JP6210582B2 - Cellulose fiber-dispersed polyethylene resin composite, molded body and pellets using the same, and method for recycling cellulose fiber-attached polyethylene thin film pieces - Google Patents

Description

  The present invention relates to a cellulose fiber-dispersed polyethylene resin composite, a molded body and pellets using the same, and a method for recycling a cellulose fiber-attached polyethylene thin film piece.

Laminated paper that constitutes a paper beverage container such as a milk pack is a laminate in which a polyethylene thin film is attached to the surface of a paper mainly made of cellulose fibers. Pulp) and the polyethylene thin film portion need to be separated.
The separation method is generally a method in which the paper part is peeled off from the laminated paper by stirring the laminated paper in water for a long time in an apparatus called a pulper. Is a raw material for recycled paper.
However, the polyethylene thin film is in a state in which a large number of paper components (paper pieces made of cellulose fibers) are non-uniformly attached to the surface, and the size and shape vary, and the cellulose fibers attached to the polyethylene thin film are A large amount of water is absorbed during the paper separation process by the pulper. In order to reuse such a polyethylene thin film as a raw material for resin products, a sufficient drying process is required, and much energy is consumed for reuse. Further, since the raw materials are not uniform in size and shape, it has been difficult to obtain a resin having a homogeneous composition and physical properties by kneading them. Therefore, at present, such a cellulose fiber-attached polyethylene thin film piece is buried as it is and discarded or reused as fuel.
Therefore, from the viewpoint of reducing the environmental load, development of a technology capable of reusing the polyethylene thin film as a raw material for resin products has been desired.

  Japanese Unexamined Patent Publication No. 2000-62746 (Patent Document 1) discloses a mold forming technique for producing a packaging tray by reusing a used beverage container made of laminated paper. The separated cellulose fiber-attached polyethylene thin film pieces are dried and pulverized, then formed into a plate shape by a primary molding machine, and further molded into a predetermined shape such as an egg packaging tray using a heat molding machine. The technology to do is described.

  Japanese Patent No. 4680000 (Patent Document 2) discloses a technique for reusing used beverage containers made of laminated paper, in which the laminated paper is crushed as it is without being separated into a paper portion and a polyethylene thin film portion. In addition, a method is described in which a paper-containing resin composition is produced by kneading with polypropylene or the like with a twin screw extruder, and a fluidity improver is further added thereto, followed by injection molding.

Japanese Patent No. 4950939 (Patent Document 3) discloses a technique of reusing a used PPC paper and a PET material such as a used beverage container in combination, and finely cutting the PPC paper. In addition, a method is described in which an injection molding resin is prepared by kneading in the presence of subcritical water together with a finely cut PET material after water is contained.
The technique of Patent Document 3 makes it possible to mix the cellulose fibers of the PPC paper and the molten PET material relatively uniformly by kneading the PPC paper and the PET material in the presence of subcritical water. Is.

  In addition, it is known that when cellulose fibers are uniformly dispersed in a resin, the physical properties are improved, for example, the bending strength is improved as compared with the resin alone. For example, in JP 2011-93990 A (Patent Document 4), non-fibrillated fibrous cellulose and a thermoplastic resin are melt-kneaded using a batch-type closed kneading apparatus, so that the strength containing cellulose fibers is increased. A technique for producing a high resin molding is disclosed.

JP 2000-62746 A Japanese Patent No. 4680000 Japanese Patent No. 4950939 JP 2011-93990 A

  However, in the technique described in Patent Document 1, a packaging tray is simply manufactured by mold molding without performing kneading in a molten state, and is not melt kneaded in a subcritical state as described later. Therefore, in Patent Document 1, paper waste containing polyethylene is finely pulverized to perform mold molding. However, since there is no melt-kneading step, the distribution of cellulose is biased. Furthermore, in the molding, the material is merely heat-fused without remelting the material, and there are few fusion parts between the thin film pieces, and the dispersed state of the cellulose fibers cannot be sufficiently uniformed, and the resulting molded product There exists a problem that the intensity | strength of the melt | fusion part of this is low. Moreover, since this molded object is in the state in which many cellulose fibers were exposed from resin, it has the characteristic that it is easy to absorb water and it is hard to dry, and the use will be limited.

  Moreover, in the technique described in Patent Document 2, the paper portion is not peeled off from the laminated paper and pulverized to a fine particle size of 0.5 mm to 2.5 mm, and polypropylene or modified polypropylene is added. A paper-containing resin composition is obtained by kneading, and further, a mixture containing a fluidity improver is added thereto for injection molding. That is, the technique described in Patent Document 2 does not melt and knead cellulose fiber-attached polyethylene thin film pieces containing moisture obtained from waste paper of laminated paper in a subcritical state. Furthermore, Patent Document 2 describes a paper-containing resin composition containing softwood bleached chemical pulp. However, the resin used in this composition is polypropylene or modified polypropylene resin, not polyethylene. Furthermore, in the technique described in Patent Document 2, the amount of cellulose contained in the paper-containing resin composition is relatively large, and as it is, good fluidity cannot be obtained at the time of kneading. There is a problem in that there are variations and portions where sufficient strength cannot be obtained. In order to solve this, Patent Document 2 describes that polypropylene or a fluidity improver is separately added as a raw material, but does not describe the use of polyethylene.

Further, Patent Document 3 discloses a resin for injection molding by making PPC paper, which is used discharged paper discharged from an office, water, dehydrated, mixed with PET resin or PP resin, and subjected to subcritical or supercritical processing. It is invention regarding the manufacturing method which manufactures.
The invention described in Patent Document 3 simply recycles PPC waste paper and PET recycled resin containers by separately preparing them, mixing and recycling them, and removing the paper components by pulping paper beverage containers. It does not recycle thin-film pieces that contain a large amount of water, vary in size and shape, and in which cellulose is unevenly adhered to the resin.
In the technique described in Patent Document 3, a large number of cellulose fibers constituting PPC paper are intertwined in a complicated manner, and it is difficult to sufficiently disentangle them into pieces, so that the PPC paper is finely cut. Is used.
In addition, PPC paper is superior in water absorption from the cut surface, so that the surface area of the cut surface is increased. Therefore, if the PPC paper is not cut finely and subjected to water-containing or dehydration treatment, cellulose fibers by subcritical or supercritical processing are used. Defibration does not progress sufficiently. If this cutting is not performed sufficiently, not a few pieces of paper (agglomerated cellulose fibers) remain in the produced injection molding resin, which reduces the strength of the injection molding resin and the water absorption characteristics. There is a problem that can cause

Furthermore, in the technique described in Patent Document 4, when thermoplastic resin and fibrous cellulose are separately supplied into a stirring chamber of a batch-type melt mixing device, the thermoplastic resin and fibrous cellulose are melt-kneaded. The fibrous cellulose is not melted and the thermoplastic resin is melted. That is, in the technique described in Patent Document 4, the raw material used is a so-called pure product suitable for obtaining the target resin composition, contains a large amount of water as described above, and varies in size and shape. It does not recycle thin-film pieces in which cellulose is unevenly adhered.
In addition, when thermoplastic resins and fibrous cellulose having different physical properties are separately added and mixed together, it is difficult to disperse the fibrous cellulose in the thermoplastic resin in a sufficiently uniform state to form an integrated resin composition. . That is, lumps or the like in which fibrous cellulose is aggregated are likely to occur, and there is a possibility that the strength of the resin molded body is reduced. Therefore, Patent Document 4 describes the use of fibrous cellulose having an aspect ratio of 5 to 500.

In the present invention, a paper component (cellulose fiber) that cannot be completely removed is obtained by removing a paper portion by stirring a polyethylene laminated paper having a polyethylene thin film adhered to the paper surface in water. Cellulose fibers are sufficiently adhered to the polyethylene resin while the cellulose fibers are peeled off from the surface of the cellulose fiber-attached polyethylene thin film pieces using the cellulose fiber-attached polyethylene thin film pieces of various sizes and shapes that adhere unevenly to the thin film. It is an object of the present invention to provide a method for producing a cellulose fiber-dispersed polyethylene resin composite that can be dispersed in a uniform state and is simple and excellent in energy efficiency (low power consumption).
Further, the present invention comprises cellulose fibers dispersed in a polyethylene resin in a sufficiently uniform state, low moisture content, low water absorption, excellent moldability by extrusion molding, injection molding, etc., bending strength and resistance. It is an object of the present invention to provide a cellulose fiber-dispersed polyethylene resin composite material capable of producing a molded article having excellent impact properties and the like.
Furthermore, this invention makes it a subject to provide the molded object excellent in bending strength, impact resistance, etc. which uses the said cellulose fiber dispersion | distribution polyethylene resin composite material.
In addition, the present invention provides a recycling method by reusing a polyethylene laminated paper and a cellulose fiber-attached polyethylene thin film piece from which the paper portion has been removed from the processed paper into a cellulose fiber-dispersed polyethylene resin composite. This is the issue.

