JPS6157177B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a multilayer film having a saponified ethylene-vinyl acetate copolymer layer with an ethylene content of 15 to 55 mol% and a degree of saponification of the vinyl acetate component of 90 mol% or more by a co-inflation molding method. It is. A laminated film consisting of an ethylene-vinyl acetate copolymer Ken compound (X) layer and another thermoplastic resin (Y) layer effectively takes advantage of the X layer's excellent oxygen barrier properties, fragrance retention, and oil resistance. In order to
It is useful for a variety of uses including food packaging, pharmaceuticals, industrial chemicals, fuel oil, etc. The partner resin layer Y layer to be combined with the X layer is low.
Examples include medium/high density polyethylene, polypropylene, polyolefin resins including ethylene-vinyl acetate copolymer, polyester, polyamide, polycarbonate, etc., but when trying to obtain a multilayer film by the co-inflation method. Generally, there is a drawback that the interlayer adhesive strength between the X layer and the Y layer is poor. Therefore, a mutual blending method in which resin Y is blended into the X layer and resin X is blended into the Y layer,
Various methods have been proposed, including a resin blending method in which an adhesion-imparting resin is blended into at least one of the Y layers, and an adhesive layer interposition method in which an adhesive resin layer having affinity with both layers is interposed between the X and Y layers. However, there is a strong desire in this industry to further increase the interlayer adhesive strength. The inventors of the present invention have conducted extensive research in an attempt to improve the interlayer adhesive strength by changing the structure of the molding machine and the molding operation, and as a result, they have found that the X layer and the Y layer are brought into contact with each other in a molten state for more than 2.0 seconds in the die. The present inventors have discovered that it is possible to further increase the interlayer adhesive strength using technology, and have completed the present invention. In general, in co-inflation molding of two or three or more layers using polyethylene, ionomers, ethylene-vinyl acetate copolymers, polypropylene, polyamides, polyvinyl chloride, etc., each layer is contact-bonded outside the die or inside the die. Even when contact bonding is performed, the contact time is usually extremely short (usually within 1 second). It can be said that increasing the in-die contact time in the molten state of the X layer and the Y layer to 2.0 seconds or more as in the present invention is a special condition that is not normally considered in this field. The resin X in the present invention has an ethylene content of 15
~55 mol%, degree of saponification of vinyl acetate component 90 mol%
A saponified ethylene-vinyl acetate copolymer having the above composition is used. If the ethylene content is less than 15 mol%, melt moldability will decrease, and the ethylene content will decrease.
If it exceeds 55 mol% or if the degree of saponification is less than 90 mol%, the desired oxygen barrier properties will not be achieved, and even if the contact time between both layers in the die is increased, the interlayer adhesion strength will not improve. do not have. In addition to ethylene and vinyl acetate (or saponified vinyl alcohol), the saponified ethylene-vinyl acetate copolymer may also contain unsaturated carboxylic acids or esters or salts thereof, unsaturated sulfonic acids or salts thereof, (meth) A such as acrylamide, (meth)acrylonitrile, propylene, butene, α-octene, α-octadecene, etc.
