KR0134560B1 - Preparation process of polyamide film - Google Patents

Abstract

The present invention relates to a method for producing a polyamide sequential biaxially stretched film having excellent stretchability and workability, wherein the maximum stretching stress in the longitudinal stretching step is 1 to 10 g / d, and the maximum stretching stress in the transverse stretching step. Is 0.1 to 5 g / d, and the heat setting stress in the final heat setting step is 1 g / d or less.

Description

Polyamide Film Manufacturing Method

The present invention relates to a method for producing a polyamide film, and in particular, a method for producing a polyamide film excellent in high strength, high modulus and low shrinkage stability with polyamide mainly composed of aliphatic polyamide as a sequential axis. It is about.

Polyamide biaxially oriented films have been widely used as packaging materials for food packaging, chemical packaging, etc. because of their excellent gloss, chemical resistance, and gas barrier properties, and high mechanical strength. Generally, simultaneous biaxial stretching and sequential biaxial stretching are well known as biaxial stretching methods for stretching unoriented films of plastic polymers in mutually perpendicular directions to improve physical properties such as mechanical properties and gas barrier properties of the films.

Simultaneous biaxial stretching methods include two types of film melt, which are a method of inflation, and a polymer melt stream coming out of the die by the tenter method, and stretching in the MD and TD directions. There are two methods, and the sequential biaxial stretching method includes stretching in advance in the MD direction, and then stretching in the Teddy direction separately from the tenter. However, aliphatic polyamides such as nylon 6 and nylon 66 have a problem that it is difficult to obtain a uniform stretched film by successive biaxial stretching.

In the case of sequential biaxial stretching of aliphatic polyamide, the two-stage stretching in the eddy direction arranges the molecular chains in the same direction. At this time, the amide bonds present in the aliphatic polyamide molecular chain easily form hydrogen bonds with the amide bonds in the other molecular chains located in the vicinity, and the direction of the hydrogen bond is perpendicular to the MD direction and is the same as the Teddy direction. do. The hydrogen bonds converging in the Teddy direction may concentrate the stretching stress or increase the magnitude of the stretching stress when the TDY stretching is performed, causing uneven stretching or severe cutting. The difficulty of the method by sequential biaxial stretching in the production of such aliphatic polyamide films is disclosed, for example, in Japanese Tokhe Publication No. 48-9899. Japanese Patent Publication No. 87-2195 discloses a method of successively biaxially stretching a polyamide film by containing a polyamide monomer or oligomer, but this method has a problem in that additives adhere to the rollers during film production. There is also a problem that physical properties deteriorate.

In addition, Japanese Patent Publication Nos. 88-5986 and 89-12496 disclose a method of stretching in one direction and then rolling in a right angle direction, and Japanese Patent Publication No. 47-8195 discloses a roll stretching process. A method of controlling crystallization is disclosed, and in US Pat. No. 48-8868, a method of attaching water vapor to an oriented stretched film is disclosed.

However, all of the above-mentioned conventional methods partially solve the above-mentioned problems that occur when manufacturing successive biaxially stretched films from aliphatic polyamide polymers, but do not disclose a method of completely solving the above problems.

The present invention has been made to fundamentally solve the above problems in the production of polyamide biaxially stretched film. As a result of obtaining biaxially stretched aliphatic polyamide polymer film, the present invention provides high strength, high modulus and low shrinkage stability. It is an object to provide a method for producing a polyamide sequential biaxially stretched film having.

In order to achieve the above object, the present invention is a polyamide sequential which is carried out in the process of producing an unstretched film of a polyamide polymer through a T-die, stretching the unstretched film in a longitudinal direction, and then stretching and heat setting in a transverse direction. In the biaxially stretched film production method, the maximum stretching stress in the longitudinal stretching step is 1 to 10 g / d, the maximum stretching stress in the transverse stretching step is 0.1 to 5 g / d, and the heat in the final heat setting process Provided is a method for producing a polyamide sequential biaxially oriented film, characterized by a fixed stress of 1 g / d or less.

In the present invention, the maximum stretching stress in the longitudinal stretching step during the successive biaxial stretching is preferably 1 to 10 g / d. When the maximum stretching stress is 1 g / d or less during longitudinal stretching, sufficient molecular chain orientation in the longitudinal direction does not occur, resulting in low tensile strength or tensile modulus. In addition, when 10 g / d or more, the orientation of the molecules in the longitudinal direction is excessive and various problems occur in the laterally stretching process, which is a subsequent process, and the heat setting stress is increased due to molecular chain reorientation at the time of heat setting. The non-shrinkage rate in a final film also becomes large and undesirable. Moreover, it is preferable to perform extending | stretching in a horizontal direction in the range of the maximum extending stress in 0.1-5 g / d.

