JPS5931449B2 - Polyamide film with excellent drawability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a nylon 6 film having optimal characteristics as a base film for vacuum drawing for food packaging.

When food products such as ham, sausage, bread park, fish, and vegetables are used for frozen storage, boiling, reheating, or microwave cooking, vacuum forming is performed using a laminated film made by dry laminating polyethylene film on unstretched nylon 6 film as a base film. After filling the box-shaped or cylindrical molded container with food, the lid is covered with a laminated film made of biaxially oriented polyester film and polyethylene film, and the molded container is used for various purposes (Figure 1). reference). However, the vacuum drawing formability of the base film for vacuum forming, that is, the formability evaluated by the shape conformity (fitting property) of the base film to the drawing mold and the uniformity of the thickness at the drawing corners, is poor. Product value and productivity were significantly reduced. Typical examples of poor drawing formability are shown in Figures 2 and 4. In Figure 2, the shape consistency is extremely poor and the mold shape and film shape do not match at all. The figure shows a case where thickness variation at the drawing corner, that is, necking stretching occurs. This is especially noticeable when the drawing ratio (R/N, R: height, N/I) is small, such as 0.2 to 0.3, when the drawing is shallow.
As described above, nylon 6 film has poor drawing formability, and despite long-awaited improvements, there was no nylon 6 film with excellent drawing formability. Draw forming is often carried out under conditions that provide good draw formability, even if productivity is reduced.
Therefore, the inventors conducted intensive studies on the above-mentioned nylon 6 film having excellent vacuum drawing formability, and as a result, they arrived at the present invention. That is, the present invention relates to a polyamide film that is a substantially non-oriented film made of nylon 6 and has excellent drawability and has the following characteristics. (
1) 4%≦thickness unevenness in the width direction≦10% (2) 0.4X100≦(refractive index in the longitudinal direction) - (refractive index in the width direction)<, 2×103 (3) γ-type crystallinity≦12
1$ Here, the thickness unevenness in the width direction is defined as the maximum film thickness and minimum film thickness measured by measuring the thickness at least 10 points continuously along the width direction at a distance of l sum or more with a U gauge. This is the average value of the difference divided by the average pool thickness plus 100.

r-type crystallinity means that the crystal phase is γ-type crystal (for example, Makr
-0m01chem33.1 (1959) etc., the amide group of nylon 6 is C-N and C-
crystals with a bent molecular structure that rotates around C bonds and deviates from a planar structure) and α-type crystals (for example, J
, pOly-SciUl59 (1955), etc., two crystals with a planar zigzag structure
Considering only the crystal type, it is the weight percent of the γ type crystal in the molecular structure including the crystal type and the amorphous phase. The r-type crystallinity was determined according to the following formula. D,28 and D974:9
The difference in the refractive index between the longitudinal direction and the width direction is determined from the infrared absorption spectrum at 28 cm1 and 974 cm1.
7)) or measurement of refractive index (J, Appl, POly
, Sci., 2717 (1964).

Of course, all of the above three physical property values must be satisfied at the same time, and if even one property is outside the above range, excellent vacuum formability cannot be obtained. More preferable physical properties include (1) Thickness unevenness in the width direction≦8(01) (2) 0.4×103≦refractive index in the longitudinal direction, refractive index in the width direction≦1×103 (3) R-type crystallinity≦10 ($ ) (4) Longitudinal thickness unevenness≦15(a)′ (5) 30(5)≦α-type crystallinity 10γ-type crystallinity≦4
The relative viscosity of 5% (6) nylon 6 film in 98 (fl) sulfuric acid is ≧3.0.

Mainly thickness unevenness in longitudinal and width directions, birefringence value,
and γ-type crystallinity are characteristics necessary for forming into a film with uniform thickness and excellent transparency.
Total crystallinity is a necessary property for shape conformity to the molding die. Among films that satisfy the above physical property values, those that have even more preferable vacuum formability are those that satisfy the following relationship.

That is, [width direction thickness unevenness] (a) x [γ-type crystallinity (4
))]≦110 has particularly excellent vacuum formability. The method for producing the polyamide film of the present invention will be described below, but the method is not necessarily limited thereto.
Manufacturing method 1 Nylon 6 pieces, talc, as an additive
Micas such as graphite, molybdenum disulfide, mica powder, phlogopite, muscovite, and iron mica; highly open inorganic substances such as magnesium hydroxide; organic substances such as inosides; nylon 22; and polyhexamethylene terephthalate. One or two selected from polymer compounds such as lamids
The above seeds are mixed with nylon 6 chips, and after drying by a conventional method, the nylon 6 and the melt are extruded from an extruder, and the first cylinder is heated at a surface temperature of 100 to 140°C using, for example, water as a heating medium. The cast film is continuously cast on the staying drum, transferred to a second casting drum whose surface temperature is maintained at 40 to 98°C, and then wound up. Examples of the heat medium include water (steam) and Tousum A (
Diphenyl heating medium manufactured by Tau Chemical Co., Ltd.), Unilube (
Among them, water (steam) is particularly preferable. is preferred, followed by Tousum A.

