JP2002012759A - Polyamide resin composition and film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition and a film for a polyamide film having excellent pinhole resistance, having a practically satisfactory level of optical characteristics, and capable of forming a stable film over a long period of time. I will provide a. SOLUTION: Polyamide resin 99.5 to 93% by weight
And a polyamide resin composition comprising 0.5 to 7% by weight of an ethylene / vinyl acetate copolymer having a vinyl acetate content of 20 to 50% by weight, wherein the ethylene / vinyl acetate copolymer has a saponification degree of 50 to 98%. It is partially saponified to mol% and does not contain a carboxyl group in the molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for a polyamide film which is excellent in pinhole resistance, has a practically satisfactory level of optical characteristics, and can be formed stably for a long period of time. And films.

[0002]

2. Description of the Related Art A film made of a polyamide resin is excellent in various physical properties such as gas barrier properties, toughness, pinhole resistance, heat resistance, optical properties and oil resistance. Therefore, it is used in various fields as a base material of a single-layer film or a laminated film, and as a constituent material of a multilayer film by co-extrusion with another resin, especially in the field of food packaging. However, regarding the pinhole resistance, which is regarded as the most important in practical use among the above characteristics, its temperature dependence is remarkable, and 5 ° C.
In use at low temperatures such as the following, leakage of the filler due to pinholes resulting from repeated bending fatigue,
Problems such as rotting of meat occur, and the use of chilled beef packaging and frozen food packaging is limited. As a method for improving this, a modified product of an ethylene copolymer (Japanese Patent Publication No. 7-15059) and an acid-modified product of a partially saponified ethylene-vinyl acetate copolymer (Japanese Patent Application Laid-Open No. 9-183900) are used. Addition has been proposed. These improve the pinhole resistance while maintaining the excellent transparency of the polyamide film,
Modified polyolefins having a carboxyl group in the molecule are added.

However, when a polyamide resin and a modified polyolefin having a carboxyl group in the molecule are mixed, a filter installed in a passage of a molten resin in an extruder is easily clogged at the time of film formation. However, there is a problem that the effect on productivity during film formation is enormous. Accordingly, an object of the present invention is to solve the above problems and to provide a polyamide resin composition and a film capable of forming a film stably for a long period of time and having excellent transparency and pinhole resistance.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a polyamide resin has a partially saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVA). When a specific amount is added and a film is formed, stable molding can be performed over a long period of time, and the obtained film retains optical characteristics at a level that is practically acceptable, and has a pinhole resistance at a low temperature. Was found to be improved.

That is, the present invention relates to a polyamide resin 99.5.
A polyamide resin composition comprising from 0.5 to 93% by weight and from 0.5 to 7% by weight of an ethylene / vinyl acetate copolymer having a vinyl acetate content of from 20 to 50% by weight, wherein the ethylene / vinyl acetate copolymer is saponified. The present invention relates to a polyamide resin composition which is partially saponified to a degree of 50 to 98 mol% and does not contain a carboxyl group in a molecule, and a polyamide film comprising the same.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The polyamide resin used in the present invention contains a lactam having three or more rings, a polymerizable ω-amino acid, a diamine and a dicarboxylic acid as main components. Examples of the lactam having three or more rings include ε-caprolactam, ω-enantholactam, ω-laurolactam, α-pyrrolidone, and the like. Examples of the polymerizable ω-amino acid include ω-aminocaproic acid, ω-aminoheptanoic acid, ω-aminononanoic acid, ω-aminooundodecanoic acid, ω-aminododecanoic acid, and the like.
As the diamine, for example, tetramethylene diamine,
Aliphatic such as hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4- / 2,4,4-trimethylhexamethylenediamine Amine, 1,3
Alicyclic diamines such as-/ 1,4-bis (aminomethyl) cyclohexane, isophoronediamine, piperazine, bis (4-aminocyclohexyl) methane, 2,2-bis- (4'-aminocyclohexyl) propane, and meta Aromatic diamines such as xylylenediamine and paraxylylenediamine can be mentioned. As the dicarboxylic acid, for example, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sepatinic acid, nonandioic acid, decanedioic acid, undecandioic acid, aliphatic dicarboxylic acid such as dodecanedioic acid, hexahydroterephthalic acid, Alicyclic carboxylic acids such as hexahydroisophthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid (1,2-form, 1,3-form 1,4-form, 1,
5-body, 1,6-body, 1,7-body, 1,8-body, 2,3
-, 2,6- and 2,7-) aromatic dicarboxylic acids.

