JPH09176999A - Production of glassine paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain glassine paper exhibiting excellent releasing property even in solvent-free type releasing agent applied in a small coating amount and capable of re-utilizing as waste paper-regenerated pulp by applying a coating composition consisting essentially of a water-soluble polymer to base paper plural times and carrying out pressurizing treatment of the coated paper. SOLUTION: A coating composition consisting essentially of a water-soluble polymer such as polyvinyl alcohol having >=1,500 polymerization degree and >=80mol% saponification degree is applied onto raw paper plural times so that coating in final time is carried out so as to provide a layer having excellent barrier property using a bar coater and the coated paper is subjected to pressurizing treatment by various kinds of calender such as super-calender to provide the objective glassine paper.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing glassine paper. More specifically, it relates to a method for producing glassine paper suitable for a base material of a release paper used in combination with an adhesive sheet. More specifically, it is a method for producing glassine paper which has excellent releasability even when a solvent-free release agent is used as a release agent and can provide a release paper which can be reused as waste paper pulp. .

[0002]

2. Description of the Related Art Adhesive sheets are generally composed of a surface base material, an adhesive and release paper, and are used for a very wide range of purposes such as commercial, office and household purposes, such as labels, stickers, stickers and patches. It is used after being processed into the shape of.
As the surface base material, depending on the type, high-quality paper, coated paper, cast coated paper, general paper such as thermal recording paper, aluminum foil laminated paper, aluminum vapor-deposited paper, resin-impregnated paper, special paper such as synthetic paper, PET, etc. Films such as polypropylene, polypropylene and polyvinyl chloride are used. A lot of rubber and acrylic adhesives are used. Especially, acrylic mainly composed of acrylic acid ester and acrylic acid, methacrylic acid, acrylamide, vinyl acetate, styrene, acrylonitrile, etc. The number of system adhesives is increasing.

Release papers can be classified into polyethylene laminate type, glassine type, clay coat type, water-based resin coat type, film base type, etc. Among them, polyethylene laminate type and glassine type are widely used.

The polyethylene laminate type laminates polyethylene on the surface of the base paper for the purpose of preventing penetration of a release agent such as silicone into the interior of the base paper such as high-quality paper or kraft paper, or for the purpose of effectively exhibiting the release performance. It is treated and a release agent layer is provided thereon.
Since the release agent is completely retained on the polyethylene layer formed on the high quality paper or kraft paper which is rich in voids, it has an advantage of effectively exhibiting the release performance.

However, since high-quality paper or kraft paper is used as the release paper base material, it has a poor optical transparency and causes a problem in label position detection by a labeler having a transmission type position detector. Further, since polyethylene is laminated on the release paper base material, the recycled paper cannot be re-dispersed in water at the time of disaggregation and cannot be regenerated.

On the other hand, the glassine type is a glassine paper obtained by paper-making from chemical pulp that has been subjected to a high degree of beating treatment and further densified with finishing equipment such as a super calender, and provided with a release agent such as silicone. is there. Since the glassine type release paper is excellent in light transmittance, it has an advantage that it can be applied to a labeler having a transmission type position detector. Further, since the release paper has a relatively thin paper thickness, it has a feature that it can have a large winding area and a large area for a case. Recently, while further improving the transparency so as not to cause problems in label position detection with a labeler having a transmission type position detector, the penetration of release agent into the inside of the base material is suppressed as much as possible.
A method of applying a polyvinyl alcohol-based resin aqueous solution to the surface of the base paper has been adopted for the purpose of allowing the release agent to be held on the surface of the base paper so that effective release performance is exhibited.

However, when the aqueous solution of polyvinyl alcohol resin is applied, most of the coating composition penetrates into the inside of the base material and is filled, so that sufficient barrier properties cannot be obtained. Further, the suppression of penetration of the release agent and the covering (coverability) of the surface of the substrate with the release agent are insufficient. In order to provide a high-quality release paper comparable to the laminate type, it is necessary to increase the amount of the release agent applied or to apply a large amount of the polyvinyl alcohol-based resin aqueous solution to improve the barrier property. An expensive release agent cannot actually increase the coating amount, and a method of increasing the coating amount of the polyvinyl alcohol-based resin aqueous solution is adopted, but the release paper impregnated with a large amount of the polyvinyl alcohol-based resin aqueous solution is recycled. As a raw material for paper, it cannot be easily redispersed in water during disintegration.

