JPH09300456A - Polyamide sheet and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyamide sheet capable of being cast at a high speed, having good flexibility and impact resistance and easy to stretch suppressing the crystallization of a non-stretched sheet. SOLUTION: A stretched molding polyamide sheet is characterized by that the total crystallization degree of a non-stretched sheet is below 30% and the γ-type crystallization thereof is 20% or less and produced by extruding a polyamide resin molten at temp. equal to or high than its m.p. (Tm) from a cap and closely bringing the extrudate into contact with a casting drum to cool and solidify the same to form a sheet. In this case, the molten resin is cooled to a temp. range from temp. falling crystallization start temp. (Tcb) to Tm+30 deg.C to be extruded from a cap and electrostatic force is applied to the molten body to bring it into close contact with the casting drum to cool and solidify the same. By this constitution, the crystallization of the non-stretched sheet is suppressed and high speed casting is possible and stretching becomes easy.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyamide sheet and a method for producing the same, and more specifically, to a polyamide sheet which suppresses crystallization of an unstretched polyamide sheet, enables high speed casting, and is easily biaxially stretched. The present invention relates to a manufacturing method thereof.

[0002]

2. Description of the Related Art Stretched polyamide sheets made of poly ε-caprolactam, polyhexamethylene adipamide, etc., have flexibility, impact resistance, tensile strength, pinhole resistance,
It is widely used for food packaging because it has excellent heat and cold resistance and oxygen and other gas barrier properties. Further, as a stretching method of these sheets, a tubular method, a simultaneous biaxial stretching method from a crystal orientation characteristic of polyamide,
Alternatively, it is produced by a sequential biaxial stretching method under special conditions (Japanese Patent Laid-Open No. 61-283527, Japanese Patent Laid-Open No. 61-17729, etc.) and the like.

However, in the tubular method, uneven thickness is likely to occur, and in the simultaneous biaxial stretching method, there is a problem that productivity is lowered because the apparatus is expensive and it is difficult to increase the speed. Also, a special sequential biaxial stretching method,
That is, in the method of the invention disclosed in the above-mentioned published patent, the stretching conditions are extremely regulated, which causes a problem of inferior productivity. Therefore, as a stretching method of a polyamide sheet, a sequential biaxial stretching method of stretching in the longitudinal direction and then stretching in the transverse direction is often used.

Further, as a casting method for obtaining an unstretched polyamide sheet for carrying out this sequential biaxial stretching, the surface temperature of the casting drum is kept at 100 to 140 ° C., the polyamide melt extruded from the die and the casting drum. High temperature casting method (JP-A-53-16067) for improving the adhesion with the casting method, or a casting method with an air knife for fixing the casting position by the dynamic pressure of air to bring the melt into close contact with the casting drum,
Further, an electrostatic application method (SI cast method) is used in which the melt and the casting drum are brought into close contact with each other by electrostatic force.

However, in the above-mentioned casting method,
In the high temperature casting method, thermal crystallization of the molten sheet occurs on the surface of the drum, necking occurs during subsequent stretching in the longitudinal direction, and in the air knife method, the adhesion between the molten material and the casting drum is increased. There are problems such as unstretched sheets that are difficult to stretch due to an increase in crystallinity caused by insufficientness, and a limit in casting speed. Further, in the SI cast method, since polyamide is a resin having a high electric conductivity, there is a problem that it is difficult to increase the casting speed, and it has been obtained only under conditions of extremely low productivity.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and facilitates successive biaxial stretching without impairing properties such as excellent flexibility and impact resistance, and has good productivity. The purpose is to provide an unstretched sheet.

[0007]

That is, according to the present invention, the total crystallinity of the unstretched sheet is less than 30%, and γ
The present invention relates to a polyamide sheet for successive biaxial stretching, which has a mold crystallinity of 20% or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

In the present invention, polyamide is a general term for polymers having an amide group in the molecular chain and may be either aliphatic polyamide or aromatic polyamide.

