JPS599345B2 - Manufacturing method of laminated packaging material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a laminated packaging material using a thin layer of uniform thickness of a vinylidene chloride copolymer resin as a barrier layer.

Conventionally, a vinylidene chloride resin layer has been used as a barrier layer against gas or water vapor in a laminated film.

However, in general, vinylidene chloride resin has a low viscosity when melted and the drawdown phenomenon during extrusion is severe, so it is extremely difficult to melt and extrude it into a film with a uniform thickness of 3 microns or less due to the design of the extrusion die. It is.

In addition, vinylidene chloride resin, which is much more expensive than other resins due to the complexity of the monomer manufacturing process and polymerization process, is not suitable for polypropylene, polyethylene, etc. 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 water vapor, it is still difficult to compete with relatively inexpensive resin films such as nylon. I could not be accepted by the world. Therefore, although it is recognized that films laminated with this as a barrier layer, such as coextruded laminated films or laminated films, are excellent packaging materials in terms of physical properties, it is extremely difficult to find a place where they can be used. It was hot. For this reason, conventionally, laminated packaging materials sandwiching ultra-thin pinylidene chloride resin layers have been manufactured by a coating method using a vinylidene chloride resin solution or emulsion.
However, this method not only requires a large amount of capital for equipment such as drying equipment and solvent recovery equipment, but also requires high costs in terms of the number of operating personnel, yield, etc., as it is performed in a completely separate process from the film formation process. The drawback was that I couldn't do it. An object of the present invention is to provide a method for forming a vinylidene chloride resin layer into a uniform thin layer in a laminated packaging material having a vinylidene chloride resin layer as an inner layer.

Another object of the present invention is to provide a method for enhancing the gas and moisture barrier properties of a thinned pinylidene chloride resin layer. Still another object of the present invention is to provide a method that allows laminating a surface layer by appropriately selecting a surface layer depending on the application, and making it possible to create a laminated film with a vinylidene chloride resin layer adjusted to the required thickness. That's true.

The ultimate object of the present invention is to provide a method for making a laminate having a layer of vinylidene chloride resin industrially usable. In the present invention, a pinylidene chloride resin layer serves as the center layer, and on both sides, ethylene/vinyl acetate copolymer resin, ethylene and unsaturated carboxylic acid or
(A bonding resin of 5 to 30 microns consisting of one or more mixed resins of copolymer resins with metal salts thereof, ethylene/unsaturated carboxylic acid ester copolymer resins, and styrene/butadiene block copolymer resins) The layers are laminated, and the five outer surfaces of one of the bonded resin layers are coated with polyolefin resin,
A surface resin layer selected from polystyrene resin and polyamide resin is arranged, and the surface resin layer/bonding resin layer/
A laminate having a flat structure of the center layer/bonding resin layer is melt-extruded and immediately passed between a cold air nozzle and a cooling roll 4 to form a laminate film without being stretched. A thermoplastic resin film or melt selected from polyolefin resin, polystyrene resin, and polyamide resin is applied to the outer surface of the bonding resin layer, so that the sum of the thicknesses of both surface resin layers is less than the thickness of the pinylidene chloride resin layer. This is a method for producing a laminated packaging material, which is characterized in that the laminated material is laminated to a thickness that increases in thickness, and the laminated body is stretched uniaxially or biaxially in a heating zone to make the thickness of the vinylidene chloride resin layer 3 microns or less.

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

In addition, ethylene/vinyl acetate copolymer resin placed on both sides, copolymer resin of ethylene and unsaturated carboxylic acid or its metal salt, ethylene/unsaturated carboxylic acid ester copolymer resin, styrene/butadiene block copolymer resin All of the resins are molten and inseparably adhere to vinylidene chloride resins, polyolefin resins, polyamide resins, and polystyrene resins. In the present invention, an ethylene/vinyl acetate copolymer resin, a copolymer resin of ethylene and an unsaturated carboxylic acid or a metal salt thereof,
The ethylene/unsaturated carboxylic acid ester copolymer resins have an ethylene content of 60 to 90%, and the styrene/butadiene block copolymer resins have a styrene content of 30 to 50%.

