JPH02172737A - Laminating film excellent in low temperature heat sealability - Google Patents

Abstract

PURPOSE:To improve heat sealability at low temp. by forming a laminating film by providing a laminating layer composed of a copolymer having a specific composition and a heat-sealing layer composed of a copolymer having a specific composition on a base film. CONSTITUTION:A laminating layer constituted of 70-95wt.% of a composition consisting of a straight chain ethylene/buten-1 copolymer or straight-chain ethylene/hexane-1 copolymer having density of 0.91-0.94g/cm<2> and 30-5 wt.% of high-pressure low density polyethylene is provided on a base film. Subsequently, a heat-sealing layer composed of a composition consisting of 35-60wt.% of a straight chain ethylene/hexane-1 copolymer having density of 0.91-0.94g/cm<2>, 25-40wt.% of a low-crystalline ethylene/alpha-olefin copolymer and 15-25wt.% of high-pressure low density polyethylene is laminated to said laminating layer to obtain a laminating film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a laminated film for lamination with excellent low-temperature sealability that is laminated to various base films.

[Prior art] Nylon, polyester, polypropylene, etc. are packaging base materials with excellent transparency, strength, and heat resistance. When sealing the contents using the above-mentioned materials, heat sealing was difficult because the heat welding temperature was high, resulting in defects such as shrinkage of the film or difficulty in complete welding. The produced film is used as a laminated film with a separate heat-sealing layer.

As the resin used for the heat seal layer, high-pressure low density polyethylene, ethylene-vinyl acetate copolymer, ionomer, polypropylene, high density polyethylene, etc. are used. When producing laminated laminated films, high-pressure low-density polyethylene has a heat-sealing temperature of around 110°C and is easy to handle, but it does not boil while containing the contents, may have a slight odor, and is not suitable for bending. As a result, bottle holes are generated at the bent portions, making it difficult to block external air, which may cause problems when packaging fresh foods.

Ethylene-vinyl acetate copolymer has excellent low-temperature sealing properties, but increases odor when sealed at high temperatures, and does not have excellent bending pinhole resistance, hot tack properties, or heat resistance.

Ionomers have excellent heat seal strength and hot tack properties, but their adhesive strength is somewhat weak, their extrusion processability is poor, and the film is prone to fish eyes and bumps.
If you use 1'J t'+ film, the film will have a stiff and hard texture, and when moving heavy items such as tilted meat in a vacuum package, the packages will rub against each other and cause pinholes to form. This may cause vacuum return.

Polypropylene has strong heat-sealing strength, but during T-die processing, it tends to thermally decompose, the molecular plate tends to drop, and there is a large amount of neck-in, which is difficult to handle.The heat-sealing temperature is too high at 150℃, making it difficult to handle. , its range of use is limited due to 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 processability is poor.

As mentioned above, each material has its advantages and disadvantages, and none of them are satisfactory yet.

[Problems to be Solved by the Invention] In view of the above circumstances, the present inventors have developed a product that has particularly excellent low-temperature sealing properties and economical efficiency, and has excellent low-temperature impact resistance, pinhole resistance, interlayer adhesion, stress crack resistance, and hot As a result of various studies to obtain a laminated film for lamination with excellent tackiness, odorlessness, and transparency, it was found that the above object could be achieved by the means described below, and the present invention was completed.

[Means for Solving the Problems] That is, the present invention provides a laminated film for lamination consisting of a layer to be laminated to a base film and a heat sealing layer for imparting low-temperature heat sealability to the base film, The layer bonded to the base film has a density of 0.91 to 0.94 g/
It is composed of a composition consisting of 70 to 95% by weight of am3 linear ethylene-butene-1 copolymer or linear ethylene-hexene-1 copolymer and 30 to 5% by weight of high-pressure low-density polyethylene. The seal layer has a density of 0.91 to 0.
94 g/cm' linear ethylene-butene-1 copolymer or linear ethylene-hexene-1 copolymer 35-60
Heavy weight percent and low crystallinity ethylene-α olefin copolymer 25
~40% by weight and high pressure low density polyethylene 15-25
An excellent laminated film for lamination with a low-temperature heat-sealing layer, characterized by being composed of a composition consisting of
Furthermore, the laminated film is characterized in that the thickness of the heat-sealed layer ranges from 0.01 mm to 173 mm, which is the thickness of the laminated film.

Density used in the present invention: 0.91-094g, /
crn'' linear ethylene-butene-1 copolymer and linear ethylene-hexene-1 copolymer by known methods,
That is, a Ziegler catalyst consisting of a transition metal compound (compounds such as titanium or vanadium) as a main catalyst, an organometallic compound (e.g. organoaluminium) as a co-catalyst, and a carrier (e.g. an oxide of silicon, titanium, magnesium, etc.), or a chromium-based catalyst. In the presence of a catalyst etc., ethylene and butene-1
Alternatively, it can be obtained by polymerizing hexene-1 under medium or low pressure.

