JPH0890521A - Low-density board - Google Patents

Abstract

PURPOSE: To provide a method for stably and easily manufacturing a low-density board made of wastepaper and having excellent cushioning properties. CONSTITUTION: A low-density board is obtained by the steps of mixing wastepaper pulp fibrillated in dry system with thermoplastic resin fine fiber in dry system, then heating them at a temperature of the melting point or higher of the fine fiber thereby to melt the part of all of the fine fiber, and adhering the pieces of the wastepaper to each other. The wastepaper has necessarily a length weighted average length of 0.5m or more and is preferably that the ratio of the wastepaper pulp in which the fiber length compared in terms of the number is 0.4mm or less is 90% or less of the entire wastepaper pulp and the ratio of the wastepaper pulp of 1mm or more is 30% or more. The fine fiber is preferably made of pulplike multi-branched fiber made of polyolefin resin, and weighted average fiber length is preferably in a range of 0.2-15mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low density board mainly made of waste paper, and more specifically, a cushioning material, a heat insulating material, a heat insulating material and the like used for the purpose of preventing damage, damage and crushing of articles. The present invention relates to a low-density board that can be widely used as.

[0002]

2. Description of the Related Art In recent years, a large amount of waste paper discharged from factories, shops, offices, general households, etc. has been urgently required to be expanded in its fields of use and methods from the viewpoint of environmental protection and effective use of resources. As a method of using waste paper as a raw material for the cushioning material, waste paper pulp prepared by disintegrating waste paper with water,
A so-called molding method is widely used in which a pack-shaped cushioning material for preventing the destruction of eggs is obtained by introducing it into a mold and drying it. However, since the used paper pulp cushioning material obtained by this method is formed by drying used paper pulp disintegrated with water, a strong hydrogen bond is formed between the pulps, and the apparent bulk is high due to the shape of the mold. On the other hand, since the obtained base material has a high true specific gravity and is hard, the buffer performance was insufficient. Further, since the base material itself is hard, it cannot be used as a sheet-shaped cushioning material. Further, there is a problem that it is necessary to make an expensive mold according to the application.

As a method for solving these problems, for example, Japanese Laid-Open Patent Publication No. 56-41142 discloses waste paper pulp and fiber length.
After mixing fibers of 10 mm or more and thermoplastic resin powder by dry method,
A heat molded pallet is disclosed. Using this method, it is possible to produce a bulky sheet because there are almost no hydrogen bonds between the pulps. However,
Since the thermoplastic resin powder is used as a binder, the sheet after heat molding becomes hard, and not only the buffer performance is poor, but also when the thermosetting resin powder such as phenol resin is mixed with waste paper pulp or fiber, Alternatively, in the subsequent manufacturing process, there is a problem that the working environment is deteriorated, for example, the thermosetting resin powder is scattered and further phenol and formalin are generated during the heat treatment.

On the other hand, JP-B-52-20588 discloses that 1 to 50% by weight of synthetic pulp is added to used paper such as cardboard and paperboard, and the pulp is dried in a dry state using a defibrating machine such as a dry refiner. After mixing and defibrating, a method of depositing on a formation wire and then producing a flat sheet by hot pressing is disclosed. If this method is used, water does not exist at the stage of forming the sheet, so there is no problem that the sheet becomes hard due to the formation of hydrogen bonds and the density of the sheet increases, and moreover, thermosetting properties such as phenol resin as an adhesive Since no resin powder is used, the working environment is not deteriorated due to the scattering of the thermosetting resin powder during production and the phenol and formalin generated during the heat treatment. However, since waste fiber and synthetic pulp are mixed and defibrated by a dry refiner, the temperature inside the refiner causes the synthetic pulp to melt, forming waste paper pulp flocs, and the molten synthetic pulp adhering to the inside of the refiner. However, because the fiber length distribution of the used paper pulp used is not within a specific range, the work environment is deteriorated due to a large amount of powdered fine pulp fiber components, and the strength and moldability due to the lack of long fiber components in the pulp. Due to a problem such as a shortage, it was not possible to stably produce a high-quality low-density board. Furthermore, since synthetic pulp having a specific fiber length is not used, it is difficult to stably produce a waste paper sheet having both strength and cushioning properties that can be practically used as cushioning materials.

[0005]

The object of the present invention is to use recycled paper as the main raw material so that it can be reused as a raw material after use, and even if it is discarded, it will be decomposed by microorganisms by being buried in the soil, An object of the present invention is to provide an environment-friendly method for producing a low-density board that does not generate a toxic gas even when incinerated. Furthermore, there is no hardness of the board due to the use of water in the manufacturing process, there is almost no deterioration of the environment due to the scattering of binder and paper powder during manufacturing, and harmful substances such as phenol and formalin from the binder used. Effective use of waste paper, cushioning,
An object of the present invention is to provide a bulky low-density board which has excellent heat insulation properties, good strength and thermoformability, and is easy to manufacture.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the present situation, and as a result, used paper pulp defibrated by a method of defibrating used paper in the air without using water (dry method). And a fine fiber of a thermoplastic resin, a fiber assembly obtained by dry-mixing, by heating at a temperature equal to or higher than the melting point of the thermoplastic resin, to dissolve a part or all of the thermoplastic resin fine fiber, In the method of combining waste paper pulp to obtain a low-density board, the length-weighted average length after defibration (length
-By using waste paper pulp with a weighted average length of 0.5 mm or more, the above problems can be solved. Furthermore, the ratio of waste paper pulp with a fiber length of 0.4 mm or less is 90% or less of waste paper pulp,
By using waste paper pulp with a fiber length of 1 mm or more, the ratio of waste paper pulp is 3% or more of the total waste paper pulp,
The present invention has been completed by finding that it is possible to easily obtain a low-density board having excellent buffering properties, heat insulating properties, and the like.

