JPH0588655B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a take-off roll of a thermoplastic resin film molding apparatus for manufacturing a thermoplastic resin film, and a method for manufacturing a thermoplastic resin film. [Prior art] Thermoplastic resin film is a film (or sheet) with a thickness of about 0.05 mm to 0.2 mm made of vinyl chloride resin, polyurethane resin, EVA, ABS, etc.
It is used as stickers and marking films. Such a thermoplastic resin film is generally manufactured by the following process using a molding device equipped with a calendar roll molding machine or an extrusion molding machine. In other words, 1) For example, in the case of vinyl chloride resin, plasticizers, stabilizers, etc. are added to the resin.
Knead to obtain molten resin material A, 2) feed this to a calender roll molding machine a or an extrusion molding machine to mold it into film B, and 3) apply the above film B to each roll of take-off roll r following the molding machine. 4) Emboss the surface of film B with embossing roll b, 5)
Cooling with cooling roll c (including heat treatment)
and 6) trimming as necessary and winding it up to make a product (refer to Figure 1a for the reference numeral). In addition,
In the production of transparent films, the embossing step (4) is omitted. Among the above, take-off rolls are molded with a molding machine and have rubber-like elasticity within a temperature range (approximately
This is a roll for taking thermoplastic resin film at a temperature of 150℃ to 200℃ and sending it to an embossing roll or a cooling roll. Normally, take-off rolls consist of two to seven rolls that are kept close to the above-mentioned temperature by circulating high-temperature water inside, and each roll is placed in parallel to create a slight tension on the thermoplastic resin film. It is rotationally driven. The functions required of the take-off roll are to accurately hold the thermoplastic resin film at a predetermined temperature and feed it to the embossing roll without changing the film's thickness or cross-sectional shape as much as possible. In order for the take-off roll to perform these functions, the surface properties of the roll have an important meaning, and conventionally, the surface of each roll of the take-off roll is
They were either side-blasted (or shot-blasted) to give them a matte finish, or (b) polished to give them a smooth mirror surface, and both were coated with chrome plating to prevent corrosion. The surface roughness of the roll made in this way is approximately 5 to 10 μm (R _nax ) in the case of (a) above, and 1 μm in the case of (b).
(R _nax ) or less. [Problems to be Solved by the Invention] In take-off rolls having a roll surface as described in (a) or (b) above, an inconvenient phenomenon called "net-in" of the thermoplastic resin film occurs to a considerable extent. Netzukin is a thermoplastic resin film wrapped around take-off rolls that is stretched in the longitudinal direction by the tension exerted by each roll, reducing its width and causing its side edges (ends in the width direction) to expand. This is a phenomenon in which the thickness increases. The "net-in rate" that indicates the degree of reduction is the reduction rate of the film width expressed in %. When the net-in rate is high, the side edges of the thermoplastic resin film must be trimmed over a wide area, resulting in an extremely low film production efficiency. The trimmed side edges of the film are kneaded as reusable material and then fed to the molding machine, but if there is a large amount of reused material, it is difficult to melt it uniformly, which can result in fish-eye defects and the like on the film. Traditional take-off roll has net-in rate of 3
Although it can reach up to ~10%, the reason why Netzukin occurs so easily is as follows. In the take-off roll of (a) above, in which the surface of each roll is side-blasted, the adhesion of the thermoplastic resin film to the roll surface (matte surface) is small, so the film slips in the width direction on the roll, causing neck-in. On the other hand, in the take-off roll (b) above, in which the surface of each roll is mirror-finished, the thermoplastic resin film strongly adheres to the mirror surface, so it does not slip on the roll, but when the film is peeled off from the roll surface, tension is applied to the film. acts, and this causes netquin. In case b), the net-in rate is lower than in case b), but gas tends to be interposed between the roll surface and the film in a patchy manner, which causes discontinuous patches on the film surface. Sometimes. In addition, the above-mentioned netquin is a distortion that occurs while the