In the present invention, homopolymers or copolymers derived therefrom can be used alone or in the form of a mixture. Specific examples of the polyamide resin include nylon 4, 6, 7, 11, 12, 46, 66, 6
9, 610, 611, 612, 6T, 6I, MXD6,
6/66, 6/610, 6/611, 6/12, 6/6
12,6 / 6T, 6 / 6I, 6/66 / 610,6 / 6
6/12, 6/66/612, 66 / 6T, 66/6
I, 6T / 6I, 66 / 6T / 6I, and the like.
Preferred polyamide resins include nylon 6, nylon 12, and nylon 6 in consideration of heat resistance, mechanical strength, transparency, economy, availability, and the like of the obtained film.
6, MXD6, nylon 6/66 copolymer, nylon 6
/ 12/12 copolymer, nylon 6/66/12 terpolymer and the like.

The ethylene / vinyl acetate copolymer of the present invention has a vinyl acetate content of 20 to 50% by weight, is partially saponified to a saponification degree of 50 to 98 mol%, and does not contain a carboxyl group in the molecule. Things. This partially saponified ethylene-vinyl acetate copolymer (hereinafter referred to as HEV
A) can be obtained by the following method.

EVA as a raw material for producing HEVA
Is produced by a known production method such as a high-pressure method or an emulsification method, and one having a vinyl acetate content of 20 to 50% by weight is usually used, and preferably 30 to 45% by weight. When the vinyl acetate content is low, the crystallinity of polyethylene cannot be suppressed, and the transparency is not improved. On the other hand, when the vinyl acetate content is increased, the vinyl acetate is softened and the effect of improving pinhole resistance is obtained, but the production becomes difficult in the saponification step.

A method of treating EVA with a known saponification method, for example, a system comprising a low-boiling alcohol such as methanol or ethanol and an alkali such as sodium hydroxide, potassium hydroxide or sodium methylate, having a saponification degree of 50 to 9
By saponifying to 8 mol%, preferably 60 to 98 mol%, a partially saponified EVA (HEVA) can be obtained. If the saponification degree is low, the compatibility with the polyamide resin is not improved, and the transparency is not improved. On the other hand, when the degree of saponification is 99 mol% or more, the crystallinity becomes high and flexibility cannot be obtained.

HE added to polyamide in the present invention
VA melt index is 0.1g / 10min ~ 40g / 1
It is preferably 1 g / 10 min to 25 g / 10 min in view of the dispersibility at the time of mixing with polyamide for 0 minute.

The HEVA used in the present invention must be free of carboxyl groups in the molecule. When a resin having a carboxyl group introduced into a molecule by acid modification or the like is mixed with a polyamide resin, a filter provided in a melt line in an extruder is likely to be clogged during film formation. On the other hand, when a polyamide film is obtained by mixing EVA itself with a polyamide resin, only a film having poor transparency is obtained, but there is a problem in practicality because the film has poor pinhole resistance.

The mixing ratio of the polyamide resin of the present invention and HEVA is such that the ratio of HEVA to polyamide resin is 0.5 to 0.5.
It is 7% by weight, preferably 1 to 5% by weight. When the amount is less than 0.5% by weight, the pinhole resistance is hardly improved. On the other hand, if it exceeds 7% by weight, the transparency deteriorates.

When HEVA is added to a polyamide resin,
The transparency can be further improved by adding a compatibilizer such as an ionomer within a range that does not impair the molding long-run property. In order to further improve pinhole resistance, known elastomers such as polyamide elastomers, ethylene-α-olefin copolymers, unsaturated carboxylic acid alkyl ester and ethylene copolymers, styrene elastomers, etc., are used as transparent, molded long run. Can be added in a range that does not impair the properties.

As a method for mixing the polyamide resin with the polyamide resin, a method of mixing the polyamide resin and HEVA by dry blending can be applied. Alternatively, a method of blending a polyamide resin and HEVA, followed by melt-kneading with an extruder to obtain a pellet of a molten mixture can also be applied.

As a method for producing a film comprising the resin composition of the present invention, a known production method can be applied. Specifically, the resin composition is melt-kneaded with an extruder,
A casting method in which the film is extruded into a flat film by a T-die or a coat hanger die and then cast on a casting roll surface to cool the film, or a tuber method in which a product extruded in a cylindrical shape by a ring-shaped die is water-cooled is applied. Is done.

