JPH0292943A - Polyolefin composition and laminated body thereof - Google Patents

Abstract

PURPOSE:To obtain a laminated body, consisting of a propylene-based polymer, ethylenic polymer and ethylene.alpha,beta-unsaturated carboxylic acid copolymer (metal salt), excellent in hermetic sealing and easy unsealing properties, heat and oil resistance and suitable as sealing materials. CONSTITUTION:A composition consisting of (A) 20-70 pts.wt. propylene-based polymer, preferably copolymer of propylene and ethylene or a 4-8C alpha-olefin having 0.5-100g/10min melt flow rate, (B) 20-60 pts.wt. polyethylene or ethylene.alpha-olefin copolymer, preferably a copolymer, having 0.9-0.96g/cm<3> density and 0.5-100g/10min melt flow rate and produced by a middle- and low-pressure process and (C) 5-40 pts.wt. ethylene.alpha,beta-unsaturated carboxylic acid copolymer (metal salt) having preferably 0.5-100g/10min melt flow rate. The above- mentioned composition is laminated to a substrate layer to provide a laminated body.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyolefin composition suitable as an easily openable sealing material, and a laminate in which the composition is laminated on a base resin layer.

Technical background of the invention and its problems There are many types of film materials for food packaging, and there are various proposals regarding single-layer films or multi-layer films.

Generally, heat sealing is performed at the sealing stage, so heat-sealable materials are commonly used for single-layer films, and for multi-layer films, the innermost layer is a heat-sealable material. Those formed with this are commonly used.

Known examples of such heat-sealing materials include polyolefin polymers such as polyethylene and polypropylene, and resin compositions in which these general-purpose polyolefins are mixed with ethylene-vinyl acetate copolymer, polybutene-2, and the like.

By the way, there are cases where the heat-sealing surface is formed of a different material, and cases where the heat-sealing surface is formed of the same material, such as packaging bags for potato chips, instant ramen noodles, snack foods, and the like. As an example of the former, in order to package foods such as tofu, jelly yokan, and sweets, a synthetic resin film as a lid is usually adhered to a container made of polypropylene or the like. When the above-mentioned resin or resin composition is used as such a film, there is a problem that the sealing strength between the container and the lid is stronger than necessary, making it impossible to open the container by hand.

For this reason, various types of easy-to-open sealing materials have been proposed, but in general, easy-to-open sealing materials have poor sealing properties, or the adhesion strength decreases significantly when foreign matter gets into the heat-sealed surface. Alternatively, when the adhesive is heated in hot water, the adhesive strength is significantly reduced. Furthermore, when sealing is performed by heating the heat-sealing surface, there is a problem that the temperature range in which an appropriate sealing strength is achieved is narrow.

For example, heat-sealable resin compositions containing tackifier resins have been proposed, but their use has been limited because they generally have poor heat resistance and oil resistance. In addition, as a system not containing a tackifying resin, for example, JP-A No. 80-2392
Publication No. 38 states that the melt index is 0.5 to 100.
g / 10 minutes, with a heat seal layer formed by mixing 5 to 65 parts by weight of an ethylene-propylene copolymer with an ethylene content of 1 to 50% by weight to 100 parts by weight of an ionomer resin, which has an ethylene content of 1 to 50% by weight. An easy-open sealing material using an olefin resin as a sealant is disclosed.

However, this easy-open sealing material has not always been fully satisfactory in terms of sealability, easy-openability, and the like.

Furthermore, many of the easy-open sealing materials that have been proposed in the past should normally be applied when heat-sealing different materials, and there are some that do not show easy-opening properties when heat-sealing the same material. It was almost.

Purpose of the Invention The present invention is intended to solve the problems associated with the prior art as described above. Another object of the present invention is to provide a polyolefin composition that can be used as a sealing material with excellent sealing properties, easy opening properties, heat resistance, and oil resistance.

