JP2005254610A - Manufacturing method for image recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that unevenness of separation occurs in a laterally stepped pattern in an extrusion type molten-resin applicator. <P>SOLUTION: In a part where a molten-resin curtain formed by extruding a molten polyolefin resin by means of an extrusion die is sandwiched, with a web, in a gap pressed against the side of a cooling roll by the cooling roll and a press roll, a decompression chamber with a slit opened in parallel with the longitudinal direction of the cooling roll is arranged in such a manner that the slit gets close to a part of contact between the molten resin curtain and the web, and a flow rate of gas, which passes through the slit provided in the decompression chamber, is higher than a conveyance speed of the web. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention melts a polyolefin resin such as polyethylene or polypropylene and applies it to a web such as paper or film, and produces an extrusion paper that produces a smooth polyolefin resin coated paper without causing uneven horizontal stripping. The present invention relates to a method for producing an image recording material by applying a mold molten resin.

  Highly smooth polyolefin resin-coated paper obtained by applying a polyolefin resin to paper is used in many fields today. For example, polyolefin resin-coated paper is used as a base material in various fields such as photographic printing paper, printing paper, printing plate making material, inkjet recording paper, thermal recording paper, pressure-sensitive recording paper, and magnetic recording paper.

  By applying the polyolefin resin to the paper, it is possible to avoid unevenness due to unevenness in the mass of the paper and unevenness in smoothness due to the paper being made of pulp fibers. In addition, the improvement in water resistance by covering the front and back with a polyolefin resin is also the reason why polyolefin resin-coated paper has been used in many fields. That is, by applying polyolefin resin to paper, the advantages of high rigidity per unit mass, whiteness, and opacity, and the smoothness and water resistance of the film are coated with polyolefin resin. Given on paper.

  As a means for producing such polyolefin resin-coated paper, the polyolefin resin is melted and extruded from an extrusion die to form a molten resin curtain, and the curtain is sandwiched between a paper and a cooling roll (cooling roll) and applied. The method of doing is common. In the portion sandwiching the molten resin curtain and the web or the like, the adhesiveness is improved by increasing the pressure bonding between the web and the molten curtain using an elastic roll (press roll) coated with resin or rubber. The pressure-bonded resin and web are cooled by a cooling roll and peeled off from the cooling roll so as to be held by the peeling roll.

  A cooling medium is circulated inside the cooling roll, and is controlled so as to keep the cooling roll at an appropriate temperature according to the coating speed, molten resin temperature, coating amount, and the like. As the molten resin used, the polyolefin resin is often polyethylene or polypropylene. In addition, calcium carbonate or titanium dioxide is often used as a filler in order to increase the opacity and whiteness of the resin. Kneading these fillers usually involves pre-manufacturing a high-filling resin, usually called a masterbatch, and diluting it with an appropriate dilution resin before kneading. However, it is unavoidable to contain some moisture. A dispersant is used to knead these fillers. Furthermore, the temperature of the molten resin is usually heated to a temperature much higher than the melting point of the resin and extruded from the die. This is because the resin extruded from the die is not cooled and solidified when forming the molten resin curtain, and the adhesion to the web is increased. For this reason, an antioxidant for polyolefin resin is often added to the molten resin.

  From these facts, when the molten resin extruded from the die forms a curtain, a large amount of low molecular weight polyolefin resin and the above additives decompose and give off a lot of smoke. Most of the smoke is sucked and exhausted, but some smoke is carried along with the molten resin curtain onto the cooling roll. Since the smoke carried on the cooling roll is sandwiched between the cooling roll and the molten resin, it slightly accumulates on the surface of the cooling roll and becomes dirty. Further, it is known that when a low molecular component substance is present in the resin layer, a phenomenon called bleed out occurs in which the low molecular component moves to the air interface.

  It has been apparent from the examination so far that the horizontal stripping unevenness (hereinafter referred to as horizontal striping unevenness) occurs when the polyolefin resin-coated paper is peeled from the cooling roll. Moreover, it occurred when (1) the coating speed was increased, (2) the cooling roll was soiled, and (3) the cooling roll was not properly cooled. What is common to these is insufficient solidification of the molten resin due to insufficient cooling with the cooling roll of the molten resin.

