JP3511742B2 - Method for producing low density molded article and low density sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a low-density molded product and a low-density sheet which are excellent in cushioning property and suitable as a cushioning material for packaging, using pulp fibers.

[0002]

2. Description of the Related Art Generally, various characteristics are required as the performance of a cushioning material for packaging, but basically, the important performance is as follows.
This is the role of protecting the packaged cargo from shocks, vibrations, etc. during the distribution process. 2. Description of the Related Art Conventionally, as a cushioning material for packaging, a foamed body of a synthetic resin such as polystyrene, polyurethane, or polyethylene has been widely used in a wide field. However, these synthetic resin foams have strength, are easy to process into various molded bodies, and are convenient to use, but on the other hand, there is no suitable method for treating used foams. The current situation is causing environmental problems. That is, since the synthetic resin used for the foam has a high combustion calorie, burning the used foam raises the combustion temperature and causes a problem of damaging the incinerator. However, there is a problem that when it is left in a natural environment, it is not biodegradable and is not decomposed and pollutes the environment.

Therefore, a method for producing a foam by mixing cellulose fibers with a synthetic resin (Japanese Patent Laid-Open No. 55-23109).
Japanese Patent Publication No. 3-269025, Japanese Patent Publication No.
19152) and cellulose fibers, and a composition in which an adhesive selected from animal and vegetable pastes, synthetic resin emulsions, rubber latices and the like is blended at a constant ratio, and a foaming agent having a decomposition temperature of 100 ° C. or less is contained. Then, a method for producing a foam by foaming and foaming (JP-A-7-41588) is proposed.

On the other hand, as a low-density sheet material, a method of producing a low-density and bulky paper by heating a base paper obtained by mixing a cellulose fiber with a particulate foaming agent to make a paper ( Japanese Unexamined Patent Publication (Kokai) No. 5-339898), bulky paper made by blending hollow spherical vaterite type calcium carbonate with cellulose fibers (Japanese Unexamined Patent Publication No. 3-124895).
Gazette), a bulky sheet obtained by molding a mixture of a cross-linking pulp obtained by reacting a cross-linking agent in the presence of a softening agent for fibers, and a heat-fusible fiber (JP-A-4-202895). A bulky paper (Japanese Patent Laid-Open No. 2-300398) made of an eccentric core-sheath type or a side-by-side type composite fiber whose crimp form is a spiral crimp is disclosed. In the method of foaming with the above-mentioned foaming agent, it is difficult to control the foaming state, the foamed cells are likely to be nonuniform, and the structurally nonuniform foam is likely to be formed.

Further, in the case of a sheet material using a cellulosic material, in the method of producing a bulky sheet using a synthetic resin, synthetic fibers, and a filler, the obtained low-density molded product has a contact point between fiber materials. However, even if it is excellent in bulkiness, it has low strength, and its shape is changed during molding, resulting in poor workability. Further, when the heat-sealing fiber is used, the cellulose fiber content is decomposed in the natural world, but the heat-sealing fiber is made of a synthetic resin so that it is hardly decomposed in the natural world and becomes a source of environmental pollution.

[0006]

In view of the above situation, the inventors of the present invention have made extensive studies as to a method for producing a buffer material that can be used without environmental pollution, and as a result,
Cellulose fibers that are biodegradable even if discarded and do not have an adverse effect on the environment, and do not cause problems to the incinerator or the environment even when incinerated. Focusing on the fact that it is toughened, and that the cellulose fibers that are crosslinked, curled such as twisted and deformed, and have extremely low bond strength have excellent compressibility, and a specific amount of these fibers is combined to make a raw material. The molded body obtained by deliquoring and drying with a molding machine equipped with a net is excellent in compressive strength and buffering property even though it has a low density, has a strong bonding strength, and is extremely excellent as a buffering material or a packaging material, Further, they have found that a sheet obtained by paper-making and drying the above raw material with a wet paper machine has low density and excellent strength, and thus completed the present invention. An object of the present invention is to provide a method for producing a molded product having a low density and excellent compressive strength and cushioning properties, and a sheet having a low density and excellent strength.

