JPH10100231A - Manufacture of thermoplastic resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin sheet which is free from streaks, stripes, irregurality in thickness, etc., by a method wherein a molten state thermoplastic resin sheet extruded onto a surface of a rotary cooling drum from a die is pressed by specifying its temperature and lowered crystallization temperature. SOLUTION: A molten state sheet is stuck close onto a rotary cooling drum 4 by pressure of gas blow out from an air knife 8. Then, the molten state sheet 2 on the surface of the rotary cooling drum 4 is pressed with a touch roll 5. An interval (pressing force) between the rotary cooling drum 4 and the touch roll 5 can be appropriately adjusted according to a range of temperature T of [Tm-70]<=TS<=[Tm+50] and appearance characteristies of a product sheet. As the thermoplastic resin, crystalline polyester satisfying [Tm-180]<=Tc<=[Tm-20] is used. Where, Tm expresses a melting point ( deg.C) of the thermoplastic resin, and Tc expresses a lowered crystallization temperature ( deg.C) of the thermoplastic resin. Values of Tc and Tm mean peaks obtained under conditions of 20 deg.C/mm temperature lowering or temperature raising speed after melting or quenching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thermoplastic resin sheet, and more particularly, to a method for solving the problem of the conventional thermoplastic resin sheet which has a poor appearance on the surface of the sheet. The present invention relates to a method for producing a thermoplastic resin sheet that can also achieve improvement.

[0002]

2. Description of the Related Art Thermoplastic resin sheets and molded products thereof are:
Used for a variety of applications. For example, polyester sheets are excellent in moldability, gas barrier properties, mechanical properties, and the like, and thus are widely used for refrigerator inner boxes, cups, trays, displays, signboards, roofing materials, and the like.

[0003] The thermoplastic resin sheet as described above is usually
The molten thermoplastic resin sheet extruded from the die is brought into close contact with a rotary cooling drum and rapidly cooled to obtain a substantially amorphous thermoplastic resin sheet. However, when the raw material resin is a crystalline thermoplastic resin or when a thick thermoplastic resin sheet is manufactured, there is a problem that streaks or stripes are generated on the surface of the obtained product sheet.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide streaks, stripes,
An object of the present invention is to provide an industrially advantageous method for producing a thermoplastic resin sheet having good appearance without thickness unevenness.

[0005]

Means for Solving the Problems The present inventors have made various studies to achieve the above object, and as a result, the above object can be easily achieved by applying specific means in combination. Thus, the present invention was completed.

That is, the gist of the present invention is that a molten thermoplastic resin sheet extruded from a die onto the surface of a rotary cooling drum is brought into close contact with the surface of the rotary cooling drum by the pressure of a gas flow blown from an air outlet of an air knife. And then pressing the molten thermoplastic resin sheet on the surface of the rotary cooling drum with a rotatable touch roll.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an explanatory side view showing an example of a sheet forming apparatus used in the manufacturing method of the present invention. In the method for producing a thermoplastic resin sheet (hereinafter abbreviated as a sheet) of the present invention, a molten sheet (2) extruded from a die (1) onto the surface of a rotary cooling drum (4) is converted into a rotary cooling drum (4). Adhering and then the resulting product sheet (3)
Is separated by a peeling roll (7) in the same manner as in the conventional manufacturing method.

The feature of the present invention is that the air knife (8) and the rotatable touch roll (5) are combined with the conventional method described above. That is, the air knife (8) and the touch roll (5) are sequentially arranged near the rotary cooling drum (4), and the molten sheet (2) is rotated by the pressure of the gas flow from the air knife (8). 4) After being brought into close contact with the surface, it is pressed with a touch roll (5).

In a preferred embodiment of the present invention, the air knife (8) is arranged near the rotary cooling drum (4) where the molten sheet (2) comes into contact first, and the touch roll (5) is an air knife. It is arranged near the rotary cooling drum (4) close to (8). In addition, in order to press effectively with the touch roll (5), the molten sheet (2) immediately before pressing on the surface of the rotary cooling drum (4)
The temperature [T] of (portion A in FIG. 1) is set within a specific range.

First, in the present invention, the molten sheet (2) is brought into close contact with the rotary cooling drum (4) by the pressure of the gas flow blown from the air outlet of the air knife (8). Next, in the present invention, the molten sheet (2) on the surface of the rotary cooling drum (4) is pressed by the touch roll (5).

In the present invention, by applying the close contact operation with the air knife (8) and the pressing operation with the touch roll (5) in combination as described above, high-speed operation is realized as will be described later in the embodiments. Even in the extrusion, the cyclic thickness unevenness of the molten sheet (2) is suppressed, and the product sheet (3) having excellent appearance characteristics can be obtained.

