JP2005009017A - Waterproof and oilproof paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide waterproof and oilproof paper having both water resistance and oil resistance needed as waterproof and oilproof paper while reducing plastic use, and realizing hot-meltability and disaggregativeness. <P>SOLUTION: The waterproof and oilproof paper comprises a paper base 1 adjusted in surface roughness or Cobb test water-absorbency so as to be uniformly coatable with an aqueous emulsion and a coating layer 2 formed on the paper base 1 by coating it with the polyester-based aqueous emulsion followed by drying. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water- and oil-resistant paper that is required to have both water resistance and oil resistance at the same time in a paper tray, a food packaging container, and the like. .
[0002]
[Prior art]
Conventionally, laminated paper such as polyethylene and film-laminated paper are known as water- and oil-resistant paper having high water resistance and oil resistance. However, since this type of water- and oil-resistant paper is a composite material with plastic, there is no disaggregation (recovered paper recoverability). That is, contrary to the recent increase in demand for environmental problems, it is a water and oil resistant paper that is difficult to recover resources.
[0003]
For this reason, recently, there has been a demand for water-resistant and oil-resistant paper that allows easy resource recovery, or at least water- and oil-resistant paper that reduces the amount of plastic used.
[0004]
Here, as a water- and oil-resistant paper that does not use plastic, a recyclable processed paper is disclosed in which an acrylic emulsion is applied several times to the paper surface and an acrylic resin layer is laminated (for example, patent document) 1).
[0005]
[Patent Document 1]
JP-A-6-57689
[Problems to be solved by the invention]
However, the processed paper coated with an acrylic emulsion has a large deterioration at the ruled line portion, so the coating amount must be increased.
[0007]
As a result, although the water- and oil-resistant paper can be disaggregated, the acrylic resin cannot actually be pulverized even by a stirring mixer, and the granular acrylic resin remains, so that it is difficult to process it into a re-paper.
[0008]
The present invention has been made in consideration of the above circumstances, and has the water resistance and oil resistance necessary for water and oil resistant paper while reducing the amount of plastic used, and further achieves hot melt suitability and disaggregation. The object is to provide a water and oil resistant paper to be obtained.
[0009]
[Means for Solving the Problems]
1st invention is provided with the following A paper base material and the following B coating layer formed in the single side | surface or both surfaces of the said A paper base material, Cobb water absorption (JIS P8140) is 15 [g / m < ² >. 2 minutes] or less, and is a water and oil resistant paper having hot melt suitability and easy disintegration.
[0010]
A: A paper base having a surface roughness (JIS B01001) in the range of 30 to 5 μm in terms of the maximum height (R _max ).
B: A coating layer formed by applying and drying a polyester-based aqueous emulsion having a glass transition temperature Tg in the range of 10 to 30 ° C. within a range of 2 to 20 [g / m ² ] in terms of solid content.
[0011]
A second invention is a water- and oil-resistant paper having the following A paper base material in place of the A paper base material in the first invention.
A: A paper base having a Cobb water absorption (JIS P8140) in the range of the basis weight of paper to 20 [g / m ² · 2 min].
[0012]
As described above, the polyester-based aqueous emulsion is applied and dried on a paper base whose surface roughness or Cobb water absorption is adjusted so that the aqueous emulsion can be uniformly applied, while reducing the amount of plastic used. It has water resistance and oil resistance necessary for water and oil resistant paper, and can achieve hot melt suitability and disaggregation.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0014]
FIG. 1 is a cross-sectional view schematically showing a configuration of a water- and oil-resistant paper according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view schematically showing a modified configuration of the water- and oil-resistant paper.
[0015]
This water and oil resistant paper 10 includes a paper base 1 and a coating layer 2 formed on one or both sides of the paper base 1 and can be used for applications such as paper trays and food paper container materials. It has become. Specifically, the water- and oil-resistant paper 10 is water resistant and has hot melt suitability that the Cobb water absorption (JIS P8140) is 15 [g / m ² · 2 min] or less from the viewpoint of use as a material for food paper containers. And easy disaggregation.
