JPH0611832B2 - Resin composition of saponified ethylene copolymer - Google Patents

Description

The present invention relates to a resin composition of a saponified ethylene-based copolymer. More specifically, the present invention relates to a resin composition in which a specific polyamide is blended in a specific ratio with a highly saponified ethylene-vinyl acetate copolymer. A film or container formed by extrusion molding from the resin composition of the present invention has both excellent gas barrier properties and impact resistance (pinhole resistance), and is particularly suitable for use as a film or container for packaging foods. be able to. Further, the molded product formed by injection molding from the resin composition of the present invention has excellent impact strength as well as rigidity and heat resistance, and can be used as engineering plastics for various functional parts.

[Description of Prior Art]

In general, a saponified product of an ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH) has a very good gas barrier property, and therefore, a film or container for food packaging which is required to have a low oxygen gas permeation rate. Used as a material for forming In addition, EVOH with glass fiber in particular has high rigidity and heat resistance, so metal parts (Al
It is used for various functional parts as an alternative to die casting, Zn die casting, etc.).

However, this EVOH has the drawback that its molded product is hard and brittle, and is limited in its application. For example,
When used as a film or sheet for food packaging,
During the packaging work, the movement work of the packaged goods, and the transportation work, the film is easily broken or pinholes are easily generated, and the excellent gas barrier property cannot be fully utilized. Furthermore, even when used in injection-molded products, there were many complaints about cracks, especially immediately after molding and at low temperatures.

Generally, the physical properties and moldability of EVOH change depending on the ethylene content and saponification degree. As the ethylene content increases and as the saponification degree decreases, the moldability and impact resistance become better, but conversely the gas barrier property. , Rigidity and heat resistance will decrease. Therefore, a new technique for improving impact resistance without greatly impairing the gas barrier property, rigidity, and heat resistance, which are the characteristics of EVOH, has been strongly expected.

As a means for improving such a drawback of EVOH, E
A method of using a resin composition in which various polyamides are mixed with VOH is disclosed in, for example, Japanese Patent Publication No. 44-24277.
48-22833, JP-A-50-121347, JP-A-54-78749, JP-A-54-7.
It is well known from Japanese Patent No. 8750 and Japanese Patent Laid-Open No. 55-34956.

In the above method, EVOH and polyamide have good compatibility with each other. Therefore, if polyamide is blended with EVOH and blended, it acts to improve the impact resistance of polyamide polyamide, and furthermore, EVOH has excellent original properties. Gas barrier property,
The rigidity and heat resistance are not significantly impaired.

However, this resin composition, which is a mixture of EVOH and polyamide, has a serious problem.

That is, when EVOH and polyamide are mixed in a molten state, a chemical reaction occurs between the two, the melt viscosity increases, and finally gelation occurs, making molding impossible.

Since this gelation becomes more remarkable as the molding temperature becomes higher, means for using various copolyamides having a low melting point as polyamides have been proposed.
For example, JP-A-54-78749 and JP-A-54-
The methods disclosed in JP-A-78750 and JP-A-55-34956 can be mentioned.

However, even with these methods, it is difficult to completely prevent gelation, and EVOH can be used without impairing moldability.
There is a demand for a practical method for improving the impact resistance of the.

[Each requirement and effect of the present invention]

As a result of intensive studies aimed at improving the impact resistance of such EVOH, the present inventors have found that a resin composition obtained by mixing a specific EVOH with a polyamide modified with a specific end group shows no gelation during molding. The inventors have found that it is unlikely to occur, do not impair the gas barrier properties, rigidity, and heat resistance of the molded product, and further improve pinhole resistance or impact resistance, and completed the present invention.

That is, the present invention has 5 to 50 mol% of repeating units (—CH ₂ —CH ₂ ) based on ethylene monomer, and
100 parts by weight of a saponified product of a copolymer of ethylene and vinyl acetate having a saponification degree of 80% or more, and a relative viscosity of 2.1.
~ 3.5 and the amino end group is 8 × 10 ^-5 equivalent / g
Thus, the amino-terminal rich end-modified polyamide having a carboxyl end group of 3 × 10 ⁻⁵ equivalent / g or less 5 to 5
It relates to a resin composition of a saponified ethylene-based copolymer, which is characterized by comprising 150 parts by weight.

The resin composition of the present invention (a) is used for molding films, containers, injection molded products,
Molding does not become difficult due to gelation, and (b) the molded product has sufficient gas barrier properties, rigidity, heat resistance, and improved pinball resistance or impact resistance. Therefore, it can be suitably used as a packaging material or a functional component.

