JPS5844462B2 - Manufacturing method of laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a laminated film containing a uniform, ultra-thin vinylidene chloride resin layer.

Conventionally, a vinylidene chloride resin layer has been interposed in a laminated film as a barrier layer against gas or moisture.

However, in general, a vinylidene chloride resin layer has a severe drawdown phenomenon when melted, so it is extremely difficult to melt-extrude it to a uniform thickness of 3 microns or less.

Furthermore, compared to other resins, vinylidene chloride resin is much more expensive due to the complexity of the monomer manufacturing process and polymerization process. It is almost impossible to compete with relatively inexpensive resin films such as nylon in the same application, and even if you take into account the fact that it has highly excellent barrier properties against gas and moisture, it is still difficult to compete with relatively inexpensive resin films such as nylon. could not be accepted by the world.

Therefore, although laminated films with this as a barrier layer, such as coextruded laminated films or Lamiho 1-films, are recognized as packaging materials with excellent physical properties, it is extremely difficult to find a place where they can be used. there were.

An object of the present invention is to form a vinylidene chloride resin layer of a laminated film having a vinylidene chloride resin layer as an inner layer into a uniform thin layer.

Another object of the present invention is to improve the gas and moisture barrier properties of a thin vinylidene chloride resin layer.

The ultimate objective of the present invention is to make a laminated material having a vinylidene chloride resin layer usable on T leaves.

In the present invention, vinylidene chloride resin is the central layer, and on both sides, ethylene-vinyl acetate copolymer resin, copolymer resin of ethylene and unsaturated carboxylic acid or its metal salt, and ethylene-unsaturated carboxylic acid ester copolymer resin A resin layer of 5 to 30 microns consisting of one or more mixed resins of styrene-butadiene block copolymer resins is laminated, and the vinylidene chloride resin layer with a total thickness of 5 to 30 microns is further laminated on the outer peripheral surface thereof. Thermoplastic resins selected from polyolefin resins, polystyrene resins, and polyamide resins thicker than the thickness of This is a method for producing a laminated film having an extremely thin vinylidene chloride resin layer, which is characterized by stretching the film in a heating zone in a uniaxial or biaxial direction at a temperature higher than the softening temperature of both surface resins.

In the present invention, the vinylidene chloride resin refers to a copolymerized or multicomponent copolymerized resin containing at least 60% (weight percent, same hereinafter) of vinylidene chloride.

Furthermore, ethylene-vinyl acetate copolymer resin, copolymer resin of ethylene and unsaturated carboxylic acid or its metal salt, ethylene-unsaturated carboxylic acid ester copolymer resin, and styrene-butadiene block copolymer resin are arranged on both sides of the resin. All of these are molten and inseparably adhere to vinylidene chloride resins, polyolefin resins, polyamide resins, and polystyrene resins.

In the present invention, the ethylene-vinyl acetate copolymer resin, the copolymer resin of ethylene and unsaturated carboxylic acid or its metal salt, and the ethylene-unsaturated carboxylic acid ester copolymer resin each have an ethylene content of 60 to 90%. , and its unsaturated carboxylic acids include acrylic acid and methacrylic acid, and its metal salts include sodium, subsalt,
Examples of salts such as calcium and unsaturated carboxylic acid esters include ethyl acrylate, methyl methacrylate, and inbutyl acrylate.

The styrene-butadiene block copolymer resin 1 has a styrene content of 30 to 50%.

In the present invention, the laminated thickness of this glue layer during extrusion is set in the range of 5 microns to 30 microns.

This limitation of thickness is important.

If the thickness of the glue layer is less than 5 microns, the adhesion between the center layer and the surface layer will not be sufficient, and peeling will easily occur even when subjected to a slight external impact, especially after stretching.

In addition, if the thickness exceeds 30 microns, the vinylidene chloride resin layer in the center layer will not stretch uniformly during the subsequent stretching process, and will become partially thick and thin, and in extreme cases may crack partially. A region is created in which the central layer has been lost.

The reason for this is that during forced stretching, the thick surface layer actively stretches, and the center layer stretches accordingly, but since the glue layer is thick, it oscillates, and the center layer stretches evenly. This is thought to be because it is not carried out.

Another role of these glue layers is to facilitate the exudation of the low-molecular plasticizer contained in the vinylidene chloride resin during the subsequent heating and stretching of the laminated film, and to retain the exuded plasticizer in the layer. It is to be.

In general, vinylidene chloride resins have poor thermal stability and processability during melt extrusion processing, so the molecular weight of
It is essential to add a low-molecular plasticizer with a molecular weight of 500% or less, such as dioctyl sebacate, dibutyl sebacate, acetyl tributyl citrate, and epoxidized vegetable oil, but these plasticizers have a high thermal stability and processability during melt extrusion. It is known that, on the other hand, it reduces the gas barrier properties and moisture barrier properties of vinylidene chloride resins.