From the background of the importance of environmental protection and resource protection, release paper has good disintegration property that can be used as a raw material for recycled paper, and is also used for label position detection by a labeler having a transmission type position detector. A release paper having a problem-free light transmission has not yet been found.

On the other hand, as the release agent, silicone resin,
There are fluororesins, aminoalkyd resins, polyester resins and the like, which are used as an emulsion, solvent type or solventless type, and most of them are silicone resins. At present, it is general to apply a release agent diluted with a solvent, a so-called solvent-type release agent, to a release paper substrate. The reason is that when the release agent is applied, the fluidity is appropriately adjusted by diluting with a solvent to form a uniform layer of the release agent film on the surface of the base material and maximize the performance of the release agent. Has been used to take advantage of the ease of doing things. However, in recent years, there have been strong demands for safety and pollution, and solvent-free release agents have been strongly demanded from the viewpoint of maintaining the health of workers.

By the way, when a solvent-based release agent is actually applied to a release paper substrate, a large amount of liquid is applied because the release agent is diluted with a solvent, while a solventless release agent is applied. When applied to a release paper substrate, the amount of liquid applied is small because no solvent is used. Therefore, when using a solvent-free release agent, a thinner uniform release agent film must be formed on the release paper substrate as compared to the solvent release agent. When applied to conventional glassine paper, it was difficult to form a uniform layer of the release agent film. In such a state, unevenness or minute voids are formed on the release agent layer on the surface of the glassine paper, and the adhesive enters the recesses or voids in the step of forming the adhesive layer on the release agent layer. After forming the pressure-sensitive adhesive sheet by laminating the surface base material in the step of, the force (hereinafter referred to as peeling force) applied when peeling the surface base material with the adhesive layer becomes extremely heavy, and the surface base material is It causes troubles such as tearing and becomes a very serious problem in terms of workability and quality.

For the above reasons, development of a low-cost base material for release paper, which suppresses the penetration of a solvent-free release agent, which is excellent in terms of safety and pollution, and forms a uniform thin film on the surface of the base material, has been strongly pursued. Although there is a strong demand for releasable release papers for the protection of forest resources, at present, there is no release paper that can sufficiently meet these requirements.

[0012]

Thus, there is provided a release paper which has excellent releasability even when a solventless release agent is used as the release agent, and which can be reused as waste paper pulp. Provided is a method for producing glassine paper that can be produced.

[0013]

The present inventors have made a detailed analysis of the polyethylene function of a conventional release paper substrate laminated with polyethylene in order to suppress the penetration of a solventless release agent into glassine paper. As a result, (1) The permeation of the solvent-free release agent is suppressed in the base paper that is manufactured from wood pulp as the main raw material, has fine pores with a pore size of 0.1 to 1.0 μm, and is porous and highly absorbent. And (2) to simultaneously prevent the scattering of voids having a pore size of 1 to 200 μm in the base paper, the effect of obtaining a performance comparable to polyethylene laminated paper by forming a coating layer I reached the view that it was an effective means.

The inventors of the present invention have conducted further intensive studies to establish this means, and as a result, the glassine paper obtained by coating the polyvinyl alcohol resin in a plurality of times has excellent barrier properties, It has excellent releasability even for release paper using a solvent-free release agent, and exhibits sufficient release performance even with a small amount of release agent applied, and release paper as a waste paper material. It was found that

The present invention provides a method for producing glassine paper in which a base paper is coated with a coating composition containing a water-soluble polymer as a main component and then pressure-treated to finish the coating composition. This is a method for producing glassine paper, which is characterized in that it is carried out in batches.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the water-soluble polymer used in the present invention include polyvinyl alcohol, polyurethane ionomer, urethane / olefin composite resin, polypropylene resin, ethylene resin, colloidal silica composite resin, and the like. They can be used alone or in combination. Among them, polyvinyl alcohol-based resins are preferable because they have excellent film-forming properties and excellent barrier properties. The polyvinyl alcohol-based resin is generally referred to as Poval. The basic composition is a copolymer of vinyl alcohol and vinyl acetate.