As a result of intensive studies in view of the above problems, the present inventors stir polyethylene laminated paper constituting a paper beverage container such as a milk pack in water, peel off and remove the paper portion by this stirring, A polyethylene thin film piece with cellulose fibers that could not be removed was obtained, and this thin film piece was poured into the closed space while absorbing a large amount of water, and kneaded vigorously. The water can be changed to a subcritical state, and by kneading in the presence of such subcritical water, the cellulose fibers can be dispersed in a sufficiently uniform state in the polyethylene resin. This melt-kneading can remove moisture almost completely, so that a composite material in which polyethylene resin and cellulose fiber are integrated is an excellent energy source. It has been found that can be obtained in ghee efficiency.
That is, as described above, cellulose fiber and polyethylene resin are integrated by melting and kneading the above-mentioned polyethylene thin film piece, which has been a high hurdle for reuse as a resin raw material, while acting on subcritical water. It was found that a composite material with excellent uniformity was obtained.
The present invention has been further studied based on these findings and has been completed.

That is, the said subject was solved by the following means.
[1]
In the molecular weight pattern obtained by gel permeation chromatography (GPC) measurement, cellulose fibers are dispersed in a polyethylene resin satisfying the relationship of 1.7> full width at half maximum (Log (MH / ML))> 1.3. A cellulose fiber-dispersed polyethylene resin composite material comprising the cellulose fiber-dispersed polyethylene resin composite material, wherein the cellulose fiber-dispersed polyethylene resin composite material comprises 1% by mass or more and less than 50% by mass of cellulose fiber.
[2]
The cellulose fiber-dispersed polyethylene resin composite material according to [1], wherein the water absorption rate of the cellulose fiber-dispersed polyethylene resin composite material satisfies the following formula.
[Formula 1] (Water absorption) <(cellulose effective mass ratio) ² × 0.01
[3]
The cellulose fiber-dispersed polyethylene resin composite contains 1% by mass or more and less than 10% by mass of cellulose fiber, and the molded product has a bending strength of 8 to 20 MPa when the cellulose fiber-dispersed polyethylene resin composite is molded. ] Or the cellulose fiber-dispersed polyethylene resin composite material according to [2].
[4]
The cellulose fiber-dispersed polyethylene resin composite contains 10% by mass or more and less than 50% by mass of cellulose fiber, and the molded product has a bending strength of 15 to 40 MPa when the cellulose fiber-dispersed polyethylene resin composite is molded. ] Or the cellulose fiber-dispersed polyethylene resin composite material according to [2].
[5]
The cellulose fiber-dispersed polyethylene resin composite material according to any one of [1] to [4], wherein a melt flow rate (MFR) at a temperature of 230 ° C. and a load of 5 kgf is 0.5 to 10.0 g / 10 min.
[6]
The cellulose fiber-dispersed polyethylene resin composite according to any one of [1] to [5], wherein the polyethylene resin constituting the cellulose fiber-dispersed polyethylene resin composite includes low-density polyethylene.
[7]
The cellulose fiber dispersion according to any one of [1] to [6], wherein the polyethylene resin constituting the cellulose fiber-dispersed polyethylene resin composite includes one or more of linear low-density polyethylene and high-density polyethylene. Polyethylene resin composite material.
[8]
The cellulose fiber-dispersed polyethylene resin composite material according to any one of [1] to [7], wherein the moisture content is less than 1% by mass.
[9]
In the molecular weight pattern of integral display obtained as a result of molecular weight analysis obtained by gel permeation chromatography (GPC) measurement, the shoulder of the peak on the low molecular side where the peak shape is flattened is 10 ⁴ to 4 × 10 ⁴ . The cellulose fiber-dispersed polyethylene resin composite material according to [1], wherein cellulose fibers containing cellulose having a mass smaller than the mass of the polyethylene resin are dispersed in a polyethylene resin present in a range.
[10]
A test piece having a length of 100 mm, a width of 100 mm, and a thickness of 1 mm was prepared using the cellulose fiber-dispersed polyethylene resin composite, and the water absorption after being immersed in water at 23 ° C. for 20 days was 0.1 to 10%. In addition, the impact resistance of a test piece having a length of 80 mm, a width of 10 mm, and a thickness of 4 mm produced using the composite material is higher after being immersed in water at 23 ° C. than for 20 days, [1 ] The cellulose fiber-dispersed polyethylene resin composite material according to any one of [9] to [9].
[11]
The cellulose fiber-dispersed polyethylene resin composite material according to any one of [1] to [10], which is obtained using a cellulose fiber-attached polyethylene thin film piece to which cellulose fibers are attached.
[12]
The cellulose fiber-dispersed polyethylene resin composite material according to any one of [1] to [11], wherein the shape is a pellet.
[13]
The molded object using the cellulose fiber dispersion | distribution polyethylene resin composite material of any one of [1]-[12].
[14]
[13] A pellet comprising the molded article according to [13] or a cut piece thereof.

In the present invention, the invention of “cellulose fiber-dispersed polyethylene resin composite” is also specified by the manufacturing method as its specific matter. The reason will be explained.
The cellulose fiber-dispersed polyethylene resin composite material of the present invention is a subcritical state in which a cellulose fiber-attached polyethylene thin film formed by adhering a small amount of cellulose fibers to the polyethylene thin film piece as a mean of the mass of the material used is attached to the polyethylene thin film piece. It can be obtained by melt kneading with the action of water. In the cellulose fiber-dispersed polyethylene resin composite material, as will be described later, cellulose fibers are dispersed in a sufficiently uniform state in the polyethylene resin. This cellulose fiber-dispersed polyethylene resin composite material is excellent in the dispersion state of cellulose fibers in polyethylene, and cellulose fibers and polyethylene resin are integrated so to speak. In addition, because there are a wide variety of paper beverage container manufacturers and types of containers, including impurities, it is virtually difficult to unambiguously define the detailed composition etc. even if the main constituent materials can be specified. is there. Therefore, in order to clarify the invention by clarifying the difference from the prior art, the manufacturing method is part of the invention of the cellulose fiber-dispersed polyethylene resin composite material.

  In the present invention, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  In the present invention, the term “polyethylene” means low density polyethylene, linear low density polyethylene and / or high density polyethylene. That is, polyethylene means that an α-olefin other than ethylene may be included as a monomer component in addition to ethylene.

  According to the method for producing a cellulose fiber-dispersed polyethylene resin composite in the present invention, a paper part is peeled off and removed from a polyethylene-laminated paper having a polyethylene thin film attached to the surface of a paper, such as a used beverage container. Cellulose fiber-dispersed polyethylene resin composite material in which cellulose fibers are dispersed in a polyethylene resin in a sufficiently uniform state, with a low moisture content and a low water absorption rate, using a cellulose fiber-attached polyethylene thin film piece as a raw material. It can be obtained with high energy efficiency.

  Further, in the cellulose fiber-dispersed polyethylene resin composite material in the present invention, cellulose fibers are dispersed in a polyethylene resin in a sufficiently uniform state, and since the moisture content is low and the water absorption rate is also low, extrusion molding, injection molding, etc. Adaptability to is high. Moreover, the molded object excellent in bending strength, impact resistance, etc. can be obtained by shape | molding the cellulose fiber dispersion polyethylene resin composite material in this invention.

  Furthermore, the molded article of the present invention is made of the cellulose fiber-dispersed polyethylene resin composite material of the present invention, and the cellulose fibers are sufficiently uniformly dispersed in the resin, so that the homogeneity is high and the shape stability is high. In addition to being superior in bending strength and impact resistance, it can be used for various purposes.

  In addition, according to the recycling method of the present invention, polyethylene laminated paper such as used beverage containers, and cellulose fiber-attached polyethylene thin film pieces obtained by peeling off and removing the paper portion from the processed paper are subjected to extrusion molding and injection molding. By reusing it for highly adaptable cellulose fiber-dispersed polyethylene resin composites, it is possible to effectively use the cellulose fiber-attached polyethylene thin film pieces, which had been difficult to reuse as a resin in the past. It can be greatly reduced.

It is drawing which shows an example of the half value width of molecular weight distribution. The width indicated by the arrow in FIG. 1 is the half-value width. It is drawing which shows an example of the shoulder part of the low molecular side peak in which the peak shape was flattened in the molecular weight pattern.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

[Method for producing cellulose fiber-dispersed polyethylene resin composite]
<Cellulose fiber-attached polyethylene thin film pieces>
In polyethylene laminated paper such as paper beverage containers, generally, high-quality pulp that is strong and beautiful in appearance is used as the material of the paper portion, and such pulp is mainly composed of cellulose fibers. And the polyethylene thin film is affixed by the polyethylene extrusion lamination process on the surface of this paper part, and it is trying to prevent the penetration | invasion of the drink to a paper part.
In the present invention, the polyethylene-laminated paper is not particularly limited as long as it is a paper that has been subjected to polyethylene laminating, and a wide variety of paper such as beverage containers can be used.