  The cause of the horizontal stripping unevenness is that the film surface strength of the polyolefin resin solidified due to insufficient solidification of the molten resin falls, so that the uniform and smooth peeling does not occur when the resin-coated paper is peeled from the cooling roll. It is caused by causing. This occurs not only when the resin is not sufficiently solidified, but also when the cooling roll surface is contaminated and the portions are not uniformly cooled.

  Therefore, in order to solve these problems, it is necessary to clean the surface of the cooling roll frequently, and in order to keep the cooling roll temperature constant, the cooling medium management and the structure of the cooling roll are devised, resulting in horizontal peeling due to poor peeling. Unevenness was prevented. However, as long as the fate of the manufacturing industry is to increase the coating speed by solving the horizontal stripping unevenness, these methods cannot be used alone.

As means for solving such a problem, as a conventional technique, there is disclosed means for detecting a flutter that is an abnormal vibration that is the cause of peeling unevenness and adjusting the tension of the web (for example, see Patent Document 1). However, with this method, it is difficult to detect only fluttering that causes peeling unevenness in a laminator device that has a large number of mechanically movable parts, and there is a problem that the tension adjustment operation malfunctions when there is no peeling abnormality. What we have is the current situation.
JP 7-256723 A

  Even in the above-mentioned general apparatus and the coating method in which a polyolefin resin is applied to a web using a molten resin, it can be said that all problems occur by increasing the coating speed in order to increase productivity. However, an object of the present invention is to solve the horizontal uneven peeling that occurs particularly in the method of manufacturing an image recording material by applying an extrusion-type molten resin.

  The present invention is a method for producing an image recording material having a thermal lamination step, wherein a molten resin curtain formed by extruding a molten polyolefin resin with an extrusion die is pressed against the cooling roll side by a cooling roll and a press roll, A vacuum chamber having a slit opened in parallel with the longitudinal direction of the cooling roll at a portion sandwiched with the web in the gap is arranged so that the slit is close to a portion where the molten resin curtain and the cooling roll are in contact with each other. The object is achieved by the image recording material manufacturing method, wherein the flow rate of the gas passing through the slit provided in the decompression chamber is higher than the web conveyance speed. .

  According to the method for producing an image recording material of the present invention, it is possible to solve the horizontal uneven separation generated in the method for producing an image recording material by applying an extrusion type molten resin.

  In the present invention, in the thermal lamination step, smoke that is inevitably generated and is the main cause of the contamination of the cooling roll is a vacuum chamber (hereinafter, abbreviated as a suction device) having a slit opened in parallel with the longitudinal direction of the cooling roll. ) Is disposed so that the slit is brought close to the portion where the molten resin curtain and the cooling roll come into contact with each other. By using such a device, it is possible to prevent cooling roll contamination.

  The suction device in the present invention is preferably installed in an arrangement as shown in the sectional view of the thermal laminator device shown in FIG. That is, the base paper 3 before resin coating bites into the nip formed by the cooling roll 6 and the press roll 5. The polyolefin resin molten resin curtain 2 extruded from the extrusion type molten resin extrusion die 1 is dropped into the nip and applied to the web 3. At this time, in order to keep the nip formed by the press roll 5 and the cooling roll 6 uniform in the cross direction (cross-machine-direction), a pressurizing mechanism combining the two rolls of the backup roll 4 and the press roll 5 is used. Adopted. It should be noted that more rolls may be combined as necessary, and even a single press roll may not be a problem. The suction device 8 is arranged so that the slit-shaped opening is in contact with the portion where the molten resin curtain 2 and the cooling roll 6 are in contact. The image material support 12 that is held by the cooling roll 6 and coated with the molten resin is peeled off from the cooling roll 6 by the peeling roll 7.

  A detailed three-dimensional view of the suction device is shown in FIG. The decompression chamber 9 is decompressed by decompression means connected to the suction pipe. When the inside of the decompression chamber 9 is decompressed, a pressure gradient is generated at the slit opening, and air flows into the decompression chamber 9. By disposing the slit opening 10 in the vicinity of the portion where the molten resin curtain 2 and the cooling roll 6 are in contact with each other, dirt components adhering to the surface of the cooling roll can be introduced into the decompression chamber 9 in advance.