- It may contain a small amount of about 10 mol% or less of a third component such as olefin or vinyl ester other than vinyl acetate. Thermoplastic resins other than X include low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, saponified ethylene-vinyl acetate copolymer having a composition other than X, ionomer, ethylene-α- Olefin (α-olefin with 3 to 20 carbon atoms) copolymer, ethylene-
Acrylic ester copolymer, polypropylene,
Propylene-ethylene copolymer, propylene-α
-Olefin (α-olefin with 4 to 20 carbon atoms)
Copolymers, single or copolymers of olefins such as polybutene and polypentene, or polyolefin resins in a broad sense such as those obtained by graft-modifying these polyolefins with unsaturated carboxylic acids or esters thereof, singly or as a blend of two or more types. used. In addition, polyester, polyamide, copolyamide, polycarbonate, polyvinyl chloride, polyvinylidene chloride, acrylic resin, styrene resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, chlorinated polyolefin, etc. can also be used. The structure of the multilayer film obtained by the method of the present invention is not limited to the X/Y two-layer structure, but also Y/X/Y,
X/Y/X, X/Y ₁ /Y ₂ , Y ₂ /Y ₁ /X/Y ₁ /
Any configuration including Y ₂ , Y/X/Y/X/Y and at least one X layer and one Y layer is possible. In each of the above embodiments, Y ₁ is
A preferred embodiment is an adhesive resin layer that adheres to _Y2 . In such a layer configuration, an appropriate amount of an adhesion-imparting resin may be blended with the resin constituting at least one of the X layer or the Y layer. The adhesive resin layer or the adhesion-imparting resin is often one or a blend of two or more of the following resins. For example, low-density polyethylene, medium-density polyethylene, ethylene-vinyl acetate copolymer, partially saponified ethylene-vinyl acetate copolymer with an ethylene content of about 70 mol% or more, ionomer, ethylene-acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, These include α-olefin (α-olefin having 3 to 20 carbon atoms) copolymers, carboxylic acid or carboxylic acid ester graft modified products of ethylene or propylene polymers or copolymers, polyamides, polyester elastomers, polyurethane elastomers, and the like. Also, efforts have been made to increase interlayer adhesion by blending Y into the X layer or blending X into the Y layer. Molding loss from the laminated film obtained in the present invention may be crushed and mixed with new Y resin for use, but in such a case, the Y layer inevitably becomes a blend layer. Now, resin X and resin Y are supplied to a multilayer inflation molding machine, and after being melt-extruded by an in-die joining method, they are expanded into a tube shape and taken off by a nip roll. At this time, it is important to select conditions such that the X layer and the Y layer are in contact with each other in a molten state for at least 2.0 seconds within the die. In order to satisfy this condition, the volume and discharge amount of the so-called land from the confluence point of both melted resins in the die to the discharge port must be appropriately selected. Generally, the condition of residence time in the land of 2.0 seconds or more is satisfied by increasing the land length and decreasing the discharge amount. If the residence time in the land is less than 2.0 seconds, not only the interlayer adhesion between the X layer and the Y layer will be insufficient;
There is a drawback that the thickness variation of each layer becomes large. There is no particular restriction on the residence time in the land as long as it is 2.0 seconds or more, but if it becomes too long, productivity will decrease, so there are naturally restrictions in that respect, and usually the conditions are selected to be no longer than 10 seconds. There are many things. A particularly preferred range is 2.2 to 5 seconds. The multilayer film after film formation can be subjected to heat treatment, cooling treatment, uniaxial stretching treatment, biaxial stretching treatment, printing, etc. The multilayer film with or without such treatment can also be dry laminated with other substrates such as paper, aluminum foil, plastic film, or can be melted with any resin with or without adhesive. coating, solution coating or dispersion coating. The product film is used in bags, deep squeeze containers,
It is often reprocessed into boxes, tubes, etc. The multilayer film obtained by the method of the present invention or its processed products can be used in foods (including beverages, seasonings, dairy products, etc.), pharmaceuticals, chemicals, aroma-containing substances, luxury goods, agricultural chemicals, microorganisms, precision equipment parts, and electrical appliances. In addition to packaging electronic equipment parts, it can be applied to a wide range of fields such as separation membranes and agricultural chemicals films. Next, the method of the present invention will be further explained with reference to Examples. Example 1 Co-inflation molding was performed under the following conditions. Raw _material resin Mixed resin of 2:1 by weight with ethylene-vinyl acetate copolymer (Evaflex P-1405 manufactured by Mitsui Polychemical Co., Ltd.) Y ₂ : Low density polyethylene with melt index 1.8 and density 0.927 Molding conditions Extruder for X 40 mm Diameter extruder, screw L/D = 24, compression ratio 3.35 For Y ₁ 40mm diameter extruder, screw L/D
=24, compression ratio 3.5 Y ₂ 65mm diameter extruder, screw L/D
= 28, compression ratio 3.5 Three-layer co-inflation spiral die with lip diameter 200 mm and lip width 1.0 mm Extrusion temperature Cylinder tip X: 220℃, Y ₁ : 210℃, Y ₂ : 210℃ Die 210 ℃ Land length (distance from the confluence point to the die lip) 70mm Land volume (volume of the flow path from the confluence point to the die lip) 43.8cm ^3Discharge rate 52.7Kg/hr (X: 12.4Kg/hr, Y ₁ : 6.7
Kg/hr, Y ₂ : 33.6Kg/hr) Residence time in land 2.9 seconds Blown air temperature Room temperature Take-up speed 11m/mm Bubble cooling Air at 20℃ is supplied from the air ring to the bubble surface at a height of 50mm and 300mm from the die. Spraying Film thickness after taking off 75μ (X: inner layer 15μ, Y ₁ : intermediate layer 10μ, Y ₂ : outer layer 50μ) Folding width 550mm Control example 1 Molding conditions Land length 25mm Land volume 15.6cm ^3Discharge rate 60.5Kg/hr ( X: 14.3Kg/hr, Y ₁ :
Co-inflation molding was carried out in the same manner as in Example ₁ , except that the retention time in the land was 0.9 seconds and the take-up speed was 12.6 m/min. Example 2 Modified polypropylene (Admer manufactured by Mitsui Petrochemical Industries, Ltd.) was used as resin Y ₁ in Example 1.