[0016]
Here, the paper substrate 1 is one in which the surface roughness (R _max ) and Cobb water absorption (liquid absorbency) before application of the aqueous emulsion to be the coating layer 2 are adjusted within a predetermined range. It can be made by a known method mainly using natural fibers for papermaking.
[0017]
Specifically, the surface roughness of the paper substrate 1 is in the range of 30 to 5 μm at the maximum height (Rmax) specified in JIS B010001. The water absorption of the paper substrate 1 is such that the Cobb water absorption (JIS P8140) is within the range of 20 [g / m ² · 2 minutes] or less to the basis of the weight of the paper. The paper substrate 1 only needs to satisfy at least one of the surface roughness and the Cobb water absorption.
[0018]
When the surface roughness (R _max ) of the paper substrate 1 exceeds 30 μm, the size of the surface irregularities becomes larger than the thickness of the coating film, so that the coating film at the convex portion becomes extremely thin and the function is deteriorated. Becomes larger.
[0019]
Further, in order to reduce the surface roughness (R _max ) of the paper base material 1 to less than 5 μm, excessive press, strengthening of the calendar process, and the like are required. Therefore, the paper base material 1 is crushed and becomes fine. Since it is thin and the rigidity is lowered, it is not suitable for a tray or a container.
[0020]
In addition, when the Cobb water absorption of the paper base material 1 is higher than the weighed amount of paper, the coating liquid penetrates in a large amount and the coating film on the surface becomes non-uniform. Become. To compensate for this, an excessive coating amount is required.
[0021]
Here, the case of the paper having such a high Cobb water absorption will be described in detail. This is the case, for example, when the paper substrate 1 is inexpensive. In general, inexpensive paper has a high water absorption (liquid absorbency) due to its low surface water resistance. Therefore, inexpensive paper requires a large amount of resin coating in order to obtain high water resistance and high oil resistance, but may be used in consideration of the following advantages.
[0022]
In general, inexpensive paper is paper using waste paper (hereinafter referred to as recycled paper). With the recent increase in the used paper usage rate, the usage rate for packaging materials such as 100% used paper is increasing. Waste paper is inexpensive and is cut to a short fiber length during the recycling process. For this reason, recycled paper using used paper has the advantage that it does not return easily when folded (high dead hold property).
[0023]
The advantage that the dead hold property is high means that it is excellent in the performance of holding the folded shape when folded and assembled into a box. Because of this advantage, recycled paper has the disadvantage of requiring a lot of resin, but it is a powerful choice depending on the price of the paper base 1, the price of the resin, and the characteristics of the paper base 1 when designing the product. It has become.
[0024]
On the other hand, when the Cobb water absorption of the paper base material 1 is less than 20 [g / m ² · 2 minutes], there is little penetration of the emulsion into the paper base material 1 and the bonding between the coating layer 2 and the paper base material 1 The so-called anchor effect is weakened, and the coating layer 2 is easily peeled off from the paper substrate 1 during bending. Therefore, the water absorption of the paper substrate 1 is desirably 20 [g / m ² · 2 minutes] or more.
[0025]
The paper base 1 as described above is obtained by a normal papermaking process. For example, the adjustment of the surface roughness of the paper substrate 1 can be performed by controlling the raw material beating degree (CSF) and wet press pressure, using a Yankee dryer, pigment pre-coating, calendaring, and the like. In addition, the adjustment of the Cobb water absorption of the paper substrate 1 can be performed by internal addition of an acidic sizing agent or neutral sizing agent, surface size coating by a size press, or the like.
[0026]
On the other hand, the coating layer 2 is obtained by applying and drying a polyester-based aqueous emulsion having a glass transition temperature Tg of 10 ° C. or more and 30 ° C. or less within a range of 2 to 20 [g / m ² ] in terms of solid content. It will be.
[0027]
For coating polyester-based aqueous emulsion, any coating equipment such as rod bar coater, gravure coater, roll coater, bar coater, blade coater, air knife coater, curtain coater used on-machine or off-machine can be used. is there.