In order to recycle such a laminated paper, generally, it is put into a pulper and stirred in water, whereby the paper portion is peeled off from the laminated paper and separated into a polyethylene thin film portion and a paper portion. In that case, the polyethylene film portion, for example a few cm 2 ^~ ten cm ² or two tens cm ^2, the size, shape and cut into uneven pieces, the side surface of the paper portion thereof is peeled off In this case, a large number of cellulose fibers that could not be removed remained non-uniformly attached (the polyethylene thin film pieces to which the cellulose fibers were attached are hereinafter referred to as “cellulose fiber-attached polyethylene thin film pieces”). can get. Further, the cellulose fiber-attached polyethylene thin film piece has a small amount of cellulose fiber due to the removal of the paper by the pulper. When viewed as an aggregate of cellulose fiber-attached polyethylene thin film pieces (entire thin film raw material), the mass of cellulose fibers is less than the mass of polyethylene in the dry mass. The cellulose fibers of the cellulose fiber-attached polyethylene thin film pieces are in a state of absorbing a large amount of water during the separation treatment by the pulper.

  In the present invention, the cellulose adhering to the “cellulose fiber-attached polyethylene thin film piece” may be in a state where the fibers are dispersed without contacting each other, or the fibers may be entangled to maintain a paper state. The “cellulose fiber-attached polyethylene thin film piece” may contain polyethylene, cellulose, a filler (eg, kaolin, talc), a sizing agent, and the like that are generally included to increase the whiteness of paper. In addition, other components may be included as long as the effects of the present invention are not impaired. For example, various additives, ink components, other trace amounts of sealing material, anti-adhesive agent, and the like included in the raw material polyethylene laminated paper may be included. The content of the other components in the cellulose fiber-attached polyethylene thin film piece (in the cellulose fiber-attached polyethylene thin film piece excluding moisture) is usually 0 to 10% by mass, preferably 0 to 5% by mass, 3% by mass is more preferable.

  The amount of cellulose fibers adhering to the polyethylene thin film piece needs to be smaller than the polyethylene weight of the thin film piece in dry mass. This is because when the cellulose fiber adhesion amount is larger than the mass of polyethylene, it is difficult to uniformly disperse the cellulose fiber in the resin when producing the cellulose fiber-dispersed polyethylene resin composite.

<Action by subcritical water>
In the method for producing a cellulose fiber-dispersed polyethylene resin composite of the present invention, the above-described cellulose fiber-attached polyethylene thin film piece is melt-kneaded in the presence of subcritical water. That is, a cellulose fiber-dispersed polyethylene resin composite can be produced by melt-kneading while allowing subcritical water to act.
Here, “subcritical water” refers to water in a high temperature and high pressure state that does not reach the supercritical state (temperature of 374 ° C. and pressure of 22 MPa), and more specifically, temperature. Is the boiling point of water at atmospheric pressure (100 ° C.) or more and not more than the critical point of water, and the pressure is at least near the saturated water vapor pressure.
It is estimated that the water in the subcritical state has an ionic product larger than that of water at 0 ° C. or more and 100 ° C. or less under atmospheric pressure, and the action of decomposing a polymer such as cellulose to lower the molecular weight is enhanced. This action causes molecular weight reduction due to decomposition of cellulose fibers and polyethylene, and the addition of shearing force by melt kneading and reaction in the subcritical state act on the adhesive interface when cellulose and polyethylene are laminated. The cellulose fibers are separated and released from the state in which the cellulose fibers are embedded and fixed or heat-sealed on the polyethylene resin surface, and the action also contributes to the relaxation of the entanglement between the cellulose fibers that maintain the paper shape, It is considered that a resin dispersed in a sufficiently uniform state in polyethylene is obtained. Utilizing such a reaction, cellulose fiber dispersed resin composite with uniform physical properties from cellulose fiber-attached polyethylene thin film pieces as a composite of cellulose fiber and polyethylene, with non-uniform size, shape, and cellulose fiber adhesion state It is possible for the first time to produce materials.

  In order to melt-knead cellulose fiber-attached polyethylene thin film pieces in the presence of subcritical water, for example, melt-knead a mixture of cellulose fiber-attached polyethylene thin film pieces and water in the subcritical state of the water. Can do.

There is no particular limitation on the method for melt-kneading the cellulose fiber-attached polyethylene thin film pieces in the presence of subcritical water. For example, by putting a cellulose fiber-attached polyethylene thin film piece and water into a closed space and kneading the thin film piece and water vigorously in the closed space, the temperature and pressure in the space rise, and the water becomes subcritical. It becomes possible to change to a state.
In the present invention, “closed” is a space closed from the outside, but is used to mean that it is not completely sealed. That is, it means a space provided with a mechanism in which the temperature and pressure rise when vigorously kneading the thin film pieces and water in the closed space as described above, but the steam is discharged to the outside under such high temperature and pressure. Therefore, it is possible to remove moisture substantially completely by melt-kneading the thin film piece and water in a subcritical state in the closed space.

  For the melt-kneading of the thin film pieces and water in the closed space described above, for example, a batch type closed kneader can be suitably used. As such a batch type closed kneading apparatus, for example, a batch type high speed stirring apparatus described in International Publication No. 2004/076044 manufactured by M & F Technology, Inc. can be suitably used. This batch-type closed kneading apparatus is provided with a cylindrical stirring chamber, and a total of six stirring blades are projected from the outer periphery of a rotating shaft disposed through the stirring chamber. Yes. In addition, a mechanism for releasing water vapor while maintaining the pressure in the stirring chamber is provided at both ends of the rotating shaft.

  The temperature and pressure in the stirring chamber rapidly increase when a high shearing force is applied to a raw material such as a cellulose fiber-attached polyethylene thin film piece by a rotating stirring blade, and subcritical water is generated. In this way, cellulose fiber is embedded in the surface of the polyethylene thin film by heat-sealing at the time of laminating due to the hydrolytic action of cellulose by subcritical water and strong shearing force by high-speed stirring. It is considered that cellulose fiber can be uniformly dispersed in polyethylene.

<Manufacturing process of cellulose fiber-dispersed polyethylene resin composite>
In the method for producing a cellulose fiber-dispersed polyethylene resin composite of the present invention, a cellulose fiber-attached polyethylene thin film formed by adhering a small amount of cellulose fibers to the polyethylene thin film piece in the presence of subcritical water is obtained. Melt and knead.
In addition, in this specification, when referring to the mass ratio of polyethylene and cellulose fiber, it means the ratio of dry mass. In addition, the mass ratio of polyethylene and cellulose fibers in the cellulose fiber-attached polyethylene thin film piece is also referred to as the mass ratio ("average of dry mass ratio") of the whole cellulose fiber-attached polyethylene thin film piece (an aggregate of the cellulose fiber-attached polyethylene thin film pieces used) ).

As described above, the cellulose fiber-attached polyethylene thin film piece as a raw material needs to have a smaller amount of attached cellulose fiber than the mass of polyethylene constituting the thin film portion. For thin film pieces with a relatively small amount of cellulose fiber attached, as described above, the polyethylene-laminated paper is agitated in water (meaning in water or hot water) and the paper portion is peeled off to some extent. There is a tendency that partially defibrated paper and cellulose fibers are thinly entangled and adhered to the surface of the thin film piece. In addition, for each of the thin film pieces of cellulose fiber, the quantitative ratio is slightly different, but because a polyethylene thin film piece to which the cellulose fiber from which the paper component has been removed is attached from the paper beverage container by the pulper treatment is used. In comparison with the dry mass, the average value of the mass of the cellulose fiber of the polyethylene thin film piece to which the cellulose fiber is adhered is smaller than the average value of the mass of the polyethylene thin film excluding the cellulose (that is, the whole polyethylene thin film piece to which the cellulose fiber is adhered). The mass of cellulose fibers is less than the mass of polyethylene). In addition, the average value of the adhesion mass of the cellulose fibers can be controlled to some extent by the rotation speed and processing time in the pulper processing step.
In other words, the thin film piece has a cellulose fiber bonded to the polyethylene layer on the entire surface, and the adhesive interface when laminating the polyethylene and the polyethylene is a combination of shearing force by melt-kneading and subcritical reaction. Is released from the fixed or heat-sealed state embedded in the polyethylene resin surface, and the cellulose shape is changed from paper shape to fiber shape by releasing each cellulose fiber from the network-like entanglement of cellulose fibers. Thus, the cellulose fibers can be uniformly dispersed in the polyethylene resin.

  In addition, the cellulose fiber-attached polyethylene thin film piece absorbs a lot of water during the separation process from the paper portion, and it is difficult to reuse even in consideration of energy consumption at the time of reuse. However, since the melt kneading in the present invention is performed in the presence of subcritical water, water is required. Therefore, a large amount of water absorption of the thin film piece is not a problem at all, and there is an advantage that the labor for adding water can be reduced. Moreover, in melt kneading, water can be efficiently discharged as high-temperature steam, so that it is considered that the moisture content of the obtained composite material can be highly suppressed.