Typical polyamides include nylon 6, nylon 66, nylon 610, nylon 11, nylon 12, polyethylene isophthalamide, polymethaxylene adipamide, poly (hexamethylene isophthalamide / terephthalamide), poly ( (Hexamethylene terephthalamide / monomethyl terephthalamide), a copolymer of hexamethylene isophthalamide / terephthalamide and ε-caprolactam, a copolymer of hexamethylene terephthalamide and hexamethylene adipamide and the like can be used. Of course, these may be used alone, or may be a mixture of two or more components.

In the present invention, a case where nylon 6 is used as a typical example of polyamide will be described by taking an example. As for the viscosity of the polyamide used in the present invention, the relative viscosity [ηr] in 98% sulfuric acid of 2 to 7, preferably 3 to 6, is suitable from the viewpoint of sheet formability and mechanical strength. If the relative viscosity is higher than this range, film-forming property is deteriorated, fish eyes are increased, or dimensional stability is deteriorated, which is not preferable.

Further, in the polyamide, various known additives within a range that does not impair the effects of the present invention, such as a heat resistance stabilizer, an oxidation resistance stabilizer, an weather resistance stabilizer, an ultraviolet absorber,
Antistatic agents, organic or inorganic fine particles, pigments, dyes, nucleating agents and the like may be added.

In the present invention, the total crystallinity of the unstretched sheet is less than 30% and the γ-type crystallinity is 20%.
It is necessary that the total crystallinity is 25 or less.
%, And the γ-type crystallinity is preferably 15% or less. When the total crystallinity is 30% or more, intermolecular force becomes very large, excessive stretching stress occurs during stretching, and there is a problem that stretching becomes difficult, which is not preferable. On the other hand, if the γ-type crystallinity exceeds 20%, stretching starts from the γ-type crystal, and necking stretching tends to occur, which is not preferable. The crystalline phase of nylon has a γ structure in which the amide group rotates around the C—N and C—C bonds and shifts from the planar structure to form a bent structure.
Type crystal and α-type crystal having a planar zigzag structure are considered to be only two crystal types. Here, the γ-type crystallinity is the weight% of the γ-type crystal in the molecular structure including the crystalline phase and the amorphous phase. Yes, infrared absorption spectrum at 928 cm ^-1 and 977c
Since the peaks of m ⁻¹ correspond to the characteristic absorptions of the α-type crystal and the γ-type crystal, respectively, they can be determined by measuring this absorbance ratio. Also, here, the total crystallinity is
It is obtained from the density measured by the density gradient tube method.

As a method for producing a polyamide sheet having good stretchability in the present invention, first, it is preferable to melt the polyamide resin at a temperature equal to or higher than the melting point (Tm (° C.)).
If the melting temperature is lower than Tm, problems such as deterioration of product quality due to unmelted matter, retention in the extruder, and clogging of the filter are likely to occur, which is not preferable. Further, the Tm of a polyamide resin can be easily measured by a known method using a differential scanning calorimeter (DSC), but in general, in the case of a polymer material, the Tm is not always observed as one point. , It is observed as a widened peak. Here, as Tm that determines the melting temperature of the resin in the extruder,
Most of the resin is melted at the peak temperature, but the molten resin in the expanded part of the skirt may not be melted and may remain in an unmelted state, so the temperature at the end of the skirt (melting end temperature) is used rather than the peak temperature. To do.

Next, the molten resin is cooled to start crystallization (T
After being cooled to a temperature of not less than (cb (° C.)) and not more than (Tm + 30) ° C., it is extruded from a die, and an electrostatic force is applied to the melt to adhere, cool, and solidify on a casting drum to form a sheet. preferable. At this time, by applying a high voltage to the melt and applying an electrostatic current (SI cast method) in which a current is applied between the melt and the drum, the melt and the casting drum can be brought into close contact with each other uniformly. It will be possible. Further, as the casting speed increases, a higher SI current flows, which is effective for high-speed casting.
Examples of the shape of the electrode for the electrostatic application include a wire electrode and a knife electrode. However, it is preferable to use the wire electrode from the upper limit speed of occurrence of application spots. Also, as the material, a tungsten wire of 0.08 to 0.15 mm is used, a DC voltage of 5 to 20 kV, and a current of 3 to 5 mmA.
Therefore, it is preferable that the film is used while being constantly wound during film formation.