Furthermore, these low-molecular plasticizers have the property of leaching out from the inside of the vinylidene chloride resin film to the surface thereof over time, particularly when it is exposed to heat.

In the laminated film produced by the production method of the present invention, a glue layer is used to facilitate the exudation of the plasticizer and to prevent the plasticizer from further migrating to the surface layer and coming into contact with the package contents, etc. Retained in resin body.

Due to this action of the glue layer, the barrier force per unit thickness of the vinylidene chloride resin layer after heating and stretching becomes much larger than that before heating and stretching.

The difference in the oxygen permeability of the laminated film before and after the heat stretching is extremely significant, as shown in the examples below.

A polyethylene resin, a polypropylene resin, a polystyrene resin, or a polyamide resin can be used as the thermoplastic resin laminated on both outer surfaces of the glue layer.

Here, the polyethylene resin includes a copolymer containing 60% or more of ethylene, a multicomponent polymer, an ionomer having metal ion crosslinks, and the like.

Further, polypropylene resin and polystyrene resin both include copolymers and multicomponents containing 60 or more propylene or styrene.

Lamination and extrusion are performed so that the total thickness of these surface layers is thicker than the thickness of the center layer.

This is a requirement to actively stretch both surface layers during the subsequent stretching, and to stretch the glue layer and the center layer dependently on this stretching, and the total thickness of both surface layers must be smaller than the thickness of the center layer. If so, the traction properties against the center layer are low, and both the surface layer and the center layer tend to stretch partially unevenly, and both layers tend to crack.

In the present invention, after extruding the laminated film having the above structure through a goo, it is passed between a cooling roll and an air nozzle that injects cold air toward the cooling roll directly below the die.

This is an essential requirement in order to prevent the thickness of the vinylidene chloride resin layer in the center layer and the glue layer from deteriorating.

As mentioned above, vinylidene chloride resins and resins that form a single layer of glue, which have such high fluidity that they draw down when melted, can be made into a film by simply winding them around cooling rolls or compressing them between cooling rolls. If air is partially allowed to enter between the roll and the film, the film will partially bulge, and the highly fluid resin will flow and solidify in response to the distortion, resulting in uneven thickness. This easily causes cracks to occur in the center layer during subsequent stretching.

The surface temperature of the cooling roll, the temperature of the cold air, the air volume, and the pressure are adjusted depending on the material, thickness, etc. of both surface layers, but the temperature is 0~
The temperature is 30° C., and the air volume and pressure may be within a range that can suppress the film to the roll to an extent that prevents air from entering between the roll and the film.

Moreover, the cold air temperature and the roll surface temperature do not necessarily have to be the same.

The laminated film is then stretched in a heating zone provided in front of a pair of pinch rolls.

This stretching may be sequential biaxial stretching using tenter clips, longitudinal stretching using two pairs of pinch rolls with different surface rotation speeds, and biaxial stretching using tenter clips alone. Stretching may also be used.

Stretching is carried out in a heating zone.

The temperature inside the oven is set to be equal to or higher than the softening temperature of the resin on the higher softening point side of both surface layers.

The film heated and stretched in this manner does not shrink at temperatures below oven temperature.

However, if the film is expected to be stored, used, displayed, etc. at a temperature higher than that temperature, and the film must not shrink, it is subjected to tension heat treatment at a temperature higher than the above oven temperature after stretching.

This temperature is preferably about 10° C. higher than the temperature at which the product is stored, used, and displayed.

Next, examples of the present invention will be shown.

Example 1 15 microns made of a vinylidene chloride copolymer resin made by adding 1.5 parts by weight of dioctyl adipate and 2.5 parts by weight of dibutyl sebacate to 100 parts by weight of a copolymer of 83 parts of vinylidene chloride and 17 parts of vinyl chloride. The inner layer and both sides are coated with ethylene containing vinyl acetate of 26%.
A 6 micron layer of vinyl acebuto copolymer resin, and a 20 micron layer of ethylene-propylene copolymer resin with an ethylene content of 5 parts and a randomness index of 0.45 on one outer side, and on the other side. A 250 micron layer of isotactic polypropylene resin with an intrinsic viscosity of 2.5 in Tetocillin was melt extruded from a T-die at 135°C, and an air nozzle with an ejected air temperature of 15°C was arranged at 10°C. Pass it through a casting roll, then
Stretched 3 times in the longitudinal direction in a heating zone of 145°C,
Next, in the heating zone of 155℃, 3 times in the horizontal direction, a total of 9
It was stretched twice and subjected to tension heat treatment at 165°C.

