JP2002080717A - Polyamide resin composition for film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain both a polyamide resin composition for a film having excellent heat stability and oxidation stability and slight reduction in practical properties even if subjected to a retort treatment and a polyamide film for food packaging, especially suitably useful as a film for a retort packaging. SOLUTION: This polyamide resin composition for a film comprises (A) 100 pts.wt. of a polyamide resin and (B) 0.01-1.0 pt.wt. of a hydroxyphenylpropionic acid ester represented by general formula (1) (R1 is a 1-3C alkyl group).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide composition for films containing a specific amount of a specific antioxidant and a polyamide film for food packaging. Specifically, it has excellent thermal stability and oxidation stability, and even after retort treatment,
The present invention relates to a polyamide resin composition for a film having good mechanical properties, particularly practical properties such as high tensile strength retention, and a polyamide film for food packaging, particularly a polyamide film suitably used as a film for retort packaging.

[0002]

2. Description of the Related Art A film made of a polyamide resin has excellent properties such as gas barrier properties, toughness, pinhole resistance, heat resistance and oil resistance. For this reason, polyamide is used as a base material for single-layer films or laminate films, especially in the field of packaging films, especially food packaging.
Further, it is used as a constituent material of a multilayer film by coextrusion with another resin. In recent years, in particular, demand for retort food packaging films has been increasing.

In the case of producing a film from a polyamide resin, the film is often formed by melt-kneading at a temperature about 50 to 100 ° C. higher than the melting point of the polyamide resin to be used in consideration of the fluidity and productivity of the resin. . When the polyamide resin is held at such a temperature, the polyamide resin may be partially cross-linked or deteriorated, and may form a gel-like substance or may be colored. Therefore, when manufacturing a film continuously for a long time or when manufacturing a film by an intermittent method such as interrupting the manufacturing in the middle, a number of gel-like substances may be generated on the surface of the manufactured film, The commercial value of the film was sometimes reduced.

[0004] Films used for retort food packaging are sterilized after filling the contents. In recent years, retort treatment is often performed with hot water or steam at about 130 ° C. Is getting tougher. When the polyamide film is treated under such conditions, the mechanical properties of the polyamide film, particularly practical properties such as a large decrease in tensile strength and a decrease in transparency, may be impaired.

Conventionally, even when a film is continuously manufactured for a long period of time, even if it is subjected to the development or retort treatment of a polyamide resin having good thermal stability such as little generation of a gel or less coloring, the practical property is hardly reduced. Research and development on polyamide resins for films are in progress. Regarding polyamide resin compositions having good heat stability and oxidation stability, see, for example, JP-A-59-25826 and JP-A-59-2826.
No. 31089, JP-A-62-149679,
Japanese Patent Application Laid-Open No. 6-16928 discloses a polyamide resin composition containing a polyamide resin and a hydroxyphenylpropionic acid ester and having improved heat stability.
Also, JP-A-4-28727, JP-A-7-268
No. 209 and the like disclose a polyamide film for retort food packaging, in which practical properties are hardly reduced by retort treatment.

[0006]

Problems to be Solved by the Invention
No. 6, JP-A-59-231089, JP-A-59-231089
Japanese Patent Application Laid-Open No. 2-149679 discloses a polyamide resin composition containing a hydroxyphenylpropionic acid ester and having improved heat stability and oxidation stability. However, these prior documents do not disclose specific data on the thermal stability and oxidation stability of the polyamide resin composition. Moreover, there is no specific description about the use of the film, and no technical disclosure or suggestion is made regarding the effect of the retort treatment on the practical properties of the polyamide film. JP-A-6-16928 discloses that the heat stability and oxidation stability of a polyamide resin composition are improved, but a phosphorus-based antioxidant is an essential component. In addition, there is no description about the film in terms of application, and no technical disclosure or suggestion is made regarding the effect of retort treatment on practical properties.

Japanese Patent Application Laid-Open No. 4-28727 discloses a retort food packaging film made of a specific terminal-modified polyamide resin. However, there is no description about the heat stability and oxidation stability of this polyamide resin. Neither was suggested. Also, JP-A-7-268209 discloses that
Although a retort food packaging film comprising a polyamide composition in which a specific antioxidant is blended is disclosed, the thermal stability of the polyamide resin, the oxidation stability,
No description or suggestion is made.