Further, polyamide has a problem that it is difficult to apply static electricity because polyamide has a very low melting specific resistance and thus has too high electric conductivity. However, as a result of intensive studies by the present inventors, the temperature of the polyamide melt extruded from the die (T
It was found that out) should be set to a temperature of (Tm + 30) ° C. or lower. By extruding at such a low temperature, the melting specific resistance becomes 1 × 10 ⁶ Ω · cm or more, and the adhesion with the casting drum can be improved. Further, the melting specific resistance can be increased by setting Tout to a temperature lower than usual, but it is not necessary to simply lower the temperature. If it is lower than Tcb, crystallization of the polymer starts and It solidifies and cannot be extruded. Further, at a temperature at which Tout exceeds (Tm + 30) ° C., electrostatic melting cannot be applied, resulting in problems such as insufficient adhesion with the casting drum and generation of a modified polymer. . Therefore, the temperature of the melt extruded from the die is Tcb or higher, (Tm + 30) ° C.
The following temperatures are preferred.

Further, the melt is heated to Tc from the above-mentioned die.
Melt extrusion method of extruding at a temperature lower than usual, that is, not lower than b and not higher than (Tm + 30) ° C. (hereinafter abbreviated as “low temperature extrusion method”)
And the SI cast method are preferably used together, which makes it possible to obtain an unstretched sheet having a total crystallinity of less than 30% and a γ-type crystallinity of 20% or less.

On the other hand, an unstretched sheet obtained by another casting method with only the melt extrusion method as the low temperature extrusion method has a low melting temperature of the resin at the time of extrusion and has a high melt viscosity, so that crystallization occurs, and When the SI casting method is used only as the casting method by using another melt extrusion method, the melting temperature is too high to apply electricity and electrostatic application becomes impossible, or the temperature of the molten resin is too low to extrude. Problems such as being impossible occur, and an unstretched sheet satisfying the total crystallinity and γ-type crystallinity of the present invention cannot be obtained. However, when the low temperature extrusion method and the SI cast method are used together, the total crystallinity is 3
Is less than 0%, and the γ-type crystallinity is 20% or less,
An unstretched sheet having good stretchability that does not cause problems such as necking during stretching can be obtained. Further, by using the above method in combination, the SI casting method is used, and the casting speed can be increased, which is preferable. The speeding up here means that stable casting can be performed at 60 m / min or more.

Further, in the present invention, the melting specific resistance of the polyamide resin when extruded from the die is 1 × 10 ⁶ Ω · cm.
It is preferably 1 × 10 ⁹ Ω · cm or less,
More preferably, 1 × 10 ⁷ Ω · cm or more, 1 × 10 ⁸
Ω · cm. If the melting specific resistance is less than 1 × 10 ⁶ Ω · cm, the electrical conductivity will be too high and electricity will be applied during electrostatic application, and if it exceeds 1 × 10 ⁹ Ω · cm, the electrical conductivity will decrease. Therefore, the adhesion to the casting drum becomes insufficient, which is not preferable. At this time, the surface roughness of the drum is preferably 0.2 s or less, and a chrome-plated finish such as hard chrome plating or amorphous chrome plating is used for long-term stable casting, reproducibility, and economical efficiency. preferable. Further, it is most preferable to set the casting drum temperature to a temperature not higher than the glass transition point (Tg) of the polyamide resin in order to suppress the crystallization of the resin.

In the present invention, it is preferable that the polyamide sheet for molding is successively biaxially stretched so that the characteristics of the sheet can be exhibited.