[0028]
The application amount of the polyester-based aqueous emulsion is preferably in the range of ^{2 to} 20 [g / m ² · dry] after drying. When the coating amount is less than 2 [g / m ² ], the formation of a continuous uniform coating film becomes insufficient, and the performance such as water resistance becomes insufficient. On the other hand, when the coating amount is more than 20 [g / m ² ], it is difficult to dry, so that the production becomes difficult. The specific value of the coating amount is 2-20 within the scope of ^{[g / m 2 · dry]} , state or paper substrate 1 may be such set according to the required performance of the water-oil-paper 10 .
[0029]
The drying temperature of the polyester-based aqueous emulsion is not particularly limited, but it is sufficient if it is within the range of 70 to 150 ° C. from the viewpoint of removing moisture and aggregating and melting the emulsion particles.
[0030]
The water / oil resistant paper 10 as described above is formed on a paper tray 20 as shown in FIG. 3, for example, by forming a ruled line, folding it at the ruled line part, and adhering appropriately. However, it goes without saying that the water and oil resistant paper 10 is not limited to food containers such as the paper tray 20 and may be applied to any application as long as the water and oil resistance is required.
[0031]
Next, the operation of the water-resistant paper configured as described above will be described.
First, a paper substrate 1 is prepared in which either one or both of the surface roughness and the Cobb water absorption is adjusted within a predetermined range. The predetermined range of the surface roughness, as described above, a 30~5μm in maximum height _{(R max).} Similarly, the predetermined range of the Cobb water absorption is, as described above, not more than the weight of the paper to 20 [g / m ² · 2 minutes].
[0032]
A polyester-based aqueous emulsion to be the coating layer 2 is applied on the paper substrate 1 by a coating device within a range of ^{2 to} 20 [g / m ² ] in terms of solid content, and applied to the surface of the paper substrate 1. A film was formed.
[0033]
The paper base material 1 on which the coating film was formed was transported from the coating apparatus to the drying furnace, heated and dried in the drying furnace, and carried out. Thereby, the water-resistant oil-resistant paper 10 which has the coating layer 2 on the paper base material 1 was manufactured.
[0034]
Since this water- and oil-resistant paper 10 has a coating layer 2 with a Cobb water absorption of 15 [g / m ² ] or less, it can prevent the penetration of liquids such as water and oil, and can exhibit water resistance and oil resistance. it can.
[0035]
Thereafter, a ruled line was formed on the water-resistant and oil-resistant paper 10, folded at the ruled line portion, and appropriately bonded to produce a paper tray 20.
[0036]
Since the paper tray 20 is made of the water-resistant and oil-resistant paper 10 described above, similarly, the penetration of liquids such as water and oil can be prevented, and water resistance and oil resistance can be expressed.
[0037]
As described above, according to the present embodiment, the coating layer 2 obtained by applying and drying the polyester-based aqueous emulsion on the paper base material 1 whose surface roughness or Cobb water absorption is adjusted so that the aqueous emulsion can be uniformly applied, While reducing the amount of plastic used, it has the water resistance and oil resistance necessary for water- and oil-resistant paper, and can achieve hot melt suitability and disaggregation.
[0038]
Specifically, the paper base material 1 with the surface irregularity and liquid absorbency adjusted is coated with a polyester emulsion having a glass transition temperature Tg in the range of 30 ° C. to 100 ° C. A uniform coating layer 2 excellent in oil resistance and hot melt suitability can be obtained. Furthermore, this coating layer 2 can be easily separated and dispersed at the time of disaggregation and can be used as a recycled material.
[0039]
The water and oil resistant paper 10 provided with such a coating layer 2 can obtain performance close to that of polyethylene laminated paper with respect to the oil resistance of the plane portion and the ruled line portion.
[0040]
Furthermore, since the coating layer 2 has hot melt suitability and is easily disintegrated, it can be easily reused as used paper with existing equipment. Moreover, when the paper base material 1 is recycled paper, the water / oil resistant paper 10 can be provided at a lower cost.
[0041]
Accordingly, the water and oil resistant paper 10 and the packaging container as described above have extremely great industrial significance as environment-conserving packaging materials that require a high degree of water and oil resistance.
