KR102456149B1 - Process for making a renewable release paper - Google Patents

Abstract

The present invention relates to a method for manufacturing an eco-friendly release paper in which a silicone release agent layer is applied directly on a paper substrate without an intervening layer.
The present invention, the step of supplying a paper substrate; A calendering step of supplying moisture to the paper substrate so that the water content is in the range of 4 to 7%, heating to a temperature of 70 to 140° C., and passing a multi-stage pressing roller to which a pressure of 25 to 50 kg/cm 2 is applied; Corona treatment with a high frequency of 25Kv of 20 ~ 50KHz oscillation frequency in a corona treatment machine with 30 ~ 75dine; A silicone-based release agent layer is applied to the surface of the paper substrate using a reverse five-roll coater, wherein the passing speed of the paper substrate is 300 to 1800 m/min, and the application amount of the release agent layer is 0.4 to 3.0 g/m. step; A forming step of passing a drying furnace having a 15 m section at the entrance of 180 to 200 ℃ at a speed of 300 to 1800 m/min; and re-humidifying so that the moisture content is in the range of 4.0 to 6.5%.
According to the present invention, as a thin silicone release agent layer is directly coated on the surface of a paper substrate without a primer coating layer acting as an obstacle to release paper recycling, the used release paper is easily dissociated from the pulp and separated from a very small amount of silicone pressure-sensitive adhesive component. It is eco-friendly because the release paper can be recycled.

Description

Method for manufacturing renewable release paper {PROCESS FOR MAKING A RENEWABLE RELEASE PAPER}

The present invention relates to a method for manufacturing a release paper for a paper substrate, and more particularly, to a method for manufacturing an eco-friendly release paper that enables recycling of the used release paper by directly applying a silicone release agent layer without an intermediate layer on the paper substrate. will be.

Release paper (also called 'release paper') is attached to an object and serves to protect the attachment surface of the object and maintain the properties of the surface. It is attached to the surface of the object through the layer, and then peels off when the object is used and is separated.

Such release papers are used in various ways throughout the industry, and to list typical uses, there may be mentioned packaging tapes, sticker labels, synthetic leather, various electronic components, and the like. On the other hand, in the cross-sectional structure of the release paper, a primer coating layer (or 'intermediate layer' or 'prevention layer' has the same meaning) is usually interposed on one or both sides of a synthetic resin film or paper substrate, and a silicone-based release agent layer is usually applied thereon. .

A representative material constituting the primer coating layer applied on the base paper of the paper substrate may include a polyethylene (PE) resin, which prevents moisture penetration of the paper substrate to prevent deformation of the substrate due to moisture penetration, By filling in the rough upper surface of the paper substrate, the surface is flattened, the gloss is improved, and the shape of the tensile strength is achieved. It is known to play a role such as

As a prior art for controlling peeling force or improving adhesion by improving the adhesion properties of the silicone layer of the release paper, Patent Registration No. 10-1708509 discloses a silicone composition comprising siloxane in which a substituent containing an alkenyl group is bonded to a silicon atom as an adhesive improving component. A release paper comprising a layer is disclosed.

In addition, in Patent Publication No. 10-2018-0062352, a release agent layer is formed with a mixture of an amino alkyd resin and an epoxy resin that does not contain a silicone compound on the coating layer formed on one side of the paper substrate, thereby improving properties compared to the conventional silicone release agent layer. Attempts to obtain a surface state exhibiting

In addition, Korean Patent Laid-Open No. 10-2011-0016443 discloses an invention in which the hydroxylation catalyst in the silicone composition constituting the release agent layer is treated with a contact poison to control the peel force.

On the other hand, as a technology that attempts to change or improve the primer coating layer rather than the release agent layer of the release paper, Patent Registration No. 10-1879816 includes an adhesive vinyl resin in PVA instead of PE, which has been used before as a primer coating layer composition. A release paper is disclosed that uses PVA resin to prevent moisture permeation and to exhibit anti-curling properties.

In addition, in Patent Registration No. 10-0315994, when a water-soluble polymer material such as corn starch or dextrin is used as the primer coating layer composition and the separated release paper is put into water after use, the water solubility between the paper substrate and the release agent layer is An invention is disclosed in which the polymer material layer is dissolved in water to separate the silicone release agent layer and the paper substrate (pulp, cellulose) to utilize the paper substrate as recycled pulp.

As described above, most of the existing release papers have a primer coating layer made of a resin composition such as PE, PVA, PP as an intermediate layer between the paper substrate and the release agent layer, and a silicone-based or other release agent layer is formed thereon. .

However, in the conventional release paper including the primer coating layer, a separate manufacturing process for coating a paper substrate by melting a solid raw material such as PE or PP at high heat in a short time and accompanying equipment and energy are required, The primer coating layer is vulnerable to high temperatures during the formation of dots and adhesive layers, which may cause peeling problems.

