JP2003213123A - Polyamide resin composition and film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare a film excellent in gas barrier properties, pinhole resistance and transparency, with little occurrence of fish eyes. <P>SOLUTION: A composition, in an amount of 100 pts.wt., containing a polyamide resin (a) in an amount of 90-99.5 pts.wt. and an ethylene/vinyl acetate copolymer (b) having a vinyl acetate content of 5-50 wt.% and a degree of saponification of 97-100 mol%, in an amount of 0.5-10 pts.wt. is mixed with a hindered phenol compound (c) in an amount of 0.001-3 pts.wt. to give a polyamide resin composition. The film is obtained from the composition. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyamide resin composition and a film comprising the same. More specifically, the present invention relates to a polyamide resin composition which is excellent in pinhole resistance and transparency, and is suitable as a material for a film having less fish eyes, and a film comprising the composition.

[0002]

2. Description of the Related Art Polyamide resin has the strength, flexibility,
It has excellent properties such as transparency, heat resistance, and chemical resistance. Above all, it has a good gas barrier property, so it is widely used for packaging materials such as food packaging, medical packaging, agricultural chemicals, reagent bottles and containers. It is used. Specifically, due to the excellent oxygen barrier property of the polyamide resin, it is characterized in that it is often used for containing so-called liquid substances such as raw meat, konjac, pickles and medical infusions as its contents. Thus, the oxygen barrier property of the film is exhibited only when the film is uniform and has no defects such as pinholes. Actually, after filling the contents of a packaging material using such a film with high temperature and high humidity treatment to prevent food poisoning and foreign substances these days, seal the mouth and squeeze with wire etc. When packing and transporting in a box or plastic container, if an external force that repeatedly makes a crease is applied to the film, a pinhole will be generated in the repeatedly crease part of the film, and the contents will leak out from the pinhole or from that pinhole. Oxygen may enter and cause oxidative deterioration of the contents. In particular, due to the recent advances in freezing technology and the product reliability of contents due to the enforcement of the PL Law, foods such as raw meat are 0
Transportation at a temperature around ℃, a so-called chilled state, is increasing. However, in the conventional polyamide film, the pinhole resistance has a large temperature dependency, so that it is difficult to maintain the practical pinhole resistance especially at a low temperature such as 0 ° C.

For applications that require more gas barrier properties, an ethylene vinyl alcohol copolymer resin (hereinafter abbreviated as EVOH) or an aromatic polyamide resin may be blended or laminated as an oxygen barrier (Japanese Patent Publication No. 44-44). 242
77, JP-B-48-22833, JP-A-50-1213.
47 etc.), it has been proposed to laminate a polyester resin as an odor barrier. However, these resins generally have good gas barrier properties but poor toughness, and pinholes are easily generated. There was a tendency that the pinhole resistance in the above was required.

In order to improve the pinhole resistance, a method of adding an unsaturated carboxylic acid-modified polyolefin resin has been tried in the past. As a method for improving the pinhole resistance, Japanese Patent Publication No. 7-15059, Kaihei 6-13615
7, JP-A-9-183900 are known. However, since these methods all use a polyolefin resin modified with an unsaturated carboxylic acid, while the polyamide film obtained by these methods has improved pinhole resistance, during long-time molding, It was a situation in which fisheyes were likely to occur and a stable, high-quality film could not be formed, and neither pinhole resistance nor transparency was sufficient.

DISCLOSURE OF THE INVENTION The present invention provides a polyamide resin composition which is excellent in pinhole resistance and transparency and which is suitable for producing a film having less generation of fish eyes, and a film comprising the composition. With the goal.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above object, and as a result, a polyamide resin composition containing a specific component is excellent in pinhole resistance and transparency. Moreover, they have found that the occurrence of fish eyes is reduced and have reached the present invention. That is, the gist of the present invention is that the content of vinyl acetate is 5 to 50% by weight and the degree of saponification is 9 to 90 to 99.5 parts by weight of the polyamide resin (a).
To 100 parts by weight of a composition containing 0.5 to 10 parts by weight of an ethylene / vinyl acetate copolymer (b) of 7 to 100 mol%, 0.001 of a hindered phenolic compound (c) is added.
˜3 parts by weight of the polyamide resin composition. The present invention also resides in films and laminated films comprising such polyamide resin composition.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. As the polyamide resin (a) in the present invention, 3
A lactam having a member ring or more, a polymerizable ω-amino acid, or a polyamide obtained by polycondensation of a dibasic acid and a diamine can be used. Specifically, ε-caprolactam, aminocaproic acid, enanthlactam,
7-aminoheptanoic acid, 11-aminoundecanoic acid, 9
-Aminononanoic acid, polymers such as α-pyrrolidone and α-piperidone, diamines such as hexamethylenediamine, nonamethylenediamine, undecamethylenediamine, dodecamethylenediamine, metaxylylenediamine and terephthalic acid, isophthalic acid, adipic acid, sebacic acid ,
Polymers obtained by polycondensation with dicarboxylic acids such as dodecane dibasic acid and glutaric acid, or copolymers thereof, such as nylon 4, 6, 7, 8, 11, 12, 6
6, 69, 610, 611, 612, 6T, 6/66,
6/12, 6 / 6T, 6T / 6I, MXD6 and the like can be mentioned, and plural kinds of polyamide resins can also be used. Preferred is a polymer of ε-caprolactam (polyamide 6), a copolymer of polyamide 6 and hexamethylenediamine adipamide (polyamide 6/66), or a mixture thereof.

