JP3291850B2 - Pulp mold manufacturing method - 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 pulp mold mainly used for a packaging material, a cushioning material and the like. In addition to forming an inorganic or organic granular material of the above, and adding a coagulant to the pulp slurry, which is the main raw material of the pulp mold, the disadvantages of using the filtration layer are improved, and in particular, the drainage time The present invention relates to a novel method for improving productivity by shortening the time.

[0002]

2. Description of the Related Art Conventionally, as a mold used in manufacturing a pulp mold, a water hole is formed in an aluminum casting or a stainless steel plate having a predetermined shape, and the surface of the water hole is formed. In many cases, a wire is stretched and then silver-welded to the surface of the substrate in a spot-like manner (Japanese Patent Laid-Open No. 21900/1987). Using a filtration layer formed by filling in a mold base (see JP-A-60-9704).

[0003] As is well known, in the former method, since the filtration layer of the pulp slurry is composed of a simple wire, short fibers or fine fibers having a length of about 0.1 mm or less contained in the slurry are not used. However, when the wire is pulled out of the wire, the yield is low. In addition, when the wire is set on the mold base, a problem as described below occurs. There were also problems with management. That is, in the former mold, when the wire is to be silver-welded to the metal base, the wire has to be brought into close contact with the base, so that it takes a lot of time and labor to manufacture.
In addition, even when drilling water holes in a metal base, it is difficult to make the diameter and distribution uniform, and furthermore, it is often difficult to maintain a uniform degree of adhesion of the wire to the base. However, there is also a drawback that the molded products become irregular. In addition, if the difficulties such as short life of the wire and weakness to wear are counted, it is considered that the conventional wire method should be replaced by the latter porous mold.

However, in the latter mold made of a porous material, the thickness of the filtration layer must be set to a large value, so that clogging is likely to occur due to short fibers or fine fibers present in the pulp slurry. In addition, at least during the repetition of the filtration, the filter layer was clogged and became unusable. In short, the above-mentioned porous mold can provide advantages over the conventional wire type, but the drainage time is significantly longer than the former, and the work efficiency is several steps lower. Met. As described above, each of the conventional methods has advantages and disadvantages, and there is a need for improvement.

[0005] Incidentally, as described in the above-mentioned Japanese Patent Application Laid-Open No. 62-21900, a sulfuric acid band may be used as a fixing agent together with a sizing agent in a raw material pulp solution, In this case, there is no case where a flocculant such as the above-mentioned sulfate band is used for the purpose of collecting short fibers or fine fibers present in the pulp slurry.

[0006]

According to the present invention, a filtration layer, which is a main component of a papermaking mold, is made of inorganic or organic granular material such as hard plastic, glass, ceramic or the like. Structure (1 layer, 2 layers
A coagulant is also added separately to the pulp slurry, which is the main raw material of the pulp mold, in addition to the layered structure, so that the fine fibers are flocculated in the pulp slurry and clogged in the filtration layer. In addition to preventing the occurrence of water, the drainage time is shortened to improve the productivity and thereby enhance the usefulness of the porous filtration layer.

Next, the porous mold as a constituent member of the filtration layer will be described as follows. As a base for defining the outer frame of the mold, an aluminum cast product is generally desirable, and the shape thereof is also free, and it may be a simple ring or a square ring. A skeleton may be provided. In short, any structure can be used as long as it is a frame body capable of forming a narrow space communicating vertically or in the front and back direction by coagulating the granular material described below in a dense state.

In the present invention, examples of the type of the granular material used in the mold include hard plastics, glass, ceramics, and the like. The adhesive used to coagulate the granular material includes And an epoxy resin. Then, after the adhesive is mixed with the granular material, as one example, a filtration layer is formed by applying the adhesive to the surface of a base made of an aluminum cast product having water holes.

Further, the particle size of the granular material in the present invention varies depending on the type of the pulp molded product as a product.
Although it depends on whether the filtration layer is a single layer or a plurality of layers, it is preferable that the gap is in the range of 0.01 to 2.00 mm based on the dimension of the gap. When the filtration layer has a three-layer structure, the gap size of the uppermost layer (in other words, the layer in contact with the pulp slurry) is 0.01 to 0.2 mm, and the gap size of the intermediate layer is 0.1 to 0. .4 mm, the gap size of the lowermost layer is
It is better to keep it in the range of 0.3 to 2.00 mm.

[0010] Examples of the flocculant include a sulfuric acid band and polyaluminum chloride. The type of the flocculant is not particularly limited. It is required to be in the range of 0.5 to 10%, and the effect is small when it is less than the lower limit. If the upper limit is exceeded, a proportional effect cannot be obtained.

[0011] By the way, when it comes to the raw materials of the mold, it is usually wood pulp including waste paper pulp,
In addition, glass fiber, synthetic pulp, and the like may be mixed depending on required characteristics.

