JP6789655B2 - Sheet - Google Patents

Description

The present invention relates to a sheet containing polytetrafluoroethylene (PTFE).

Patent Document 1 relates to a fixing device, and uses a non-porous sheet having at least a sliding surface containing a heat-resistant resin as a sheet-like sliding member included in the fixing device, and the non-porous sheet. Is provided on a porous PTFE sheet having irregularities on the surface.

Further, Patent Document 2 discloses that a PTFE sheet having irregularities is used as a sliding sheet for a fuser.

The PTFE sheet is excellent in both slidability and releasability, but there is a demand in the market for a PTFE sheet with further enhanced releasability and slipperiness.

Japanese Patent No. 4543670 JP-A-2009-15227

An object to be solved by the present invention is to provide a sheet having excellent releasability.

According to the embodiment , a releasable sheet made of a fired body of a polytetrafluoroethylene-containing fluororesin is provided. This sheet has recesses or protrusions on at least one surface.

According to the embodiment, it is possible to provide a sheet having excellent releasability.

It is the image data by the non-contact type shape measuring machine of the 1st surface of the sheet which concerns on embodiment. It is sectional drawing of the sheet shown in FIG. 1 in two directions. It is the image data by the non-contact shape measuring machine of the 2nd surface of the sheet shown in FIG. It is a perspective view which shows the embossing process in manufacturing of the sheet which concerns on embodiment. The perspective view which shows the example which applied the sheet which concerns on embodiment to the release sheet of the bread dough transport tray. FIG. 5 is a perspective view showing an example in which the release sheet shown in FIG. 5 is applied to a bread manufacturing process. FIG. 5 is a side view showing an example in which the sheet according to the embodiment is used as a release sheet in a heat sealing device. The perspective view which shows the example which used the sheet which concerns on embodiment as a release sheet of a transport member.

Hereinafter, embodiments of the present invention will be described in detail.

According to the embodiment, a sheet having a concave portion or a convex portion on at least one surface and having a polytetrafluoroethylene-containing releasable property is provided. Such a sheet is excellent in releasability of a surface having a concave portion or a convex portion. Therefore, by arranging the sheet on a part or the like whose slipperiness or releasability with respect to the object is desired to face the object, the slipperiness and releasability with respect to the object such as the part is improved. .. Therefore, it is possible to smoothly transport the object.

The surface having the concave portion or the convex portion may be formed on only one surface of the sheet, but it can also be formed on both sides of the sheet. Further, both the concave portion and the convex portion may be present on one surface.

It is desirable that the pitch of the concave portion or the convex portion is 0.23 mm or more and 0.7 mm or less. By setting the pitch to 0.7 mm or less, the slipperiness and releasability of the polytetrafluoroethylene-containing sheet can be improved. The narrower the pitch, the better the slipperiness and releasability, but when the pitch is less than 0.23 mm, the traces of the concave or convex portion are likely to adhere to the object in contact with the surface having the concave or convex portion of the sheet. Become. In addition, the mechanical strength of the sheet may decrease. Therefore, by setting the pitch to 0.23 mm or more and 0.7 mm or less, the mechanical strength of the polytetrafluoroethylene-containing sheet is not impaired, and the material in contact with the sheet is not deformed. The sex can be improved. A more preferable range of the pitch is 0.32 mm or more and 0.52 mm or less. Here, the pitch of the concave portion or the convex portion means the distance between the adjacent concave portion or the convex portion.

The thickness of the sheet is preferably in the range of 0.025 mm or more and 0.15 mm or less. By setting the thickness to 0.025 mm or more, the mechanical strength required for the sheet can be maintained. Further, by setting the thickness to 0.15 mm or less, the flexibility required for the sheet can be maintained. Therefore, by setting the thickness to 0.025 mm or more and 0.15 mm or less, it is possible to impart the necessary mechanical strength and flexibility to the sheet.

The surface roughness of the sheet is preferably in the range of 15 μm or more and 130 μm or less. By setting the surface roughness to 15 μm or more, the slipperiness of the sheet can be improved. Further, by setting the surface roughness to 130 μm or less, it is possible to prevent the traces of the concave portion or the convex portion from adhering to the object in contact with the surface having the concave portion or the convex portion of the sheet. Therefore, by setting the surface roughness to 15 μmm or more and 130 μmm or less, it is possible to improve the slipperiness and releasability of the object in contact with the sheet without deforming the object.