As the stretching method, for example, the unstretched polyamide sheet is 40 to 90 ° C, preferably 50 to 80 ° C.
At a stretching speed of 10 ⁴ to 10 ⁶ % / min, preferably 5 × 10 ⁴ to 2 × 10 ⁵ % / min in the longitudinal direction by 2 to 5 times,
It is preferably stretched 3 to 4 times and then cooled as quickly as possible to obtain a uniaxially stretched film. This stretching in the longitudinal direction is preferably performed between two pairs of nip rolls having different peripheral speeds in the heating zone. This uniaxially stretched film is 60 to 140
C., preferably 80 to 125.degree.
Stretch 5 times. After this, 180-220 ℃ if necessary
The heat treatment may be performed for 0.5 to 10 seconds.

Next, the manufacturing method of the present invention will be specifically described, but the invention is not limited to such an example.

After sufficiently drying nylon 6 having a relative viscosity of 3.2 under reduced pressure heating, Tm was obtained by rotating a screw heated in an extruder using a conventional melt extruder, for example, a single-screw or twin-screw extruder. The resin is melted at the above temperature, the molten resin sent from the extruder is passed through a heated flow pipe (polymer pipe), and the resin is passed through a filter to remove foreign matters and denatured polymer, and then guided to a die. At this time, if necessary, a gear pump may be provided to improve the quantitative supply property.

Here, the melting specific resistance of the polyamide resin extruded from the die is 1 × 10 ⁶ Ω · cm or more and 1 × 10 ⁹ Ω ·
The temperature of the resin is Tcb to (Tm +
As a method of controlling the temperature of 30) ° C., for example, a method of providing a heat exchanger between the extruder and the filter to control the temperature of the resin, or a tandem extruder for cooling in the second stage may be used. . Subsequently, the molten resin thus obtained is extruded from a T-die die, and while the crystallization of the molten sheet is suppressed by a cooled casting drum, the molten resin is adhered and solidified by electrostatic force on the casting drum to obtain a total crystal. An unstretched sheet having a degree of crystallinity of less than 30% and a γ-type crystallinity of 20% or less is obtained.

The thickness of the polyamide sheet used in the present invention is not particularly limited, and it is usually used in the range of 30 μm to 1 mm.

The polyamide sheet thus obtained was used as 40
Heated to ˜90 ° C., drawn at a draw speed of 10 ⁴ to 10 ⁶ % / min in the longitudinal direction in the heating zone between 2 to 5 times between two pairs of nip rolls with different peripheral speeds, then cooled as soon as possible, Obtain a uniaxially stretched sheet. Next, this uniaxially stretched film is stretched 3 to 6 times in the width direction under heating at 60 to 150 ° C. After this, any treatment such as heat treatment, molding, surface treatment, laminating, coating, printing, embossing, etching, etc. may be performed, if necessary. Further, the surface of the stretched sheet may be subjected to corona discharge treatment or the like.
By coextruding a layer containing an ionic polyelectrolyte on the surface layer of the polyamide thus obtained, a sheet having more excellent humidity stability can be obtained.

[0027]

[Evaluation method of physical properties]

(1) Total Crystallinity The density at 25 ° C. was measured using a density gradient tube composed of carbon tetrachloride and n-heptane, and the total crystallinity was calculated by the following formula.

(D-da) / (dc-da) × 100
(%) However, d: sample density da: amorphous density (1.335 g / cm ³ ) dc: crystal density (1.455 g / cm ³ ) (2) γ-type crystallinity 928 cm obtained by infrared absorption spectrum ^-1 and 9
The γ crystallinity was determined according to the following formula from the absorbance at 77 cm ⁻¹ and the total crystallinity determined by the density gradient tube method.