And a more serious problem is that, due to the presence of a primer coating layer made of a synthetic resin material, it is practically impossible to separate the paper substrate (pulp) even if it is dissolved in water for regeneration or recycling, so almost all of the release paper is discarded and incinerated. , the combustion of the resin contained on the surface of the release paper during incineration has a detrimental effect on the atmospheric environment, and is undesirable from an environmental point of view because it is disadvantageous in terms of resource recycling.

The present invention does not form a primer coating layer between the paper substrate and the release agent layer, which is a major factor in the disadvantages and problems pointed out in the conventional release paper or release paper manufacturing method, but the application of the existing release agent layer is made directly on the paper substrate. It is an object of the present invention to provide a method for producing a release paper with

Another object of the present invention is to perform a pretreatment and an improved release agent layer curing process on the paper substrate before and after forming the release agent layer on the paper substrate without forming the primer coating layer, so that the level equivalent to that of the release paper with the existing primer coating layer interposed therebetween An object of the present invention is to provide a method for manufacturing an eco-friendly release paper that can be recycled while exhibiting the quality characteristics of

The above object of the present invention is to apply a release agent layer after calendering and corona treatment on at least one surface of a paper substrate supplied from a supply roll, and to form a release agent layer by passing a dryer maintained at a high temperature at high speed. It is achieved by a release paper manufacturing method consisting of a series of successive steps of post-winding.

Hereinafter, each step of the manufacturing method will be described in detail.

[paper description]

The paper substrate used in the present invention includes all kraft papers including general kraft paper, stretched kraft paper and semi-stretched kraft paper, white paper, white release paper, yellow release paper, single/double-sided art paper, roll paper and pulp including food paper, etc. Includes a paper base consisting of.

It is preferable to remove various foreign substances from the outside of the base paper roll before disassembling the wrapping paper and mounting it on the supply roll of the manufacturing apparatus.

[Calendaring]

The calendering in the present invention is a part of the process of replacing the function performed by the primer coating layer interposed between the paper substrate and the release agent layer in the existing release paper.

In calendering, water is first supplied to the paper substrate so that the water content is in the range of 4 to 7% and passed through a multi-stage pressing roll heated to a temperature of 70 to 140°C. At this time, it is preferable that a pressure (compression force) of 25 to 50 kg/cm 2 is applied to the pressing roll in a state in which a metal (iron) roll and a rubber or Teflon roll are alternately arranged.

In the process of passing through the multi-stage pressing roll in a heated state as described above, the paper substrate exhibits an ironing effect, thereby increasing the density of the paper substrate itself, reducing thickness variation, and increasing gloss and surface smoothness. Accordingly, it is possible to uniformly apply the release agent layer applied in the subsequent process, thereby reducing the consumption of raw materials.

During the calendering, it is preferable to maintain the pressing roll passing speed of the paper substrate in the range of 300 to 1800 m/min, and the temperature of the pressing roll is applied differently depending on the basis weight of the paper substrate. In the case of a basis weight, 70 to 80 ° C., in the case of a medium basis weight of 70 to 100 g/m2, 90 to 110 ° C., and in the case of a high basis weight of 110 g/m 2 or more, the range of 110 to 140 ° C. is appropriate. If it is out of the appropriate temperature range for each basis weight, gloss and smoothness are lowered, so that the amount of raw material used is increased, and it may be difficult to obtain a predetermined peeling force.

[Corona treatment]

Corona treatment in the present invention increases the surface energy of the paper substrate to increase the adhesive force of the release agent layer (silicone) applied thereon, and prevents the occurrence of rub-off on the surface of the release paper while improving curing performance. function.

The corona treatment transmits high-voltage electrons to the surface of the paper substrate to create a roughness of several tens of nanometers on the surface, and the bonding force between the silicone release agent layer applied thereon and the paper substrate is strengthened, so that the external force is applied to the surface of the release paper. Even if it acts (eg, rubbing or contact with an organic solvent), it serves to prevent the so-called rub-off phenomenon in which the silicone release agent layer peels off and separates from the paper substrate.

Such a corona treatment machine is composed of a bar station, a frame silicon roll, and a roll sensor, and outputs a high frequency of 25 Kv at an oscillation frequency of 20 to 50 KHz. 30-40 dine, 70-100g/m2, 45-60dine, 110g/m2, 60-75dine.

[Application of release agent layer]

As the composition of the release agent layer in the present invention, all existing compositions including silicone-based compositions may be used. As an example of a preferred release agent layer composition, a silicone release agent layer composition in which a crosslinking agent, a catalyst, and a release force controlling agent are added to polydimethylsiloxane (PDMS), and other conventional release agent layer compositions for release agents including silicone-based agents may be applied. can

The paper substrate to be supplied after completing the calendering and corona treatment may be coated with a release agent layer through a reverse 5-stage roll device. The reverse 5-stage roll is easy to control the amount of application of the liquid release agent layer composition, and is particularly suitable for high-speed operation.

