JPH0578534A - Ethylene-vinyl alcohol copolymer composition containing polyamide resin and excellent in processing stability - Google Patents

Abstract

PURPOSE:To provide the subject compsn. which scarcely forms gel during extrusion. CONSTITUTION:The objective compsn. is prepd. by compounding a resin component consisting of 60-95wt.% ethylene-vinyl alcohol copolymer and 40-5wt.% polyamide resin with a processing stabilizer consisting of a block copolymer of an A-B-A type (wherein A is an arom. vinyl polymer block and B is a hydrogenated conjugated-diene polymer block contg. units derived from an unsatd. carboxylic acid).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ethylene-vinyl alcohol copolymer composition containing a polyamide resin, which is excellent in processing stability with less generation of gel-like substances during extrusion processing.

[0002]

2. Description of the Related Art Ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) has excellent gas barrier properties, aroma retention, oil resistance, high transparency, etc., and is conventionally used for packaging foods and the like. Widely used as films and containers. In addition, polyvinylidene chloride-based resins are also known as gas barrier resins currently used for such purposes, but in recent years, when the problem of global environmental pollution has become serious, chlorine-based resins have been used. Due to the unavoidable tendency to eliminate resins, EVOH, which does not contain chlorine, has attracted great attention as an alternative resin.

However, as is well known, since EVOH is a resin having a high hydrophilicity, it has a large moisture permeability and lacks hot water resistance.
Although it can be applied to boiling applications of about ℃, in the field of retort which requires a higher degree of hot water resistance, there is a problem that the film is bleached or the strength is significantly reduced by high temperature sterilization.

Therefore, as a method for improving the problem of hot water resistance, a method of blending EVOH with a polyamide resin such as nylon-6 has been proposed (Japanese Patent Publication No. 44-2).
4277, JP-B-60-24813, JP-A-63-125334, JP-A-1-308626.
However, such polyamide resin is EV
Since it is extremely reactive with OH, the resin retained in the extruder or die during the melt extrusion crosslinks and gels, and in turn, a large number of gel-like substances that have lost this fluidity are mixed in the molded product. Since it is in a situation of being extruded, there is a big problem that continuous molding cannot be performed for a long time.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to exert an excellent effect in preventing the formation of gel-like substances during extrusion.
Another object is to provide a polyamide resin-blended ethylene-vinyl alcohol copolymer composition having excellent processing stability.

[0006]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the present inventors have found that a specific aromatic vinyl compound block copolymer is added to a system consisting of EVOH and a polyamide resin. For example, they found that the viscosity increase due to the reaction between the two was suppressed and the extrusion processing stability was remarkably improved, and the present invention was conceived.

That is, the present invention uses 60 to 95% by weight of ethylene-vinyl alcohol copolymer and 40% of polyamide resin.
To 5% by weight, as a processing stabilizer, an A-B-A type block copolymer (where A is a polymer block of an aromatic vinyl compound and B is a hydrogenation partially unsaturated carboxylic acid is added). The present invention relates to a polyamide resin-blended ethylene-vinyl alcohol copolymer composition having excellent processing stability, characterized in that a conjugated diene compound polymer block) is added.

In the present invention, EVOH is obtained by hydrolyzing a vinyl acetate unit in a copolymer of ethylene and vinyl acetate. Specifically, it has an ethylene content of 10 to 50% by weight, preferably 20 to 45% by weight. , Saponification degree 90%
Above, preferably 95% or more is exemplified. Here, when the ethylene content is less than 10% by weight, it is not preferable because the extrusion moldability is poor and the heat stability is poor, and when the ethylene content exceeds 50% by weight, the gas barrier property is lost. On the other hand, when the saponification degree is less than 90%, the gas barrier property is significantly lowered, and the thermal dimensional stability of the obtained molded product is deteriorated.

The polyamide resin used in the present invention means polycaprolactam (nylon-6), polyundecaneamide (nylon-11), polylaurolactam (nylon-12), polyhexamethyleneadipamide (nylon-6). , 6), polyhexamethylene dodecamide (nylon-6,12), or poly (caprolactam / laurolactam) copolymer (nylon-6 / 12), poly (caprolactam / aminoundecanoic acid) copolymer (nylon- 6/11), poly (caprolactam / hexamethylene diammonium adipate) copolymer (nylon-6 / 6,6), poly (caprolactam / hexamethylene diammonium adipate / hexamethylene diammonium sebacate) copolymer (nylon -6/6, 6 /
6, 12) and the like.