The content of polytetrafluoroethylene in the sheet is preferably in the range of 50% by weight or more and 100% by weight or less. By setting the content to 50% by weight or more, the water repellency of the sheet can be enhanced and the slipperiness and releasability can be improved.

The sheet can contain components other than polytetrafluoroethylene (PTFE). Other components include, for example, modified polytetrafluoroethylene (modified PTFE), tetrafluoroethylene-propylene hexafluoride copolymer resin (FEP), ethylene tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin (PFA), and polyvinylidene fluoride. Includes vinylidene fluoride (PVDF) and ethylene tetrafluoroethylene copolymer resin (ETFE). These fluororesins are flame-retardant materials having excellent weather resistance and chemical resistance. The types of other components may be one or more.

An adhesive layer may be formed on at least a part of one side or both sides of the sheet. As a result, the sheet can be fixed to a target position, a member, or the like by the adhesive layer.

The method of manufacturing the sheet will be described. A fired product of PTFE is obtained by filling a mold with polytetrafluoroethylene particles (PTFE particles), performing pressure molding, and then firing. A film is obtained by cutting from the obtained fired body. The obtained film is embossed and then cut if necessary to obtain the sheet of the embodiment. It is also possible to perform annealing treatment before, after, or before and after embossing.

An example of embossing is shown in FIG. An unprocessed film between a metal roll (first roll) 11 having a plurality of protrusions on the surface and an elastic roll (second roll) 12 having a smooth surface without protrusions on the surface. When pressure is applied in the direction of the arrow 14 shown in FIG. 4 with the 13 in between, a concave portion corresponding to the convex portion of the first roll 11 is formed on one surface of the film 13, and the sheet of the embodiment having unevenness on one surface. 15 is obtained. The arrow 16 indicates the transport direction of the film 13.

For the PTFE particles, for example, PTFE molding powder can be used. Here, the molding powder means a raw material powder obtained by suspension polymerization. The molding powder is once crushed to a size of several tens to several hundreds of μm, and then subjected to treatments such as granulation {pelletizing}, finecutting, and presintering depending on the molding application. It was given. It is also called granular resin.

The calcination temperature is not particularly limited, but can be, for example, the melting point of the uncalcined polymer of PTFE of 340 ° C. or higher, preferably 360 ° C. or higher and 380 ° C. or lower. A cooling step may be performed after firing.

As an application example of the sheet of the embodiment, for example, foreign matter such as a heat-sealing sheet adheres to a mold release sheet for a transport member, a die, a press machine, etc. for imparting mold releasability to the surface of the transport member. A release sheet for preventing the above is mentioned, but the present invention is not limited to these applications.

An application example will be described with reference to FIGS. 5 to 8. 5 and 6 show an example in which the sheet of the embodiment is used as a release sheet on a transport tray as a transport member. The transport tray 17 shown in FIG. 5 is for transporting the bread dough 18 in the bread manufacturing process. The sheet 19 of the embodiment is arranged on the transport tray 17 as a release sheet. The bread dough 18 is not placed directly on the transport tray 17, but is arranged on the sheet 19. By doing so, the releasability of the bread dough 18 is improved, so that the bread dough 18 can be easily transferred from the transport tray 17 to the next step. For example, in the bread manufacturing process shown in FIG. 6, the bread dough 18 on the transport tray 17 is transported to the frying step. The transport tray 17 on which the bread dough 18 is placed is conveyed to 21 by the conveyor 20. Since the sheet 19 improves the releasability of the bread dough 18, the bread dough 18 is smoothly transferred onto the wire mesh belt 21. The bread dough 18 on the wire mesh belt 21 is conveyed to the fryer 22 and fried.

By using the sheet 19, even if the bread dough 18 is not sprinkled with hand flour, the bread dough 18 becomes slippery, so that the hand flour can be unnecessary or reduced. As a result, it becomes possible to improve the taste of bread. Further, the sheet 19 is unlikely to be cracked, chipped or frayed during use. Further, the sheet 19 is less likely to cause mold and is excellent in hygiene.

