JPH10204175A - Polyamide resin for being molded into film and polyamide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyamide resin for being molded into a film which does not lose transparency and does not deteriorate in mechanical properties even after retorting under high-temperature high-humidity conditions and to provide a polyamide film comprising the same. SOLUTION: This polyamide is one modified with a (1-22C) diamine and a (1-22C) monocarboxylic acid and having a relative viscosity (ηrel ) of 3.0-5.0, wherein the number [A] of the terminal carboxyl groups of the polyamide and that [B] of the terminal amino groups are 0.85×10,000/113(ηrel -1.2)μeq/g of the polymer, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyamide resin for forming a film and a polyamide resin film made of such a polyamide resin.

[0002]

2. Description of the Related Art Polyamide films, especially biaxially stretched polyamide films, have better strength, flexibility, transparency, heat resistance, chemical resistance, and gas than biaxially stretched polypropylene films and biaxially stretched polyester films. It has a barrier property and can be used in a wide temperature range.It is widely used for packaging and containers such as food packaging, medical packaging, agricultural chemicals and reagent bottles, and for retort packaging. Opportunities for use are increasing.

[0003] In retort packaging, when foods such as fresh noodles and pickles are packaged in a film, the contents are heat-sterilized at about 130 ° C for sterilization after filling the contents for long-term storage. In such retort processing,
Because the film is exposed to high temperatures under high humidity conditions, the mechanical strength is reduced, or the film is whitened and the transparency is impaired. The mechanical strength reduced by the retort treatment can be said to be a level at which practical problems do not usually occur if the tensile strength retention is 90% or more. The tensile strength retention can be defined as follows. Tensile strength retention = (tensile strength after retort treatment / tensile strength before retort treatment) × 100 [%]

To improve the retort resistance, Japanese Patent Application Laid-Open No.
Japanese Patent No. 4232 discloses a method of adding an antioxidant. However, the addition of an antioxidant has the disadvantage of increasing the film production cost. JP-A-4-287
No. 27 discloses a biaxially stretched polyamide film made of a monoamine or a polyamide resin modified with a monoamine and a monocarboxylic acid. However, such a biaxially stretched polyamide film is easily whitened after retort treatment, and when aluminum vapor deposition is performed on the polyamide film, a partially whitened spot called a cloud is likely to appear, which is not always a satisfactory film.

Further, with the recent progress in printing technology, multicolor printing on the surface of a polyamide film is increasing. Transparency is an important point in the appearance of the product because the transparency of the film not only improves the color development of the print but also gives the contents a clean feeling. Transparency is generally good if the haze is 2% or less in a film having a thickness of 15 μm.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to maintain the original transparency of a polyamide film, maintain its mechanical properties even after retort treatment at high temperature and high humidity, and to whiten aluminum-deposited films. An object of the present invention is to provide a polyamide resin for forming a film and a polyamide film comprising the polyamide resin.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and its gist is to modify a diamine having 1 to 22 carbon atoms and a monocarboxylic acid having 1 to 22 carbon atoms. Has a relative viscosity (η _rel ) of 2.5 to
5.0, wherein the number of terminal carboxyl groups [A] (μeq / g of polymer) and the number of terminal amino groups [B] (μeq / g of polymer)
But 0.85 × _10000/113 (η _rel −
1.2) A polyamide resin for film molding characterized by the following.

Hereinafter, the present invention will be described in detail. As the polyamide in the present invention, a linear high molecular compound having an amide bond -CONH- in the molecule, for example, polycaprolactam (nylon 6), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebacamide (Nylon 6, 10), polyaminoundecanoic acid (nylon 11), polylaurin lactam (nylon 1
2), polyamides obtained by modifying their copolymers with a diamine having 1 to 22 carbon atoms and a monocarboxylic acid having 1 to 22 carbon atoms, and preferably, polycaprolactam (nylon 6), polyhexamethylene Adipamide (nylon 66) and polyamides modified by adding a diamine and a monocarboxylic acid at the time of polymerization of a copolymer thereof, and more preferably a diamine and a monocarboxylic acid at the time of polymerization of polycaprolactam (nylon 6). A polyamide modified by adding an acid may be used.

In the present invention, the relative viscosity of the polyamide (η
_rel ) is 2.5 to 5.0 as measured at a concentration of 1% in 98% sulfuric acid and a temperature of 25 ° C. according to JIS K6810. If the relative viscosity (η _rel ) is less than 2.5, molding becomes difficult, the strength is reduced, and if it exceeds 5.0, the melt fluidity is reduced. The relative viscosity (η _rel ) of the polyamide is preferably from 2.8 to 4.5.