Of these, nylon-6,
Nylon-6 / 12, Nylon-6 / 11, Nylon-
Polycaprolactam or polycaprolactam block of 6 / 6,6, nylon-6 / 6,6 / 6,12, etc. 60
It is more preferable that the content of at least wt% is relatively good in compatibility with EVOH and exhibits excellent effects such as improvement in hot water resistance, stretchability and impact resistance.

The base resin composition of the present invention is composed of 60 to 95% by weight of EVOH and 40 to 5% by weight of polyamide resin. When the content of the polyamide resin in EVOH is less than 5% by weight, the effect of improving hot water resistance is small, while when it exceeds 40% by weight, the gas barrier property is deteriorated and the EVOH properties are lost, which is not preferable.

The composition excellent in processing stability according to the present invention is obtained by adding the composition of EVOH and polyamide resin to
-BA type block copolymer (where A is a polymer block of an aromatic vinyl compound, B is a hydrogenated conjugated diene compound polymer block to which an unsaturated carboxylic acid is partially added) was added. It is a thing.

Here, as the aromatic vinyl compound constituting the ABA type block copolymer (hereinafter referred to as a modified block copolymer), styrene, α-methylstyrene, o-methylstyrene, m- Methyl styrene, p-methyl styrene and the like can be used, but among these, styrene is particularly preferable, and the conjugated diene compound is 1,
3-Butadiene, isoprene and the like are used, among which 1,
3-Butadiene is preferred. The content of the aromatic vinyl compound in the block copolymer composed of the aromatic vinyl compound and the conjugated diene compound is preferably 10 to 40% by weight from the viewpoint of compatibility with EVOH and the number of the block copolymers. The average molecular weight is generally about 20,000 to 500,000.

The modified block copolymer of the present invention is obtained by hydrogenating a block copolymer consisting of the terminal block of the above aromatic vinyl compound polymer and the intermediate block of the conjugated diene compound polymer to obtain an intermediate conjugated diene compound polymer. After hydrogenating the block, the unsaturated carboxylic acid is partially added to the hydrogenated conjugated diene compound polymer block. Here, the hydrogenation ratio is preferably such that at least 80% of the aliphatic double bonds of the intermediate conjugated diene compound polymer block are hydrogenated.

As the unsaturated carboxylic acid added to the hydrogenated conjugated diene compound polymer block, maleic acid, itaconic acid, cis-4-cyclohexene-1,2-
Examples thereof include dicarboxylic acid and the like, and anhydrides of these dicarboxylic acids. Among these, maleic anhydride is particularly preferable. The addition amount of these unsaturated carboxylic acids is preferably less than 10% by weight of the whole block copolymer, and even if added more than that, the effect of improving processing stability cannot be expected so much. still,
Typical examples of the modified block copolymer used in the present invention include a polystyrene end block and an intermediate block of a hydrogenated block copolymer composed of a poly (ethylene / butylene) intermediate block in which polybutadiene is hydrogenated. A reactive polymer to which maleic anhydride has been added, which is available from Shell Chemical Company of the United States as "Clayton FG-1901.
Examples are those marketed under the trade name "X".

In the present invention, the amount of the modified block copolymer is preferably 0.5 to 10 parts by weight based on 100 parts by weight of the composition comprising EVOH and polyamide resin. When the amount of the modified block copolymer is less than 0.5 parts by weight, the effect of improving the processing stability is insufficient, while when it is more than 10 parts by weight, the effect corresponding to it cannot be expected to be improved. Or EV
The excellent gas barrier property peculiar to OH is impaired.

If desired, the composition of the present invention may further contain various additives such as antioxidants, ultraviolet absorbers, light stabilizers, lubricants, colorants, flame retardants and inorganic fillers. I don't care. Further, the EVOH composition of the present invention can be stably formed into a film or sheet by a usual method such as melt extrusion, stretching, and heat setting, and can also be applied to a container by injection molding. ..

[0018]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited thereto.

In the present invention, a retention test with the following melt indexer was conducted as a standard for judging the quality of processing stability. (Staying Test by Melt Indexer) Using a melt indexer manufactured by Takara Kogyo Co., Ltd., the test composition was allowed to stay in a cylinder heated to a temperature of 250 ° C., and the fluidity (unit: g) with time elapsed. / 10 min) change was measured under a load of 2160 g. In this test, it is shown that the less the fluidity (that is, the melt index) decreases due to the retention, the less the generation of gel-like substances during extrusion, and the more excellent the processing stability is.