Thus, in the case of producing a cellulose fiber-dispersed polyethylene resin composite material using a cellulose fiber-attached polyethylene thin film piece as a raw material, the amount of cellulose fibers attached to the polyethylene thin film piece is less than the mass of polyethylene in the thin film portion, When other raw materials are used, for example, as in Patent Document 4, non-fibrillated fibrous cellulose is purchased, and compared with a production method in which this and thermoplastic resin are added as separate raw materials, non-fibrillar Cellulose can be obtained directly from the thin film piece as a waste material without purchasing modified fibrous cellulose, so that the cost is excellent, the manufacturing process is simple, and the energy efficiency is high. The invention of Patent Document 4 aims to improve the dispersion state of non-fibrillated cellulose fibers in a thermoplastic resin, and pays attention to the effect of lowering the molecular weight by melting and kneading each resin at a high temperature. Absent. In one embodiment of the present invention, the molecular weight distribution is controlled by lowering the molecular weight of the polyethylene of the cellulose fiber-dispersed polyethylene resin composite obtained by subcritical processing, thereby adjusting the MFR to a predetermined range and simultaneously setting the physical properties of the polyethylene resin. It becomes possible to maintain the range.

  When the raw material containing cellulose fiber-attached polyethylene thin film pieces and water are put into a closed space such as a batch-type closed kneader, the cellulose fiber-attached polyethylene thin film pieces are pulverized or reduced as necessary, You may process to the size and bulk density which are easy to handle and can be dropped into the batch type closed kneader. In particular, by performing the volume reduction treatment, the energy efficiency until the composite material is obtained can be greatly improved.

Moreover, since water can use the impregnation water of the cellulose fiber adhering to the cellulose fiber adhesion polyethylene thin film piece as above-mentioned, the adhesion water of the surface of a thin film piece, etc. as it is, if water is added as needed good.
Note that the amount of water necessary for kneading in the presence of subcritical water is 5 parts by mass or more and less than 150 parts by mass with respect to 100 parts by mass of the cellulose fiber-attached polyethylene thin film piece. For example, a cellulose fiber-dispersed polyethylene resin composite material in which cellulose fibers are uniformly dispersed in the resin and the water content is less than 1% by mass and excellent in moldability can be produced.

Next, a method for melt-kneading raw materials while bringing water into a subcritical state using a batch type closed kneader will be described.
The batch type closed kneading apparatus is provided with a cylindrical stirring chamber, and a total of six stirring blades project from the outer periphery of a rotating shaft disposed through the stirring chamber. ing. The rotating shaft on which the stirring blades are arranged is connected to a motor that is a drive source, but in the present invention, a torque meter that measures the rotating torque applied to the motor is installed, and the rotating torque can be monitored on the control panel. In the method for producing a cellulose fiber-dispersed polyethylene resin composite of the present invention, the change in the rotational torque of the rotational shaft measured from a torque meter is measured to determine the end point of kneading.

The end point of kneading is appropriately adjusted in consideration of the physical properties of the obtained composite material. Preferably, after the rotational torque of the rotary shaft of the batch type closed kneading apparatus rises and reaches a maximum value, the torque decreases and the torque becomes 0.7 times the maximum value. It is preferable to stop the rotation of the rotary shaft within 30 seconds from the time when the rate becomes 5% per second. By doing so, the melt flow rate (MFR: temperature = 230 ° C., load = 5 kgf) of the obtained cellulose fiber-dispersed polyethylene resin composite can be easily adjusted to 0.5 to 10.0 g / 10 min, and the physical properties are further improved. Can be made. Cellulose fiber-dispersed polyethylene resin composites having a melt flow rate within the above range have cellulose fibers uniformly dispersed in the resin, suitable for extrusion molding or injection molding, and having shape stability, strength and impact resistance. A high molded article can be produced.
The reason why the melt flow rate of the cellulose fiber-dispersed polyethylene resin composite can be adjusted by controlling the end point of the kneading is that some of the molecules of the polyethylene and cellulose fibers are caused by the action of subcritical water generated during the kneading. It is presumed that the decrease in molecular weight is one factor.
In this specification, “the torque change rate is 5% per second” means that the torque T1 at a certain time point and the torque T2 after one second from the time point satisfy the following formula (T).
Formula (T) 100 × (T1-T2) / T1 = 5

The method for producing a cellulose fiber-dispersed polyethylene resin composite of the present invention melts and kneads a cellulose fiber-attached polyethylene thin film piece in the presence of subcritical water. In this case, the preferable range of the amount of water required is 5 parts by mass or more and less than 150 parts by mass with respect to 100 parts by mass of the cellulose fiber-attached polyethylene thin film piece. The material can be made substantially free of moisture, and a molded product using this composite material can have excellent bending strength and impact resistance. When the cellulose fiber-attached polyethylene thin film contains water, the water necessary for kneading is usually not necessary to be added separately. On the other hand, even when the cellulose fiber-attached polyethylene thin film piece is impregnated with a considerable amount of water, it can usually be kneaded without any problem and the desired composite material can be obtained. This is because water efficiently evaporates in a high temperature and high pressure environment.
The amount of water in the vapor melt kneading is preferably 5 to 150 parts by mass, more preferably 5 to 120 parts by mass, and further preferably 5 to 100 parts by mass with respect to 100 parts by mass of the cellulose fiber-attached polyethylene thin film piece. More preferably, it is 5-80 mass parts, and it is still more preferable to set it as 10-25 mass parts.

[Cellulose fiber-dispersed polyethylene resin composite and molded article thereof]
The cellulose fiber-dispersed polyethylene resin composite of the present invention is obtained by the above-described method for producing the cellulose fiber-dispersed polyethylene resin composite of the present invention. In the cellulose fiber-dispersed polyethylene resin composite of the present invention, cellulose fibers are dispersed in a polyethylene resin in a sufficiently uniform state, and is highly adaptable to extrusion molding and injection molding.

The cellulose fiber-dispersed polyethylene resin composite of the present invention desirably contains 1% by mass or more and less than 50% by mass of cellulose fiber. This is because when the ratio of the cellulose fiber is 50% by mass or more, the impact resistance is lowered and the water tends to be easily absorbed.
The cellulose fiber-dispersed polyethylene resin composite of the present invention contains 1% by mass or more and less than 10% by mass of cellulose fiber, and the molded product formed by molding the cellulose fiber-dispersed polyethylene resin composite has a bending strength of 8 to 20 MPa. It is preferable.
Further, the cellulose fiber-dispersed polyethylene resin composite of the present invention contains 10% by mass or more and less than 50% by mass of cellulose fiber, and the molded product formed by molding the cellulose fiber-dispersed polyethylene resin composite has a bending strength of 15 to 40 MPa. It is also preferable.
The bending strength is measured by the method described in Examples described later.

  The cellulose fiber-dispersed polyethylene resin composite of the present invention preferably has a moisture content of less than 1% by mass. By melt-kneading in the presence of the above-described subcritical water, water can be efficiently removed as steam during melt-kneading, and the water content of the resulting cellulose fiber-dispersed polyethylene resin composite is 1% by mass. It can be reduced to less than. Moreover, this method can significantly reduce the amount of energy used (such as power consumption) for removing moisture compared to the case where moisture removal and melt-kneading are performed in separate processes.

The cellulose fiber-dispersed polyethylene resin composite of the present invention preferably has a water absorption rate that satisfies the following formula. It is more preferable that the cellulose effective mass ratio described later is in the range of 5 to 40%. The “water absorption” (unit:%) is a value obtained when a molded article formed using a cellulose fiber-dispersed polyethylene resin composite and having a length of 100 mm, a width of 100 mm, and a thickness of 1 mm is immersed in water at 23 ° C. for 20 days. It is measured by the method described in the examples described later. In addition, “cellulose effective mass ratio” (unit:%) will be described in detail in Examples described later.

[Formula 1] (Water absorption) <(cellulose effective mass ratio) ² × 0.01

That is, the cellulose fiber-dispersed polyethylene resin composite of the present invention has a low water absorption rate despite containing cellulose fibers. The reason for this is not clear, but by melt-kneading the above-mentioned cellulose fiber-attached polyethylene thin film pieces in the presence of subcritical water, cellulose and polyethylene are in an integrated state. It is estimated that polyethylene effectively masks the water absorption rate. In addition, the hydrophilic group formed on the surface of the low molecular weight polyethylene may be bonded to the hydrophilic group on the cellulose surface, resulting in a decrease in the hydrophilic group on the surface, or the structural change or low molecular weight due to the degradation of cellulose by a subcritical reaction. There is a possibility that the hydrophilic group may be reduced by the conversion.

  When the cellulose fiber-dispersed polyethylene resin composite material of the present invention is formed into a molded body having a length of 100 mm, a width of 100 mm, and a thickness of 1 mm using the composite material, the molded body is immersed in water at 23 ° C. for 20 days. The water absorption is preferably 0.1 to 10%.

