JPS61197220A - Manufacture of thin cylindrical molded material made of polyester - Google Patents

Abstract

PURPOSE:To manufacture a thin cylindrical molded material whose surface is smooth, by a method wherein after a preform has been made to expand through blowing within a mold, an inside shape of which has no split part and is in a cylindrical state, in an axial and circumferential directions, a molded article is unloaded by making the same shrink by heat within the mold. CONSTITUTION:A preform 1B heated at the orientation temperature is set within a mold 7 an inside shape of which has no split part and is in a cylindrical state. The preform is stretched by a stretching rod 5 in an axial direction, and made into a cylindrical molded material 2A by blowing compressed air within the preform. After said molded material 2A has been made to shrink through heat by keeping a mold at the temperature of more than the polyester glass point, the same is unloaded through the mold 7. Polyester shall be an article having intrinsic viscosity of more than 0.5. As the molded material is unloaded after heat shrinkage has been made to perform, a scratchless and thin cylindrical material is obtained. The titled material can be used for a carrier for a high density magnetic recording material.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing a thin cylindrical molded article made of polyester, and more specifically, it has a smooth surface, a thin wall and a uniform thickness distribution, The present invention relates to a method for producing a thin cylindrical molded body made of polyester and used as a carrier for a recording element.

<Prior art> Conventionally, as a method for manufacturing thin cylindrical molded bodies made of polyester, the so-called inflation molding method
A method in which a tubular preform obtained by extrusion is stretched and expanded between a supply roll and a take-up roll (Japanese Patent Publication No. 32080/1980) is known.

However, since the molded product obtained by this method is obtained in a flat folded state, the crease marks become a defect and it cannot be used as a carrier for a recording element.

In addition, the unfolded portion also becomes a defect due to friction caused by the sizing cylinder during expansion.

In addition, in the method of deep drawing a polyester sheet in a mold with a cylindrical internal shape, the diameter of the opening of the mold is slightly larger than the diameter of the bottom of the mold in order to draw a molded product without scratches from the mold. It is necessary to have a large K, so that the molded product obtained has a shape similar to the side part of a conical body with a slight taper. Such a tapered shape poses a problem when covering with a magnetic recording element layer.

Furthermore, in the method of manufacturing a thin cylindrical molded body by stretching a polyester tube in the axial direction within a mold having a cylindrical internal shape and expanding it in the circumferential direction, taking out the molded body from the mold requires the following steps: The mold is opened and taken out as a split mold, or a mold with a taper is used.

However, in the method of using a split mold, the joint portion of the mold leaves vertical streaks on the molded product, and if a tapered mold is used, this becomes a problem when coating the magnetic recording element layer as described above.

<Objective of the Invention> The object of the present invention is to provide a thin-walled cylindrical polyester carrier useful as a carrier for a recording element, which has a smooth surface free from creases, vertical lines, and scratches, has no taper, and has a uniform wall thickness distribution. An object of the present invention is to provide a method for manufacturing a molded body.

<Structure of the Invention> The present invention provides a polyester resin having a substantially non-oriented and amorphous cylindrical portion, which is composed of polyester having ethylene terephthalate (ethylene terephthalate)+1-main repeating unit and having an intrinsic viscosity of 0.5 or more. When manufacturing a cylindrical molded article by stretching at least the cylindrical part of the reform in the axial direction within a temperature range that allows orientation within a mold having a cylindrical internal shape and blowing it in the local direction, After using a mold without split parts as the mold, and maintaining the temperature of the mold at a temperature higher than the glass transition temperature of the polyester, and shrinking the cylindrical part of the cylindrical molded body within the mold. This is a method for producing a cylindrical polyester molded product, which involves taking out the product.

In the polyester of the present invention, at least 80 moles of repeating units are ethylene terephthalate.

Ester units other than ethylene terephthalate are esters of difunctional acids and glyfur, and examples of difunctional acids include terephthalic acid, inphthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether Aromatic dicarboxylic acids such as dicarboxylic acid, diphenylsulfone dicarboxylic acid, etc.; Alicyclic dicarboxylic acids such as hexahydroterephthalic acid, hexahydroinphthalic acid, etc.; Aliphatic dicarboxylic acids such as adipic acid, sepatic acid, azelaic acid, etc. Examples include oxyacids such as p-β-hydroxyethoxybenzoic acid and C-oxycaproic acid; examples of glycols include ethylene glycol and trimethylene glycol! Tetramethylene glycol, hexamethylene glycol, decamethylene glycol naneneopentyl glycol 9 diethylene glycol, 1,1-cyclohexane dimetatool 91,4-cyclohexane dimetatool.

