JPS6297998A - Manufacturing method of base paper for release paper - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention can be applied to a release paper base paper without any special pre-processing.
This paper relates to paper that can be directly coated with a release agent (hereinafter abbreviated as direct coating base paper).
By coating this liquid in the form of fine bubbles, it is possible to provide a high-performance and inexpensive base paper for direct coating.

[Conventional technology]

In general, release paper is of the polyethylene type, in which paper is laminated with polyethylene and a release agent is applied on top of it, the clay coat type, in which the paper is clay-coated and sealed, and a release agent is applied to the L of the paper. It is classified as a direct coating type in which the remover is applied directly.

Among these, the direct coating type is used for many purposes because it is excellent in heat resistance and economical efficiency. This base paper for direct coating requires high barrier properties and excellent dimensional stability. The former means that a release film layer is formed on the surface layer of the paper and it is smooth, and release agents such as silicone resin, polyester resin, amino alkyd resin, and fluororesin do not penetrate into the inside of the paper layer and are effective on the surface. It is coated as a thin film and is necessary to exhibit excellent peelability. The latter is also an extremely important property, as it means that there will be no problems caused by expansion and contraction of the paper due to changes in humidity, such as curling during the release agent application and drying process, or curling after adhesive processing to make adhesive paper. be.

In order to satisfy these required characteristics,
In No. 6-, a mixed aqueous solution of polyvinyl alcohol and styrene/maleic anhydride copolymer is coated using an on-machine size press, and in JP-A-60-110999, a low molecular weight solution is applied at a high concentration of 20 to 40%. It has been shown that starch alone or in combination with a water-proofing agent or a sizing agent can also be used for size press coating. In addition, JP-A No. 5
No. 9-14493 describes that high barrier properties can be imparted by applying a water-soluble coating solution in two stages using a size press and a calendar size press.

[Problems to be Solved by the Invention] However, since paper is a porous base material, when a chemical capable of imparting barrier properties is applied as an aqueous solution using a size press or the like, penetration into the inside of the paper layer progresses. Therefore, in order to form a film on the surface layer and impart barrier properties, a large amount of chemicals must be applied, including the amount that penetrates into the paper layer. In order to suppress such penetration into the inside of the paper layer, it is possible to strengthen the beating of the raw material pulp and increase the density of the paper, but this will impair the dimensional stability required for base paper for direct coating. be exposed. On the other hand, from the viewpoint of process stability, it is better to weaken the beating of the raw material pulp, but since the paper layer structure becomes porous and the coating liquid easily penetrates, it becomes difficult to impart barrier properties.

As a result of extensive research into a method for satisfying the contradictory properties of barrier properties and dimensional stability, the present invention was achieved. The present invention will be explained in detail below.

[Means for solving problems]

The present invention has a surface tension of 6°dyn/containing a water-soluble polymer.
After foaming a foaming composition liquid of 4 or less to a foaming ratio of 5 times or more, applying it to paper at the try end of a paper machine, and immediately crushing the foam by physical means such as roll nip pressure or blade pressure. It has been found that drying, or performing foam breaking and drying in the same drying process, is an effective means of suppressing penetration into the paper layer, forming a continuous film on the surface layer, and imparting barrier properties. It is something.

In other words, instead of using a conventional aqueous solution, it is mixed with air to form fine bubbles to increase viscosity and suppress penetration into the paper layer, effectively adding barrier properties to the paper layer with a small coating amount. It is characterized by the production of direct-coated Kamikawara paper that has dimensional stability and barrier properties by effectively surface-treating even paper with many voids made from pulp that has been treated or beaten to a reduced degree. .

[Effect]

In order to make an aqueous solution foam, it is necessary to lower the surface tension of the aqueous solution by adding a substance with surface activity, and surfactants such as ammonium stearate and ammonium lauryl sulfate are generally added as foaming agents. be done. However, when a low molecular weight surfactant such as this is added to the paper, the sizing properties expressed by the internally added sizing agent may be reduced.

This has a large negative impact on paper quality, such as weakening paper strength.

It is not desirable to use it for foam coating on paper. In addition, the protein foaming agent described in JP-A No. 54-2403 does not have a negative effect on size properties or paper strength, but it does not have the function of imparting properties such as barrier properties and size properties to paper, and it is susceptible to decay. Due to its drawbacks, it is not suitable for producing the release paper base paper in the present invention.