  Although the material which comprises a suction device is not specifically limited, It is important to have the intensity | strength which does not bring about a deformation | transformation by pressure reduction. In particular, since the opening area of the slit is easily affected by deformation due to reduced pressure, it is preferable to use a metal such as stainless steel, cast iron, or titanium having high rigidity in consideration of deformation.

  As a method of reducing the pressure in the vacuum chamber of the suction device, it is preferable to use a vacuum pump. Examples of the pump include a diaphragm pump, a turbo pump, a blade pump, a blower pump, and an oil rotary pump. A mist trap is preferably provided between the vacuum chamber and the pump for the purpose of removing the liquefied or solidified gas that has been sucked.

  As a condition for more effectively removing the smoke causing the contamination by the suction device, it is preferable that the flow rate of the gas passing through the slit provided in the decompression chamber is higher than the transport speed of the base paper. Since it is synchronized with the transport speed of the base paper, the peripheral speed of the cooling roll is equal to the transport speed of the base paper. The air near the surface of the cooling roll flows at the same speed as the cooling roll. As a result of the examination by the present inventors, in order to remove the smoke-like dirt component emitted from the molten resin curtain, as a dynamic pressure difference in the vicinity of the point where the molten resin curtain and the cooling roll are in dynamic contact, The present inventors have found that smoke-like soil components can be removed by suction with a pressure difference higher than the dynamic pressure difference corresponding to the peripheral speed of the cooling roll. The dynamic pressure difference can be represented by the average flow velocity inside the slit of the decompression chamber, and when the average flow velocity is higher than the peripheral speed of the cooling roll, the removal ratio of the smoke-like dirt component can prevent the cooling roll contamination It was found that it can be raised to a certain extent.

The average flow velocity at the slit opening is given by the product of the slit average opening width S [cm] and the effective opening length L [cm] in the longitudinal direction, and the exhaust flow rate at the suction pipe is Q [cm ³ / Second], the flow velocity V can be expressed as follows.
V [cm / sec] = Q [cm ³ / sec] ÷ (S [cm] × L [cm])
The exhaust flow rate is measured on the exhaust side of a decompression device such as a pump in consideration of volume change due to pressure, or when measured under reduced pressure, pressure correction must be performed.

  The method for producing an image recording material of the present invention is usefully applicable to image recording materials in various fields such as photographic paper, printing paper, printing plate making material, ink jet paper, thermal paper, pressure sensitive paper, magnetic recording paper and the like.

  In the following, the present invention will be described in detail by way of examples. Needless to say, the present invention is not limited to the examples. The addition amount% is mass%. The number of parts added is the number of parts by mass with respect to 100 parts in total.

After corona treatment of the base paper mainly composed of wood pulp, the thermoplastic resin composition 1 having the following composition is melt-coated on the back surface, and then the thermoplastic resin composition 2 is melt-coated on the opposite surface of the back surface. An image recording material was obtained. As the melt coating apparatus, the thermal lamination manufacturing apparatus shown in FIG. 1 was used. The conveyance speed of the base paper was 300 m / min, and the flow rate of the gas passing through the slit of the suction device was 315 m / min for all the apparatuses used for processing the front and back surfaces. The continuous processing time was 18 hours.
The thermoplastic resin composition 1: high density polyethylene (density 958kg / m ³⁾ 80 parts of low density polyethylene (density 922kg / m ³⁾ 20 parts of thermoplastic resin composition 2: low-density polyethylene (density 922kg / m ³⁾ 88 Part, rutile type titanium oxide 12 parts In addition, in preparing the thermoplastic resin composition 2, in order to advance the dispersion efficiently, after preparing a 60% concentration titanium oxide master batch in advance using low-density polyethylene as a dilution resin, It was mixed again with low density polyethylene.
The basis weight of the support base paper was absolutely dry, 150 g / m ² , and the polyethylene coating amount was 24 g / m ² on the back surface, 23 g / m ^{2 on} the lower layer, and 7 g / m ^{2 on the} upper layer.