[Detailed description of each requirement of the present invention]

The saponified product (EVOH) of a copolymer of ethylene and vinyl acetate used in the present invention contains repeating units I based on ethylene monomer in an amount of 5 to 50 mol% based on the total amount of the polymer.
Preferably 10 to 45 mol%, particularly preferably 15 to 4
It has a proportion of 0 mol% and a saponification degree of 80%.
As described above, the "saponified ethylene-vinyl acetate copolymer" is preferably 90% or more, and particularly preferably 95% or more.

The saponified product (EVOH) is prepared by saponifying an ethylene-vinyl acetate copolymer obtained by polymerizing an ethylene monomer and a vinyl acetate monomer by a known method, and the repeating product based on the ethylene monomer is used. If the unit I is less than 5 mol% with respect to the saponified product, the moldability of the resin composition obtained using such a saponified product is deteriorated, which is not suitable. On the other hand, the repeating unit based on the ethylene monomer is not suitable. When the content of I is more than 50 mol%, the gas barrier property, rigidity and heat resistance of the molded product molded from the resin composition containing such a saponified product are deteriorated, which is not suitable.

In the present invention, the degree of polymerization of EVOH is not particularly limited, but the intrinsic viscosity (15% by weight in water-containing phenol, 3%
EVOH of 0.07-0.17 (measured at 0 ° C.) is preferably used.

Polyamides that can be used in this invention include nylon 6, nylon 610, nylon 12, etc., but especially EVOH
A nylon 6-based copolymer, for example, a 6/66 copolymer, a 6/12 copolymer, a 66/610/6 copolymer, or the like is preferable from the viewpoint of compatibility with and a decrease in molding temperature. The feature of the present invention is to use a polyamide modified with a specific end group, wherein the amino end group is 8 × 10 ⁻⁵ equivalent / g or more and the carboxyl end group is 3 × 10 ⁻⁵ equivalent / g. It must be: When blended with EVOH using a polyamide that does not satisfy the conditions of such end groups,
The melt viscosity increases during molding, making continuous molding difficult for a long time. As a method for obtaining a polyamide having such an end group, a known method can be applied. For example, addition of a diamine such as an aliphatic diamine such as hexamethylenediamine or an aromatic diamine such as metaxylenediamine at the time of polymerization. Is obtained by

Regarding the degree of polymerization of the polyamide used in the present invention, the relative viscosity is 2.1 to 3.5, more preferably 2.2.
Those in the range 3.2 are used. The relative viscosity is measured according to JIS K-6810 4.4.1 sulfuric acid solution. The sulfuric acid concentration is 98% and the temperature is 25 ° C.

In order to obtain the terminal group as in the present invention, it is difficult to polymerize one having a relatively high relative viscosity, and when the relative viscosity is too low, the desired pinhole resistance or impact resistance when blended with EVOH. No improvement in sex is achieved.

The resin composition of this invention comprises 100 parts by weight of the above EVOH and 5150 parts by weight of the above polyamide, preferably 10 parts by weight.
The resin composition is a saponified ethylene-based copolymer containing 100 to 100 parts by weight as a polymer component.

In the resin composition of the present invention, if the ratio of the polyamide to the saponified product is too small, the molded product formed from such a resin composition may have poor mechanical properties such as pinhole resistance or impact resistance. It is not suitable because it is not improved, and if the proportion of polyamide used relative to the saponified product becomes too large, the gas barrier property, rigidity, etc. of the molded product formed from such a resin composition become insufficient. Not suitable.

The method for preparing the resin composition of the present invention is not particularly limited, and the resin composition can be prepared by the commonly known method "method of mixing the saponified product with polyamide".

That is, as a known mixing method of the saponified product and the polyamide, for example, the saponified product and the polyamide are
Pellet, powder, etc. are mixed uniformly, then melt-kneaded with an extrusion kneader to pelletize, and the pellet is used for molding, or pellets, powder, etc. of the saponified product and polyamide are uniformly mixed. And the mixture is directly supplied to a film molding machine or an injection molding machine,
A method of molding while kneading in the molding machine is suitable.

In order to make the resin composition of the present invention into a film, a container, an injection-molded product, etc., a usual extrusion molding method or injection molding method can be applied. Stable continuous molding is possible.

Films, sheets, etc. made of the resin composition of the present invention are excellent in gas barrier properties and pinhole resistance, and at the same time, have transparency, chemical resistance, etc., and are highly useful. Furthermore, the injection-molded product made of the resin composition of the present invention has excellent rigidity, heat resistance and impact resistance, as well as excellent wear resistance and chemical resistance, and is used as engineering plastics for various functional parts. it can.

The resin composition of the present invention has other components, for example,
Pigment, heat stabilizer, antioxidant, weathering agent, crystallization accelerator,
It also includes those to which an appropriate amount of lubricants, fillers, plasticizers, etc. are added. In particular, those filled with glass fiber are useful as injection molded products because of their high rigidity, creep resistance and heat resistance.