thermoplastic resin film has rubber-like elasticity, so the molecular arrangement of the film loses its isotropy at the time the netquin occurs, and the film after cooling is distorted in the longitudinal direction. It has the inherent possibility of shrinkage. Therefore, if a thermoplastic resin film is produced using the above-mentioned take-off roll, even if the side edges where the thickness has increased due to necking are trimmed and a film with a uniform appearance and thickness is obtained, After the film is wound or used as a sticker or other product, it may shrink and deform significantly in one direction. [Object of the Invention] The present invention has been made to solve the above-mentioned problems, and has a feature that there is less slippage of the thermoplastic resin film on the roll surface, that the film is easily peeled off from the roll surface, and that the roll and film can be separated easily. To provide a take-off roll for a thermoplastic resin film molding device, which has an escape area for gases caught up between the rolls on the roll surface, and therefore hardly causes neck-in or spots on the thermoplastic resin film. It is. Another object of the present invention is to provide a method for producing a thermoplastic resin film that maintains isotropic molecular arrangement and exhibits almost no shrinkage using the take-off roll. [Means for Solving the Problems] In order to achieve the above object, the take-off roll of the thermoplastic resin film molding apparatus of the present invention has the following features:
At least the surface of the first roll following the molding machine is formed into a rough surface having countless minute substantially hemispherical protrusions. In addition, the surface roughness of the roll can be adjusted to a maximum height of 20 μm or more.
100μm and the surface roughness of each roll.
It is preferable that the roughness is made finer (lower roughness) in order from the first roll to the rear roll. Furthermore, the method for producing a thermoplastic resin film of the present invention includes forming a thermoplastic resin material blended with a plasticizer, a lubricant, or a stabilizer and melting it into a film using a calendar roll molding machine or an extrusion molding machine. The film is taken up by a take-off roll, at least the first roll of which has a rough surface having numerous minute substantially hemispherical protrusions, and then cooled. [Function] According to the take-off roll of the thermoplastic resin film molding apparatus of the present invention, the thermoplastic resin film moderately adheres to countless microscopic substantially hemispherical protrusions on the surface of at least the first roll following the molding machine. Since there is almost no slippage and the film is easily peeled off from the roll surface, the occurrence of net-in can be minimized. In addition, the gas caught between the roll surface and the film escapes into the recesses between the numerous substantially hemispherical protrusions, and no patchy intervening portions of gas are formed between the roll and the film, so that no spots are formed on the film. Note that the thermoplastic resin film has the highest temperature in the first roll following the molding machine among the take-off rolls, and is sensitive to intervening nets and gases.
The above effect is most effective in the first roll. Furthermore, the above effect is remarkable when the rough surface has a maximum height of 20 μm to 100 μm. As for the surface roughness of each roll of the take-off roll, if the surface roughness is made finer in order from the first roll to the rear roll, there will be no problem when mirror-embossed finish is applied to the film surface using the embossing roll. In addition, in the method for producing a thermoplastic resin film of the present invention, the film is produced by using the above-mentioned take-off roll while maintaining the same molecular arrangement within the film. During this time, the film rarely shrinks or deforms in one direction. [Example] FIG. 1 is a side view showing an outline of a thermoplastic resin film molding apparatus according to an example of the present invention. As shown in the figure, this molding apparatus is equipped with a calender roll molding machine a, which is followed by a take-off roll r, an embossing roll b, a cooling roll c, a winder d, etc., arranged in this order. In the calender roll forming machine a, four rolls a1, a2, a3, and a4 are arranged close to each other in an inverted L shape, and each roll is driven to rotate, and the temperature is adjusted by circulating high-temperature water etc. inside. has been done.
