JPH0751635B2 - Method for producing colored thermoplastic resin sheet - Google Patents

Description

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

As the thermoplastic resin chips, a few mm square or a few mm cylindrical small pieces are usually used, and as the dye fine powder, fine particle powder having an average particle size of about 15 to 30 μm is usually used. . Fine particles of the dye are attached to the respective surfaces of the thermoplastic resin chips by mixing the fine powder of the dye with the thermoplastic resin chips, so that these 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, the colored thermoplastic resin sheet used as the support of the photographic film needs to be colored in a uniform density as a whole in order to obtain high quality.

However, depending on the mixing conditions of the thermoplastic resin chips and the fine dye powder, the obtained colored thermoplastic resin sheet has a problem in that the density becomes uneven and the quality becomes poor.

That is, when the ratio of the fine dye powder to the thermoplastic resin chip is excessive, the fine dye powder that is present in a free state without being able to adhere to the thermoplastic resin chip appears (hereinafter also referred to as “free phenomenon”). ), And in some cases, the dye fine powder may agglomerate, and when extruded in such a state, the portion where the dye fine powder was present in a free state is more than the other portions. There is a problem in that the coloring density becomes abnormally high and a part where the density is not uniform occurs.

[Object of the Invention]

The present invention has been made based on the above circumstances, and an object thereof is to provide a manufacturing method capable of obtaining a colored thermoplastic resin sheet colored at a uniform concentration.

[Means for solving problems]

The method for producing a colored thermoplastic resin sheet of the present invention includes a step of mixing a thermoplastic resin chip and a dye fine powder, extruding the mixture, and then biaxially stretching, wherein one of the thermoplastic resin chips is used. The relationship between the surface area ΣA of the entire chip when the average surface area per hit is A and the surface area ΣB of the entire dye fine powder when the average surface area per fine particle of the dye fine powder is B is expressed by the following equation (1) The thermoplastic resin chips and the dye fine powder are mixed under a condition satisfying the condition (1).

Formula (1) ΣB ≦ 3ΣA According to this method, since the chips of the thermoplastic resin and the fine dye powder are mixed at a mixing ratio such that the total surface areas of the chips satisfy the specific conditions, Of the fine particles of Dye fine powder are not detached and adhere to each of the chips of the thermoplastic resin, and as a result, it is avoided that fine particles of the dye fine powder are present in the state of being separated from the chips of the thermoplastic resin. In the colored thermoplastic resin sheet to be obtained, a locally high density portion does not occur, and the sheet is colored with a uniform density.

Hereinafter, the present invention will be described in detail.

In the present invention, the surface area ΣA of the entire chip, where A is the average surface area of the thermoplastic resin chips and the dye fine powder, and one particle of the fine dye powder is used. When the average surface area per hit is B, the surface area ΣB of the entire dye fine powder is mixed under conditions satisfying the above formula (1), and the mixture is extruded and then biaxially stretched, thus giving a colored thermoplastic resin. Manufacture sheets.

As the chip of the thermoplastic resin, usually, a small piece of a few mm square or a few mm columnar made of a polyester resin can be used. As the fine dye powder, fine powder having an average particle size of about 15 to 30 μm can be used.

The coloring density of the colored thermoplastic resin sheet is selected as an appropriate value as necessary in relation to the application, but specifically, it changes depending on the content ratio of the fine dye powder. Therefore, the present inventors, as a colored thermoplastic resin sheet, in the case of obtaining such a content of the dye fine powder is an appropriate value within the range of, for example, 200 to 300 ppm (weight), the entire dye fine powder The surface area ΣB and the surface area ΣA of the entire thermoplastic resin chip are mixed by varying the ratio ΣB / ΣA.
An experiment was conducted to examine whether or not the liberation phenomenon of the dye fine powder occurs, and as shown in FIG. 1, it was found that the liberation phenomenon suddenly occurred when the ratio ΣB / ΣA value exceeded 3. . In other words, by mixing the thermoplastic resin chips and the dye fine powder under the conditions that satisfy the above formula (1),
It is possible to surely attach the entire fine particles of the dye fine powder to each of the chips of the thermoplastic resin without the release phenomenon of the dye fine powder. Note that, in FIG. 1, the release rate on the vertical axis is a value indicating the weight% of the released dye with respect to the input dye.