It is also applicable to stretch a film manufactured in a flat shape or a tuber shape continuously or in another step. For example, in the case of the sequential biaxial stretching method,
The flat unstretched film is stretched 2 to 4 times by a roll type longitudinal stretching machine, and then stretched 2 to 4 by a tenter type transverse stretching machine.
After the film is stretched 5 times and the obtained biaxially stretched film is heat-treated as desired, it can be manufactured by continuously winding the film while gradually cooling the film. The thickness of the biaxially stretched film thus obtained is 3 to 40 µ, preferably 5 to 25 µ.

The pinhole resistance referred to in the present invention has a thickness dependency, and becomes worse as the film becomes thicker. When the thickness of the film exceeds 40 μm, the addition of the HEVA cannot improve the pinhole resistance. On the other hand, if the thickness is smaller than 3 μm, the function as a strength retaining material, which is a characteristic of a polyamide film, cannot be obtained.

The biaxially stretched polyamide film can be produced by other methods such as a tenter simultaneous biaxial stretching method and a tuber stretching method in addition to the tenter sequential biaxial stretching method described above.

Further, the film comprising the polyamide resin composition of the present invention may be formed into a laminate with another polymer film. Other polymer films include polyethylene, polypropylene, ethylene-vinyl acetate copolymer or saponified product thereof, ethylene-unsaturated carboxylic acid copolymer, ethylene-acrylate copolymer, ionomer, ethylene-α-olefin copolymer. Examples include an olefin film such as a coalesced film and a modified polyolefin film obtained by graft-modifying the above with an unsaturated carboxylic acid or a derivative thereof.

The method of forming the polyamide film into a laminate is not particularly limited. For example, a method of bonding a polyamide film and one or more other polymer films with an adhesive, or a method of bonding a polyamide resin and one or two A method of melt-coextrusion of a polymer compound constituting at least one kind of another polymer film from a multilayer die via an adhesive resin can be applied.

The polyamide resin composition of the present invention may contain other additives according to the required properties, for example, a heat-resistant agent, a weathering agent including an ultraviolet absorber, a flame retardant, an antistatic agent, a lubricant, a nucleating agent,
It can contain a plasticizer, a foaming agent, a coloring agent, a stabilizer, a coupling agent and the like.

[0023]

The present invention will be described more specifically below with reference to examples and comparative examples. Note that the present invention is not limited to the following embodiments. The methods for measuring or evaluating physical properties in the following examples are as follows. <Molding stability> The resin composition was supplied to a single-screw extruder equipped with a T-die to form a film. The filter differential pressure was measured over time during molding, and the point at which the increase was remarkably determined was judged to be the filter clogged. The molding stability was determined when no increase in the differential pressure was observed within the test time of 8 hours. It was judged to be good. In order to quickly determine the state of clogging of the filter, a filter having a fine mesh size was used, and the extrusion temperature was set to be 20 ° C. higher than usual in order to promote thermal deterioration and the like. The extrusion conditions are shown below. Screw inner diameter: 30 mm L / D: 28 Screw compression ratio: 3.2 T die: coat hanger type Die width: 300 mm Screw rotation speed: 40 rpm Filter mesh: 80/125/125/80/500/500/500/80 / 125/125/80 Extrusion temperature C1 C2 C3 AD D Set temperature 160 ° C. 240 ° C. 280 ° C. 280 ° C. 280 ° C. <Transparency> AS is measured by a direct read haze meter manufactured by Suga Test Machine.
The haze value (haze ratio) of the film was measured according to TMD-1003. And when the value was 5 or less, it was judged that there was a transparency improving effect. <Pinhole resistance> -20 ° C according to MIL-B-131C using a gelbo flex tester with a thermostat manufactured by Rigaku Kogyo.
After performing the bending test 200 times below, the number of pinholes generated in the film was measured using a pinhole detector manufactured by Sanko Electronics. When the value was 5 or less, it was determined that the pinhole resistance was improved.

The polyamide and the ethylene / vinyl acetate copolymer used in the embodiment are as follows. Polyamide resin (1): UBE Nylon 1022B ethylene-vinyl acetate copolymer HEVA (1): Dumilan XD-159, manufactured by Takeda Pharmaceutical Co., Ltd., saponification degree 90 mol%, MI 23 g / 10 min Ethylene -Vinyl acetate copolymer HEVA (2): Mersen H-6051, manufactured by Tosoh Corporation, saponification degree 98 mol%, MI 5.5 g / 10 min, ethylene / vinyl acetate copolymer HEVA (3): Tosoh ( Mersen H-7551, saponification degree 80 mol%, MI 5.5 g / 10 min Ethylene / vinyl acetate copolymer HEVA-C
(4): Dumilan C-1591 manufactured by Takeda Pharmaceutical Co., Ltd., saponification degree 90 mol%, acid modification rate 2.0 wt%, MI 8.0
g / 10 minutes Ethylene / vinyl acetate copolymer HEVA (5): Mersen H-6251, manufactured by Tosoh Corporation, saponification degree 20 mol%, MI 5.0 g / 10 minutes Ethylene / vinyl acetate copolymer EVA ( 6): Ultrasone 751, manufactured by Tosoh Corporation, vinyl acetate content 28
%, Saponification degree 0%, MI 6.0 g / 10 min. In Table 1, the meanings of the abbreviations of the resins are as follows. PA: Polyamide resin EVA: Ethylene / vinyl acetate copolymer HEVA: Ethylene / vinyl acetate copolymer partially saponified HEVA-C: Ethylene / vinyl acetate copolymer partially saponified