QF-300) and ethylene-vinyl acetate copolymer (Evafix P- manufactured by Mitsui Polychemical Co., Ltd.)
1405) and the molding conditions were as follows: Extrusion temperature Cylinder tip X: 230℃, Y ₁ : 230℃, Y ₂ : 230℃ Die 220℃ Land length 70mm Land volume 43.8cm ³ Output 58.7Kg/hr (X: 13.8Kg/hr, Y ₁ :
Co-inflation molding was carried out in the same manner as in Example ₁ , except that the residence time in the land was 2.6 seconds and the take-up speed was 12.2 m/min. Control example 2 Molding conditions: Land length 25mm Land volume 15.6cm ^3Discharge rate 68.2Kg/hr (X: 16.1Kg/hr, Y ₁ :
Co-inflation molding was carried out in the same manner as in Example ₂ , except that the residence time in the land was 0.8 seconds and the take-up speed was 14.2 m/min. Example 3 As resin _Y1 in Example 1, ethylene-
Using α-olefin copolymer (Tafmar-P-0180 manufactured by Mitsui Petrochemical Industries, Ltd.), the molding conditions were: land length 70mm land volume 43.8cm ³ discharge rate 56.7Kg/hr (X: 13.4Kg/hr, Y ₁ :
Co-inflation molding was carried out in accordance with Example ₁ , except that the residence time in the land was 2.7 seconds and the take-up speed was 11.8 m/min. Control example 3 Molding conditions: Land length 25mm Land volume 15.6cm ^3Discharge rate 68.8Kg/hr (X: 16.1Kg/hr, Y ₁ :
(9.3Kg/hr, _Y2 : 43.4Kg/hr) Co-inflation molding was performed in the same manner as in Example 3, except that the residence time in the land was 0.8 seconds. Example 4 High-density polyethylene with a melt index of 0.7 and a density of 0.950 was used as resin Y ₂ in Example 1, and co-inflation was carried out in the same manner as in Example 1 except that the extrusion temperature of Y ₂ was 220°C at the cylinder tip. Shion molding was performed. Control example 4 Molding conditions: Land length 25mm Land volume 15.6cm ^3Discharge rate 61.0Kg/hr (X: 14.3Kg/hr, Y ₁ :
(8.2 Kg/hr, _Y2 : 38.5 Kg/hr) Co-inflation molding was performed in the same manner as in Example 4, except that the residence time in the land was 0.9 seconds. The results of Examples 1 to 4 and Control Examples 1 to 4 above are summarized as
Shown in the table.

[Table] Example 5 Co-inflation molding was performed under the following conditions. Raw material resin X: Ethylene with 42 mol% ethylene content and 98.5 mol% vinyl acetate saponification
Saponified vinyl acetate copolymer Y: Modified ethylene-vinyl acetate copolymer (Admar-VF-500 manufactured by Mitsui Petrochemical Industries, Ltd.) Molding conditions Extruder For X 40 mm diameter extruder For Y 65 mm diameter extruder Screw Both L /D=24, compression ratio 3.3 Die Spiral die with lip diameter 150mm, lip width 1.0mm Extrusion temperature Cylinder tip, X: 210℃, Y: 200℃ Die 210℃ Land length 70mm Land volume 32.8cm ^3Discharge amount 47.4Kg /hr (X: 18.1Kg/hr, Y:
29.3Kg/hr) Residence time in land 2.5 seconds Blow air temperature Room temperature Blow ratio 1.91 Take-up speed 14.5 m/min Bubble cooling Air at room temperature is blown from an air ring onto the bubble surface at a height of 150 mm and 400 mm from the die After take-up Film thickness 60μ (X: inner layer 20μ, Y: outer layer 40μ
μ) Folding width 450mm Control example 5 Molding conditions Land length 30mm Land volume 14.1cm ^3Discharge rate 34.0Kg/hr (X: 13.0Kg/hr, Y:
Co-inflation molding was carried out in the same manner as in Example 5, except that the residence time in the land was 1.5 seconds and the take-up speed was 10.4 m/min. Example 6 As the resin Y of Example 4, modified polyethylene (Admer-LF manufactured by Mitsui Petrochemical Industries, Ltd.) was used.