In the present invention, in order to perform the above pressing operation more effectively, the temperature [T] of the molten sheet (A in FIG. 1) immediately before pressing by the touch roll (5) is expressed by the following formula (T). It is preferable to satisfy I).

[0013]

[Tm−70] ≦ T ≦ [Tm + 50] (I) (where Tm represents the melting point (° C.) of the thermoplastic resin).

There is a close relationship between the above temperature range and the appearance characteristics of the product sheet (3). That is, when the temperature [T] is lower than [Tm-70], the pressing effect may not be exerted. When the temperature is higher than [Tm + 50], the pressing effect is reduced, so that a product sheet having excellent appearance characteristics is obtained. (3) may not be obtained. A more preferable temperature [T] is in the range of [Tm-50] to [Tm + 30], and a particularly preferable temperature [T] is [Tm-40] to [Tm + 1].
0].

The distance (pressing force) between the rotary cooling drum (4) and the touch roll (5) is not particularly limited, but can be appropriately adjusted according to the temperature [T] range and the appearance characteristics of the product sheet (3). I can do it. The surface temperatures of the rotary cooling drum (4) and the touch roll (5) are generally in the range of 10 to 60C, preferably 20 to 50C. It is preferable in operation that the touch roll (5) can be driven to rotate.

The surface materials of the rotary cooling drum (4), the touch roll (5) and the peeling roll (7) are selected to be those that can be used for a long time. Such materials include hard chrome plating and ceramic coating. And Teflon coat. The surface may have either a mirror finish or a rough finish.

The air knife (8) includes a high-pressure gas (83),
It is composed of a pair of straightening plates (82) and an air outlet (81). The type and temperature of the high-pressure gas (83) are not particularly limited. For example, an inert gas may be used in addition to air,
The temperature of the gas stream may be near the melting point of the thermoplastic resin.

However, the gas flow blown out from the air outlet (81) is adjusted to be uniform in the width direction of the molten sheet in order to prevent uneven contact of the molten sheet.

The current plate (82) may be made of any material as long as it has a small elastic deformation with respect to the gas flow. Its structure is such that the gas flow uniform effect can be maximized. In particular, it is designed to be uniform over the width direction of the molten sheet. The interval between the current plates (82) can be adjusted by an appropriate adjusting mechanism. The position, distance, angle, etc., of the gas flow from the air knife (8) can also be adjusted as appropriate.

Examples of the thermoplastic resin include polyesters, polyester ethers, polyamides, polycarbonates, polyester carbonates, polysulfones, polyether sulfones, polyetherimides, and polyolefins. Examples of polyolefins include ethylene, propylene, butene, 4-methylpentene-1 and the like.

Among the above thermoplastic resins, polyesters are particularly preferred. Examples of the polyesters include polyesters obtained using aromatic dicarboxylic acid or its ester and glycol as main starting materials.
As the aromatic dicarboxylic acid component, terephthalic acid is typically cited as a typical example.
6-naphthalenedicarboxylic acid, isophthalic acid, phthalic acid, oxycarboxylic acid (for example, p-oxyethoxybenzoic acid) and the like. Preferred aromatic dicarboxylic acids are terephthalic acid or 2,6-naphthalenedicarboxylic acid.

On the other hand, as the glycol component, ethylene glycol is usually mentioned as a typical example, and other examples include diethylene glycol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, propylene glycol, 4-butanediol,
1,3-neopentyl glycol, bisphenol A,
Bisphenol S etc. are mentioned. Preferred glycol components are ethylene glycol, diethylene glycol or 1,4-cyclohexanedimethanol.

The above-mentioned thermoplastic resin can be prepared by any polymerization method,
For example, it is produced by melt polymerization, solid state polymerization, or the like. In the case of polyester, known additives, such as stabilizers, particles, lubricants, and antistatic agents, can be used in addition to the esterification or transesterification catalyst and the polycondensation catalyst.
These are added at any stage by a known method.

When the thermoplastic resin is a polyester,
The limiting viscosity of the polyester in the raw material resin, the product sheet and the molded product is usually in the range of 0.50 to 1.3 dl / g, preferably 0.60 to 1.1 dl / g. If the intrinsic viscosity is less than 0.50 dl / g, the resulting product sheet may have poor mechanical properties, particularly impact resistance, and may have poor deep drawability. On the other hand, when the intrinsic viscosity is more than 1.3 dl / g, processing of a product sheet is difficult due to poor melt fluidity, and deep drawability may be poor.

The effect of the present invention is remarkable when a crystalline polyester satisfying the following formula (II) is used as a raw material resin. Because, according to the conventional method, it was difficult to obtain a product sheet having good appearance from crystalline polyester, but according to the present invention, a product having good appearance even when the raw material resin is crystalline polyester You can get a sheet.