The sheet of the embodiment is excellent in the effect of improving the slipperiness or releasability of a sticky substance such as bread dough, but the thing to be transported by the transport tray is not limited to the sticky substance.

Although the sheet obtained by impregnating the glass fiber cloth with PTFE has mold releasability, the glass fiber cloth functions as an abrasive and is liable to crack, chip or fray. In addition, when a campus sheet is used as a bread dough transport member, hand flour is required and mold is likely to occur because it is made of cloth. On the other hand, the sheet containing polyamide and silicone resin can reduce the amount of hand flour used and is lightweight, but is prone to mold.

FIG. 7 shows an example in which the sheet of the embodiment is used as the release sheet of the heat seal bar of the heat seal device. The heat seal device 23 includes an upper heat seal bar 24a, a lower seal bar 24b, a release sheet fixing member 25, and a heater (not shown) installed on the upper heat seal bar 24a. The upper heat seal bar 24a and the lower seal bar 24b have recesses 26a and 26b near the center, respectively. The release sheet fixing member 25 is arranged in the recess 26a of the upper heat seal bar 24a. As the release sheet, the sheet 19 of the embodiment covers the heat seal surface of the upper heat seal bar 24a in a state of being hung on the release sheet fixing member 25. The sealing surface of the lower seal bar 24b is also covered with the sheet 19 of the embodiment. When the thermoplastic film 27 is placed between the heat seal surface of the upper heat seal bar 24a and the seal surface of the lower seal bar 24b and pressurized by the upper heat seal bar 24a and the lower seal bar 24b, the upper heat seal bar 24a Since the sheet 19 is interposed between the and the thermoplastic film 27 and between the lower seal bar 24b and the thermoplastic film 27, the thermoplastic film 27 does not adhere to the upper heat seal bar 24a and the lower seal bar 24b. , The thermoplastic film 27 can be heat-sealed.

FIG. 8 shows an example in which the sheet of the embodiment is arranged on the guide wall of the transport rail used for transporting bottles, corrugated cardboard, and the like. The transport rail 28 is used for transporting bottles, corrugated cardboard, and the like, and in FIG. 8, the bottle 29 is transported. The guide walls 30 are provided on both sides of the transport rail 28. The sheet 19 of the embodiment is arranged as a release sheet on the inner surface of the guide wall 30. One side of the sheet 19 is covered with an adhesive layer (not shown), and the sheet 19 is fixed to the inner surface of the guide wall 30 by the adhesive layer. As a result, the slipperiness and releasability of the guide wall 30 are improved, so that the bottle 29 can smoothly move on the transport rail 28 along the guide wall 30.

Hereinafter, examples will be described with reference to the drawings.
(Examples 1 to 6)
The mold was filled with PTFE molding powder of model M-391S manufactured by Daikin Industries, Ltd. having a bulk density of 0.78 g / mL. Next, the molding powder in the mold was pressed from above with a pressure of 17 MPa to obtain a premolded product.

The obtained premolded product was fired at 370 ° C. to obtain a PTFE fired product. By cutting the obtained PTFE fired body, a PTFE long film having a thickness of 100 μm and a short side of 300 mm was obtained.

By using the embossing apparatus shown in FIG. 4 and setting the height and pitch of the convex portion of the first roll to the values shown in Table 1 and forming a concave portion on one side of the obtained PTFE long film, unevenness is formed. Was formed. Subsequently, the PTFE film was annealed at 230 ° C. to obtain a long sheet containing PTFE of Examples 1 to 6. The pitch and surface roughness of the PTFE-containing sheets of Examples 1 to 6 were set to the values shown in Table 1 below by changing the pitch and height of the convex portion of the first roll of the embossing apparatus.