The used paper used in the present invention is not particularly limited as long as it is formed mainly of pulp fibers, and for example, newspaper, magazine, book, cardboard, paperboard,
Used paper such as high-quality paper, leaflets, pamphlets, and packaging paper can be used. The water content of waste paper before defibration is 2-1
It is preferably in the range of 5%, preferably 2.5-12%.
If the water content of waste paper is less than 2%, the sheet will become stiff,
It is not preferable because the fine pulp component unsuitable for the production of the low density board increases during the defibration in the dry method. Furthermore, the low water content is not preferable because static electricity is significantly charged and workability is deteriorated. Conversely, if the water content of waste paper exceeds 15%, dry defibration will be insufficient, and not only paper pieces and pulp flocs will tend to be present, but trouble will also occur during the heat treatment process during the production of low-density boards. It is not preferable because it causes the problem. In the present invention, waste paper is defibrated in air without using water. As a defibration method, a normal dry pulp manufacturing apparatus, a dry refiner, or the like can be used. In this case, the used paper may be roughly crushed in advance before defibration with a cutting device such as a shredder or a crushing device.

The first feature of the present invention is that the length-weighted averag of dry defibrated pulp fibers is
(e length) used paper pulp having a specific numerical value or more, and fine fibers of a thermoplastic resin are dry-mixed, and a fiber assembly is heated at a temperature equal to or higher than the melting point of the thermoplastic resin. The purpose is to dissolve some or all of the fibers and bond the waste paper pulps together.

The second feature of the present invention is to use waste paper pulp whose fiber length distribution compared by the number of fibers is controlled within a specific range. That is, a length-weighted average length after defibration in a dry method is 0.5 mm or more, preferably 0.6 mm or more of waste paper pulp, and a fine fiber of a thermoplastic resin are mixed in a dry method to obtain a fiber assembly. It is characterized by heating at a temperature above the melting point of the plastic resin, melting some or all of the thermoplastic resin fine fibers, and binding waste paper pulp to each other.Furthermore, comparing the numbers, the fiber length is 0.4 mm or less. 90% or less of the total used paper pulp, preferably 85%
It is characterized in that used paper pulp having a ratio of used paper pulp of 1 mm or more is 3%, preferably 4%, most preferably 5% or more of the total used paper pulp.

If the length-weighted average length is shorter than 0.5 mm,
The surface strength of the produced low-density board is reduced, the pulp powder is liable to be detached due to surface friction, and cracks and the like of the base material are likely to occur when performing bending or the like, which is not suitable.
Also, when the ratio of waste paper pulp with a fiber length of 0.4 mm or less compared with the number of waste fibers is more than 90% of the total waste paper pulp, the surface strength of the prepared low density board decreases and the surface friction causes the pulp powder to be removed. Separation is likely to occur, and cracking of the substrate is likely to occur when bending is further performed, which is not preferable.
Conversely, if the ratio of waste paper pulp with a fiber length of 1 mm or less is less than 3% of the total waste paper pulp compared with the number of sheets, the sheet strength will decrease, and cracking of the base material etc. Is likely to occur and is not suitable.

The length-weighted average fiber length of the pulp is the sum of the squares of Li, where Li is the length of each fiber in the pulp (i = 1, 2, 3 ... n, n is the number of fibers). Is the value obtained by dividing the sum of Li. The length-weighted average fiber length of waste paper pulp is calculated by removing unbroken paper pieces with an area of 1 mm ² or more from waste paper pulp.
It is possible to measure using KAYANI fiber length measuring machine FS-2000 manufactured by Valmet Automation.

The fine fibers of the thermoplastic resin that can be used in the present invention include polyolefin resins such as polyethylene and polypropylene, polyamide resins such as nylon, thermoplastic resins such as polyester resins, and copolymers of these resins. Processed into short fiber, or 2 of the above resins
This is a so-called side-by-side type or sheath core type conjugate fiber obtained by spinning at least one kind of fiber at the same time, and it is possible to use one or more kinds of these. Particularly, pulp-like multi-branched fibers manufactured from polyolefin resins such as polyethylene and polypropylene are preferable. The weight average fiber length of the fine fibers of the thermoplastic resin is in the range of 0.2 to 15 mm, preferably 0.3 to 5 mm. If the fiber length is less than 0.2 mm, the strength of the produced low-density board decreases, which is not preferable. On the other hand, if the fiber length exceeds 15 mm, the thermoplastic resin fine fibers are not evenly dispersed in the pulp, which is not preferable. The weight average fiber length of fine fibers of the thermoplastic resin can be measured by the method shown in TAPPI T233 using the apparatus shown in JIS P8207.

