JPH0684444B2 - Thermoplastic film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a thermoplastic film having good transparency and slipperiness, and less likely to cause deterioration in quality even after recovery and reprocessing.

[Prior Art] Thermoplastic films are widely used as packaging materials and various industrial materials because they have excellent physicochemical properties and are inexpensive, but in such applications, transparency of the film is required. It is overwhelmingly done.

On the other hand, the ease of handling of the thermoplastic film has a great influence on the quality and yield of the product, and therefore the ease of handling is required in the film manufacturing process and each process of processing the final product. Heretofore, it has been known that it is effective to impart appropriate slipperiness to the film as a means for facilitating the handling of the thermoplastic film. As a method for imparting this slipperiness, a fatty acid ester or a metal called a lubricant is used. There are known a method of incorporating soap and the like into a resin (JP-A-56-139551) and a method of incorporating inert particles called a lubricant into the resin (JP-A-56-55424).

In order to avoid an increase in product cost, it is common for thermoplastic films to collect and recycle the cut film pieces at the final stage of the manufacturing process. It is necessary to prevent the quality of the product film from deteriorating due to the adverse effects of being attached to the film.

[Problems to be Solved by the Invention] When the thermoplastic film contains the above-mentioned lubricant or lubricant, the slipperiness is certainly increased and the handling becomes easy.
On the other hand, the transparency of the film is generally deteriorated. Further, when the cut film pieces were collected and used, these disadvantages seemed to be more remarkable.

However, it is known that a film having excellent transparency can be obtained when silica or alumina silicate fine particles, particularly silica gel fine particles are used among the lubricants. However, even with these relatively good lubricants,
It is not sufficient in the field where higher transparency is required, and when fine particles of silica gel are used, the fineness of the particles occurs during the film recovery and processing stage, and the slipperiness of the recycled film deteriorates significantly. Had.

In view of the above problems, in the present invention, a thermoplastic film having high transparency and slipperiness and capable of maintaining its performance even in a recycled film was examined.

[Means for Solving Problems] The thermoplastic film of the present invention which can solve the above problems has a pore volume of less than 0.1 l / g and substantially no pores, and an average particle diameter. Silica particles having a particle size of 0.1 to 10 μm
The main constitution is to contain 01 to 0.5% by weight, and in order to further improve the transparency of the film, the silica particles are observed under a scanning electron microscope. It is recommended as a preferred embodiment to select a polyester having a value of 90% or more, and to use a polyester composed of ethylene terephthalate units as the main component of the thermoplastic film.

[Action] The thermoplastic film of the present invention contains silica particles as described below, and the action of the silica particles makes the film excellent in transparency and slipperiness. Further, even if the thermoplastic film containing the silica particles is collected and reprocessed, good transparency and slipperiness can be obtained.

The type of the thermoplastic film in the present invention is not particularly limited, but is typically a film made of a thermoplastic resin such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyamide, polyester, and the like. Films composed of copolymers or mixtures of the above are also included. Of these, particularly when applied to a film containing polyethylene terephthalate as a main component, it is preferable because it has excellent transparency and excellent mechanical strength, heat resistance and chemical resistance. These films may be unstretched films or stretched films,
From the viewpoint of mechanical strength and heat resistance, a stretch-heat-fixed film is preferable.

Next, the silica particles contained in the thermoplastic film will be described.

(1) Pore volume: When the pore volume of silica particles is large, for example, when there are many pores such as silica fine powder, the transparency and slipperiness of the film may be different between lots of raw materials. Is known to vary between lots of film and the quality of the film is not stable, and when the film is recovered to obtain a recycled film, the slipperiness of the film is significantly deteriorated. . This is because particles with many pores tend to agglomerate with each other, forming secondary particles and coarse particles of a higher order, and processing conditions when dispersing them into the resin, such as shearing force in the extruder. It is considered that the particle size distribution fluctuates due to such factors. It is also considered that when reclaimed film is obtained, the aggregation and miniaturization of particles further progress during the processing step and the fluctuation of the particle size distribution becomes severe as in the above case. Under such an idea, the present inventors have studied the relationship between the pore volume of silica particles and the slipperiness and transparency of the film. As a result, in order to improve both the slipperiness and transparency of the film, the silica particles With a pore volume of 0.1 ml / g
We have come to the conclusion that it is sufficient to use those of less than, substantially without pores.