Vob = Vα · xα + Vγ · xγ + (1-x
α−xγ) · Vax × c = (Va−Vob) / {Va− (Vα · Xα + Vγ ·
Xγ)} xα = Xα · Xc xγ = Xγ · Xc where Xα = 7.58D ⁴ −5.78D ³ −1.87D ² + 3.05D Xγ = 1−Xα D = D ₉₂₈ / (D ₉₂₈ + D ₉₇₄ ) Vob = 1 / D Vα = 0.8127 Vγ = 0.8389 Va = 0.9139 d: Density (g / cm ³ ) of the sample measured at 25 ° C. D ₉₂₈ : Absorbance determined from infrared absorption spectrum at ₉₂₈ cm ⁻¹ D ₉₇₄ : ₉₇₄ cm ⁻¹ (3) Thermal characteristics Seiko Denshi Kogyo's "Robot" DSC-RDC220 was used as a differential scanning calorimeter, and the company's "Disk Station" SSC was used as a data analyzer.
/ 5200 was used to melt and hold about 5 mg of a sample on an aluminum pan at 300 ° C. for 5 minutes, quenching and solidifying with liquid nitrogen, and then heating from room temperature at a heating rate of 20 ° C./minute,
The temperature at the inflection point of the baseline due to the transition from the glass state to the rubber state was Tg, and the temperature was further raised, and the melting end temperature observed at this time was Tm. Also, 3
After raising the temperature to 00 ° C, melt and hold for 5 minutes, cooling rate 20 ° C
The temperature was lowered at a rate of / minute. At this time, the starting temperature of the exothermic peak of the temperature-falling crystallization observed was set to Tcb.

(4) Resin temperature A thermocouple was inserted into the molten resin extruded from the die, and the temperature of the resin was measured.

(5) Melt Specific Resistance 150 g of polyamide resin was vacuum dried at 170 ° C. for 4 hours and then melted under N ₂ atmosphere. Then, a pair of copper electrodes are inserted into the molten resin, and a DC voltage is applied when the resin temperature reaches the target temperature.
I asked.

Ρ = (V × S) / (I × D) However, V: Applied voltage S: Electrode area I: Current value D: Distance between electrodes (6) Sequential biaxial stretchability Melt extrusion from a die, casting drum The sheet-shaped unstretched sheet is stretched 3.2 times in the longitudinal direction by a longitudinal stretching device heated to a roll surface temperature of 60 ° C.,
Subsequently, after preheating to 60 ° C. in a tenter, the stretching condition when visually stretching at a temperature of 110 ° C. in the width direction of 3.6 times was visually observed, and the biaxial stretchability was sequentially determined under the following conditions, In the following state, ◯ was passed and X was not passed.

◯: Necking did not occur during stretching, and the above stretching was possible.

X: Necking occurred during stretching, or breakage occurred during stretching.

(7) Casting upper limit speed and high speed casting property Casting was performed using a casting drum having a diameter of 1 m and having a mirror surface hard chrome plating finish of 0.2 s or less on the drum surface, and air was blown between the molten sheet and the drum. The limit casting speed that does not cause biting was set as the casting upper limit speed, and the high-speed castability was judged under the following conditions.

◯: A cast upper limit speed of 60 m / min or more.

X: The maximum casting speed was less than 60 m / min.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

Example 1 Nylon 6 having a relative viscosity of 3.2 was used. When thermal characteristics were measured using DSC, Tg: 47 ° C., Tm: 223
C, Tcb: 190C. After vacuum-drying the nylon 6 pellets at 170 ° C. for 3 hours, the nylon 6 pellets are supplied to an ordinary melt extruder and melted at a temperature of 280 ° C. Then, the molten resin is cooled in a heat exchanger, and the temperature of 235 ° C. is increased from a T-die die. Melt-extruded at a temperature of 23 ° C., and the surface of the drum cooled to 23 ° C. has a mirror hardness of 0.2 s or less.
An unstretched sheet was obtained at a casting speed of 5 m / min. In addition,
Air entrapment between the molten sheet and the casting drum did not occur up to an upper casting speed of 90 m / min.

