JPH07332B2 - Method for producing colored thermoplastic resin sheet - Google Patents

Description

The present invention relates to a method for producing a colored thermoplastic resin sheet used as a support for a photographic film such as an X-ray film.

[Background of technology]

For example, in a support for a photographic film such as an X-ray film, a support colored with, for example, a blue-based dye fine powder may be required in order to make the image easy to see during diagnosis with the X-ray film. The colored thermoplastic resin sheet used as such a support is usually manufactured by extruding a mixture of thermoplastic resin chips and dye fine powder, and then biaxially stretching.

As the chips of the thermoplastic resin, powders of a few mm square or columnar small pieces of a few mm are usually used, and fine dye powders are usually fine particles having an average particle size of about 15 to 30 μm. Used. By mixing fine particles of the dye into the thermoplastic resin chips, since the fine particles of the dye adhere to each surface of the thermoplastic resin chips, they are extruded into a sheet shape, and further biaxially stretched, A colored thermoplastic resin sheet is obtained.

[Problems to be solved by the invention]

However, in the production of the colored thermoplastic resin sheet, after the extrusion molding or after the biaxial stretching, that is, after the ordinate stretching and after the abscissa stretching, unnecessary parts of the sheet body are usually removed so that sheet scraps are generated. If such sheet scraps can be utilized, the yield is high and the colored thermoplastic resin sheet can be economically manufactured.

However, while the sheet waste produced after extrusion is usually about several mm in thickness, the sheet waste produced after biaxial stretching, that is, after vertical axis stretching and horizontal axis stretching, is thin, In particular, since the sheet waste generated after the horizontal axis stretching is usually a thin material of about several tens of μm to several hundreds of μm, when a crushed product obtained by crushing this is required as a reusable chip, a thermoplastic resin is used. In the mixing process with the chips and dye fine powder, it may be difficult to mix with high homogeneity, and the resulting thermoplastic resin sheet will have uneven density, resulting in poor quality colored thermoplastic. There is a problem that it becomes a resin sheet.

On the other hand, if the collected sheet waste is crushed and then, for example, semi-melted and processed into almost the same size as the thermoplastic resin chip and used as a reuse chip, highly uniform mixing is achieved. It could be achieved.
However, in such a means for processing sheet waste into almost the same size as the chips of the thermoplastic resin, special equipment such as an extrusion molding machine, a cooling device, and a cutting device is required for that purpose, and therefore the equipment cost is reduced. However, there is a problem that this causes an increase in the running cost. In addition, since it is melted during processing, it causes a decrease in the intrinsic viscosity of the reused chip, which causes a problem that the quality of the obtained colored thermoplastic resin sheet is deteriorated.

[Object of the Invention]

The present invention has been made based on the above circumstances, and an object thereof is to make a colored thermoplastic resin sheet having a uniform concentration even when reusing thin sheet waste generated from a manufacturing process. It is to provide a manufacturing method capable of manufacturing.

[Means for solving problems]

The method for producing a colored thermoplastic resin sheet of the present invention includes a thermoplastic resin chip, a reusable chip obtained by processing a screen after collecting and crushing sheet waste generated from the manufacturing process, and a dye fine powder. And extruding and then biaxially stretching, and the size of the recycled chips obtained from the sheet waste produced after the completion of the biaxial stretching is obtained from the sheet waste produced before the end of the biaxial stretching. As a screen to be used for sheet waste generated after the end of the biaxial stretching step, a smaller diameter than the diameter of the screen used for sheet waste generated before the end of the biaxial stretching step should be used so that it is smaller than the recycled chip It is characterized by using what it has.

According to such a method, with respect to a sheet waste having a relatively small thickness generated after the end of the biaxial stretching step in the manufacturing process, this is crushed and processed by a small aperture screen having a relatively small aperture to obtain the small aperture screen. It is used as a chip to reuse the finely pulverized material that has passed through, and for the sheet waste with a relatively large thickness that is generated before the end of the biaxial stretching step, this is crushed and the diameter is larger than the small diameter screen. The coarse crushed material that has been processed by the caliber screen and passed through the large caliber screen is used as a reusable chip.Therefore, the reusable chip using a fine crushed product has a small thickness, but its size is also small. No, and reusable chips made from coarsely pulverized material have little adverse effect on homogeneity in mixing with thermoplastic resin chips. Therefore, it becomes possible to sufficiently disperse those recycled chips in the mixing process with the thermoplastic resin chips and the dye fine powder, and therefore, the thermoplastic resin chips, the recycled chips and the dye fine powder are dispersed. It is possible to mix with a high degree of homogeneity, and as a result, a colored thermoplastic resin sheet having a uniform density can be obtained without causing density unevenness even when a reusable chip having a small thickness is used.