When molten thermoplastic resin material A, which is a mixture of thermoplastic resin and a plasticizer, etc., mixed and kneaded in advance, is supplied between rolls a1 and a2 at the top of molding machine a, resin material A is mixed between three pairs of rolls. It is rolled while forming some banks (pools) and is molded into a thermoplastic resin film B having a predetermined thickness. The take-off roll r consists of four rolls 1, 2, 3, and 4 arranged slightly apart from each other, and takes the film B formed by the forming machine a, and separates each roll 1 as shown in Fig. 1. ~ 4 are wound alternately above and below and sent to the next process. Each roll 1 to 4 is heated to 130℃ or more by circulating high-temperature water, etc.
The temperature is maintained at 180°C, and the speed is adjusted to create a slight tension on the film B, which is rotated. Embossing roll b applies a gloss (mirror finish) to the surface of film B sent from takeoff roll r.
An embossed finish such as matte finish (matte finish) is applied (this is omitted when manufacturing transparent film), and a steel roll b1 and a rubber roll b2, which can be replaced depending on the finish, are arranged so as to be in pressure contact with each other. In addition, in embossing roll b, film B
is cooled to below 100℃. A cooling roll c consisting of a plurality of rolls c1, c2, . . . is provided behind the embossing roll b, and the film B is cooled to room temperature here. The winder d winds up the film B with a winding roll d3, and is provided with a tension adjustment roll d1 and a winding roll d2 in order to smoothly wind the film. In the above thermoplastic resin film molding apparatus, the four rolls 1 to 4 of the take-off roll r are formed as follows. In other words, the cylindrical part (roll body) is made of carbon steel pipe and the outer diameter is
It was machined to a length of 125 to 250 mm (for example, 150 mm), and its surface was formed into a rough surface with countless minute approximately hemispherical protrusions X by electrical discharge machining, as shown in Figure 3. Chrome plating has been applied. The surface roughness of such a rough surface is as follows: Roll 1 has a maximum height of 50 μm (R _nax ) and Roll 2 has a maximum height of 40 μm.
(R _nax ), 30 μm (R _nax ) for roll 3, and 20 μm (R _nax ) for roll 4, so that the roughness becomes finer (lower roughness) in order from roll 1 to the following rolls. Note that FIG. 3 is a cross-sectional view of a part of the surface of the roll 1 enlarged with a microscope (magnification: 600 times). Also, plating does not necessarily have to be applied. Electric discharge machining of the rolls 1 to 4 is performed by arranging a roll (workpiece) and an electrode facing each other with a minute interval in a machining fluid, and applying a pulsed voltage to both. Rotate the roll and feed the electrode horizontally (move in the axial direction of the roll) while maintaining a minute interval.
Then, an electric discharge machined surface (rough surface) is formed on the roll surface. The roughness of the machined surface is determined by the single discharge energy, that is, the discharge current value and the time width of the pulse, so the roll surface can be roughened to an arbitrary roughness depending on the type of thermoplastic resin film (for example, It is also possible to change the size of the substantially hemispherical protrusions X and the spacing between those protrusions. Regarding surface roughness, including the display above,
In this specification, any Japanese Industrial Standard JIS (B0601)
It is expressed by the maximum height (R _nax ) according to That is, the average value of the height R _nax from the highest peak to the lowest valley bottom of the cross-sectional curve (roughness curve) in the section of reference length L is referred to as surface roughness. Therefore, for example, the maximum height of 50 μm (R _nax ) means that the above R _nax is approximately 50 μm (see Figure 4), and since it is the "maximum height", it is 0 μm.