(2) Regarding particle size: When the particle size of the silica particles is less than 0.1 μm, the projections formed by the silica particles projecting on the surface of the film are too small to impart sufficient slipperiness to the film. Is 10
When it exceeds μm, the balance between transparency and slipperiness of the film is deteriorated. Therefore, considering both the transparency and slipperiness of the film, the average particle size is 0.1-10 μm, especially 1.5-5 μm.
m is preferable. Further, silica particles have a distribution in particle size, and in order to obtain a film having good transparency and slipperiness, a particle having a particle size of 0.1 to 10 μm and a sharp particle size distribution are used as described above. It is preferable. A measure of the sharpness of the particle size distribution is represented by a degree of variation (%), and a degree of variation of 25% or less, particularly 20% or less is preferable.

(3) Content: The amount of silica particles contained in the film is 0.001 to 0.5% by weight based on the thermoplastic film. If it is less than 0.001% by weight, sufficient slipperiness is not provided, and if it exceeds 0.5% by weight, the transparency becomes poor.

As described above, silica particles having a pore volume of less than 0.1 ml / g and having substantially no pores and an average particle diameter of 0.1 to 10 μm are used.
When the content is 0.001 to 0.5% by weight, the aggregation of silica particles in the polymer is extremely small, and even if a strong shearing force is applied in the film forming process, the particles are hardly made fine. Therefore, there is little variation in the transparency and slipperiness of the product film, and the number of defective products can be significantly reduced. Especially when the recovered film is reused, the quality of the product film does not deteriorate (especially the slipperiness decreases), and a stable quality film can be obtained even if the recovered film and the new raw material resin are arbitrarily mixed. .

Further, the closer the spherical shape of the silica particles is, the easier it is to form effective protrusions on the surface of the film. Therefore, even if the content is close to a true sphere, even if the content is small, a transparent and slippery film can be obtained. . To more accurately express the shape of the “more spherical silica particles”, the circumscribed circle 1 when observed with a scanning electron microscope as shown in FIG.
It can be concluded that those having an area ratio of silica particles 2 of 90% or more are preferable. On this occasion It is defined as

As the silica particles having a substantially spherical shape, there are artificially synthesized substantially spherical silica particles, and the use of the silica particles is effective for improving the transparency and slipperiness of the thermoplastic film, and The closer the particle distribution is to monodisperse, the better, and it is desirable to select and use silica having an optimum shape according to the application. Further, surface treatment of various silica particles can prevent the particles from aggregating, can reduce the generation of voids generated between the resin and the silica particles, and can improve the transparency and physical properties of the film. In order to incorporate the silica particles into the thermoplastic film, a method of adding the silica particles in the initial stage or an intermediate stage of the polymerization step, blending with the resin, or adding and kneading together with the resin in the extruder in the film forming step may be used. is there.

The thermoplastic film of the present invention comprises a lubricant in addition to the silica particles,
Lubricants, heat deterioration inhibitors, light resistance agents, flame retardants, antistatic agents, coloring agents, etc. may be contained. It is also possible to use fine powder of silica gel, which is a silica particle outside the scope of the present invention, or particles of dry process silica together with the silica particles in the present invention.

As a method for producing the thermoplastic film of the present invention, generally, a method of melt-extruding from a slit of an extruder, and cooling and solidifying with a cooling roll as it is or a process of stretching treatment or heat setting treatment and then winding into a roll shape It is taken,
It is not limited to such a film forming method. A multilayer film can also be obtained by adopting coextrusion, but in this case, since the silica particles controlled by the present invention can be contained in only the surface layer to obtain a film having good slipperiness, the silica particles can be provided only in the surface layer. The contained multilayer film also falls within the scope of the present invention. Further, it is preferable to perform rapid cooling and solidification during melt extrusion during film production. This is because if the quenching is insufficient, the film will crystallize and whiten and the transparency will deteriorate. In addition, the solidified film can be subjected to stretching treatment or heat setting treatment, the stretching treatment is effective for improving the mechanical strength of the film, and the heat fixing treatment is effective for improving the dimensional stability of the film at high temperature. Is.