And, the finally obtained release agent layer application thickness, adhesive force, and adjustment of the peeling force can be made through the control of the operation of the reverse 5-stage roll and the composition of the release agent layer, in particular, the content of the release force adjusting agent, and the like.

The configuration showing the difference in the silicone coating process of the present invention compared to the conventional coating process is that the coating speed, that is, the moving speed of the paper substrate passing through the reverse 5-stage roll, is relatively high compared to the conventional one. To explain this in more detail, the coating speed of the release agent layer in the conventional release paper manufacturing process is 40 to 250 m/min, but in the present invention, 300 to 1800 m/min, which is much faster than this, is preferable. The reason and effect of making the coating speed (or the speed of passing through the paper substrate) high in this way will be explained in the molding step as a subsequent subsequent process involved.

The application amount of the release agent layer is 0.4 to 3.0 g/m 2 in the same range as in the conventional release paper, and it varies depending on the point of use of the point/adhesive tape used for the release paper, and the material and use laminated with the point/adhesive agent.

[Cure]

As soon as the application of the release agent layer is completed, it is passed through a drying furnace installed in the movement path of the paper substrate for curing and drying the pressure-sensitive adhesive layer. The drying furnace is heated by LNG combustion with a length of 40 to 50 m. In particular, it is preferable to install a far-infrared heater in parallel to the 20 m section of the entrance to maintain a high temperature of 180 to 200 ℃.

On the other hand, the moving speed of the paper substrate coated with the release agent layer passing through the drying furnace is maintained at the same speed (300 ~ 1800 m/min) as the release agent layer application, that is, the silicone coating speed in the previous step. The penetration of the silicone liquid applied to the paper substrate toward the paper substrate is prevented by passing through the inlet high temperature portion.

[Re-humidification]

The re-humidification process of the present invention is a process for reducing the moisture in the paper substrate to its original moisture content as it dries as the moisture in the paper substrate evaporates while being exposed to high temperatures while passing through the drying furnace in the curing process. After the re-humidification process, the moisture content of the paper substrate varies slightly depending on the type of paper, but is preferably in the range of 4.0 to 6.5%.

As such, the release paper that has undergone the re-humidification process improves the quality of the release paper itself by improving the imbalance distributed in the paper width, increasing the tensile force, and preventing curling (curling) during the point/adhesive work.

On the other hand, Figure 1 is a manufacturing process diagram showing the entire process from the supply of the paper substrate to the winding step of the release paper is completed by synthesizing each step of the process of the present invention.

The paper substrate 2 continuously supplied from the supply roll 1 passes between the iron roll 4a and the rubber roll 4b, which rotate while being engaged with each other under pressure through the moisture supply unit 3, and calendering by compression. this will be done At this time, at least one of the rolls 4a and 4b is maintained at a high temperature, and in the process of passing these rolls in a heated state in compression contact, the paper substrate 2 has a smoothing and thickness of the substrate surface due to the ironing effect. A decrease in deviation and an increase in gloss are achieved.

Subsequently, the calendered paper substrate 2 has a fine surface roughness as a result of forming grooves of several tens of nano diameters on the surface by the high frequency applied while passing through the corona treatment machine 5, and a silicone release agent applied thereafter. It contributes to strengthening the bonding strength of the layers.

The paper substrate 2 exiting the corona treatment machine 5 is calendered and corona treated by the reverse 5-stage roll 6 for coating the silicone release agent layer, and the silicone release agent layer is applied on one surface of the completed paper substrate 2 will lose At this time, the adjustment of the application amount of the release agent layer is made through the control of the reverse 5-stage roll 6 and the viscosity of the silicone composition.

The paper substrate 2 coated with the silicone release agent layer is dried and molded while passing through a drying furnace 7 installed on an adjacent subsequent movement path at high speed. At this time, a far-infrared heater 7a is installed in the inlet section of the drying furnace 7 so that the inlet internal temperature is maintained relatively high in addition to the heating by the original LNG combustion, so that it is introduced into the drying furnace 7 By instantaneously heating the release agent layer of the paper substrate 2, molding is induced in an instant without penetration of the release agent layer into the inside of the paper substrate.

Subsequently, the paper substrate 2 with the release agent layer formed after exiting the drying furnace 7 is re-humidified to an appropriate level of moisture content range (4.0 to 6.5%) while passing through the humidifier 8, and then finally the winding roll 9 ) will be caught in

The present invention provides a quality equivalent to that of a release paper having a primer coating layer interposed therebetween through the pretreatment of the paper substrate before and after the formation of the release agent layer on the paper substrate and the improved release agent layer curing process without forming the primer coating layer. indicates characteristics.