[0008] A technique relating to a polyamide resin composition having improved thermal stability and oxidation stability and a technique relating to a polyamide film for retort food packaging that has a small decrease in practical properties even after being subjected to retort treatment are disclosed. However, there is no disclosure of a technology relating to a polyamide resin for a film which has good thermal stability and oxidation stability and has a small decrease in practical properties even after being subjected to retort treatment. Therefore, in the field of food packaging materials, there has been a demand for the development of a polyamide resin for a film which has good thermal stability and oxidative stability and has a small decrease in practical properties even after being subjected to retort treatment.

[0009]

The present inventors have conducted various studies on a polyamide resin for a film which satisfies the above-mentioned demands. As a result, the present inventors have found that a polyamide resin composition containing a specific amount of a specific antioxidant has a purpose. We have achieved this and arrived at the present invention.

That is, the present invention relates to (A) 100 parts by weight of a polyamide resin, (B) a hydroxyphenylpropionate ester represented by the general formula (1) 0.01 to 1.0.
It is a polyamide resin composition for films containing parts by weight.

Embedded image (In the formula, R ¹ represents an alkyl group having 1 to 3 carbon atoms.)

Hereinafter, the present invention will be described in detail. The polyamide resin (A) used in the present invention is a polyamide resin obtained by polymerizing or copolymerizing a nylon salt comprising a lactam, amino acid, or diamine having three or more ring members and a dicarboxylic acid. Polymerization of these,
Alternatively, the copolymerization can be performed by a known polyamide polymerization method such as melt polymerization, solution polymerization, or solid phase polymerization. Known polyamide production, such as kneading reaction extruders such as batch type reaction vessels, single-tank type or multi-type continuous reaction devices, tubular continuous reaction devices, single-screw kneading extruders, and twin-screw kneading extruders. An apparatus can be used.

Lactams having three or more rings are, for example,
ε-caprolactam, ω-enantholactam, ω-laurolactam, α-pyrrolidone, α-piperidone and the like. Examples of the amino acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminooundodecanoic acid, and 12-aminododecanoic acid.

As the diamine constituting the nylon salt,
For example, tetramethylene diamine, hexamethylene diamine, heptamethylene diamine, octamethylene diamine, nonamethylene diamine, decamethylene diamine, undecamethylene diamine, dodecamethylene diamine,
Aliphatic amines such as 2,2,4- / 2,4,4-trimethylhexamethylenediamine, 1,3- / 1,4-bis (aminomethyl) cyclohexane, isophoronediamine, piperazine, bis (4-aminocyclohexyl) ) Methane, 2,2-bis- (4'-aminocyclohexyl)
Examples thereof include alicyclic diamines such as propane, and aromatic diamines such as meta-xylylenediamine and para-xylylenediamine.

The dicarboxylic acids constituting the nylon salt include, for example, aliphatic acids such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sepatinic acid, nonandioic acid, decanedioic acid, undecandioic acid and dodecandioic acid. Alicyclic carboxylic acids such as dicarboxylic acid, hexahydroterephthalic acid, and 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-body and 2,7-body). In the present invention, the above 3
A homopolymer or copolymer produced by polymerization or copolymerization of a nylon salt comprising a lactam, amino acid, or diamine having at least a member ring and a dicarboxylic acid can be used alone or in combination.

Specific examples of the polyamide resin (A) used include nylon 4, nylon 6, nylon 7, nylon 11, nylon 12, nylon 46 and nylon 6.
6, nylon 69, nylon 610, nylon 611,
Nylon 612, Nylon 6T, Nylon 6I, Nylon MXD6, Nylon 6/66 (Copolymer of Nylon 6 and Nylon 66; hereinafter, copolymer is similarly described),
Nylon 6/610, Nylon 6/611, Nylon 6
/ 12, nylon 6/612, nylon 6 / 6T, nylon 6 / 6I, nylon 6/66/610, nylon 6
/ 66/12, nylon 6/66/612, nylon 6
6 / 6T, nylon 66 / 6I, nylon 6T / 6I,
Nylon 66 / 6T / 6I and the like. Preferred polyamide resins include nylon 6, nylon 12, nylon 66, nylon MXD6, and nylon 6/66 in consideration of heat resistance, mechanical strength, transparency and economy, availability of molded articles, and the like. , Nylon 6/12 and nylon 6/66/12.