Since the thermoplastic film of the present invention obtained as described above has excellent transparency and slipperiness, it is suitable for packaging films, labels, photographic / printing substrates, display vapor deposition films, gold and silver threads, etc., which require transparency and gloss. It is suitable. Further, since it has excellent slipperiness, it is easy to handle the film at the time of manufacturing or processing, for example, the occurrence of wrinkles can be reduced, and the product yield can be improved. Furthermore, even if it is reprocessed, the deterioration of transparency and slippage is small, so that the recovered film can be easily recycled.

[Examples] Next, examples and comparative examples of the present invention will be described. All parts in the examples mean parts by weight unless otherwise specified.

The measuring method used is shown below.

(1) Measurement of pore volume It was measured by the BET method using nitrogen gas.

(2) Average particle diameter Inactive particles were observed with a scanning electron microscope (Hitachi s-510 type), photographed and enlarged, and further traced to randomly paint 200 particles in black. Using the image analyzer of this image (Luzex 500 type manufactured by Nireco Corporation), the ferret diameter in the horizontal direction was measured,
The average value was defined as the average particle size. The degree of variation in particle size was calculated by the following formula.

(3) Area ratio to the circumscribed circle 20 particles are arbitrarily selected from the trace image used to measure the average particle diameter, and the projected cross-sectional area of each particle is
It was measured by the image analysis device used in (2). In addition, the area ratio was calculated using the following formula by calculating the area of the circle circumscribing these particles.

(4) Transparency of film The film haze was measured by an integrating sphere type haze meter manufactured by Toyo Seiki Co., Ltd. according to JIS K6714. A film having a lower value indicates better transparency.

(5) Sliding property of film According to ASTM D1894, the dynamic friction coefficient was measured by a universal tensile tester manufactured by Shimadzu Corporation. Thread dimensions are 76 x 64 x
25 mm, the friction surface is 48.6 cm ² , and the weight is 238 g. Generally, a film having a lower value has better slipperiness and is easier to handle.

[Production of Polyester Resin Containing Silica Particles] First esterification using a continuous esterification reaction device consisting of a two-stage complete mixing tank equipped with a stirrer, a dephlegmator, a raw material inlet and a product outlet E to TPA (terephthalic acid) to the system where the esterification reaction product of the reactor is present
The molar ratio of G (ethylene glycol) was adjusted to 1.7, and antimony trioxide was used as an antimony atom to give 2 per TPA unit.
An EG slurry of TPA containing 89 ppm was continuously fed.

At the same time, from an inlet other than the EG slurry inlet of TPA, magnesium acetate tetrahydrate EG solution and sodium acetate EG
100 ppm and Na as Mg atom per polyester unit in the reaction product passing through the solution in the reactor
It was continuously supplied so as to be 10 ppm as an atom, and the reaction was carried out at normal pressure at an average residence time of 4,5 hours and a temperature of 255 ° C.

This reaction product was continuously taken out of the system and supplied to the second esterification reaction can. 0.5 parts by weight of EG and EG solution of trimethyl phosphate are 64 ppm as P atoms and EG slurry of silica particles is 2000 ppm as silica with respect to the polyester unit in the reaction product passing through the second esterification reactor. Thus, each is continuously supplied from a separate supply port, and the average residence time is 5.0 hours at normal pressure,
The reaction was carried out at a temperature of 260 ° C. The reaction product of the first esterification reaction vessel had an esterification rate of 70%, and the reaction product of the second esterification reaction vessel had an esterification rate of 98%.

The esterification reaction product is continuously supplied to a two-stage continuous polycondensation reaction device equipped with a stirrer, a dephlegmator, a raw material charging port and a product outlet port to carry out polycondensation, and an intrinsic viscosity of 0.
620 polyester was obtained.

[Production Method of Polyester Not Containing Silica Particles] A polyester resin not containing silica particles was produced by the same method as in the case of the polyester resin containing silica particles, except that the EG slurry of silica particles was not added.