In the manufacturing method of the present invention, the lamination thickness of this bonding resin layer during extrusion is set in the range of 5 microns to 30 microns.

This limitation of ambiguity is important. If the thickness of the bonding resin layer is less than 5 microns, the adhesion between the center layer and the surface resin layer will not be sufficient, and the center layer will be particularly prone to stretch unevenness during stretching, and will be subject to slight external impact after stretching. In particular, this tends to lead to the disadvantage that peeling is likely to occur. In addition, if the thickness exceeds 30 microns, the pinylidene 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. This results in areas that have lost their central layer. The reason for this is that during forced stretching, the thick surface resin layer actively stretches, and the center layer expands accordingly, but if the adhesion between the center layer and the surface resin layer is not sufficient, the surface resin layer The center layer does not follow the elongation of the material smoothly, and the elongation of the center layer tends to be uneven.Furthermore, even if the adhesion between the center layer and the surface resin layer is sufficient, the bonding resin layer is thick. It is thought that this is because if it is too long, oscillations will occur due to the forced stretching of the surface resin layer, making it difficult for the center layer to be stretched evenly. Another role of these bonding resin layers is to disperse and retain the low-molecular plasticizer exuded from the center layer, which is caused by the increase in the crystalline region during heating and stretching of the laminated film in the subsequent stage, within the bonding resin layer without being stopped at the interface. 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 low-molecular plasticizers with a molecular weight of 500 or less, such as dioctyl sebacate, dibutyl sebacate, acetyl tributyl citrate, and epoxidized vegetable oil, but these plasticizers improve the thermal stability and processability during melt extrusion. On the other hand, it is known that it reduces the gas barrier and moisture barrier properties of vinylidene chloride resins. In addition, these low-molecular plasticizers, which are liquid or fluid at room temperature, have the property of leaching out from inside the vinylidene chloride resin film to the surface over time, especially when it is exposed to heat. . According to the manufacturing method of the present invention, the dependent elongation of the vinylidene chloride resin layer in response to the elongation of the surface resin layer, with the help of the low-molecular plasticizer contained, causes the elongation deformation of the central layer to progress uniformly throughout. Moreover, the thickness of the center layer after stretching is extremely uniform, and a packaging material with high reliability in gas barrier properties and moisture barrier properties can be obtained.

Furthermore, when the phenomenon in which the plasticizer is dispersed and retained in the bonded resin layer due to the heating stretching operation in the present manufacturing method is taken into account, a laminated film with barrier properties far exceeding expectations can be obtained. become. The thermoplastic resin laminated on the outer surface of the bonding resin layer is a polyolefin resin such as a polyethylene resin or a polypropylene resin, a polyamide resin, or a polystyrene resin. Here, polyethylene resin is a copolymer containing 60% or more of ethylene or its ionomer with metal ion crosslinks.
It includes multicomponent polymers and blend polymers. Polypropylene resins and polyamide resins both contain 60% or more of propylene or amide, and polystyrene resins include copolymers, multicomponents, and blended polymers that contain 40% or more of styrene. In the manufacturing method of the present invention, a laminated film is melt-extruded from a nozzle, with one surface coated with a resin forming the surface layer of the packaging material and the other surface remaining as a bonded resin layer. The film is passed between a cooling roll rotating directly below and an air nozzle spraying cold air toward the cooling roll, and is then formed into a non-stretched film.