Examples 1 to 3, Comparative Examples 1 to 3 EV having ethylene content of 28% by weight and saponification degree of 99% or more
OH (Kuraray's "Eval L101") 80% by weight,
Resin 10 obtained by blending 20% by weight of nylon-6 / 12 copolymer ("Amilan CM6541" manufactured by Toray) having a copolymerization ratio of nylon-6 and nylon-12 of 9: 1 by weight.
A modified block copolymer obtained by adding 2% by weight of maleic anhydride to the middle block of a styrene- (ethylene / butylene) -styrene block copolymer having a styrene content of 28% by weight (0% by weight). FG
-1901X ") in various proportions and then 20 mm
Melted and kneaded with a φ extruder to form pellets. A retention test was performed on the obtained pellets using the melt indexer, and the fluidity after retention for 30 minutes and 45 minutes was measured to evaluate the quality of processing stability. For comparison, when the modified block copolymer was not added (Comparative Example 1),
And when a commercially available styrene-butadiene-styrene block copolymer is added instead of the modified block copolymer (Comparative Example 2), a commercially available maleic acid is not added instead of the modified block copolymer. Styrene
The processing stability was evaluated by the same method for the case where (ethylene / butylene) -styrene block copolymer was added (Comparative Example 3). The results are shown in Table 1. From the table, the composition to which the modified block copolymer of the present invention was added showed less deterioration in fluidity in the retention test with the melt indexer and was excellent in processing stability. It was

[0021]

[Table 1] In the additives in the table, M-SEBS is the modified block copolymer of the present invention, SBS is a styrene-butadiene-styrene block copolymer, and SEBS is styrene- (ethylene / butylene)-. Each of the styrene block copolymers is shown.

Example 4, Comparative Examples 4-5 Nylon-6 instead of nylon-6 / 12 copolymer
Pellets were prepared in the same manner as in Example 2 except that (Toray's "Amilan CM1041") was used, and the resulting pellets were measured for fluidity after retention for 15 minutes and 30 minutes with the melt indexer. Then, the processing stability was evaluated. Also in this case, for comparison, no modified block copolymer was added (Comparative Example 4), and a commercially available styrene- (ethylene / butylene) in which maleic acid was not added in place of the modified block copolymer was used. ) -Styrene block copolymer was compounded (Comparative Example 5), and the processing stability was evaluated. The results are shown in Table 2. From the table, the composition of the present invention showed less deterioration in fluidity in the retention test with the melt indexer and was excellent in processing stability.

[0023]

[Table 2] In the additives in the table, M-SEBS is the modified block copolymer of the present invention, and SEBS is a styrene- (ethylene / butylene) -styrene block copolymer.

[0024]

INDUSTRIAL APPLICABILITY As described above, the EVOH composition of the present invention, which is excellent in processing stability, suppresses gelation due to blending of polyamide resins and enables continuous molding for a long time. Therefore, according to the composition of the present invention, although many proposals have been made to improve the hot water resistance of EVOH, the blend of EVOH-polyamide resin, which has been difficult to put into practical use due to the problem of processing stability, has been proposed. It greatly opens the way to practical use, and is of extremely high industrial value.

Claims (3)

[Claims] 1. An ethylene-vinyl alcohol copolymer 6
0 to 95% by weight and polyamide resin 40 to 5% by weight
In addition, as a processing stabilizer, an ABA type block copolymer (where A is a polymer block of an aromatic vinyl compound, B
Is a hydrogenated conjugated diene compound polymer block to which an unsaturated carboxylic acid is partially added), which is excellent in processing stability, and is a polyamide resin-blended ethylene-vinyl alcohol copolymer composition. object. 2. The polyamide resin according to claim 1, comprising a polycaprolactam or a polycaprolactam block.
A polyamide resin-blended ethylene-vinyl alcohol copolymer composition having excellent processing stability, which is a polyamide resin copolymer containing 0% by weight or more. 3. A polyamide system excellent in processing stability, wherein the ABA type block copolymer according to claim 1 is a (polystyrene block-maleic anhydride-hydrogenated polybutadiene block-polystyrene block) copolymer. A resin-blended ethylene-vinyl alcohol copolymer composition.