Another object of the present invention is to provide a laminate which itself can be used as an easily heat-sealable and easy-open packaging material such as a packaging bag or a lid.

Summary of the Invention The polyolefin composition according to the present invention comprises 20 to 70 parts by weight of a propylene polymer and 20 to 60 parts by weight of polyethylene or an ethylene/α-olefin copolymer mainly composed of ethylene.
Parts by weight and ethylene α.

β-unsaturated carboxylic acid copolymer or metal salt thereof 5-40
Parts by weight (100 parts by weight in total). Further, the laminate according to the present invention is characterized in that the polyolefin composition layer is laminated on a base material layer.

DETAILED DESCRIPTION OF THE INVENTION The polyolefin composition according to the present invention and the laminate formed by laminating the polyolefin composition will be specifically described below.

The propylene polymer used in the present invention is a highly crystalline polymer selected from propylene homopolymers and copolymers mainly composed of propylene, and copolymers are particularly preferred.

As the propylene polymer, a copolymer of propylene and ethylene and/or an α-olefin having about 4 to 8 carbon atoms is used, and the content of ethylene or α-olefin is 0.5 to 20 mol%, Preferably it is 1 to 10 mol%.

Such a propylene polymer has a melt flow rate (230°C, 2160g load) of 0°1 to 500g.
/ 10 minutes, preferably about 0.5 to 100 g/10 minutes.

The polyethylene or the ethylene/α-olefin copolymer mainly composed of ethylene used in the present invention is obtained by homopolymerization of ethylene or copolymerization of ethylene and α-olefin by a high-pressure method or a medium-low pressure method.

It is desirable that its density is usually 0.88 to 0.98 g/aa, preferably 0.90 to 0.96 g/aJ. In addition, this polyethylene or ethylene/α-olefin copolymer has a melt flow rate of 0.1 to 500 g/10 minutes at 190°C and a load of 2160 g.
It is particularly preferable to use an ethylene polymer of about 0.5 to 100 g/10 minutes, and it is more preferable to use an ethylene/α-olefin copolymer produced by a medium-low pressure method.

Examples of the a-olefin component in the ethylene/α-olefin copolymer include propylene, l-butene, l-hexene, -octene, 1-decene, and 4-methyl-1-pentene.

The ethylene/α,β-unsaturated carboxylic acid copolymer or metal salt thereof used in the present invention is also α.

It may contain β-unsaturated carboxylic acid ester or carboxylic acid vinyl ester as a copolymerization component.

Examples of the above α,β-unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, and monomethyl maleate.

Examples of α,β-unsaturated carboxylic acid esters include alkyl esters of acrylic acid or methacrylic acid having 1 to 8 carbon atoms, such as esters such as methyl, ethyl, propyl, n-butyl, isobutyl, and 2-ethylhexyl. can do. Further, as the carboxylic acid vinyl ester, acetic acid vinyl ester can be given as a representative example.

Examples of metal salts include monovalent metal ions such as lithium, sodium, potassium, and cesium, divalent metal ions such as zinc, copper, magnesium, calcium, strontium, and barium, and trivalent metal ions such as ammonium and iron. can be used. Such a copolymer contains 85 to 99.5 mol% of ethylene units, especially 94 to 99 mol% of ethylene units, and 0 α,β-unsaturated carboxylic acid units.
．． Use a copolymer containing 5 to 15 mol%, especially 1 to 6 mol%, and 0 to 10 mol%, especially 0 to 6 mol% of other monomers, or the degree of neutralization is 100% or less, especially 80 mol%.
% or less is preferable.

More specifically, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-ethyl acrylate-acrylic acid copolymer, ethylene-isobutyl acrylate-methacrylic acid copolymer, or salts thereof, etc. can be given as an example.

These copolymers or metal salts thereof preferably have a melt flow rate of about 0.1 to 500 g/10 minutes, particularly about 0.5 to 100 g to 10 minutes at 190°C.