This does not mean that any roughness between (R _nax ) and 49 μm (R _nax ) is acceptable. In this example, a vinyl chloride resin film B shown below was manufactured using a thermoplastic resin film molding apparatus having a take-off roll r configured as described above. Composition PVC (=1300): 100 parts Plasticizer (DOP): 30 parts Other compounding agents: Appropriate amount (as necessary) Film dimensions Width 1200 mm, thickness 0.07 mm Film surface Mirror embossed (polished) finish As a result, take-off Roll r (Roll 1-4)
The net-in rate of thermoplastic resin film B was 0.7% on average, which was a fraction of the value for conventional take-off rolls. Furthermore, there were no speckled defects in the film B due to the presence of patchy gas between the roll and the film, and the glossy finish on the surface of the film B by the mirror-finished embossing roll b was also good. A heat load test and an outdoor aging test were further conducted on the vinyl chloride resin film B that was finally wound up on the take-up roll d3 of the winder d, but the net-in rate was extremely low. Therefore, the incidence of shrinkage and deformation of film B was almost zero. In other words, the vinyl chloride resin film B produced as described above is
It will not shrink or deform even if it is used as a final product such as a sticker for a long period of time in an environment with severe temperature conditions. In another example, satin embossed roll b
When finishing the surface of PVC resin film B with a matte finish, the surface was also polished to 50 μm by electrical discharge machining.
Four rolls 1 to 4 with a rough surface of (R _nax )
was used as the takeoff roll r. In this case, the net-in rate is even lower than above, and the average
It became 0.5%. In other words, the net-in rate is even better when the surface roughness of each of the rolls 1 to 4 is 50 μm (R _nax ). However, in this case, it is not suitable for mirror embossing (polishing) finishing, and even if mirror embossing roll b is used, the rough surface created by rolls 1 to 4 remains on the surface of film B. Furthermore, in another example, rolls 1 to 4 have a rough surface with a roughness of 50 μm (R _nax ) by performing metal spray processing on the surface.
was used as Takeoff Roll R to produce vinyl chloride resin film B. rolls 1-4
For thermal spraying, use chromium particles (powder) with a particle size of 0.5 mm or less.
The coating was carried out using a gas powder spraying method using the thermal spraying material, and plating after thermal spraying was omitted. In this case as well, the net-in rate in the take-off roll r was 1% or less, and there were no spot defects in the film B, giving good results. Note that ceramic spraying may be performed instead of metal spraying. In this way, countless minute approximately hemispherical protrusions X
Rolls 1 to 4 formed with a rough surface having a rough surface function very effectively as the take-off roll r as described above, but the reason why such a take-off roll r was used in the above examples is as follows. This is based on preliminary experiments. The experiment and results will be described below. The experiment was conducted by making a prototype of vinyl chloride resin film B' using the test molding apparatus shown in FIG. This equipment is equipped with a calender roll forming machine a' of the same type as described above (Fig. 1), a single-roll type take-off roll r', an embossing roll b', and a cooling roll c', arranged in this order. As r′, one roll 1′ is
It is designed to be removable and replaceable. Various rolls with different surface properties were used as roll 1' (including rollless rolls), and manufacturing conditions (molding machine
Vinyl chloride resin films B' of the same size were manufactured at the same rotational speed, temperature, etc. from a' to cooling roll c', and the net-in rate in each case was investigated. As a result, as shown in the table below (next page), the net-in rate is low when roll 1', whose surface has been roughened by electrical discharge machining or metal spraying, is used as take-off roll r'. I understand. When the surface of roll 1' was mirror-finished (case d) and when it was coated with Teflon (case e), spot defects due to the presence of gas occurred in film B', so cases g to j

【table】

[Table] and Cases m to p, that is, the surface of roll 1' is formed into a rough surface with a surface roughness of 20 μm (R _nax ) to 100 μm (R _nax ) by electric discharge machining or metal spray machining. It can be said that it is superior in comparison.
Note that in an actual molding device, a plurality of rolls are provided as a take-off roll, so the absolute value of the net-in rate will be a value that is somewhat different from the results of this experiment. Among the above, the net-in rate was the lowest and no spot defects due to gas intervention occurred when the surface of roll 1' was roughened to a roughness of 50 μm (R _nax ) by electrical discharge machining (case i). ), but FIG. 4 shows an example in which the roughness curve of the surface of the roll 1' in this case was determined using a stylus type surface roughness measuring device. The roughness curve in the figure is related to the scale of the vertical and horizontal axes,
Although the apparent height of the unevenness does not match that in Fig. 3, it can be seen in Fig. 4 that the area near the peak of the protrusion has a relatively smooth arc shape. Therefore, considering these points, the reason why the rough surface produced by electrical discharge machining reduces the neck-in of thermoplastic resin film is that a) approximately hemispherical protrusion X (Fig. 3)
The smooth tip of the convex portion corresponding to (near the peak in Figure 4) acts like a minute mirror surface,
The film adheres easily and does not slip easily,
b) Gas (air) passes through the recess (near the bottom of the valley in Figure 4) corresponding to the valley between the roughly hemispherical protrusions X (Figure 3).