After corona treatment of the base paper mainly composed of wood pulp, the thermoplastic resin composition 1 having the following composition is melt-coated on the back surface, and then the thermoplastic resin composition 2 is melt-coated on the opposite surface of the back surface. An image recording material was obtained. As the melt coating apparatus, the thermal lamination manufacturing apparatus shown in FIG. 1 was used. The conveyance speed of the base paper was 300 m / min, and the flow rate of the gas passing through the slit of the suction device was 280 m / min for all the apparatuses used for processing the front and back surfaces. The continuous processing time was 18 hours.
The thermoplastic resin composition 1: high density polyethylene (density 958kg / m ³⁾ 80 parts of low density polyethylene (density 922kg / m ³⁾ 20 parts of thermoplastic resin composition 2: low-density polyethylene (density 922kg / m ³⁾ 88 Part, rutile type titanium oxide 12 parts In addition, in preparing the thermoplastic resin composition 2, in order to advance the dispersion efficiently, after preparing a 60% concentration titanium oxide master batch in advance using low-density polyethylene as a dilution resin, It was mixed again with low density polyethylene.
The basis weight of the support base paper was absolutely dry, 150 g / m ² , and the polyethylene coating amount was 24 g / m ² on the back surface, 23 g / m ^{2 on} the lower layer, and 7 g / m ^{2 on the} upper layer.

(Comparative example)
After corona treatment of the base paper mainly composed of wood pulp, the thermoplastic resin composition 1 having the following composition is melt-coated on the back surface, and then the thermoplastic resin composition 2 is melt-coated on the opposite surface of the back surface. An image recording material was obtained. As the melt coating apparatus, an apparatus having a configuration excluding the suction apparatus 8 from the thermal lamination manufacturing apparatus shown in FIG. 1 was used. The conveyance speed of the base paper was 300 m / min. The continuous processing time was 18 hours.
The thermoplastic resin composition 1: high density polyethylene (density 958kg / m ³⁾ 80 parts of low density polyethylene (density 922kg / m ³⁾ 20 parts of thermoplastic resin composition 2: low-density polyethylene (density 922kg / m ³⁾ 88 Part, rutile type titanium oxide 12 parts In addition, in preparing the thermoplastic resin composition 2, in order to advance the dispersion efficiently, after preparing a 60% concentration titanium oxide master batch in advance using low-density polyethylene as a dilution resin, It was mixed again with low density polyethylene.
The basis weight of the support base paper was absolutely dry, 150 g / m ² , and the polyethylene coating amount was 24 g / m ² on the back surface, 23 g / m ^{2 on} the lower layer, and 7 g / m ^{2 on the} upper layer.

(Application result)
In Example 1, there was no occurrence of horizontal stripping unevenness due to the contamination of the cooling roll, and no fogging of the cooling roll was observed after 18 hours of continuous processing. In Example 2, a minute peeling sound was observed when the continuous processing time reached 15 hours, and after 18 hours of continuous processing, the surface of the cooling roll was observed. It was. In the comparative example, a peeling sound was generated when the continuous processing time reached 5 hours, and after 4 hours had elapsed, horizontal peeling unevenness was observed on the surface of the recording paper, and after 16 hours had elapsed, The base paper was wrapped around the cooling roll and was forced to stop.

Schematic of the extrusion type molten resin coating apparatus of the present invention. Three-dimensional view of the suction device of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extrusion type molten resin extrusion die 2 Molten resin curtain 3 Web 4 Backup roll 5 Press roll 6 Cooling roll 7 Peeling roll 8 Suction apparatus main body 9 Decompression chamber 10 Slit 11 Suction pipe 12 Image recording material

Claims (2)

  A method for producing an image recording material having a thermal lamination process, in which a molten resin curtain formed by extruding a molten polyolefin resin with an extrusion die is pressed against the cooling roll side by a cooling roll and a press roll, and the base paper is inserted into the gap A suction device having a decompression chamber having a slit opened in parallel with the longitudinal direction of the cooling roll at the portion sandwiched together is arranged so that the slit comes close to the portion where the molten resin curtain and the cooling roll come into contact. A method for producing an image recording material.   2. The method for producing an image recording material according to claim 1, wherein the flow velocity of the gas passing through the slit provided in the decompression chamber of the suction device is higher than the conveying speed of the base paper.

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