JPS6210256B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for coextruding a saponified ethylene-vinyl acetate copolymer and a thermoplastic resin other than the saponified copolymer. Saponified ethylene-vinyl acetate copolymer has strong adhesion to metal in the molten state, so the flow of the resin at the point where it comes into contact with the machine wall during melt molding is poor, and the screw torque increases and becomes stable during long-run molding. There is a problem that continuous rotation is no longer possible. Therefore, in order to solve this problem, it has conventionally been done to blend a small amount of a metal stearate, propylene bisamide, etc. as a lubricant into a saponified ethylene-vinyl acetate copolymer and then subject it to melt molding. However, when coextruding a saponified ethylene-vinyl acetate copolymer with a thermoplastic resin other than the saponified copolymer, if conventionally used lubricants such as metal stearate and propylene bisamide are added, both A problem arises in that the adhesion between the layers is significantly reduced, causing delamination. Furthermore, during molding, these lubricants may thermally decompose, causing coloring or an unpleasant odor. Moreover, in Japanese Patent Application Laid-Open No. 52-77160, ethylene-
Add 1 part of an olefin polymer with a melting point of 60 to 140℃ to 80 to 99 parts by weight of vinyl alcohol copolymer for plasticity.
It is disclosed that adding ~20 parts by weight improves molding processability while maintaining gas permeability resistance. Specifically, gelation load, Experimental results are shown when measuring equilibrium load and melt viscosity. According to the description in JP-A-52-77160, a saponified ethylene-vinyl acetate copolymer with a melting point of 60 to
When 1 to 20% by weight of an olefinic polymer at 140°C is added and the saponified copolymer is melt-molded,
There is no risk of coloring or odor caused by thermal decomposition, but
When this technique is applied to coextrusion molding of the saponified copolymer and other thermoplastic resin, there is a problem that the adhesive force between both layers decreases, causing delamination. The present invention was made to solve the problems that occur when conventionally used lubricants or plasticizers are applied to coextrusion molding as described above. The method for producing a coextrusion product of the present invention involves combining a saponified ethylene-vinyl acetate copolymer (A) with an ethylene content of 15 to 55 mol% and a degree of saponification of the vinyl acetate component of 90 mol% or more; Thermoplastic resins other than compounds (A)
In coextrusion molding with (B), the ethylene-
Low molecular weight polyolefin with a molecular weight of 500 to 10,000 per 100 parts by weight of saponified vinyl acetate copolymer (A)
It is characterized in that 0.01 to 0.5 parts by weight is blended and molded. If coextrusion molding is carried out by the method of the present invention, not only will there be no molding troubles, but also a coextrusion molded product with excellent interlayer adhesion can be obtained, so this coextrusion molded product can be used for secondary processing. Even when this is filled with food and distributed, it does not cause delamination or bag breakage, and is highly reliable. The present invention will be explained in detail below. The saponified ethylene-vinyl acetate copolymer (A) used in the present invention includes those having an ethylene content of 15 to 55 mol% and a degree of saponification of the vinyl acetate component of 90 mol% or more. If the ethylene content is less than 15 mol%, melt moldability will decrease, and if the ethylene content exceeds 55 mol%, it will become close to polyethylene, resulting in poor oxygen barrier properties, as well as poor heat deformability and oil resistance. Not suitable for purpose. In addition, if the degree of saponification of the vinyl acetate component is less than 90 mol%, the thermal stability will be poor, the oxygen barrier property will be poor, and the mechanical properties, heat deformability, water resistance, and oil resistance will not be sufficient. Poor practicality. The saponified ethylene-vinyl acetate copolymer (A) contains, in addition to ethylene and vinyl acetate (or vinyl alcohol obtained by saponifying it), an unsaturated carboxylic acid or its ester or salt, an unsaturated sulfonic acid or its α-salts, (meth)acrylamide, (meth)acrylonitrile, propylene, butene, α-octene, α-octadecene, etc.