Further, regarding the sheet scraps generated before the end of the biaxial stretching step, since the large diameter screen is used instead of the small diameter screen, it is higher than the case of using the small diameter screen to make the finely ground product. The processing capacity can be obtained, and the load in the mixing step can be reduced, so that a sufficiently uniformly mixed state can be easily and surely achieved.

Hereinafter, the present invention will be described in detail.

In the present invention, sheet scraps having a relatively small thickness, specifically sheet scraps having an average thickness of 250 μm or less, which are generated after the completion of the biaxial stretching step in the manufacturing process, are crushed to have a caliber Is treated with a small-diameter screen of less than 5 mm and used as a reusable chip of finely pulverized material that has passed through the small-diameter screen, and is produced before the end of the biaxial stretching step, and a relatively large thickness of sheet scrap, specifically For the sheet waste with an average thickness of 250 μm or more, pulverize it and then treat it with a large-diameter screen with a diameter of 5 mm or more, and use the pulverized material that has passed through the large-diameter screen as reusable chips. Reused chips are mixed with thermoplastic resin chips and dye fine powder, extruded and then biaxially stretched to produce a colored thermoplastic sheet.

During the execution of the manufacturing process, after the extrusion molding, after the vertical axis stretching and after the horizontal axis stretching, unnecessary parts of the sheet body are removed, respectively, so that sheet waste is generated. The thickness of the sheet waste produced after extrusion is usually about 1 to 2 mm, and the thickness of the sheet waste produced after the vertical axis stretching is usually about 1 mm.
The thickness is about 0.6 to 1 mm, and the thickness of the sheet waste produced after the transverse stretching is usually about 75 to 175 μm.

In the case of reusing sheet waste generated from such a manufacturing process, in order to investigate what difference occurs in the dispersion state in the mixing process depending on the thickness and size of the sheet waste, the average thickness is 250 μm or less. Of the sheet waste of No. 5 is collected and crushed, and then treated with a screen having a diameter of less than 5 mm, and the finely crushed material that has passed through the screen and the sheet waste having an average thickness of 250 μm or less are collected and crushed. Prepare semi-molten and columnar (a diameter of about 6 mm and a length of about 10 mm) granules, so to speak, mix each of these with thermoplastic resin chips and dye fine powder and disperse them. When an experiment for examining the above was conducted, it was found that when the above-mentioned finely pulverized product was used, the variation of the weight ratio by sampling of 500 cc was within 1% and the uniform dispersibility was high. When using granules
The variation in weight ratio due to sampling of 500cc was as large as about 10%, and the uniform dispersion was low.

Also, when a sheet waste with an average thickness of 250 μm or less was collected, crushed, and then passed through a screen of 5 mm or more, for example, 6 mm, a similar experiment was conducted using a crushed material, and the weight of 500 cc sampling Ratio variation is 2.5
%, And mixing with high uniformity was difficult.

That is, in the case of a pulverized product having a small thickness, it was found that a highly pulverized mixture can be achieved by using a fine pulverized product that has passed through a small-diameter screen having a relatively small diameter as a reusable tip. .

At the same time, the sheet waste produced before the end of the biaxial stretching step in the manufacturing process has a relatively large average thickness, and when reusing such thick sheet waste, it is not necessary to particularly finely grind it. It has been found that even if the coarsely crushed material that has been crushed and then treated with a large-diameter screen having a diameter of 5 mm or more and passed through the screen is used as a reuse chip, a mixture having sufficiently high homogeneity can be produced.

Further, it is also possible to use a small-diameter screen as a finely pulverized product for the sheet scraps produced before the end of the biaxial stretching step, and use this as a reusable chip. Is considerably high, so that the load particularly in the mixing step becomes large, and it is impossible to obtain a high processing capacity as a whole. However, with respect to the sheet waste generated before the end of the biaxial stretching step, the use of the large-diameter screen makes it possible to achieve the intended purpose extremely advantageously without causing such an obstacle.

The coloring concentration of the colored thermoplastic resin sheet is not necessarily limited to an appropriate value as necessary in relation to the application, but is generally 200 to 300 ppm (weight) in the colored thermoplastic resin sheet. The content ratio of the fine dye powder and the usage ratio of the reused chips are selected so that the appropriate value is obtained. Such dye fine powder has an average particle size of 15 to
It is possible to use a powder of fine particles of about 30 μm, and an anthraquinone dye is generally used as the dye, but the dye is not limited to this.

