JPH04219227A - Composite sheet for releasable belt and releasable belt - Google Patents

Abstract

PURPOSE:To transmit the rotating power of a driving roll efficiently over a cooling roll by bonding a polytetrafluoroethylene film and a film consisting of plastics having a Young's modulus higher than polytetrafluoroethylene while leaving both end sections and forming adhesive layers on the inner side faces of both end sections of each film. CONSTITUTION:A polytetrafluoroethylene film 31 and a film 32 made up of plastics having a Young's modulus higher than polytetrafluoroethylene are bonded while leaving both end sections E, E, and adhesive layers 4 are formed on the inner side faces of both end sections E, E of each film, thus manufacturing a composite sheet for a releasable belt. The composite sheets for the releasable belts are shaped in an endless loop by the engagement bonding of both end sections E, E while the polytetrafluoroethylene films 31 are directed outward, thus manufacturing a desired releasable belt.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a composite sheet for a release belt and a release belt using the sheet.

(Prior Art) When transporting a plastic molded product while cooling it, cooling rolls are sometimes used. For example, in the production of plastic-coated paper used for paper packs, etc., a paper sheet is run on a cooling roll, and molten plastic is flowed down in a curtain shape onto the running paper sheet from an extruder directly above the roll, and then the cooling roll is The molten plastic coating film on the paper sheet is cooled and solidified.

In the above-mentioned cooling roll, it is necessary to provide a release layer in order to prevent molten plastic from adhering to the roll. For this reason, it is known to wrap a polytetrafluoroethylene adhesive film, but in this release layer,
When rewinding polytetrafluoroethylene adhesive tape, adhesive tends to remain on the roll, and the remaining adhesive must be removed with an organic solvent, which is troublesome. The only parts of the roll that come into contact with the molten plastic are the ends of the paper sheet, and wrapping a polytetrafluoroethylene adhesive film around the entire roll is difficult because polytetrafluoroethylene is quite expensive. There are absurdities such as being uneconomical.

As shown in FIG. 6, two release belts a and a made of polytetrafluoroethylene are installed between the cooling roll 2 and the drive roll 1, and only the ends of the paper sheet S are separated. If the paper sheet S is supported by each belt a, a, and the middle part of the paper sheet S is brought into direct contact with the cooling roll 2, there will be no problem of residual adhesive in the above (2), and the separation in the above (2) will be avoided. There is no problem of uneconomical use of the polytetrafluoroethylene adhesive sheet in the part of the roll that does not require mold treatment, and the above-mentioned unreasonableness (1) and (2) can be resolved.

(Problem to be solved) However, polytetrafluoroethylene has a small coefficient of friction, and in order to transmit the rotational power of the drive roll to the cooling roll, it is necessary to increase the belt tension considerably.
If such a large belt tension is borne by the narrow belt described above, the tensile stress acting on the belt will become extremely large, causing the belt to stretch in a relatively short period of time. belt tension cannot be maintained, and it becomes difficult to transmit the rotational force of the drive roll to the cooling roll.

Therefore, it is difficult to rotate the cooling roll smoothly, making it impossible to satisfactorily cool and mold the molten plastic film.

However, such disadvantages are limited by means of absorbing belt elongation,
For example, it is possible to eliminate this by using a dancer roll or the like, but this inevitably increases the cost of the device.

An object of the present invention is to provide a release belt that can efficiently transmit the rotational power of the drive roll to the cooling roll for a sufficiently long period of time with a simple mechanism even when installed between the drive roll and the cooling roll. It is in.

(Means for Solving the Problems) A composite sheet for a release belt according to the first invention has a polytetrafluoroethylene film and a plastic film having a higher Young's modulus than polytetrafluoroethylene that are bonded together with both ends left intact. , the structure is characterized in that an adhesive layer is provided on the inner surface of both ends of each film,
A release belt according to a second invention is characterized in that the composite sheet for a release belt according to the first invention is formed into an endless loop with the polytetrafluoroethylene film facing outward by interlocking adhesive at both ends. The configuration is as follows.