The absolutely dry weight mixing ratio of waste paper pulp and thermoplastic fine fiber is as follows: waste paper pulp / fine fiber = 95-60 / 5
-40, preferably 90-70 / 10-30. If the blending ratio of the thermoplastic fiber is less than 5%, the strength of the low density board prepared is weak, and if the blending ratio exceeds 40%, the board is void.
It is not preferable because it becomes too hard.

In the present invention, a low density product which is a product is
In order to improve the strength and moldability of the pulp, it is possible to mix softwood pulp with long fibers in the waste paper pulp.
The softwood pulp used is not particularly limited,
For example, chemical pulp obtained by boiling softwood by Kraft method, soda method, polysulfide method or the like, or mechanical pulp such as ground pulp, thermomechanical pulp, unbleached or bleached, alone or mixed. Can be used.

Softwood pulp has a length weighted average fiber length of 0.
7 mm or more, preferably 1 mm or more, and the ratio of the softwood pulp having a fiber length of 0.6 mm or less compared by the number is 80% or less, preferably 75% or less of the total softwood pulp, and the fiber length is 1.5 mm or more. It is necessary to use a softwood pulp having a ratio of 5% or more, preferably 10% or more, of the total softwood pulp. When a softwood pulp having a long fiber portion out of this range is used, the strength is not improved so much. The blending ratio of softwood pulp to waste paper pulp is
It is made 5% or more and preferably 10% or more. Mixing ratio is 5
If it is less than%, the strength is not sufficiently improved. Like the waste paper pulp, the softwood pulp is defibrated by a dry method with a water content of 2 to 15% and mixed with the waste paper pulp in a dry state.

A fiber assembly of waste paper pulp and thermoplastic fine fibers, which are uniformly mixed, is laminated on a moving belt-shaped carrier for conveyance and transferred to a heat treatment apparatus. In this case, the mixed fiber laminate of waste paper pulp and thermoplastic fine fibers may be sandwiched from above and below by a breathable carrier support, or may be carried by being sandwiched by a metal belt or the like having high thermal conductivity. The heating device is not particularly limited as long as it can melt the thermoplastic fine fibers in the mixed fiber laminate, and for example, a hot air oven or a microwave can be used. In the case of a hot-blast stove, it is preferable to suck the waste paper pulp or the heat-resistant fine fibers from below the transport support in order to prevent the waste paper pulp and the thermal fine fibers from scattering. The heating temperature of the heating device is preferably 260 ° C. or lower. If the heating temperature exceeds 260 ° C,
There is a risk of carbonization and ignition of pulp fibers, which is not preferable.

The mixed fiber laminate of waste paper pulp and thermoplastic resin fine fibers heated to a temperature not lower than the melting point of the thermoplastic resin fine fibers by the heating device is added to a press roll or the like in the heating device or after leaving the heating device. It can be pressed by a pressure device to obtain a low density board of desired thickness and density. In this case, the pressure treatment may be performed both inside the heating device and after exiting the heating device. The density of the low-density board after heating and pressure molding is preferably in the range of 0.01 to 0.4 g / cm ³ , preferably 0.05 to 0.3 g / cm ³ . If the density of the manufactured low-density board is less than 0.01 g / cm ³ , the strength of the board is reduced, which is not preferable.
On the contrary, if the density of the board is larger than 0.4 g / cm ³ , the manufactured board becomes too hard and the buffering performance is lowered, which is not preferable.

On the other hand, a low-density board can be obtained by hot pressing mixed fibers of waste paper pulp and thermoplastic fine fibers with a press having a heating function, as in the above method. That is, the mixed fibers of waste paper pulp and thermoplastic fine fibers that are uniformly mixed are placed on a press plate on the sample holding side (lower side) of the hot press, in which a spacer having the same thickness as the desired low-density board is placed. A low-density board can be produced in the same manner as in the above method by stacking layers on top of each other and heat-pressing at a temperature equal to or higher than the melting point of the thermal fine fibers. When there is a return of the thickness of the low density board after the hot press is released, the thickness of the spacer can be reduced to obtain the desired thickness of the low density board. The heating temperature of the hot press is preferably 260 ° C or lower. If the heating temperature exceeds 260 ° C, the pulp fibers may be carbonized or ignited, which is not preferable. The pressure at the time of press molding is not particularly limited as long as it can compress the laminated body of mixed fibers to the thickness of the spacer. That is, even if the pressure is increased, the presence of the spacer does not cause the laminated body of the mixed fibers to be crushed below the thickness of the spacer.