The unstretched sheet thus obtained was stretched 3.2 times in the longitudinal direction by means of a longitudinal stretching device which was heated to a roll surface temperature of 60 ° C. Subsequently, after preheating to 60 ° C. in a tenter, stretching at 110 ° C. in the width direction by 3.6 times, and 2% in the width direction.
A heat treatment was performed at 200 ° C. for 8 seconds while performing the relaxation treatment, and after the corona discharge treatment, a biaxially stretched polyamide sheet having a thickness of 15 μm was obtained.

The physical properties of the polyamide sheet thus obtained are shown in Table 1. Both the total crystallinity and the γ-type crystallinity are low, and the adhesion to the casting drum due to electrostatic force is good. Therefore, a stretched polyamide sheet excellent in stretchability and high-speed castability was obtained.

Comparative Example 1 In the same manner as in Example 1, after drying the nylon 6 pellets, the nylon 6 pellets were supplied to an ordinary melt extruder and melted at a temperature of 280 ° C., and then the molten resin was cooled in a heat exchanger to obtain T. 2 from die base
It is melt extruded at a temperature of 35 ° C. and adhered and solidified by electrostatic force on a casting drum cooled to 54 ° C.
An unstretched sheet was obtained at a casting speed of m / min. In addition, the trapping of air between the molten sheet and the casting drum did not occur until the upper limit of the casting speed was 88 m / min.

Using the unstretched sheet thus obtained, a biaxially stretched polyamide sheet was obtained in exactly the same manner as in Example 1.

The physical properties of the polyamide sheet thus obtained are as shown in Table 1, and the maximum casting speed is 88 m.
/ Min, which was excellent in high-speed castability, but compared with Example 1, the casting drum temperature was Tg of 4 or less.
Since it was as high as 7 ° C. or higher, the total crystallinity and the γ-type crystallinity were high, necking occurred during stretching, and the stretchability was deteriorated.

Example 2 In the same manner as in Example 1, after drying the nylon 6 pellets, the nylon 6 pellets were fed to an ordinary melt extruder and melted at a temperature of 279 ° C., and then the molten resin was cooled in a heat exchanger to obtain T 2 from die base
It is melt extruded at a temperature of 00 ° C., and adhered and solidified by electrostatic force on a casting drum cooled to 25 ° C.
An unstretched sheet was obtained at a casting speed of m / min. In addition, the trapping of air between the molten sheet and the casting drum did not occur until the upper limit of the casting speed was 87 m / min.

Using the unstretched sheet thus obtained,
A biaxially stretched polyamide sheet was obtained in the same manner as in Example 1.

The physical properties of the polyamide sheet thus obtained are as shown in Table 1. Compared with Example 1, the temperature at the time of melt extrusion is 35 ° C. lower, so the melt specific resistance is somewhat higher, A stretched polyamide sheet that does not affect the adhesion between the molten sheet and the casting drum when static electricity is applied, has excellent high-speed castability, and has excellent stretchability due to low total crystallinity and low γ-type crystallinity. Was obtained.

Comparative Example 2 In the same manner as in Example 1, after drying the nylon 6 pellets, the nylon 6 pellets were supplied to an ordinary melt extruder and melted at a temperature of 281 ° C., and then the molten resin was cooled in a heat exchanger to obtain T. 1 from die base
When melt extrusion was performed at a temperature of 87 ° C., the temperature at the time of melt extrusion was 190 ° C. or lower of Tcb, so that the resin solidified and the extrusion became impossible.

Example 3 In the same manner as in Example 1, after drying the nylon 6 pellets, the nylon 6 pellets were fed to an ordinary melt extruder and melted at a temperature of 281 ° C., and the molten resin was cooled in a heat exchanger to obtain T 2 from die base
It is melt extruded at a temperature of 53 ° C. and is electrostatically contacted and solidified on a casting drum cooled to 24 ° C.
An unstretched sheet was obtained at a casting speed of m / min. In addition, the trapping of air between the molten sheet and the casting drum did not occur until the upper limit of the casting speed was 88 m / min.

