JP3505898B2 - Manufacturing method of sequential biaxially stretched polyamide film - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a biaxially stretched film of polyamide. More specifically, the present invention relates to a method for industrially advantageously producing a polyamide biaxially stretched film by using a specific polyamide copolymer, without newly producing a special stretching device dedicated to polyamide, using an existing device.

[0002]

In the field of stretched films of thermoplastic resins, films are biaxially stretched in order to increase the mechanical strength of the films, and biaxially stretched films of polyester, polyvinyl chloride, polystyrene, polypropylene and the like are used. It is well known in the art, and its products are commercially available. Polyamide, which is one of these thermoplastic resins, has excellent gas barrier properties, strength and rigidity, and if it can be biaxially stretched, mechanical strength will increase and it will be even more excellent for packaging materials. Expected to be something.

However, since polyamide has a crystal structure due to a hydrogen bond, interaction between molecules is extremely large, and when biaxial stretching is attempted, crystallization has already progressed at the stage of the first stretching, and During the step drawing, tearing or necking occurred, and it was difficult to obtain a film having industrial value.

In order to improve this, various studies have hitherto been carried out. For example, in JP-B-37-2195, a polyamide film is made to contain its monomer and oligomer as a plasticizer, and this is successively biaxially blended. The method of stretching is mentioned. Certainly, if the content of monomers and oligomers is high, a film with no uneven drawing can be obtained.
However, the monomers and oligomers present in the film reduce the stiffness and dimensional stability of the film, and further, the monomers and oligomers easily adhere to the stretching roll, which adheres to the film and blocks the film after stretching. It has drawbacks such as a cause. Further, if the content is reduced in order to prevent such a phenomenon, it becomes difficult to stretch the film and the purpose cannot be achieved.

On the other hand, for example, Japanese Examined Patent Publication No. 43-9399.
The publication describes a method of simultaneously stretching in two directions. However, this method requires a simultaneous biaxial stretching machine exclusively for polyamide having an extremely complicated structure, and the physical properties of the chuck part of the stretching machine become non-uniform, so the yield is poor and an industrially advantageous manufacturing method. However, the stretched film produced is expensive.

Further, in addition to the above-mentioned simultaneous biaxial stretching method, the successive biaxial stretching method has been studied as described in JP-B-47-3195 and JP-A-51-49268. ing. However, all of these require not only a special device dedicated to them, but also the range of stretching conditions is very narrow, steady production is difficult, and it is hard to say that they are industrially effective methods.

[0007]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The inventors of the present invention have earnestly studied to solve the problems relating to the stretchability of the above-mentioned polyamide film, and as a result, if a specific polyamide copolymer is used, industrially, That is, it is possible to produce a polyamide biaxially stretched film by using a biaxial stretching device that can be usually used for existing polyester, polyvinyl chloride, polypropylene, polystyrene, etc. without specially preparing a stretching device dedicated to polyamide. The present invention has been completed when the present invention has been discovered.

That is, the gist of the present invention is that a substantially amorphous film of polyamide is stretched in one direction in a first step (hereinafter referred to as "uniaxial stretching"), and then in a second step in a direction substantially perpendicular to the stretching direction. In the polyamide stretched film to be referred to as "biaxially stretched" hereinafter, as the polyamide, 85 to 99% by weight of ε-caprolactam, 0.5 to 5% by weight of aminododecanoic acid, and an equimolar salt of hexamethylenediamine and adipic acid are used. A polyamide terpolymer having a content of 0.5 to 10% by weight is used.

The present invention will be described in detail below. The polyamide used in the method of the present invention includes 85 to 99% by weight of ε-caprolactam and 0.5 to 99% of aminododecanoic acid.
5, and a polyamide terpolymer consisting of 0.5 to 10% by weight of an equimolar salt of hexamethylenediamine and adipic acid.

The polyamide terpolymer of the present invention is prepared by charging ε-caprolactam and equimolar salts of aminododecanoic acid and hexamethylenediamine and adipic acid into a polymerization tank according to a conventional method, that is, ε-caprolactam polymerization. It is manufactured in the same manner as in the case.

As a method for charging the polymerization vessel, aminododecanoic acid and an equimolar salt of hexamethylenediamine and adipic acid themselves may be charged together with ε-caprolactam into the polymerization vessel and polymerized. Components that make up the nylon salt, that is, the amount of hexamethylenediamine component and adipic acid component in such a proportion that they become nylon salt,
It is also possible to directly charge ε-caprolactam and aminododecanoic acid into a polymerization tank for polymerization.

In the present invention, the amount ratio of the equimolar salt of ε-caprolactam, aminododecanoic acid, hexamethylenediamine and adipic acid, which constitutes the polyamide terpolymer, is an important constituent factor. That is, in this polyamide terpolymer, the melting point is 197 to 218.
C., the aminododecanoic acid is usually 0.5 to 5% by weight, preferably 0.5 to 4% by weight, the equimolar salt of hexamethylenediamine and adipic acid is usually 0.5 to 10% by weight, preferably Is essential to be contained in an amount of 0.5 to 4% by weight. Further, various additives such as a lubricant, an antistatic agent, an antiblocking agent, a stabilizer, a dye, a pigment, and inorganic fine particles can be added to the polyamide copolymer within a range that does not affect the properties of the film.