Since the low-density board according to the present invention uses waste paper as its main raw material, waste can be effectively used, and the board after use can be defibrated again and used as a raw material for the low-density board. Furthermore, even when it is discarded, it can be decomposed by microorganisms by burying it in the soil, and even when it is incinerated, it is a very environmentally friendly material that does not generate toxic gas. According to the present invention, a low-density board having such advantages can be stably and easily manufactured without causing deterioration of the work environment due to the scattering of the binder in the manufacturing process and without the generation of harmful substances such as phenol and formalin during the manufacturing. Can be obtained, and various processes such as thermoforming, punching, and laminating can be performed as necessary, and the product can be used as a cushioning material, a heat insulating material, a heat insulating material and the like.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the following examples, all parts and% are parts by weight and% by weight, unless otherwise specified. Example 1 A newspaper crusher with a water content of 6% was used as a pulp crusher (Zuiko Tekko Co., Ltd.).
Co., Ltd., TYPE FR-160), and then pulverized by a dry method using a pulp crusher (Type P-270, manufactured by Mizuko Tekko KK).
Waste paper pulp was obtained. The length-weighted average length of the obtained waste paper pulp was 1.44 mm, and the fiber length was 0.4 when compared by the number.
The ratio of used paper pulp of mm or less is 52.5% of all used paper pulp.
The ratio of waste paper pulp of 1 mm or more was 20.1% of the total waste paper pulp. The obtained waste paper pulp and dry defibrated and dried multi-branched synthetic pulp (trade name SWP, E990, manufactured by Mitsui Petrochemical Co., Ltd.) are blended at a ratio of waste paper pulp / synthetic pulp = 80/20. Then, the mixture was uniformly mixed with a mixer to obtain a mixed fiber. The melting point of synthetic pulp is 130 ° C,
The average fiber length was 2.1 mm and the water content was 5%. Next, a heat press device (manufactured by Toyo Seiki Seisakusho Co., Ltd., Lab Press 30T) in which a spacer having a height of 10 mm is placed on the mixed fiber.
10 kg at a pressure of 20 kg / cm ² and a temperature of 170 ° C.
Hold for a minute to obtain a low density board. The density of the obtained low-density board was 0.15 g / cm ³ and the basis weight was 1500 g / m ² .

Example 2 Waste newspaper with a water content of 8% was crushed by a pulp crusher (Zuiko Tekko Co., Ltd.).
Co., Ltd., TYPE FR-160), and then pulverized by a dry method using a pulp crusher (Type P-270, manufactured by Mizuko Tekko KK).
Waste paper pulp was obtained. The length-weighted average length of the obtained waste paper pulp was 0.80 mm, and the fiber length was 0.4 when compared by the number.
The ratio of used paper pulp of mm or less is 84% of the total used paper pulp.
The ratio of waste paper pulp of 1 mm or more was 4.0% of all waste paper pulp. The obtained waste paper pulp and synthetic pulp defibrated and dried by a dry method (manufactured by Mitsui Petrochemical Co., Ltd.,
Product name SWP, E780), recycled paper pulp / synthetic pulp = 85 /
It was mixed in a ratio of 15 and uniformly mixed with a mixer to obtain a mixed fiber. The melting point of the synthetic pulp was 130 ° C., the average fiber length was 1.6 mm, and the water content was 5%. Next, the mixed fibers are laminated between a heat press device (Labo Press 30T, manufactured by Toyo Seiki Seisakusho Co., Ltd.) with a spacer having a height of 20 mm, and the pressure is 10 kg / cm 2 and the temperature is 170 ° C. for 10 minutes. Hold and
A low density board was obtained. The density of the obtained low density board is 0.
It was 10 g / cm ³ and the basis weight was 2000 g / m ² .

Example 3 Waste newspaper with a water content of 5% was crushed by a pulp crusher (Zuiko Tekko Co., Ltd.).
Co., Ltd., TYPE FR-160), and then pulverized by a dry method using a pulp crusher (Type P-270, manufactured by Mizuko Tekko KK).
Waste paper pulp was obtained. The length-weighted average length of the obtained waste paper pulp was 1.80 mm, and the fiber length was 0.4 when compared by the number.
The ratio of used paper pulp of mm or less is 43.6% of the total used paper pulp.
The ratio of waste paper pulp of 1 mm or more was 28.1% or more of the total waste paper pulp. The obtained waste paper pulp and synthetic pulp defibrated and dried by the dry method (Mitsui Petrochemical Co., Ltd.)
Manufactured, trade name SWP, E780), recycled paper pulp / synthetic pulp =
They were mixed in a ratio of 90/10 and uniformly mixed with a mixer to obtain mixed fibers. The melting point of the synthetic pulp was 130 ° C, the average fiber length was 1.6 mm, and the water content was 5%. Next, the mixed fiber was laminated between a heat press device (manufactured by Toyo Seiki Seisakusho Co., Ltd., Lab Press 30T) on which a spacer having a height of 10 m was placed, and the pressure was 20 kg / cm ² at a temperature of 170 ° C. Hold for a minute to obtain a low density board. The density of the obtained low-density board was 0.25 g / cm ³ , and the basis weight was 2500 g / m ² .