In the present invention, the maximum stretching stress range in the transverse stretching as described above is a value obtained empirically in consideration of workability that can be judged as sequential biaxial stretching and tensile properties and thermal properties in the final film. If the maximum stretching stress in the transverse direction is 0.1g / d or less, satisfactory transverse tensile properties are not obtained, and in the case of 5g / d or more, film nonuniformity due to necking phenomenon and severe film breakage occur. Done. In the present invention, all of the values of the maximum stretching stress in the longitudinal direction and the transverse direction are important, but it is the value of the maximum stretching stress in the transverse direction that further influences the physical properties of the film. The reason for this is difficult to explain morphologically precisely, but the strength of the hydrogen bonds and the number of hydrogen bonds which are bonded in the transverse direction inside the longitudinally stretched film are rearranged in the transverse stretching so that the stable manufacturability of the film is achieved. It is thought to have a greater influence on physical properties.

In addition, in the present invention, the maximum heat setting stress in the heat setting process is a large variable in determining the shrinkage rate in the final film.

In this invention, the maximum stress of the preferable range at the time of heat setting is 1 g / d or less. If the maximum stress at the time of heat setting is 1g / d or more there is a problem that the stress of the internal molecular chain remains a large number, the thermal properties deteriorate.

Next, the present invention will be described in more detail with reference to preferred embodiments of the present invention.

However, the following examples are provided only for better understanding of the present invention, and the present invention is not limited to these examples.

Example 1

Poly-ε-caprolactam (relative viscosity = 3.1) was melted by heating to 265 ° C. using a 60 mm diameter extruder with a tie, extruded into a film by weighing with a gear pump, and cooled on a cooling roll at 20 ° C. to approximately thickness. An unstretched film of 210 µm and a width of about 25 cm was obtained. This unstretched film was extended | stretched longitudinally using the breadcrumb roll of 3 mm of running speed of 110 mm and width 700 mm. At this time, the stretching temperature in the longitudinal direction was 50 ℃, the maximum stretching stress is shown in Table 1. Immediately thereafter, transverse stretching was performed at 95 ° C in a transverse yarn yarn tenter having a width of about m and a length of about 11 m. At this time, the maximum stretching stress is shown in Table 1. Then, the heat setting was performed in a hot chamber under the conditions of the heat setting maximum stretching stress shown in Table 1 below. The physical properties of the film thus produced were evaluated in the following manner, and the results are shown in Table 1.

Example 2-5 and Comparative Example 1-4

In Example 1, the same conditions as in Example 1 were carried out except that the conditions of the maximum stretching stress in the longitudinal stretching, the lateral stretching and the heat setting step were as shown in Table 1 below.

The physical properties and process workability of the biaxially stretched polyamide films prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were evaluated according to the following methods, and the results are shown in Table 1 below.

[Assessment Methods]

-Evaluation of stretchability (when manufacturing stretched film)

1. Cutting frequency: 1 or less / day. … … … … … … … … … … … Good

2. Number of cuts: 1 ~ 2 / day. … … … … … … … … … … … Great

3. Number of cuts: 4 or more / day. … … … … … … … … … … … Bad

-Evaluation of workability (when manufacturing packaging film)

1. Cutting frequency: 1 or less / day. … … … … … … … … … … … Good

2. Number of cuts: 2-3 / day. … … … … … … … … … … … Great

3. Number of cuts: 4 or more / day. … … … … … … … … … … … Bad

Polyamide film being manufactured by the present invention as shown in the above Table 1, the longitudinal tensile strength of 1600kg / cm ² or more, the longitudinal tensile modulus of elasticity is 15000kg / cm ^2, the non-aqueous shrinkage properties of more than 6% Has This physical property is an excellent one not realized in the conventional method.

Claims (2)

In the polyamide sequential biaxially stretched film manufacturing method performed by the process of manufacturing an unstretched film of a polyamide polymer through a TiD, and extending | stretching this unstretched film longitudinally, and extending | stretching and heat setting in a transverse direction, longitudinal stretch The maximum stretching stress in the process is 1 to 10 g / d, the maximum stretching stress in the lateral stretching process is 0.1 to 5 g / d, and the heat setting stress in the final heat setting process is 1 g / d or less. The manufacturing method of the polyamide sequential biaxially stretched film made into. In the polyamide sequential biaxially stretched film manufacturing method performed by the process of manufacturing an unstretched film of a polyamide polymer through a TiD, and extending | stretching this unstretched film longitudinally, and extending | stretching and heat setting in a transverse direction, longitudinal stretch The maximum stretching stress in the process is 1 to 10 g / d, the maximum stretching stress in the lateral stretching process is 0.1 to 5 g / d, and the heat setting stress in the final heat setting process is 1 g / d or less. A polyamide sequential biaxially oriented film having a longitudinal tensile strength of at least 1600 kg / cm 2, a longitudinal tensile modulus of at least 15000 kg / cm 2, and a non-shrinkage ratio of 6% or less, which is produced by a method of forming a film.