The end of the polyamide resin in the present invention is
It may be encapsulated with a carboxylic acid or amine, and a polyamide resin encapsulated with a carboxylic acid or amine having 6 to 22 carbon atoms is particularly desirable. Specific examples of the carboxylic acid used for sealing include aliphatic monocarboxylic acids such as caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid. Examples of amines include aliphatic primary amines such as hexylamine, octylamine, decylamine, laurylamine, myristylamine, palmitylamine, stearylamine, and behenylamine. The amount of carboxylic acid or amine used for sealing is 30 μe
It is preferably about q / g, but it is preferable to use a polyamide resin in which the terminal amino groups of the polyamide are blocked with only a carboxylic acid because the thermal stability is improved and the effect of the present invention becomes more remarkable.

The polyamide resin suitable for the present invention preferably has a degree of polymerization within a certain range, that is, a relative viscosity. A preferable relative viscosity is 2 to 6.5, more preferably 2.5 to 5.5, as measured by a resin concentration of 1% in 98% sulfuric acid and a temperature of 25 ° C. according to JIS K6810. When the relative viscosity is lower than 2, the melt viscosity is small and molding becomes difficult, and the pinhole resistance is also lowered.
Further, even if the relative viscosity is higher than 6.5, the melt fluidity is impaired, which is not preferable.

The ethylene / vinyl acetate copolymer (EVA) (b) in the present invention is produced by a known production method such as a high pressure method or an emulsification method and has a vinyl acetate content of 5 to 50% by weight. Is used. The vinyl acetate content is preferably 15-45% by weight. When the vinyl acetate content is less than 5% by weight, when saponified, the compatibility with the polyamide resin is poor and the pinhole resistance and the transparency are deteriorated. On the other hand, when the content of vinyl acetate exceeds 50% by weight, not only the effect of improving the pinhole resistance due to excessive hardness when saponified but also the reaction with the polyamide resin excessively causes fish eyes due to gel, which is preferable. Absent. A known method is used for the saponification method of EVA. For example, low boiling alcohols such as methanol and ethanol and sodium hydroxide,
A saponification product of EVA having a saponification degree of 97% mol or more can be obtained by a method of treating with an alkali system such as potassium hydroxide or sodium methylate. The degree of saponification is more preferably 100 mol%. When the saponification degree is less than 97%, the compatibility with the polyamide resin is poor and the effect of improving the pinhole resistance and the transparency is not sufficient, which is not preferable.

The ethylene / vinyl alcohol copolymer (EVOH) usually has a vinyl acetate content of 50 mol%.
It is a resin that completely saponifies EVA exceeding 99 mol% or more and is a resin that is hard and has an excellent gas barrier property. However, the saponified EVA of the present invention improves flexibility and improves pinhole resistance. Used for purposes. The amount of the saponified EVA (b) used in the present invention is 90 to 9 for the polyamide resin (a).
The ratio is 0.5 to 10 parts by weight, and more preferably 1 to 8 parts by weight, based on 9.5 parts by weight. The amount of (b) added is
If it is less than 0.5 parts by weight, the effect of improving the pinhole resistance is poor, and if it exceeds 10 parts by weight, haze is deteriorated, which is not preferable.