Example 4 Waste newspaper with a water content of 6% was crushed by a pulp crusher (Zuiko Tekko Co., Ltd.).
Co., Ltd., TYPE FR-160), and then pulverized by a dry method using a pulp crusher (Type P-270, manufactured by Mizuko Tekko KK).
Waste paper pulp was obtained. The length-weighted average length of the obtained waste paper pulp was 1.44 mm, and the fiber length was 0.4 when compared by the number.
The ratio of used paper pulp of mm or less is 52.5% of all used paper pulp.
The ratio of waste paper pulp of 1 mm or more is 2 of that of paper pulp.
It was 0.1%. Mix the obtained waste paper pulp with the dry defibrated and dried synthetic pulp (manufactured by Mitsui Petrochemical Co., Ltd., trade name SWP, E380) in the ratio of waste paper pulp / synthetic pulp = 80/20, and mix. To obtain a mixed fiber. The melting point of synthetic pulp is 130 ° C and the average fiber length is 0.7.
mm and water content was 5%. Next, the mixed fiber
Heat press machine with spacer of 30mm height (Co., Ltd.)
Toyo Seiki Seisakusho, Lab Press 30T)
A pressure of kg / cm ² and a temperature of 170 ° C. were maintained for 15 minutes to obtain a low density board. The density of the obtained low density board is 0.15
It was g / cm ³ and the basis weight was 4500 g / m ² .

Example 5 Waste newspaper with a water content of 6% was crushed by a pulp crusher (Zuiko Tekko Co., Ltd.).
Co., Ltd., TYPE FR-160), and then pulverized by a dry method using a pulp crusher (Type P-270, manufactured by Mizuko Tekko KK).
Waste paper pulp was obtained. The length-weighted average length of the obtained waste paper pulp was 1.44 mm, and the fiber length was 0.4 when compared by the number.
The ratio of used paper pulp of mm or less is 52.5% of all used paper pulp.
The ratio of waste paper pulp of 1 mm or more was 20.1% of all waste paper pulp. The obtained waste paper pulp and synthetic pulp defibrated and dried by a dry method (manufactured by Mitsui Petrochemical Co., Ltd.,
Product name SWP, E990), recycled paper pulp / synthetic pulp = 80 /
It was mixed in a ratio of 20 and uniformly mixed with a mixer to obtain a mixed fiber. The melting point of the synthetic pulp was 130 ° C, the average fiber length was 2.1 mm, and the water content was 5%. Next, the mixed fiber was laminated between a heat press device (manufactured by Toyo Seiki Seisakusho Co., Ltd., Labo Press 30T) having a spacer with a height of 30 mm, and a pressure of 10 kg / cm ² and a temperature of 170 ° C. were applied for 15 minutes. Hold for a minute to obtain a low density board. The obtained low-density board had a density of 0.07 g / cm ³ and a basis weight of 2400 g / m ² .

Example 6 A high-quality waste paper having a water content of 4% was crushed with a pulp crusher (Zuiko Tekko Co., Ltd.).
Manufactured by TYPE FR-160), and then crushed by a dry method using a pulp crusher (Type P-270 manufactured by Mizuko Tekko KK).
Waste paper pulp was obtained. The length-weighted average length of the obtained waste paper pulp was 2.24 mm, and the fiber length was 0.4 when compared by the number.
The ratio of used paper pulp of mm or less is 38.8% of all used paper pulp.
%, And the ratio of waste paper pulp of 1 mm or more was 32.4% of all waste paper pulp. The obtained waste paper pulp and synthetic pulp defibrated and dried by the dry method (Mitsui Petrochemical Co., Ltd.)
Manufactured, trade name SWP, E990), recycled paper pulp / synthetic pulp =
It was blended in a ratio of 80/20 and uniformly mixed with a mixer to obtain a mixed fiber. The melting point of the synthetic pulp was 130 ° C, the average fiber length was 2.1 mm, and the water content was 5%. Next, the mixed fibers were laminated between a heat press device (Labo Press 30T, manufactured by Toyo Seiki Seisakusho, Ltd.) with a spacer having a height of 10 mm, and pressure was 20 kg / cm ² at a temperature of 170 ° C. for 10 minutes. Hold for a minute to obtain a low density board. The density of the obtained low-density board was 0.15 g / cm ³ and the basis weight was 1500 g / m ² .

Example 7 Waste newspaper with a water content of 6% was crushed with a pulp crusher (Zuiko Tekko Co., Ltd.).
Manufactured by TYPE FR-160), and then crushed by a dry method using a pulp crusher (Type P-270 manufactured by Mizuko Tekko KK).
Waste paper pulp was obtained. The length-weighted average length of the obtained waste paper pulp was 1.44 mm, and the fiber length was 0.4 when compared by the number.
The ratio of used paper pulp below mm is 52.5% of all used paper pulp.
%, And the ratio of waste paper pulp of 1 mm or more was 20.1% of all waste paper pulp. The obtained waste paper pulp and synthetic pulp defibrated and dried by the dry method (Mitsui Petrochemical Co., Ltd.)
Manufactured, trade name SWP, E990), recycled paper pulp / synthetic pulp =
It was blended in a ratio of 80/20 and uniformly mixed with a mixer to obtain a mixed fiber. The melting point of the synthetic pulp was 130 ° C, the average fiber length was 2.1 mm, and the water content was 5%. Next, the mixed fiber was laminated on a conveyor belt made of a porous material sucked from below and introduced into a hot air dryer. The dryer temperature was 180 ° C. Then, the heat-treated mixed fiber laminate was molded with a press roll installed at the exit of the dryer to a density of 0.15 g / cm ^3, and a low-density board with a thickness of 10 mm and a basis weight of 1500 g / m ² was obtained. It was

