JP3218239B2 - Multilayer structure molding material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel molding material having a multilayer structure, and more particularly, to a molding material having a barrier property without impairing the excellent moldability of a styrene resin. Things.

[0002]

2. Description of the Related Art In recent years, plastic packaging materials include (1)
Hygiene, (2) protection, (3) processability, (4) convenience,
(5) It has features such as economical efficiency, it is light, its contents are visible, it has a high degree of freedom in the form that it can be used in bags and containers, it is suitable for mass production, it is inexpensive, it has low gas barrier properties and keeps freshness Its demand is rapidly growing because it is easy to provide the functions of.

[0003] Among plastics, polystyrene has excellent thermoformability and rigidity, so that it has been widely used in containers for food packaging and the like. On the other hand, ethylene-vinyl alcohol copolymer has a high barrier property, and It is widely used as a packaging material.

[0004] Multilayered materials combining polystyrene and an ethylene-vinyl alcohol copolymer are known, and various materials are known. These are based on the molding temperature of polystyrene and the ethylene-vinyl alcohol copolymer. Since the molding temperature is different, molding conditions are narrow, and such a multilayer structure material generally has a drawback that it is difficult to mold in a low-temperature molding region of a single polystyrene sheet.

On the other hand, a polystyrene layer / adhesive resin layer / ethylene-polyvinyl alcohol copolymer layer / adhesive resin layer /
A laminated material comprising a polystyrene layer is also known, but in this laminated material, no consideration is given to a sheet configuration in consideration of formability during the production.

[0006]

SUMMARY OF THE INVENTION Under such circumstances, the present invention is capable of thermoforming even at a temperature of 120 ° C. or less which has excellent moldability of a styrene resin and has a barrier property. An object of the present invention is to provide a styrenic resin / ethylene-polyvinyl alcohol copolymer-based multilayer molding material.

[0007]

The present inventors have conducted various studies to improve the moldability of a styrene resin / ethylene-polyvinyl alcohol copolymer-based multilayered molding material having a barrier property. -It has been found that, if a vinyl alcohol copolymer having a specific DSC behavior which has not been known before is used, thermoforming can be performed even at a temperature as low as 120 ° C. or less, and the present invention based on this finding has led to the present invention. I've reached the point.

That is, the present invention has a multilayer structure in which (A) an ethylene-vinyl alcohol copolymer layer, (B) an adhesive resin layer and (C) a styrene-based resin layer are combined, and the (A) layer When the ethylene-vinyl alcohol copolymer of the formula ( ₁₎ has an integral value S of the entire DSC peak in the heating process, the integral value S ₁ up to 160 ° C. is 30% or more of S,
Integral value S ₂ up to 150 ° C is 20% or more of S, 140 ° C
The DSC behavior shows that the integrated value S _{3 up} to 15% or more of S, the integrated value S ₄ up to 130 ° C. is 10% or more of S, and the integrated value S ₅ up to 120 ° C. is 5% or more of S. An object of the present invention is to provide a multilayer structure molding material which can be thermoformed even at 120 ° C. or lower.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The multilayer structure molding material of the present invention comprises:
(A) At least one layer of an ethylene-vinyl alcohol copolymer, (B) at least one layer of an adhesive resin, and (C) at least one layer of a styrene-based resin. Thus, it has at least 3 layers, but often 5
It has layers or more layers.

It is advantageous that the ethylene-vinyl alcohol copolymer has a melt index (MI) of 10 g / 10 minutes or less (190 ° C.) when extruding a multilayer structure. If it is too large, the distribution of the barrier layer in the lateral direction of the sheet deteriorates.

Further, the ethylene-vinyl alcohol copolymer preferably has an ethylene unit content of 35 mol% or less and a melting point of 185 ° C. or less.
Those having more than mol% generally have low barrier properties, and those having a melting point of more than 185 ° C. generally tend to cause defective phenomena such as cracks. Further, the thickness of the ethylene-vinyl alcohol copolymer layer is desirably 20% or less, preferably less than 10% of the entire thickness, and the moldability is improved by making the barrier layer thin.