The hindered phenolic compound (c) in the present invention is generally used as an antioxidant and a processing stabilizer, and 3,5-dialkyl-4-in the molecule.
Hydroxyphenyl or 2,4-dialkyl-1-
It is a compound having a hydroxyphenyl structure, and its hydroxy group may be esterified with an acid such as phosphorous acid. Furthermore, the alkyl-substituted phenol structure may be present at one or more sites in the molecule. Particularly preferred is a compound having a 3,5-dialkyl-4-hydroxyphenyl structure in the molecule. Specific hindered phenols include triethylene glycol-bis [3-
(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], penta Erythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxyhydrocin) Namamide), 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, octadecyl-3- (3,5-di-t-butyl-4)
-Hydroxyphenyl) propionate, 1,3,5-
Trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, 2,4-bis- (n-octylthio) -6- (4-hydroxy-
3,5-di-t-butylanilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5
-Di-t-butyl-4-hydroxyphenyl) propionate] and the like, and these may be used alone or in combination with 2
Combinations of more than one species can be used. Particularly preferred hindered phenol compounds are N, N'-hexamethylene bis (3,5-di-t-butyl-4-hydroxyhydrocinnamamide), pentaerythrityl-tetrakis [3- (3,5-di). -T-butyl-4-hydroxyphenyl) propionate].

The addition amount of the hindered phenolic compound (c) is 0.001 with respect to 100 parts by weight of (a) + (b).
To 3 parts by weight, preferably 0.01 to 1 part by weight,
It is more preferably 0.01 to 0.5 parts by weight. Addition amount is 0.
When the amount is less than 001 parts by weight, the addition effect is not obtained, and when the amount is more than 3 parts by weight, the amount of bleed-out on the surface is large when formed into a film, the printing and laminating suitability is deteriorated, and peeling easily occurs when forming a laminated film. Not preferable.

The polyamide resin (a) has a saponified EV
The method for producing the composition of the present invention by adding A (b) and the hindered phenol (c) is not particularly limited, and a method of adding (b) and (c) in the polymerization process of the polyamide resin. , A method of dry blending with a polyamide resin after polymerization, a method of melt-kneading with a polyamide resin, a method of preparing a high-concentration masterbatch, and diluting and using this at the time of molding, according to any known addition method You can In particular, saponified EVA (b)
As a method for adding the polyamide resin (a) to the polyamide resin (a), a method of preparing a masterbatch in which the polyamide resin (a) and the saponified EVA (b) are melt-mixed in advance and adding the master batch to the polyamide resin (a) It is preferable from the viewpoint of reducing. At this time, it is more preferable to set the melt viscosity of the masterbatch to be lower than that of the polyamide resin from the viewpoint of reducing fish eyes.

Further, the polyamide resin composition containing (a), (b) and (c) is a lubricant, a mold release agent, a heat deterioration preventing agent and an ultraviolet absorber within a range not impairing the effects of the present invention. Further, additives such as antistatic agents, antiblocking agents, dyes, pigments, inorganic particles, flame retardants and the like may be blended and used. For example, the polyamide resin composition of the present invention may contain a bisamide compound to improve the slipperiness of the film. Specific examples of the bisamide compound include N, N′-methylenebisstearylamide and N, N′-ethylenebisstearylamide. The addition amount of bisamide compound is polyamide resin 1
0.01 to 1 part by weight is preferable with respect to 00 parts by weight,
It is more preferably 0.01 to 0.3 parts by weight.

Further, it is preferable to use a polyamide resin containing 0.01 to 1 part by weight of silica or kaolin surface-treated with a silane coupling agent or the like because the slipperiness is improved. These additives are added in the process of polymerizing the polyamide resin, dry-blended with the polyamide resin after polymerization, melt-kneaded with the polyamide resin, or made into a high-concentration masterbatch, which is diluted during molding. Can be used according to any known addition method.

The method for forming a film using the polyamide resin composition of the present invention is not particularly limited, and various known methods can be adopted. Examples thereof include extrusion sheet molding, extrusion T-die film molding, extrusion inflation film molding and the like. The film using the polyamide resin composition of the present invention may be used as a monolayer film, or may be laminated with another resin in order to further improve the gas barrier property and the like. As the other resin used for forming the laminated film, at least one selected from ethylene / vinyl alcohol copolymer resin (EVOH), aromatic polyamide resin and polyester resin is preferable.

The EVOH may be a general EVOH and is not particularly limited, but considering that it is used for the purpose of improving the gas barrier property, the ethylene portion is 50% by weight or less and the saponification degree is 98 mol% or more. Those are preferable. The aromatic polyamide resin is not particularly limited, but may be MXD6, which is a polymer of an aromatic diamine such as metaxylylenediamine and adipic acid, or a polycondensate 6T of hexamethylenediamine and terephthalic acid and hexamethylenediamine. Copolymer with isophthalic acid polycondensate 6I (6
T / 6I) is more preferable from the viewpoint of gas barrier property. The polyester resin is not particularly limited, but polyethylene terephthalate and polybutylene terephthalate are more preferable in terms of moldability.

