JP3055867B2 - Renewable water and oil resistant paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper sheet and a food packaging container and the like which are required to have both water resistance and oil resistance at the same time, and a method for producing the same. No product blocking occurs,
The present invention relates to a water- and oil-resistant paper that is easily disintegrated and can be recovered and reused.

[0002]

2. Description of the Related Art Laminated paper such as polyethylene and film-bonded paper are known as papers having high water resistance and oil resistance. However, since they are composite materials with plastic, they have no disintegration properties and are difficult to recover as recycled materials. There are drawbacks. Therefore, in response to recent environmental problems, a water- and oil-resistant paper has emerged in place of a polyethylene laminated paper coated with an aqueous emulsion that is defibrating and easy to recover resources.

However, such resin-treated paper tends to cause blocking (a phenomenon in which the paper sticks to each other when the product is left standing or transported in a wound state or in a state where plain paper is deposited), and anhydrous silica or starch powder is used. Although a so-called anti-blocking agent is sprayed between the papers to prevent it, an improper amount of spraying may cause trouble in the printing process.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a resin-treated paper which does not cause blocking even if the application of an anti-blocking agent, which can be a trouble factor in a printing process, is omitted in the resin-treated paper as described above. It is still another object of the present invention to provide a water- and oil-resistant paper from which resources can be easily recovered in response to environmental problems.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have applied an acrylic resin emulsion to a base paper having controlled surface irregularities and liquid absorption. By setting the glass transition temperature (T _g ) of the acrylic resin in an appropriate range in a water- and oil-resistant paper obtained by heating and drying, a uniform film having excellent blocking resistance while maintaining water resistance and oil resistance can be obtained. The obtained film was further found to be easy to separate and disperse at the time of defibration and could be used as a recycled material, and the present invention was completed.

[0006] The base paper in the present invention is mainly composed of natural fibers for papermaking, and can be obtained by a method known to those skilled in the art. maximum height of JIS B 0601 (R _max)
JIS P 8140 in the range of 30 to 5 μm and liquid absorbency
Characterized in that it has a Cobb water absorption of 50 to 20 g / m ² · 2 minutes.

When the surface roughness R _max of the base paper exceeds 30 μm, the size of the surface irregularities becomes larger than the thickness of the coating film, so that the film on the convex portion becomes extremely thin, and the function deterioration in this portion is large, Further, in order to reduce the surface roughness R _max of the base paper to less than 5 μm, it is necessary to excessively lower the raw material CSF, press and strengthen the calendering treatment, and as a result, the paper is crushed and dense, and the liquid absorption as described later In addition to the decrease in paper stiffness, the rigidity of the paper decreases, making it unsuitable for trays and containers.

[0008] Liquid-absorbent base paper surface exceeds 50g / m ² · ² minutes as Cobb water absorption many coating liquid penetration into the paper layer, pinholes no uniform coating on the base paper surface is formed , And sufficient performance cannot be obtained. To compensate for this, an excessive amount of coating is required, increasing the drying load, etc.
It is costly and economically disadvantageous. On the other hand, if the Cobb water absorption is less than 20 g / m ² · 2 minutes, the penetration of the emulsion into the base paper is small, and the bonding between the coating film and the base paper, the so-called anchor effect, is weakened. The problem of peeling off from paper arises.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A base paper satisfying such conditions can be obtained by a usual paper making process. For example, surface roughness can be controlled by adjusting raw material CSF and wet press pressure, using a Yankee dryer, and using pigments. Liquid absorption can be controlled by precoating, calendering, or the like, and by internal addition of an acidic sizing agent or a neutral sizing agent, surface size coating by a size press, or the like.

The acrylic resin emulsion that can be used in the present invention is, for example, an acrylic polymer, an acrylic resin emulsion.
Various emulsions such as copolymer emulsions such as styrene copolymers and self-crosslinking acrylic copolymer emulsions can be used. Specifically, styrene and styrene derivatives, acrylic acid (methacrylic acid) and methyl acrylate, An acrylic copolymer obtained by copolymerizing acrylates such as ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate, and methacrylates such as methyl methacrylate, ethyl methacrylate and butyl methacrylate. Acrylic resins having a glass transition temperature (T _g ) in the range of 10 to 28 ° C. are preferred.