(Explanation of Examples) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective explanatory view showing an embodiment of a composite sheet for a release belt according to the first invention.

In FIG. 1, 31 is a polytetrafluoroethylene film, and 32 is a plastic film having a higher Young's modulus than polytetrafluoroethylene, and its Young's modulus is 50 kg/mm2 or more at 25°C. 4 is an adhesive layer provided on one side of each film, and the polytetrafluoroethylene film 31 and the plastic film 3
2, and by this adhesive layer 4, both ends E,
All parts except E are glued.

As the plastic film 32, polypropylene, polyethylene terephthalate, polyimide, polybutylene terephthalate polyether sulfone, polyether ether ketone, etc. can be used. As the adhesive, acrylic-based, rubber-based, silicone-based adhesives, nylon-based, EVA-based, ester-based hot melt adhesives, etc. can be used.

Although the thickness of the polytetrafluoroethylene film 31 is not particularly limited, it is practically preferable to set it to, for example, 0.025 mm to 0.3 mm in terms of cost, service life, and the like. The thickness of the plastic film 32 is set relative to the thickness of the polytetrafluoroethylene film 31 so as to suppress the elongation of the polytetrafluoroethylene film 31, for example, from 0.025 mm to
It is preferable to set it to 0.20 mm.

The thickness of the adhesive layer 4 is preferably 0.02 mm to 0.10 mm.

In order to manufacture the composite sheet for a release belt according to the first invention, as shown in FIG. Coated original film of plastic (Young's modulus is higher than polytetrafluoroethylene) 320
and in the adhesive layers 4 and 4, excluding both ends E and E,
After adhering by adhesive, heat fusion, etc., Fig. 2B
As shown in , a method can be used in which the composite sheet for release belt is cut into a large number of composite sheets A, . . . using a cutter.

FIG. 3 shows an embodiment of the release belt according to the second invention, in which both ends E and E of the composite sheet A for release belts according to the first invention are engaged and , the occlusal portion is adhered by adhesive, heat fusion, etc. to form an endless loop.

4A and 4B each show another embodiment of the first invention, in which 31 is a polytetrafluoroethylene film, 32 is a plastic film having a larger Young's modulus than the polytetrafluoroethylene film 31, and 4 is an adhesive layer, and the films 31 and 32 are bonded to each other by this adhesive layer 4 except for both ends E and E. In FIG. 4A, 51, 51 are double-sided separators temporarily attached between the adhesive layers 4, 4 at both end portions E, E. In FIG. 4B, 52, 52 are both ends E of each of the above-mentioned films 31, 32.
, E is a single-sided separator temporarily attached between the adhesive layers 4, 4.

For these separators 51, 51, 52..., paper, plastic film (polyethylene terephthalate, polyethylene, etc.) coated on one or both sides with a silicone mold release agent or a fluorine mold release agent can be used.

FIG. 5A shows the state in which the release belt according to the present invention is used, and FIG. 5B shows a cross-sectional view taken along line bb in FIG. 5A.

In FIG. 5A, 1 is a driving roll and 2 is a driven roll, which may be a cooling roll, for example. A1,
A1 is a mold release belt according to the present invention, and as shown in FIG. They are mounted with a predetermined tension at intervals of .

In FIG. 5A, if the tension side tension of belt A1 is F, the running speed of belt A1 is v, the friction coefficient between the belt and the roll is μ, and the winding angle of belt A1 is φ, then The power P transmitted to the roll 2 is as follows.