Here, the laminated film is pressed against a cooling roll by cold air, and this is an essential requirement to prevent the core vinylidene chloride resin layer and the bonding resin layer from becoming loose. As mentioned above, pinylidene chloride resins that have such high fluidity that they draw down when melted and the resins that form the bonding resin layer can be made into a film by simply winding them around cooling rolls or compressing them between cooling rolls. If air is allowed to partially enter between the roll and the film, it will partially bulge, and these highly fluid resins will flow and solidify in response to the distortion, resulting in uneven thickness. This tends to cause cracks 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 by the material and thickness of both surface resin layers, but the temperature is 0 to 30°C, and the air volume and wind pressure are dependent on the roll and film. Any material may be used as long as it can press the film against the roll to an extent that prevents air from entering between the rolls. Moreover, the cold air temperature and the roll surface temperature do not necessarily have to be the same. In this way, it is extremely important to form an unstretched film without one of the surface resin layers.
Later on, it becomes possible to apply a surface resin layer suitable for each application as needed, and since the vinylidene chloride resin layer is in an unstretched state, it can provide the barrier properties and low cost required for each application. It is possible to thin the layer by heating and stretching while maintaining a balance of properties.

On top of the bonding resin layer forming one side of the unstretched film, a film that will become the surface resin layer of the packaging material is laminated, or the resin is laminated while being melt-extruded.

This surface resin layer is selected from the thermoplastic resins described above as the resin group forming the other surface already formed. The films laminated here may be unstretched or may be partially uniaxially or biaxially stretched to the extent that stretching after lamination is possible. However, the surface resin layer to be laminated here must be thick enough that the sum of its thickness and the surface resin layer already formed on the other side is greater than the thickness of the vinylidene chloride resin layer. No. This is an essential requirement in order to actively stretch both surface resin layers during the subsequent stretching, and to stretch the bonding resin layer and vinylidene chloride resin layer dependently on this stretching, and the total thickness of both surface resin layers. If the thickness is less than the thickness of the vinylidene chloride resin layer, the traction to the bonding resin layer and the pinylidene chloride resin layer will be low, and each resin layer will tend to stretch unevenly in parts, making it easy to crack.

Stretching is performed 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 in combination, or uniaxial stretching using either of these methods. It may be. Stretching is carried out in a heating zone.

The temperature inside the oven is set to be equal to or higher than the softening point of the resin on the lower softening point of both surface resin layers. The laminated film heated and stretched in this manner does not shrink at temperatures below the 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, displayed, etc. Next, examples of the present invention will be shown.

Example 1 100 parts (by weight, the same applies hereinafter) of a copolymer resin of 85% vinylidene chloride and 15% vinyl chloride, 2.3 parts of dibutyl sebacate, and 2 parts of acetyltributyl citrate.
, an inner layer of 10 microns made of vinylidene chloride copolymer resin with 0 parts added, and an ethylene content of 75% on both sides.
% ethylene/ethyl acrylate copolymer resin, and Surlyn Al652 on one outer side.
A 400 micron layer with a diameter of 400 microns is arranged and laminated and extruded from a T-die, passed between an air nozzle blowing out air at 20°C and a roll with a surface temperature of 15°C, and the film is left unstretched ( I took it up as AJ.

On the other hand, nylon resin 6 was extruded into a film with a thickness of 200 microns (B), and while the film was laminated on the ethylene ethyl acrylate resin layer of 8, it was heated three times in the longitudinal direction in a heating zone of 90°C. , 3 times horizontally, total 9
It was stretched twice and then subjected to tension heat treatment in a heating zone at 120°C. The obtained film has excellent transparency, oil resistance, and pinhole resistance, and its oxygen permeability is 1/9th that of the unstretched laminated film of film (A) + (B). The unstretched film is 4 (CC/I・24hr, 23
℃), whereas the stretched film has a water vapor transmission rate of 18, or the unstretched film has a water vapor transmission rate of 1.5 (7/d・2
4hI-), it showed an extremely high blocking property of 7.5.

In addition, the Surlyn A layers were placed facing each other, and the heating plate temperature was 150℃.
The adhesive strength of the heat-sealed portion, which was performed at a pressure of 1k9/Crii and a sealing time of 0.5 seconds, was 3.0 (K9/15 mm width).