In the present invention, the surface tension containing the polymer aqueous solution is 60 dyn/
By mechanically stirring a foamable liquid composition having a particle size of less than cn with air, foaming is made possible, and the above problems are solved at once.

Table 1 shows the surface tension and foaming properties of various aqueous solutions in the following margins. Surface tension is a value measured by the Wilhelmy method (hanging plate method).
Foaming property is an evaluation of the degree of foaming by mechanical stirring. The foaming composition liquid referred to in the present invention includes polyvinylsilcol as a foaming agent, styrene/maleic acid copolymer, diisobutylene/maleic acid copolymer, acrylic resin, starch as a foam stabilizer, or starch. Derivative 2 This is a solution containing at least one type of cellulose derivative. As is clear from Table 1, in order to foam, it is necessary to contain at least one of polyvinyl alcohol, styrene/maleic acid copolymer, diisobutylene/maleic acid copolymer, and acrylic resin. That is, it is possible to foam not only with an aqueous solution alone, but also with a solution such as starch or carboxymethylcellulose aqueous solution, which has a surface tension of around 7° dyn 70 and does not exhibit foaming properties. Furthermore, these water-soluble polymers are generally commercially available as barrier agents or sizing agents and can be easily obtained.

On the other hand, starch and carboxymethylcellulose do not have foaming properties as mentioned above, but have high viscosity, so they strengthen the foam film and contribute to foam stabilization. Other starch derivatives, cellulose derivatives and sodium alginate also act as foam stabilizers. Normally, foam breaks down over time, but the foam used in the present invention must remain stable until it is mechanically crushed after it is generated and transferred to a coating device and coated on paper. Therefore, it is often desirable to use not only a water-soluble polymer as a foaming agent, but also a foam stabilizer.

By stirring the above-described foamable liquid composition while blowing air, the liquid changes into a cream-like composition composed of foam particles. The foaming ratio is a value that indicates the volume ratio of the foaming composition liquid before foaming to the volume after foaming, but by adjusting the amount of air blown in, it is possible to achieve a predetermined foaming ratio. ! ? It will be done. Table 2 has the following margin: Table 2〉 Original paper: LBKP 85%/NBKP 15% C, S,
f 450+nQ Filler in paper 12% Liquid formulation; Nissan Sizer 700 4% Kuraray Boval 1051% Sunrose F-50M CO, 2% Type B viscosity values and sizeless foam of various expansion ratios.

The air permeability is shown when such a foam is coated with a Suizu press on a high-quality paper with a basis weight of 64 g/m made of a high freeness raw material. The air permeability referred to here is J, TAPPI Nα5-
This is the value measured by B (Ouken air permeability tester) and serves as a guide for barrier properties. As shown in Table 2, as the foaming ratio increases, the B-type viscosity of the foam increases and the air permeability of the foam-coated paper tends to increase, but if the foaming ratio is too low, the viscosity of the foam becomes low; There is not much difference in air permeability compared to when liquid is applied. Therefore, in order to provide barrier properties, foam with a high expansion ratio is desirable, but a foaming ratio of at least 5 times or more is necessary.

The foam thus prepared is sent to the dry aid coating device of the paper machine. As such a coating device, a size press, a gate roll coater, a bill blade coater, or a calender roll can be used, but the present invention is not limited thereto. When coating with conventional liquids, the liquid begins to penetrate into the paper layer the moment the liquid comes into contact with the paper, and immediately after that, the liquid is squeezed out with a roll nip or scraped off with a blade. At this time, pressure is applied and further penetration progresses. On the other hand, in foam coating, the foam has a high viscosity, so even if it comes into contact with paper, it does not penetrate into the paper layer.
The bubbles coated on the paper surface are simultaneously broken and injected by roll nip pressure and blade pressure, but the degree of penetration is extremely small compared to liquid coating.

Therefore, a large amount of the coating liquid is present on the surface layer of the paper, which is then dried to form a continuous film on the surface layer of the paper. As a result, as shown in Table 2, high air permeability can be obtained with a small coating knee. In addition, when we investigated the penetration state of the coating liquid on a cross section of the paper, we found that in liquid coating, the coating liquid was distributed throughout the paper layer, whereas in foam coating, the penetration depth was shallow and it was near the surface layer. It was observed that the coating solution tends to stop at one surface layer, especially as the foaming ratio increases.