Polymerization is carried out in a variety of ways, such as slurry polymerization, gas phase polymerization, and high temperature solution polymerization.

Commercially available products include Ultsex, Neosex (manufactured by Mitsui Ishimagari Kagaku), Dowlex (manufactured by Dow Chemical), and NU.
Examples include C-polyethylene-LL, Tafsen (manufactured by Nippon Unicar Co., Ltd.), and the like.

The high-pressure low-density polyethylene used in the present invention is:
Ethylene alone or ethylene and propylene, butene-1,
Polymerization of inbutylene, ■-hexene, 4-methyl-1-pentene, vinyl acetate, ethyl acrylate, etc. at a pressure of 1,000 to 4,000 kg/cm2 and a temperature of 230
It is produced by polymerization in a tubular reactor or tank reactor in the presence of a radical polymerization initiator and a chain transfer agent under conditions of ~360°C, and has a crystallinity of 40 to 70 and a density of 0. 9
2-0.93g/mn, melt index 1-50
, ethylene homopolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-
These include propylene copolymer, ethylene-butene-1 copolymer, and the like.

The low crystalline ethylene-a olefin copolymer used in the present invention is a meltinde sox 01 to 50 g/
l 0m1n, density 0.870-0.900g/cm
3. Crystallinity by X-rays 5-40%, melting point 40-1
It is a random copolymer of OO'C and ethylene containing f185 to 95 mol% ethylene and an a-olefin having 3 to 10 carbon atoms.

Specifically, the a-olefin having 3 to 10 carbon atoms to be copolymerized with ethylene includes propylene, 1-butene, 1-benzone, 1-hexene, 4-methyl-1-pentene, 1
-octene, 1-decene or a mixture thereof, and particularly preferred is an a-olefin having 3 to 5 carbon atoms, especially 1-ph'thene. Melt index is 0.1 g
/ If it is less than 10 m1n, the flow characteristics are poor and a good laminated film cannot be obtained.

On the other hand, if it exceeds 50 g/10 m1n, the mechanical strength of the film will decrease, which is not desirable.

If the density is 0.870 g/cm', it is undesirable because the δ1 fat is sagging and the laminated film is blocked, and if the density exceeds 0.900 g/cm', the laminated film is bent at one side. It is undesirable because it has no effect on improving sex.

If the crystallinity is less than 5%, the laminated film will be sticky and will block, which is undesirable. If it exceeds 40%, it will not improve the bending resistance of the laminated film, which is undesirable.

The melting point determined from the endothermic curve at a heating rate of 10°C/min by DSC is 40 to 100°C, preferably 70°C.
It is necessary that the temperature is in the range of ~85°C. Melting point is 40℃
If it is less than that, the heat resistance of the laminated film will decrease, which is undesirable, and if it is too large, it will not have a heat sealing effect, which is undesirable.

The method for producing this low-crystalline ethylene-〇 olefin copolymer uses a vanadium compound such as vanadyl trichloride, monoethoxy divanadyl chloride, triethoxyvanadyl, vanadium oxydiacetylacetonate, vanadium triacetylacetonate, and the empirical formula RnAIX*- 7 (However, R is a hydrocarbon such as an alkyl group, O<n≦3, X is hydrogen,
A preferred method is to copolymerize ethylene and an a-olefin having 3 to 10 carbon atoms in the presence of a solvent using a catalyst consisting of a bad aluminum compound represented by chlorine or an alkoxy group having 2 to 4 carbon atoms. It is not limited to this. In the present invention, a composition comprising 70 to 95% by weight of a linear ethylene-hexene-1 copolymer and 30 to 5% by weight of high-pressure low-density polyethylene is used for the layer bonded to the base film.

If the linear ethylene-butene-1 copolymer or the linear ethylene-hexene-1 copolymer is 95% by weight or more, it will be difficult to produce a laminated film within 1 extrusion during production by coextrusion. The shear viscosity is high, resulting in extremely poor extrusion processability, and the elongational viscosity is extremely low, resulting in low melt tension.
For this reason, a high load is placed on the extruder during extrusion processing,
Furthermore, the film formation properties of the T-dies become unstable. That is, if the stability of the edges deteriorates, processing defects will appear and the transparency of the film will deteriorate, which is undesirable.

When the linear ethylene-butene-1 copolymer or the linear ethylene-hexene-1 copolymer is 70% or less,
This is undesirable because the heat seal strength to the base material and the mechanical strength of the film itself deteriorate.