The diamine having 1 to 22 carbon atoms includes ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, undecamethylenediamine, dodecamethylene. Diamine, 2,2,4 (or 2,
Aliphatic diamines such as 2,4) -trimethylhexamethylenediamine, cyclohexanediamine, bis- (4
Examples thereof include alicyclic diamines such as 4'-diaminocyhexyl) methane, and aromatic diamines such as metaxylylenediamine and paraxylylenediamine, and preferably aliphatic diamines. The diamine preferably has 1 to 12 carbon atoms.

The monocarboxylic acids having 1 to 22 carbon atoms include acetic acid, propionic acid, isopropionic acid, butanoic acid enanthic acid, caprylic acid, capric acid, pelargonic acid,
Undecanoic acid, lauric acid, tridecanoic acid, myristic acid, myristoleic acid, palmitic acid, stearic acid,
Aliphatic carboxylic acids such as oleic acid, linoleic acid, arachinic acid, behenic acid, alicyclic carboxylic acids such as cyclohexanecarboxylic acid and methylcyclohexanoic acid, benzoic acid, toluic acid, ethylbenzoic acid, phenylacetic acid Aromatic carboxylic acids are preferred, and aliphatic carboxylic acids are preferred.

In the present invention, the number of terminal carboxyl groups [A] (μeq / g of polymer) and the number of terminal amino groups [B] (μeq / g of polymer) of the polyamide are 0.85 × 10000/113 (η), respectively. _rel -1.2) When the number [A] of terminal carboxyl groups is 0.85
If the value exceeds × 10000/113 (η _rel -1.2), the strength retention after retorting decreases. When the number [B] of terminal amino groups is 0.85 × _10000/113 (η _rel -1.
If the value exceeds 2), the strength retention after retorting decreases, and the melt heat stability decreases, resulting in the formation of a gel in the film.

The number of terminal carboxyl groups [A] and the number of terminal amino groups [B] are preferably 0.8 × 1
000/113 (η _rel -1.2) or less, more preferably 0.4 × 10000/113 (η
_rel -1.2) or more, 0.8 × 10000/113 (η)
_rel -1.2) Terminal carboxyl group [A]
Is less than 0.4 × 10000/113 (η _rel -1.2) or the number of terminal amino groups [B] is 0.4
If less than × 10000/113 (η _rel -1.2),
Production of the terminal-modified polyamide resin tends to be difficult.

In the present invention, the number of terminal carboxyl groups is determined by dissolving a polyamide resin in benzyl alcohol,
It can be measured by adjusting the amount to 0.1 N caustic soda. The number of terminal amino groups can be measured by dissolving the polyamide resin in phenol and determining the amount with 0.05 N hydrochloric acid.

The polyamide resin for forming a film of the present invention may be blended with an inorganic filler such as silica or kaolin, or fine silica treated with a silane coupling agent to improve the slipperiness. Separately from the above-mentioned compounds in a range that does not impair the properties, additives such as a lubricant, a release agent, a thermal deterioration inhibitor, an ultraviolet absorber, an antistatic agent, an antiblocking agent, a dye, a pigment, inorganic particles, and a flame retardant. Blending can improve the performance.

The additives may be added in the course of polymerization of the polyamide resin, dry blended with the polyamide resin after polymerization, melt kneaded with the polyamide resin, or a high-concentration masterbatch is prepared. It can be carried out according to an arbitrary addition method such as a method of using it after dilution during molding.

The polyamide film of the present invention can be obtained by molding the above polyamide resin. As a molding method, for example, a molten polyamide resin is continuously extruded from a T-die, a T-die method in which the molten polyamide resin is molded into a film while being cooled by a metal casting roll, and continuously extruded from an annular die. A water-cooled inflation method in which water is contacted and cooled, and an air-cooled inflation method in which water is extruded from an annular die and cooled by air are also used. According to these molding methods, a multilayer film can be obtained by a co-extrusion method in which other raw materials, for example, olefin-based resins such as LDPE, LLDPE, and EVA are simultaneously extruded.

When the biaxially stretched polyamide film of the present invention is obtained, the stretching method is not particularly limited, and any industrially known method can be applied. For example, for a film formed by the T-die method, the film is stretched longitudinally. Is a roll type, and when stretching in the transverse direction, a sequential biaxial stretching method using a tenter method. For a tubular film formed from an annular die, in addition to the above-described sequential biaxial method, a tubular capable of simultaneously stretching vertically and horizontally. A stretching method is used. The stretching ratio is preferably 1.5 to 6 times the length and 1.5 to 6 times the width, and more preferably 2 to 4 times the length and 2 to 4 times the width.