The polyamide resin (A) used in the present invention has a concentration in 98% sulfuric acid of 1 according to JIS K6810.
%, The relative viscosity ηr measured at the temperature of 25 ° C. is 2
-6, preferably 2-5. If the relative viscosity is too low, the resulting molded article may have insufficient mechanical strength, and if it is too high, film production may be difficult.

The hydroxyphenylpropionate (B) represented by the general formula (1) used in the present invention (hereinafter simply referred to as hydroxyphenylpropionate), 3- (3-alkyl-) 5-t
-Butyl-4-hydroxyphenyl) propionic acid, or a reactive derivative thereof such as an acid chloride or an acid anhydride;
9-bis (1,1-dimethyl-2-hydroxyethyl)
It can be produced by reacting 2,4,8,10-tetraoxaspiro [5.5] undecane with a known method.

Embedded image (In the formula, R ¹ represents an alkyl group having 1 to 3 carbon atoms.)

In the hydroxyphenylpropionic acid ester represented by the general formula (1), R ¹ represents a methyl group, an ethyl group, or a propyl group, and a methyl group is preferable in view of heat and oxidation stability. Specific examples of hydroxyphenylpropionate include 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5-
Methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-bis [2- [3- (3
-T-butyl-4-hydroxy-5-ethylphenyl)
Propionyloxy] -1,1-dimethylethyl]-
2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-bis [2- [2- (3-t-butyl-
4-hydroxy-5-isopropylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4.
There are 8,10-tetraoxaspiro [5.5] undecane and the like, and among these, 3,9-bis [2- [3
-(3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.
5] Undecane is preferably used.

The polyamide composition of the present invention comprises (A) 100 parts by weight of a polyamide resin and (B) 0.01 to 1.0 part by weight, preferably 0.01 to 0.5 part by weight, of a hydroxyphenylpropionic acid ester. Parts, more preferably 0.0
It contains 5 to 0.25 parts by weight. When the amount of the hydroxyphenylpropionate is less than 0.01 part by weight, the effect of improvement is not always sufficiently exhibited, and even when the amount exceeds 1.0 part by weight, the effect corresponding to the improvement can be expected. Not economically disadvantageous.

The polyamide composition of the present invention may further comprise a known phenolic antioxidant other than hydroxyphenylpropionate, such as tris (2,4-di-t), as long as the properties of the resulting film are not impaired. -Butylphenyl) phosphite, tetrakis (2,4-di-t-)
(Butylphenyl) -4,4'-biphenylene phosphite, etc., phosphorus-based antioxidants, sulfur-based antioxidants, weathering agents including ultraviolet absorbers, metal soaps such as calcium stearate, magnesium stearate, methylene bisamide, ethylene Bisamide compounds such as bisamides, antistatic agents such as poly (oxyethylene) alkylamines, alkylsulfonates, and quaternary ammonium sulfates; various fillers such as silica, talc and montmorinite; antiblocking agents; and various additives such as dyes and pigments May be blended.

The polyamide resin composition of the present invention is produced by blending a polyamide resin, a hydroxyphenylpropionic acid ester and various additives as necessary, and mixing them by a known method. For example, using a known mixing device such as a tumbler or a mixer, a method of dry blending a polyamide resin and a hydroxyphenylpropionate ester to produce a polyamide resin, and dissolving the hydroxyphenylpropionate ester in a soluble solvent in a polyamide. There is a method in which the solvent is evaporated after the resin is sprayed, a method in which the solvent is evaporated, and a method in which the polyamide resin and the hydroxyphenylpropionate are melt-kneaded using a known single-screw or twin-screw extruder, and the like.

As a method for producing a film from the polyamide resin composition of the present invention, a known method for producing a polyamide film can be applied. For example, the polyamide resin composition of the present invention is melt-kneaded with an extruder, extruded into a flat film shape by a T-die or a coat hanger die, cast on a casting roll surface, and cooled to produce a film. There is a tubular method for producing a film by air-cooling or water-cooling a tubular material melt-extruded into a cylindrical shape by a die. Although the produced film can be used in an unstretched state, it is often used as a stretched film. Examples of the stretched film include a uniaxially stretched film, a simultaneous biaxially stretched film, a sequential biaxially stretched film, and the like. These are a roll type uniaxially stretched method, a tenter type sequential biaxially stretched method, a tenter type simultaneous biaxially stretched method, and a tube. It is manufactured by a known stretching method such as the Ller stretching method. The stretching step may be performed continuously after the production of the polyamide film, or the polyamide film may be once wound up and then stretched as a separate step.