In order to mix the thermoplastic resin chips and the fine dye powder so as to satisfy the above formula (1), the following may actually be carried out.

That is, when mixing the two in a batch system, the charge amount per batch is W ₀ (kg), the weight of one thermoplastic resin chip is w _a0 (kg), and the entire thermoplastic resin chip is Weight of W _a0 (kg), weight of one fine particle of dye powder w
_b0 (kg), the total weight of the dye fine powder is W _b0 (kg), and when the mixing number of the thermoplastic resin chips and the fine particles of the dye fine powder are n _a0 and n _b0 , respectively, the liberation phenomenon does not occur. The condition is n _a0 · A ≦ 3n _b0 · B from the above equation (1).

If the two are mixed under the condition that n _a0 · A = 2n _b0 · B, then n _a0 = 2n _b0 · (B / A) ... from this equation.

Further, the charged amount per batch is W ₀ = n _a0 · _{wa 0} + n _b0 · w _b0 .

The amount of chips of the thermoplastic resin and the amount of fine dye powder per batch are W _a0 = n _a0 · w _a0 ... W _b0 = n _b0 · w _b0 ... respectively.

Therefore, as a procedure, _obtain n _a0 and n _b0 from the formula and the formula, obtain W _a0 and W _b0 from the formula and the formula, and mix the thermoplastic resin chips and the dye fine powder according to the obtained numerical values. Good.

Also, when mixing both in a continuous system, if the total amount charged per unit time is W ₁ (kg), the amount of chips of thermoplastic resin W per unit time is the same as in the case of the batch system below. _{Since a1} and the dye fine powder amount _Wb1 can be obtained, it is sufficient to continuously mix the thermoplastic resin chips and the dye fine powder according to the obtained numerical values.

Generally, polyester resin or the like can be preferably used as the thermoplastic resin chip, but the chip 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 may also contain other acid components and / or alcohol components. Such other acid components include isophthalic acid,
One or more kinds of naphthalene dicarboxylic acid,
β-Hydroxyethoxybenzoic acid, p-hydroxybenzoic acid, adipic acid, sebacic acid, etc. can be mentioned, and other alcohol components include trimethylene glycol, tetramethylene glycol, hexamethylene glycol, 1,4-cyclohexane. Examples thereof include one or more of fatty acids or alicyclic or aromatic dioxy compounds such as dimethanol and polyalkylene glycols such as polyethylene glycol. Preferred polyester resins are those in which at least 80 mol% of the repeating structural units are ethylene terephthalate units.

As the dye fine powder, generally, anthraquinone dye fine powder can be used, but the dye fine powder is not limited thereto.

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 is selected so as to be an appropriate value within the range.

FIG. 2 is an explanatory view showing an example of a manufacturing process of a colored thermoplastic resin sheet, 11 is a storage tank of thermoplastic resin chips, 12 is a storage tank of reused chips, 2 is a storage tank of fine dye powder, 31 And 32 are drying mechanisms, 41 and 42 are mixing mechanisms, 51
Reference numerals 52 and 52 are extrusion molding mechanisms, and 6 is a biaxial stretching mechanism.

In this example, the thermoplastic resin chips measured under the conditions satisfying the above formula (1) are supplied from the storage tank 11 to the drying mechanism 31 and dried, and then the dried thermoplastic resin chips are mixed with the mixing mechanism. Supplied to 41. Along with this, fine dye powder measured under the condition that satisfies the above formula (1) is supplied from the storage tank 2 to the mixing mechanism 41. The mixing mechanism 41 mixes the thermoplastic resin chips and the fine dye powder.

The thermoplastic resin chips and the fine dye powder thus mixed and processed are then supplied to an extrusion molding mechanism 51, where they are extruded while being heated and melted, and the thickness thereof is usually several.
The sheet body is mm. Then, this sheet is longitudinally stretched by the biaxial stretching mechanism 6 and then transversely stretched, so that the thickness is about 75 to 175 μm and the coloring density is 200 to 300 ppm.
A colored thermoplastic resin sheet having a constant (weight) range can be obtained.

