JPS6141289B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a multilayer structure having a saponified ethylene-vinyl acetate copolymer layer with an ethylene content of 15 to 55 mol% and a saponification degree of vinyl acetate component of 90 mol% or more by coextrusion molding. be. A laminated structure consisting of a saponified ethylene-vinyl acetate copolymer (A) layer and another thermoplastic resin (B) layer is A.
Because the layer's excellent oxygen gas barrier properties, fragrance retention, and oil resistance are effectively utilized, it is used in a variety of applications including food packaging, pharmaceuticals, industrial chemicals, fuel oil packaging, and liquid transportation. Useful. The partner resin layer B layer to be combined with layer A can be made of polyolefin resins such as low-medium to high-density polyethylene, polypropylene, polyester, polyamide, polycarbonate, etc., and a multilayer structure can be obtained by coextrusion method. When attempting to do so, there is generally a problem that the interlayer adhesive strength between layer A and layer B is poor. Therefore, a mutual blending method in which resin B is blended into layer A and resin A is blended into layer B, layer A,
Various methods have been proposed, including a resin blending method in which an adhesion-imparting resin is blended into at least one of the B layers, and an adhesive layer interposition method in which an adhesive resin layer having affinity with both layers is interposed between the A and B 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 intensive research in an attempt to improve the interlayer adhesive strength by changing the structure of the molding machine and the molding operation. As a result, the inventors have developed a technology in which the A layer and the B layer are pressed together in a molten state in a die for more than 2.0 seconds. The inventors have discovered that the interlayer adhesive strength can be further enhanced by this method, and have completed the present invention. In general, in coextrusion molding of two or more layers using polyethylene, ionomers, ethylene-vinyl acetate copolymers, polypropylene, polyamides, polyvinyl chloride, etc., each layer is bonded in contact outside the die or in contact within the die. Even when bonded, 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 layer A and layer B to 2 seconds or more as in the present invention is a special condition that is not normally considered in this field. The resin A 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 decreases, and if the ethylene content is less than 55 mol%,
If it exceeds mol%, or if the stenality is less than 90 mol%, the desired oxygen barrier properties will be insufficient, and no improvement in interlayer adhesion strength will be observed even if the contact time of both layers in the die is increased. . 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) α 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 resin B other than A includes low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, saponified ethylene-vinyl acetate copolymer having a composition other than A,
Ionomer, ethylene-α-olefin (α-olefin with 3 to 20 carbon atoms) copolymer, ethylene-propylene-diene copolymer, ethylene-acrylic acid ester copolymer, polypropylene, propylene-ethylene copolymer, propylene - α-olefin (α-olefin with 4 to 20 carbon atoms) copolymer, single or copolymer of olefin such as polybutene, polypentene, or those obtained by graft modification of these polyolefins with unsaturated carboxylic acid or its ester, etc. in a broad sense These polyolefin resins may be used alone or in a blend of two or more thereof. In addition, polyester, polyamide, copolyamide, polycarbonate, polyvinyl chloride, polyvinylidene chloride, acrylic resin, styrene resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, etc. can also be used. The structure of the multilayer film obtained by the method of the present invention is not limited to the A/B two-layer structure. B/A/B,
A/B/A, A/B ₁ /B ₂ , B ₂ /B ₁ /A/B ₁ /
Any configuration including B ₂ , B/A/B/A/B and at least one layer each of A layer and B layer is possible. In each of the above embodiments, B ₁ is A