A laminated film using the polyamide resin composition of the present invention can be manufactured by a known method.
Examples thereof include so-called co-extrusion methods such as co-extrusion sheet molding, co-extrusion T-die film molding, and co-extrusion inflation film molding, or a method of obtaining a single layer film and then laminating it with another film by a lamination method. The co-extrusion method will be described in more detail. The polyamide resin composition of the present invention and the laminated resin raw material are melted by different extruders and continuously melted.
-Multi-layer T-die method of extruding from a die, adhering inside and outside the die, and forming into a film while cooling with a casting roll, continuously extruding from an annular die,
A multi-layer water cooling inflation method in which water is contacted and cooled,
Similarly, a multilayer air-cooling inflation method in which the material is extruded from an annular die and cooled by air can be used.

It is also possible to stretch a film-shaped molded article in a later step, and as this method, a method known in industry can be applied. For example, with respect to a film formed by the T-die method, the longitudinal stretching is performed by a roll method, and when the film is stretched in the transverse direction, a tenter method is used sequentially.
In addition to the above-mentioned sequential biaxial method, a tubular stretching method capable of simultaneous longitudinal and transverse stretching is used for the axial stretching method and the tubular film formed from the annular die. In the laboratory, a stretched film can be obtained by using a desktop stretching machine (for example, manufactured by TM Long Co. or Toyo Seiki Seisakusho Co., Ltd.).

The thickness of the film using the polyamide resin composition of the present invention is not particularly limited, but if it is thick, the gas barrier property is improved, but the transparency is lowered,
If it is too thin, the original strength of the polyamide resin will decrease. In view of this point, the thickness of the polyamide resin layer is preferably 2 to 100 μm for the unstretched film and 2 to 50 μm for the stretched film, and the thickness of the laminated film is preferably about 10 to 300 μm. Also,
The film of the present invention can be used after corona treatment on one side or both sides for improving printability and laminating property.

[0021]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The physical properties were evaluated by the following methods.

(1) A pinhole-resistant film was machined in the machine direction (longitudinal direction) 280 mm × Transverse Dir.
Section direction (horizontal direction) is cut to 160 mm, fixed to a stainless steel jig, put in an autoclave SR-240 for retort food manufactured by Tommy Seiko Co., Ltd., and steam-type / aerated treatment is performed at 130 ° C. for 30 minutes. . Specifically, first, the air in the retort kettle is discharged while the temperature is raised to 100 ° C., then the exhaust valve is closed and the temperature rise / pressurization is continued. When the temperature reaches 130 ° C., air pressure is applied to adjust the internal pressure to 0.21 MPa and hold for 30 minutes. Then the internal pressure is 0.24 MPa
Pressurize until it reaches 70 ° C and introduce cooling water into the retort kettle.
Cooled down. Remove the film after cooling from the jig, 2
The humidity was controlled at 3 ° C. and 65% RH for 4 days or more. The sterilized film was subjected to flex fatigue 1000 times repeatedly at 0 ° C. by a method conforming to MIL-B-131C using a gelbo flex tester manufactured by Rigaku Kogyo Co., Ltd., and then pinholes formed in the film. I counted the number. The value in this test is preferably 0.

(2) Transparency The haze value was evaluated using a haze meter manufactured by Tokyo Denshoku Co., Ltd. The value of this test is preferably 5 or less for practical use. (3) Fish eye evaluation method The film was cut into 300 mm × 300 mm square, and 40
The number of fish eyes having a size of μm or more was counted and evaluated with the naked eye. The number of fish eyes in this test is preferably 10 or less.

(4) Materials used in Examples and Comparative Examples Polyamide resin A: 6 nylon manufactured by Mitsubishi Engineering Plastics, grade name 1020J, relative viscosity:
3.5. Saponified EVA: Tosoh Corporation, trade name Mersen H60
51, vinyl acetate content 42% or less, saponification degree 100%. Modified PO: unsaturated carboxylic acid-modified ethylene / butene copolymer manufactured by Mitsui Chemicals, Inc., grade name MH5010. Hindered phenolic compound: N, N'-hexamethylenebis (3,3, manufactured by Ciba Specialty Chemicals Co., Ltd.
5-di-t-butyl-4-hydroxyhydrocinnamamide), trade name Irganox 1098. EVOH: ethylene-vinyl alcohol copolymer resin manufactured by Nippon Gohsei Co., Ltd., trade name Soarnol DC3203.