Further, during the manufacturing process, for example, after extrusion molding, after vertical axis stretching, and after horizontal axis stretching, unnecessary parts of the sheet body are usually removed, so that sheet waste is generated. When such sheet waste is reused, for example, crushed sheet waste into an appropriate size is used as a reuse chip, and the reuse chip is stored in the storage tank 12. Then, the recycled chips weighed from the storage tank 12 are supplied to the drying mechanism 31 together with the thermoplastic resin chips from the storage tank 11 to be dried, and then these are supplied to the mixing supply 41 together with the fine dye powder from the storage tank 2. And mixed, and a colored thermoplastic resin sheet is obtained in the same manner.

When a so-called master batch having a coloring concentration exceeding the range of 200 to 300 ppm (weight) is produced, the measured chips of the thermoplastic resin are supplied from the storage tank 11 to another drying mechanism 32 to be dried, and The weighed dye fine powder from the storage tank 2 is supplied to another mixing mechanism 42 together with the dried thermoplastic resin chips to mix them. Next, the mixture is supplied to the extrusion molding mechanism 51 together with the mixture mixed by the mixing mechanism 41 in the same manner as described above, and the colored thermoplastic resin sheet is obtained in the same manner. Alternatively or alternatively, the mixture from the mixing mechanism 42 may be replaced by another dedicated extrusion mechanism 52.
May be supplied to obtain a colored thermoplastic resin sheet.

〔Example〕

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

Example 1 Using the apparatus shown in FIG. 2, a thermoplastic resin chip made of a polyester resin and having a cylindrical diameter of about 3 mm and a length of about 3 mm, and an anthraquinone dye were used. In the mixing mechanism 42, the relationship between the surface area ΣA of the entire thermoplastic resin chip and the surface area ΣB of the entire dye fine powder is ΣB = The mixture was mixed so as to satisfy the condition of satisfying 2ΣA, extrusion-molded, and then biaxially stretched to produce a colored thermoplastic resin sheet.

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 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.

Comparative Example 1 Colored thermoplastic resin was prepared in the same manner as in Example 1 except that the thermoplastic resin was mixed under the condition that the total surface area ΣA of the chips and the total surface area ΣB of the dye fine powder satisfy ΣB = 3.5ΣA. A sheet was manufactured.

When the density unevenness of this colored thermoplastic resin sheet was examined in the same manner as in Example 1, the density unevenness with respect to the set density was as large as about 10%, and the quality was poor. In this example, the density unevenness value (10%) was smaller than the liberation rate value (14%) because the extrusion molding mechanism 51
It is considered that this is because the dye fine powder was dispersed to some extent and averaged.

〔The invention's effect〕

As described above, according to the method for producing a colored thermoplastic resin sheet of the present invention, thermoplastic resin chips and dye fine powder are mixed under conditions such that the total surface area of each satisfies a specific relationship. Therefore, the whole fine particles in the dye fine powder will not be released and will adhere to each of the thermoplastic resin chips, and as a result, the fine particles of the dye fine powder will exist in a state of being released from the thermoplastic resin chips. Therefore, in the obtained colored thermoplastic resin sheet, a locally concentrated high density portion does not occur and is colored with a uniform density, and eventually a high quality colored thermoplastic resin sheet can be produced. it can.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the relationship between the surface area ΣB of the entire dye fine powder and the surface area ΣA of the entire thermoplastic resin chip and the value of the ratio ΣB / ΣA and the release rate of the dye fine powder, and FIG. 2 is the manufacturing process. It is explanatory drawing which shows an example. 11 …… Thermoplastic resin chip storage tank 12 …… Reused chip storage tank 2 …… Dye fine powder storage tank 31,32 …… Drying mechanism 41,42 …… Mixing mechanism, 51,52 …… Extrusion molding mechanism 6 ... Biaxial stretching mechanism

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tomio Ushioda 1 Sakura-cho, Hino-shi, Tokyo Konishi Roku Photo Industrial Co., Ltd. (56) Reference JP-A-56-47438 (JP, A)

Claims (1)

[Claims] 1. A step of mixing a thermoplastic resin chip and a fine dye powder, extruding the mixture, and then biaxially stretching the mixture, wherein the average surface area per chip of the thermoplastic resin is A
Under the condition that the surface area ΣA of the entire chip and the surface area ΣB of the entire dye fine powder where B is the average surface area per fine particle of the dye fine powder satisfy the following formula (1). A method for producing a colored thermoplastic resin sheet, which comprises mixing the thermoplastic resin chip and the dye fine powder. Formula (1) ΣB ≦ 3ΣA