The obtained film has excellent transparency, stiffness, gloss, and scratch resistance, and has an oxygen permeability of 20 (cc,
/r1.・24hr, 23℃), water vapor transmission rate 0.9
(?/rrl ・24 hr), oxygen transmission rate 3
6 (cf:,,/i・24hr, 23℃), water vapor permeability 4.7 (t/d・24hr), heat sealing strength between ethylene-propylene copolymer resin layers at hot plate temperature 1
A value of 2.5 (for 715 kg) was obtained at 50° C., a pressure of 1 kg/cdl, and a sealing time of 0.5 seconds.

In addition, four plates of 1 d each were randomly cut from this film, and the thickness of the vinylidene chloride resin layer at 10 randomly selected measurement positions from each was extremely uniform with an average thickness of 1.7 microns and a sigma of 0.05 microns. Met.

Example 2 Consisting of a vinylidene chloride copolymer resin made by adding 2.3 parts by weight of dibutyl sebacate and 12.0 parts by weight of acetyl tributyl cider to 100 parts by weight of a copolymer with 83% vinylidene chloride and 17% vinyl chloride. A 15 micron inner layer, a 6 micron layer of ethylene-vinyl acetate copolymer resin with a vinyl acetate content of 20 on both sides, and an ethylene content of 501 on both outer sides.
A 90 micron layer of ethylene-propylene copolymer resin was placed and melt extruded from a T-die, with the blowing air at a temperature of 20°C.
After passing through a 20°C casting roll equipped with an air nozzle, the film was stretched 3 times in the longitudinal direction in a 145°C heating zone, and then 3 times in the transverse direction in a 155°C heating zone, for a total of 9 times. was carried out and subjected to tension heat treatment at 165°C.

The obtained film has excellent transparency and gloss, and the oxygen permeability of the film before stretching is 20 (c4/i・24hr,
23℃), water vapor transmission rate 1.8 ('?/i ・24h
r), the oxygen permeability is 30 (CC,/ffl ・2
4hr, 23℃), water vapor transmission rate 9 ('?/d・24
h r ), and is currently capable of overlapping sealing, and its heat sealing strength is at a hot plate temperature of 15
0°C, pressure 1 kg/ctA.

i, 0 (kg/us width) at seal time 0.5 seconds
Met.

Further, four sheets were randomly cut from this film for each door, and the thickness of the vinylidene chloride resin layer at 10 measurement positions randomly selected from each was 1.7 microns on average, and sigma -0.05 microns.

Example 3 10 consisting of a vinylidene chloride copolymer resin in which 1.5 parts by weight of dioctyl adipate and 2.5 parts by weight of dibutyl sebacate were added to 100 parts by weight of a copolymer of 85 parts vinylidene chloride and 15% vinyl chloride. micron inner layer,
A 7 micron layer of ethylene-ethyl acrylate copolymer resin with an ethyl acrylate content of 20% on both sides,
Furthermore, one side of the outside is coated with Surlyn A 1652 resin 160.
A micron layer and a 60 micron layer of 6-nylon resin on one side were melt-extruded from a T-die, passed through a casting roll at 15°C equipped with an air nozzle with ejected air at a temperature of 15°C. In a heating zone at 120°C, the film was heated and stretched by a total of 4 times, twice in the longitudinal direction and twice in the transverse direction, and subjected to tension heat treatment at 130°C.

The obtained film has excellent transparency, oil resistance, and pinhole resistance, and has an oxygen permeability of 10 (cc, /rrf) before stretching.
・24hr, 23℃), water vapor transmission rate 3.0 (?
/rd 14hr) to oxygen permeability 17(cc,
/i + 24hr, 23℃), water vapor transmission rate 8 (
1/d・24hr).

In addition, the seal strength of Surlyn A comrades is at a hot plate temperature of 150°C.
3 at a pressure of 1 kg/crA and a sealing time of 0.5 seconds.
．． 0 (kg/15 mm width).

The thickness of the vinyl chloride resin layer was measured in the same manner as in Examples 1 and 2 and was found to be an average of 2.5 microns and a sigma of 0.07 microns.