In the polyolefin composition according to the present invention, the propylene polymer is 20 to 70 parts by weight, preferably 30 to 6 parts by weight.
0 parts by weight, polyethylene or ethylene/α-olefin copolymer: 20 to 60 parts by weight, preferably 25 to 50 parts by weight, ethylene/α,β-unsaturated carboxylic acid copolymer or metal salt thereof: 5 to 40 parts by weight Parts by weight, preferably 10-30
parts by weight (total of 100 parts by weight). If the amount of the propylene polymer is less than 20 parts by weight, it will not exhibit adequate sealing strength in a wide temperature range, and delamination may occur between the polypropylene layer and the sealing layer when coextruded with polypropylene. On the other hand, if it exceeds 70 parts by weight, it does not exhibit excellent ease of opening and does not exhibit adequate sealing strength in a wide temperature range, which is not preferable.

On the other hand, if the amount of polyethylene or ethylene fiber α-olefin copolymer is less than 20 parts by weight, the sealing strength will be weak, while if it exceeds 60 parts by weight, it will not exhibit excellent easy-opening properties and will not be able to be sealed over a wide range of sealing temperatures. This is not preferable because it does not exhibit adequate sealing strength in this area.

Furthermore, if the amount of the ethylene/α,β-unsaturated carboxylic acid copolymer or its metal salt is less than the above range, it will not exhibit excellent ease of opening and will not exhibit adequate sealing strength in a wide temperature range. On the other hand, if it exceeds 40 parts by weight, the sealing strength becomes too weak, which is not preferable.

The composition according to the present invention can be prepared by tri-blending or melt-blending the above-mentioned components simultaneously or sequentially. In the case of triblends, the blend is melt-plasticized in a molding machine, uniformly melt-mixed, and extruded. In the case of melt blending, melt mixing may be carried out using a single screw extruder, a twin screw extruder, various mixer rolls such as a Banbury mixer, various kneaders, etc., and there is no particular restriction on the mixing order.

It is also possible to add antioxidants, weather stabilizers, lubricants, antifogging agents, etc. to the polyolefin composition according to the present invention within a range that does not impair the performance of the composition.

The polyolefin composition thus obtained is applied onto a substrate such as polypropylene, polyethylene terephthalate, polyvinylidene chloride, saponified ethylene-vinyl acetate copolymer, polyamide, aluminum foil, metallized film, etc., as necessary. High pressure polyethylene, ethylene-α.

They are laminated via a resin such as a β-unsaturated carboxylic acid copolymer or an adhesive such as an anchor coating agent.

The method for producing the laminate is not particularly limited, but when the composition according to the present invention is used in the sealing layer, it can be carried out, for example, by the following method.

(1) Heat fusion method When a pre-formed base material and a sealing layer film are made into a laminate using an adhesive, a method of thermocompression bonding the base material, adhesive, and sealing layer film, or a method of bonding the base material, an adhesive, and a sealing layer film. A method is adopted in which an adhesive is previously laminated on at least one surface of the sealing layer by a coextrusion method, an extrusion coating method, etc., and then thermocompression bonding is performed.

(2) Sandwich lamination method This is a method in which a base material and a sealing layer are bonded together via a molten adhesive film using a T-die method or the like.

(3) Co-extrusion method This is a method in which a base material and a sealing layer, or a base material, an adhesive layer, and a sealing layer are laminated by a co-extrusion molding method.

(4) Adhesive method This is a method in which an adhesive is applied to at least one surface of the base material or sealing layer, and the adhesive is pressed and bonded.

Of course, these methods include, for example, (4) bonding a base material coated with an adhesive using the adhesive method with a sealing layer via a molten film of another adhesive using the (2) side-deutsche lamination method. It is also possible to use it in combination with.

In particular, when a base material such as polypropylene is used, the layers can be laminated by a coextrusion lamination method.