2.2-bis(4'-β-human p-oxyethoxyphenyl)propane and bis(4'-β-hydroxyethoxy-phenyl)sulfonic acid.

Among these, polyethylene terephthalate is preferred as the polyester of the present invention.

Polyester preform used in the present invention! ! , Specific FK (0-chlorophenol!35℃) is 0.5
That's all. If the intrinsic viscosity is lower than 0.5, crystallization occurs when the preform is heated to the orientation temperature, making it difficult to stretch, or even if it can be formed, the thickness will be uneven. There are drawbacks such as. It is preferable that the intrinsic viscosity is 0.6 or more, more preferably 0.7 or more, since a molded article with excellent stretchability and a uniform wall thickness can be obtained.

Further, although the cylindrical portion of the preform is substantially non-oriented and amorphous, if the preform is in an oriented state, the thickness distribution in the local direction of the obtained molded product will be extremely poor. Moreover, if it is in a crystalline state, it becomes difficult to stretch and expand it. The crystalline state of the cylindrical portion can be determined, for example, by the density of the portion, but preferably the density is 1.3417 cd or less.

The wall thickness of the cylindrical portion of the preform for obtaining the desired thin-walled molded body is preferably 1 mm or less, more preferably 0.2 mm or less.

In the present invention, the polyester preform has a cylindrical internal shape without split portions and is kept at a temperature higher than the glass transition temperature (hereinafter abbreviated as T and f) of the polyester within a temperature range that allows orientation of the polyester preform. The molded product is stretched in the axial direction and expanded by blowing in the local direction in the mold, and then the molded product is contracted in the mold and then taken out from the mold to form a thin-walled cylindrical shape without scratches with the mold. Manufacture the body.

Here, the temperature range in which orientation is possible is a temperature higher than i! degrees at which microp voids are generated during stretching ((so-called cold stretching)), and a temperature at which the degree of orientation is increased by stretch stretching. For example, polyester TF+20℃~TI9+80'
C, preferably 7.9+b.

The stretching magnification is preferably 2 to 5 times in the axial direction, 2 to 5 times in the circumferential direction, and the area magnification (product of the magnification in the axial direction and circumferential direction) is 4 to 16 times, more preferably 8 to 12 times. is within the range of

The mold used in the present invention has a cylindrical internal shape without a split portion, and has no taper with a plurality of arbitrary portions having the same inner diameter. If a split portion is provided for taking out the molded product, the split portion will cause shape defects in the molded product. Further, if a taper is provided, the molded body becomes shaped like the side part of a cone, which becomes a hindrance when covering the molded body with a magnetic recording element layer.

The mold is preferably made of a corrosion-resistant material such as stainless steel, and the cylindrical portion thereof is preferably mirror-finished with precision, and further preferably subjected to hardening treatment such as chrome plating.

In the present invention, by shrinking the stretched/blow-molded molded product in the mold and then taking it out, a molded product without scratches from the mold can be obtained. The mold temperature is adjusted to one or more of the polyesters, preferably TI
I+ 5°C or more and TI + 80°C or less, more preferably TJi'+10'C-T, 9+30°C. If the mold temperature is lower than TJ+, the shrinkage will be insufficient and scratches will occur on the sides of the molded product when it is taken out.

Further, a preferable shrinkage rate (according to the measuring method specified in the examples) is 0.3-5% or less.

More preferably, the content is 0.5 to 2%.

In the present invention, a polyester preform is stretched in the axial direction and expanded by blowing in the local direction.
The method shown in FIG. 4 or FIGS. 5 to 8 is used.

Figure 1 shows that the open end of the bottomed preform (IA) is fitted into the mounting seat (3) and fixed using a presser (4) having a split part, and then the heat insulating material (8
) and has a cylindrical inner wall, the preform (IA) is heated to the stretching temperature.