In the present invention, it is necessary to use a copolymer exhibiting a specific DSC behavior as the ethylene-vinyl alcohol copolymer. FIG. 1 shows (A) of the present invention.
3 is a heating process DSC curve for explaining a DSC behavior of an ethylene-vinyl alcohol copolymer of a layer. And
If the heating process DSC curve is represented by equation f (T) and the base A → C → B curve is represented by equation g (T) with temperature as the horizontal axis and calorific value as the vertical axis, the integral of the entire heating process DSC peak is obtained. The value S is given by the formula

(Equation 1)Is represented by In addition, up to 160 ° C for this peak
Is the integral value of₁, The integrated value up to 150 ° C is S_Two, 140 ° C
The integral value up to S_Three, And the integrated value up to 130 ° C is S _Four, 12
The integral value up to 0 ° C is S_FiveThen these are:
(II) to (VI).

[0013]

(Equation 2)

The ethylene-vinyl alcohol copolymer in the layer (A) of the present invention must satisfy all of the following conditions. (S ₁ / S) × 100 ≧ 30 (%) (S ₂ / S) × 100 ≧ 20 (%) (S ₃ / S) × 100 ≧ 15 (%) (S ₄ / S) × 100 ≧ 10 ( %) (S ₅ / S) × 100 ≧ 5 (%)

By satisfying such conditions, the multilayer structure molding material of the present invention can be thermoformed even at a low temperature of 120 ° C. or less without causing unevenness or cracks when molding a container. As a result, the shot cycle can be improved, and the molding cost can be reduced.

In the multilayer structure molding material of the present invention, the adhesive resin of the layer (B) preferably has an end point of the DSC peak in the heating step of 130 ° C. or less from the viewpoint of moldability, more preferably 100 ° C. or less. Is preferred. If the end point of the peak exceeds 130 ° C., uneven elongation tends to occur when molded.

This adhesive resin has a melt index (M
Those having I) of 20 g / 10 min or less (measured in accordance with JIS K-6730) are preferable for extrusion molding of a multilayered molding material. If the MI exceeds 20 g / 10 min, the distribution state of the adhesive resin layer is reduced. It becomes worse or the flow becomes uneven. Furthermore, this adhesive resin has a melting point of 70 ° C. in terms of heat resistance.
The above are preferred. When the resin having a melting point of less than 70 ° C. is hot-filled (filled with contents of about 70 ° C.), the adhesive resin layer is peeled off. In molding the multilayer structure molding material, an extrusion molding method, a lamination method, or the like is used. As such an adhesive resin, for example, an ethylene-vinyl acetate copolymer, a modified ethylene-vinyl acetate copolymer, an α-olefin copolymer and a modified product thereof are preferable.

The styrene resin of the layer (C) in the multilayer structure molding material of the present invention includes, for example, impact-resistant polystyrene, styrene-based special transparent resin, general-purpose polystyrene, syndiotactic polystyrene, acid-modified polystyrene,
A mixture of these, or a mixture of these with a styrene-based elastomer is used, and properties such as rigidity, impact resistance, heat resistance, and transparency can be adjusted by appropriately selecting these compositions.

The layer structure of the multilayer structure molding material of the present invention is based on (A) / (B) / (C), and another resin layer (D) may be laminated. Particularly, a layer structure close to the symmetry of (C) / (B) / (A) / (B) / (C) is particularly preferable. Also, JP-A-3-212380
As shown in the publication, a special polystyrene layer may be provided to provide a polyolefin layer on the surface.

The multilayer structure molding material of the present invention has a thickness of 0.1 to
It is advantageous to make a multilayer sheet of about 2.0 mm. This sheet can be formed into a multi-layered container having an opening peripheral portion for sealing the lid member in a ring shape, and can be used for storing contents that cause oxygen deterioration.

If the multilayer structure molding material of the present invention is used, 12
Thermoforming can be performed even at a temperature of 0 ° C. or less,
A multi-layered container in a good molded state can be obtained within the allowable range of not less than ° C. As the thermoforming method, for example, a vacuum forming method, a press forming method, a vacuum press forming method, or a forming method in which plug assist is added thereto is used. In this way, a multi-layer container suitable for food preservation and the like having an extremely high oxygen barrier property can be easily formed with a low defect rate as compared with a polystyrene single-layer sheet.