Image data of the embossed surface of the long sheet containing PTFE of Example 1 by a non-contact shape measuring machine (Keyence shape analysis laser microscope VK-X110) is shown in FIG. 1 and a cross section of the sheet shown in FIG. 1 in two directions. FIG. 2 shows image data of a surface located on the opposite side of the embossed surface by a non-contact shape measuring machine. The image data shown in FIGS. 1 and 3 represent only a part of the PTFE-containing long sheet. The line segment indicated by the number 3 in FIG. 1 is a line segment parallel to the longitudinal direction of the PTFE-containing long sheet. The line segment shown by No. 2 in FIG. 1 is a line segment parallel to the width direction (short side direction) of the PTFE-containing long sheet. As is clear from the comparison of the image data of FIGS. 1 and 3, the embossed surface shown in FIG. 1 has larger unevenness. Therefore, the embossed surface shown in FIG. 1 is referred to as the uneven surface 1, and the surface located on the opposite side of the embossed surface shown in FIG. 3 is referred to as the back surface 7. FIG. 2 shows a cross section of the PTFE-containing sheet cut along the line segment 2, a cross section of the PTFE-containing sheet cut along the line segment 3 perpendicular to the line segment 2, and a cross section of the PTFE-containing sheet cut along the line segment 8. Shown in. Cross sections 2, 3 and 8 shown in FIG. 2 show a state in which the uneven surface 1 is located on the upper side of FIG. The line segment 2 is a cross-sectional shape line parallel to the width direction of the PTFE-containing long sheet on the uneven surface 1 (the cross-sectional shape line of the portion of the concave portion 5b where the surface roughness Rz of JIS B 0601: 1994 is the highest). .. The line segment 3 is a cross-sectional shape line parallel to the longitudinal direction of the PTFE-containing long sheet on the uneven surface 1 (the cross-sectional shape line of the portion of the concave portion 5b where the surface roughness Rz of JIS B 0601: 1994 is the highest). .. The line segment 8 is a line segment that diagonally connects the locations on the back surface 7 where the surface roughness Rz of JIS B 0601: 1994 is the highest. The line segment 8 on the back surface 7 of FIG. 3 is shown by a solid line, and the portion corresponding to the line segment 8 on the uneven surface 1 of FIG. 1 is shown by a dotted line.

The concave portion is a portion recessed in a pyramid trapezoidal mortar shape from the uneven surface 1 to the back surface 7, and the deepest portion is indicated by 5b. The concave portions are surrounded by convex portions and are partitioned one by one by the convex portions. The convex portion is a portion indicated by a white grid-like frame in FIG. 1, and the highest portion is indicated by 5a.

The surface roughness of the uneven surface 1 and the back surface 7 of the PTFE-containing sheet and the pitch between the convex portions 5a were measured by the methods described below, and the results are shown in Table 1 below.

Regarding the surface roughness of the uneven surface 1, the maximum value of the surface roughness Rz of JIS B 0601: 1994 was obtained for each of the cross sections 2 and 3 in the two directions, and the two maximum values obtained were compared and the larger one was obtained. Let 4 be the surface roughness Rz of the uneven surface 1.

On the other hand, the pitch between the convex portions 5a of the concave-convex surface 1 is obtained by calculating the average interval Sm of the irregularities based on JIS B 0601: 1994 in the cross section in the direction in which the surface roughness Rz of the concave-convex surface 1 is determined. Let the value be the pitch 5 between the convex portions 5a.

In FIG. 2, the highest portion of the convex portion on the back surface 7 is indicated by 6, and the deepest portion of the concave portion is indicated by 9. On the back surface 7, the front surface Rz calculated based on JIS B 0601: 1994 is indicated by 10. At the position of the uneven surface 1 corresponding to the highest portion 6 of the convex portion of the back surface 7, there is the deepest portion 5b of the concave portion.

Table 1 below shows the thickness of the PTFE-containing sheet of Example 1, the pitch between the convex portions, the surface roughness Rz of the uneven surface and the back surface, the pitch of the convex portions of the first roll and the height of the convex portions. In Examples 2 to 6, the thickness of the PTFE-containing sheet, the pitch between the convex portions, the surface roughness Rz of the uneven surface and the back surface, the pitch of the convex portions of the first roll and the convex portions are the same as in Example 1. The heights are also shown in Table 1.
(Comparison example)
A PTFE-containing sheet was prepared in the same manner as in Example 1 except that it was not embossed. The obtained PTFE-containing sheet had smooth surfaces on both sides. The thickness of the PTFE-containing sheet of Comparative Example 1 is also shown in Table 1.