Also, take the obtained film one by one from a random position.
The thickness of the vinylidene chloride resin layer was measured by cutting out a sheet, randomly selecting 10 measurement points on each sheet, and found that it was extremely uniform with an average of 1.1 microns and a sigma of -0.03 microns. It was hot.

Example 2 A 20 micron inner layer made of a vinylidene chloride copolymer resin prepared by adding 1.5 parts of dioctyl adipate and 2.5 parts of dibutyl sebacate to 100 parts of a copolymer of 83% vinylidene chloride and 17% vinyl chloride. and a 20 micron layer of ethylene/vinyl acetate copolymer resin with a vinyl acetate content of 28% on both sides, and a 20 micron layer of ethylene/vinyl acetate copolymer resin with a vinyl acetate content of 5% and a randomness index of 0.45 on one outer side.
A 150-micron layer of ethylene/propylene random copolymer resin is arranged and laminated and extruded from a T-die, and passed between a nozzle that blows out cold air at 15°C directly below the extrusion nozzle and a cooling roll with a surface temperature of 20°C. The film was then rolled up without being stretched.

This is taken as a film (0. On the other hand, the putadiene content is 6%
Rubber-modified polystyrene resin is extruded from a T-die to a length of 2 m.
It was wound up as an unstretched film.

This is called film (self). Next, the ethylene/pineyl acetate side of the film (O) and the film (D) were heated at 95°C.
The sheets were laminated using thermocompression rolls, and stretched 3 times in the machine direction using a group of heated rolls at 120° C., and then stretched 3 times in the transverse direction in a heating zone at 130° C., for a total of 9 times. The resulting film has firmness, excellent thermoformability, and impact resistance.
Furthermore, compared to the oxygen permeability of 14 (CC/I・24hr, 23°C) and water vapor permeability of 0.9 (7/Rrl・24hr) of the unstretched laminated films of films (C) and (D), a thin layer was added to 1/9. The oxygen permeability of the stretched film is 31 (C
C/M2・24hr, 23℃), water vapor transmission rate 5 (7/
Trl・24hr).

In addition, four pieces of 1 m2 each were cut from the obtained film at random positions, and 10 measurement points were randomly placed on each piece.
The thickness of the vinylidene chloride resin layer was measured at selected locations and found to be extremely uniform with an average of 2.2 microns and a sigma of 0.06 microns. Example 3 A 26 micron inner layer made of a vinylidene chloride copolymer resin prepared by adding 1.5 parts of dioctyl adipate and 2.5 parts of dibutyl sebacate to 100 parts of a copolymer of 83% vinylidene chloride and 17% vinyl chloride. and a 20-micron layer of styrene-butadiene block copolymer resin with a styrene content of 40% on both sides, and an ethylene-propylene random copolymer resin with an ethylene content of 5% and a randomness index of 0.45 on one outer side. A 25 micron layer of resin was arranged and laminated and extruded from a T die, and after passing between an air nozzle blowing out air at 18°C and a rotating roll with a surface temperature of 20°C, it remained unstretched. Film (E
).

On the other hand, a polystyrene resin with an MFL of 2.5 and a specific gravity of 1.05 was extruded into a film with a thickness of 2200 microns (F'
) while laminating it on the remaining styrene-butadiene block copolymer resin layer of the film (g).
The film was stretched 3 times in the longitudinal direction using a heating roll group at 0°C, and then 3 times in the transverse direction in a heating zone at 130°C, for a total of 9 times.