Example 1 95% by weight of polyamide 6 resin (1) and HEVA (1) 5
Using a resin composition obtained by melt-kneading the resin composition in an amount of 1% by weight, the molding stability was evaluated in accordance with the above evaluation method. Further, a biaxially stretched film was produced using the following molding machine and molding conditions, and physical properties were evaluated in accordance with the above evaluation methods. Table 1 shows the evaluation results. Raw material molding 1) Molding machine: 40mmφEx, T-die film molding machine manufactured by Plastics Engineering Laboratory 2) Film thickness: 100μ 3) Molding condition C1 C2 C3 C4 ADD Set temperature 200 ° C 230 ° C 250 ° C 250 ° C 250 ° C 250 ° C 4) Roll temperature: 30 ° C Biaxial stretching 1) Molding machine: Biaxial stretching machine manufactured by Iwamoto Seisakusho 2) Stretching ratio: Simultaneous stretching, 2.6 times long, 2.6 times wide, total 6.8 times 3) Stretching temperature: 80 ° C Film thickness: 15μ

Example 2 Using a resin composition obtained by melt-kneading 95% by weight of polyamide resin (1) and 5% by weight of HEVA (2), evaluation of molding stability and film properties was performed according to the method of Example 1. went. Table 1 shows the evaluation results.

Example 3 Using a resin composition obtained by melt-kneading 95% by weight of polyamide resin (1) and 5% by weight of HEVA (3), evaluation of molding stability and film properties was carried out according to the method of Example 1. went. Table 1 shows the evaluation results.

Example 4 Using a resin composition obtained by melt-kneading 98% by weight of polyamide resin (1) and 2% by weight of HEVA (3), evaluation of molding stability and film properties was carried out in accordance with the method of Example 1. went. Table 1 shows the evaluation results.

Comparative Example 1 95% by weight of polyamide resin (1) and HEVA-C (4)
The molding stability and film properties were evaluated in accordance with the method of Example 1 using a resin composition obtained by melt-kneading 5% by weight. Table 1 shows the evaluation results.

Comparative Example 2 Using a resin composition obtained by melt-kneading 95% by weight of polyamide resin (1) and 5% by weight of HEVA (5), evaluation of molding stability and film properties was carried out according to the method of Example 1. went. Table 1 shows the evaluation results.

Comparative Example 3 Using a resin composition obtained by melt-kneading 95% by weight of polyamide resin (1) and 5% by weight of EVA (6), evaluation of molding stability and physical properties of a film was carried out according to the method of Example 1. went. Table 1 shows the evaluation results.

Comparative Example 4 90% by weight of polyamide resin (1) and HEVA (1) 10
Example 1 using a resin composition obtained by melt-kneading
According to the method described above, evaluation of molding stability and film physical properties was performed. Table 1 shows the evaluation results.

Comparative Example 5 The molding stability and film properties were evaluated in accordance with the method of Example 1 using only the polyamide resin (1). Table 1 shows the evaluation results.

[0034]

[Table 1]

[0035]

According to the present invention, by adding a partial saponified product of a specific ethylene / vinyl acetate copolymer to a polyamide resin, the pinhole resistance at low temperatures can be maintained while maintaining a level of transparency which is practically no problem. Can be improved. In addition, a stable operation for a long time can be achieved in the production of these, and the industrial use value is extremely large.

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Claims (2)

[Claims] (1) 99.5 to 93% by weight of a polyamide resin,
A polyamide resin composition comprising 0.5 to 7% by weight of an ethylene / vinyl acetate copolymer having a vinyl acetate content of 20 to 50% by weight, wherein the ethylene / vinyl acetate copolymer has a saponification degree of 50 to 98% by mole. A polyamide resin composition characterized in that it is partially saponified and does not contain a carboxyl group in the molecule. 2. A polyamide film comprising the polyamide resin composition according to claim 1.