A preferred embodiment is an adhesive resin layer that adheres to _B2 . In such a layer configuration, an appropriate amount of adhesion-imparting resin may be blended into at least one of the A layer or the B 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 60 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 polymers or copolymers of ethylene or propylene, polyamides, polyester elastomers, polyurethane elastomers, and the like. In addition, efforts have been made to increase the interlayer adhesion by blending layer B with layer A or blending layer A with layer B. Molding loss of the laminated film obtained in the present invention may be crushed and mixed with new B resin for use, but in such a case, the B layer inevitably becomes a blend layer. Now, resin A and resin B are supplied to a multilayer coextrusion molding machine and melt-extruded by an in-die bonding method to obtain a multilayer structure. Molding methods include T-die extrusion, blow molding, fiber or monofilament extrusion, irregular die extrusion, pipe extrusion, and even coating a base material with a melt coextruded from a T-die. Extrusion coating methods can also be employed. However, since the multilayer inflation molding method has slightly different conditions, a separate patent application has been filed, and it is excluded from the scope of the present invention. During molding, it is important to select conditions such that layer A and layer B are in pressure contact with each other in a molten state for 2.0 seconds or more in 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 can be satisfied by increasing the land length or decreasing the discharge amount. If the residence time in the land is less than 2.0 seconds, not only the interlayer adhesion between layer A and layer B will be insufficient;
This results in disadvantages such as a decrease in heat sealing strength and a decrease in oxygen gas barrier properties due to an increase in thickness unevenness of the A layer. There is no particular limit to 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 the condition is usually set to 15 seconds at most. There are many things. A particularly preferred range is 2.0 to 5.0 seconds. Note that the method of installing a guide outside the die, heating the guide, and guiding the flow of molten resin to this guide for bonding results in a loss of resin pressure, and in addition, resin leaks from the joint. The pressure could not be increased sufficiently, and therefore only a slight improvement in adhesive strength was observed. The multilayer structure after film formation can be subjected to heat treatment, cooling treatment, uniaxial stretching treatment, biaxial stretching treatment, printing treatment, etc. The multilayer structure with or without such treatment can also be dry laminated with other substrates, such as paper, aluminum foil, plastic film, or can be laminated with any resin with or without adhesive. may be melt coated, solution coated or dispersion coated. Products are often reprocessed into bags, deep squeeze containers, boxes, tubes, etc. The multilayered structure obtained by the method of the present invention or its processed products can be used for foods (including beverages, seasonings, dairy products, etc.), pharmaceuticals, chemicals, aroma-containing substances, luxury goods, concentrated medicines, microorganisms, and precision equipment parts. It can be applied to a wide range of fields, including packaging for electrical and electronic equipment parts, as well as separation membranes and agricultural films. Next, the method of the present invention will be further explained with reference to Examples. Example 1 Coextrusion molding was carried out using a T-die under the following conditions. Raw material resin Saponified ethylene-vinyl acetate copolymer with ethylene content of 29.5 mol% and degree of saponification of vinyl acetate component of 99.0 mol% B ₁ modified polyethylene resin (Admar LF-500 manufactured by Mitsui Petrochemical Industries, Ltd.) B ₁ : Melt Molding conditions for low density polyethylene with index 1.8 and density 0.929 Extruder: For layer A: 40 mm diameter extruder L/D = 24, compression ratio 3.5 For B ₁ layer: 40 mm diameter extruder L/D = 24, compression ratio 3.35 B For ₂ layers: 65mm diameter extruder L/D=28, compression ratio 3.5 Die: Set width 1100mm, clearance 0.8mm
T-die for three-layer coextrusion Land length (distance from the confluence point to the die lip): 50mm Land volume (volume of the flow path from the confluence point to the die lip): 68cm ^3Extrusion temperature: Cylinder tip A: 220℃, _B1 : 210℃, _B2 : 210