The cellulose fiber-dispersed polyethylene resin composite of the present invention has the property that it is difficult to absorb water as described above, but has the property that impact resistance is increased when water is absorbed after molding. Therefore, the molded body using the cellulose fiber-dispersed polyethylene resin composite of the present invention is also suitable for outdoor use.
The impact resistance is measured by the method described in Examples described later.

Decreasing the molecular weight of a cellulose fiber-dispersed resin polyethylene composite by subcritical processing is an important factor that affects the mechanical properties of the composite such as MFR, bending strength, and impact resistance. Therefore, it is preferable to control the molecular weight distribution of polyethylene within a predetermined range. In the present invention, as the molecular weight distribution of polyethylene, it is preferable to control the half-value width of the molecular weight distribution pattern and the molecular weight position of the shoulder of the low molecular peak as follows.
The polyethylene contained in the cellulose fiber-dispersed polyethylene resin composite of the present invention preferably satisfies the relationship of 1.7> full width at half maximum (Log (MH / ML))> 1.3 in the molecular weight pattern obtained by GPC measurement. . A composite material having a half width of 1.3 or less tends to be inferior in fluidity and injection moldability. A composite material having a full width at half maximum of 1.7 or more tends to reduce the impact strength of the molded body. Furthermore, in the molecular weight pattern obtained by GPC measurement, it is preferable that the shoulder of the peak on the low molecular side where the peak shape is flattened is in the range of 10 ⁴ to 4 × 10 ⁴ . In the present invention, by performing a subcritical reaction, the peak is flattened as the molecular weight pattern is reduced in molecular weight, and the shoulder on the low molecular side of the flattened peak is in the range of 10 ⁴ to 4 × 10 ⁴ . Can be controlled.
In addition, the half value width of a molecular weight pattern shows the spread of the spectrum (degree of molecular weight distribution) around the peak top (maximum frequency) of the maximum peak among the molecular weight patterns in GPC. That is, the width of the GPC spectrum line where the intensity in the spectrum is half the peak top (maximum frequency) (each having a high molecular weight side is MH and the low molecular weight side is ML) is the half-value width. The “peak shoulder on the low molecular side” will be described in detail in the examples described later.

  The cellulose fiber-dispersed polyethylene resin composite of the present invention preferably has a melt flow rate (MFR) at a temperature of 230 ° C. and a load of 5 kgf of 0.5 to 10.0 g / 10 min. By setting the MFR within the above preferable range, the water content and water absorption can be suppressed, better moldability can be realized, and the impact resistance of the obtained molded body can be further improved.

  The cellulose-dispersed polyethylene resin composite material of the present invention can be made into pellets by melting and solidifying into an arbitrary shape and size, or by cutting. For example, pellets can be obtained by extruding a pulverized product of the cellulose-dispersed polyethylene resin composite of the present invention into a strand shape by a twin screw extruder and cutting after cooling and solidification. Alternatively, pellets can be obtained by extruding and cutting the pulverized product of the cellulose-dispersed polyethylene resin composite of the present invention with a twin-screw extruder equipped with a hot cut. Although the size and shape of these pellets can be selected as appropriate, it can be finished into, for example, a substantially cylindrical or disk-shaped particle having a diameter of several mm.

  The cellulose-dispersed polyethylene resin composite of the present invention may contain polyethylene other than polyethylene derived from cellulose fiber-attached polyethylene thin film pieces. That is, in the manufacturing method of the cellulose-dispersed polyethylene resin composite of the present invention described above, polyethylene may be added separately in addition to the cellulose fiber-attached polyethylene thin film piece. The polyethylene to be blended may be low-density polyethylene, linear low-density polyethylene, or high-density polyethylene, and one or more of these may be mixed.

The molded article of the present invention is formed using the cellulose-dispersed polyethylene resin composite of the present invention. In the molded product of the present invention, cellulose fibers are dispersed in a polyethylene resin in a sufficiently uniform state, so that the homogeneity is high, the shape stability is excellent, and the bending strength and impact resistance are excellent. It can be used effectively.
The molded body of the present invention can also be used as a molding material in the form of pellets.

[Recycling method of cellulose fiber-attached polyethylene thin film pieces]
The recycling method of the cellulose fiber-attached polyethylene thin film of the present invention is a method of reusing the above-described cellulose fiber-attached polyethylene thin film as a raw material for resin products. More specifically, the cellulose fiber-attached polyethylene thin film piece is melted. And kneading under high temperature and high pressure that does not melt the cellulose fiber to obtain a cellulose fiber-dispersed polyethylene resin composite. For example, the same treatment may be performed by adding water to the cellulose fiber-attached polyethylene thin film piece.
According to such a recycling method, cellulose fiber-attached polyethylene thin film pieces separated from used polyethylene laminated paper, which are currently mainly discarded or reused as fuel, have excellent energy efficiency. Thus, it can be reused for a high-quality cellulose fiber-dispersed polyethylene resin composite.
Such kneading can be performed, for example, by melt-kneading the cellulose fiber-attached polyethylene thin film piece in the presence of subcritical water.
In the method for recycling the cellulose fiber-attached polyethylene thin film piece of the present invention, the step of obtaining the cellulose fiber-dispersed polyethylene resin composite material using the cellulose fiber-attached polyethylene thin film piece as a raw material is the method for producing the cellulose fiber-dispersed polyethylene resin composite material of the present invention. It is the same as the process demonstrated, and its preferable form is also the same.

  In the recycling method of the present invention, for example, in order to produce the composite material having a higher function or to expand the field of use of the composite material, for example, a low-density polyethylene and / or a straight-line together with a cellulose fiber-attached polyethylene thin film piece. A chain low density polyethylene or high density polyethylene may be added and kneaded.

[Recycling method of polyethylene laminated paper]
The recycling method of the polyethylene laminated paper of this invention includes performing the following process (A) and (B) continuously in this order.
(A) A step of subjecting the cellulose fiber-attached polyethylene thin film piece containing water to volume reduction treatment,
(B) A step of obtaining a cellulose fiber-dispersed polyethylene resin composite by melting and kneading the cellulose fiber-attached polyethylene thin film containing water, which has been subjected to volume reduction, in the presence of subcritical water.

The method for recycling polyethylene-laminated paper of the present invention preferably further includes performing the following step (C) before performing the step (A).
(C) The process of peeling and removing a paper part by stirring the polyethylene laminated paper by which the polyethylene thin film was stuck on the surface of paper in water, and obtaining the cellulose fiber adhesion polyethylene thin film piece containing water.

Typically, the step (C) is a step of peeling the paper portion from the laminated paper by stirring the laminated paper in water (in water or hot water) for a long time in an apparatus called a pulper as described above. It is. As this process, a conventionally known process in the reuse of polyethylene-laminated paper can be adopted.
The cellulose fiber-attached polyethylene thin film obtained in the step (C) usually has a water content of about 50% by mass and is in a state of absorbing a large amount of water. The cellulose fiber-attached polyethylene thin film piece is subjected to volume reduction treatment in the step (A). Water content is reduced by this volume reduction treatment, and the water content is usually around 20% by mass. Moreover, it is preferable to make volume into about 1 / 2.0-1 / 5.0 by this volume reduction process. The apparatus used for volume reduction treatment is not particularly limited, and for example, a biaxial waste plastic volume reduction solidification machine (model: DP-3N, manufactured by Oguma Iron Works Co., Ltd.) can be used.
The cellulose fiber-attached polyethylene thin film piece containing water that has undergone the step (A) is melt-kneaded in the presence of subcritical water to obtain a cellulose fiber-dispersed polyethylene resin composite. As the melt-kneading in the presence of water in the subcritical state, the form of melt-kneading described in the method for producing a cellulose fiber-dispersed polyethylene resin composite of the present invention can be employed, and the preferred form is also the same.

  By the recycling method by the above-mentioned continuous process, for example, it becomes unnecessary to transport the cellulose fiber-attached polyethylene thin film piece separated from polyethylene-laminated paper and containing a large amount of water to a different factory. The energy efficiency or cost of recycling can be greatly improved.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these.
First, a method for measuring and evaluating each index in the present invention will be described.

[Melt flow rate (MFR)]
The measurement was performed according to JIS-K7210 under the conditions of temperature = 230 ° C. and load = 5 kgf. The unit of MFR is “g / 10 min”.

[Shape of the resultant product (cellulose fiber-dispersed polyethylene resin composite)]
The appearance of the cellulose fiber-dispersed polyethylene resin composite after kneading was visually evaluated. The state of bulk (lumps) was an acceptable product (◯), and the one in powder form with a particle size of 2 mm or less, or the one that ignited significantly after kneading was regarded as an unacceptable product (x).
Cellulose fiber dispersion of polyethylene resin composite obtained by the production method of the cellulose fiber dispersion of polyethylene resin composite of the present invention are those corresponding to the accepted product.

[Formability]
Whether injection molding was possible and the appearance after molding were visually evaluated. A case where warpage or surface irregularities was confirmed was regarded as a rejected product (x), and a product other than the rejected product was regarded as a accepted product (◯).