Heat-sealability, bending resistance, heat resistance, and hot tack properties are improved only when the linear 11-type ethylene-butene-1 copolymer or linear ethylene-hexene-1 copolymer is in the range of 70 to 95% by weight. A laminated layer with well-balanced properties such as hardness, impact resistance, tear resistance, transparency, and rigidity can be obtained.

In the present invention, the heat seal layer has a density of 0.91 to 0.
94 g/cm'' linear ethylene-butene-1 copolymer or linear ethylene-hexene-1 copolymer 35-6
0% by weight and low crystalline ethylene-α olefin copolymer 2
5-40% by weight and high pressure low density polyethylene 15-2
The composition consists of 5% by weight.

If the content of the linear ethylene-butene-1 copolymer or ethylene-hexene-1 copolymer with a density of 0.91 to 0.94 g/cm' is 35% by weight or less, the mechanical properties of the heat seal layer It is undesirable because the strength becomes weak, and heat sealing strength, hot tack properties, etc. deteriorate, and when it is 60% by weight or more, low temperature heat sealing properties deteriorate, which is undesirable. If the content of the low-crystalline ethylene-α-olefin copolymer is less than 25% by weight, low-temperature heat-sealability will not be imparted, which is undesirable, and if it is more than 40% by weight, the mechanical strength of the heat-sealing layer will decrease, Undesirable.

The content of high-pressure low-density polyethylene is 15 to 25% by weight.
However, if it is less than 15% by weight, the processability in extrusion processing of the heat-sealing layer will be poor, and if it is more than 25% by weight, it will impair the mechanical strength and low-temperature heat-sealability of the heat-sealing layer, which is undesirable. .

Only when the mixing ratio of the three is within the above range, the heat seal layer's low temperature sealing properties, mechanical strength, hot tack properties, low temperature properties, bending resistance, extrusion processability, transparency, etc. can be balanced, and the present invention can be achieved. holds true.

When the laminated film for lamination of the present invention is laminated to a base material, the layer to be laminated to the base film in the first aspect of the present invention is laminated to the base material.

Examples of the bonding method include known methods such as extrusion lamination, dry lamination, sandwich lamination, and coextrusion.

The base material to which the laminated film for lamination of the present invention is laminated includes paper, aluminum foil, cellophane, high molecular weight polymer, etc., and is appropriately selected depending on the purpose and the item to be packaged.

Examples of high-molecular polymers include ultra-low density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, ionomer, polypropylene,
Polybutene-1, poly-4-methyl-pentene-1, ethylene-α olefin copolymer, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylate, polyacrylonitrile, nylon 6, nylon 66, nylon 7, nylon 10, Nylon 11, nylon 12,
Examples include nylon 610, polymethaxylylene adipamide, polyethylene terephthalate, polyethylene terephthalate-isophthalate copolymer, polybutylene terephthalate, bobbinyl alcohol, ethylene-vinyl alcohol copolymer, polycarbonate, and the like.

In the present invention, the thickness of the heat seal group is at least 0.010
mm to one-third of the thickness of the laminated film.

If it is less than 0.010 mm, the low-temperature sealability will be insufficient, and even if heat-sealing is possible at low temperatures, the adhesive strength will be weak and the heat-sealed surface will easily peel off due to weak stress or impact, which is undesirable. If it is 1/3 or more, there is no problem in terms of performance, but the expensive low-crystalline ethylene-α-olefin copolymer will be used beyond the amount required for low-temperature heat sealing, which will reduce economic efficiency. gone and undesirable.

The resin compositions constituting the laminating layer and heat-sealing layer of the present invention include heat-resistant stabilizers, antioxidants, colorants, pigments, carbon black, lubricants, processability improvers, eye discharge preventive agents, slip agents, and anti-blocking agents. Agents, antifogging agents, antistatic agents, nucleating agents, etc. may be added depending on the purpose and use.

Examples are shown below.

Example 1 Linear ethylene-butene-1 copolymer (NUCG-5222 manufactured by Nippon Unicar, MI = 2.0, density 0.921
)95% by weight and high pressure low density polyethylene (DFD-0148 manufactured by Nippon Unicar, MI=6.3, density 0.922
) 5% by weight, and an antioxidant (I RGANOXl 01
0.5ANDO3TAB-PEPQ 0.05% by weight each
) and laminated onto the base film.

On the other hand, linear ethylene-butene-1 copolymer (NUCG-5222 manufactured by Nippon Unicar, MI=20, density 0.92
1) High pressure process low density polyethylene with 35% heavy weight (Nippon Unicar: #DFD-OI48, MI=6.3, density 0.9
22) 25% by weight and low crystalline ethylene-α olefin copolymer (Tafmer A-4085 manufactured by Mitsui Petrochemicals, MI
= 37, density 0.88) 40% by weight and antioxidant (r
RGANOX 1010.5ANDO3TABPEPQ
0.05% by weight of each) to prepare a heat-sealable Ishikawa resin composition (B).