Figure 2 shows the state in which the preform (IB) heated to the elongation temperature is located inside the metal 11+7) having a cylindrical internal shape with a vent hole (9) after the heater is removed. show. In Figure 3, the preform is stretched in the axial direction KIIA from the stretching rod (5) K, and compressed air (hereinafter abbreviated as compressed air) is blown into the gap between the bracket stretching pud (5) and the mounting seat (3). This figure shows the state in which two shaped bodies have been molded. Figure 4 shows the heated gold IIC7 after removing the compressed air inside the molded body and reducing the internal pressure of the molded body to the same level as the external pressure.
Figure 1 shows a state in which the mold (7) outside the heat-shrinked molded body (' 2 B ) is removed downward and the stretched p-rad (5) is returned to its original position. Furthermore, by opening the split portion of the presser (4), a polyester molded article having a thin cylindrical portion with no scratches can be obtained.

Figure 5 shows that the open end of the preform αυ, one end of which is flattened and closed, is fitted into a mounting vehicle 0 having a pressurized air blowing hole in the center, and the preform Stretching tool α9 for the closed end of αD
This shows a state in which the preform aυ is held and fixed by the cylindrical heater frame having a split part and heated by the cylindrical heater frame having a split part.

FIG. 6 shows that after the preform has been heated to the stretching temperature, the heater 4 is removed from the split part, and the mold (Lη) having a cylindrical internal shape is slid to the preform mounting position. The preform is moved in the axial direction K from the stretching tool ajK.
It shows a state in which the cylindrical molded body (12A) has been stretched by m and compressed air is blown into the center hole of the mounting seat number α to form a cylindrical molded body (12A).

FIG. 7 shows that the pressurized air inside the molded body is removed from the center hole of the mounting vehicle a3, and the mold αη is removed from the position of the thin cylindrical molded body (12B) that has contracted from the heated mold a7) Ic.
Shows the state with removed.

FIG. 8 shows a state in which the split portion of the presser holder 4 is opened and the molded body (12C) is pulled out from the mounting vehicle 3 using a stretching tool. Furthermore, after this, the gripping portion of the stretching tool α9 is opened to obtain a thin cylindrical molded product without scratches.

A bottomed preform having one cylindrical portion is used, but the preform may be formed by injection molding, or one end of a tube obtained by extrusion molding is shown in FIGS. 9 and 10. As shown in FIG.

As shown in Figure 12, one end of the tube may be flattened and fused together.

<Examples> The present invention will be described in detail below with reference to Examples. The conditions for measuring the main characteristic values are as follows.

(1) Intrinsic viscosity C■]: Measured at 35°C using o-liprophenol as a solvent.

(2) Density Cj]: Measured at 30°C in a density gradient tube made from carbon tetrachloride and n-hebutane.

(31 Refractive index [n]: A polarizing plate was attached to an Atsube refractometer, and the refractive index of a sample cut from the cylindrical part of the molded body was measured at 25°C using a sodium D line.

(4) Glass transition temperature (Tg): Measured on an amorphous sample using a runner-type differential calorimeter at a heating rate of 8°C/2. °C (5) Shrinkage rate [S]: Cut the cylindrical molded body in the axial direction, measure the length of one circumference, and calculate the following from the circumference determined from the mold dimensions.

(6) Surface roughness CLA (Center Line Average) According to JI8 BO601, using a stylus type surface roughness meter (Surcom 3B) manufactured by Tokyo Seimitsu Co., Ltd.

Under the conditions of a needle radius of 2 μm and a load of 0.19 N.

Find the roughness curve in the circumferential direction of the compact, cut out a part of measurement length L in the direction of its center line, and create a roughness curve with the center line of this cut out part as the Y axis and the direction of vertical magnification as the Y axis. Na Y =
When expressed as f (x), the value given by the following formula is μm. To measure Φ, set the reference length to 0.25 g, measure 8 pieces, remove 3 fJl from the direction with the largest value, and calculate the average value of the 5 pieces. represent.

Examples 1 to 5 and Comparative Examples 1 to 2 Polyethylene terephthalate with IV=O071 (hereinafter referred to as
PET) chips are dried with hot air at 160℃ for 5 hours,
After setting the moisture content in the chips to o, o o s, and the purity, the cylinder diameter is 40 m1 + cylinder length / cylinder diameter =
22, with a gear pump at the tip to stabilize the discharge, and a stainless steel sintered metal filter (Dynall) to remove foreign matter.
Supply dry chips to an extruder equipped with a tube die (5 sheets of oy
By extruding the tube at ℃ and immediately solidifying it by cooling with water, the outer diameter was 10B.