Example 8 Waste newspaper with a water content of 6% was used for a pulp crusher (Zuiko Tekko Co., Ltd.).
Manufactured by TYPE FR-160), and then crushed by a dry method using a pulp crusher (Type P-270 manufactured by Mizuko Tekko KK).
Waste paper pulp was obtained. The length-weighted average length of the obtained waste paper pulp was 1.44 mm, and the fiber length was 0.4 when compared by the number.
The ratio of used paper pulp below mm is 52.5% of all used paper pulp.
%, And the ratio of waste paper pulp of 1 mm or more was 20.1% of all waste paper pulp. The obtained waste paper pulp and the synthetic pulp that was defibrated and dried by the dry method (Mitsui Petrochemical 8 Co., Ltd. 9
Manufactured by SWP, E990) and blended at a ratio of waste paper pulp / synthetic pulp = 80/20 and uniformly mixed with a mixer to obtain a mixed fiber. The melting point of the synthetic pulp was 130 ° C, the average fiber length was 2.1 mm, and the water content was 5%. Next, the mixed fiber was introduced into a commercially available microwave oven, irradiated with a microwave of 2450 MHz for 60 seconds, taken out from the microwave oven, and pressure-molded with a press roll to a density of 0.15 g / cm ³ , A low-density board having a thickness of 10 mm and a basis weight of 1500 g / cm ² was obtained.

Example 9 Waste newspaper and softwood bleached kraft pulp (hereinafter NBKP)
Sheet), and a pulp crusher
(Zuiko Tekko Co., Ltd., TYPE P-160)
Using a lup crusher (Type P-270 manufactured by Zuiko Tekko Co., Ltd.)
It was defibrated by a dry method to obtain waste paper pulp and NBKP. Got
The length-weighted average fiber length of waste paper pulp is 1.07 mm.
Proportion of waste paper pulp with a fiber length of 0.4 mm or less compared by number
Is 57.5% of the total waste paper pulp, and the fiber length is 1 mm or more.
The percentage of waste paper pulp was 19.3% of the total waste paper pulp. Profit
The length-weighted average fiber length of NBKP was 2.69 mm.
The ratio of NBKP with a fiber length of 0.6 mm or less compared by number is all NBK
59.4% of P and the ratio of NBKP with a fiber length of 1.5 mm or more is all
It was 23.3% of NBKP. The obtained waste paper pulp and NBKP are recycled
Paper pulp / NBKP = 45/55 blended and length weighted
A mixed pulp having an average fiber length of 1.96 mm was obtained. This mixed pal
And dry-defibrated multi-branched synthetic pulp (Mitsui Petrochemical
(Trade name SWP, E780) manufactured by K.K.
Mix at a ratio of 80/20 and mix evenly with a mixer.
To obtain a mixed fiber body. The melting point of synthetic pulp is 130 ℃,
The volume average fiber length was 1.6 mm. Next, the mixed fiber body is mixed with 8
Heat press machine with spacer of mm height (Co., Ltd.)
Layered between Toyo Seiki Seisakusho, Lab Press 30T) 10
kg / cm²Hold at 170 ℃ for 10 minutes,
A low density board was obtained. Board density is 0.15 g / cm ³ And
And the basis weight is 1200 g / m²Met.

Example 10 The recycled paper pulp obtained in Example 9 and NBKP were mixed in a ratio of 70/30 to form a mixed pulp having a length weighted average fiber length of 1.56 mm, and the mixed pulp and the synthetic pulp were 80/20. The low-density board was obtained by treating the fiber mixture obtained by blending with No. 1 in the same manner as in Example 9.

Example 11 The used paper pulp obtained in Example 9 and NBKP were mixed in a ratio of 90/10 to form a mixed pulp having a length weighted average fiber length of 1.07 mm, and the mixed pulp and the synthetic pulp were 80/20. The low-density board was obtained by treating the fiber mixture obtained by blending with No. 1 in the same manner as in Example 9.

Comparative Example 1 The length-weighted average length was 0.31 mm, and the numbers were compared.
The ratio of pulp with a fiber length of 0.4 mm or less is 95.1% of the total pulp.
%, And the ratio of pulp of 1 mm or more was 1.2% of the total waste paper pulp, except that the waste paper pulp was used, the operation of Example 1 was repeated to obtain a low density board.

Comparative Example 2 The length-weighted average length was 0.40 mm, and the numbers were compared.
The ratio of pulp with a fiber length of 0.4 mm or less is 92.1% of the total pulp.
%, And the ratio of pulp of 1 mm or more was 2.6% of the total waste paper pulp.
The above operation was repeated to obtain a low density board.