When the equimolar salt of aminododecanoic acid or hexamethylenediamine and adipic acid is more than 15% by weight, the stretching is extremely easy, but the crystallinity and the physical properties of the film are substantially deteriorated. On the other hand, if the content is less than 1.0% by weight, a stretched film cannot be industrially advantageously obtained with an existing stretching apparatus. Then, from the polyamide terpolymer in the usual manner, that is, the polyamide terpolymer is added with the residual monomer and oligomer contents of 0.5% by weight.
It is extracted to the following temperature, then heated to a temperature of 280 ° C or lower, extruded into a film by a T-die method or an inflation method in a molten state, and cooled rapidly to a temperature of 0 to 60 ° C to obtain substantially no heat. A regular polyamid film (hereinafter simply referred to as "unstretched film") is obtained. In the method of the present invention, first, this unstretched film is axially stretched at a temperature of 35 to 70 ° C. for 2.5 to 4 times and then at a temperature of 35 to 120 ° C. in a direction substantially perpendicular to the stretching direction. Deformation rate 1000% / min ~ 5000
Biaxial stretching is performed 2.5 to 5 times at 0% / min.

The biaxial stretching method in the present invention is longitudinal stretching,
The present invention will be described in more detail with reference to a specific stretching method in the case where either the transverse stretching may be performed first, or the longitudinal stretching may be performed on the axis. The stretching conditions such as temperature and draw ratio described below are the same when the transverse stretching is performed on the − axis. That is, first, the unstretched film produced from the polyamide copolymer in the method of the present invention is longitudinally stretched 2.5 to 4 times at a temperature of usually 35 to 70 ° C., preferably 40 to 65 ° C., in the film advancing direction.
At this time, if the temperature is lower than 35 ° C., the film is whitened or broken, and if higher than 70 ° C., uniaxial stretching is possible, but during biaxial stretching, the film is ruptured, necked, uneven in stretching, etc. And a good film cannot be obtained.

Then, the uniaxially stretched film is continuously processed with a transverse stretching device typified by a tenter, etc.
In the temperature range of 5 to 120 ° C., preferably 50 to 100 ° C., the deformation speed is usually 1000 to 50000% / min, preferably 2000 to 40000% / min under conditions of 2.5 to 5
Stretched twice. In this case, when the stretching temperature is lower than 35 ° C., the film is whitened and broken, and when it is higher than 120 ° C., necking and stretching unevenness occur. Further, it is preferable that the temperature in the biaxial stretching is selected to be the same as or higher than the temperature for the uniaxial stretching within the above temperature range. Further, in terms of deformation rate, if it is less than 1000% / min, the probability of film breakage is high, and
If it exceeds 0000% / min, there is a problem in the steady operation of the stretching device. Further, the equimolar salt of aminododecanoic acid and hexamethylenediamine and adipic acid constituting the polyamide terpolymer in the present invention is more likely to crystallize as the amount falls within the scope of the present invention, so the stretching temperature for biaxial stretching is When the deformation rate is lowered within the above range and the deformation rate is increased within the above range, the stretching tends to be more stable.

Another point to be noted in the method of the present invention is to avoid leaving a time of 10 seconds or more after the completion of the uniaxial stretching until the start of the biaxial stretching because it causes film-necking or breakage. Is good. However,
If this condition is not satisfied in the existing biaxial stretching device, the film is instantly frozen by a cooling roll or the like maintained at 0 to 40 ° C immediately after the longitudinal stretching is completed, and then the film is passed through a preheating roll and then subjected to transverse stretching. This time can be increased.

A film stretched at a high ratio like a polyamide biaxially stretched film obtained by the method of the present invention is
Because its dimensions change at room temperature or with the heat it receives during processing,
Heat setting is performed when it is necessary to provide dimensional stability to the product. The heat setting of the polyamide stretched film of the present invention is carried out in the temperature range of 150 to 230 ° C. for 1 to 120 seconds until the shrinkage substantially disappears.

As described above, according to the present invention, since the polyamide copolymer is used as the polyamide, the crystallization of the film by uniaxial stretching is slower than that of the conventional polyamide. Axial stretching can be easily performed, and during stretching, the film can be successively biaxially stretched by a very simple and simple method without causing breakage or necking.

That is, the present invention does not use a special stretching device dedicated to polyamide, but uses a sequential stretching device that has been conventionally used for polyester, polyvinyl chloride, polystyrene, polypropylene, etc. A stretched film can be produced, which is an extremely industrially advantageous method.

The effect of the present invention is to add aminododecanoic acid and equimolar salts of hexamethylenediamine and adipic acid to ε-caprolactam as a polyamide.
It is considered that this is because when the uniaxial stretching is performed, the molecular arrangement and hydrogen bonds of the polyamide film are slightly disturbed to facilitate the subsequent biaxial stretching. Further, when the polyamide terpolymer in the method of the present invention is used as the polyamide, the monomer and the oligomer are contained in the film in excess, so that the film physical properties are deteriorated or the blocking phenomenon of the film due to the adhesion of the monomer and the oligomer to the roll is caused. It does not occur in the present invention.

