by Sumitomo Heavy Industries, Ltd., die width 600 mm, die lip 1.
Attach 0mm, straight manifold type T-die,
Extruded under the condition of die set temperature of 220 ° C and discharge rate of about 25Kg / hr, cooled with a semi-mat roll of 600mmφ controlled at 60 ° C, and wound up on a paper tube by using the resin composition of the present invention having a thickness of 40μ. The film was obtained and measured for haze, 1% secant modulus, and dart impact strength. Table 1 shows the measurement results.

Furthermore, this film is drawn into 35μ thick stretched nylon / LDP
E Double film (thickness configuration: stretched nylon: 15μ, LDPE: 20
μ), a 65φ extruder made by Sumitomo Heavy Industries, Ltd.
L / D = 26) and Sumikasen L705 with a resin temperature of 320 ° C using an L550 type laminator manufactured by Tanabe Plastics Machinery Co., Ltd.
(Low-density polyethylene) is extruded in the middle to perform a sand lamination process with a thickness of the intermediate layer of 30 μm to form a laminated film having a configuration of [stretched nylon / LDPE / L705 / film of the resin composition of the present invention]. Obtained. The heat sealing property and hot tack property of the laminated film thus obtained were measured, and the heat sealing property was 5 kg / 15 mm.
And the lower limit temperature and upper limit temperature of the heat seal at which the peel distance was 5 mm were obtained for the hot tack property, and the results are shown in Table 1.

In addition, the measurement of blocking was also performed for the laminated film, and the results are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated, except that Nissan polyethylene 1010 was not used. Table 1 shows the results.

Example 2 and Comparative Example 2 Sumikasen α CS2010 (containing 5000 ppm of natural silica and 600 ppm of erucamide) Nissan polyethylene 1010 used in Example 1 was tumbled and blended in the ratio shown in Table 1, and the same method as in Example 1 was used. Was subjected to film processing and sand lamination processing, and physical properties were measured.
The results are shown in Table 1.

Comparative Example 3 Ultoxex 3520L manufactured by Mitsui Petrochemical Industries, Ltd. (comonomer was 4-methyl-
1-pentene, MFR = 2.2 g / 10 min, density = 0.931 g / cm ³ ) was subjected to film processing and sand lamination in the same manner as in Comparative Example 1, and the physical properties were measured. The results are shown in Table 1.

Example 3 97% by weight of Ultrazex 3520L used in Comparative Example 3 and 520MB of Idemitsu Polyethylene (MFR = 0.25g / 10min, density = 0.963g)
/ cm ³ ) 3 wt% was mixed with a Henschel mixer, and the mixture was subjected to film processing and sand lamination in the same manner as in Comparative Example 1 to measure physical properties. The results are shown in Table 1.

Comparative Example 4 Sumikasen-L FA101-1 manufactured by Sumitomo Chemical Co., Ltd. (comonomer is butene-1, MFR = 0.8 g / 10 min, density = 0.921 g / c
m ³ ) Sumikacene F208-0 (MFR = 1.5 g)
/ 10min, density = 0.922g / cm ³ ) After adding 10 parts by weight and blending with a tumbler, a Placo K-40R inflation molding machine equipped with a spiral die having a die diameter of 125mm and a die lip of 2.0mm and an air ring with an iris ( Screw L / D = 1
Using 9), the film was extruded under the conditions of a die set temperature of 190 ° C. and a discharge rate of 23 kg / hr to obtain a film having a blow-up ratio of 1.8 and a thickness of 60 μm.

Further, this film was dry-laminated using a 35 μm-thick stretched nylon / LDPE bilayer film described in Example 1 as a base material using a test coater MGD-280 manufactured by Yasui Seiki Co., Ltd. / LDPE / the above film].

At the time of dry lamination processing, Adcoat 308A / B manufactured by Toyo Morton Co., Ltd., which is a two-component curing type polyurethane adhesive, was used as an anchor coating agent.

Table 1 shows the measurement results of the physical properties of the film and the laminated film.

Example 4 Sumikasen-Hard 2603B (MFR = 5.0 g / 10 min, density = 0.960) was added to Sumicacene-L FA101-196 wt% used in Comparative Example 4.
g / cm ³ ) To 100 parts by weight of the composition to which 4% by weight was added, 10 parts by weight of Sumikacene F208-0 was added and blended by a tumbler. Then, film processing and dry lamination were performed in the same manner as in Comparative Example 4. Physical properties were measured. The results are shown in Table 1.

Comparative Example 5 Sumicacene Hard 3621 (MFR = 0.05 g / 10 min, density = 0.955) was added to Sumicacene-L FA101-195 wt% used in Comparative Example 4.
g / cm ³ ) 10 parts by weight of Sumikacene F208-0 was added to 100 parts by weight of the composition to which 5% by weight was added, and after blending with a tumbler, film processing was attempted in the same manner as in Comparative Example 4.
The melt flow rate of high density polyethylene (B) is 0.1g
Because it was less than / 10 min, many fish eyes were generated in the film, and holes were frequently formed in the bubbles, and good film processing could not be performed.

<Effects of the Invention> As described above, according to the present invention, a resin composition excellent in transparency, stiffness and anti-blocking properties, and excellent in heat sealability, suitable for packaging materials and A laminated film using a layer composed of the resin composition as at least one surface layer can be provided.

Continuation of the front page (72) Inventor Satoru Koyama 5-1 Anesaki Beach, Ichihara-shi, Chiba Sumitomo Chemical Co., Ltd. (56) References JP-A-63-289548 (JP, A) JP-A-58-210948 (JP) , A) JP-A-58-171424 (JP, A)

Claims (2)

(57) [Claims] 1. The melt flow rate is 0.1 to 5 g / 10 mi.
n, an ethylene-α-olefin copolymer (A) composed of ethylene having a density of 0.905 to 0.940 g / cm ³ and an α-olefin having 3 to 18 carbon atoms: more than 95% by weight and not more than 99.5% by weight; Flow rate 0.1 to 20g / 10min, density 0.945g / c
m ³ or more high-density polyethylene (B): composed less than 0.5 wt% to 5 wt%, and a melt flow rate MFR _A high density polyethylene of the ethylene -α- olefin copolymer (A) (B) Of melt flow rate MFR _B to MFR _A
/ MFR _B is from 0.1 to 8.8. 2. A laminated film, wherein at least one surface layer is a layer comprising the polyethylene resin composition according to claim 1.