[0042]
Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.
[0043]
【Example】
Hereinafter, although the embodiment described above will be described in detail by way of examples, the present invention is not limited to the embodiment described above and the following examples. In the following description, the indications “%” and “parts” represent “% by weight” and “parts by weight”, respectively.
[0044]
Moreover, the test and evaluation method used in each Example are as shown to following (1)-(7).
(1) Surface Roughness of Paper Base 1 The maximum height (Rmax) at the surface roughness specified in JIS B01001 (1976) was measured.
[0045]
(2) Cobb water absorbency of paper base material 1 According to JIS P8140 (1976) water absorption test method (Cobb method) of paper and paperboard, distilled water was brought into contact with the resin coated surface, and the water absorbency after 2 minutes was measured. .
[0046]
(3) Water resistance of water / oil resistant paper 10 JIS P8140 (1976) Water absorption after 60 minutes of resin coated surface by contacting distilled water with resin coated surface according to water absorption test method (Cobb method) of paper and paperboard Was measured.
[0047]
(4) Based on oil resistance [TAPPIUM-557], a test solution was prepared and evaluated as shown in FIG.
[0048]
(5) Blocking resistance Note that blocking refers to a phenomenon in which pseudo-adhesion or adhesion occurs at the interface of stacked substances and does not easily separate (do not peel off). Here, blocking resistance that hardly causes such blocking was examined.
In the evaluation method, the water / oil resistant paper 10 was processed into a plurality of test pieces of 10 cm × 10 cm. Next, each test piece is overlapped, and the first test bundle (one of the two sheets of the paper base and the coating layer 2) is overlapped with the second test bundle (of the two test pieces). A pair with two layers of the coating layer was created. Ten such sets are prepared for each example and each comparative example, and 10 sets are subjected to a blocking tester so as to have a weight of 1000 g / m ² , and left at 50 ° C. and 80% Rh for 24 hours. The peel resistance was evaluated.
[0049]
The evaluation results are indicated by a symbol “◯” as a pass indicating that the peel resistance is such that it can be peeled off without a feeling of peeling or feels a light peeling feeling. Moreover, the evaluation result was represented by the symbol x as a failure when the material had a strong peel resistance and the material that caused material destruction at the interface in addition to the strong peel resistance.
[0050]
(6) Hot melt (HM) adhesiveness The hot melt property of the water and oil resistant paper 10 sample is tested on a resin surface and a non-resin surface. For the test, a hot melt apparatus (trade name: Hakoko Melter 806-1 (manufactured by Hakuko Co., Ltd.)) was used. Two test pieces each having a shape of (width) 70 mm × (flow) 150 mm are prepared from the water / oil resistant paper 10 in pairs. In the following description, each of the set of two test pieces is referred to as a first test piece and a second test piece.
[0051]
Thereafter, the hot melt is melted and kept at 180 ° C. in a hot melt apparatus. In addition, the brand name: HC1601 (made by Nitta Gelatin) was used for the hot melt.
[0052]
Next, 0.1 g of hot melt is applied to the clay coat surface (one surface of the paper substrate) of the first test piece, and left for 2 seconds (open time) from application to adhesion.
Then, the resin-coated surface (two coated layers) of the second test piece is placed on and adhered to the clay-coated surface (coated surface) of the first test piece, and a weight (weight) of 330 g is applied for 2 seconds (set time). ) Next, the weight was removed, and the first and second test pieces were stored in an environmental test room, and a peel test was performed after 24 hours. That is, after leaving in an environment of freezing, refrigeration at 5 ° C., temperature 25 ° C. and humidity 60%, temperature 40 ° C. and humidity 90%, it was peeled off and passed with paper peeling.
[0053]
(7) Disaggregation (recoverable paper recovery)
JIS P8209 (1976) Standard disintegrator described in the method for preparing handmade paper for pulp test (Tapi standard disintegrator; 3000 rpm) is used. The amount was added and disaggregated for 15 minutes. In the evaluation method, the slurry after disaggregation and the fiber state after preparation of the handsheet were visually determined. The resin and the fiber separated cleanly, and when the paper was re-made, the fiber was rejected (granular mass), and it was accepted.