[0007]

The first object of the present invention is to make fine fiberized pulp having a water retention of 210 to 450% based on the total fiber weight of 3 to 65% by weight and a water retention of 25 to 65% and a wet curl. A water slurry obtained by using a mixture containing 35 to 97% by weight of curled fiber having a factor in the range of 0.5 to 1.0 based on the total fiber weight as a raw material was introduced into a molding machine equipped with a net, and deliquored. It is a method for producing a low-density molded product, which comprises molding and drying. The second aspect of the present invention is that the water retention is 2
10 to 450% of fine fiberized pulp 3 per total fiber weight
To 65% by weight, and water made from a mixture containing 35 to 97% by weight of curled fiber having a water retention of 25 to 65% and a wet curl factor in the range of 0.5 to 1.0, based on the total fiber weight. A method for producing a low-density sheet, which comprises making a slurry into a paper using a wet paper machine and drying the paper.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a method for producing a low-density molded body or sheet by molding or papermaking a mixture containing fine fiberized pulp and curled fiber. The fine fiberized pulp used in the present invention is one in which pulp fibers are made fine and the water retention is in the range of 210 to 450%. Such fine fiberized pulp is a pulp fiber medium stirring mill treatment (JP-A-4-18186), a vibration mill treatment (JP-A-6-10286), a treatment in a high-pressure homogenizer, a colloid mill treatment. Etc. are manufactured.

Among the devices used in the above-mentioned treatment method, the medium stirring mill is filled in the grinding container by rotating the stirring machine inserted in a fixed grinding container at high speed.
It is a device that agitates a medium such as glass beads or alumina beads and pulp fiber, and pulverizes the pulp fiber by shearing stress.The pulverizing device includes a tower type, a tank type, a flow pipe type, an annular type, etc. Any type of device can be used with the present invention. A vibrating mill is a device that vibrates a crushing container at high speed and applies a force such as an impact force or a shearing force to pulp fibers by beads, balls, rods, etc. filled in the container to perform a crushing process. The homogenizing device is a device that crushes and disperses pulp fibers by applying high pressure to the pulp fiber slurry so that the pulp fiber slurry passes through the small-diameter orifices.

The fine fiberized pulp obtained by the medium agitation mill or the vibration mill has higher flexibility of pulp fibers than other processing devices, and the fine fiberization is performed not only in the longitudinal direction of the fibers but also three-dimensionally. Therefore, the curled fibers used in the present invention can be efficiently and strongly bonded to each other, which is preferable, but the present invention is not particularly limited to the method for producing fine fiber pulp. However, the water retention of the fine fiberized pulp used in the present invention is 210%.
If it is less than the above, because the micronization is not sufficient, the binding between the curled fibers is not sufficient, and the molded product obtained by the combination of such microfiberized pulp and the curled fiber has a weak shape retention force and loses its shape. The sheet is not practical because it does not exhibit strength. On the other hand, if the water retention of the fine fiberized pulp exceeds 450%, the pulp fiber becomes finer and at the same time the fiber shortening is extremely advanced. Therefore, a combination of such fine fiberized pulp and curled fiber was obtained. Not suitable because the strength of the molded body or sheet becomes weak.

Examples of the raw materials for the fine fiberized pulp include chemical pulp obtained by craft cooking, soda cooking or sulfite cooking of softwood and hardwood, pulp from cotton and linter, waste paper pulp, and the like. Bleached or unbleached may be appropriately selected and used alone or as a mixture, but is not particularly limited thereto.

The curled fiber used in the present invention is, in terms of morphology, deformed such as curl and twist due to a chemical bond due to a cross-linking reaction, which is permanently imparted to the long fiber, and is bent, so that the length of the original fiber becomes equal to that of the original fiber. Compared with pulp fibers, the apparent length is smaller. However, such a deformation of the fiber may cause the strain in the fiber to be released due to the wetting of the fiber by water even if the deformation is maintained in a dry state, and the degree of the deformation may be weakened. In the present invention,
One of the bent fibers that is deformed in this way
As an index showing the degree of deformation of a book, the length of one fiber after immersion in water is observed with a microscope, and how much the deformation of the fiber deviates from the linear length of the original fiber Wet curl factor that was quantified is used. In the present invention, the wet curl factor is the actual length (LA) of the fiber after the curled fiber is immersed in pure water at room temperature for 24 hours and the maximum projected length of the fiber (the length of the longest side of the rectangle surrounding the fiber). Now, measure LB), {(LA / LB) -1}
It is defined as the value calculated in.