Furthermore, when coating with a liquid, it is difficult to control the coating amount, but with foam coating, it can be easily controlled by the foaming ratio as shown in Table 2. Therefore, the higher the foaming ratio, the smaller the amount of coating, which leads to a reduction in the load on the afterdryer and contributes to energy savings.

The softness of the base paper pulp used for foam coating as described above is 20.
0mlcsF and basis weight of 40g/m or more are required.

If the freeness is less than 200 mlcsF, the dimensional stability is extremely poor and it is not suitable for release paper base paper, and the basis weight is 40 g/
If it is less than m', the strength will be low and will cause many troubles such as frequent paper breakage during the process of peeling and adhesive processing, so it is preferably 40 g/m2 or more.

After drying, the paper web coated by this method is machine calendered or supercalendered to produce a base paper for direct coating with an air permeability of 3000 seconds or more and sufficient smoothness. [Obtain] IE is now available.

If the air permeability is less than 3000 seconds, the release agent will penetrate into the paper layer and a uniform thin film cannot be formed, so good release properties are 711f.
I can't.

〔effect〕

The base paper for direct coating thus obtained has a barrier property equal to or better than that of conventional liquid coated base paper with a smaller coating amount, and is an inexpensive release paper base paper. Furthermore, an effective treated surface can be obtained by performing foam coating on base paper in which the beating of the raw material pulp has been weakened. As a result,
It has become possible to produce release paper that has both good dimensional stability and good releasability.

As mentioned above, the industrial value of replacing conventional liquid size press coating with foam coating using the chemical of the present invention is extremely large.

〔Example〕

Next, the present invention will be explained in detail with reference to Examples.

Example 1 Pulp blend N-BKP 40%, L-[3KP
Using raw material pulp with a freeness of 60% and a freeness of 300 mncsf, a neutral sizing agent alkyl ketene dimer [trade name: SPK 901゜manufactured by Arayo Kagaku Kogyo ■] was added at a concentration of 0.15%.
% (based on pulp) internally added, cationic polymer, polyamide epichlorohydrin resin [Product name: Kaimen 557
11. 0.15% (based on the pulp) of Dick Bercules (manufactured by Dick Vercules) was added thereto for fixation. Obtained basis weight 60g/rr
The following foam was size-press coated on high-quality paper made by a fourdrinier machine and dried using a multi-barrel dryer. Thereafter, the water content in the paper was reduced to 10% and supercalendering was performed to obtain a base paper for direct coating.

Composition of foam: Oxidized starch [trade name: Esnancizer 700° manufactured by Ajinomoto ■] 5% (solid content concentration), polyvinyl alcohol [
Product name: Kuraray Bobal 105. ■Manufactured by Kuraray] 4% (solid content concentration), carboxymethyl cellulose [Product name: Sunrose F-50MC, manufactured by Yamaba Kokusaku Pulp Division] 0.2
% (solid content concentration) using a continuous foaming machine [product name: FINEFOAM, Newly manufactured by Suehiro Kakoki Seisakusho] to foaming ratios of 7, 12, and 20 times.
The surface tension of the liquid is measured using a surface tension measuring device 5T-1 (St(I)
55 dyn/an as measured by MADZU ■
Met.

Using this base paper for direct coating, an addition reaction type silicone solution [trade name: S-772, manufactured by Shin-Etsu Chemical Co., Ltd.] was diluted to a predetermined concentration, and the amount of silicone coated was 1.0 g using a Mayer bar coater. /m. Drying and curing conditions after silicone coating were 120° C. for 20 seconds.

Subsequently, in order to evaluate the peelability, a solvent-based acrylic adhesive [trade name; [3PS-5127, stock solution 37.5%, Toyo Ink +j! Coated using an applicator (clearance 125μ) manufactured by KYP Co., Ltd., and coated with high-quality paper [product name: KYP
.

66.3 g/m, made by Sanyo Kokusaku Pulp ■.

Peel resistance was measured. This peeling resistance is Tensilon [1
7M4C (manufactured by Toyo Baldwin ■) using a tensile testing machine under the conditions of sample width 20 nn, peel angle 180', and tensile speed 1000+nn/min. IQ was determined for both the time course and the time course.