In the laboratory, a table-top stretching machine (for example, T.I.
M. (Long Company or Toyo Seiki Co., Ltd.) can be used to obtain a stretched film. In this case, in order to obtain the same physical properties as an industrially produced stretched film, the preheating temperature before stretching is 60 to 90 ° C., and the stretching ratio is 2.5 to
Stretching may be performed at a heat setting temperature of about 190 ° C. to 220 ° C. 4.0 times.

In the case of a single-layer biaxially stretched polyamide film, it is dry-laminated with an olefin-based resin film such as an LDPE film or an LLDPE film generally called a sealant using a polyether-based adhesive or a polyester-based two-component adhesive. To obtain a laminated film.

The thickness of the polyamide resin layer in the polyamide film of the present invention is preferably 2 to 70 μm, more preferably 5 to 50 μm, and still more preferably 10 to 30 μm.
μm. In the case of a multilayer film, the thickness as a polyamide resin layer is preferably 2 to 50 μm, more preferably 5 to 30 μm. When the thickness of the polyamide film is large, the gas barrier property is improved, but the transparency is reduced. When the thickness is small, for example, when the thickness is less than 2 μm, the strength becomes insufficient. These films can be corona-treated on one side or both sides to improve printability and lamination.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

EXAMPLES The analysis and evaluation of physical properties were carried out by the following methods. (1) Measurement of terminal carboxyl group, terminal amino group, and residual ratio of each terminal: The polyamide resin was dissolved in benzyl alcohol, and titrated with 0.1N sodium hydroxide to measure the amount of terminal carboxyl groups. The polyamide resin was dissolved in phenol and titrated with 0.05N hydrochloric acid to measure the terminal amino groups. The terminal residual ratio was calculated based on the following equation. Terminal residual ratio = Amount of terminal group measured [μeq / Polymer 1
g] / (10000/113 (η _rel -1.2)) × 10
0 [%]

(2) Tensile strength elongation: Orientec,
Using the trade name Tensilon UTM-III-100,
The measurement was performed at 23 ° C. and 65% RH at a sample width of 15 mm, a gap between chucks of 50 mm, and a test speed of 200 mm / min. (3) Transparency: Haze value was evaluated using a haze meter manufactured by Tokyo Denshoku Co., Ltd.

(4) Preparation of test film: Tables 1-3
Ethylenebisstearylamide (trade name: Armowax, manufactured by Lion Corporation) was added to the polyamide resin shown in 10 above.
After dry blending at 00 ppm, a single-layer film having a thickness of 135 μm was formed at a resin temperature of 240 ° C. using a water-cooled inflation molding machine manufactured by Placo. This film is called T.I. M. Using a biaxial stretching machine manufactured by Long Co., Ltd., the film was biaxially stretched 3 × 3 times at 80 ° C., and then heat-set at 210 ° C. to obtain a biaxially stretched polyamide film having a thickness of 15 μm.

(5) Measurement of tensile strength and elongation of biaxially stretched polyamide film: After fixing the biaxially stretched polyamide film on a metal frame, a high pressure steam environment tester PC manufactured by Hirayama Manufacturing Co., Ltd.
After performing retort treatment at 2.7 kg / cm ² and 130 ° C. for 30 minutes using 242S, the tensile strength and elongation were measured again. The ratio of the tensile strength of the film before and after the retort treatment was calculated as the strength retention by the following formula. Tensile strength retention = (tensile strength after retort treatment / tensile strength before retort treatment) x 100 (%)

(6) Evaluation of cloud (white spots): The biaxially stretched polyamide film obtained in the above (3) was subjected to aluminum vapor deposition using a vapor deposition machine manufactured by JEOL Ltd. After fixing the stretched polyamide film to a metal frame, a high-pressure steam environment tester PC242 manufactured by Hirayama Seisakusho
2.7 kg / cm ² , 30 m at 130 ° C. using S
After the in-retort treatment, the presence or absence of whitening was visually evaluated. The case where no whitening was observed was indicated by “○”, the case where whitening spots were slightly present was indicated by “△”, and the case where whitening spots were present was indicated by “×”.

Examples 1-4 A 200 L autoclave was charged with 60 kg of ε-caprolactam and 1.2 kg of water.
Charge the amount of diamine and monocarboxylic acid described in 1,
The vessel was sealed in a nitrogen atmosphere, and the temperature was raised to 260 ° C. The reaction was performed under pressure for 2 hours with stirring, and then gradually released, the pressure was reduced to the pressure shown in Table 1, and the reaction was performed for 2 hours under reduced pressure. After the pressure was restored to normal pressure by introducing nitrogen, stirring was stopped, the strand was taken out as a strand, pelletized, unreacted monomer was extracted and removed using boiling water, and dried to obtain a polyamide resin pellet. A biaxially stretched polyamide film was obtained as a test film using the obtained polyamide resin pellets. Table 1 shows the values of the tensile strength and tensile elongation of the biaxially stretched film before the retort treatment, the strength retention after the retort treatment, and the haze after the retort treatment.

