Stock material or miscellaneous articles – Composite – Of wax or waxy material
Reexamination Certificate
2001-05-24
2002-09-24
Michl, Paul R. (Department: 1714)
Stock material or miscellaneous articles
Composite
Of wax or waxy material
Reexamination Certificate
active
06455168
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hot melt composition excellent in moistureproof properties, and recyclable moistureproof (laminated) paper using the same, which is excellent in disintegrating properties and moistureproof properties.
BACKGROUND OF THE INVENTION
As moistureproof paper used as packaging paper for newsprint base paper and copying paper, paper coated with polyolefin polymers such as polyethylene and polypropylene have been widely used. The moistureproof paper coated with the polyolefin polymers have the advantages of excellent workability and moistureproof properties and low cost. However, when it is tried to recycle these paper to reuse them, the coating strength of moistureproof layers is too strong to sufficiently disintegrate the paper with a disintegrator in a pulping process. As a result, the olefinic resin layers separated from the paper remain in the pulp as films, which make it impossible to recycle used paper.
In recent years, as recyclable moistureproof paper, moistureproof paper have been proposed which are coated with emulsions comprising synthetic rubber latexes and wax emulsions, or synthetic rubber latexes, wax emulsions and resin emulsions. These moistureproof paper have good moistureproof properties, and also have recyclability. However, they have the disadvantage that a long and large drying apparatus is required and it causes poor productivity, because coating solutions are emulsions.
Further, recently, moistureproof paper coated with a moistureproof hot melt composition mainly composed of an amorphous poly-&agr;-olefin (hereinafter abbreviated as APAO), a tackifier resin and wax has been proposed (Japanese Patent Laid-open Publication (Hei) 09-316252 and Japanese Patent Laid-open Publication (Hei) 11-158330). This moistureproof paper is excellent in moistureproof properties and disintegrating properties, and moreover has the advantage that it can be produced at low cost, because inexpensive APAO is used as a main component. However, the APAO used as a main component is amorphous and soft, so that the coated moistureproof paper is liable to show tackiness. Inhibition of the tackiness tends to bring cracks on a moistureproof layer when the paper is folded. It is therefore difficult to balance various properties. Further, the melt viscosity of the moistureproof hot melt composition is low, so that application thereof to T-die extrusion coating is difficult. Thus, there is a limitation on a coating method of the composition.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a hot melt composition excellent in moistureproof properties.
Another object of the present invention is to provide moistureproof paper using the same, which is excellent in moistureproof properties and recyclability, low in cost and excellent in productivity.
According to the present invention, there is provided
(1) a composition comprising 20% to 90% by weight of polyethylene and/or polypropylene (A) and 10% to 80% by weight of a tackifier resin (B), with the proviso that (A)+(B)=100% by weight (hereinafter also referred as to “composition (1)”);
(2) a composition comprising 20% to 90% by weight of the above-mentioned component (A), 5% to 80% by weight of the above-mentioned component (B) and 0.1% to 50% by weight of wax (C), with the proviso that (A)+(B)+(C)=100% by weight (hereinafter also referred as to “composition (2)”);
(3) a composition comprising 10% to 90% by weight of an ethylene-vinyl acetate copolymer (D) (hereinafter also referred to as “EVA”) and 10% to 90% of the above-mentioned component (B), with the proviso that (D)+(B)=100% by weight (hereinafter also referred as to “composition (3)”); or
(4) a composition comprising 10% to 90% by weight of the above-mentioned component (D), 5% to 90% by weight of the above-mentioned component (B) and 0.1% to 50% of the above-mentioned component (C), with the proviso that (D)+(B)+(C)=100% by weight (hereinafter also referred as to “composition (4)”).
DETAILED DESCRIPTION OF THE INVENTION
In the moistureproof hot melt composition of the present invention, polyethylene and/or polypropylene (A) or the EVA (D) is used as a base polymer, with which the tackifier resin (B) and/or the wax (C) is further mixed. Accordingly, when the moistureproof hot melt composition is used, the film strength of a moistureproof layer can be kept lower than that of the conventional moistureproof paper with which olefinic polymers are used. It is also possible to achieve disintegration of used paper with a disintegrator in a pulping process on recycling. These polymers (A) or (D) have appropriate hardness and softness, so that various properties required for the moistureproof hot melt composition can be easily balanced, and the MFR (Melt Flow Rate) of the moistureproof hot melt composition can be freely adjusted. Accordingly, the moistureproof hot melt composition of the present invention is applicable to various coaters.
The MFR will be described in detail below.
The MFR is generally used for indicating the fluidity of a resin.
The MFR value is determined by the following method. As to polyethylene or EVA, a material is put in a cylinder having an orifice with a diameter of 2.1 mm and a length of 8 mm, and the material melted is extruded at 190° C. (230° C. for polypropylene) under a load of 2,160 g. The weight of the material extruded for 5 to 240 seconds is measured, and then, converted to gram per 10 minutes, thereby obtaining the MFR value. That is to say, the higher MFR value means the better fluidity (see JIS-K-7210).
The most preferable MFR value of polyethylene and polypropylene (A) used in the present invention varies depending on the coating method of the moistureproof hot melt composition. For example, in T-die extrusion coating, the MFR is preferably from 0.1 to 200 g/10 minutes, more preferably from 0.1 to 50 g/10 minutes, and particularly preferably from 0.1 to 30 g/10 minutes. On the other hand, in coating with a head coater or a roll coater, the MFR is preferably from 30 to 2,000 g/10 minutes, and more preferably from 50 to 2,000 g/10 minutes. It is difficult to obtain polyethylene and polypropylene having an MFR exceeding 2,000 g/10 minutes or less than 0.1 g/10 minutes from the market.
It is preferred that polyethylene constituting component (A) has a tensile breaking strength (in accordance with JIS K6760) of 9.8 to 1,960 N/cm
2
(1 to 200 kgf/cm
2
). When polyethylene having a tensile breaking strength exceeding 1,960 N/cm
2
is used, the film strength of the moistureproof hot melt composition of the present invention is increased, resulting in a tendency to poor disintegrating properties.
The compounding ratio of polyethylene and/or polypropylene (A) is from 20% to 90% by weight, preferably from 30% to 80% by weight, and more preferably from 40% to 80% by weight, for a two-component system (composition (1)). When the compounding ratio is less than 20% by weight, a moistureproof layer is liable to have a crack when folded. On the other hand, exceeding 90% by weight results in poor disintegrating properties.
For a three-component system (composition (2)), the compounding ratio thereof is from 20% to 90% by weight, preferably from 30% to 80% by weight, and more preferably from 40% to 70% by weight. When the compounding ratio is less than 20% by weight, a moistureproof layer is liable to have a crack when folded. On the other hand, exceeding 90% by weight results in poor disintegrating properties.
The most preferable MFR of the EVA (D) used in the present invention varies depending on the coating method of the moistureproof hot melt composition and the vinyl acetate content of the EVA (D) . For example, in T-die extrusion coating, the MFR is preferably from 0.1 to 200 g/10 minutes, more preferably from 0.1 to 50 g/10 minutes, and particularly preferably from 0.1 to 30 g/10 minutes. On the other hand, in coating with a head coater or a roll coater, the MFR is preferably from 0.1 to 2,000 g/10 minutes, more prefera
Kuno Tatsuhiro
Nishikiori Yoshitada
Shimokado Takaichiro
Michl Paul R.
Yasuhara Chemical Co., Ltd.
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