Known curled fibers can be used for the present invention. For example, a C2-C8 dialdehyde and a C2-C8 monoaldehyde having an acid functional group are used to crosslink the inside of the cellulosic fiber, and the cellulosic crosslinked fiber having an average water retention of 28% to 50% (Japanese Patent Publication No. -71702), a cellulosic fiber is internally crosslinked with a C2 to C9 polycarboxylic acid, and the crosslinked fiber has a water retention of about 25% to 60% (JP-A-3-20617).
No. 4, JP-A-3-206175, and JP-A-3-206175.
206176), and further commercially available products (for example, product name: HBA-FF, manufactured by Warehauser, USA).
And the like, which are appropriately selected and used. When producing cross-linked fibers, after adding a cross-linking agent to pulp fibers, mechanical stirring is performed, then fluffing and heat treatment are performed, and if the fibers are fixed with deformation, the curl with a larger wet curl factor is obtained. Fiber is obtained.

However, in the pulp fibers having these cross-linking bonds, the hydroxyl groups (-OH) of the cellulose molecules are reduced by the cross-linking treatment, and therefore the hydrophilicity of such fibers is smaller than that of the pulp fibers not subjected to the cross-linking treatment. The value of the water retention, which indicates the ability to retain water, decreases, and the value is within the range of 25 to 65%. If the water retention is less than 25%, the ability to form interfiber bonds will be significantly reduced, and the strength of the molded body and paper will be insufficient even when used in combination with fine fiberized pulp. Conversely, the water retention will exceed 65%. When the size becomes larger, the ability to maintain the applied deformation becomes insufficient, the wet curl factor becomes too low, and it becomes impossible to obtain a molded body and a sheet having a low density. The wet curl factor of the curled fiber used in the present invention is in the range of 0.5 to 1.0. When the wetting factor of the carded fiber is less than 0.5, the bulkiness becomes small, and a low-density molded body or sheet cannot be obtained. Conversely, when the curl factor exceeds 1.0, the pulp fiber is deformed. It is necessary to strengthen the mechanical treatment at the time of applying, but doing so causes damage to the pulp fibers and significantly reduces the strength of the molded body or sheet, which is not suitable for practical use.

As described above, in the case of the curled fiber having a wet curl factor in the range of 0.5 to 1.0, the pulp fiber is deformed to a considerable extent, is bent, and is crosslinked. Since the fibers are rigid because
The probability of fibers coming into contact with each other is lower than that of ordinary pulp fibers that are neither deformed nor cross-linked. Further, such curled fiber alone is used to form a molded body or sheet as a slurry, which is then dehydrated and dried. In addition, since the entanglement of fibers is weak and it is difficult to generate hydrogen bonds due to hydroxyl groups,
The strength of the molded body or sheet is extremely weak and it cannot be put to practical use. However, as described above, it has been found that a molding material or sheet having a low density and a high strength can be produced by adding a fine fiberized pulp to a curled fiber, but the balance between the density and the strength is: It is controlled by changing the mixing ratio of carded fiber and fine fiberized pulp.