[Moisture content]
It is a mass reduction rate (mass%) when thermogravimetric analysis (TGA) is performed at a temperature increase rate of + 10 ° C./min from 23 ° C. to 120 ° C. within 6 hours after production. A water content of 0% means that no mass loss occurs.

[Power consumption]
When a cellulose fiber-dispersed polyethylene resin composite material is continuously produced from cellulose fiber-attached polyethylene thin film pieces that have absorbed water, each device (dryer, volume reducer, kneader) is required to produce 1 kg of the composite material. The total amount of power consumed was obtained.

[Shock resistance]
A test piece (thickness 4 mm, width 10 mm, length 80 mm) was prepared by injection molding, and the Izod impact strength was measured using a notched test piece according to JIS-K7110. The unit of impact resistance is “kJ / m ² ”.

[Bending strength]
A test piece (thickness 4 mm, width 10 mm, length 80 mm) was prepared by injection molding, and a load was applied at a fulcrum distance of 64 mm, a radius of curvature of the fulcrum and the working point of 5 mm, and a test speed of 2 mm / min. The bending strength was calculated according to K7171. The unit of bending strength is “MPa”.

[Cellulose effective mass ratio]
Based on the results of thermogravimetric analysis (TGA) from 23 ° C. to 400 ° C. at a rate of temperature increase of + 10 ° C./min in a nitrogen atmosphere using a sample that had been completely dried in advance, the following formula was used. .
(Cellulose effective mass ratio [%]) =
(Weight reduction [g] at 270 to 390 ° C.) × 100 / (Sample weight [g])

[Water absorption rate]
The composite material which has been completely dried in advance is molded into a sheet of 100 mm × 100 mm × 1 mm with a press to obtain a molded body. This molded body is immersed in water at 23 ° C. for 20 days, and the weight before and after immersion is measured. Based on the value, the water absorption was calculated by the following [Formula A] (however, when measuring the mass after immersion, water droplets and the like adhering to the surface were wiped off with a dry cloth or filter paper). In the pass / fail judgment, a case where the calculated water absorption rate satisfies the following evaluation formula [Formula B] was determined to be acceptable (O), and a case where the calculated water absorption rate was not satisfied was determined to be unacceptable (X).
[Formula A] (water absorption [%]) =
(Mass after immersion [g] −Mass before immersion [g]) × 100 / (Mass before immersion [g])
[Formula B] (water absorption) <(cellulose effective mass ratio) ² × 0.01

[Shock resistance after water absorption]
A test piece (thickness 4 mm, width 10 mm, length 80 mm) was prepared by injection molding, this test piece was immersed in water at 23 ° C. for 20 days, and the impact resistance before and after immersion measured according to JIS-K7110. Based on the measured value, it was calculated by the following formula (however, when measuring the impact resistance after immersion, it was measured within 6 hours without intentionally drying after taking out from water) .)
(Shock resistance after water absorption [%]) =
(Impact resistance after water absorption [kJ / m ² ]) × 100 / (Impact resistance before water absorption [kJ / m ² ])

[Cellulose fiber dispersibility]
The composite material that has been completely dried in advance is molded into a sheet of 100 mm × 100 mm × 1 mm with a press to obtain a molded body, and the molded body is immersed in warm water at 80 ° C. for 20 days, and then molded from the warm water. A 40 mm × 40 mm square was written at an arbitrary location on the body surface, and nine 40 mm line segments were written at 4 mm intervals inside the square. Using a surface roughness measuring machine, under the conditions of a cutoff value λc = 8.0 mm and λs = 25.0 μm, roughness curves on the nine line segments (specified in JIS-B0601 and evaluated length) 40 mm) A total of 9 pieces were produced. When the number of peaks having a peak top of 30 μm or more and convex upward in all nine roughness curves was counted, a case where the total number of peaks was 20 or more was regarded as a rejected product (x). The case where it was less than 20 was set as the acceptable product (◯).
When cellulose fibers are unevenly distributed in the sample, water absorption occurs locally and the surface of the portion expands. Therefore, the dispersibility of the cellulose fibers can be evaluated by this method.

[Molecular weight pattern]
To 16 mg of the composite material, 5 ml of GPC measurement solvent (1,2,4-trichlorobenzene) was added and stirred at 160 ° C. to 170 ° C. for 30 minutes. Insoluble matter is removed by filtration with a 0.5 μm metal filter, and a GPC device (PL220 manufactured by Polymer Laboratories, model: HT-GPC-2) is used for the obtained sample (soluble matter) after filtration. The column uses Shodex HT-G (1), HT-806M (2) (manufactured by Showa Denko), the column temperature is set to 145 ° C., and 1,2,4-trichlorobenzene (0. GPC was measured by injecting 0.2 ml of the sample at a flow rate of 1.0 mL / min. From this, a calibration curve was prepared using monodispersed polystyrene (manufactured by Tosoh Corp.) and dibenzyl (manufactured by Tokyo Chemical Industry Co., Ltd.) as standard samples, and data processing was performed with a GPC data processing system (manufactured by TRC) to obtain a molecular weight pattern. In the molecular weight pattern obtained by GPC measurement, those satisfying both of the following (A) and (B) are (◎), those satisfying only (A) are (◯), and those not satisfying both are (×). .
(A) 1.7> full width at half maximum (Log (MH / ML))> 1.3
(B) The shoulder portion of the peak on the low molecular side where the peak shape is flattened is in the range of 10 ⁴ to 4 × 10 ⁴ .
Here, the full width at half maximum of the molecular weight pattern indicates the spread of the spectrum (degree of molecular weight distribution) around the peak top (maximum frequency) of the maximum peak in the molecular weight pattern in GPC. That is, the width of the GPC spectrum line where the intensity in the spectrum is half of the peak top (maximum frequency) (each high molecular weight side is MH and low molecular weight side is ML) is the half width (see FIG. 1). In addition, when a plurality of peaks are observed, calculation is performed from the maximum one of the peaks.
The shoulder of the peak on the low molecular side refers to the point (change point) where the cumulative frequency at the peak end of the molecular weight pattern changes abruptly. The change point is obtained by obtaining a tangent line from the flat part of the peak to the low molecular side, obtaining a tangent line from the flat part and a part where the cumulative frequency of molecular weight rapidly decreases, and a molecular weight pattern immediately below the intersection of these two tangents. It is assumed that the value is read (see FIG. 2).

[Test Example 1]
The influence of the amount of water when the cellulose fiber-attached polyethylene thin film pieces were kneaded by a batch type closed kneader was tested.

The paper part was peeled off and removed from the paper beverage container made of used polyethylene laminated paper with a pulper to obtain a cellulose fiber-attached polyethylene thin film piece. Such thin pieces, several cm 2 ^~ ten cm ² or two dozen cm ^2, of various shapes, are cut into pieces of size, wet by being immersed in water at stripping step of the paper portion It was a state (a state where a large amount of water was absorbed). Moreover, the mass ratio (after drying) of the polyethylene which comprises this thin film piece, and the cellulose fiber adhering to it was [polyethylene]: [cellulose fiber] = 56: 44.
This cellulose fiber-attached polyethylene thin film piece was dried for 48 hours with a drier set at 80 ° C. so that the water content was 1% by mass or less, and then water was added intentionally. Four types of sample materials were prepared so as to be parts by mass of water described in each column of “Example 3” and “Comparative Example 1”.
Next, these four kinds of sample materials are separately put into a batch type closed kneading apparatus (MF & F Technology Co., Ltd., MF type mixing and melting apparatus, model: MF5000 R / L), and stirred at high speed to supply water. The sample material was kneaded while being in a subcritical state, and four types of cellulose fiber-dispersed polyethylene resin composites were produced.
In each test example, unless otherwise specified, the kneading end point of the batch type closed kneading apparatus is lowered after the rotational torque of the rotating shaft of the batch type closed kneading apparatus increases to reach the maximum value. After the torque reaches 0.7 times the maximum value, the moment when the torque reaches the minimum value (that is, when the torque change rate reaches 5% per second) is the starting point, and 7 seconds after the starting point. It is said.
The evaluation results of each composite material are as shown in Table 1.

From “Comparative Example 1” in Table 1, when the melt kneading of the cellulose fiber-attached polyethylene thin film piece is performed in an environment where there is no water, the cellulose fiber-dispersed polyethylene resin composite of the present invention cannot be obtained. I understand.
Further, from Example 1, it is possible to obtain a cellulose fiber-dispersed polyethylene resin composite having excellent characteristics even though the amount of water is as small as 8: 100 in terms of mass ratio with the cellulose fiber-attached polyethylene thin film piece. I understand. Further, from “Example 3”, a cellulose fiber-dispersed polyethylene resin composite material having excellent characteristics was obtained although the amount of water was as large as 120: 100 in terms of mass ratio to the cellulose fiber-attached polyethylene thin film piece. Furthermore, it can be seen that the water content can be reduced to zero. Therefore, it can be seen that the amount of water may be large or small in the production method of the present invention in which melt-kneading is performed in the presence of subcritical water. In view of energy efficiency, it can be seen that it is preferable to reduce the amount of water to a certain extent.