300) and modified ethylene-vinyl acetate copolymer (DUMILAN G-251 manufactured by Mitsui Polychemical Co., Ltd.)
Using a 1:1 ^mixed resin with a weight of
Co-inflation molding was carried out in the same manner as in Example 5, except that the residence time in the land was 3.2 seconds and the take-up speed was 11.4 m/min. Control example 6 Molding conditions Land length 30mm Land volume 14.1cm ^3Discharge rate 30.0Kg/hr (X: 11.4Kg/hr, Y:
Co-inflation molding was carried out in the same manner as in Example 6, except that the residence time in the land was 1.7 seconds and the take-up speed was 9.2 m/min. The results of Examples 5 and 6 and Control Examples 5 and 6 are summarized in the second
Shown in the table.

[Table] Measured values when running.
Example 7 As the resin G-251) mixed resin at a ratio of 9:1 by weight,
As resin Y, melt index 1.8, density 0.926
low-density polyethylene was used, and the molding conditions were as follows: Land length 70mm Land volume 32.8cm ^3Discharge rate 49.5Kg/hr (X: 18.9Kg/hr, Y:
(30.6Kg/hr) Co-inflation molding was carried out in the same manner as in Example 5, except that the residence time in the land was 2.4 seconds. Control example 7 Molding conditions: Land length 30mm Land volume 14.1cm ^3Discharge rate 39.1Kg/hr (X: 14.9Kg/hr, Y:
(24.2 Kg/hr) Co-inflation molding was performed in the same manner as in Example 7 except that the residence time in the land was 1.3 seconds. The results were that Example 7 had an interlayer peel strength of 890 g/15 mm; heat seal strength was 4.1 Kg/15 mm; and Control Example 7 had an interlayer peel strength of 130 g/15 mm; and a heat seal strength of 0.6 Kg/15 mm. Note that the heat seal strength is a measured value when Y pieces are heat sealed. As described above, the method of the present invention allows ethylene-
In co-inflation molding using saponified vinyl acetate copolymer (X) as one layer, significant effects can be achieved by lengthening the residence time in the land. On the other hand, in multilayer inflation molding that does not have a saponified ethylene-vinyl acetate copolymer layer, the residence time in the land is generally shortened to about 1 second or less, or an outside-die bonding method is usually used. However, in such a case, increasing the residence time in the land only lowers the productivity and does not improve the interlayer adhesive strength. For example, in the case of multilayer inflation molding consisting of a saponified ethylene-vinyl acetate copolymer (X) layer and a polyolefin resin (Y) layer having polar groups, the residence time in the land is 0.8 to 0.9 seconds and 2.6 to 2.9 seconds. However, in layer configurations such as polyethylene/ethylene-vinyl acetate copolymer, polyethylene/polypropylene, polyethylene/ionomer, etc., the residence time in the land is Between 1 second and 4 seconds, the interlayer adhesive strength hardly increases.

Claims (1)

[Scope of Claims] 1. A saponified ethylene-vinyl acetate copolymer (X) layer with an ethylene content of 15 to 55 mol% and a degree of saponification of the vinyl acetate component of 90 mol% or more, and a thermoplastic resin other than X (Y). When manufacturing a multilayer film by co-inflation molding the layers using an in-die bonding method, the X layer and the Y layer are melted in a die.
A method for producing a multilayer inflation film characterized by crimping for 2.0 seconds or more. 2. The method according to claim 1, wherein Y is a polyolefin resin.