If the acrylic resin has a _Tg of 10 ° C. or less, the film is flexible, and if the papers are left standing one on top of the other, the adhesion increases and blocking tends to occur. On the other hand, if the _Tg is 28 ° C. or higher, the film-forming properties are poor, and furthermore, the film is brittle, cracks are likely to occur at the time of bending, and the water resistance and oil resistance deteriorate, which is not preferable.

The resin emulsion can be applied to paper using any of the on-machine or off-machine coating apparatuses such as a roll coater, a bar coater, a blade coater, an air knife coater, and a curtain coater. However, as described above, an air knife coater is suitable for obtaining a uniform film. The coating amount after drying is preferably in the range of 3 to ²⁰ g / m ² . Coating amount is 3g / m
^If it is less than ² , continuous and uniform film formation will be insufficient, and the performance such as water resistance will not be sufficiently exhibited, and if it is more than 20 g / m ^{2, the} performance will not change and the cost will be increased and disadvantageous. The drying temperature is not particularly limited, but generally, drying at 70 to 150 ° C is sufficient.

[0013]

EXAMPLES Hereinafter, the water- and oil-resistant paper according to the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The indications “%” and “parts” represent “% by weight” and “parts by weight”, respectively. The tests and evaluation methods used in the examples are as follows.

(1) Surface roughness JIS B 0601 (1976) Maximum height in surface roughness ( _Rmax )
Was measured.

(2) Water Absorption In accordance with JIS P 8140 (1976) paper and paperboard water absorption test method (Cobb method), the water absorption of the base paper surface after 2 minutes was measured.

(3) Water resistance According to JIS P 8140 (1976) paper and paperboard water absorption test method (Cobb method), the water absorption of the resin-coated surface after 60 minutes was measured.

(4) Oil resistance Test liquids shown in Table 1 were prepared based on TAPPI UM-557 and evaluated.

[0018]

[Table 1]

(5) Blocking Resistance Five sheets of paper cut into 10 cm squares were stacked and left under pressure at room temperature for 2 hours under a load of 4 kgf / cm ² to evaluate the adhesion between the resin surface and the non-resin surface.

(6) Disintegration (recovery of recovered paper) Using a standard disintegrator (Tappi standard disintegrator; 3000 rpm) shown in JIS P 8209 (1976) Hand paper preparation method for pulp test, at room temperature A piece of paper having a size of 1 to 2 cm square was added to tap water to give a pulp concentration of 2%, and defibration was performed for 15 minutes. In the evaluation method, the state of the slurry after the defibration and the fiber state after the preparation of the handsheet were visually determined.

Example 1 One side (surface roughness R _max 15.3 μm, Cobb water absorption 36 g / m ² · 2 min) of a double-sided lightly coated paperboard (basic weight 320 g / m ² ) (acid sizing agent to pulp 0.5% internally added) ) Was coated with an acrylic resin emulsion having a T _{g of} 26 ° C (Sibinol EK-55, manufactured by Seiden Chemical Co., Ltd.) using an air knife coater.
It was dried with hot air at 30 ° C. The water- and oil-resistant paper thus obtained had a resin coating amount of 10.0 g / m ² after drying.

Example 2 An acrylic resin emulsion having a T _{g of} 15 ° C. (manufactured by Seiden Chemical Co., Ltd .; Sibinol X-595-9) was used.
05E-2), and applied and dried with hot air in the same manner as in Example 1. The coating amount at this time was 8.0 g / m ² after drying.

[0023] manufactured by Comparative Example 1 Resin coating liquid T _g 5 ° C. in an acrylic resin emulsion (Saiden Chemical Co., Saivinol X-595-9
Coating was carried out in the same manner as in Example 1 except that it was 03E-1), followed by hot-air drying. The coating amount at this time was 13.4 g / m ² after drying.