The low density in the present invention means that the density of both the molded body and the sheet is in the range of 0.05 g / cm ^{3 to} 0.35 g / cm ³ , and in order to give practical strength, the above-mentioned is used. It is necessary to mix the fine fiberized pulp having the characteristics in an amount of 3 to 65% by weight based on the total dry fiber weight, and the curled fiber having the characteristics described above in a ratio of 35 to 97% by weight based on the total dry weight of the total fiber. . Fine fiberized pulp 3
If it is less than wt%, the strength of the molded body or sheet will be insufficient,
It cannot be put to practical use, and conversely, fine fiberized pulp is 6
If it exceeds 5% by weight, the density becomes higher than 0.35 g / cm ³ . Known bleached or unbleached pulp fibers, which are known as other fiber raw materials, can be used in the low-density molded body or sheet within the range of the mixing ratio of the fine fiberized pulp. Known pulp fibers include softwood chemical pulp, hardwood chemical pulp, mechanical pulp such as GP and TMP (thermo-mechanical pulp), bleached or unbleached waste paper pulp, cotton pulp, linter pulp, etc., unbeaten or beaten. Examples thereof include, but are not particularly limited to.

The low-density molded article of the present invention is obtained by introducing the mixed raw material containing the above-mentioned curled fiber and fine fiberized pulp into a metal mold having a desired shape, which is used in pulp mold production, Then, it is dehydrated and dried by suction or pressure to obtain a molded product having a desired shape, and the low density can be easily controlled by the ratio of the fibers used to provide various levels of compressibility and a cushioning material. A molded body that can be suitably used as is obtained. Similarly, the low-density sheet of the present invention is obtained by paper-making the above-mentioned mixed raw material by a known wet papermaking method and drying, and a sheet having a low density and excellent strength can be obtained. Further, in order to further improve the strength of the low-density molded product or sheet, a known paper-strengthening agent used for papermaking may be added. As the paper strength enhancer, urea formaldehyde resin, melamine formaldehyde resin, polyamide urea formaldehyde resin, ketone resin, polyamide epichlorohydrin resin, polyamide polyamine epichlorohydrin resin, glycerol polyglycidyl ether resin,
Examples thereof include polyethyleneimine resin, and these paper-strengthening agents may be used alone or in combination of two or more kinds as appropriate. With these paper strength agents,
At the same time as the strength in the dry state is improved, the strength in the water-wet state is also increased, and it is possible to obtain a molded product having higher compression resistance or a sheet having excellent strength.

[0018]

The present invention will be described in more detail with reference to the following examples, but of course the present invention is not limited thereto. In Examples and Comparative Examples,% means% by weight unless otherwise specified.

Example 1 A 1.5 liter Dynomill (type: KDL-PILOT type, manufactured by Simmar Enterprises Co., Ltd.) apparatus in which a water slurry of bleached kraft pulp of hardwood having a solid content of 1% was filled with glass beads. Was introduced at a rate of 350 ml / min and passed through to produce a fine fiberized pulp. This pulp has a water retention of 280%, and is composed of 10% of this pulp and 90% of a curled fiber (HBA-FF, trade name: American Weehauser Co., Ltd.) having a wet curl factor of 0.65 and a water retention of 50%. The mixture was made into a water slurry having a solid content of 1%, and after sufficiently stirring, the slurry 30
0 ml was concentrated and deliquored with a Buchner funnel with a diameter of 11 cm,
Then, the concentrate was filled into an 80-mesh stainless wire 3 cm x 3 cm x 3 cm cubic container open in one direction by gently pushing it uniformly by hand, and the container was filled with a hot air circulation dryer at 105 ° C. It was put into a container and dried for 3 hours to obtain a molded body. The density of the molded body is 0.09g
/ Cm ³ . Further, a compression test was conducted on the molded body to evaluate the compression characteristics. The test methods for water retention, wet curl factor and compression test used in the present invention are as follows.