- It may contain about 10 mol% or less of a third component such as olefin and vinyl ester other than vinyl acetate. Next, as the low molecular weight polyolefin having a molecular weight of 500 to 10,000, low molecular weight polyethylene or low molecular weight polypropylene is used. Derivatives of these (copolymer modified products, graft modified products, etc.) can also be used in the same manner. Materials having such molecular weights do not fall into the category of plastics, nor do they have extremely low molecular weights, but are in the intermediate range, and can be said to be waxes in a broad sense. The form is a white powder. The softening point is approximately 95 to 115°C for low molecular weight polyethylene, approximately 130 to 160°C for low molecular weight polypropylene, and the specific gravity is approximately 0.90 to 0.95 for low molecular weight polyethylene and approximately 0.88 to 0.93 for low molecular weight polypropylene. It is. If the molecular weight of the low molecular weight polyolefin is less than 500, the low molecular weight polyolefin may bleed to the interface and impede the adhesion between the layers, while if the molecular weight exceeds 10,000, saponified ethylene-vinyl acetate copolymer (A) Insufficient compatibility with the skin can cause rough skin. A particularly preferred molecular weight range is 1000
~8000. Saponified ethylene-vinyl acetate copolymer (A) 100
The amount of low molecular weight polyolefin to be added to parts by weight should be selected within the range of 0.01 to 0.5 parts by weight, preferably 0.05 to 0.5 parts by weight; less than 0.01 parts by weight will result in poor modification effect, while more than 0.5 parts by weight. Tokiha saponified ethylene-vinyl acetate copolymer (A)
Characteristics (oxygen barrier, oil resistance, solvent resistance,
(rigidity, dimensional stability, etc.) and the adhesion between the layers.If the amount increases even further, the external lubricity of the low molecular weight polyolefin may cause slippage during kneading or extrusion molding. , machining becomes difficult. After adding a low molecular weight polyolefin to the saponified ethylene-vinyl acetate copolymer (A) powder or pellets and mixing with a Henschel mixer, tumbler, etc., the mixture may be subjected to coextrusion molding as it is, or the mixture may be subjected to coextrusion molding. It may be pelletized and then subjected to coextrusion molding. The temperature conditions for coextrusion molding are approximately 160 to 260℃.
It is preferable to set it at ℃. During molding, at least one of the saponified ethylene-vinyl acetate copolymer (A) or a thermoplastic resin other than the saponified copolymer (A) (B) may be reinforced with glass fiber, carbon fiber, etc. as necessary. Appropriate amounts of known additives such as materials, fillers, colorants, stabilizers, and blowing agents can also be blended. Examples of coextrusion molding methods include T-die method,
Blow molding method, pipe extrusion method, profile die extrusion method, line extrusion method, inflation method, etc. can be adopted. Thermoplastic resins (B) other than saponified ethylene-vinyl acetate copolymer (A) include low-density polyethylene, medium-density polyethylene, high-density polyethylene,
Ethylene-vinyl acetate copolymer, ionomer,
Ethylene-α-olefin (α- with 3 to 20 carbon atoms)
Olefin) copolymer, ethylene-acrylic acid ester copolymer, polypropylene, propylene
α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, a single or copolymer of olefin such as polybutene, polypentene, or a single or copolymer of these olefins with an unsaturated carboxylic acid or an ester thereof. Polyolefin resins in a broad sense, such as graft-modified ones, are preferably used, and in addition, polyesters, polyamides,
Copolymerized polyamide, polyvinyl chloride, polyvinylidene chloride, acrylic resin, styrene resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, chlorinated polyethylene, chlorinated polypropylene, etc. are also used.
A saponified ethylene-vinyl acetate copolymer (A) having a different composition from the above-mentioned saponified ethylene-vinyl acetate copolymer (A) can also be used. The layer structure during coextrusion is the saponified ethylene-vinyl acetate copolymer layer A (A1, A2,...),
When other thermoplastic resin layers are B (B1, B2,...), if it is a film, sheet, bottle, etc.
Not only A/B two-layer structure, but also B/A/B, A/
B/A, A1/A2/B, A/B1/B2, B/A/
Any combination such as B/A/B, B2/B1/A/B1/B2 is possible, and if it is filament-like,
A/B bimetal type, core (A) - sheath (B) type, core (B) - sheath
Any combination such as type (A) or eccentric core-sheath type is possible. Also saponified ethylene-vinyl acetate copolymer (A)
Blend the saponified ethylene-vinyl acetate copolymer (A) with the other thermoplastic resin (B), or blend the saponified ethylene-vinyl acetate copolymer (A) with the other thermoplastic resin (B), or An adhesion-imparting resin that improves adhesion may also be blended. The coextrusion molding method obtained as described above includes heat treatment, cooling treatment, rolling treatment, uniaxial or biaxial stretching treatment, printing, dry lamination treatment,
Solution or melt coating processing, bag making processing, deep drawing processing, box processing, tube processing, etc. can be performed. The coextrusion molded product obtained by the method of the present invention is
It can be used in a wide range of fields including packaging materials. Next, the present invention will be further explained with reference to Examples.
Hereinafter, "parts" and "%" are expressed on a weight basis unless otherwise specified. Example 1 Three-layer blow molding was performed under the following conditions. Resin used (A): ethylene content 33 mol%, saponification degree of vinyl acetate component, 100 parts of saponified ethylene-vinyl acetate copolymer with 99.5 mol%, molecular weight 2000, temperature 140.