Comparative Example 2 An acrylic resin emulsion having a T _{g of} 30 ° C. (manufactured by Seiden Chemical Co., Ltd .; Sibinol X-595-9) was applied to the resin coating solution.
Using 05E-6), the same paperboard as in Example 1 was coated with a Meyer bar # 16 and dried with hot air at 130 ° C for 30 seconds. The coating amount at this time was 14.0 g / m ² after drying.

Comparative Example 3 Uncoated paperboard having a basis weight of 320 g / m ² (no sizing agent added,
Surface roughness R _max 27.8μm, Cobb water absorption 78g / m ² · ²
Min), the same aqueous emulsion as in Example 2 was applied using a Meyer bar # 14 and dried with hot air at 130 ° C. for 30 seconds. The coating amount at this time was 8.5 g / m ² after drying.

Comparative Example 4 Example ² was applied to uncoated paperboard having a basis weight of 320 g / m ² (acid sizing agent to pulp 0.3% internally added, surface roughness R _max 36.5 μm, Cobb water absorption 29 g / m ² · 2 minutes). The same aqueous emulsion was applied using a Meyer Par # 14 and dried with hot air at 130 ° C for 30 seconds. The resin coating amount at this time was 8.7 g / m ² after drying.

Table 2 shows the results of evaluating the blocking resistance, oil resistance, water resistance, and defibration properties of the papers obtained in the above Examples and Comparative Examples.

[0028]

[Table 2]

As can be seen from the results, the surface roughness R _max
30 to 5 μm, and liquid absorbency as 50 to 20 g /
T _g 10 to 28 in base paper was controlled to a range of m ² · 2 minutes
In Examples 1 and 2 of the present invention in which an acrylic resin emulsion having a temperature in the range of ° C was applied, water resistance and oil resistance were good, and blocking resistance was also good. On the other hand, if the T _g of the acrylic resin in the same base paper is low (Comparative Example 1) it is water-resistant formed well flexible coating film formability, oil resistance occurs good although blocking. When _Tg is high (Comparative Example 2), the film-forming properties are poor and the film is brittle, so that blocking does not occur, but the function is greatly reduced by bending. In addition, even if the resin has good blocking resistance, if the liquid absorbency of the base paper is large (Comparative Example 3), or if the surface of the base paper is rough (Comparative Example 4), a uniform resin film is formed as described above. Is not formed, and satisfactory performance cannot be obtained.

[0030]

The water- and oil-resistant paper according to the present invention is a resin-treated paper having a quality close to that of polyethylene laminated paper,
Because it has good blocking resistance without dispersing an anti-blocking agent such as conventional resin-coated paper, and has good disintegration properties and can be recovered and reused, its industrial significance as an environmentally-friendly packaging material is Very large.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Sadao Hosokawa 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Nihon Paper Industries Co., Ltd. (72) Inventor Yasunori Minamisato 1-30, Kamiochiai, Shinjuku-ku, Tokyo No. 6 Nippon Paper Industries Co., Ltd. Product Development Laboratory (72) Inventor Tadashi Iwamida 450 Hina, Fuji City, Shizuoka Prefecture Inside Koyo Paper Co., Ltd. (56) References JP-A-6-57689 (JP, A) 7-258307 (JP, A) 7-26493 (JP, U) JP44-5326 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) D21H 19 / 00-27/42

Claims (2)

(57) [Claims] The surface roughness (JIS B 0601) is the maximum height (R
_max ) and 30 to 5 μm and Cobb water absorption (JIS P 8140)
Has a glass transition temperature (T _g ) on one or both sides of a base paper mainly composed of natural fibers for papermaking having a particle size of 50 to 20 g / m ² · 2 min.
A water- and oil-resistant paper which has good blocking resistance and is renewable, obtained by applying an acrylic resin emulsion coating liquid having a solid content of 3 to 20 g / m ² at 10 to 28 ° C and drying by heating. 2. A method for producing a renewable water- and oil-resistant paper having good blocking resistance according to claim 1.