Particularly, a polyvinyl alcohol resin having a polymerization degree of 1500 or more and a saponification degree of 80 mol% or more has few acetic acid groups having poor hydrophilicity and forms a highly continuous film by hydrogen bonding. Since the polyvinyl alcohol-based resin on the base paper is excellent in continuity because it contains a large number of hydroxyl groups for exerting its ability, silicone can be retained on the base paper surface and effective release performance can be exhibited, which is preferable. . As such a polyvinyl alcohol-based resin, it is possible to arbitrarily select and use a resin satisfying the above requirements from commercial products,
For example, "GH17" and "GH2" of Nippon Synthetic Chemical Industry Co., Ltd.
0 ”is commercially available.

Pigments and other adhesives can be appropriately mixed in the coating liquid containing the water-soluble polymer as a main component. Examples thereof include inorganic pigments and organic pigments such as kaolin, clay, aluminum hydroxide, heavy calcium carbonate, light calcium carbonate, titanium dioxide, chisan white, talc, plastic pigment, zinc oxide, calcium sulfate and barium sulfate. . Of course, two or more kinds of pigments can be used together.

As the adhesive, modified starch,
Examples thereof include polyacrylamide resins, styrene-butadiene copolymer latex emulsions, styrene-acrylic copolymer latex emulsions and acrylic ester resin systems. However, in order to exert a sufficient sealing effect by the polyvinyl alcohol resin of the present invention, the mixing ratio of these is 10 in the total solid content of the coating liquid.
It is preferable to keep it below the weight. Further, it does not cause any problem to add a small amount of additives such as a dispersant, a water-proofing agent, a lubricant, an antifoaming agent, a coloring agent and an antiseptic, if necessary.

According to the present invention, a coating solution containing such a water-soluble polymer as a main component is applied to a base paper in plural times,
The feature is that the glassine paper is finished by pressure treatment.
By adopting such a manufacturing method, not only it has excellent releasability even when used as a base material of a release paper using a solvent-free release agent as a release agent, but it also reduces the coating amount of the release agent. It is possible. Probably, by dividing the coating into at least two stages, that is, by applying the coating liquid → drying (semi-drying), coating → drying, a barrier is applied to the base paper to some extent by the first coating and drying. It is considered that this is because the coating solution is prevented from penetrating into the base paper more than necessary because the second step of coating and drying is performed after imparting the property, and the barrier layer can be efficiently formed on the surface.

The coating amount of the coating solution containing a water-soluble polymer as a main component does not increase from the conventional coating amount because the coating process is performed a plurality of times, and the total coating amount is an absolute dry weight. It is preferably 0.5 to 5 g / m ² . If the amount is less than 0.5 g / m ² , it is impossible to sufficiently coat the surface of the base paper with the coating layer of the water-soluble polymer, and therefore the penetration of the solventless release agent cannot be suppressed, Further, it is impossible to stop the voids having a hole diameter of 1 to 200 μm scattered in the base paper. Further, if it exceeds 5 g / m ² , for example, the amount of expensive polyvinyl alcohol-based resin increases, which is disadvantageous in terms of cost. In addition, excess polyvinyl alcohol-based resin may cause excess polyvinyl alcohol-based resin on the dryer surface of the dryer of the paper machine or However, not only does it adhere to the surface of the roll of the super calender for smoothing the surface and cause stains in the process, but a part of the coating layer is detached, so that the desired sealing effect cannot be obtained. The first-stage coating is 5 to 50% by weight of the total coating amount.
Should be used as a guide. Further, the coating liquids in each stage may have the same composition or different compositions.