℃ Dice: 210℃ Cooling roll temperature: 80℃ Discharge amount: 86.2Kg/H (A: 18.3Kg/hr, B ₁ : 9.9
Kg/hr, B ₂ : 58.0Kg/hr) Residence time in land: 2.7 seconds Take-up speed: 18.8 m/min Film thickness after take-up: 84.8μ (A: Upper layer 15.2μ, B ₂ :
(Middle layer 10.1μ, _B2 lower layer 59.5μ) Product winding width: 880mm Control example 1 Molding conditions Die: Land length: 30.5mm Land volume: 39.5cm ³ Discharge rate: 91.9Kg/hr (A: 19.2Kg/hr , _B1 :
10.4Kg/hr, B ₂ : 62.3Kg/hr) Residence time in land: 1.5 seconds Take-up speed: 19.4m/min. Coextrusion molding was carried out using a T-die under the same conditions as in Example 1. . The film thickness after collection is
87.7μ (A: Upper layer 15.5μ, B ₁ : Middle layer 10.3μ,
B ₂ :lower layer 61.9μ). Example 2 As resin B ₁ in Example 1, a 1:1 mixture by weight of the modified polyethylene resin used in Example 1 and ethylene-hinyl acetate copolymer resin (Yukalon Eva EVA30K manufactured by Mitsubishi Yuka Co., Ltd.) was used. ,
Molding conditions: Discharge rate: 86.9Kg/hr (A: 18.3Kg/hr, B ₁ :
Coextrusion molding using a T-die was carried out under the same conditions as in Example 1, except that 10.6 Kg/hr, B ₂ : 58.0 Kg/hr) was adopted. The film thickness after collection is
85.5μ (A: upper layer 15.2μ, B ₁ : middle layer 10.8μ,
B ₂ :lower layer 59.5μ). Control example 2 Molding conditions: Die: Land length: 30.5 mm Land volume: 39.5 cm ³ Discharge rate: 93.9 Kg/hr (A: 19.2 Kg/hr, B ₁ :
11.3Kg/hr, B ₂ : 63.4Kg/hr) Residence time in land: 1.5 seconds Take-up speed: 19.4m/min Co-extrusion molding was carried out using a T-die under the same conditions as in Example 2, except that . The film thickness after collection is
89.7μ (A: Upper layer 15.5μ, B ₁ : Middle layer 11.2μ,
B ₂ :lower layer 63.0μ). Example 3 As resin B ₁ in Example 1, ethylene-
Using α-olefin copolymer (Tafmer P-0480 manufactured by Mitsui Petrochemical Industries, Ltd.), resin A and
B ₂ was the same as in Example 1, and coextrusion molding was performed using a T-die under the following conditions. Extruder: For A layer: 60mm diameter extruder L/D = 28, compression ratio 3.2 B For ₁ layer: 60mm diameter extruder L/D = 28, compression ratio 3.0 B For ₂ layers: 90mm diameter extruder L/D =28, compression ratio 3.5 Die: set width 1200mm, clearance 1.2mm
T-die for 3-layer coextrusion Land length: 175mm Land volume: 211cm ³ Extrusion temperature: Cylinder tip A: 210℃, B ₁ : 190℃, B ₂ : 200
℃ Dice: 205℃ Cooling roll temperature: 40℃ Discharge amount: 296.72Kg/hr (A: 80.0Kg/hr, B ₁ :
54.7Kg/hr, B ₂ : 162Kg/hr) Residence time in land: 2.5 seconds Take-up speed: 120 m/min Film thickness after take-up: 44.4μ (A: upper layer 10.2μ, B ₁ :
(Middle layer 8.7μ, _B2 : Lower layer 25.5μ) Product winding width: 900mm Control example 3 Molding conditions: Die: Land length: 33.5mm Land volume: 95cm ³ Discharge rate: 304.7Kg/hr (A: 81.5Kg/hr , _B1 :
56.2Kg/hr, _B2 : 167Kg/hr) Coextrusion molding using a T-die was carried out under the same conditions as in Example 3, except that residence time in land: 1.1 seconds and withdrawal speed: 120 m/min were used. The film thickness after collection is
45.6μ (A: Upper layer 10.4μ, B ₁ : Middle layer 8.9μ,
B ₂ :lower layer 26.3μ). Example 4 High-density polyethylene with a melt index of 0.7 and a density of 0.952 was used as resin B ₁ in Example 1, and the molding conditions were as follows: Discharge rate: 76.7 Kg/hr (A: 18.3 Kg/hr, B ₁ : 9.9
(Kg/hr, B ₂ : 48.5 Kg/hr) Coextrusion molding was carried out using a T-die under the same conditions as in Example 1, except that the residence time in the land was 3.2 seconds. The film thickness after collection is
73.9μ (A: upper layer 15.2μ, B ₁ : middle layer 10.1μ,
B ₂ :lower layer 48.6μ). Control example 4 Molding conditions: Die: Land length: 30.5 mm Land volume: 35.5 cm ³ Discharge rate: 80.8 Kg/hr (A: 19.2 Kg/hr, B ₁ :
10.4Kg/hr, _B2 : 51.2Kg/hr) Residence time in land: 1.8 seconds Take-up speed: 19.4m/min Co-extrusion molding was carried out using a T-die under the same conditions as in Example 4, except that . The film thickness after collection is
75.5μ (A: upper layer 15.5μ, B ₁ : middle layer 10.3μ,
B ₂ :lower layer 49.7μ). The results of Examples 1 to 4 and Control Examples 1 to 4 are summarized above.
Shown below.