Comparative Example 3 Newspaper waste paper having a water content of 19% was crushed by a pulp crusher (Zuiko Tekko Co., Ltd.).
Manufactured by TYPE FR-160) and then crushed by dry method using a pulp crusher (Type P-270, manufactured by Zuiko Iron Works Co., Ltd.). A large number of pieces of paper remained in a lump form, and no waste paper pulp capable of producing a low-density board was obtained.

Comparative Example 4 Newspaper waste paper having a water content of 1.4% was crushed by a pulp crusher (Zuiko Tekko Co., Ltd.).
Made by TYPE FR-160) and then crushed by dry method using a pulp crusher (TYPE P-270, manufactured by Zuiko Iron Works Co., Ltd.). The workability was remarkably deteriorated due to the scattering of pulp, adhesion to the defibration device, discharge, etc., so the subsequent tests were stopped.

Comparative Example 5 Except that the waste paper pulp used in Comparative Example 2 was used and synthetic pulp having a weight average fiber length of 0.1 mm (manufactured by Mitsui Petrochemical Co., Ltd., trade name SWP, ESS5) was used as the synthetic pulp. The operation of Example 1 was repeated to obtain a low density board.

Comparative Example 6 The procedure of Example 1 was repeated except that the synthetic pulp was not used and the phenolic resin fine powder was used instead of the synthetic pulp, but the dispersion of the phenolic resin powder and the odors of phenol and formalin were observed. However, the production of the low density board was stopped.

Comparative Example 7 Using the waste paper pulp used in Comparative Example 2, the mixing ratio of the waste paper pulp and the synthetic pulp was as follows: waste paper pulp / synthetic pulp = 50 /
The operation of Example 1 was repeated except that the amount was changed to 50. However, the heating and pressurizing treatment by a hot press caused a large amount of synthetic pulp to dissolve, resulting in a non-uniform and rough surface.
The obtained low-density board also had a density gradient in the thickness direction and was harder, so it could not be used as a cushioning material.

Comparative Example 8 The waste paper pulp used in Comparative Example 2 and a synthetic pulp defibrated by a dry method and dried (manufactured by Mitsui Petrochemical Co., Ltd., trade name SW
P and E990) were blended at a ratio of waste paper pulp / synthetic pulp = 80/20 and uniformly mixed by a mixer to obtain a mixed fiber.
The melting point of the synthetic pulp was 130 ° C., the weight average fiber length was 2.1 mm, and the water content was 5%.

Next, the mixed fiber was laminated between a hot press machine (Labo Press 30T, manufactured by Toyo Seiki Seisakusho Co., Ltd.) with a spacer having a height of 4 mm, and a pressure of 50 kg / cm ² was applied for 17 minutes.
The board was obtained by holding at a temperature of 0 ° C. for 15 minutes. The obtained board had a density of 0.6 g / cm ³ and a basis weight of 2400 g / m ^2.
Met. The sheets obtained in Examples 1 to 11 and Comparative Examples 1 to 8 were tested by the following test method to evaluate their quality.
The manufacturing conditions are shown in Table 1.

[0040]

[Table 1] The evaluation results are shown in Table 2.

[0041]

[Table 2]

Test method (1) Length-average weighted length and fiber length distribution of waste paper pulp: Measured using a Kayaney fiber length measuring machine (FS-2000) manufactured by Valmet Automation. (2) Weight average fiber length of heat-sensitive fine fibers: measured by the method shown in TAPPI T233 using the device shown in JIS P8207. (3) Basis weight: measured by the method shown in JIS P8126. (4) Density: Measured using the method shown in JIS P8118. (5) Tensile strength: Measured using the method shown in JIS P8113. (6) L-shaped moldability: The sample was bent and sandwiched between two L-shaped metal fittings, fixed with a Sayako vise, and held at 170 ° C for 10 minutes. evaluated. 5 ... Very good with no return after molding or cracks in the bent portion. 4 ... Good moldability. 3 ... Moldability is normal. 2. There is a return after molding, and cracks are also noticeable. 1 ... There is no moldability at all.

(7) Surface property: The surface property of the produced board was evaluated functionally. The evaluation was carried out in the following five stages. 5: The surface property is extremely good. 4 ... Good surface property. 3 ... The surface property is normal. 2 ... The surface is rough and the fibers often fall off. 1 ... The surface is extremely defective. (8) Board moldability: Whether or not low density boards can be manufactured
The grade was evaluated. ○: Boards are easy to manufacture. △: Making a board is a little difficult. × ・ ・ ・ The board cannot be manufactured. (9) Board buffering property: The buffering performance of the low density board was evaluated by sensory evaluation according to the following five grades. 5 ... Very good buffering property. 4 ... Good buffering property. 3 ... Buffering property is normal. 2 ... Inferior in buffer property. 1 ... The buffering property is extremely poor.