The obtained film was stiff, had excellent thermoformability and transparency, and although it was thinned to 1/9 of the thickness of an unstretched film in which films (G) and (D) were laminated, The oxygen permeability of the unstretched film is 10 (CC/TTI・24h
r, 23°C), while for stretched film it is 25°C.
, and the water vapor permeability of the unstretched film is 1.2 (y
/I・24hI-), it showed an extremely high blocking property of 7. In addition, four pieces of 1 m2 of the obtained film were taken from random positions, and 10 measurement points were randomly selected on each piece, and the thickness of the vinylidene chloride resin layer was measured. The average result was 2.9. micron, sigma
It was extremely uniform with a diameter of 0.06 microns. Example 4 A 9.8 micron film made of a vinylidene chloride copolymer resin prepared by adding 1.5 parts of dioctyl adipate and 2.5 parts of dibutyl sebacate to 100 parts of a copolymer of 83% vinylidene chloride and 17% vinyl chloride. M on the inner layer and on both sides
I4. O, 20 micron layer of ethylene-vinyl acetate resin with 26% vinyl acetate content, and one outer side with 5% ethylene content and 0 randomness index.
．． 45 ethylene propylene random copolymer resin 6
Laminated and extruded from a T-die with a layer of 0 micron, 15
After passing air between the roll and an air nozzle injecting air at a temperature of 0.degree. C. toward the rotating roll, a film (G) was obtained without stretching.

On the other hand, 1.5m77 of polystyrene resin with MFL2.5 and specific gravity 1.05 was made from T-die! Melt extrusion into a thick flat plate (b) Stretch it 2.5 times in the longitudinal direction using a group of heated rolls, then laminate it on the ethylene vinyl acetate resin surface of the film (G) and heat it at 130°C. It was stretched 3.5 times in the transverse direction in the zone.

The obtained film is stiff, has excellent thermoformability and transparency, and has an oxygen permeability of 28 (CC/I・24) of the laminated film in which the longitudinally stretched film is laminated with film (G).
hr, 23℃), water vapor transmission rate 1.5 (7/7TI・2
Oxygen permeability 42, water vapor permeability 3.0 for 4hr)
showed an extremely high value. Further, when the thickness of the pinylidene chloride resin layer was measured in the same manner as in Example 1, it was found to be extremely uniform with an average of 2.8 microns and a sigma of 0.06 microns. As is clear from the above examples, in the manufacturing method of the present invention, the pinylidene chloride resin layer in the laminate is once formed into an intermediate product with a uniform thickness and no stretching, and extrusion film formation is performed. Even in resin processing factories that do not handle vinylidene chloride resin, which is difficult to process, it is now possible to coat it with surface resin and stretch it. It has become possible to easily and quickly produce the required brand type of packaging material according to the product, and its industrial value is extremely high. Because it can exist as a thin layer, it can withstand market competition sufficiently, and it can also provide high and reliable gas and water vapor barrier properties, making it extremely useful as a general-purpose packaging material.

Claims (1)

[Claims] 1. Vinylidene chloride resin layer serves as the center layer, and on both sides thereof, ethylene/vinyl acetate copolymer resin, copolymer resin of ethylene and unsaturated carboxylic acid or its metal salt,
A bonding resin layer of 5 to 30 microns consisting of one or more mixed resins of ethylene/unsaturated carboxylic acid ester copolymer resin and styrene/butadiene block copolymer resin is laminated, and one of the bonding resin layers is further laminated. A laminate with a surface resin layer selected from polyolefin resin, polystyrene resin, and polyamide resin is arranged on the outer surface, and has a flat structure of surface resin layer/bonding resin layer/center layer/bonding resin layer. After melt extrusion, it is immediately passed between a cold air nozzle and a cooling roll to form a laminated film without stretching, and then at any time, polyolefin resin, polystyrene resin, and Films or melts of thermoplastic resins selected from polyamide resins are laminated to a thickness such that the sum of the thicknesses of both surface resin layers is greater than the thickness of the vinylidene chloride resin layer, and the laminate is uniaxially heated in a heating zone. or biaxially stretched,
A method for producing a laminated packaging material, characterized in that the thickness of the vinylidene chloride resin layer is 3 microns or less.