As the thermoplastic resin chip, generally, a few mm square or several mm cylindrical small piece made of polyester resin can be used, but is not limited thereto. Particularly suitable polyester resins are those in which the acid component is mainly terephthalic acid and the alcohol component is mainly ethylene glycol, but other acid components and / or
Alternatively, it may contain an alcohol component. Examples of such other acid component include isophthalic acid, one or more of naphthalenedicarboxylic acid, β-hydroxyethoxybenzoic acid, p-hydroxybenzoic acid, adipic acid, sebacic acid, and the like. Other alcohol components include trimethylene glycol, tetramethylene glycol, hexamethylene glycol, 1,4
One or more of fatty acids, alicyclic or aromatic dioxy compounds such as cyclohexanedimethanol, and polyalkylene glycols such as polyethylene glycol can be mentioned. Preferred polyester resins are those in which at least 80 mol% of the repeating structural units are ethylene terephthalate units.

FIG. 1 is an explanatory view showing an example of a manufacturing process of a colored thermoplastic resin sheet, 1 is a storage tank of thermoplastic resin chips, 2 is a storage tank of dye fine powder, 3 is a storage tank of reused chips, 4 Is a drying mechanism, 5 is a mixing mechanism, 6 is an extrusion molding mechanism, 7 is a vertical axis stretching mechanism, 8 is a horizontal axis stretching mechanism, and 91, 92 and 93 are formed after extrusion molding, vertical axis stretching and horizontal axis stretching, respectively. This is a crushing and classifying mechanism for crushing the sheet waste and further classifying it to obtain reused chips.

In the crushing / classifying mechanism 91, sheet waste generated after extrusion is crushed and processed by a screen having a diameter of about 8 mm to obtain recycled chips as reusable chips, which are, for example, pneumatically transported to the storage tank 3. Further, in the crushing / classifying mechanism 92, the sheet waste generated after the vertical axis stretching is crushed and processed by a screen having a diameter of about 6 mm to obtain the recycled chips as reusable chips, which are, for example, pneumatically transported to the storage tank 3. . And, in the pulverizing / classifying mechanism 93, the average thickness generated after the horizontal axis stretching is 250 μm.
Sheet scraps containing m or less are crushed and treated with a screen having a diameter of less than 5 mm, for example, about 4 mm to obtain a finely crushed product that has passed through the screen, and this is pneumatically transported to the storage tank 3.

The thermoplastic resin chips stored in the storage tank 1 and the reused chips stored in the storage tank 3 are first dried by the drying mechanism 4 and then supplied to the mixing mechanism 5, and together with this, the dye fine particles in the storage tank 2 are mixed. The powder is supplied to the mixing mechanism 5, and the chips of the thermoplastic resin, the reusable chips, and the fine dye powder are mixed.

The thermoplastic resin chips, the recycled chips, and the dye fine powder thus mixed are then supplied to the extrusion molding mechanism 6, and are extruded while being heated and melted into a sheet body. After removing unnecessary portions, the sheet body is longitudinally stretched by the vertical axis stretching mechanism 7, and after the unnecessary portions are removed, it is further stretched horizontally by the horizontal axis stretching mechanism 8 and the unnecessary portions are removed. With a thickness of about 75 ~
A colored thermoplastic resin sheet of about 175 μm can be obtained.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

Example 1 The materials used in this example are as follows.

[Chip A of thermoplastic resin]

Made of polyester resin, the diameter of the circle is about 3 mm and the length is about 3
Thermoplastic resin powder consisting of cylindrical small pieces of mm [reused chip B] Sheet scrap produced after extrusion is crushed and processed with a screen having a diameter of about 8 mm and passed through the screen, The generated sheet waste is crushed and processed by a screen with a diameter of about 6 mm and passed through the screen, and the sheet waste including the average thickness of 250 μm or less generated after the transverse axis stretching is crushed to a diameter of about 4.5 mm.
Mixture with what has been passed through the screen after being processed by a screen of about mm [Dye fine powder C] Dye fine powder made of anthraquinone type dye and consisting of substantially spherical fine particles having a particle size of about 20 μm. Chip A, recycled chip B and dye fine powder C are mixed, extruded and then biaxially stretched,
Thus, a colored thermoplastic resin sheet was produced.

When the density unevenness of this colored thermoplastic resin sheet was examined, the density unevenness with respect to the set density was as low as ± 0.3% or less including the measurement error in any part, and the quality was excellent. The density unevenness was measured by an optical densitometer in the width direction and the length direction of the colored thermoplastic resin sheet.

After the mixing was completed, a part of the mixture before being subjected to the extrusion molding process was taken out and the mixed state was examined. As a result, the reusable chips having an average thickness of 250 μm or less were well dispersed in the whole mixture, and were uniformly dispersed. It was once in a high mixed state.

Example 2 In Example 1, sheet scraps containing reusable chips B having an average thickness of 250 μm or less produced after transverse axis stretching were crushed and treated with a screen having a diameter of about 4 mm. A colored thermoplastic resin sheet was produced in the same manner as in Example 1 except that the sheet that passed through the screen was used.