Immediately after extrusion of the melted product or after casting, it is slightly stretched at least in the width direction at 95 to 200°C by about 1.3 to 2.2 times.

Production method: unstretched nylon 6 film, 16 in the case of dry heat treatment
Heat treatment is performed within a temperature range of 5 to 210°C, and in the case of wet heat treatment, 120 to 190°C.

Of course, any method may be used for manufacturing, but limited manufacturing method 1 is the best from the viewpoint of simplicity of manufacturing process, ease of handling, uniformity of quality, etc.

The polyamide film of the present invention may contain optional additives, such as lubricants, thickeners, antioxidants, ultraviolet absorbers,
Thinning agents, fillers, stabilizers, end-capping agents, antistatic agents, crystal nucleating agents, dyes, pigments, conductive particles, etc. may be added within the range that does not significantly reduce the characteristics of the present invention. It is clear that it may be copolymerized or blended with other polymeric compounds such as polyolefin, polyamide, polyester, polyvinyl alcohol, polyacrylonitrile, polysulfone, polyurethane, polycarbonate, etc., or may be laminated.

The thickness of the film of the present invention is not particularly limited, but is 15 to 40 mm.
0 micron, particularly preferably in the range of 40 to 80 micron, and even in 98% sulfuric acid, the relative viscosity is 3.0 microns.
The above is preferable. The polyamide film of the present invention can be used for ham, sausage, bread park, fish, vegetables, meat, etc.
It is a film with excellent formability as a base film for vacuum drawing for food packaging such as If a composite film made by laminating a polyethylene film after applying an anchor coating agent to a K-coated nylon 6 film coated with an oxygen and water vapor barrier resin is used as a base film for shallow and deep drawing vacuum forming, it will easily fit into the mold. The composite film has good shape conformity, and can be vacuum-formed to be transparent and uniform without thickness unevenness at corner portions.

In addition, when general processing other than vacuum forming (coating, drying, etc.) is applied to the heather invention polyamide film before vacuum forming, if the processing conditions are approximately 80 to 120°C, X as polyamide film
, <10% film is preferably used.

The nylon 6 film of the present invention obtained in this manner not only has excellent vacuum formability as described above, but also has stronger film stiffness compared to conventional nylon 6 films, making it easier to handle, especially in coating and laminating operations. It has excellent properties such as flexibility and handling, as well as thermal dimensional stability and heat resistance, so it exhibits excellent properties not only for vacuum forming applications but also for separators, transfer paper, special industrial materials, etc. .

In order to make the present invention easier to understand, Examples and Comparative Examples will be described below, but the present invention is not necessarily limited to these.

Examples 1 to 5 After mixing 0.10 parts by weight of talc as an additive with 100 parts by weight of nylon 6-chip [CMlO4l manufactured by Toray Industries, Inc.], the mixture was fed to a 60ml extruder (L/D=32) and heated at 275°C.
and extruded through a nozzle with a 1.011 slit.

The molten film was cast onto a first casting drum (diameter 600/7It71) heated to various surface temperatures using water or steam as a heating medium, followed by a second casting drum heated to a surface temperature of 89°C. After casting on two casting drums (diameter 300m7!l), it was wound up. After laminating an unstretched polyethylene film (120 microns) to the unstretched nylon 6 film (60 microns), vacuum drawing molding (drawing ratio 0.5, forming temperature 114°C) was performed.
), and the shape conformity (fitting properties) and the uniformity of the thickness at the drawing corners (netking) were investigated. As shown in the following table, if all the physical property values of nylon 6 are not within the range of the present invention, it can be seen that the moldability is poor and the transparency is also poor. However, △n: Difference between the refractive index in the longitudinal direction and the refractive index in the width direction UR-T
D: Thickness unevenness in the width direction ×
It is indicated by a mark, and only the complete case is marked as O.

Examples 6 to 7 As described above, it can be seen that even additives have no effect unless they are special additives such as talc, Mg(0H)2, etc.