Using the unstretched sheet thus obtained,
A biaxially stretched polyamide sheet was obtained in the same manner as in Example 1.

The physical properties of the polyamide sheet thus obtained are as shown in Table 1. Compared with Example 1, the temperature during melt extrusion is higher by 18 ° C. Crystallinity and melting specific resistance are slightly lower, but 88m
It is possible to perform high-speed casting / minute, and it is possible to obtain a stretched polyamide sheet having excellent high-speed castability and stretchability.

Comparative Example 3 In the same manner as in Example 1, after drying the nylon 6 pellets, the nylon 6 pellets were fed to an ordinary melt extruder and melted at a temperature of 280 ° C., and then naturally cooled by passing them through a polymer tube. It is melt extruded at a temperature of 270 ° C. from a die die and fixed on a casting drum cooled to 25 ° C. by a dynamic pressure of air to fix the casting position and adhere to it (air knife method) for 10 m.
An unstretched sheet was obtained at a casting speed of / min. In addition, the trapping of air between the molten sheet and the casting drum did not occur until the upper limit of the casting speed was 15 m / min.

Using the unstretched sheet thus obtained,
A biaxially stretched polyamide sheet was obtained in the same manner as in Example 1.

Physical properties of the polyamide sheet thus obtained are as shown in Table 1. Compared with Example 1, the temperature at the time of melt extrusion was considerably high, so that the sheet was not sufficiently cooled on the casting drum. , Crystallization occurs, necking occurs during stretching, and since the casting method is the air knife method, the adhesion to the casting drum is poor, and the maximum casting speed is reduced to 15 m / min, and high-speed castability is obtained. I couldn't do it.

Comparative Example 4 In the same manner as in Example 1, after drying the nylon 6 pellets, the nylon 6 pellets were fed to an ordinary melt extruder and melted at a temperature of 282 ° C., and then the molten resin was cooled in a heat exchanger to obtain T. 2 from die base
It was melt extruded at a temperature of 72 ° C., and was adhered and solidified on the casting drum cooled to 25 ° C. by electrostatic force.
As can be seen from the physical properties in Table 1, the temperature during melt extrusion is (T
Since the temperature was 250 ° C. or higher of m + 30) ° C., electrostatic application was impossible due to energization.

[0056]

[Table 1]

[0057]

According to the polyamide sheet of the present invention, crystallization of an unstretched sheet is suppressed, high-speed casting is possible, flexibility and impact resistance are also good, and a polyamide sheet which is easily stretched. Is realized.

According to the method for producing a stretch-forming polyamide sheet of the present invention, a stretch-forming polyamide sheet having the above-mentioned characteristics can be easily produced.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // B29K 77:00 B29L 7:00

Claims (4)

[Claims] 1. A polyamide sheet for successive biaxial stretching, wherein the uncrystallized sheet has a total crystallinity of less than 30% and a γ-type crystallinity of 20% or less. 2. When a polyamide resin is melted at a temperature equal to or higher than the melting point (Tm), it is extruded from a die, closely adhered to a casting drum, cooled and solidified to form a sheet, the molten resin is cooled to start crystallization (Tcb). ) And above, (Tm + 3
0) A method for producing a polyamide sheet for stretch-molding, which comprises cooling to a temperature of 0 ° C. or lower, extruding from a die, applying an electrostatic force to the melt to bring it into close contact, cooling, and solidification. 3. A polyamide melt extruded from a die having a melting specific resistance of 1 × 10 ⁶ Ω · cm or more and 1 × 10 ⁹ Ω ·
The method for producing a polyamide sheet for stretch forming according to claim 2, wherein the polyamide sheet is made to have a size of not more than cm. 4. The total crystallinity is less than 30%, and γ
A method for producing a polyamide sheet, which comprises sequentially subjecting a polyamide sheet having a type crystallinity of 20% or less to biaxial stretching.