Comparative Example 1 In the same manner as in Example 1, a foam with a foaming ratio of 4 times, a non-foaming solution, and a solution in which the concentration of the coating solution was lowered so that the coating amount after drying was the same as in Example 1 were respectively prepared. It was applied using a size press, dried and subjected to supercalender treatment. The base paper for direct coating thus obtained and the commercially available glassine type base paper for direct coating were subjected to peeling and adhesive processing in the same manner as in Example 1, and the peel resistance was measured. The results are shown in Table 3.

As can be seen from Margin Table 3 below, when the foaming ratio is high among foam-coated products (Nα1-1 to 1-3), liquid-coated products (Nol-5) are used.
A high air permeability was obtained with a small coating amount compared to the above, and the peel strength was low both immediately and over time. Furthermore, compared to commercially available glassine-type base paper for direct coating, foam with a foaming ratio of 20 times (Nal 1) shows the same level of peelability, and when the foaming ratio is lowered to 7x (NQL-3), the peeling strength increases. However, the level was such that there was no problem in practical use. However, when the foaming ratio was less than 5 times i1R (Nα1-4), there was almost no difference between liquid coating and liquid coating. When the coating amount is the same as that of foam coating (NQI 6), the air permeability is 300.
The peeling time was 0 seconds or less, the peel strength was extremely high, and the release paper could not be used for practical purposes.

Example 2 The following foam was size press coated on the same high-quality paper as in Example 1 and dried using a multi-barrel dryer.

Thereafter, the paper was subjected to a supercalender treatment with a moisture content of 10%.

Composition of foam: Oxidized starch [trade name: Varnish Sunsizer 700° manufactured by Ajinomoto N] 5% (solid content concentration), styrene-maleic acid copolymer [trade name: Polymalon 351. Manufactured by Arayo Kagaku Kogyo ■ 2% (solid content concentration), carboxymethyl cellulose [
Product name: F-50MC, made by Sanin Kokusaku Pulp ■ 0.2%
Continuous foaming machine [Product name: FI
NEFOAM (newly manufactured by Suehiro Kakoki Seisakusho) was used to foam the foam to a foaming ratio of 15 times.

Using the base paper for direct coating thus obtained, peeling and adhesive processing were performed in the same manner as in Example 1, and the peel strength was determined to be 811.

Comparative Example 2 Size press coating was performed using the same coating solution as in Example 2 in liquid form, and the peel strength was measured in the same manner as in Example 2.

The results are shown in Table 4, and as in Example 1, the foam-coated product had a higher air permeability with a smaller coating amount and exhibited better releasability.

Example 3 In this example, enzyme denaturation [denaturant α-amylase,
Product name: Klystase PA, manufactured by Yamato Kagaku Division] 18% potato starch (solid content) and diisobutylene/maleic acid copolymer [Product name: Polymalon 482. A solution consisting of 2% (solid content concentration) [manufactured by Arayo Kagaku Kogyo Division] as a foaming agent and sizing agent was foamed 15 times as much as in Example 2, and applied to the same high-quality paper as in Example 1. The paper was dried and calendered to produce directly coated 1-kawara paper, subjected to peeling and adhesive processing, and peel strength was measured.

Comparative Example 3 After size press coating using the same coating solution as in Example 3 in liquid form, a base paper for direct coating was obtained through the same process.

Further, an attempt was made to foam the starch used in Example 3 alone using the same foaming machine, but no foam was formed. However, this starch contains a foaming agent [trade name: Thaiformer F210. By adding 1% (solid content concentration) of Meisei Kagaku Kogyo ■, a foam with a foaming ratio of 15 times was obtained, which was coated with a size press and used in the same process as a base paper for direct coating. The base paper for direct coating, which had been subjected to liquid coating and foam coating containing a foaming agent, was subjected to peeling and adhesive processing in the same manner as in Example 1, and the peel strength was measured (Comparative Example 3-1.3- 2).

The results are shown in Table 4. When the same liquid composition was applied as a foam, better releasability was obtained with a smaller amount of coating.