Example 4 10 consisting of a vinylidene chloride copolymer resin in which 1.5 parts by weight of dioctyl adipate and 2.5 parts by weight of dibutyl sebacate were added to 100 parts by weight of a copolymer of 83% vinylidene chloride and 17 parts by weight of vinyl chloride. A T-die is formed by forming a micron inner layer, a 10 micron layer of styrene-containing 40% styrene-butadiene block copolymer resin on both sides, and a 900 micron layer of polystyrene copolymer resin on both outer sides. The material was melt extruded, passed through a casting roll at 10°C equipped with an air nozzle with an ejected air temperature of 15°C, then heated and stretched 2.5 times in the longitudinal direction in a heating zone of 125°C, and further stretched in a heating zone of 135°C. Heat stretching was performed in the transverse direction by 2.5 times, a total of 6.25 times.

The obtained film has excellent thermoformability and barrier properties, and has an oxygen permeability of 28 (cc/i ・24hr, 23
°C), water vapor transmission rate 2.2 (f/rrf ・24hr
), oxygen permeability 42 (cc, /i ・24hr,
23℃), water vapor transmission rate 11 (r/771'・24h
r).

The thickness of the vinylidene chloride resin layer was measured in the same manner as in Examples 1 and 2 and was found to be 1.6 microns on average and sigma -0.05 microns.

Example 5 From a vinylidene chloride copolymer resin in which 41.5 parts by weight of dioctyl adipe and 2.5 parts by weight of dibutyl sebacate were added to 100 parts by weight of a copolymer of 83 polyvinylidene chloride and 17 strips of vinyl chloride. 25 micron inner layer, and on both sides 6 micron of mixed resin of 50 parts of ethylene-vinyl acetate copolymer resin with vinyl acetate content of 28% and 50 parts of ethylene-acrylic acid copolymer resin with acrylic acid content of 20%. and a 15-micron layer of ethylene-propylene copolymer resin with an ethylene content of 5% and a randomness index of 0.45 on one outer side, and a layer of ethylene-propylene copolymer resin with an intrinsic viscosity of 2 in tetralin at 135°C on the other side. .5
A 300 micron layer of isotactic polypropylene resin was placed and melt extruded from a T-die, passed through a rotating casting roll at 25°C equipped with an air nozzle at a temperature of 20°C, and then heated to 135°C. Stretched to 3.3 times in the machine direction using a group of heated rolls, then stretched to 14
3.3 times laterally in the 5°C heating zone, totaling 10.
It was stretched 9 times and subjected to tension heat treatment at 155°C.

The obtained film has excellent transparency, stiffness, gloss, and scratch resistance, and has an oxygen permeability of 11 (cc) before stretching.
/i ・24hr, 23℃), water vapor transmission rate 1.0 (
? /rtf・24hr), oxygen permeability is 30
(CC, /i・24hr, 23℃), water vapor transmission rate 4.
5 (?/i ・24hr).

In addition, the heat sealing strength of the ethylene-propylene copolymer resin layers is determined at a heating plate temperature of 150°C and a pressure of 1kg/ctyi.
, 0.6 (kg///
15 width).

The thickness of the vinylidene chloride resin layer was measured in the same manner as in Example 1.2, and was found to be extremely well-balanced with an average of 2.3 microns, sigma-o, and i-microns.

As is clear from the above examples, method 1 of the present invention
This has made it possible for the first time to produce a film with a uniform layer of vinylidene chloride resin that is extremely thin, 3 microns or less, and has a high barrier property against gas and moisture.

This is because (1) one layer of specific glue is arranged with a specific thickness on both sides of the vinylidene chloride resin layer, and (2) the total thickness of the surface layers on both sides is greater than that of the vinylidene chloride resin layer. (3) The laminate melt-extruded with the above configuration was pressed against a cooling roll with cooling air directly under the extrusion die; (4) It was heated and stretched at a temperature higher than the softening temperature of the resin on both surfaces. This effect was first brought about by synergizing the four requirements of .

In addition, since the obtained laminated film has an extremely thin layer of vinylidene chloride-based resin, it is competitive with resin film in terms of cost, and when judged by taking into account its gas and moisture barrier properties, It's an extremely ideal film.

Claims (1)

[Claims] 1 Vinylidene chloride resin serves as the center layer, and on both sides there are ethylene-vinyl acetate copolymer resin, copolymer resin of ethylene and unsaturated carboxylic acid or its metal salt, ethylene-unsaturated carboxylic acid ester copolymer resin, and styrene. A resin layer of 5 to 30 microns made of one or a mixture of two or more of butadiene block copolymer resins is laminated, and the total thickness is the same as that of the vinylidene chloride resin layer on the outer surface of the circle. The thermoplastic resin layers selected from thicker polyolefin resins, polystyrene resins, and polyamide resins are melt-extruded into a laminated flat structure, passed between a cooling roll and a cold air nozzle, and then A method for producing a laminated film having an ultra-thin vinylidene chloride resin layer, which comprises stretching at a temperature higher than the softening temperature of both surface resins in a heating zone.