〔Example〕

Hereinafter, the resin composition of the present invention will be described more specifically with reference to Examples and Comparative Examples. The method for measuring the physical properties of the film in each Example or Comparative Example was measured according to the methods described below.

(1) Oxygen permeability Measured using an oxygen gas permeability measuring device (Modern Control Co., OXYTRAN-100 type) under conditions of 20 ° C. and absolutely dry condition.

(2) Pinhole resistance A tensile test was performed in the take-up direction (MD) according to ASTM D-882 in an absolutely dry state at 23 ° C. The tensile modulus and elongation were used as a measure of pinhole resistance. That is, in the above test, the lower the tensile modulus is,
The higher the elongation, the better the pinhole resistance.

Moreover, the measuring method of the relative viscosity in the following Examples and Comparative Examples is the measuring method of the amino terminal group and the carboxy terminal group according to JISK-6810 (method using sulfuric acid solution, sulfuric acid concentration 98%, temperature 25 ° C.) described above. Is Waltz, JEAn
al Chem 19 , 448 (1947). For amino end groups, dissolve the sample in a phenol / methanol mixed solution and use a methyl orange xylene cyanol FF indicator. The carboxy terminal group was dissolved in hot benzyl alcohol and the phenolphthalein indicator was used. It was determined by neutralization titration with an aqueous solution.

Example 1 An ethylene-vinyl acetate copolymer saponified product (EVOH) containing 38 mol% of repeating unit I based on an ethylene monomer, having a saponification degree of 99%, an intrinsic viscosity of 0.14 and a melting point of 173 ° C. ) ”100 parts by weight, relative viscosity 2.7,
43 parts by weight of nylon 6 (A) having amino terminal groups of 9.7 × 10 ⁻⁵ equivalent / g and carboxy terminal groups of 2.0 × 10 ⁻⁵ equivalent / g were blended in a pellet form. The mixture is supplied to an extrusion molding machine (T-die extrusion molding machine, screw diameter is 40 mm) and melt-extruded at 250 ° C.
A film of a resin composition consisting of a polymer component of nylon and nylon 6 (A) is extruded and then cooled and solidified on a casting drum having a surface temperature of 70 ° C. to have a thickness of about 50.
A film of μ was formed. The following physical properties of this film were evaluated.

Regarding the gelling behavior during molding, the molding temperature should be 250
The conditions were set to be severe against ℃ and gelation, and the time until gel formation on the film was measured.

The results are shown in Table 1.

In the above-mentioned film formation, the resin composition used does not easily cause gelation, no gelation occurs even at 250 ° C. high temperature molding or 10 hours after molding, and the film obtained by the above film formation is The pinhole property was remarkably improved, and the gas barrier property was also good.

Example 2 Instead of nylon 6 (A), 6/66 copolymer (A) [molar ratio (6/66) of the structural units of nylon 6 and the structural unit of nylon 66 was 85/15, and the melting point was 195 ° C., relative viscosity 2.8, amino end groups 9.0 × 10 ⁻⁵ equivalent / g
Then, a film was formed in the same manner as in Example 1 except that 43 parts by weight of carboxy terminal group was 2.2 × 10 ⁻⁵ equivalent / g.

The results are shown in Table 1.

The obtained film was excellent in both gas barrier property and pinhole resistance, and gelation was not generated during film formation.

Example 3 A film was formed in the same manner as in Example 1 except that the amount of 6/66 copolymer (A) used in Example 2 was changed to 11 parts by weight.

Example 4 A film was formed in the same manner as in Example 1 except that the amount of the 6/66 copolymer (A) used in Example 2 was changed to 100 parts by weight.

These results are shown in Table 1 and are shown in Example 3 and Example 4.
Both were good results.

Example 5 As a polyamide, a 6/12 copolymer (A) [a molar ratio of a structural unit of nylon 6 and a structural unit of nylon 12 (6/1
2) is 80/20, melting point is 196 ° C., and relative viscosity is 2.
5, amino end groups are 10.5 × 10 ⁻⁵ equivalent / g and carboxy end groups are 2.1 × 10 ⁻⁵ equivalent / g] in the same manner as in Example 1 except that 43 parts by weight are used. , The film was formed.

The results are shown in Table 1.

The obtained film was excellent in both gas barrier property and pinhole resistance, and no gelled product was generated even after 10 hours from molding.

Comparative Example 1 A film was formed in the same manner as in Example 1 except that no polyamide was used.

The results are shown in Table 1.

The film obtained as described above has a good gas barrier property, but is poor in pinhole resistance because it is hard and has a small elongation.

Comparative Example 2 A polyamide having a relative viscosity of 2.9 and an amino end group of 4.
6 × 10 ^-5 equivalent / g, carboxy end group 5.3 × 10 ^-5
A film was formed in the same manner as in Example 1 except that 43 parts by weight of nylon 6 (B) having an equivalent weight / g was used.