[0026]

[Tm-180] ≦ Tc ≦ [Tm-20] (II) (where Tm is the melting point (° C.) of the thermoplastic resin, and Tc is
This represents the temperature crystallization temperature (° C.) of the thermoplastic resin. )

The above values of Tc and Tm are values measured by the evaluation method described in Examples, and are determined by melting or quenching the thermoplastic resin sheet by measurement using a differential scanning calorimeter (DSC). Later, the cooling rate is 20 ° C / min
Alternatively, it means a main peak obtained at a temperature rising rate of 20 ° C./min.

The above thermoplastic resins include, for example, silicon oxide, talc, calcium carbonate, alumina, kaolin,
Known particles such as titanium oxide, carbon black, and barium sulfate, a whitening material, a concealing material, and a coloring material may be added. If necessary, various additives such as an antioxidant, an ultraviolet absorber, a flame retardant, and a lubricant may be appropriately compounded. Further, a known technique of low oligomerization may be applied. In addition, it is preferable to mix the recycled product with the thermoplastic resin raw material not only in terms of cost but also in terms of reduction of waste.

The product sheet in the present invention may be a laminate of two or more layers, and the inner layer may be a product sheet using a recycled product. The product sheet may be subjected to various surface treatments for the purpose of preventing the surface from being damaged or preventing static charge.

In the present invention, the average thickness of the product sheet is not particularly limited, but is preferably 0.5 to 10 m.
m, more preferably 1.0 to 7.0 mm, particularly preferably 2.0 to 7.0 mm. When the average thickness of the product sheet is less than 0.5 mm or more than 10 mm, the effect of improving the appearance of the product sheet may not be obtained.

According to the present invention, not only the appearance characteristics of the obtained product sheet can be improved, but also the productivity can be improved. That is, according to the present invention, since the high-speed gas flow is blown onto the molten sheet by the air knife, the adhesion of the molten sheet to the rotating cooling drum is improved, and the molten sheet on the rotating cooling drum surface is touched by the touch roll. Pressing improves the appearance of the resulting product sheet and increases the rate of melt extrusion of the thermoplastic resin. Specifically, for example, a product sheet having excellent appearance characteristics can be obtained even at a melt extrusion rate of 600 kg / hr or more, and even 800 kg / hr or more.

[0032]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. The measuring methods and definitions of various physical properties and characteristics in the examples are as follows.

(1) Intrinsic viscosity: A 1.00 g sample arbitrarily collected from a product sheet or a molded product was mixed with phenol / tetrachloroethane = 50/50 (weight ratio) mixed solvent 10
It was dissolved in 0 ml and measured at 30 ° C.

(2) Melting point [Tm]: Measurement was performed using a differential scanning calorimeter ("DSC20" manufactured by Seiko Instruments Inc.). A 10 mg sample arbitrarily collected from the sheet was melted in nitrogen at 300 ° C. for 3 minutes, and then rapidly cooled with dry ice. The main quenched product was heated from 20 ° C. under a condition of a temperature rising rate of 20 ° C./min to obtain a main peak temperature [Tm].

(3) Temperature drop crystallization temperature [Tc]: Measurement was performed using a differential scanning calorimeter ("DSC20" manufactured by Seiko Instruments Inc.). A sample of 10 mg arbitrarily collected from the sheet is subjected to a heating rate of 20 ° C./min for 20 to 300 minutes.
After the temperature was raised to 300C, the temperature was maintained at 300C for 3 minutes, and then the temperature was lowered at a cooling rate of 20C / min to obtain a main peak temperature [Tc].

(4) Average thickness of the product sheet: 5 in the width direction
The thickness was measured for each mm, and the average value was determined. The ears of the sheet are not included in the average thickness.

(5) Product sheet temperature: Measured with a radiation thermometer.

(6) Evaluation of appearance of product sheet: The appearance of a 10 m ² sample arbitrarily collected from the sheet was visually observed and evaluated according to the following criteria.

[0039]

[Table 1] ：: The sheet is very beautiful without appearance defects such as streaks, stripes and uneven thickness on the surface of the sheet. ×: The above-mentioned poor appearance is remarkably not practical. Δ: Intermediate between the above-mentioned ○ and ×.

Example 1 In an esterification reactor, 87 parts of terephthalic acid and 65 parts of ethylene glycol were esterified at 250 ° C. under normal pressure in the presence of 100 parts of bis (β-hydroxyethyl) terephthalate oligomer. Was done. Five hours after the start of the reaction, a polyester oligomer having an esterification rate of 96% was obtained.

To this reaction system were added 0.012 parts of ethyl acid phosphate, and 0.08 parts of magnesium acetate tetrahydrate and 0.04 parts of antimony trioxide were added.
The temperature was gradually increased from 20 ° C. to 285 ° C., and the pressure was gradually reduced from normal pressure to 1 mmHg.
Polycondensation reaction was performed for 4 hours and 45 minutes under the condition of Hg to obtain a polyester (PET).