Test method (1) Water retention The water retention is based on JAPAN TAPPI No. 26-78
It was measured according to. If the carded fibers were dry, then: A sample of 0.5 g of absolute dry sample was taken, sufficiently dispersed in 100 ml of distilled water, and then left as it is.
After being left at room temperature for a long time to be sufficiently impregnated with water, the sample is collected on a filter, and then a centrifuge having a G2 glass filter (model: H-103N, manufactured by Domestic Centrifuge).
It was placed in a centrifuge tube of No. 1 and subjected to centrifugal dehydration for 15 minutes at 3000 G of centrifugal force. The centrifugally dehydrated sample was taken out from the centrifuge tube, weighed in a wet state, then dried in a drier at 105 ° C. until a constant weight was obtained, the dry weight was measured, and the water retention was calculated by the formula (1). In the case of fine fiberized pulp, the solid content concentration is adjusted to a range of 6 to 9%, a sample is collected so as to have an absolute dry weight of 0.7 g, and the sample is placed in a centrifuge tube having a G3 glass filter. Centrifugal dehydration treatment was carried out in the same manner as above, and the water retention was calculated from the wet weight and the dry weight by the formula (1). Water retention (%) = {(WD) / D} × 100 (1) However, W is the wet weight of the sample after centrifugal dehydration (g), and D is
It is the dry weight (g) of the sample.

(2) Wet curl factor 100 pieces of curled fiber after soaking in pure water at room temperature for 24 hours are placed on a microscope slide glass, and an actual image of each fiber is obtained by using an image analyzer. (Linear)
The length LA (μm) and the maximum projected length (equal to the length of the longest side of the rectangle surrounding the fiber) LB (μm) were measured, the wet curl factor was obtained from the equation (2), and the average value thereof was used. . Wet curl factor = (LA / LB) -1 (2) (3) Compression characteristics Cut the obtained molded body with a cutter knife, and 2 cm x 2
A cm × 2 cm cube was obtained. The compression characteristic of this cube was measured by a straw graph tensile tester (model: M2, manufactured by Toyo Seiki Seisakusho). 100kg as a load cell
The test was carried out using a compression rate of 20 mm / min. As the compression characteristics of the test body, strain (%) was plotted on the x-axis and compression stress was plotted on the y-axis, and Young's modulus was calculated from the slope of the first straight line portion of the curve. Also, the compressive stress when the strain is applied 60% (12 mm) is obtained, and after the strain is further applied 75% (15 mm), the ratio of the strain to the original height (20 mm) after 24 hours has elapsed is permanently set. It was defined as strain and calculated from equation (3). Permanent strain (%) = {strain (mm) / original height (mm)} × 100 ... (3)

Example 2 A molded body was prepared in the same manner as in Example 1 except that a mixture of 40% carded fiber and 60% fine fiber pulp was used, and the density was measured to evaluate the compression characteristics. did. The density was 0.28 g / cm ³ .

Comparative Example 1 90% carded fiber and bleached hardwood kraft pulp were beaten in a laboratory Niagara beater (capacity: 23 liters, manufactured by Tozai Seiki) at a pulp concentration of 2% to a Canadian standard freeness of 100 ml. 180% pulp 1
A molded body was produced in the same manner as in Example 1 except that the mixture with 0% was used, the density was measured, and the compression characteristics were evaluated. The obtained molded body is 2 cm x 2 cm with a cutter knife.
When cut into a cube of × 2 cm, the shape of the cube collapsed, the surface of the cube could not be cut smoothly, and irregularities were generated on the surface. The density was 0.09 g / cm ³ .

Comparative Example 2 Untreated unbleached softwood kraft pulp 9 having a wet curl factor of 0.33 and a water retention of 135%.
A molded product was prepared in the same manner as in Example 1 except that a mixture of 0% and 10% of fine fiberized pulp having a water retention of 280% prepared by treating a hardwood bleached kraft pulp with Dynomill was used. The density was measured and the compression characteristics were evaluated. The density was 0.19 g / cm ³ .

Comparative Example 3 40% of unmodified unbleached softwood kraft pulp having a wet curl factor of 0.33 and a water retention of 135% and a hardwood bleached kraft pulp were treated with a Dynomill to prepare a water retention. A molded body was prepared in the same manner as in Example 1 except that a mixture with 280% fine fibrous pulp 60% was used, and the density was measured and the compression characteristics were evaluated. The density was 0.39 g / cm ³ .

Comparative Example 4 Two commercially available polystyrene foams (density 0.02 g / cm ³ ) were used.
A cubic cube of cm square was cut with a cutter knife, and this was used as a sample to evaluate the compression characteristics.