[Test Example 2]
The relationship between the melt flow rate (MFR) of the composite material obtained by kneading the cellulose fiber-attached polyethylene thin film pieces with a batch type closed kneader and other characteristics was investigated.

In the same manner as in Example 1, a cellulose fiber-attached polyethylene thin film piece was obtained. Such thin film pieces, like the first embodiment, which is cut into several cm 2 ^~ ten cm ² or two tens cm ^2, pieces were wet conditions. Moreover, as for the mass ratio (after drying) of the polyethylene constituting these thin film pieces and the cellulose fibers adhering thereto, “Example 4” is [polyethylene]: [cellulose fibers] = 52: 48, Example 5 ”was [polyethylene]: [cellulose fiber] = 56: 44, and“ Example 6 ”and“ Example 7 ”were [polyethylene]: [cellulose fiber] = 58: 42.
Next, these four types of cellulose fiber-attached polyethylene thin film pieces are kept in a wet state and separately put into the same batch type closed kneading apparatus as in Example 1, and stirred at a high speed to bring the water into a subcritical state. At the same time, the sample materials were kneaded, and the kneading was stopped when the melt flow rate of each sample material showed the value described in Table 2, to prepare four types of cellulose fiber-dispersed polyethylene resin composites.
The evaluation results of each composite material are as shown in Table 2.

  From the results in Table 2, it can be seen that even if the MFR is changed, the characteristics of the obtained composite material are good. However, Example 7 is not excellent in impact strength strength because MFR exceeds 10 because time A is long.

[Test Example 3]
The influence of the time for kneading the cellulose fiber-attached polyethylene thin film pieces with a batch type closed kneader was tested.

In the same manner as in Example 1, a cellulose fiber-attached polyethylene thin film piece was obtained. Such thin film pieces, like in Test Example 1 are cut into several cm 2 ^~ ten cm ² or two dozen cm ^2, pieces were wet conditions. Moreover, the mass ratio (after drying) of the polyethylene which comprises this thin film piece, and the cellulose fiber adhering to it was [polyethylene]: [cellulose fiber] = 56: 44.
Next, this cellulose fiber-attached polyethylene thin film piece is put in the same batch type closed kneading apparatus as in Example 1 in a wet state, and is stirred at a high speed to bring water into a subcritical state and melt-kneaded. Samples of six types of cellulose fiber-dispersed polyethylene resin composites with different kneading times were prepared.
Specifically, after the rotational torque of the rotary shaft of the batch type closed kneading apparatus increases and reaches a maximum value, the torque decreases to 0.7 times the maximum value, and then reaches the minimum value. The starting point is the moment when the torque is reached (when the rate of change in torque reaches 5% per second), the elapsed time (seconds) until the device is stopped is “time A”, and the time A shown in Table 3 is obtained. A cellulose fiber-dispersed polyethylene resin composite was prepared.
The evaluation results of each sample are as shown in Table 3.
Further, FIG. 1 shows the full width at half maximum of the molecular weight pattern in Example 10. FIG. 2 shows the molecular weight of the shoulder portion of the low molecular weight peak in the molecular weight pattern of Example 10. 1 and 2, the horizontal axis represents molecular weight (Molecular Weight), and the vertical axis represents the weight fraction (dW / dlogM) per unit logM. From the results of FIG. 1, the molecular pattern of Example 10 has a half width of 1.54, which satisfies the definition of the present invention. From the results of FIG. 2, Example 10 has a molecular weight of 1.8 × 10 ⁴ at the shoulder of the peak on the low molecular side, which satisfies the definition of the present invention. This improves the compatibility of polyethylene and cellulose fibers, reduces the fine voids at the interface between polyethylene and cellulose fibers, improves the fragility of the interface, and suppresses the decrease in impact resistance and the increase in water absorption rate. It is thought that.

  As shown in Table 3, it can be seen that the MFR of the composite material obtained by adjusting the time A can be changed, and composite materials having different characteristics can be obtained. However, in Example 12, since the time A was long and the MFR exceeded 10, the impact strength was slightly inferior.

[Test Example 4]
The effect of changing the mass ratio between the polyethylene of the cellulose fiber-attached polyethylene thin film and the cellulose fiber attached to the thin film was tested.

Five types of cellulose fiber-attached polyethylene thin film pieces having different mass ratios of polyethylene and cellulose fibers as shown in Table 4 were obtained. These thin film pieces are all as with Example 1, are cut into several cm 2 ^~ ten cm ² or two dozen cm ^2, pieces were wet conditions.
Next, this cellulose fiber-attached polyethylene thin film piece is put in the same batch type closed kneading apparatus as in Example 1 in a wet state, and is stirred at a high speed to bring water into a subcritical state and melt-kneaded. Five types of cellulose fiber-dispersed polyethylene resin composites were prepared.
Table 4 shows the evaluation results of each composite material. In each test example, at the end of kneading by the batch type closed kneader, the rotational torque of the rotating shaft of the batch type closed kneader increases and reaches the maximum value, and then decreases, so that the torque reaches the maximum value. After reaching 0.7 times the value, the starting point is the moment when the minimum value is reached (that is, when the torque change rate becomes 5% per second), and 7 seconds after this starting point.

  From “Comparative Example 2” in Table 4, when the cellulose fiber was larger than the provisions of the present invention with respect to the total mass of the cellulose fiber and polyethylene, the moldability deteriorated and a composite material having the desired shape could not be obtained. . In Comparative Example 2, a polyethylene laminated paper that does not remove any paper portion was cut and water-absorbed was used as a sample material.

[Test Example 5]
The influence of the method (apparatus) for kneading the cellulose fiber-attached polyethylene thin film pieces was tested.

In the same manner as in Example 1, a cellulose fiber-attached polyethylene thin film piece was obtained. Such thin film pieces, like the first embodiment, which is cut into several cm 2 ^~ ten cm ² or two dozen cm ^2, pieces were wet conditions. Moreover, the mass ratio (after drying) of the polyethylene which comprises this thin film piece, and the cellulose fiber adhering to it was [polyethylene]: [cellulose fiber] = 63: 37. In Example 17, when the kneading by the batch type closed kneading apparatus is finished, the rotational torque of the rotating shaft of the batch type closed kneading apparatus rises to reach the maximum value, and then falls, and the torque reaches the maximum value. After reaching 0.7 times the value, the starting point is the moment when the minimum value is reached (that is, when the torque change rate becomes 5% per second), and 7 seconds after this starting point.
As shown in Table 5, the cellulose fiber-attached polyethylene thin film piece was kneaded using a kneader when melt-kneaded in the presence of subcritical water using the batch type closed kneader (Example 17). The evaluation described in Table 5 was performed using the case (Comparative Example 3) and the one obtained by directly molding the thin film piece (Comparative Example 4).
The evaluation results of each composite material are as shown in Table 5.

  From Example 17 in Table 5, the cellulose fiber-dispersed polyethylene resin composite obtained by melt-kneading in the presence of subcritical water as in Example 1 has a moisture content, impact resistance, water absorption, and cellulose fiber dispersion. It turns out that it is excellent in property. In Example 17, the molecular weight pattern of polyethylene satisfies the range set in the present invention. This improves the compatibility of polyethylene and cellulose fibers, reduces the fine voids at the interface between polyethylene and cellulose fibers, improves the fragility of the interface, and suppresses the decrease in impact resistance and the increase in water absorption rate. It is thought that.

  On the other hand, in the case of kneading using a kneader (Comparative Example 3) and in the case where the thin film piece was directly molded (Comparative Example 4), water could not be removed sufficiently. In addition, it is practically difficult to treat the moisture content to 0% using a kneader. Even if the moisture content can be dried to 0%, the consumption shown in Table 5 above is assumed. It consumes several times to several tens of times the amount of power. Moreover, the composite material obtained by the comparative examples 3 and 4 had a high water absorption, and was inferior also to the dispersibility of a cellulose fiber.

  Furthermore, evaluation shown in Table 5 was performed using a commercially available recycled resin recovered by the container recycling method (PE Rich Product manufactured by Green Loop Co., Ltd .: Comparative Example 5). It can be seen that the cellulose-containing thermoplastic resin produced by the production method of the present invention has improved impact resistance after water absorption as compared with a commercially available recycled resin.

[Test Example 6]
The cellulose fiber-attached polyethylene thin film pieces were tested for the effect of volume reduction and solidification before kneading.