[0012]

As described above, in the present invention, a large number of granules are aggregated to form a porous mold.
The thickness of the filtration layer itself exceeds at least 5 mm, and the thickness is greatly increased as compared with the conventional wire mesh type having a thickness of only about 0.1 mm. Short fibers, particularly fine fibers having a length of 0.1 mm or less, are caught by the filtration layer and cause clogging. In other words, in the conventional wire mesh method, the short fibers easily pass through the wire and do not close the opening inside the filtration layer unlike the filtration layer formed by the granular material, but the porous filtration layer formed by the granular material. In the case of (1), since the filtration layer itself has a considerable thickness, it cannot be put to commercial use unless measures are taken to prevent clogging caused by the short fibers or fine fibers. The present invention is an improvement on this point. By adding a flocculant to the pulp slurry, the short fibers or fine fibers are flocculated to prevent the fibers from entering the pores of the filtration layer. To prevent clogging of the filtration layer, and at the same time, to incorporate the fibers into a mold, which is a product, thereby improving the yield and further exerting the full advantage of using a porous mold. It is.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example of a porous mold used in carrying out the present invention will be specifically described with reference to the accompanying drawings, and examples and comparative examples will be given. As shown in FIG. 1, inside a mold base 1 composed of an aluminum casting, as an example, a large number of glass beads having a particle size of 0.78 mm are condensed on the lower side (the side in contact with the pulp liquid) to form a thick plate. A filter layer 2 having a thickness of 2 mm is formed, and a filter layer 3 having a thickness of 28 mm with glass beads having a particle size of 2.60 mm is formed on the upper side (the surface facing the intake side) in the same manner. A porous mold consisting of layers was made. In addition, the whole metal mold | die was a cylindrical shape with a diameter of 120 mm. Incidentally, reference numeral 4 denotes a reinforcing frame provided inside the mold 1, and reference numeral 5 denotes a stock liquid tank in which a pulp slurry is suspended, and a mold in which the porous filtration layer is formed. Is immersed and sucked, whereby the pulp fibers are adsorbed on the surface of the filtration layer to form a mat-shaped molded article.

Although the filtration layers 2 and 3 shown in the drawings have a flat cross section, this filtration layer is not limited to a flat cross section, but may have any cross section. For example, it can be a cup-shaped, hemispherical or zigzag cross-section filter layer,
In short, the shape of the entire filtration layer can be any shape according to the item of the pulp molded article as a product.

[0015]

REFERENCE EXAMPLE 1 A pulp molded article having a dryness of 5 g was prepared using the above-mentioned porous mold and a pulp slurry having a concentration of 1% and a freeness of 300 cc. The suction pressure at that time is -5
It was 00 mmHg. Also, the pulp slurry includes
A sulfuric acid band was added as a flocculant at 3.5% of the pulp.

[0016]

Reference Example 2 The filtration layer in a porous mold had a particle size of 1.0.
0 mm glass beads and a thickness of 20 mm
A pulp molded article was produced in the same manner as in Reference Example 1 except that the filtration layer (single layer) was used.

[0017]

[Reference Example 3] Reference Example 1 except that polyaluminum chloride was used as a coagulant and the addition ratio was 2.5%.
A pulp molded article was prepared in the same manner as in the above.

[0018]

REFERENCE EXAMPLE 4 A pulp molded article was prepared in the same manner as in Reference Example 1, except that the amount of the coagulant added was 1% based on pulp.

[0019]

Reference Example 5 A pulp molded article was prepared in the same manner as in Reference Example 1, except that the amount of the coagulant was 7% based on pulp. Table 1 below shows the results of the measurement of the filtration time in each of the above Examples and the results of visually evaluating whether or not the porous mold used was clogged. The unit of the filtration time is “second”, and the clogging is a result of observing the filtration surface after 50 times of filtration.

[0020]

As is clear from the description in Table 1, when a porous mold is used, drainage time is considerably longer than that of the conventional wire method unless a coagulant is added to the pulp slurry. It was confirmed that it would be longer. In addition, when using a conventional wire mold, the drainage time does not change much without adding a flocculant such as a sulfuric acid band. It was confirmed that it would change.

[0021]

[Table 1]

[0022]

[Discussion] As is apparent from the above comparative example, when a wire mold is used, even if a flocculant such as a sulfuric acid band is added, the effect is not improved as seen in the filtration time. Although the reason is not clear, it is thought that it is caused by the thickness of the filtration layer. In other words, it does not have a thickness like a porous mold, so the short fibers can easily pass through the wire and block the filtration surface without adding a flocculant to aggregate the short fibers and long fibers. It is thought that there is not. On the other hand, in a porous mold,
Since the opening area is considerably smaller than in the case of a wire, and furthermore, since the filtration layer itself has a considerable thickness, if the short fibers or fine fibers are not flocculated beforehand, clogging will occur immediately. Think there is.

[Brief description of the drawings]

FIG. 1 is a partially longitudinal side view showing an example of a porous mold.

FIG. 2 is a plan view of the same as above, with a part cut away.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold substrate 2, 3 Filtration layer 4 Reinforcement frame 5 Stock liquid tank

Continuation of the front page (56) References JP-A-6-128900 (JP, A) JP-A-50-101604 (JP, A) JP-A-53-56254 (JP, A) JP-A-53-14816 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) D21J 7/00

Claims (4)

(57) [Claims] 1. A three-layer structure in which an inorganic or organic particulate material such as hard plastic, glass, or ceramic is filled and condensed inside a metal mold base and communicates in a front-to-back direction.
Forming a filtration layer (excluding one-layer and two-layer filtration layers)
A method for producing a pulp mold, wherein a pulp mold is formed from a pulp slurry to which a coagulant has been added using the filtration layer. 2. The method for producing a pulp mold according to claim 1, wherein said filter layer is formed of a glass or ceramic granule to form a narrow gap of 0.01 to 2.00 mm. 3. A filter layer having a three-layer structure communicating in a front-to-back direction with inorganic granules is formed inside the mold base, and the slit size of the uppermost layer is 0.01 to 0.2 mm.
3. The method for producing a pulp mold according to claim 1, wherein the slit size of the intermediate layer is 0.1 to 0.4 mm and the slit size of the lowermost layer is 0.3 to 2.00 mm. 4. The method for producing a pulp mold according to claim 1, wherein one of a sulfuric acid band and polyaluminum chloride is used as the coagulant.