Example 3 30 g of dried coniferous bleached kraft pulp was placed in a double-arm kneader (model: S1-1, manufactured by Moriyama Seisakusho) having a capacity of 1 liter, and a non-formaldehyde-based crosslinking agent (trademark: Sumitex NF-). 500K, Sumitomo Chemical Co., Ltd. and its cross-linking aid (trademark: Sumitex ACCELERATOR X)
-60, manufactured by Sumitomo Chemical Co., Ltd.) and 3.0% and 0.25%, respectively, based on the weight of the absolutely dry pulp, and then water to adjust the solid content concentration to 35%, and then the double arms at 27 ° C. Were rotated at 60 rpm and 100 rpm, respectively, and stirred for 20 minutes. Then, the pulp was taken out from the kneader, and the pulp was well loosened by hand, and then the lump of pulp was disintegrated and fluffed by an experimental Warren blender, and then the fluffed pulp was put in a blast dryer at a temperature of 150 ° C. After being dried for 2 hours in a restrained state, the dried pulp was taken out from the dryer and cooled. The wet curl factor of the obtained curled fiber is 0.7.
5, the water retention was 45%.

A mixture of 40% of this curled fiber and 60% of fine fiberized pulp having a water retention of 280% prepared by using hardwood bleached kraft pulp in the same manner as in Example 1 was placed in a disintegrator, and the solid content concentration was increased. Stirring at 2% gave a well dispersed fiber slurry. A sheet having a basis weight of 60 g / m ² was prepared by a square (25 cm × 25 cm) hand-made sheet machine equipped with an 80 mesh bronze wire using this slurry as a paper material, and dried with a hot air dryer at 105 ° C. to form the sheet. Obtained. Using the obtained sheet, the basis weight (P-8124), the thickness and the density (P
-8118) and tensile strength (breaking length, P-8113)
Was measured and the quality was evaluated.

Example 4 Curled fiber having a wet curl factor of 0.65 and a water retention of 50% (HBA-manufactured by Warehauser, USA)
FF) 75% and 25% of fine fiberized pulp having a water retention of 220% and produced by treating with a Dynomill in the same manner as in Example 1 with a liquid feed rate of 700 ml / min when producing fine fiberized pulp. Except that a mixture of
A sheet was prepared in the same manner as in Example 3 and its quality was evaluated.

Example 5 Polyacrylamide resin (trade name: AF-100, manufactured by Arakawa Chemical Industry Co., Ltd.) as a paper strengthening agent was added to the paper material used in Example 4 in an amount of 0.5 per dry fiber weight. %, A sheet was prepared in the same manner as in Example 3 except that the content was added, and the quality was evaluated.

Example 6 60% of a curled fiber having a wet curl factor of 0.65 and a water retention of 50%, and 20% of a fine fiberized pulp having a water retention of 280% obtained by treating in the same manner as in Example 1, Further, a sheet was prepared and the quality thereof was evaluated in the same manner as in Example 3 except that a mixture of 650 ml of freeness of 650 ml and 20% of bleached softwood kraft pulp beaten with a laboratory niagara beater was used as a paper material.

Comparative Example 5 Addition rates of the cross-linking agent and the cross-linking aid were 0.2% and 0.
Wet curl factor 0.4 in the same manner as in Example 3 except that the treatment time in the kneader was 5 minutes.
A curled fiber having a water retention of 70% was produced. Furthermore, the pulp solid content concentration is 0.5%, and the liquid transfer amount is 700 ml.
The water retention is 18 in the same manner as in Example 1 except that the water retention rate is 18 minutes.
A fine fiberized pulp of 0% hardwood pulp fibers was prepared. Then, a sheet was prepared in the same manner as in Example 3 except that a mixture of the above-mentioned curled fiber 75% and fine fiberized pulp 25% was used as a paper material, and the quality thereof was evaluated.

Comparative Example 6 A curled fiber having a wet curl factor of 0.65 and a water retention of 50% (HBA-manufactured by Warehauser, USA).
FF) 75% and 25% of finely fibrillated pulp having a water retention of 475% and produced in the same manner as in Example 1 at the time of producing the finely fibrillated pulp at 100 ml / min. A sheet was prepared in the same manner as in Example 3 except that it was used as a material, and its quality was evaluated.