For coating the coating liquid, a generally known coating device,
For example, an on-machine coater such as a size press, a gate roll coater, a bar coater, a roll coater, an air knife coater, and a blade coater, or an off-machine coater can be appropriately used. The first-stage coating is preferably performed by a so-called on-machine coater installed inside the paper machine, and is preferably applied by a size press, a bar coater or a gate roll coater. on the other hand,
The final stage coating may be performed by either an on-machine coater or an off-machine coater, and coating with a bar coater is particularly preferable because a layer having excellent barrier properties can be obtained.

The bar coater has a metering mechanism in which a wire is wound around a cylindrical metal rod, and a target coating amount is obtained by the thickness of the wire. Generally, a rod bar, a Mayer bar and a wire bar are used. It is a coating method called "etc." In the coating step, the coating liquid coated on the surface of the substrate passes through the capillary of the substrate by the measuring mechanism,
Penetrates inside the substrate. For example, in a blade coater, pressure penetration occurs due to the tip pressure of a blade that is a measuring mechanism, and in a roll coater, when a base material coated with a coating liquid passes between rolls, pressure is applied by a nip pressure. Penetration occurs. When such pressure permeation occurs, the permeation of the coating liquid into the base material becomes excessive, and it tends to be difficult to sufficiently coat the base paper surface with the coating layer of the water-soluble polymer. The use of fewer bar coaters is preferred.

The glassine paper is mainly composed of a strongly beaten chemical pulp as a raw material for papermaking, is paper-made with acidity or neutrality, and is coated with the above water-soluble polymer in plural times.
For example, various calenders such as a super calender, a gloss calender, and a soft compact calender are used for compression processing to finish. Note that the calendar may be on-machine or off-machine.

As the pulp, for example, a softwood chemical pulp using a high-grade softwood material such as spruce or hemlock is most suitable. , Synthetic pulp, etc. are appropriately mixed and blended to take advantage of their characteristics. The beating degree of pulp is 150 ml in Canadian Standard Freeness (hereinafter, CSF)
When beaten strongly below, oil resistance and transparency are improved. However, since papermaking properties and humidity dimensional stability tend to occur, it is possible to keep the CSF to a medium beating level of 200 to 400 ml and use a size press or the like to assist the glassine quality characteristics. Further, various additives such as a sizing agent, a paper-strengthening agent, a drainage agent, a dye and the like can be adjusted and mixed into the papermaking raw material. The compression treatment with a super calendar or the like is performed by adjusting the conditions such as pressurization, temperature, speed and paper moisture.

Incidentally, the smoothness of the glassine paper is adjusted so that the value measured by the Oken smoothness tester manufactured by Asahi Seiko Co., Ltd. is not less than 500 seconds to form a uniform thin film of the release agent. The base material for release paper is completely covered and the release property can be maximized.

A glassine release paper can be obtained by applying a release agent to the glassine paper thus obtained. As the release agent, known solvent-free or solvent-based release agents can be used, but they are suitable because they can sufficiently cope with solvent-free silicone release agents that require a thin uniform release agent film. . Examples of the solvent-free silicone release agent include heat-curable, ultraviolet-curable and electron beam-curable release agents. As a coating device for forming the release agent layer, various coaters for coating the release agent such as a roll coater and a gravure coater, or a printing machine is appropriately used. Also,
The amount of release agent applied is 0.2 to 3.0 g per dry side, considering that it will be reused as recycled pulp.
It is desirable to adjust it so that it is in the range of about / m ² .

The glassine paper obtained according to the present invention is suitable as a base material for release paper due to its excellent solvent resistance, but it is also excellent in grease resistance for food packaging,
It can also be used as a container lining.

[0029]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited by these examples. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight", respectively.