[Film manufacturing method] A polyester resin containing silica particles and a polyester resin not containing silica particles are blended so that the silica particles contained in the film have a predetermined amount, and melt extruded at 290 ° C, and the longitudinal direction at 90 ° C. Then, it was stretched 3.5 times in the transverse direction at 110 ° C. and then heat treated at 220 ° C. to obtain an oriented film having a thickness of 12 μm.

[Manufacturing Method of Regenerated Film] The oriented film obtained above was crushed and pelletized by a compression molding machine, and a regenerated oriented film having a thickness of 12 μm was obtained again under the above film forming conditions.

Examples 1 and 2 The silica particles have an average particle size of 2.
An oriented film was obtained by the above method so that the silica particles having the characteristics shown in Table 1 of 8 μm and 2.0 μm were contained in an amount of 0.080% by weight of the film. Further, a recycled oriented film was obtained from this oriented film. The characteristics of the obtained film and the recycled film using the resin immediately after the polymerization are shown in Table 1.

Comparative Examples 1 and 2 As the silica particles, fine powder having the characteristics shown in Table 1 having a pore volume of 1.4 ml / g, which was conventionally regarded as the most transparent lubricant, was used, and the silica content in the film was , 0.070 each
And an oriented film and a regenerated oriented film were obtained so that the content was 0.080% by weight. The characteristics of each film are shown in Table 1.

The transparency (haze) and slipperiness (dynamic friction coefficient) of the recycled films of Examples 1 and 2 are almost the same as those of the film using the resin immediately after polymerization as a raw material, and Comparative Examples 1 and 2 show the dynamic friction coefficient of the recycled films. It can be seen that it is easier to recycle the recovered film, compared with the increase in. Also in terms of the relationship between transparency and slipperiness, it can be said that the haze is almost the same as that of the comparative example, but the coefficient of dynamic friction is low, which is excellent.

Comparative Example 3 Silica particles having an average particle size of substantially no pores of 0.
An oriented film was obtained by the above-described method so that the film contained 0.08% by weight of silica particles having the characteristics shown in Table 1 of 08 μm. The characteristics of this film are shown in Table 1.
Although this film had good transparency, it had a large coefficient of friction and had wrinkles and was difficult to wind. There were also many fish eyes due to the aggregation of silica.

Comparative Example 4 Silica particles having an average particle size of substantially no pores of 15
An oriented film was obtained by the above method so that the silica particles having the characteristics shown in Table 1 of μm of 0.080 wt% were contained in the film. The characteristics of this film are shown in Table 1.
Although the haze and slipperiness of this film were not significantly different from those of the examples, the transparency was visually observable and the film was not practical.

Comparative Example 5 Example 2 except that the content of silica particles was 0.55% by weight.
An oriented film was obtained in the same manner as in. The haze of this film was 21%, which was poor in transparency, and was not suitable for applications requiring transparency or clear feeling after printing and vapor deposition.

EFFECTS OF THE INVENTION Since the present invention is constituted as described above, the thermoplastic film of the present invention has excellent transparency and good slipperiness. Moreover, even if the film is collected and recycled, there is little deterioration in the performance of transparency and slipperiness.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the area ratio of silica particles to the circumscribed circle. 1 ... circumscribed circle, 2 ... silica particles

Front page continuation (72) Inventor Koichiro Nakamura 10-24 Toyo-cho, Tsuruga-shi, Fukui Prefecture Toyobo Co., Ltd. General Research Institute Tsuruga Branch Office (72) Inventor Osamu Makimura 10-24 Toyo-cho, Tsuruga-shi, Fukui Prefecture Toyobo Co., Ltd. General Research Institute, Tsuruga Branch Office (56) References JP-A-63-105040 (JP, A)

Claims (3)

[Claims] 1. A heat containing 0.001 to 0.5% by weight of silica particles having a pore volume of less than 0.1 ml / g, substantially no pores, and an average particle diameter of 0.1 to 10 μm. Plastic film. 2. The silica particles are observed under a scanning electron microscope. The thermoplastic film according to claim 1, wherein the value defined by is 90% or more. 3. The thermoplastic film according to claim 1 or 2, wherein the main component of the thermoplastic film is a polyester composed of ethylene terephthalate units.