[0054]
<Example 1>
As the paper substrate 1 of Example 1, a card paper having a basis weight of 260 g was used. This card paper has a maximum surface roughness (R _max ) of 13.2 μm and a Cobb water absorption of 40 [g / m ² · 2 min].
[0055]
A resin emulsion of a polyester-based oilproofing agent having a glass transition temperature Tg of 28 ° C. was applied to the card paper with an air knife so that the coating amount was 6 [g / m ² · dry] and dried. The drying condition was a paper surface temperature: 80 ° C. (measured value).
[0056]
<Example 2>
In Example 2, a card paper having a Cobb water absorption of 220 [g / m ² · 2 min] in the card paper of Example 1 was used.
[0057]
The Cobb water absorption can be adjusted by finely applying PVA (polyvinyl alcohol) or the like to the substrate during paper making. A large Cobb water absorption indicates that the water resistance is poor, and the aqueous emulsion is likely to penetrate.
[0058]
The card paper of Example 2 was coated with a polyester oil-resistant resin emulsion having a glass transition temperature Tg of 15 ° C. with an air knife so that the application amount was 15 [g / m ² · dry] and dried. The drying conditions are the same as in Example 1.
[0059]
<Comparative Example 1>
As the paper base material of Comparative Example 1, card paper having the same characteristics as Example 1 was used.
[0060]
The same resin emulsion as in Example 1 was applied to an application amount of 1.5 [g / m ² · dry] with an air knife and dried. The drying conditions are the same as in Example 1.
[0061]
<Comparative example 2>
As the paper base material of Comparative Example 2, card paper having the same characteristics as Example 1 was used.
[0062]
A resin emulsion of a polyester-based oilproofing agent having a glass transition temperature Tg of 5 ° C. was applied with an air knife to a coating amount of 2 [g / m ² · dry] and dried. The drying conditions are the same as in Example 1.
[0063]
<Comparative Example 3>
The paper base of Comparative Example 3 was a card paper having the same characteristics as Example 1.
[0064]
A resin emulsion of a polyester-based oilproofing agent having a glass transition temperature Tg of 30 ° C. was applied with an air knife so that the coating amount was 2 [g / m ² · dry] and dried. The drying conditions are the same as in Example 1.
[0065]
<Comparative example 4>
As the paper base material of Comparative Example 4, the card paper having the Cobb water absorption of 265 [g / m ² · 2 min] in the card paper of Example 1 was used.
[0066]
To this, the resin emulsion of Example 1 was applied with an air knife so that the coating amount was 2 [g / m ² · dry], and dried. The drying conditions are the same as in Example 1.
[0067]
<Comparative Example 5>
The paper base material of Comparative Example 5 was a strong paper having the same basis weight and R _max as in Example 1 and a Cobb water absorption of 40 [g / m ² · 2 min].
[0068]
To this, the resin emulsion of Example 1 was applied with an air knife so that the coating amount was 2 [g / m ² · dry], and dried. The drying conditions are the same as in Example 1.
[0069]
<Comparative Example 6>
The paper base material of Comparative Example 6 is the card paper of the card paper of Example 1, with the maximum surface roughness height (R _max ) being 30 μm and the Cobb water absorption being 220 [g / m ² · 2 min]. It was used.
[0070]
The resin emulsion of Example 2 was used for this, and it was coated with an air knife so that the coating amount was 15 [g / m ² · dry] and dried. The drying conditions are the same as in Example 1.
[0071]
<Comparative Example 7>
In Comparative Example 7, an acrylic resin emulsion (EK61: manufactured by Seiden Chemical; Tg 25 ° C.) was used instead of the polyester resin in Example 1, and the coating amount was 2 [g / m ² · dry]. , Dried. Other conditions are the same as those in the first embodiment.
[0072]
<Comparative Example 8>
As the paper base material of Comparative Example 8, card paper having the same characteristics as Example 4 was used.