Example 1 (1) Production of glassine paper First, a paper stock having the following composition was prepared. Component weight Softwood bleached kraft pulp (beating degree: 420 ml) 20 parts Hardwood bleaching kraft pulp (beating degree: 420 ml) 80 parts 50% talc dispersion 10 parts 30% Reinforced rosin sizing agent (trademark: SPE, Arakawa Chemical Industry Co., Ltd. Made) 0.3 part 30% aluminum sulfate 2 parts

Next, a raw paper having a rice basis weight of 80 g / m ^{2 was made} from this paper material by a long-mesh multi-cylinder paper machine. In addition, a polyvinyl alcohol resin (trademark: G was used by a bar coater installed in the middle part of the dryer of the fourdrinier paper machine.
H20, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., degree of polymerization 1800) 6
As a primary processing, the coating liquid (%) was applied to one surface of the above-mentioned base paper so that the dry weight became 0.6 g / m ² , and dried. Further, as a secondary processing, after the primary processing, the surface of the raw paper was coated with this 6% solution by an on-machine bar coater so that the dry weight was 0.6 g / m ² and dried. Then, it was treated with a super calender to obtain glassine paper with Oken type smoothness of 520 seconds.

(2) Manufacture of release paper Addition reaction type solventless silicone (trademark: KNS-320,
Shin-Etsu Chemical Co., Ltd.) 100 parts, platinum catalyst (trademark: PL-
56, manufactured by Shin-Etsu Chemical Co., Ltd.) to prepare a solventless release agent solution having a composition of 2 parts. The release agent was applied onto the coated layer of the glassine paper by a gravure coater so as to have a weight of 0.5 g / m ² and cured with hot air to obtain a release paper.

Example 2 Glassine paper and release paper were prepared in the same manner as in Example 1.
However, the coating amount of the coating liquid of Example 1 was 2 g / m ² with an on-machine size press as the primary processing and 1.4 g / m ² with an on-machine bar coater as the secondary processing.

Example 3 Glassine paper and release paper were prepared in the same manner as in Example 1.
However, a polyvinyl alcohol resin (trademark: PVA117, manufactured by Kuraray Co., Ltd., polymerization degree: 1700) was used in place of the polyvinyl alcohol resin (trademark: GH20) as a component of the coating liquid of Example 1.

Example 4 Glassine paper and release paper were prepared in the same manner as in Example 1.
However, instead of the solvent-free release agent of Example 1, 100 parts of ultraviolet curable solvent-free silicone (trademark: BY24-551A, manufactured by Toray Dow Corning Silicone Co., Ltd.), platinum catalyst (trademark: BY24-551B, A release agent having a composition of 30 parts by Toray Dow Corning Silicone Co., Ltd. was used, and this release agent solution was applied to the coating layer of the release paper substrate described in Example 1 at 0.5 g / m ² . Was coated with a multi-stage roll coater so as to be cured, and cured with ultraviolet rays to obtain a release paper.

Example 5 Glassine paper and release paper were prepared in the same manner as in Example 1.
However, instead of the polyvinyl alcohol resin (trademark: GH20) as a component of the coating liquid of Example 1, a 15% polyvinyl alcohol resin (trademark: PVA117, manufactured by Kuraray Co., Ltd.,
Polymerization degree 1700) 100 parts, 50% Kaolin (trademark: H
A coating liquid consisting of 8 parts of T clay, manufactured by Engelhard Co., Ltd. was used.

Example 6 Glassine paper and release paper were prepared in the same manner as in Example 1.
However, instead of the polyvinyl alcohol resin (trademark: GH20) as a component of the coating liquid of Example 1, a 15% polyvinyl alcohol resin (trademark: PVA117, manufactured by Kuraray Co., Ltd.,
A coating liquid consisting of 100 parts of a polymerization degree of 1700) and 8 parts of 20% oxidatively modified starch (trademark: Oji Ace A, manufactured by Oji Cornstarch) was used.

Example 7 Glassine paper and release paper were prepared in the same manner as in Example 1.
However, the coating liquid of Example 1 was subjected to primary processing with an on-machine size press coater and secondary processing with an off-machine bar coater.