When the density unevenness of this colored thermoplastic resin sheet was examined, the density unevenness with respect to the set density was as low as ± 0.2% or less in any part, and the quality was excellent.

After mixing was completed, part of the mixture before being subjected to the extrusion molding process was taken out and the mixed state was examined, and it was found that the reused chips with an average thickness of 250 μm or less were well dispersed throughout the mixture. The mixed state was more uniform than in the case of Example 1.

Example 3 In Example 1, the sheet waste including the reusable chip B having an average thickness of 250 μm or less generated after transverse axis stretching is crushed and treated with a screen having a diameter of about 3 mm. A colored thermoplastic resin sheet was produced in the same manner as in Example 1 except that the sheet that passed through the screen was used.

When the uneven density of the colored thermoplastic resin sheet was examined, no uneven density was observed in any part, and the sheet was of excellent quality.

Comparative Example 1 In Example 1, the sheet waste containing the reusable chip B having an average thickness of 250 μm or less produced after transverse axis stretching was crushed and treated with a screen having a diameter of about 6 mm. A colored thermoplastic resin sheet was manufactured in the same manner as in Example 1 except that the material passed through the screen was used.

When the density unevenness of this colored thermoplastic resin sheet was examined, the density unevenness with respect to the set temperature was as large as ± 1.5%, and the quality was poor.

〔The invention's effect〕

As described above, according to the method for producing a colored thermoplastic resin sheet of the present invention, for a sheet waste having a relatively small thickness generated after the end of the biaxial stretching step in the production process, it is crushed to have a caliber. With respect to the finely ground material that has been passed through the small-diameter screen and processed into a relatively small small-diameter screen to be reused chips, and for the sheet waste with a relatively large thickness generated before the end of the biaxial stretching step, Crushed, and the coarse crushed product that has passed through the large caliber screen by being processed by the large caliber screen whose caliber is larger than the small caliber screen is used as a reusable chip. Although it has a small size, it does not behave abnormally as a particle because its size is also small. In addition, recycled chips made from coarsely pulverized materials are not compatible with thermoplastic resin chips. For those less adverse effect on the uniformity in the case, their reuse chip,
It becomes possible to sufficiently disperse in the mixing step of the thermoplastic resin chips and the dye fine powder, and therefore it is possible to mix the thermoplastic resin chips and the dye fine powder of the reused chips with high uniformity. As a result, even when using a reusable chip having a small thickness, a colored thermoplastic resin sheet having a uniform density can be obtained without causing density unevenness.

Further, regarding the sheet scraps generated before the end of the biaxial stretching step, since the large diameter screen is used instead of the small diameter screen, it is higher than the case of using the small diameter screen to make the finely ground product. Throughput can be obtained and the load in the mixing step can be reduced, and a sufficiently uniform mixed state can be easily and surely achieved.

In order to obtain recycled chips, it is sufficient to crush the collected sheet waste and classify it using a specific screen, so it is not necessary to make granules, for example, and the recycled chips can be used very economically. Becomes

[Brief description of drawings]

 FIG. 1 is an explanatory view showing an example of a manufacturing process. 1 ... Thermoplastic resin chip storage tank 2 ... Dye fine powder storage tank 3 ... Reused chip storage tank 4 ... Drying mechanism, 5 ... Mixing mechanism 6 ... Extrusion molding mechanism, 7 ... Vertical axis Stretching mechanism 8 …… Horizontal axis stretching mechanism, 91,92,93 …… Grinding and classification mechanism

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tomio Ushioda 1 Sakura-cho, Hino-shi, Tokyo Inside Konishi Roku Photo Industrial Co., Ltd. (72) Inventor, Michio Matsushita 1 Takamichi, Iwazuka-cho, Nakamura-ku, Aichi Prefecture Mitsubishi Heavy Industry Co., Ltd., Nagoya Kikai Seisakusho Co., Ltd. (56) Reference JP-A-57-93118 (JP, A) "Extrusion molding" supervised by Kenkichi Murakami (SHO-60-12-10) Plastics Age P.K. 210-211

Claims (1)

[Claims] 1. A thermoplastic resin chip, a recycled chip obtained by collecting and crushing sheet waste generated from a manufacturing process, and then treating with a screen, and a dye fine powder are mixed and extruded. The size of the reusable chip obtained from the sheet waste produced after the end of the biaxial stretching step is smaller than that of the reusable tip obtained from the sheet waste produced before the end of the biaxial stretching step As described above, the screen used for the sheet scraps generated after the biaxial stretching step has a smaller diameter than the screen diameter used for the sheet scraps generated before the biaxial stretching step ends. And a method for producing a colored thermoplastic resin sheet.