Melt viscosity at ℃ 2.9 poise, softening point 107℃,
A composition containing 0.2 parts of low molecular weight polyethylene in the form of white powder with a specific gravity of 0.93 and pelletizing it using an extruder. (B1): Modified polypropylene made by modifying polypropylene with 0.3% carboxylic acid. (B2): Polypropylene with melt index 0.8. Molding conditions For extruder (A) 30 mm diameter extruder (for inner layer) For (B1) 30 mm diameter extruder (for middle layer) For (B2) 65 mm diameter extruder (for outer layer) Screw Both L/D = 28, compression Ratio 3.2 die three-layer die, mandrel diameter 26mmφ, core diameter
22mmφ Extrusion temperature Cylinder tip (A): 240℃, (B1): 220℃ (B2): 220℃ Die 200℃ Screw rotation speed (A) 40rpm (B1) 40rpm (B2) 100rpm Molded product shape Capacity Hollow bottle of 300c.c. Wall thickness inner layer: (A) 30μ Intermediate layer: (B1) 30μ Outer layer: (B2) 330μ Example 2 Instead of the low molecular weight polyethylene of Example 1, polyethylene with a molecular weight of 5000 and melted at a temperature of 140℃ was used. A hollow bottle was produced in the same manner as in Example 1, except that white powdery low molecular weight polyethylene having a viscosity of 43 poise, a softening point of 111° C., and a specific gravity of 0.93 was used. Control Example 1 An attempt was made to manufacture a hollow bottle in the same manner as in Example 1 except that low molecular weight polyethylene was not added, but the screw torque increased significantly after 4 hours after the start of molding, making long-run molding impossible. It was hot. Control Examples 2 to 5 Hollow bottles were produced in the same manner as in Example 1, except that 0.2 parts of propylene bisamide (Control Example 2) and 0.2 parts of calcium stearate (Control Example 3) were used in place of 0.2 parts of low molecular weight polyethylene. did. Further, hollow bottles were produced in the same manner as in Example 1, except that the proportion of low molecular weight polyethylene was 2.2 parts (Comparative Example 4) and the proportion of low molecular weight polyethylene was 5 parts (Comparative Example 5). The results of Examples 1 to 2 and Control Examples 1 to 5 above are summarized as
Shown in the table.

[Table] Example 3 A two-layer film was produced by T-die extrusion under the following conditions. Resin used (A): 100 parts of a saponified ethylene-vinyl acetate copolymer with an ethylene content of 48 mol% and a degree of saponification of the vinyl acetate component of 92.5 mol%, a molecular weight of 3500, and a temperature of 140°C.
Low molecular weight polyethylene in the form of white powder with a melt viscosity of 10 poise, a softening point of 108°C, and a specific gravity of 0.93.
A powder composition obtained by blending 0.4 parts. (B): Vinyl acetate content 5%, melt index 2
Molding conditions for ethylene-vinyl acetate copolymer Extruder (for A) 40 mm diameter extruder (for B) 90 mm diameter extruder Screw Both L/D = 28, compression ratio 4.8 Die manifold type double layer die, die width
1000mm, lip width 0.7mm Extrusion temperature Cylinder tip (A): 210℃, (B): 220℃ Die 200℃ Screw rotation speed (A) 80rpm (B) 100rpm Take-up speed 80m/min Cooling condition 35℃ Extruded onto a cooling roll Film thickness: 80μ (A) layer: 20μ (B) layer: 60μ Example 4 Instead of low molecular weight polyethylene, molecular weight 1500,
Melt viscosity 1.8 poise at temperature 190℃, softening point
A two-layer film was obtained in the same manner as in Example 3 except that white powdery low molecular weight polypropylene with a specific gravity of 0.90 was used at 105°C. Control Examples 76-9 A two-layer film was prepared in the same manner as in Example 3, except that 0.4 parts of calcium stearate (Control Example 6) and 0.4 parts of barium stearate (Control Example 7) were used in place of 0.4 parts of low molecular weight polyethylene. Obtained. Further, a two-layer film was obtained in the same manner as in Example 3, except that the low molecular weight polyethylene was mixed at 2.2 parts (Control Example 8) and the low molecular weight polyethylene was mixed at 5 parts (Control Example 9). The results of Examples 3 and 4 and Control Examples 6 and 9 above are summarized in the second section.
Shown in the table.

【table】

Claims (1)

[Scope of Claims] 1. A saponified ethylene-vinyl acetate copolymer (A) having an ethylene content of 15 to 55 mol% and a saponification degree of vinyl acetate component of 90 mol% or more, and a saponified copolymer other than the saponified copolymer (A). When coextruding with the thermoplastic resin (B),
Said saponified ethylene-vinyl acetate copolymer (A)
1. A method for producing a coextruded product, which comprises blending 0.01 to 0.5 parts by weight of a low molecular weight polyolefin with a molecular weight of 500 to 10,000 to 100 parts by weight. 2 The molecular weight of low molecular weight polyolefin is 1000~
8000, the manufacturing method according to claim 1. 3 Claim 1 in which the low molecular weight polyolefin is low molecular weight polyethylene or a derivative thereof
Manufacturing method described in section. 4. The manufacturing method according to claim 1, wherein the low molecular weight polyolefin is low molecular weight polypropylene or a derivative thereof.