It is presumed that because the film easily moves in and out, no tension is applied when the film is peeled off from the roll surface. Furthermore, it is thought that because gas easily enters and exits as described above and is not interposed between the film and roll in a patchy manner, no patchy defects occur in the film. In addition, in the above examples (and experiments), a take-off roll that follows a calender roll forming machine was introduced, but the take-off roll of the present invention has exactly the same effect and effect even when it follows an extrusion machine for film forming. be effective. Furthermore, by using the thermoplastic resin film molding apparatus equipped with the take-off roll of the present invention, in addition to the above-mentioned vinyl chloride resin, films (sheets) made of thermoplastic resins such as polyurethane, polyethylene, EVA, and ABS can be formed. ) can be similarly produced under favorable conditions, and the produced films hardly shrink or deform. [Effects of the Invention] According to the take-off roll of the thermoplastic resin film molding apparatus of the present invention, the degree of neck-in that occurs in the thermoplastic resin film produced by this is very slight, and there is no unevenness due to the presence of gas. No defects occur. Therefore, it is possible to efficiently produce a thermoplastic resin film with high thickness accuracy while minimizing loss due to trimming. In particular, the take-off roll of claim 3 is suitable for applying a mirror emboss finish to a film. Note that the rough surface having countless minute substantially hemispherical protrusions constituting the roll surface can be easily formed to a desired roughness by electric discharge machining or metal spray machining. Further, according to the method for producing a thermoplastic resin film of the present invention, the film produced thereby is as follows:
Not only is the thickness accuracy high due to the low net-in rate, but also because the molecular arrangement is isotropic.
Even after it is used as a final product such as a stick car, it hardly shrinks or deforms.

[Brief explanation of the drawing]

Fig. 1 is a side view showing an overview of a thermoplastic resin film molding apparatus according to an embodiment of the present invention, Fig. 2 is a side view showing an overview of a test forming apparatus, and Fig. 3 is a partially enlarged sectional view of the roll surface. , FIG. 4 is a drawing showing an example of the roughness curve of the roll surface. 1, 2, 3, 4, 1'...roll, r, r'...
Takeoff roll, X...approximately hemispherical protrusion, a,
a'... Calendar roll forming machine, b, b'... Embossing roll, B, B'... Thermoplastic resin film.

Claims (1)

[Scope of Claims] 1. A take-off roll provided in a thermoplastic resin film molding apparatus subsequent to a calender roll molding machine or an extrusion molding machine, the surface of at least the first roll following the molding machine being , a take-off roll of a thermoplastic resin film molding device formed on a rough surface having countless minute, approximately hemispherical protrusions. 2 Adjust the surface roughness of the rough surface to a maximum height of 20 μm or more.
The take-off roll of the thermoplastic resin film molding apparatus according to claim 1, having a thickness of 100 μm. 3. The take-off roll for a thermoplastic resin film molding apparatus according to claim 1 or 2, wherein the take-off roll is composed of a plurality of rolls, and the surface roughness is made finer in order from the first roll to the rear roll. 4. Molten thermoplastic resin material mixed with plasticizer, lubricant, stabilizer, etc. is molded into a film using a calendar roll molding machine or an extrusion molding machine, and this film is molded onto the surface of at least the first roll. 1. A method for producing a thermoplastic resin film, characterized in that the film is taken up by a take-off roll formed on a rough surface having countless minute substantially hemispherical protrusions, and then cooled.