Next, the above PET was heated at 160 ° C. under vacuum.
For 4 hours, using a vented extruder, performing melt extrusion at a resin temperature of 290 ° C., and treating with a sheeting apparatus shown in FIG. 1 to obtain a 2.0 mm thick flat PET sheet. Was. At this time, an air flow substantially at room temperature was used for the air knife, and the temperature of the rotary cooling drum (4) and the temperature of the touch roll (5) were both 40 ° C. Table 2 shows other production conditions and the evaluation results of the PET sheet. A very beautiful transparent PET sheet having excellent appearance characteristics was obtained.

Example 2 In Example 1, the polycondensation reaction time was 4 hours and 30 minutes, and the amount of titanium oxide particles in which the concentration became 10% by weight was kneaded with PET using a twin-screw kneading extruder. This titanium oxide particle-containing PET and raw material PET were
% By weight, and a PET sheet was obtained in exactly the same manner as in Example 1 except that a white PET sheet having a flat surface and a thickness of 3.0 mm was obtained. Other manufacturing conditions and P
Table 2 shows the evaluation results of the ET sheet. A very beautiful white PET sheet having excellent appearance characteristics was obtained.

Comparative Example 1 A PET sheet was obtained in the same manner as in Example 1 except that the touch roll (5) was not used.
Table 2 shows the manufacturing conditions and the evaluation results of the PET sheet.
Streaks, stripes and uneven thickness frequently occur on the surface of the PET sheet,
A practically usable PET sheet could not be obtained.

Comparative Example 2 A PET sheet was obtained in the same manner as in Example 1 except that the air knife (8) was not used. Table 2 shows the manufacturing conditions and the evaluation results of the PET sheet. P
Streaks and stripes frequently appear on the surface of the ET sheet, P
No ET sheet was obtained. In addition, although the position of the rotary cooling drum (4) and / or the position of the touch roll (5) was changed, a PET sheet with good appearance was not obtained.

[0046]

Table 2 Example Comparative Example 1 2 1 2 <Sheet Material and manufacturing conditions> PET (wt%) 100 99 100 100 Titanium oxide (wt%) 0 100 Temperature of sheet in FIG. 1A [T] (° C.) 259 258 −− <Physical properties of sheet> Intrinsic viscosity ( dl / g) 0.7 0.6 0.7 0.7 Melting point [Tm] (° C) 254 253 254 254 Temperature drop crystallization temperature [Tc] (° C) 181 183 181 181 Thickness (mm) 2.0 3.0 2.0 2.0 Sheet appearance ○ ○ × × ─ ───────────────────────────────────

[0047]

According to the method for producing a sheet of the present invention, the appearance characteristics of the sheet can be significantly improved without impairing other characteristics,
This is a revolutionary method with excellent productivity. The method of the present invention is applicable to any method for producing a thermoplastic resin sheet, and its industrial value is extremely high.

[Brief description of the drawings]

FIG. 1 is an explanatory side view showing an example of a sheet forming apparatus used in a manufacturing method of the present invention.

[Explanation of symbols]

1: Die 2: Melt sheet 3: Product sheet 4: Rotary cooling drum 5: Touch roll 7: Peeling roll 8: Air knife 81: Air outlet 82: Rectifier plate 83: High pressure gas A: Immediately before pressing with a touch roll Part of the molten sheet of

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshitaka Nakayama 347 Inoguchi, Inaguchi, Yamato-cho, Sakata-gun, Shiga Die Ahoil Hoechst Co., Ltd.

Claims (4)

[Claims] 1. A molten thermoplastic resin sheet extruded from a die onto the surface of a rotary cooling drum is brought into close contact with the surface of the rotary cooling drum by the pressure of a gas flow blown from an air outlet of an air knife, and then the rotary cooling is performed. A method for manufacturing a thermoplastic resin sheet, comprising pressing a molten thermoplastic resin sheet on a drum surface with a rotatable touch roll. 2. The method according to claim 1, wherein the temperature [T] of the molten thermoplastic resin sheet immediately before pressing with a touch roll satisfies the following formula (I). [Tm−70] ≦ T ≦ [Tm + 50] (I) (where Tm represents the melting point (° C.) of the thermoplastic resin). 3. The method according to claim 1, wherein the thermoplastic resin is a crystalline polyester satisfying the following formula (II). [Tm-180] ≦ Tc ≦ [Tm-20] (II) (where Tm is the melting point (° C.) of the thermoplastic resin, and Tc is
This represents the temperature crystallization temperature (° C.) of the thermoplastic resin. ) 4. The method according to claim 1, wherein the average thickness of the thermoplastic resin sheet after being pressed by the touch roll is 0.5 to 10 mm.