Wall thickness 0.35. , , amorphous tubes were obtained. The tube + t IV = 0.68 * ”” 1.33 (J
/C1/1) tT#=70°C. Cut the tube into a length of 60 fitll, and attach one end to the 9th
It had a conical side shape as shown in the figure, and was heated to about 180° C. and inserted into a shaping jig to form a tapered open end shape.

Further, another 1 m was heated and bottomed using the bottomed cavity jig (to) and the A plug jig (foundation) shown in Figure 10, and then cooled using a cooling jig with the same shape as Q3. First
A preform (21C) shown in Figure 1 was molded.

The obtained preform had a total length of 55 cm and a cylindrical part length of 3 cm.
It was 5-401111. The preform is shown in Figure 1~
By the method shown in FIG. 4 and under the conditions shown in Table 1, a molded article having a thin cylindrical portion shown in Table 1 was obtained.

The dimensions of the cylindrical part of the mold are inner diameter 36.5w and depth 13011.
No. 11 was used, and the stretching temperature was 110°C.

As is clear from Table 1, the mold temperature PB'IIe
When the Tg is set to 1 or more, and the convergence rate is set to 0.3 or more, sometimes 0.54 or more, the abrasion of the cylindrical part of the molded product with the material is significantly reduced, and the surface roughness of the axillary part is improved. Become good.

The results of measuring various physical properties of the round part of the conical molded body obtained in the fl'1-IK experiment are shown below.

Stretching ratio: Ring direction 3.2 times Circumferential direction 3.7 times Surface tank double standard 11.8 times Thickness: 28μ± 2μ Density:
1.380 tt/? Refraction skewer: ring direction 1.64
12 Circumferential direction IJ165 Thickness direction 1.5050 Tensile breaking strength Biaxial direction 2180 ka/cm" Circumferential direction 2730 # Tensile modulus - Ring direction 42400 # Circumferential direction
48900' Examples 6 to 7 and Comparative Examples 3 to 4 Cylindrical molded bodies were molded in the same manner as in Example 1, except that the PAT chip of Table 2 VC7Fs IV was used.

The results are shown in Table-2.

Example 8 The tube obtained in Example 1 was cut into a length of 8 (lsaa), one end was heated to 160°C, and then crushed flat to obtain a preform as shown in FIG. 12. The preform is axially rotated three times in the manner shown in Figures 5 to 8.
．． A thin cylindrical molded body was obtained by stretching 2 times and 3.7 times in the circumferential direction and expanding by blowing. The molded product obtained in this manner had properties similar to those of Example-1.

Examples 9 to 13 Fracture Examples 7 to 6 Cylindrical molded bodies were molded in the same manner as in Example 1, except that the preform thickness, length, and outer diameter were set as shown in Table 3.

The results are shown in Table-3.

<Effects of the Invention> - As explained above, the cylindrical part of the molded product obtained by the method of the present invention is thin and has a uniform wall thickness distribution, has good f1 surface properties, does not have a Tevanic shape, and is bulky. Can be used as a carrier for density magnetic recording sickle etc. ◎ ′

[Brief explanation of drawings]

FIGS. 1 to 8 are neo-sectional views showing an overview of the stretching and blow molding methods that can be used in the present invention. yX5 diagram~
Figure 8 shows 41! in the case of stretching in the axial direction rather than half-stretching with a stretching tool. This is the essential diagram. Figures 9 and 10 show tubes! Fig. 11 is a cross-sectional view of the preform obtained by this method. Fig. 12: Person B flattens one end of the tube. A front cross-sectional view of a preform which is dovetailed and fused to have a bottom (25
- person) and side cross-sectional view (25-B). Figure 3 Figure 4 Figure 5 Figure 6 Cause 7 Figure 6

Claims (1)

[Scope of Claims] 1. At least a preform comprising a polyester having ethylene terephthalate as a main repeating unit and having an intrinsic viscosity of 0.5 or more and having a substantially non-oriented and amorphous cylindrical portion. When producing a cylindrical molded article by stretching the cylindrical part in the axial direction within a temperature range that allows orientation within a mold having a cylindrical internal shape and blowing it in the circumferential direction, the mold is used as a split part. A polyester comprising: using a mold without a mold, maintaining the temperature of the mold at a temperature higher than the glass transition temperature of the polyester, shrinking the cylindrical part of the cylindrical molded product in the mold, and then taking it out. A method for manufacturing a cylindrical molded body. 2. The method for producing a thin cylindrical polyester molded article according to claim 1, wherein the preform has one end open and the other end fused and bottomed.