Comparative Example 7 Wet curl factor 1. prepared in the same manner as in Example 3 except that the treatment time in the kneader was 60 minutes.
1. 75% of curled fiber having a water retention of 50% and 25% of fine fiberized pulp having a water retention of 220% used in Example 4
A sheet was prepared in the same manner as in Example 3 except that the mixture of and was used as a paper material, and the quality was evaluated.

Table 1 shows the results of the molded products obtained in Examples 1 and 2 and Comparative Examples 1 to 4.

[0036]

[Table 1]

The results of the sheets obtained in Examples 3 to 6 and Comparative Examples 5 to 7 are shown in Table 2.

[Table 2]

As can be seen from Table 1, the molded product of the present invention has a low density, and the density and Young's modulus can be controlled by changing the compounding ratio of the curled fiber and the fine fiberized pulp (Examples). 1, 2). The molded product having the lowest density (Example 1) is slightly inferior in density to the expanded polystyrene (Comparative Example 4), but has substantially the same physical properties and has excellent quality as a cushioning material. When a pulp having a high beating degree is used instead of the fine fiberized pulp, physical properties such as Young's modulus and compressive stress are comparable, but the moldability is poor and the shape is likely to be deformed (Comparative Example 1) Pulp having a low wet curl factor When a large amount of fibers is used, the Young's modulus increases and the permanent set also increases, so that the properties as a cushioning material deteriorate (Comparative Example 2). Furthermore, when the amount of the high-beaten pulp fiber used in combination with a pulp fiber having a low wet curl factor is increased, strength is developed in the same manner as described above, Young's modulus, compressive stress and density are increased, and permanent set is also increased. The characteristics as a cushioning material are inferior (Comparative Example 3).

As can be seen from Table 2, the sheet of the present invention has a low density and, on the other hand, a high tensile strength (Examples 3 to 4). When a paper strengthening agent is added to the raw material used in the present invention, the breaking length can be further increased (Example 5), and the density is low even when untreated pulp which is not deformed is used in combination. A strong sheet is obtained while maintaining the level (Example 6). On the other hand, when the curled fiber having a low wet curl factor is used, the density becomes high, and the sheet becomes weak in comparison with that (Comparative Example 5). On the other hand, when fine fiberized pulp having too high water retention is used, the density is relatively low, but the strength is also low (Comparative Example 6).
On the contrary, if the wet curl factor is too high, the density can be lowered but the strength cannot be improved (Comparative Example 7).

[0040]

INDUSTRIAL APPLICABILITY As described above, the present invention has the effect of providing a molded product having a low density and excellent compressive strength and cushioning properties, and a method for producing a sheet having a low density and excellent strength.

Continuation of front page (56) References JP-A-5-71702 (JP, A) JP-A-4-202895 (JP, A) JP-A-4-18186 (JP, A) JP-A-6-146195 (JP , A) JP-A-6-10286 (JP, A) JP-B-62-33360 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) D21H 11/00-27/42 D21J 1/00-7/00

Claims (2)

(57) [Claims] 1. A fine fibrous pulp having a water retention of 210 to 450% and a water retention of 2 to 3 to 65% by weight based on the total fiber weight.
A curled fiber having a wet curl factor of 5 to 65% and a range of 0.5 to 1.0 is used in an amount of 35 to 35 based on the total fiber weight.
A water slurry using a mixture containing 97% by weight as a raw material,
A method for producing a low-density molded product, which comprises introducing into a molding machine equipped with a net, deliquoring, molding and drying. 2. A fine fiberized pulp having a water retention of 210 to 450% and a water retention of 2 to 3 to 65% by weight based on the total fiber weight.
A curled fiber having a wet curl factor of 5 to 65% and a range of 0.5 to 1.0 is used in an amount of 35 to 35 based on the total fiber weight.
A water slurry using a mixture containing 97% by weight as a raw material,
A method for producing a low-density sheet, which comprises making a paper with a wet paper machine and drying.