In order to improve the adhesion of the base material and the seal layer, the surfaces thereof may be subjected to a known method such as corona treatment in advance.

The thickness of the sealing surface is not particularly limited, but is generally 5 to 2
00 μm, preferably about 10 to 50 μm. Although the thickness of the base material surface is also arbitrary, it is generally about 2 to 500 μm, preferably about 5 to 100 μm.

The sealing material made of the laminate thus obtained can be bonded to the same sealing material, and in this case as well, the bonded surface exhibits easy-to-open properties. That is, the laminated layers formed on the base material using the composition as a heat-sealing surface can be heat-sealed so that the heat-sealing surfaces are in contact with each other, and the bonded surfaces heat-sealed in this way have an excellent seal. It has properties and is easy to open.

Moreover, when sealing materials having the composition according to the present invention on a base material as a heat-sealing surface are heat-sealed, appropriate sealing strength is exhibited over a wide temperature range, for example, from 130 to 160°C.

Even when the laminate obtained as described above is adhered to a polyolefin resin with the composition side of the present invention as the heat-sealing surface, the bonded surface has excellent sealing properties and exhibits easy unsealability. .

As the polyolefin resin for the mating surface, polypropylene, low density polyethylene, ethylene-vinyl acetate copolymer, etc. are used, and these polyolefin resins are usually shaped like the container body.

When the laminate according to the present invention is used as a sealing material as described above, it is usually used as a lid for a container body as described above.

When heat-sealing in such a usage mode, appropriate sealing strength is exhibited over a wide temperature range, for example, 140 to 200°C. Moreover, the obtained bonded body has an excellent property that the adhesive strength does not decrease significantly even when heated in hot water or in a microwave oven.

Effects of the Invention When the polyolefin composition according to the present invention is used in a heat-sealing layer, excellent sealing properties can be achieved both when the heat-sealing layers are heat-sealed together and when heat-sealing against an olefin resin. , has excellent ease of opening and exhibits appropriate sealing strength over a wide temperature range.

Since such a heat-sealing surface has excellent heat resistance and oil resistance, it is suitable for packaging materials for oil-based foods or packaging materials that are heated.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

The polymers used in the examples and the method for measuring seal strength are shown below.

(1) Polymer used (8) Acid copolymer diethylene methacrylic acid copolymer (acid content: 9% by weight), and MFR is 3 g/10 minutes.

(b) Medium-density polyethylene: Medium-density polyethylene manufactured by Mitsui Petrochemical Industries Ltd. (Neozex: NZ3510F), the density is 0.935 g/aa, and the MFR is 1.
It is 6g/10 minutes.

(C) Low pressure low density polyethylene (LLDPE)
: LLDPE manufactured by Mikata Petrochemical Industry ■ (Urtozex: VZ1520L) Yes, density? ! 0. 915
g/cAte, and MFR is 2.0 g/10 min.

(d) Ethylene material-butene copolymer: Density is 0.88 g
/-, and the MFR is 3.69 g/10 minutes.

(e) Polypropylene: Polypropylene F65.8 (propylene/ethylene random copolymer) manufactured by Mitsui Petrochemical Industries, Ltd., density is 0.91 g/-, MFR
is 6.0g/10 minutes.

(2) Measurement of sealing strength (a) Measuring method of two-sided heat sealing strength Using a single-sided heating type heat sealer, sealing temperature:
i2o 130 140 150160 170 1
Heat sealing was performed on each side under the following sealing conditions: 80°C, seal pressure (actual pressure): 72 kg/cd, seal time: 0.5 seconds, seal bar width: 10 times.

In addition, the seal strength was measured using a specimen in 15III under conditions of a tensile speed of 300 fins and 7 m1n.

(b) Measuring method of sealing strength for polypropylene trays Measurement was carried out using a single-sided heating type tray heat sealer.