The stretching ratio of the stretched film varies depending on the intended use, but is usually 1.5 to 1.5 in the case of a uniaxially stretched film.
It is 5 times, preferably 1.8 to 3.5 times. The tenter-type biaxially stretched film usually has a stretching ratio of 1.5 to 4 times in the winding direction (longitudinal direction) of the film production, and a stretching ratio of 1.times. In the direction perpendicular to the winding direction (lateral direction). 5 to 5 times. When stretching by the tubular method, 1.5 to 4 in the longitudinal direction
And 1.5 to 4 times in the horizontal direction.

Further, the film obtained from the polyamide composition of the present invention can be used as a laminate with another polymer film or aluminum foil. Other polymer films to be laminated include films obtained from low-density polyethylene, high-density polyethylene, polypropylene, ethylene / vinyl acetate copolymer, ionomer resin, and the like.

As a method for producing a laminate of a polyamide film and another polymer film, a known method can be applied. For example, a polyamide film and another one or two
A method of bonding at least one kind of polymer film with an adhesive, or a melt co-extrusion of a polyamide resin and a polymer compound constituting one or more kinds of other polymer films from a multilayer die through an adhesive resin. And the like.

The film obtained from the polyamide resin composition of the present invention has good thermal stability and oxidative stability. Even if the film is continuously operated for a long time, the generation of a gel-like substance is small, and the film is retorted. It is suitable for food packaging materials such as raw noodles, processed foods, pickles, meats, etc., because it has a small decrease in practical properties, and is particularly suitably used as a packaging material for retort foods.

[0027]

The present invention will be described in more detail below with reference to examples and comparative examples, but it is needless to say that the present invention is not limited to these examples. Hereinafter, the polyamide resins, antioxidants, and evaluation methods used in Examples and Comparative Examples are described.

1. Nylon resin used, antioxidant (A): Nylon 6: UBE NY manufactured by Ube Industries, Ltd.
LON 1022B, relative viscosity 3.6) (B-1): 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethyl Ethyl] -2,4,8,1
0-tetraoxaspiro [5.5] undecane: Sumitomo Chemical Co., Ltd. trade name Sumilizer GA-80 (B-2): pentaerythrityl-tetrakis [3-
(3,5-di-tert-butyl-4-hydroxyphenyl)
Propionate]: trade name Irganox 1010 (B-3): octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate manufactured by Ciba Specialty Chemicals Co., Ltd.]: Ciba Specialty Chemicals Irganox 1076 (P): Tris (2,4-di-t-butylphenyl) phosphite: Ciba Specialty Chemicals Co., Ltd. Irgafos 168

2. Evaluation method of gel-like material A polyamide resin and an antioxidant were supplied to a twin screw extruder (manufactured by Nippon Steel Works, TEX30 type), and an extruder set temperature of 250
The mixture was melt-kneaded and granulated at a temperature of 100 ° C. and a screw rotation speed of 100 rpm to produce pellets. After drying the pellets, the pellets were again granulated under the same conditions, and the produced pellets were dried. The pellets were supplied to a single screw extruder (USV25-28-200 manufactured by Union Plastics) equipped with a T die, and the extruder was set at a temperature of 250 ° C. and a screw rotation speed of 40.
rpm, chill roll temperature 40 ° C, thickness 4
After producing a 0 μm polyamide film for 30 minutes, the screw was stopped while maintaining the extruder set temperature,
Production of the film was interrupted for one hour. Then, the screw was rotated to restart the production of the polyamide film. After producing the polyamide film for 30 minutes, the screw was stopped again while maintaining the extruder set temperature, and the production of the film was interrupted for 1 hour. After repeating this operation once again, the production of the film was resumed, and the film 30 minutes after the start of the rotation of the screw was subjected to a diameter of 0.04 m ² using a film gel counter (a FUTEC fisheye counter). The number of gels having a size of 200 μm or more was measured online. The smaller the number of gels, the better the thermal stability.

