JPH02141225A - Method and device for thermally treating crystalline thermoplastic resin film - Google Patents

Abstract

PURPOSE:To heat-set films without generating fusion under the state of two superposition by executing a first heat treatment stage before a process in which a film is separated into two, and executing the heat treatment of a second stage under the state in which air is interposed between both separate films. CONSTITUTION:A crystalline thermoplastic resin film 1 is folded flatly by a guide plate 2 and pinch rolls 3, and thermally treated at a temperature higher than the shrinkage start temperature of the film 1 and lower than a temperature lower than the melting point of the film 1 by 30 deg.C. Both end sections of the flat film 1 are cut open by a trimming device 6, the film 1 is separated into two films 1A, 1B, melted and separated by rolls 8A, 8B, and forwarded and passed through three fluted rolls 9A-9C, and air is interposed between both films 1A, 1B and both films are superposed again. Both end sections are gripped by a tenter 10 in a second heating furnace 11, and these two films 1A, 1B are thermally treated at a temperature lower than the melting point of the film 1 and higher than a temperature lower than the melting point of the film 1 by 30 deg.C.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention relates to a method and apparatus for heat treating a crystalline thermoplastic resin film biaxially stretched by the tubular method, and is suitable for use in food packaging, packaging of industrial products such as computers, etc. It can be used in fields such as bag-in-boxes, drum interiors, etc.

[Prior Art] After a plastic film is biaxially stretched, for example, by a tubular method, it is heat-treated to fix the orientation of film molecules and obtain dimensional stability.

During this heat treatment, if a tube-shaped film is folded flat and, for example, nylon-6, which is a polyamide film, is heat-treated at around 200℃, the upper and lower films will fuse together, resulting in two pieces after treatment. A problem arises in that it cannot be separated and cannot be used as a product. Such problems are particularly noticeable when the plastic film is a crystalline thermoplastic resin film such as a polyamide film.

Therefore, in order to solve such problems, for example,
A tube method has been proposed in which a tubular film is biaxially stretched, then compressed air is introduced while heating to form bubbles, the film is then folded flat with nip rolls, and heat treated.

Alternatively, after cutting the edges of a biaxially stretched flat tubular film and separating it into two films, the film is introduced into a tenter with a gap maintained between the two films using an endless belt-like object. An open method has been proposed in which heat treatment is performed while holding both ends with clips (see Japanese Patent Publication No. 15439/1983).

[Problems to be Solved by the Invention] According to the above-mentioned tube method, since there is air between the two films, fusion does not occur, but in order to obtain high dimensional stability, temperatures of 180'C or higher are applied. If heat treatment is carried out, a problem arises in that the bubbles oscillate, making stable heat treatment difficult. If heat treatment is performed at a low temperature to avoid this problem, good dimensional stability will not be obtained.

Further, according to the oven method, (1) the intervening device having an endless belt-like material is large-scale, which is disadvantageous in terms of work space and equipment cost; (ii) the film is easily damaged; (iii) ) The mechanism for stably gripping both ends of the film while interposing an endless belt-like object between the two films is complicated; (iv) The gripping mechanism has to be quite sturdy because the shrinkage stress of the film during heat treatment is large. Otherwise, there is a problem that the film will come off the gripping mechanism, making continuous processing impossible.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for heat treatment of crystalline thermoplastic resin films, which can heat-fix crystalline thermoplastic resin films in a stacked state without causing fusion.

[Means for Solving the Problems 1] The method for heat treatment of a crystalline thermoplastic resin film according to the present invention includes a step of folding a crystalline thermoplastic resin film flattened by two-wheel stretching using a tubular method, and initiation of shrinkage of the film. A process of pre-heat-treating this flat film at a temperature above the temperature and no more than 30°C lower than the melting point of the film, a process of cutting both ends of the flat film to separate it into two films, and a process of separating the films into two films. A process of heat-treating the film at a temperature below the melting point of the film and 30'C lower than the melting point of the film while grasping both ends of the overlapped film with air intervening; It is characterized by having a step of winding up the film.

In the above heat treatment method, the first stage heat treatment performed in advance at a temperature not lower than the shrinkage start temperature of the film and 30'C lower than the melting point of the film is preferably performed at a temperature higher than or equal to 20'C higher than the film shrinkage start temperature. Therefore, the process is carried out under a temperature plate that is 35°C lower than the melting point of the film. If the temperature is below the shrinkage start temperature of the film, the curl of the film becomes large and it becomes difficult to grip both ends. Furthermore, if the temperature is 30° C. lower than the melting point of the film or higher, the films will fuse together, making it impossible to separate them into two sheets after heat treatment. Note that the heat treatment time is preferably 3 seconds or more; if the heat treatment time is 3 seconds or less, heat fixation tends to be insufficient. Further, although there is no particular upper limit, if the length is too long, a large device will be required, leading to increased costs. Therefore, about 3 to 30 seconds is preferable.