Comparative Example 3 As polyamide, 6/66 copolymer (B) [nylon 6
Molar ratio of the structural unit of 6 to the structural unit of nylon 66 (6 /
66) is 85/15, the melting point is 195 ° C., and the relative viscosity is 2.
7, the amino terminal group was 6.8 × 10 ⁻⁵ equivalent / g and the carboxy terminal group was 5.4 × 10 ⁻⁵ equivalent / g] in the same manner as in Example 1 except that 43 parts by weight was used. A film was formed.

Comparative Example 4 As polyamide, 6/66 copolymer (C) [nylon 6
Molar ratio of the structural unit of 6 to the structural unit of nylon 66 (6 /
66) is 85/15, the melting point is 195 ° C., and the relative viscosity is 2.
6, the amino terminal group was 8.5 × 10 ⁻⁵ equivalent / g, and the carboxyl terminal group was 5.1 × 10 ⁻⁵ equivalent / g] in the same manner as in Example 1 except that 43 parts by weight was used. Was molded.

Comparative Example 5 As a polyamide, a 6/12 copolymer (B) [nylon 6
Molar ratio of the structural unit of 6 to that of nylon 12 (6 /
12) 80/20, melting point 196 ° C, relative viscosity 2.
6, amino terminal group was 6.7 × 10 ⁻⁵ equivalent / g, and carboxy terminal group was 3.1 × 10 ⁻⁵ equivalent / g] in the same manner as in Example 1 except that 43 parts by weight was used. Was molded.

These results are shown in Table 1, and Comparative Examples 2, 3, 4, 5
In both cases, gel was generated 1 to 2 hours after molding, and film formation became difficult when molding was continued.

Comparative Example 6 A film was formed in the same manner as in Example 1 except that the amount of the 6/66 copolymer (A) used in Example 2 was changed to 3 parts by weight.

The results are shown in Table 1. The film obtained as described above had almost no improvement in pinhole resistance.

Comparative Example 7 A film was formed in the same manner as in Example 1 except that the amount of the 6/66 copolymer (A) used in Example 2 was changed to 230 parts by weight.

The results are shown in Table 1, and the gas barrier properties of the film obtained as described above were significantly deteriorated.

Comparative Example 8 As a polyamide, a 6/66 copolymer (D) [nylon 6
Molar ratio of the structural unit of 6 to the structural unit of nylon 66 (6 /
66) is 85/15, the melting point is 195 ° C., and the relative viscosity is 2.
In the same manner as in Example 1, except that 43 parts by weight of amino terminal group was 2.2 × 10 ⁻⁵ equivalent / g and carboxy terminal group was 95 × 10 ⁻⁵ equivalent / g. However, gelling was remarkably generated during molding, and film formation became difficult.

Example 6 EVOH containing 38 mol% of repeating unit I based on an ethylene monomer, having a saponification degree of 99%, an intrinsic viscosity of 0.11, and a melting point of 173 ° C. was blended with 25% of glass fiber 100 parts by weight. Then, 43 parts by weight of 6/66 copolymer (A) was blended in the form of pellets. Using the mixture, a tensile test piece (ASTM D-638) and an Izod impact test piece (ASTM D-256) were molded by an injection molding machine at a cylinder temperature of 250 ° C. No gelation was observed even after injection molding for a long time. The test pieces molded as described above were measured according to the ASTM standard. The tensile break elongation was 16%, the Izod impact strength (notched) was 9.4 kg · cm / cm, and the impact resistance was improved. .

Comparative Example 9 A test piece was injection-molded in the same manner as in Example 6 except that no polyamide was used. The test piece was measured and found to have an elongation at break of 9% and an Izod impact strength (notched) of 6.8 kg · cm / cm.

Comparative Example 10 In the same manner as in Example 6, except that 43 parts by weight of 6/66 copolymer (B) used in Comparative Example 3 was used instead of 6/66 copolymer (A) of Example, a test was conducted. The pieces were injection molded. Molding 100
A gelled product started to be generated around a shot (about 1 hour after the start of molding), and when the molding was continued further, the molding became difficult because of the gelled product.

Claims (1)

[Claims] 1. A repeating unit (—CH 2) based on an ethylene monomer.
_2- CH ₂ —) in an amount of 5 to 50 mol%, and 100 parts by weight of a saponified product of a copolymer of ethylene and vinyl acetate having a saponification degree of 80% or more, and a relative viscosity of 2.1. ~ 3.
5, and the amino end group is 8 × 10 ⁻⁵ equivalent / g or more,
A resin composition of a saponified ethylene-based copolymer, which comprises 5 to 150 parts by weight of an amino-terminal rich terminal-modified polyamide having a carboxy terminal group of 3 × 10 ⁻⁵ equivalent / g or less.