In the same manner as in Example 1, a cellulose fiber-attached polyethylene thin film piece was obtained. Such thin film pieces, like the first embodiment, which is cut into several cm 2 ^~ ten cm ² or two dozen cm ^2, pieces were wet conditions. Moreover, the mass ratio (after drying) of the polyethylene which comprises this thin film piece, and the cellulose fiber adhering to it was [polyethylene]: [cellulose fiber] = 63: 37.
Next, prepare the thin film pieces, as shown in Table 6, using the same batch closed kneading apparatus as in Example 1, and melt-kneaded in the presence of subcritical water cellulosic fiber content dispersed polyethylene resin composite (Example 18).
In addition, before putting the cellulose fiber-attached polyethylene thin film pieces into the batch type closed kneading apparatus, a volume reduction solidification machine (manufactured by Okuma Iron Works Co., Ltd., biaxial waste plastic volume reduction solidification machine, model: DP-3N) is used. The volume was reduced and solidified, and then charged into a batch type closed kneader (Example 19).
Further, the cellulose fiber-attached polyethylene thin film piece was put into a twin screw extruder (manufactured by Nippon Steel Works, Ltd., using TEX30) and kneaded (Comparative Example 6).
Moreover, before throwing the thin film piece into a twin screw extruder, it was dried with a dryer set at 80 ° C. until the water content was less than 1% by mass, and then put into a twin screw extruder (Comparative Example 7). .
The evaluation results of each composite material are as shown in Table 6.

From Example 18 of Table 6, the cellulose fiber-dispersed polyethylene resin composite material obtained by melt-kneading in the presence of subcritical water using a batch-type closed kneading apparatus has a water content of 0, The power consumption required for the production was low and the energy efficiency was excellent. Moreover, it turns out that it is excellent in a cellulose dispersibility and water absorption is also low. It can also be seen that in Example 19 in which volume reduction treatment was performed before melt-kneading, the power consumption can be further greatly reduced.
Furthermore, in Examples 18 and 19, the molecular weight pattern of polyethylene satisfied the range set above.
On the other hand, when kneaded by a twin screw extruder, the resulting composite material had a high water content, poor dispersibility of cellulose, and high water absorption. When the kneading method is adopted by a twin screw extruder, the moisture content of the obtained composite material can be set to 0% by mass by subjecting the cellulose fiber-attached polyethylene thin film piece to a drying treatment before kneading. However, in this case, the power consumption increased several times, resulting in poor energy efficiency.

[Test Example 7]
When kneading the cellulose fiber-attached polyethylene thin film pieces, the effect of adding regenerated high density polyethylene (regenerated HDPE) was tested.

In the same manner as in Example 1, a cellulose fiber-attached polyethylene thin film piece was obtained. Such thin film pieces, like the first embodiment, which is cut into several cm 2 ^~ ten cm ² or two dozen cm ^2, pieces were wet conditions. Moreover, the mass ratio (after drying) of the polyethylene which comprises this thin film piece, and the cellulose fiber adhering to it was 63:37.
Next, a predetermined amount of regenerated HDPE shown in Table 7 was added to this thin film piece, and melt-kneaded in the presence of subcritical water using the same batch type closed kneader as in Example 1. Three types of composite materials 20 to 22 were obtained.
Table 7 shows the evaluation results of each composite material.

  From Examples 20 to 22 in Table 7, it can be seen that there is no problem in physical properties even when recycled HDPE is added when kneading the cellulose fiber-attached polyethylene thin film pieces.

Conventionally, after the polyethylene laminated paper such as used beverage containers is treated with a pulper and the paper part is peeled off and removed, the paper components that could not be removed are non-uniformly adhered to the polyethylene resin. In addition, the cellulose fiber-attached polyethylene thin film pieces of various sizes and in a state of absorbing a large amount of water do not have a technology for effectively reusing as a resin composition, so to speak, it is buried as if it is garbage and discarded. It could only be used as fuel. The present invention relates to a technique for treating a cellulose fiber-attached polyethylene thin film piece as it is (without the need for moisture adjustment or the like) and allowing it to be easily reconstituted as a resin, as demonstrated in the above examples. It is an invention.
As described above, the techniques described in Patent Documents 1 and 2 do not perform subcritical processing. Further, since Patent Document 1 is a mold-molded product that uses the same materials but does not perform melt-kneading, the dispersion state of cellulose fibers is completely different from the present invention. The techniques of Patent Documents 2 and 3 merely use a polypropylene resin or a PET resin that has already been reused as a resin material. The technique of Patent Document 3 is a technique for preparing a cellulose fiber source (PPC waste paper) and a resin material source (PET resin), which are finely cut by adjusting moisture before feeding the materials, and mixing and kneading them separately. It is not a technology related to recycling.

Patent Documents 1 to 4 describe a technique in which cellulose fixed on the surface of a thin-film polyethylene film is separated from the surface of the polyethylene by subcritical processing and dispersed in a fiber form in the polyethylene resin. Neither suggested nor suggested. In one embodiment of the present invention, the MFR is adjusted to a predetermined range by controlling the molecular weight distribution by lowering the molecular weight of the polyethylene resin by performing melt-kneading in the presence of subcritical water, and at the same time, the physical properties of the polyethylene resin. Can be maintained within a predetermined range. None of Patent Documents 1 to 4 describes the molecular weight distribution of polyethylene, and neither describes nor suggests controlling the characteristics of the cellulose fiber-dispersed polyethylene resin composite.
As described above, the present invention is a cellulose fiber-dispersed polyethylene resin having uniform physical properties from a cellulose fiber-attached polyethylene thin film piece as a composite of cellulose fiber and polyethylene, in which the size, shape, and adhesion state of cellulose fibers are non-uniform. The present invention relates to a technology that makes it possible to produce a composite material.

Claims (14)

  In the molecular weight pattern obtained by gel permeation chromatography (GPC) measurement, cellulose fibers are dispersed in a polyethylene resin satisfying the relationship of 1.7> full width at half maximum (Log (MH / ML))> 1.3. A cellulose fiber-dispersed polyethylene resin composite material comprising the cellulose fiber-dispersed polyethylene resin composite material, wherein the cellulose fiber-dispersed polyethylene resin composite material comprises 1% by mass or more and less than 50% by mass of cellulose fiber. The water absorption of the cellulose fiber dispersion of polyethylene resin composite satisfies the following equation, cellulose fiber dispersion of polyethylene resin composite material according to claim 1.
[Formula 1] (Water absorption) <(cellulose effective mass ratio) ² × 0.01 The cellulose fiber-dispersed polyethylene resin composite contains 1% by mass or more and less than 10% by mass of cellulose fiber, and the bending strength of the molded product when the cellulose fiber-dispersed polyethylene resin composite is molded is 8 to 20 MPa. The cellulose fiber-dispersed polyethylene resin composite according to 1 or 2. The cellulose fiber-dispersed polyethylene resin composite contains 10% by mass or more and less than 50% by mass of cellulose fiber, and the bending strength of the molded product when the cellulose fiber-dispersed polyethylene resin composite is molded is 15 to 40 MPa. The cellulose fiber-dispersed polyethylene resin composite according to 1 or 2.   The cellulose fiber-dispersed polyethylene resin composite according to any one of claims 1 to 4, wherein a melt flow rate (MFR) at a temperature of 230 ° C and a load of 5 kgf is 0.5 to 10.0 g / 10 min. The cellulose fiber-dispersed polyethylene resin composite according to any one of claims 1 to 5, wherein the polyethylene resin constituting the cellulose fiber-dispersed polyethylene resin composite includes low-density polyethylene. The cellulose fiber-dispersed polyethylene resin according to any one of claims 1 to 6, wherein the polyethylene resin constituting the cellulose fiber-dispersed polyethylene resin composite material includes at least one of linear low-density polyethylene and high-density polyethylene. Composite material.   The cellulose fiber-dispersed polyethylene resin composite according to any one of claims 1 to 7, wherein the moisture content is less than 1% by mass. In the molecular weight pattern of integral display obtained as a result of molecular weight analysis obtained by gel permeation chromatography (GPC) measurement, the shoulder of the peak on the low molecular side where the peak shape is flattened is 10 ⁴ to 4 × 10 ⁴ . The cellulose fiber-dispersed polyethylene resin composite according to claim 1, wherein cellulose fibers containing cellulose in a mass ratio smaller than the mass of the polyethylene resin are dispersed in a polyethylene resin present in the range. A test piece having a length of 100 mm, a width of 100 mm, and a thickness of 1 mm was prepared using the cellulose fiber-dispersed polyethylene resin composite, and the water absorption after being immersed in water at 23 ° C. for 20 days was 0.1 to 10%. In addition, the impact resistance of a test piece having a length of 80 mm, a width of 10 mm, and a thickness of 4 mm produced using the composite material is higher after being immersed in water at 23 ° C. than for 20 days. The cellulose fiber-dispersed polyethylene resin composite material according to any one of 1 to 9.   The cellulose fiber-dispersed polyethylene resin composite according to any one of claims 1 to 10, which is obtained using a cellulose fiber-attached polyethylene thin film piece to which cellulose fibers are attached as a raw material.   The cellulose fiber-dispersed polyethylene resin composite according to any one of claims 1 to 11, wherein the shape is a pellet.   The molded object using the cellulose fiber dispersion | distribution polyethylene resin composite material of any one of Claims 1-12. The pellet which consists of a molded object of Claim 13, or its cutting piece.

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