Examples 13 to 20 100 parts by weight of nylon 6 [CMlO2l: manufactured by Toray Industries, Inc.] chips were mixed with 0.505 parts by weight of talc as an additive, then supplied to a 60 mm extruder (L/D = 28), and
Melt at 1.0 mT! It was extruded from a die with an L-slit gap and maintained at 98°C.
Thereafter, an unstretched film of 60 microns was prepared in the same manner as in Example 3, and laminated with an unstretched polyethylene film of 120 microns, followed by vacuum drawing and re-forming.

The method of adding additives in Examples 6 and 7 is as shown in the following table. Note that Δn and UR-TD had almost the same values as in Example 3. In this way, even if the same additives are used and the film forming conditions are exactly the same, if the additives are added at different times, there can be large differences in formability, especially the presence or absence of netting, that is, the film thickness after forming. I understand.

Examples 8 to 12 The additive talc used in Example 3 was changed to those shown in the following table, and the rest was carried out in the same manner as in Example 3, followed by lamination and evaluation of moldability.

However, all UR-TDs were in the range of 4 to 70 tons). In this way, even if the birefringence value (△n) and the γ-type crystallinity (Xγ) are both within the desired physical property value range, if the total crystallinity (Xα×Xγ) is outside the range, It can be seen that the moldability is not good.

Examples 21 to 26 [Unstretched films were subjected to dry heat treatment (in air) for 10 seconds at the temperatures shown in the following table, and the moldability of the films was evaluated in the same manner as in Example 1.

Thickness unevenness is 4 to 10, birefringence is 0.4 x 1031 x 10
It was 3 or less. In this way, formability is improved unless the temperature is appropriate. It turns out there isn't.

Examples 27-36 Nylon tip [CMlO4l: manufactured by Toray Industries, Inc.] 10
0 parts by weight, 0.05 parts by weight of talc and 0.10 parts by weight of ethylene bisstearylamide as additives, and then fed to a 150 ml extruder (L/D = 34).
After melting at ℃, it was extruded through a 3 m wide die with a 1.0 m711 slit.

The molten film was cast onto a casting drum (diameter 610 mm, 1 sandblasted) heated to a surface temperature of 14°C, then cooled to 60°C and then heated to 4°C.
A non-stretched film of 0 micron was obtained. The properties of the unstretched film were measured at 10 points at 250 mm intervals, and the formability (drawing ratio: 0.3, forming temperature: 125°C) was evaluated, as shown in the following table. Got the results. In this way, even if the crystal structure and birefringence values are within the preferred range, if the film has poor thickness unevenness, the moldability will be poor. It is necessary that the thickness unevenness in the width direction is within 10%, and more preferably the thickness unevenness in the longitudinal direction is within 15%. Examples 37 to 40 Samples (40 microns) were formed in the same manner as Examples 1 to 5, with Xγ varying depending on the casting drum temperature.

Polyvinylidene chloride (PVDC) is added to this unstretched film.
) Coated with resin to a thickness of 3 microns, 80 to 11
It was dried in an atmosphere maintained at 0°C. After coating and drying, the properties and moldability of the PVDC coated nylon film (at a drawing ratio of 0.3 and a temperature of 125° C.) were evaluated, and the results shown in the following table were obtained. In this way, even with moist heat treatment, the
It can be seen that if the temperature is as low as ℃, the moldability cannot be improved.

Example 44 0.1 wt part of the additive talc used in Example 3 was added to
The thickness unevenness in the width and longitudinal direction is all 4 to 10 (: fl
), and the birefringence is 0.4×1031×103 or less.

As described above, it has been found that even when an unstretched film is coated with PVDC, the film whose properties after coating satisfy the conditions of the present invention has excellent vacuum formability.

Examples 42, 43 The 60 micron stretched film obtained in Example 1 with poor formability was subjected to moist heat treatment for 5 seconds at the temperature shown in the following table.
The moldability of the film was evaluated in the same manner as in Example 1.

The thickness unevenness was 10% or less, and the birefringence was 1×10 3 or less. After changing to 0.5 part of barium stearate and 0.01 part of aluminum borate, the film was formed and laminated in the same manner as in Example 3, and the moldability was evaluated.

Claims (1)

[Scope of Claims] 1. A polyamide film that is a substantially non-oriented film made of nylon 6 and has excellent drawability and has the following properties. (1) 4%≦Thickness unevenness in the width direction≦10% (2) 0.4×10^3≦[(Refractive index in the longitudinal direction)−(
Refractive index in the width direction) ≦2×10^3 (3) γ-type crystallinity ≦12%