The second heat treatment is carried out at a temperature below the melting point of the film and 30°C lower than the melting point of the film while holding both ends of the film, preferably at a temperature 5°C lower than the melting point of the film.
It is carried out at a temperature lower than 25°C below the melting point of the film.

If the temperature is higher than the melting point of the film, the films will fuse together and cannot be separated into two pieces. In addition, when the temperature is 30°C lower than the melting point of the film,
The shrinkage rate of the product film in 95°C hot water is 10% or more, making it unusable for some applications. Note that the conditions regarding the heat treatment time are the same as in the case of the first stage heat treatment.

The crystalline thermoplastic resin refers to resins such as polyamide, polyester, ethylene-vinyl alcohol copolymer, and polystyrene. Among these, specific examples of polyamide resins include nylon-6 (shrinkage start temperature 45°C, melting point 215°C), nylon-6,6 (shrinkage start temperature 55°C, melting point 260°C), etc. .

Further, the heat treatment apparatus for carrying out the above heat treatment method is
means for folding a crystalline thermoplastic resin film biaxially stretched by the tubular method into a flat shape using, for example, a guide plate and a pinch roller; a first heating means for heat-treating the flat film; A trimming means for cutting both ends to separate the two films, a means for overlapping both films with air interposed between the two films using, for example, a roll, and a means for separating both ends of the overlapped films. It is characterized by having a gripping means, a second heating means for heat-treating the two films gripped at both ends, and a winding means for the heat-treated film.

The first and second heating means of the present heat treatment apparatus are preferably hot air ovens because they have high heating efficiency (and uniform heating is possible).

In addition, the rolls used in this heat treatment apparatus as a means for stacking both films while intervening air between the two films are grooved rolls (, In addition, plating treatment is applied to the surface.
i! It is preferable to avoid damaging the film with iL.

The reason why the two ends of the film are held is because if the ends are left free, the film will shrink during the heat treatment and there will be no point in heat fixing.

[Function] According to the present invention, the heat treatment step for heat setting is made into two steps, and the first heat treatment step, which is preheating, is provided before the step of separating the film into two sheets, thereby reducing the crystallization of the film. The degree of oxidation increases, and the sliding properties between the overlapping films improve. In addition, the second stage of heat treatment is performed with air interposed between the two separated films, so even if two layers are stacked, the films will not fuse together during heat setting. It disappears.

[Example 1] A heat treatment apparatus according to an embodiment of the present invention and a method for heat treatment of a crystalline thermoplastic resin film using the same will be described with reference to FIG.

First, a guide plate 2 and a pinch roll 3, which are means for folding the crystalline thermoplastic resin film 1 biaxially stretched by the tubular method into a flat shape, and a first heating means, which is a first heating means for heat-treating the flat film 1, are installed. 1 heating furnace 4, specifically a hot blast furnace, and a blade which is a trimming means for cutting both ends of the flat film 1 fed through the guide roll 7 and separating it into two films IA and IB. A trimming device 6 having a trimming device 5 is provided. Next, guide roll 7
A pair of rolls 8A located vertically apart serve as means for overlapping both films IA, IB, tl with air interposed between both films IA, IB sent through
, 8B and films IA, 1B, and three preferably IM-attached rolls 9A to 9C (see FIG. 2) located in order in the traveling direction of the films IA, 1B, and means for gripping both ends of the overlapping films IA, IB. The tenter 10 and the second film for heat-treating the two films IA and IB held at both ends.
A second heating furnace 11, specifically a hot blast furnace, is provided as a heating means. In addition, these grooved rolls 9A to 9C are
After groove processing, the surface is plated.

Finally, a winder 12 is provided as a winding means for winding up the heat-treated film IAIB via a guide roll 7.

Using this heat treatment apparatus, a crystalline thermoplastic resin film is heat treated as follows.