[0073]
A low-density polyethylene resin having a thickness of 15 μm was laminated on the back surface of the card paper.
[0074]
The results of evaluating the oil resistance, hot melt property, disaggregation property and the like of the papers obtained in Examples 1 and 2 and Comparative Examples 1 to 8 are shown in FIG.
Examples 1 and 2 have high oil resistance at the flat portion, little deterioration in bending performance, water and oil resistance close to that of polyethylene laminated paper (Comparative Example 8), hot melt suitability, and good disaggregation. there were. In Examples 1 and 2, the surface roughness (R _max ) is adjusted to 30 to 5 μm, and the Cobb water absorption is adjusted to be less than the basis weight to 20 [g / m ² · 2 minutes]. It is thought that the uniform coating layer 2 is created. The basis for the uniform coating layer 2 is that the water absorption after 60 minutes of the water-resistant and oil-resistant paper is substantially unchanged from the water absorption of 2 minutes.
[0075]
On the other hand, Comparative Examples 1 to 8 have a surface roughness (R _max ) in the range of 30 to 5 μm, as in the examples. In Comparative Examples 1 to 3 and 6 to 8, the Cobb water absorption is in the range of less than or equal to the basis weight to 20 [g / m ² · 2 minutes], as in each example.
[0076]
However, in Comparative Example 1, since the coating amount of the resin emulsion was less than 2 [g / m ² ], the coating layer was uneven and the water resistance was low.
[0077]
Since Comparative Example 2 had a low glass transition temperature Tg, the blocking resistance was low.
In Comparative Example 3, since the glass transition temperature Tg was high, the deterioration during bending was large.
In Comparative Example 4, the water resistance of the paper base material was low, and the water resistance was low.
[0078]
In Comparative Example 5, since the Cobb water absorption of the paper base material was small, peeling occurred because the adhesion between the coating layer and the paper base material was poor at the time of folding, and the deterioration of the folding performance was large.
In Comparative Example 6, since the paper substrate had a large surface roughness, the water resistance was low.
[0079]
In Comparative Example 7, since the resin to be applied was an acrylic resin, even when the physical property value (Tg) was the same, the bending performance was severely deteriorated.
Since Comparative Example 8 was a polyethylene laminated paper of the prior art, it had no disaggregation property.
[0080]
【The invention's effect】
As described above, according to the present invention, the water- and oil-resistant paper has the water resistance and oil resistance necessary as a water- and oil-resistant paper while reducing the amount of plastic used, and can realize hot melt suitability and disaggregation. Can provide.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a configuration of a water- and oil-resistant paper according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view schematically showing a modified configuration of the water and oil resistant paper in the same embodiment.
FIG. 3 is a schematic diagram showing a schematic configuration of a paper tray in the same embodiment.
FIG. 4 is a diagram for explaining a test solution for an oil resistance test of each example according to the present invention.
FIG. 5 is a diagram for explaining each example in comparison with each comparative example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Paper base material, 2 ... Coating layer, 10 ... Water-resistant paper, 20 ... Paper tray.

Claims (3)

It comprises the following A paper base and the following B coating layer formed on one or both sides of the A paper base, and has a Cobb water absorption (JIS P8140) of 15 [g / m ² · 2 min] or less. A water- and oil-resistant paper characterized by having hot melt suitability and easy disaggregation.
A: A paper base having a surface roughness (JIS B01001) in the range of 30 to 5 μm in terms of the maximum height (R _max ).
B: A coating layer formed by applying and drying a polyester-based aqueous emulsion having a glass transition temperature Tg in the range of 10 to 30 ° C. within a range of 2 to 20 [g / m ² ] in terms of solid content. The water and oil resistant paper according to claim 1,
The paper A base material has a Cobb water absorbency (JIS P8140) in the range of the basis weight of the paper to 20 [g / m ² · 2 min]. The water and oil resistant paper according to claim 1,
A water- and oil-resistant paper comprising the following A paper base instead of the A paper base. A: A paper base having a Cobb water absorption (JIS P8140) in the range of the basis weight of paper to 20 [g / m ² · 2 min].

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