In addition, the present invention is almost perfect because the used release paper is easily dissociated from the pulp and separated from a very small amount of the silicone adhesive component as a thin silicone release agent layer is directly coated on the surface of the paper substrate without a primer coating layer acting as an obstacle to the recycling of the release paper. Since the release paper can be recycled, it has the advantage of being eco-friendly.

In addition, since the release paper produced by the method of the present invention is dissolved in water and regenerated into paper again and utilized, the release paper containing the conventional primer coating layer is discarded and incinerated, adversely affecting the atmospheric environment and wasting forest resources for pulp. It is expected as a useful invention that can solve the problems that used to work as a single stroke.

1 is a flow chart of a release paper manufacturing process according to an embodiment of the present invention.

Based on the method of the present invention, Example release paper was prepared as follows.

First, as a paper substrate, a general kraft paper having a basis weight of 70 g/m 2 was used to prepare a release paper for an adhesive tape use. The moisture content of the paper substrate was measured before input into the manufacturing apparatus and it was found to be 6%.

Moisture was supplied immediately before the paper substrate supplied from the winding roll was put into the calendering process, so that the calendering process was performed while maintaining the moisture content of 7% with the moisture content increased by 1%.

The pressing roll used for calendering was passed through the paper substrate in a state where a pressure (compression force) of 40 kg/cm 2 was applied while the temperature was maintained at 110°C. The speed of passing through the pressing roll of the paper substrate was set to 350 m/min.

Then, the corona treatment was performed to 50 dine on the paper substrate using a corona treatment machine that outputs a high frequency of 25 Kv with an oscillation frequency of 40 KHz.

Next, a silicone solution having a viscosity of 400 cps as a silicone release agent layer composition to which a crosslinking agent, a catalyst, and a release force control agent are added to polydimethylsiloxane (PDMS) was coated on a paper substrate with a coating thickness of 1.0 μm using a reverse five-roll coater.

The paper substrate coated with the release agent layer was passed through a drying furnace to form the release agent layer. At this time, the inlet temperature of the drying furnace in which the far-infrared heater was installed in parallel was 185°C.

Finally, the release paper specimen of the present invention was prepared by supplying moisture such that the moisture content of the paper substrate became 6%, which is the state before the first process, through re-humidification.

[evaluation]

The release force (tesa 7475, g/25mm) was measured for the sample specimen having an adhesive thickness of 1.0 μm prepared according to the method of the present invention, and the light peeling level was 8 g/25 mm.

[Rub Off]

The release paper of the present invention is interposed between the paper substrate and the release agent layer and as there is no primer coating layer as an intermediate layer to bond them, the rub-off phenomenon in which the surface silicone release agent layer is separated from the surface of the paper substrate by an external force is the key. and the following tests were performed.

By the method of the present invention, it was examined whether the silicone release agent layer was peeled off by rubbing the surface of the sample of the present invention having the same coating thickness of the silicone release agent layer as the basis weight and the comparative example specimen having the primer coating layer interposed therebetween by the method of the present invention. It was observed that the specimens were not susceptible to rub-off compared to the comparative specimens.

Claims (5)

supplying a paper substrate;
A calendering step of supplying moisture to the paper substrate so that the water content is in the range of 4 to 7%, heating to a temperature of 70 to 140° C., and passing a multi-stage pressing roll to which a pressure of 25 to 50 kg/cm 2 is applied;
Corona treatment with a high frequency of 25Kv of 20 ~ 50KHz oscillation frequency in a corona treatment machine with 30 ~ 75dine;
A silicone-based release agent layer is applied to the surface of the paper substrate using a reverse five-roll coater, wherein the passing speed of the paper substrate is 300 to 1800 m/min, and the application amount of the release agent layer is 0.4 to 3.0 g/m. step;
A forming step of passing a drying furnace having an inlet 20m section of 180 to 200 ℃ at a speed of 300 to 1800 m/min; and
re-humidifying so that the moisture content is in the range of 4.0 to 6.5%;
A method for producing a renewable release paper, characterized in that consisting of. The method of claim 1, wherein the pressing roll comprises a metal roll and a rubber or Teflon roll alternately arranged. The method according to claim 1, wherein the temperature of the pressing roll is 70 to 80°C if the basis weight of the paper substrate is 35 to 60 g/m2, 90 to 110°C if 70 to 100 g/m2, and 110 to 140°C if 110 g/m2 or more. A method for producing a renewable release paper comprising: The method according to claim 1, wherein the drying furnace is heated by LNG combustion having a length of 40 to 50 m, and a far-infrared heater is installed in parallel in a section of 20 m at the inlet side. A recyclable release paper produced by any one of claims 1 to 4.

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