The resin compositions A and B were laminated and extruded from a T-die using a one-way coextruder with a companing adapter under the following conditions to obtain a two-layer film.

Extrusion processing conditions The heat-sealing layers of this two-layer laminated jΔ film were heat-sealed under the following conditions, and the peel strength of the heat-sealed portion was measured in Table 1.
It was shown to.

Heat seal separation test method Beat sealer Hot plate sealer Sealing pressure ],, OKg/cm2 Sealing time 10 seconds Lower bar temperature 50°C Seal width 5 mm After heat sealing, let it cool, cut out a 15 mm wide test piece, and check the tensile speed The strength was measured when the heat-sealed portion was peeled off at 500 mm/min.

In addition, the tear strength, impact strength, haze, and blocking properties of the stacked stone film were measured by the following methods and are shown in Table 1.

Hirotsuji Shigeki (Elmendorf: Kg/cm) JIS P
8116 1! Strength (Kg°Cm/Cm) ASTM D 1709A to -1's (%): ASTM D 10037'O
Based on the sensory test on ye21.

The state in which the film is stuck is O6, and the state in which the film is moderately separated is O6.Next, the previously produced laminated film and a 0.012 mm thick film made of polyethylene terephthalate (PET) are bonded to high-pressure low-density polyethylene (NUC-8 manufactured by Nippon Unicar).
008, MI=4.7, density 0.917) as an intermediate layer, sandwich lamination was performed, and the peel strength of this intermediate layer was measured and shown in Table 1.

Examples 2 to 12 The linear ethylene-butene-1 copolymer of Example I was replaced with a linear ethylene-hexene-1 copolymer, and the weight percent of each resin in the composition was shown in Table 1. Change as shown,
The results were shown. It is clear from the results in Table 1 that within the numerical range of the present invention there is a good effect.

Comparative Example 1 An experiment similar to Example 5 was conducted except that the thickness of the heat seal layer was 0.005 mm. Since the heat seal layer is thin, peel strength is not sufficient.

Comparative Example 2 Since no high-pressure low-density polyethylene was used in the layer to be laminated to the base film, only linear ethylene-butene-1 copolymer was used, so the peel strength between the base film and the base film was not sufficient. do not have.

Comparative Example 3 Since the layer laminated to the base film contained 40% by weight of high-pressure low-density polyethylene, the tear strength and iΦi impact strength of the stacked stone film decreased.

Comparative Example 4 In the heat seal layer, linear ethylene-butene-1
Since the copolymer's claw strength decreased to 25%, the blocking properties of the laminated film deteriorated.

Comparative Example 5 In the heat-sealing layer, the amount of low-crystalline ethylene myolefin copolymer was reduced to 20% by weight, so the heat-sealing strength was reduced.

[Operations and Effects of the Invention] In the present invention, the structure of the laminated film for lamination is two layers, and the heat-sealed portion is made extremely thin, so the amount of expensive low-crystalline ethylene-α-olefin copolymer used is extremely reduced. Since only a small amount is required, costs can be reduced, and the bonding layer to the base material can be made of linear ethylene-butene-1 copolymer or linear ethylene-hexene-1 copolymer and high-pressure low-density polyethylene. Because the structure is made of a resin composition, it has excellent mechanical strength, impact resistance, interlayer adhesion, pinhole resistance, and face-blocking properties, as well as low-temperature sealing properties and economical properties, which are the physical properties required for the laminated film. An excellent laminated film for lamination with well-balanced properties can be obtained.

Claims (2)

[Claims] (1) In a laminated film for lamination consisting of a layer to be laminated to the base film and a heat sealing layer for imparting low-temperature heat-sealability to the base film, the layer to be laminated to the base film has a density of 0. From 70 to 95% by weight of linear ethylene-butene-1 copolymer or linear ethylene-hexene-1 copolymer of 91 to 0.94 g/cm^3 and 30 to 5% by weight of high-pressure low density polyethylene The heat seal layer has a density of 0.91 to 0.94 g/cm^
35 to 60% by weight of linear ethylene-butene-1 copolymer or linear ethylene-hexene-1 copolymer and 25 to 40% by weight of low-crystalline ethylene-α-olefin copolymer
A laminated film for lamination with excellent low-temperature heat-sealing properties, characterized by comprising a composition comprising 15 to 25% by weight of high-pressure low-density polyethylene. (2) The laminated film for lamination according to claim (1), wherein the thickness of the layer laminated to the base material is from 0.01 mm to 1/3 of the thickness of the laminated film.