However, when a foaming agent is used to foam (Comparative Example 3)
-2) The surfactant action of the foaming agent destroys the size properties imparted by the internal addition system, increasing penetration into the paper. As a result, not only the amount of coating increased, but also the air permeability did not increase and peeling became difficult.

Example 4 Enzyme-modified starch used in Example 3 10% (solid content 4
0.5% (solid content concentration) of carboxymethyl cellulose (trade name: Sunrose F-50MC, manufactured by Yamaba Kokusaku Pulp Division) and acrylic resin (trade name: Sunsizer 5A501) as a foaming agent and sizing agent.

Made by Sanyo Chemical Industries, Ltd.] A coating solution containing 1% (solid content concentration) was foamed 15 times as much as in Example 1, coated on the same high-quality paper as in Example 1, and subjected to peeling and adhesive processing. The peel strength was evaluated.

Comparative Example 4 A liquid having the same composition as in Example 4 was applied using a size press, and the peel strength was measured in the same manner.

The results are shown in Table 4. Example 4 is Example 2 or Example 3
Although the air permeability is lower and the peeling tends to be somewhat heavier than that of foam-coated products, similar to the previous results, the results were better with foam-coated products.

Example 5 Pulp blend N-BKP 40%, L-[3KP 60%
Oxidized starch [trade name: Varnishizer 700° Flavor] was added to a Fourdrinier machine-made high-quality paper with a basis weight of 60 g/m obtained in the same manner as in Example 1 using raw material pulp with a beating degree of 450 mfA csf. Made by 18■ 7% (solid content concentration), polyvinyl alcohol [Product name: Kuraray Bhopal KL-3
18. ■Manufactured by Kuraray] 5% (solid content concentration), carboxymethyl cellulose [Product name: Sunrose F-50MC,
Chongyo national policy pulp n! A coating liquid consisting of 30.3% (solid content concentration) was heated to a foaming ratio of 1 using the same foaming machine as in Example 1.
The foam was foamed five times, size press coating was performed, and drying was performed using a multi-barrel dryer. After that, the moisture in the paper is 10%
Then, supercalendering was carried out to obtain a base paper for direct coating. This base paper was subjected to peeling and adhesive processing in the same manner as in Example 1, and its peel strength was measured. In addition, in order to evaluate the dimensional stability, the underwater elongation (J,
TAPPI 1 Paper Pulp Test Method Nα27'') and hygroscopic elongation were measured when the relative humidity was increased from 40% to 90%.

Comparative Example 5 60 g/m base paper with the same pulp composition as Example 5 (Comparative Example 5-1) and pulp blend N-BKP 40%.

A coating solution having the same composition as in Example 5 was size press coated in a liquid state on a 60 g/m base paper (Comparative Example 5-2) having a raw pulp composition of L-BKP 60% and a freeness of 280 mucsf, and Example 5 A base paper for direct coating was obtained through the same process.

This base paper was subjected to peeling and adhesive processing, and its peel strength was measured and the dimensional stability of the base paper for direct coating was evaluated.

The results are shown in Table 5.

By increasing the beating degree of the raw material pulp, the elongation in water and the elongation after moisture absorption were reduced, and the dimensional stability was improved. However, as seen in Comparative Example 5-2, size press coating of the liquid not only increases the amount of coating but also lowers air permeability, extremely high peel strength, and deteriorates releasability. On the other hand, by foam coating as in Example 5, the air permeability and releasability are comparable to those of the liquid coated product with a low degree of beating in Comparative Example 5-2. In other words, this example shows that by combining increasing the C5F of the raw material pulp with foam coating, it is possible to produce a release paper base paper for direct coating that has both good dimensional stability and good releasability. It is something.

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Claims (1)

[Scope of Claims] 1. Base paper with a basis weight of 40 g/m^2 or more made of wood pulp with a beating degree of 200 mlcsF or more [a] polyvinyl alcohol, styrene/maleic acid copolymer, diisobutylene/maleic acid copolymer , a single system using one or more foaming agents made of acrylic resin, or a combined system using one or more foam stabilizers consisting of starch, starch derivatives, or cellulose derivatives. Air permeability after superfoaming a foaming liquid composition containing a polymer with a surface tension of 60 dyn/cm or less to a foaming ratio of 5 times or more, applying it at the dry end of a paper machine, and applying dry calendering. 3,000 seconds or more.