Further, as for heating during thermoforming, a hot plate heater or the like may be used as direct heating, or an infrared heater or the like may be used as indirect heating.

[0023]

According to the present invention, a specific thermal behavior is exhibited.
By laminating a combination of an ethylene-vinyl alcohol copolymer, an adhesive resin and a styrene resin, a multilayer structure molding material having a barrier property can be obtained without significantly deteriorating the excellent moldability of the styrene resin.

Further, when the multilayer structure molding material of the present invention is used, a multilayer structure container suitable for preserving foods having extremely high oxygen barrier properties can be efficiently produced at a low defective rate and at a low cost.

[0025]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. In addition, evaluation of thermoformability was performed as follows.

(1) Molding State The molding state at the molding temperature was evaluated according to the following criteria. 10: Barrier layer has no unevenness 9: Barrier layer has minute unevenness 8: Barrier layer has slight unevenness 7: Barrier layer has slight stripe pattern 6: Barrier layer has stripe pattern 5: Barrier layer has wrinkles 4: Barrier layer has cracks 3: Barrier layer has many cracks 2: Molding state is very bad 1: Molding is impossible

(2) Moldability The temperature range in which the above-mentioned molding state was obtained was measured and evaluated according to the following criteria. 10: At a temperature of 160 ° C. or less, the temperature range of the molded state 10 is 40 ° C. or more 9: At a temperature of 160 ° C. or less, and the temperature range of the molded state 10 is 20 ° C. or more 8: At a temperature of 160 ° C. or less The temperature range of the molding state 10 is 10 ° C. or more. 7: The molding can be performed at the temperature range of 150 ° C. or less in the molding state 10 6: The molding can be performed in the molding state 10 5: The temperature range in the molding state 7 Can be molded at 150 ° C. 4: Can be molded in molding state 5 3: When molded at 160 ° C. or less, cracks are produced 2: Molding is possible, but molding state is very poor 1: Molding is not possible

Example 1 As an ethylene-vinyl alcohol copolymer, a sample having a MI value of 1.8 g / 10 min and a DSC peak temperature of 190 ° C. and a heating DSC peak behavior shown in Table 1 [Products manufactured by Kuraray Co., Ltd. Symbol, EVAL trial 1] (EVOH-1)
As a styrene-based resin, an impact-resistant polystyrene having an MI value of 2 g / 10 min [trade name "Idemitsu Styrol ET-60" manufactured by Idemitsu Petrochemical Co., Ltd.] (PS-1), and an MI value as an adhesive resin An ethylene-vinyl acetate copolymer having a DSC peak end temperature of 93 ° C. at 2 g / 10 min [trade name “Mersen M-5420” manufactured by Tosoh Corporation] (AD-
1) is used, PS-1 is 60φ, AD-1 is 5
0φ, EVOH-1 was extruded through a feed block and a die by an extruder of 50φ, and then roll-cooled, and PS-1 / AD-1 / EVOH-1 / AD-1 /
A sheet-like multilayer structure molding material having a PS-1 (thickness ratio: 45/3/4/3/45) was produced.

Comparative Examples 1 to 8 For comparison, a sheet-like multilayered molding material was produced in the same manner as in Example 1 by using a commercially available ethylene-vinyl alcohol copolymer shown below.

EVOH-2: Ethylene-vinyl alcohol copolymer, manufactured by Kuraray Co., Ltd., EVAL EP K-1
02B (MI value 2.8 g / 10 min) (190 ° C.) EVOH-3: ethylene-vinyl alcohol copolymer,
EVAL EP E-105B (MI
Value 5.5 g / 10 min) (190 ° C.) EVOH-4: ethylene-vinyl alcohol copolymer,
EVAL EP G-156B (MI
Value: 6.4 g / 10 min) (190 ° C.) EVOH-5: ethylene-vinyl alcohol copolymer,
EVAL EP G-110B (MI) manufactured by Kuraray Co., Ltd.
Value: 14 g / 10 min) (190 ° C.) EVOH-6: ethylene-vinyl alcohol copolymer,
EVAL EP F-100B (MI
Value: 0.6 g / 10 min) (190 ° C.) EVOH-7: ethylene-vinyl alcohol copolymer,
EVAL EP T-102B (MI
Value: 2.1 g / 10 min) (190 ° C.) EVOH-8: ethylene-vinyl alcohol copolymer,
EVAL EP L-101B (MI
Value: 3.0 g / 10 min) (210 ° C.) EVOH-9: ethylene-vinyl alcohol copolymer,
Soarnol AT4403 (MI manufactured by Nippon Synthetic Chemical Co., Ltd.)
Value: 3.0 g / 10 min) (210 ° C.)