For the release belt A1, a composite of a polytetrafluoroethylene film 31 and a plastic film 32 having a larger Young's modulus than that of the film 32 is used, and the thickness of the polytetrafluoroethylene film 31 and The Young's modulus is t1 and E1, respectively, and the thickness and Young's modulus of the plastic film 32 are t2 and E2, respectively.
Then, the elongation rate Δe under the tensile force F is as follows, and since E2>E1, when the entire release belt is made of polytetrafluoroethylene (E1=E2)
Compared to the above, Δe can be made sufficiently small, and even if the tensile force F is increased, belt elongation can be suppressed and belt slip can be effectively prevented. Therefore, the belt tension F can be increased and the rotational power of the drive roll can be well transmitted to the driven roll.

As shown in FIG. 6, the release belt according to the present invention can be used to coat a running paper sheet S with molten plastic P, such as molten polyethylene, flowing down from an extruder C.

In this case, the molten plastic protrudes onto the release belt from both ends of the paper sheet, but since the outer surface of the belt is made of polytetrafluoroethylene film with excellent release properties, the plastic film is attached to the belt. It can run smoothly together with the paper sheet without causing any adhesion.

In the above, when the amount of wear of the release belt reaches a predetermined thickness (t), it is necessary to replace the belt.

Therefore, if the thickness of abrasion that the belt undergoes while traveling for a unit length is k, the running speed of the belt is v, and the length of the belt is l, then the thickness of abrasion that the belt undergoes during one revolution is k. Since the time required for this is l/v, the amount of belt wear per unit time is kv/l. Therefore, the usable time of the belt is tl/kv, and the longer the belt is, the longer the usable time becomes.

(Effects of the Invention) As described above, the release belt according to the present invention includes a composite sheet of a polytetrafluoroethylene film and a plastic film having a higher Young's modulus than polytetrafluoroethylene, with the polytetrafluoroethylene film on the outside. Since the plastic film with a high Young's modulus can bear most of the tensile force, it can suppress the elongation of the belt well even when the belt tension is increased, and therefore the belt width is narrow. Furthermore, even if the coefficient of friction between the belt and the roll is small, the belt tension can be increased to sufficiently increase the power transmitted from the driving roll to the driven roll as shown by the first equation. Therefore, even with the installation of the two belts described above, the driven roll can be rotated smoothly, and the unreasonableness when winding a polytetrafluoroethylene adhesive film around a roll can be avoided, that is, when rewinding a polytetrafluoroethylene adhesive film. residual adhesive,
It is possible to eliminate the unreasonable use of polytetrafluoroethylene adhesive film in parts of the cooling roll for manufacturing plastic coated paper that do not require mold release treatment, and furthermore, when changing the width of the paper sheet in the production of plastic coated paper, There is also an advantage that can be easily dealt with by simply shifting the belt in response to changes in sheet width.

Furthermore, in the composite sheet for a release belt according to the present invention, the above-mentioned release belt can be easily manufactured by simply engaging and gluing both ends of the composite sheet.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the first invention, FIGS. 2A and 2B are explanatory diagrams showing the manufacturing procedure of an embodiment of the first invention, and FIG. 2A is a preliminary stage. , FIG. 2B shows a later stage, FIG. 3 is an explanatory diagram showing an embodiment of the second invention, and FIGS. 4A and 4B are an explanatory diagram showing another embodiment of the first invention, respectively. 5A and 6 are explanatory diagrams showing the usage state of the release belt according to the second invention, respectively, and FIG. 5B is a sectional view taken along the line bb in FIG. 5A. 31... Polytetrafluoroethylene film, 32... High Young's modulus plastic film, 4... Adhesive layer, E, E
...Both ends, A1...Release belt. Agent Patent Attorney Mikatsu Matsuzuki

Claims (2)

[Claims] Claim 1: A polytetrafluoroethylene film and a plastic film having a higher Young's modulus than polytetrafluoroethylene are bonded to each other, leaving both ends intact, and an adhesive layer is provided on the inner surface of both ends of each film. A composite sheet for release belts characterized by: 2. The composite sheet for a mold release belt according to claim (1), wherein the polytetrafluoroethylene film is directed outward and formed into an endless loop by interlocking adhesive at both ends. belt.