A 90 ° peel test was carried out on the PTFE-containing sheets of Examples 1 to 6 and Comparative Examples.
The polyethylene film was melted by heating, and a width of 80 mm was heat-sealed to the PTFE-containing sheet. After cooling the polyethylene (PE) film by air cooling, the polyethylene film is pulled at a speed of 50 mm / min so that the angle with respect to the PTFE-containing sheet is 90 °, and the force at the time when the polyethylene film is peeled from the PTFE-containing sheet. Is shown in Table 1 as PE peelability.

As is clear from Table 1, the PTFE-containing sheets of Examples 1 to 6 can easily peel off the heat-sealed polyethylene film, and are excellent in slipperiness and releasability.

In the above embodiment, the convex portion has a substantially square lattice shape, but the shape of the convex portion is not limited to this, and for example, a lattice shape other than a square such as a substantially rhombus can be used. Further, instead of providing the convex portion on the first roll for embossing, a concave portion may be provided. In that case, a pyramidal trapezoidal convex portion and a lattice-shaped concave portion partitioning the convex portion may be formed on the uneven surface. Further, in FIG. 4, the first roll 11 is arranged at the upper part and the second roll 12 is arranged at the lower part, but the positions of the first roll 11 and the second roll 12 are reversed, and the first roll 11 is placed at the lower part and the second roll is second. The roll 12 may be placed at the top.
Hereinafter, the inventions described in the claims of the original application of the present application will be added.
[1] A sheet having a concave portion or a convex portion on at least one surface and having polytetrafluoroethylene-containing releasability.
[2] The sheet according to [1], wherein the pitch of the concave portion or the convex portion is 0.23 mm or more and 0.7 mm or less.
[3] The sheet according to [1] or [2], which is a release sheet used for a member for transporting an adhesive substance.
[4] The sheet according to [3], wherein the sticky substance is bread dough.

1 ... Concavo-convex surface, 2 ... Cross-sectional shape line in the width direction of the concavo-convex surface 1, 3 ... Cross-sectional shape line in the longitudinal direction of the concavo-convex surface 1, 4 ... Surface roughness Rz of the uneven surface, 5 ... Pitch of the convex portion, 5a ... The highest part of the convex part on the uneven surface, 5b ... the deepest part of the concave part on the uneven surface, 6 ... the highest part of the convex part on the back surface, 7 ... the back surface, 8 ... the part with the highest surface roughness Rz on the back surface diagonally. Line segment connected to, 9 ... the deepest part of the recess on the back surface, 10 ... surface roughness on the back surface, 11 ... first roll, 12 ... second roll, 13 ... unembossed film, 15 ... sheet of the embodiment , 17 ... Transport tray, 18 ... Bread dough, 19 ... Sheet of embodiment, 20 ... Conveyor, 21 ... Wire mesh belt, 22 ... Fryer, 23 ... Heat seal device, 24a ... Upper heat seal bar, 24b ... Lower seal bar, 25 ... Release sheet fixing member, 26a, 26b ... Recess, 27 ... Thermoplastic film, 28 ... Conveyance rail, 29 ... Bottle, 30 ... Guide wall.

Claims (6)

A releasable sheet having recesses or protrusions on at least one surface and made of a fired body of a polytetrafluoroethylene-containing fluororesin . The sheet according to claim 1, wherein the pitch of the concave portion or the convex portion is 0.23 mm or more and 0.7 mm or less. The sheet according to claim 1 or 2, which is a release sheet used for a member for conveying an adhesive substance. The sheet according to claim 3, wherein the sticky substance is bread dough. The sheet according to any one of claims 1 to 4, wherein the content of the polytetrafluoroethylene in the sheet is in the range of 50% by weight or more and 100% by weight or less. The calcined product is composed of modified polytetrafluoroethylene, tetrafluoroethylene-propylene hexafluoride copolymer resin, ethylene tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin, polyvinylidene fluoride and ethylene tetrafluoroethylene copolymer resin. The sheet according to any one of claims 1 to 5, which comprises at least one selected from the group.