Examples 1 and 2 and Comparative Examples 1 to 6 The components shown in Table 1 were blended in the amount ratios shown in Table 1 and the cylinder set temperature was 250 ° C. with TEX-30HCT manufactured by Japan Steel Works. Melt kneading, pelletizing, and this is 100 ℃
Was dried in a vacuum dryer of No. 1 to obtain a polyamide resin composition.
This polyamide resin composition was melted at a cylinder setting temperature of 250 ° C. and a screw rotation speed of 50 rpm with a single-layer T-die molding machine manufactured by Ikegai Tekko Co., Ltd., while cooling with a casting roll to 30 ° C., 1.5-2. The take-up speed is 0m / min and the thickness is 30μm and 135μ
m monolayer film was formed. The 30 μm-thick monolayer film was directly evaluated for pinhole resistance, fish eye, and transparency, and the 135 μm-thick monolayer film was heated with a tabletop stretching machine (TMLong Co.) to obtain a residual heat temperature of 9 before stretching.
Simultaneously biaxially stretch at 0 ° C. and a draw ratio of 3.0 × 3.0 times, and then heat set at 210 ° C. for 30 seconds to obtain a thickness of 1
A film having a thickness of 5 μm was obtained and evaluated for pinhole resistance, fish eye and transparency. The results are shown in Table-1.

Example 3 and Comparative Examples 7 to 9 The components shown in Table-2 were blended in the ratios shown in Table-2, and melt-kneaded at a cylinder setting temperature of 250 ° C. with TEX-30HCT manufactured by Japan Steel Works. , Pelletize this at 100 ℃
It was dried by a vacuum dryer to obtain a polyamide resin compound.
Using the polyamide resin composition and EVOH, in a Placo 4-kind 7-layer multi-layer T-die molding machine, the polyamide resin composition is extruded with a cylinder diameter of 32 mm and screw rotation speed is 20 rpm, cylinder temperature is 240 ° C., EV
OH was melted separately with an extruder having a cylinder diameter of 25 mmφ at a screw rotation speed of 40 rpm and a cylinder temperature of 220 ° C., and three layers of polyamide resin composition / EVOH / polyamide resin composition were prepared in a die having a die lip clearance of 4.0 mm. After merging and adhering in a shape, while cooling to 30 ° C with a casting roll, 4.0 m / min
Is taken up at a take-up speed of, and the layer constitution is polyamide resin composition / EVOH / polyamide resin composition = 45 /
A 45/45 μm trilayer film was formed. This three-layer film was simultaneously biaxially stretched using a table-top stretching machine (manufactured by TM Long Co.) at a residual heat temperature of 90 ° C. before stretching and a stretching ratio of 3.0 × 3.0 times, and then 210 ° C., 30 Heat set for seconds and the thickness of each layer is polyamide resin composition / EVO
A three-layer film of H / polyamide resin composition = 5/5/5 μm was obtained, and the pinhole resistance, fish eye, and transparency were evaluated. The results are shown in Table-2.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

As is clear from Table 1 and Table 2, the film obtained from the polyamide resin composition of the present invention is
In either case of a single-layer film or a laminated film, it has excellent pinhole resistance and transparency, less generation of fish eyes, and the range of applications of polyamide films, which has been limited so far, can be greatly expanded.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 23:26) (72) Inventor Seiji Morimoto 5-6-2 Higashi-Hachiman, Hiratsuka-shi, Kanagawa Sanryo Engineering (72) Inventor Morio Tsunoda 5-6-2 Higashi-Hachiman, Hiratsuka-shi, Kanagawa Sanryo Engineering Plastics Co., Ltd. Technical Center F-term (reference) 4F071 AA15 AA29 AA54 AA55 AC11 AE05 AF07 AF26 AF30 AF53 AH04 BC01 4F100 AK22A AK41B AK46A AK47B AK48A AK69A AK69B AL05A BA02 CA06A GB15 JD02 JK14 JN01 4J002 BB222 BE032 CL001 CL011 CL031 CL051 EJ016 EJ036 FD036 GF00GG00

Claims (4)

[Claims] 1. A vinyl acetate content of 5 to 50% by weight based on 90 to 99.5 parts by weight of a polyamide resin (a), and
Composition 100 containing 0.5 to 10 parts by weight of an ethylene / vinyl acetate copolymer (b) having a saponification degree of 97 to 100 mol%
In parts by weight, 0.0 of hindered phenolic compound (c)
A polyamide resin composition containing 0 to 1 part by weight. 2. The polyamide resin composition according to claim 1, wherein the polyamide resin (a) is selected from the group consisting of polyamide 6, polyamide 6/66, and a mixture thereof. 3. A film comprising the polyamide resin composition according to claim 1. 4. The film according to claim 3, wherein an ethylene / vinyl alcohol copolymer, an aromatic polyamide resin,
A laminated film obtained by laminating at least one resin selected from polyester resins.