Table 1 shows the DSC behavior of these ethylene-vinyl alcohol copolymers in the heating process.

[0032]

[Table 1]

Example 2 In place of the styrene resin PS-1 in Example 1, M
Ordinary polystyrene having an I value of 4 g / 10 min [trade name "Idemitsu Styrol HH-30E" manufactured by Idemitsu Petrochemical Co., Ltd.]
(PS-2), acid-modified polystyrene having an MI value of 0.7 g / 10 min [trade name "Idemitsu Moremax UH-830" manufactured by Idemitsu Petrochemical Co., Ltd.] (PS-3), MI value of 8.0 g /
Styrene-based special transparent resin for 10 minutes [Philips Co., Ltd.
Made, product name "KR-03"] (PS-4) or PS-1
Styrene-isoprene elastomer [Shell Chemical Co., Ltd., trade name "Califlex TR1107"]
(SIS) 10% by mass of each was used.
Except for this, a sheet-like multilayer structure molding material was produced in exactly the same manner.

Reference Example The multilayer structure molding material obtained in Example 1 and Comparative Examples 1 to 8 was
Container molding machine CM-6 manufactured by United Mold Co., Ltd.
333, sheet heating temperature 120 to 190 ° C., clamping pressure 5 kg / cm ² , sheet stretching speed 3 m / s
ec, a mold temperature of 30 ° C., a container drawing ratio of 0.5, and molding conditions with a plug, and the moldability was evaluated. The results are shown in Tables 2 and 3.

[0035]

[Table 2]

[0036]

[Table 3]

When the molding material of the multilayer structure obtained in Example 2 was used, a molded article having almost the same physical properties as in Example 1 was obtained.

Comparative Example 9 An ethylene-vinyl acetate copolymer having a MI value of 7.5 g / 10 min and a DSC peak end temperature exceeding 130 ° C. (trade name “Mersen M-M” manufactured by Tosoh Corporation) was used as an adhesive resin. 5
321 "] (AD-2), and a molded article was produced in the same manner as in Example 1 using the multilayer structure molding material.
The molding temperature at this time was as high as 150 to 160 ° C., the molding state was 4 to 7, and the moldability was 5.

[Brief description of the drawings]

FIG. 1 is a graph for explaining the behavior of a DSC peak of an ethylene-vinyl alcohol copolymer known in the present invention.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (4)

(57) [Claims] 1. A multilayer structure comprising a combination of (A) an ethylene-vinyl alcohol copolymer layer, (B) an adhesive resin layer, and (C) a styrene-based resin layer. Alcohol copolymer is heated DSC
Assuming that the integrated value of the entire peak is S, the integrated value S ₁ up to 160 ° C. is 30% or more of S and the integrated value S ₂ up to 150 ° C.
Is 20% or more of S, and the integrated value S ₃ up to 140 ° C. is 1% of S.
D in which the integrated value S ₄ up to 5% and 130 ° C. is 10% or more of S and the integrated value S ₅ up to 120 ° C. is 5% or more of S
A multi-layered molding material which can be thermoformed even at a temperature of 120 ° C. or lower, which exhibits SC behavior. 2. The multilayer structure molding material according to claim 1, wherein the adhesive resin of the layer (B) has an end point of the DSC peak in the heating step of 130 ° C. or lower. 3. The styrene resin is at least one selected from impact-resistant polystyrene, general-purpose polystyrene, acid-modified polystyrene and syndiotactic polystyrene, or a mixture of these with a styrene elastomer. The multi-layer structure molding material according to the above. (C) / (B) / (A) / (B) /
The multilayer structure molding material according to any one of claims 1 to 3, which has a laminated structure (C).