[Table] Example 5 Blow molding of B/A/B configuration was performed under the following conditions. Raw material resin A: Saponified ethylene-vinyl acetate copolymer with ethylene content of 29.5 mol% and saponification degree of vinyl acetate component of 99.0 mol% B: Modified polyethylene resin (Admer LF-500 manufactured by Mitsui Petrochemical Industries, Ltd.) Molding conditions Extruder: For A: 30 mm diameter extruder For B: 55 mm diameter extruder Screw: Both L/D = 24, compression ratio 3.2 Die: Three-layer spider type die, core diameter 25
mm Land length: 55mm Land melting capacity: 34cm ³ Extrusion temperature: Cylinder tip A: 210℃, B: 200℃ Die: 190℃ Discharge rate: 46.9Kg/hr (A: 4.9Kg/hr, B: 42.0
Kg/hr) Residence time in land: 2.5 seconds Volume thickness: 370μ (B: inner layer and outer layer each 170μ,
A: Intermediate layer 30μ) Container capacity: 300c.c. Control example 5 Molding conditions: Die: Land length: 22mm Land volume: 13.8cm ³ Discharge rate: 47.0Kg/hr (A: 5.0Kg/hr, B: 42.0
Kg/hr) Blow molding was carried out under the same conditions as in Example 5, except that the residence time in the land was 1.0 seconds. Example 6 As the resin A of Example 5, a saponified ethylene-hinyl acetate copolymer with an ethylene content of 38.5 mol% and a saponification degree of vinyl acetate component of 98.5 mol% was used, and the molding conditions were: die: land length: 80 mm land. Volume: 49cm ³ Discharge amount: 48.0Kg/hr (A: 6.0Kg/hr, B: 42.0
Kg/hr) B/A/
B-configuration hollow molding, container thickness 420μ
(B: inner layer 200μ, outer layer 177μ, A: middle layer 43μ),
A container with a capacity of 300 c.c. was obtained. Control example 6 Molding conditions: Die: Land length: 34mm Land volume: 21.6cm ^3Discharge rate: 46.0Kg/hr (A: 6.0Kg/hr, B: 40.0
Kg/hr) Blow molding was carried out under the same conditions as in Example 6, except that the residence time in the land was 1.6 seconds. The results of Examples 5 and 6 and Control Examples 5 and 6 are summarized in the second section.
Shown in the table.

【table】

[Table] Example 7 Resin A was a saponified ethylene-vinyl acetate copolymer with an ethylene content of 42.0 mol% and a degree of saponification of the vinyl acetate component of 99.2 mol%, and a modified polypropylene (Admer QF manufactured by Mitsui Petrochemical Industries, Ltd.).
500) in a ratio of 85:15 by weight,
As resin B, melt index is 0.5 and density is 0.90.
Extrusion temperature: Cylinder tip A: 210℃, B: 230℃ Die: 220℃ Die: Land length 52mm Land volume 32cm ^3Discharge rate: 48.0Kg/hr (A: 3.0Kg/ hr, B: 45.0
Kg/hr) Blow molding was carried out in the same manner as in Example 5 except that the retention time in the land was 2.2 seconds, and the container thickness was 350μ (B: inner layer 150μ, outer layer
A container with a capacity of 300 c.c. was obtained. Control example 7 Molding conditions: Die: Land length: 22mm Land volume: 13.8cm ^3Discharge rate: 49.5Kg/hr (A: 3.0Kg/hr, B: 46.5
Kg/hr) Blow molding was carried out under the same conditions as in Example 5, except that the residence time in the land was 0.9 seconds. The results were as follows: The interlayer peel strength of Example 7 was 620 g/15 mm, and that of Control Example 7 was 210 g/15 mm. As described above, in coextrusion molding using the saponified ethylene-vinyl acetate copolymer (A) as a single layer, the method of the present invention provides a remarkable effect by increasing the residence time in the land. On the other hand, in multilayer coextrusion molding that does not have a saponified ethylene-vinyl acetate copolymer layer,
Generally, the residence time in the land is shortened to about 1 second or less, or an outside-die bonding method is used, but in such cases, increasing the residence time in the land will only reduce productivity. No improvement in interlayer adhesion strength was observed. For example, in the case of multilayer extrusion molding consisting of a saponified ethylene-vinyl acetate copolymer (A) layer and a polyolefin resin (B) layer, the retention time in the land of 1 second and 4 seconds is different from the interlayer adhesive strength of the former. The latter increases by about 2 to 10 times, but in layer configurations such as polyethylene/ethylene-vinyl acetate copolymer, polyethylene/polypropylene, and polyethylene/ionomer, the residence time in the land is 1 second and 4
The interlayer adhesion strength hardly increases when the time is 2 seconds.

Claims (1)

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