[0028]

[Table 1]

Comparative Example 1 A 200 L autoclave was charged with 60 kg of ε-caprolactam and 1.2 kg of water.
The reactor was sealed under a nitrogen atmosphere, the temperature was raised to 260 ° C., the reaction was carried out under pressure for 2 hours with stirring, then the pressure was gradually released, the pressure was reduced to the pressure shown in Table 2, and the reaction was carried out under reduced pressure for 2 hours. After the pressure was restored to normal pressure by introducing nitrogen, stirring was stopped, the strand was taken out as a strand, pelletized, unreacted monomer was extracted and removed using boiling water, and dried to obtain a polyamide resin pellet. Using the obtained pellets, a biaxially stretched polyamide film was obtained as a test film. Table 2 shows the values of the tensile strength and the tensile elongation of the biaxially stretched film before the retort treatment, the strength retention after the retort treatment, and the haze after the retort treatment.

[Comparative Examples 2 to 4] In a 200 L autoclave, 60 kg of ε-caprolactam and 1.2 kg of water were added in a table.
The amounts of monoamine and monocarboxylic acid described in 2 were charged, the atmosphere was sealed in a nitrogen atmosphere, the temperature was raised to 260 ° C., the reaction was carried out under pressure for 2 hours with stirring, and then the pressure was gradually released.
The pressure was reduced to the pressure described in 1 and the reaction was performed under reduced pressure for 2 hours. After the pressure was restored to normal pressure by introducing nitrogen, stirring was stopped, the strand was taken out as a strand, pelletized, unreacted monomer was extracted and removed using boiling water, and dried to obtain a polyamide resin pellet. Using the obtained polyamide resin pellets,
A biaxially stretched polyamide film was obtained as a test film. Table 2 shows the values of the tensile strength and the tensile elongation of the biaxially stretched film before the retort treatment, the strength retention after the retort treatment, and the haze after the retort treatment.

[0031]

[Table 2]

[Comparative Examples 5 to 7] In a 200 L autoclave, 60 kg of ε-caprolactam and 1.2 kg of water were added.
The amount of diamine and / or monocarboxylic acid described in No. 3 was charged, the atmosphere was sealed in a nitrogen atmosphere, the temperature was raised to 260 ° C., the reaction was carried out under pressure for 2 hours with stirring, and then the pressure was gradually released. The reaction was performed under reduced pressure for 2 hours. After the pressure was restored to normal pressure by introducing nitrogen, stirring was stopped, the strand was taken out as a strand, pelletized, unreacted monomer was extracted and removed using boiling water, and dried to obtain a polyamide resin pellet. A biaxially stretched polyamide film was obtained as a test film using the obtained polyamide resin pellets. Table 3 shows the values of the tensile strength and tensile elongation of the biaxially stretched film before the retort treatment, the strength retention after the retort treatment, and the haze after the retort treatment.

[0033]

[Table 3]

[0034]

Industrial Applicability The polyamide resin for forming a film of the present invention is useful for the production of a film for retort applications without any deterioration in mechanical properties and transparency under high temperature and high humidity. The polyamide film of the present invention does not deteriorate in mechanical properties during retort treatment, has a small haze value, does not whiten even in an aluminum vapor-deposited film, and can be widely used and useful as a packaging material for foods and the like requiring retort treatment. .

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08J 5/18 CFG C08J 5/18 CFG // B29K 77:00 B29L 7:00 (72) Inventor Morio Kakuda Higashi-Hachiman, Hiratsuka-shi, Kanagawa 5-6-1, Mitsubishi Engineering Plastics Co., Ltd. Technology Center

Claims (5)

[Claims] 1. A diamine having 1 to 22 carbon atoms and a diamine having 1 to 2 carbon atoms.
A polyamide having a relative viscosity (η _rel ) of 2.0 to 5.0, which is modified with a monocarboxylic acid of No. 22; the number of terminal carboxyl groups [A] (μeq /
Polymer 1 g) and the number of terminal amino groups [B] (μeq
/ G of polymer was 0.85 × 10000 /
113 (η _rel -1.2) or less, a polyamide resin for film molding. 2. A polyamide film comprising the polyamide resin according to claim 1. 3. A polyamide film for retort packaging, comprising the polyamide resin according to claim 1. 4. The polyamide film according to claim 2, wherein the polyamide film is a biaxially stretched film. 5. The polyamide film according to claim 2, wherein the polyamide film is laminated with an olefin resin.