Tray used: Made of polypropylene (height 80 x width 110 x depth 40 mm) Seal temperature: 160℃, 180℃ Seal pressure 4 dazzles / cj Seal time: 1 second Seal width: 3m ■ The sealing performance is simply the lid material. When the film was sealed on the tray, when the tray was completely filled with water and sealed, and when the water-filled tray was left in an autoclave at 120°C for 30 minutes, blank, water-filled (water-filled contaminants) ) Sealing performance and three sealing performances after sealing after retort processing were evaluated.

The seal strength was measured using a 15 m wide specimen at a tensile speed of 300 am/sin.

Example 1 20 parts by weight of acid copolymer, 40 parts by weight of medium density polyethylene, and 40 parts by weight of polypropylene were heated at a resin temperature of 180 parts by weight.
The mixture was melt-kneaded using a single-screw extruder at ℃. This composition was molded into a 30 μm thick film using a T die-cast film molding machine at a resin temperature of 230°C.
Corona treatment was applied to one side.

Next, use a dry laminator to apply the above created film,
A 12 μm thick polyethylene terephthalate film coated with an anchor coating agent was attached.

The obtained laminate was heat-sealed face-to-face using a film layer of a composition consisting of an acid copolymer, medium density polyethylene, and polypropylene as a sealing layer, and the sealing strength was measured using a tensile tester.

Similarly, a polypropylene tray was heat-sealed, and the sealing strength was measured using a tensile tester. (Blank, water contaminant seal, seal after retort treatment) The results are shown in Tables 1 and 2.

From Tables 1 and 2, it can be seen that the composition of Example 1 has excellent sealing properties in terms of heat-sealing performance, excellent ease of opening, and moderate sealing strength in a wide temperature range. .

Similarly, Tables 1 and 2 show that the composition of Example 1 has excellent sealing properties and easy opening properties even for polypropylene trays, and has a moderate sealing property in a wide temperature range. It can be seen that the sealing strength is 100%, and that even when foreign substances enter the sealing surface, it shows excellent sealing performance, and the sealing strength does not decrease significantly even when exposed to retort conditions.

Example 2 In Example 1, the acid copolymer, medium density polyethylene,
The same test as in Example 1 was conducted except that the ratio of polypropylene used was changed to 10:50:40.

The results are shown in Tables 1 and 2.

Example 3 The same test as in Example 1 was conducted except that low-pressure low-density polyethylene was used instead of medium-density polyethylene.

The results are shown in Tables 1 and 2.

Example 4 In Example 2, the resin used was medium density polyethylene 50
The same test as in Example 2 was conducted except that 40 parts by weight of medium density polyethylene and 10 parts by weight of ethylene/l-butene copolymer were used instead of parts by weight.

The results are shown in Tables 1 and 2.

Comparative Examples 1 and 2.3 In Example 1, the ratio of acid copolymer, medium density polyethylene and polypropylene was changed to 3:20 near 7 (
The same test as in Example 1 was conducted except that the ratio was changed to Comparative Example 1), 50:10:40 (Comparative Example 2), or 30:60:10 (Comparative Example 3).

The results are shown in Tables 1 and 2.

Claims (2)

[Claims] (1) 20 to 70 parts by weight of a propylene polymer, 20 to 60 parts by weight of polyethylene or an ethylene/α-olefin copolymer mainly composed of ethylene, and an ethylene/α,β-unsaturated carboxylic acid copolymer or its metal A polyolefin composition containing 5 to 40 parts by weight of salt (100 parts by weight in total). (2) In the base material layer, 20 to 70 parts by weight of a propylene polymer, polyethylene or ethylene mainly composed of ethylene, α
-20 to 60 parts by weight of olefin copolymer and ethylene.
α,β-unsaturated carboxylic acid copolymer or its metal salt 5~
A laminate formed by laminating layers of a polyolefin composition blended at a ratio of 40 parts by weight (100 parts by weight in total).