JPS626488B2 - - Google Patents

Description

[Detailed description of the invention]

The method of the present invention relates to a method of stacking and simultaneously stretching a plurality of thermoplastic resin films. For more details, please refer to polyε capramide resin.
The present invention relates to a method in which an unstretched film containing 80% or more of polyethylene terephthalate resin and an unstretched film containing 80% or more of polyethylene terephthalate resin are superimposed and simultaneously biaxially stretched in longitudinal and lateral directions using a tenter method. Regarding the method of stacking and stretching multiple thermoplastic resin films at the same time, please refer to Japanese Patent Publication No. 43-15715.
Publication No. 50-22069, JP-A-51-
31775, JP-A-53-85866, etc. are known, but the reality is that they have not yet been commercialized. In addition, there are methods for simultaneously stretching a laminated film of polyamide resin and other resins, such as Japanese Patent Publication No. 45-279 and Japanese Unexamined Patent Publication No. 49-99369. Examples are provided only. on the other hand,
Among thermoplastic resins, films made of polyε-capramide resin and polyethylene terephthalate resin are both biaxially stretched and used for food packaging, electrical materials, etc., and are extremely useful films among those currently in general use. It is. Regarding the stretching method of these resin films, please refer to Japanese Patent Publication No. 43-9399.
Publication No. 43-9919, Special Publication No. 30-5639
No. 3, Japanese Patent Publication No. 35-11774, etc., are known, but all of them relate to methods for stretching single films, and in particular, for polyethylene terephthalate resin films, a sequential biaxial stretching method is used. The present inventors have investigated a method of simultaneously stretching these two types of useful films, namely polyε-capramide resin film and polyethylene terephthalate resin film, using a single stretching machine, instead of stretching each film individually. As a result, we reached the following conclusion. That is, when an unstretched film containing 80% or more polyε-capramide resin and an unstretched film containing 80% or more polyethylene terephthalate resin are superimposed and simultaneously biaxially stretched vertically and horizontally using a tenter method, preheating is performed immediately before stretching. Temperature 90~
The best method is a simultaneous multiple stretching method, which is characterized by stretching at 150°C and maintaining the stretching temperature between 100 and 140°C, heat setting at a temperature above the stretching temperature and below 230°C, and then separating. That's what it means. In general, polyε-capramide resin films have hydrogen bonds between molecular chains, so they tend to be stretched by the sequential biaxial stretching method, so they are stretched by the simultaneous biaxial stretching method.On the other hand, polyethylene terephthalate resin films Because it does not have hydrogen bonds between molecular chains, it can be stretched by the sequential biaxial stretching method, and in fact, it is mostly produced by the sequential biaxial stretching method. The method of the present invention simultaneously stretches these two types of resin films using different stretching methods using a single stretching machine, and significantly reduces manufacturing costs without impairing the performance of films that were conventionally manufactured separately. It is extremely useful from an industrial perspective. When polyε-capramide resin film and polyethylene terephthalate resin film are stretched individually, the stretching conditions for each are completely different, and it is difficult to uniformly stretch both resin films at the same time no matter which stretching condition is applied. It is. That is, since the stretching temperature of the conventional poly-ε-capramide resin film is much higher than that of the polyethylene terephthalate resin film, when both resin films are simultaneously stretched at the conventional stretching temperature of the poly-ε-capramide resin film, the polyethylene Melting and whitening phenomena of the terephthalate resin film were observed, making it impossible to obtain a uniform stretched film. Conversely, when applying the conventional stretching temperature for polyethylene terephthalate resin film and stretching both resin films at the same time, the polyε capramide resin film may break or the stretching speed cannot be increased because the stretching temperature is too low. Problems such as these occur, making it impossible to perform stable production. In addition, since the stretching temperature of conventional polyethylene terephthalate resin film is the temperature condition for transverse stretching in the sequential biaxial stretching method, when applied as is to the simultaneous biaxial stretching method such as the method of the present invention, polyethylene terephthalate resin The film itself cannot be stretched completely evenly. In addition, in the case of multiple stretching, it is not possible to heat both sides uniformly as in the case of single stretching, and the inner surface is harder to heat than the outer surface, so it is heated at a higher temperature condition than in the case of single stretching. I need to do it. Additionally, when a thermoplastic resin film is generally stretched by the tenter method, only the ends of the film are held by clips, and the center is free, so the center is stretched later than the ends. The so-called Boeing phenomenon occurs.
This phenomenon occurs not only in the case of single stretching but also in the case of multiple stretching, and the mechanism of its occurrence is more complex than in the case of single stretching. That is, in the case of multiple stretching, especially when different types of resin films are stretched at the same time as in the method of the present invention, each stretching stress is different, and the amount of self-heat generation due to stretching and the amount of shrinkage due to heating are also different for each resin film. This is more complicated than stacking multiple films of the same composition. In the case of the method of the present invention, the polyethylene terephthalate resin film has a smaller stretching stress, so the bowing phenomenon at the stretched portion occurs later than that of the polyε-capramide resin film, but the temperature decreases due to the adsorbed moisture in the polyε-capramide resin film. The bowing phenomenon progresses faster during the stretching process than polyε capramide resin film. In addition, in the bowing relaxation phenomenon from the stretched portion to heat setting, the polyethylene terephthalate resin film has a larger thermal contraction, so relaxation occurs faster, and the final amount of bowing generated is smaller. Under conventional stretching conditions, the bowing phenomenon cannot be suppressed due to the influence of film-to-film interaction. In general, the bowing phenomenon occurs due to the stress balance at the boundary between the preheating section and the stretching section immediately before stretching, and the stress balance at the boundary between the stretching section and the heat setting section. It is possible to reduce stress strain and suppress its occurrence. The present inventors carried out stretching under various temperature conditions as described later in Comparative Examples, and arrived at the method of the present invention. The temperature conditions in the method of the present invention are completely different from the usual stretching conditions for polyε-capramide resin films and polyethylene terephthalate resin films, and can suppress the bowing phenomenon of each film to a minimum. The polyε-capramide resin film used in the method of the present invention includes those containing 80% or more of polyε-capramide, and is applicable even if it contains less than 20% of aromatic polyamide, copolymerized polyamide, etc. Furthermore, if the polyε capramide resin film is made to absorb water in advance, it can be smoothly stretched while preventing the occurrence of netting. In addition, the polyethylene terephthalate resin film of the present invention includes those containing 80% or more of polyethylene terephthalate resin, and even if it contains less than 20% of other aromatic polyesters, copolymerized polyesters, etc. be. Comparative Example A polyε capramide resin was melted at 260°C using an extruder and extruded from a T-die onto a cooling roll at 20°C to form an unstretched film with a thickness of 150μ. The unstretched film was subjected to water absorption treatment to absorb 5% by weight of water. Meanwhile, polyethylene terephthalate resin was similarly melted at 280℃ using an extruder.
An unstretched film having a thickness of 140 μm was formed by extruding from a T-die onto a cooling roll at 80° C. These two types of unstretched films are superimposed and stretched using a tenter-type simultaneous biaxial stretching machine to form 3 x 3.5 sheets in length and width.
Biaxial stretching was carried out at the same time. At that time, stretching was carried out while changing the stretching temperature conditions as shown in Table 1, and the results as shown in Table 1 were obtained. Stretching speed is 60
m/min. In addition, the amount of bowing means the value obtained by dividing the length by which the center of the stretched film lags the end of the film by the width of the film, and when the value is 0.1 or less, the film was passed.