That is, after a crystalline thermoplastic resin film 1 which has been stretched by two wheels using the tubular method is folded flat by a guide plate 2 and pinch rolls 3, it is placed in a first heating furnace 4 as a first stage heat treatment.
In this step, the flat film 1 is preliminarily heat-treated at a temperature higher than the shrinkage start temperature of the film 1 and lower than the melting point of the film 1 by 30°C. Through this heat treatment, film 1
The degree of crystallinity increases, and the sliding properties between the overlapping films improve. Next, both ends of the flat film 1 are cut with the blade 5 of the trimming device W6 to separate it into two films IA and IB. Incidentally, the cutting of the flat film 1 may be performed by positioning the blade 5 slightly inward from both ends so that a portion of the selvedge is formed.
Alternatively, the blade 5 may be positioned at the fold of the flat film I so that no ears are formed.

Next, film IA is placed on the top and bottom of rolls 8A and 8B, respectively.
, IB are separated and conveyed, each film IA
, air is brought into contact with the inner surface of the IB. Next, 3 shown in Figure 2
By sequentially feeding the film through the grooved rolls 9A to 9c, the films IA and IB are kneaded together once while air is interposed between the films IA and IB. By using the rolls 9A to 9C in this way, this iM 1
Good contact between the films IA and IB and air can be obtained through the film 3. Next, the overlapping films IA and I
B is sent to the second heating furnace 11, and while holding both ends with the tenter 10, these two sheets are heated at a temperature below the melting point of the film 1 and 30°C lower than the melting point of the film 1 as a second heat treatment. The films IA and IB are heat-treated. Finally, the heat-treated films IA and IB are wound up by the winding machine 12 via the guide roll 7.

Next, Examples and Comparative Examples in which heat treatment was performed using the above-mentioned heat treatment apparatus and specifically changing the treatment conditions will be described.

Polyamide-based nylon-6 as crystalline thermoplastic resin
(relative viscosity 3.7) was extruded from a ring-shaped goo with a diameter of 60 cm, and then rapidly cooled in cooling water at 15°C.
A tubular nylon film (shrinkage start temperature: 45° C., melting point: 215° C.) with a thickness of 120 μm was produced. By heating this raw film 1 between a pair of nip rolls using an infrared heater, it is simultaneously biaxially stretched at a stretching ratio MD (movement direction of the film)/TD (orthogonal direction) = 3.0/3.2. did.

Next, this nylon film 1 was continuously supplied to a guide plate 2 and a pinch roll 3 and folded, thereby obtaining a flat tubular nylon film 1.

Next, this flat nylon film 1 was passed through a first hot air heating furnace 4 (clip method), where the nylon film 1 was subjected to a first heat treatment at 60°C for 15 seconds to preliminarily heat set it. .

Next, both ends of the flat nylon film are cut with a trimming device 6 to separate it into two nylon films IA and IB, and then these nylon films IA and IB are separated by rolls 8A and 8B to air the inner surface. and then passed between grooveless rolls 9A to 90 to overlap again.

Next, both ends are heated using a tenter 10 in a second hot air heating furnace 11.
These nylon films IA, IB while gripping with
A second heat treatment was performed at 210° C. for 110 seconds to perform heat fixation.

Next, these nylon films IA, which were heat-set,
The IB was wound up using a winding machine 12.

Nylon films IA and I obtained by the above heat treatment
B: Even when two layers are stacked, the films do not fuse together,
I was able to divide it into two pieces. Further, the shrinkage rate in hot water at 115°C was MD/TD=4°0/4.0 (%), and a nylon film with good dimensional stability that could be used in a retort was obtained.

-h 112-10 Heating temperature of the first heating furnace 4 and second heating furnace 11 and roll 9
Nylon films IA and IB according to each example were obtained under different conditions regarding the presence or absence of grooves 13 in A to 9C. The conditions such as the nylon film used were the same as in Example 1. In Examples 1 to 6, rolls 9A to 9 without grooves were used.
In Examples 7 to 10, rolls 9A to 9C with grooves 13 were used. In addition, these grooved rolls 9
In A to 9C, two crossed grooves were formed on the surface of a metal roll using a 10 cm pinch, and the surface was plated with chrome.

- Mosquito Removal - After producing a tubular nylon film using polyamide-based nylon-6 in the same manner as in the above example, this raw film was biaxially stretched.

Next, this nylon film is folded to obtain a flat tubular nylon film, and this flat nylon film is subjected to a first heat treatment at 150°C for 55 seconds in a hot air heating furnace, and then divided into two sheets without air intervention. Then, a second heat treatment was performed at 190° C. for 110 seconds in a hot air heating furnace to perform heat fixation.

Thereafter, in the next step, an attempt was made to separate the sheets into two and roll them up, but fusion had occurred and it was not possible to wind them up.