3. Evaluation method of yellowness YI (1) Preparation of film for evaluation of yellowness YI A polyamide resin and an antioxidant were supplied to a twin-screw extruder (TEX30, manufactured by Nippon Steel Works), and the extruder was set at a preset temperature of 250.
The mixture was melt-kneaded and granulated at a temperature of 100 ° C. and a screw rotation speed of 100 rpm to produce pellets. After drying the pellets, the pellets were again granulated under the same conditions, and the produced pellets were dried. The pellets were supplied to a single-screw extruder (40 mmφEx manufactured by Plastics Engineering Laboratory) equipped with a T-die, and the extruder set temperature was 250 ° C., the screw rotation speed was 40 rpm,
Set to the condition of chill roll temperature 40 ° C, thickness 150μm
A polyamide film for evaluation was produced. (2) Evaluation of Yellowness YI The evaluation film obtained above was placed in an oven at 180 ° C. for 5 minutes.
After holding for a time, an aging treatment was performed. A sample of 5.0 cm in length and 5.0 cm in width was cut out from the evaluation film before and after the aging treatment, and the yellowness YI was measured using a color computer (SM-5-IS-2B manufactured by Suga Test Instruments Co., Ltd.). did. As an index value of the heat discoloration resistance, a change value ΔYI of the yellowness YI of the film before and after the aging treatment was obtained. The smaller the change value ΔYI, the better the oxidation stability (heat discoloration resistance). ΔYI = (YI after aging processing) − (YI before aging processing)

4. Retort treatment evaluation (1) Preparation of retort treatment evaluation film A polyamide resin and an antioxidant were supplied to a twin-screw extruder (manufactured by Nippon Steel Works, TEX30 type), and the extruder set temperature was set to 250.
The mixture was melt-kneaded at a temperature of 100 ° C. and a screw rotation speed of 100 rpm, granulated, pelletized, and dried. The pellets were supplied to a single-screw extruder equipped with a T-die (Plabor φ40Ex type, manufactured by Plastics Engineering Laboratory). The extruder was set to a temperature of 250 ° C., a screw rotation speed of 40 rpm, and a cooling roll temperature of 30 ° C. A 100 μm thick polyamide film was produced. A sample was cut out from this film to obtain an unstretched film for evaluation. Then
A sample having a length of 90 mm and a width of 90 mm was cut out from the unstretched film, attached to a biaxial stretching machine manufactured by Iwamoto Seisakusho, simultaneously biaxially stretched at a stretching temperature of 70 ° C., and stretched 2.8 times vertically and 2.8 times horizontally. Thereafter, the film was heat-set at 210 ° C. to obtain a biaxially stretched film to be retorted.

(2) Retort treatment The biaxially stretched film obtained above (length 150 mm, width 1
50mm) into a retort food autoclave (manufactured by Tommy Seiko, SR-240), 135 ° C, 3.2kg total pressure
/ cm ² (gauge pressure) and a partial pressure of air of 1.0 kg / cm ² (gauge pressure) for 30 minutes.

(3) Measurement of tensile strength retention The tensile strength was measured according to ASTM D-882. The tensile strength retention was determined by [(tensile strength after retort treatment) / (tensile strength before retort treatment)] × 100 (%). The higher the value of the tensile strength retention, the smaller the effect of the retort treatment.

Examples 1 to 3 and Comparative Examples 1 to 4 (A) 100 parts by weight of a polyamide resin were mixed with (B) an antioxidant in the amounts shown in Table 1 and the film was prepared by the method described above. Was produced to prepare a film for evaluating thermal stability, oxidation stability, and retort treatment. Using this film, the number of gels on the film surface, the yellowness YI and the tensile strength were measured, and the results are shown in Table 1.

[0035]

[Table 1]

[0036]

Industrial Applicability The polyamide resin composition of the present invention containing a polyamide resin and a specific hydroxyphenylpropionic acid ester has excellent heat and oxidation stability, a high retention of tensile strength after retort treatment, and a hot water resistance. And a polyamide resin composition suitable for use in food packaging films.

Claims (3)

[Claims] (A) 100 parts by weight of a polyamide resin,
(B) A polyamide resin composition for a film containing 0.01 to 1.0 part by weight of a hydroxyphenylpropionic acid ester represented by the general formula (1). Embedded image (In the formula, R ¹ represents an alkyl group having 1 to 3 carbon atoms.) 2. The method according to claim 1, wherein the (B) hydroxyphenylpropionic acid ester is 3,9-bis [2- [3- (3
-T-butyl-4-hydroxy-5-methylphenyl)
Propionyloxy] -1,1-dimethylethyl]-
A polyamide resin composition for a film, which is 2,4,8,10-tetraoxaspiro [5.5] undecane. 3. A polyamide film for food packaging obtained from the polyamide resin composition for a film according to claim 1.