[Table] The following is a more detailed description of Examples. Example 1 Polyε capramide resin was melted at 260°C using an extruder, extruded from a T die onto a cooling roll at 20°C to form an unstretched film with a thickness of 250μ, and immediately absorbed 6% by weight of water. Ta. Further, polyethylene terephthalate resin was melted at 280°C using an extruder and extruded from a T-die onto a cooling roll at 70°C to form an unstretched film with a thickness of 80μ. These two unstretched films were stacked one on top of the other and were simultaneously biaxially stretched to 3 x 3.5 times in the length and width using a tenter-type simultaneous biaxial stretching machine, and after stretching, they were separated and wound onto two rolls. The stretching conditions at that time were preheating temperature of 140
℃, stretching temperature 115℃, heat setting temperature 210℃, stretching speed
It was 40m/min. No whitening or cutting was observed during stretching, and the performance of the stretched film was as shown in Table 2, and was very good.

[Table] Example 2 A copolymer of 90% polyε-capramide and 10% polyhexamethyleneazibamide was made into a 240% copolymer using an extruder.
℃ and extruded from a T-die onto a cooling roll at 25℃ to form an unstretched film with a thickness of 100μ.
Through the water absorption treatment, 4% by weight of water was absorbed. The same unstretched polyethylene terephthalate resin film as in the comparative example was superimposed on the unstretched film, and the film was simultaneously biaxially stretched 3×3.5 times in the length and width using a tenter-type simultaneous biaxial stretching machine. The stretching conditions at that time were: preheating temperature of 130℃, stretching temperature of 120℃, and heat setting temperature.
The temperature was 190° C. and the stretching speed was 50 m/mm, and no breakage or melt whitening was observed during stretching. The properties of the stretched polyamide resin film and polyester resin film were as shown in Table 3, and were sufficiently durable for practical use.

【table】

Claims (1)

[Claims] 1. When an unstretched film containing 80% or more polyε-capramide resin and an unstretched film containing 80% or more polyethylene terephthalate resin are superimposed and simultaneously biaxially stretched vertically and horizontally using a tenter method, the preheating temperature immediately before stretching is Boeing's improved multi-simultaneous method, characterized in that stretching is performed while maintaining the stretching temperature at 90 to 150°C and the stretching temperature to 100 to 140°C, heat setting is performed at a temperature above the stretching temperature and 230°C or below, and then separation is performed. Stretching method.