Nylon films according to comparative examples were obtained under different conditions regarding the heating temperature of the heating furnace and the presence or absence of air. The conditions of the nylon film used were the same as in Comparative Example 1. In addition, in Comparative Examples 3.4 and 6, the film was
After separating the nylon film into sheets, a grooved roll was used to introduce air into the nylon film.

In the case of Comparative Example 2, as in Comparative Example I, fusion occurred because no air was present between the films. In the case of Comparative Examples 3 and 4, the heat treatment temperature in the second stage was 220°C and the nylon
Since the temperature exceeded the melting point of No. 6 (215"C), fusion occurred although air was present. In the case of Comparative Example 5, the first stage heat treatment temperature was 190°C, which is 30°C lower than the melting point ( 1
Since the temperature was not below 85° C., fusion occurred at this stage. In the case of Comparative Example 6, the second stage heat treatment temperature was 18o
Since the temperature was not higher than 185°C, which is 30°C lower than the melting point, the shrinkage rate was large.

Table 1 summarizes the results of evaluating the processing conditions of Examples 1 to 10 and Comparative Examples 1 to 6 and the properties of the nylon films obtained in each of the Examples and Comparative Examples. Properties were evaluated in terms of curl degree, fusion degree, and shrinkage rate, and a pass/fail judgment was made as a comprehensive evaluation. In this table, the degree of curl ○ indicates no curl, △ indicates small curl, and × indicates large curl.
Up to △, it is a level where no mechanical trouble occurs. Fusion adhesion was measured under 24-hour monitoring, where ◎ indicates no occurrence, ○ indicates 1 to 2 occurrences, △ indicates 3 to 10 occurrences, × indicates fusion ignition, and XX indicates complete fusion. O1△ is a level where the fusion strength is low and mechanical 7^U is possible, and × is a level where I is not mechanically peelable. The shrinkage rate is obtained by measuring the yield rate in hot water at 95°C and 115°C. Also,
In the pass/fail judgment, ◎ is most suitable for industrial continuous production, O is no problem for industrial continuous production, △ is possible for industrial continuous production but with some trouble,
indicates that continuous industrial production is impossible and the product cannot be produced at all.

From the evaluation in this table, the nylon film obtained in the example has a higher curl degree, fusion degree, and yield II than the nylon film obtained in the comparative example. It can be seen that a nylon film with good i-rate and good dimensional stability (N) can be obtained.

[Effects of the Invention] According to the method and apparatus for heat treatment of crystalline thermoplastic resin films according to the present invention, heat treatment for heat setting can be performed on two stacked films without causing fusion. A film with high dimensional stability can be stably supplied.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a heat treatment apparatus according to an embodiment, and FIG. 2 is a perspective view of a chamfered roll. l...Crystalline thermoplastic resin film, 4...Heating furnace as first heating means, 6...Trimming device as trimming means, 8A, 8B...Roll, 98-9C
. . . roll, 11 . . . heating furnace as second heating means, 12 . . . winder as winding means. Applicant Idemitsu Petrochemical Co., Ltd.

Claims (4)

[Claims] (1) A step of folding a crystalline thermoplastic resin film biaxially stretched by the tubular method into a flat shape, and folding the flat film at a temperature above the shrinkage start temperature of the film and below 30°C lower than the melting point of the film. a step of heat-treating, a step of cutting both ends of the flat film to separate it into two films, and a step of separating the flat film into two films while holding both ends of the overlapping film with air interposed between the two films. A crystalline thermoplastic resin film comprising the steps of: heat-treating the film at a temperature lower than or equal to the melting point of the film and 30° C. lower than the melting point of the film; and winding the heat-treated film. Heat treatment method. (2) means for flatly folding a crystalline thermoplastic resin film biaxially stretched by the tubular method; a first heating means for heat-treating the flat film; and a method for cutting both ends of the flat film. trimming means for separating the films into two sheets; means for stacking both films with air interposed between them; means for gripping both ends of the overlapping films; and means for gripping both ends of the films. A heat treatment apparatus for crystalline thermoplastic resin films, comprising: a second heating means for heat treating two films; and a means for winding up the heat treated films. (3) A heat treatment apparatus for a crystalline thermoplastic resin film according to claim 2, wherein the first and second heating means are hot air ovens. (4) In the second claim, the crystalline thermoplastic resin film is characterized in that a grooved roll is used as a means for stacking the two separated films while interposing air between the two films. Heat treatment equipment.