As is clear from Tables 1 and 2, comparing Examples 1 to 11 with Comparative Examples 1 to 8, Examples 1 to 1 are compared.
In No. 1, a good low density board was easily obtained. On the other hand, in Comparative Example 1, since the average fiber length of the waste paper pulp is short and the ratio of pulp having a fiber length of 0.4 mm or less is high, a large amount of fine pulp powder is scattered at the time of making the board, and the working environment is extremely poor. Moreover, the strength and surface properties of the obtained board were inferior. Also in Comparative Example 2, the fiber length is 0.4 m.
Since the ratio of pulp of m or less was high, there was the same problem as in Comparative Example 1. Further, in Comparative Example 3, since waste paper having a high water content was defibrated, many pieces of wet paper remained in a lump after defibration, and waste paper pulp capable of producing a low-density board was not obtained. Is because the water content of the waste paper is too low, the electrostatic charge on the disentangled waste paper pulp is remarkable,
The workability was significantly reduced due to the scattering of pulp, the adhesion to the defibration device, the discharge, and the like. Further, in Comparative Example 5, the strength of the manufactured low-density board was significantly reduced because the fiber length of the thermosetting resin fine fibers used was too short. In Comparative Example 6, instead of the thermosetting resin fine fibers, a phenol resin was used. Since the fine powder was used, the workability was significantly reduced due to the scattering problems of the phenol resin, the strong phenol odor, and the formalin odor. Further, in Comparative Example 7, since the blending ratio of the thermophilic fine fibers is high, the surface property is poor, the hardness is poor, and the buffering performance is also poor. In Comparative Example 8, since the density of the produced board is high, the buffering is performed. It was unsuitable as a material. Since softwood pulp was blended in Examples 9, 10, and 11, a product having higher strength than the low-density boards obtained in Examples 1 to 8 in which softwood pulp was not blended was obtained.

[0045]

As described above, according to the present invention, a fiber assembly obtained by dry-blending a thermosetting resin fine fiber into a waste paper pulp having a length-weighted average fiber length longer than a specific value is used at a temperature higher than the melting point of the resin fiber. The board obtained by heating and press-molding is a low-density board suitable for use as a cushioning material and a heat insulating material because it has a large cushioning property, excellent moldability, and high strength. Further, by blending softwood pulp, the strength and moldability of the board can be improved. Further, according to the present invention, it is possible to effectively use the waste paper, and the obtained low-density paper is used.
De has a lower combustion energy than conventional polystyrene foams and the like, does not generate toxic gas,
When buried in the soil, it is easily decomposed by microorganisms in the soil. Further, the used low density board can be easily reused as a pulp raw material.

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Claims (8)

[Claims] 1. A fiber assembly obtained by dry-mixing waste paper pulp obtained by dry defibration of waste paper in air without using water at a temperature not lower than the melting point of the thermoplastic resin. A low-density board in which a part or all of the thermoplastic resin fine fibers are melted by heating and pressing to bond waste paper pulp to each other, and the length-weighted average length of waste paper pulp after defibration is used. (Length-weighted average length) is
Low density board characterized by being 0.5 mm or more. 2. The length-weighted average length of the waste paper pulp is 0.
Blended with softwood pulp of 7 mm or more, the weight ratio in the dry state is waste paper pulp / softwood pulp = 95-40 / 5-
The low density board according to claim 1, wherein the low density board has a range of 60. 3. The ratio of waste paper pulp having a fiber length of 0.4 mm or less compared with the number of fibers is 90% or less of all waste paper pulp,
The ratio of waste paper pulp with a diameter of 1 mm or more is 3% of the total waste paper pulp.
It is above, The low density board of Claim 1 or 2 characterized by the above-mentioned. 4. The ratio of used paper pulp having a fiber length of 0.4 mm or less in terms of the number of fibers is 90% or less of the total used paper pulp, and the ratio of used paper pulp of 1 mm or more is used in the total used paper pulp 3.
The fiber length is 0 when compared with the number of recycled paper pulp that is less than or equal to%.
The ratio of softwood pulp of 6 mm or less is 8 of all softwood pulp.
The low density boule according to claim 2, which is 0% or less and is blended with a softwood pulp in which the ratio of the softwood pulp of 1.5 mm or more is 5% or more of the total softwood pulp.
De. 5. The pulp-like multi-branched fiber made of a polyolefin resin having a weight average fiber length of 0.2 to 15 mm, wherein the thermoplastic resin fine fibers are pulp-like multi-branched fibers. The low-density board according to any one of items. 6. The used paper pulp is a pulp obtained by dry-defibrating used paper having a water content in the range of 2 to 15%, according to claim 1, 2, 3 or 4. The low-density board according to any one. 7. A density of 0.01 to 0.4 g / cm ³ is obtained by pressurizing a fiber assembly in which waste paper pulp and fine fibers of a thermoplastic resin are mixed, during or after heat treatment.
Claims 1 and 2, characterized in that
The low-density board according to any one of items 3 and 4. 8. The weight ratio of waste paper pulp and thermoplastic resin fine fibers in an absolutely dry state is as follows: waste paper pulp / fine fibers = 95-60 / 5
~ 40, claim 1, 2, 3,
The low-density board according to any one of items 4 and 5.