The present invention will be described in more detail with reference to the following examples.
The following examples do not impose any limitation.

[0022]

【Example】

Example 1 98% by weight of ε-caprolactam and 1% by weight of aminododecanoic acid, equimolar salt of hexamethylenediamine and adipic acid 1 having a relative viscosity of 3.5 measured at 25 ° C. using 98% concentrated sulfuric acid 1 A terpolymer of polyamide terpolymer (copolymerization composition: 98/1/1% by weight), which is composed of 10% by weight and is free of monomers and oligomers, was prototyped in a 70 l autoclave, and the material was used to form a film from a T-type die at 250 ° C It was extruded and cooled by a rotary drum cooled to 20 ° C. to obtain a substantially amorphous film having a thickness of 150 μm.
This unstretched film was first stretched longitudinally between rolls, then laterally stretched by holding both ends with tenter clips, and evaluated from the appearance of the film. The results of the stretching conditions and stretchability at that time are shown in Table 1.

[0023]

[Table 1]

[0024]

EXAMPLE 2 In Example 1, ε-caprolactam 9
A polyamide terpolymer having a relative viscosity of 3.5 (copolymerization composition 99/0. 9%, aminododecanoic acid 0.5% by weight, and hexamethylenediamine / adipic acid equimolar salt 0.5% by weight). (5 / 0.5% by weight) was used, and a trial production was carried out in the same manner as in Example 1, and stretching was carried out to examine the stretchability. The results are shown in Table 2.

[0025]

[Table 2]

[0026]

Comparative Example 1 A prototype was prepared in the same manner as in Example 1 except that a polyamide (hereinafter referred to as “nylon 6”) from which monomers and oligomers having a relative viscosity of 3.5 were removed was used instead of the polyamide copolymer in Example 1. Then, a non-stretched film was prepared and the stretchability was examined. The results are shown in Table 3. As a result, although uniaxial stretching was possible, the film was broken during biaxial stretching, and it was not possible to obtain a biaxially stretched film successively.

[0027]

[Table 3]

[0028]

Example 3 and Comparative Example 2 The biaxially stretched film obtained in Examples 1 and 2 (Experiment No. 4) was heat set in a tensioned state at 200 ° C. for 30 seconds, and this film was
After standing overnight in an atmosphere of 3 ° C. and 65% RH, the breaking elongation and hot water shrinkage were measured. The results are shown in Table 4. Tensileon R manufactured by Orientec Co., Ltd.
TA-10KN crosshead moving speed 300mm / m
Used in. In addition, the hot water shrinkage is measured by attaching a square mark of 80 mm (= L) to the film and leaving it in boiling water for 3 minutes without tension to measure the amount of clogging of the gauge mark ΔL.
Was calculated and calculated as shrinkage = ΔL / L × 100.
For comparison, nylon 6/66 with a relative viscosity of 3.5
/ 12 (copolymer composition 80/5/15) to prepare an unstretched film in the same manner as in Example 1, and then stretched at a uniaxial and biaxial stretching temperature of 50 ° C. to a stretching ratio of 3.0 × 3.3. Then, the obtained film was heat set at 180 ° C. for 30 seconds,
The same measurement as above was carried out and the result is shown in Table 4 as Comparative Example 2.
Also described in. The results show that this film has a very high hot water shrinkage after heat setting and has no commercial value. The upper row of each data shows the film traveling direction, and the lower row shows the value at right angles thereto.

[0029]

[Table 4]

Continuation of front page (56) Reference JP-A-53-37773 (JP, A) JP-A-56-90851 (JP, A) JP-A-62-27128 (JP, A) JP-A-61-177228 (JP , A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B29C 55/14 C08J 5/18

Claims (7)

(57) [Claims] 1. A polyamide stretched film in which a substantially amorphous film of polyamide is stretched in one direction in a first stage, and then stretched in a second stage in a direction substantially perpendicular to the stretching direction, wherein ε-caprolactam is used as the polyamide. 85
~ 99 wt%, aminododecanoic acid 0.5-5 wt%,
And a method of producing a polyamide film, which comprises using a polyamide terpolymer in which an equimolar salt of hexamethylenediamine and adipic acid is 0.5 to 10% by weight. 2. A method for producing a polyamide film according to claim 1, wherein the first stage drawing is carried out at a temperature of 35 to 70 ° C. 3. A method for producing a polyamide film according to claim 1, wherein the first-stage stretching is 2.5 to 4 times. 4. The method for producing a polyamide film according to claim 1, wherein the second stage drawing is carried out at a temperature of 35 to 120 ° C. 5. A method for producing a polyamide film according to claim 1, wherein the second stage stretching is 2.5 to 5 times. 6. A method for producing a polyamide film according to claim 1, wherein the second stage drawing is carried out at a deformation rate of 1000 to 50000% / min. 7. A method for producing a polyamide film according to claim 1, wherein the second stage drawing is followed by heat setting at a temperature of 150 to 230 ° C. for 1 to 120 seconds.