Example 8 Glassine paper and release paper were prepared in the same manner as in Example 1.
However, instead of the polyvinyl alcohol resin (trademark: GH20) as a component of the coating liquid of Example 1, a coating consisting of 15% polyvinyl alcohol resin (trademark: GM14, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polymerization degree: 1400). The liquid was used.

Comparative Example 1 The coating liquid of Example 1 was applied once using a bar coater,
Coating amount 1.2g / m ^TwoAs in Example 1 except that
Then, glassine paper and release paper were produced.

Comparative Example 2 The coating liquid of Example 1 was once coated using an on-machine size press coater and peeled from glassine paper in the same manner as in Example 1 except that the coating amount was 1.2 g / m ^2. Paper was made. Comparative Example 3 Example 1 except that the coating liquid of Example 1 was applied once using a gate roll coater and the coating amount was 1.2 g / m ^2.
Glassine paper and release paper were prepared in the same manner as in.

Comparative Example 4 A release paper was prepared in the same manner as in Example 1, and its evaluation test was carried out.
Was done. However, the coating amount of the coating liquid of Example 1 was first processed.
On machine bar coater as 0.1g / m ^Two,secondary
Off-machine bar coater for processing 0.1g / m^TwoWhen
did.

Comparative Example 5 A release paper was prepared in the same manner as in Example 1 and its evaluation test was conducted. However, the coating amount of the coating liquid of Example 1 was 3.5 g / m with an on-machine size press coater as the primary processing.
^2, 2 g / m in off-machine bar coater as secondary processing
^{2 were} applied.

A predetermined piece of paper was prepared from the above release paper, and the covering property, disintegration property and release force of the release agent layer were measured and evaluated by the following methods, and the results are shown in Table 1.

"Coverability of release agent layer" A commercially available oil-based pen was used to uniformly coat the release agent layer of 10 cm ² of release paper, and the spotted pinholes observed on the opposite surface were observed and the coating was performed. The effect was judged. [Evaluation Criteria] O: None was observed. Δ: A considerable number of pinholes were seen, which was a level at which there was a problem in practical use. X: Pinholes were seen on the entire surface.

"Disaggregation" Regarding disaggregation in recycled pulp recycling, the obtained release paper was disaggregated by a standard disintegrator defined in JIS P 8209, and the dispersion state at a count of 5000 was observed. The disaggregation was evaluated. [Evaluation Criteria] O: Complete disaggregation. Δ: Partially not disintegrated. ×: Not disintegrated at all.

"Peeling Power" An acrylic emulsion pressure-sensitive adhesive (trademark: Nikasol L-145, manufactured by Nippon Carbide) was coated on the above-mentioned release paper with a reverse roll coater so that the dry weight was 25 g / m ^2, and the peeling force was adjusted to 130 ° C. The adhesive paper was obtained by drying with a hot-air drier and bonding high-quality paper with a basis weight of 64 g / m ^{2 to each} other. A sample of 10 cm x 5 cm whose long side is the flow direction of the paper machine is prepared from this adhesive paper, and INTESCO
The peeling force when peeled at a tensile angle of 180 degrees in the flow direction was measured under a test condition of Model 2001 with a peeling speed of 0.3 m / min. (Unit: g)

[0048]

[Table 1]

[0049]

The glassine paper obtained according to the present invention can be easily produced by the existing paper machine and coating machine, and is safe.
It is possible to directly apply a solvent-free release agent, which is excellent in terms of pollution, in a low coating amount, and is useful as a base material for release paper which is extremely practical and can be sufficiently reused as recycled pulp of used paper.

Claims (3)

[Claims] 1. A method for producing glassine paper in which a base paper is coated with a coating composition containing a water-soluble polymer as a main component and then pressure-treated to finish the coating composition coating a plurality of times. A method for producing glassine paper, characterized in that the steps are performed separately. 2. The method for producing glassine paper according to claim 1, wherein the apparatus for finally applying the coating composition is a bar coater. 3. The method for producing glassine paper according to claim 1, wherein the water-soluble polymer is polyvinyl alcohol having a polymerization degree of 1500 or more and a saponification degree of 80 mol% or more.