JPH09324399A - Production of pulp mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pulp mold having smooth surface property of the inside and outside, excellent in dimensional accuracy and useful for packaging material by mixing pulp with a thermally expandable microcapsule type foaming agent in a prescribed amount to prepare pulp slurry and foaming and drying the slurry under specific conditions. SOLUTION: Pulp is mixed with thermally swelling microcapsule type foaming agent in an amount of 1-10wt.% based on pulp to prepare pulp slurry and the slurry is made into a pulp mold by wet type papermaking and the resultant pulp mold is transferred to a mold 10 for drying having clearance which is same as or smaller than the mold thickness in the case of freely foaming the pulp mold and the pulp mold is foamed and dried by heating to provide the objective pulp mold. Furthermore, the foaming agent is preferably aggregate obtained by aggregating plural microcapsules.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pulp mold, and more particularly to a pulp mold suitable for packaging industrial products and food trays.

[0002]

2. Description of the Related Art In recent years, the demand for pulp molds for industrial products and food trays has increased due to increasing environmental problems. However, a conventional wet-molded pulp mold is twisted when it is dried freely and has poor dimensional accuracy. Therefore, stacking is difficult in packing in terms of manufacturing, and work efficiency is deteriorated. Even on the side of packaging industrial products, food trays, etc., the separability of the packaged molded products is poor, and the work efficiency is reduced.

For this reason, the dried molded product is re-shaped by an after-press and shipped. However, this method also has poor productivity due to manual work, and moreover, the wall surface of the mold and the like are broken during after-pressing, which significantly impairs the physical strength.

Therefore, the present inventors have studied to make an accurate pulp mold by using a foaming agent. The purpose of adding a foaming agent to a mold and foaming and molding is known, for example, in Japanese Patent Application Laid-Open No. 8-27700. Although the first invention forms a pulp mold using a pulp slurry, as is clear from the examples, it is a slurry having a pulp solid content of 24%, has very low fluidity, and it is difficult to manufacture a wet pulp mold. . Therefore, it seems that this material is pressed into a mold and heated to foam.

However, although this method has good dimensional accuracy, it is difficult to handle the material and the productivity is extremely low. Various proposals have been made to overcome this situation, but none have been obtained yet.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to produce a pulp mold having high productivity, smooth front and back surface properties, and good dimensional accuracy.

[0007]

Means for Solving the Problems That is, the present invention is 1) mixing 1 to 10% by weight of a thermally expansive microcapsule type foaming agent with pulp to prepare a pulp slurry, and 2) a pulp mold by wet papermaking. 3) transfer the pulp mold to a drying mold having a clearance equal to or smaller than the thickness of the mold when foamed freely, and 4) heat to foam and dry. The present invention relates to a method for producing a pulp mold. Further, the foaming agent is particularly preferably a foaming agent in which a plurality of microcapsules are aggregated.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The heat-expandable microcapsule type foaming agent used in the present invention is one in which the polymer of the outer shell covers the foaming agent as the content and the volume of which expands by several tens of times by heating. is there. For example, the content is ethane,
Hydrocarbons such as ethylene, propane and butane, tetraalkylsilanes such as tetramethylsilane and trimethylethylsilane, water, nitrogen, carbon dioxide and the like can be mentioned. Examples of the outer shell polymer include vinylidene chloride, acrylonitrile, vinyl chloride, acrylic acid ester, methacrylic acid ester, styrene, vinyl acetate, and other polymers or copolymers. Particularly preferred is a microcapsule type foam having a butane content and a vinylidene chloride resin outer shell polymer having a spherical diameter of 15 to 30 μm.

Further, as the foaming agent of the present invention, one obtained by aggregating a plurality of the heat-expandable microcapsules is particularly preferable from the viewpoint of the yield of microcapsules and the productivity of the mold. In order to improve the yield of microcapsules, a method of promoting beating of pulp can be considered,
According to this method, the drainage of the pulp is deteriorated and the productivity is lowered, so that the pulp cannot be used in actual operation.

As a method of aggregating a plurality of foaming agents of the present invention, a method of using a zeta potential control agent,
There are a method using a general polymer flocculant, a method using these and a chemical having a PH control effect such as a sulfuric acid band, and the like, and it is particularly effective to use an anionic flocculant in combination with the above chemicals.

Since the mold clearance for drying is larger than the thickness of the mold formed by wet papermaking before foaming and is equal to or smaller than the thickness of the freely foamed mold, the foamed mold expands without a gap in the mold. Therefore, the mold has good dimensional accuracy and a clean surface.

In the present invention, the blowing agent is 1 for pulp.
It is used by mixing 10 to 10% by weight. The concentration of the pulp slurry is set to about 0.5 to 2.0% in consideration of paper-making property.

Next, a wet mold is prepared by a conventional method using a papermaking mold and a take-up mold.

Next, it is put in a drying mold and heated to foam and dry. FIG. 1 shows a wet papermaking pulp mold 14,
Male type 10 having heater 12 and air hole 20 respectively
FIG. 3 is a cross-sectional view set in a drying mold composed of a female mold 11 and a female mold 11. Reference numeral 13 represents a clearance. The heater 12 heats the mold and at the same time sucks the heated air by a suction pump (not shown) to dry and foam. The mold for drying has a clearance larger than the thickness of the mold before wet foaming and equal to or smaller than the thickness of the freely foamed mold.

FIG. 2 is a sectional view in which the drying mold is heated to foam the pulp mold. Clearance 13 in FIG.
Is filled with the pulp mold 15 after foaming. The heating condition varies depending on the required quality characteristics, but is generally performed at a temperature of 150 to 200 ° C. and a time of 0.5 to 2 minutes.

The present invention will be described in more detail with reference to the following examples.

Example 1 Waste paper was disintegrated with water to make a 1% pulp slurry.
A foaming agent of 10% by weight based on pulp was added to this slurry.
The foaming agent was butane, a microcapsule of vinylidene chloride resin having an outer diameter of 15 to 30 μm. A wet mold was made with a papermaking mold and a take-up mold. At this time, the yield of microcapsules and the papermaking time were measured. The thickness of the mold was 1 mm. Put this mold in a mold for drying with a 3mm clearance between male and female,
It was heated at 1.5 minutes for foaming and drying. The mold water content dropped from 73% to 10%, and the mold thickness was tripled to fill the voids. The appearance and dimensional accuracy of the pulp mold after foaming were visually observed. The mold weight was also measured. The results are shown in the table.

Example 2 A pulp mold was prepared under the same conditions as in Example 1 except that the microcapsules used in Example 1 were aggregated on average, and the same evaluation was made. The results are shown in the table.

Example 3 The same conditions as in Example 1 were used except that the blowing agent used was an isobutane content and a vinylidene chloride / acrylonitrile copolymer outer shell agglomerated on average with three microcapsules having a spherical diameter of 10 to 20 μm. The pulp mold was made with and the same evaluation was made. The results are shown in the table.

Comparative Example 1 Waste paper was disintegrated with water to make a 1% pulp slurry.
A wet mold was made with a papermaking mold and a take-up mold. The thickness of the mold was 2.5 mm. This mold was dried by heating at 110 ° C. for 40 minutes in a dryer. Mold moisture dropped from 73% to 7%. Since the appearance was poor (there was a twist), it was put in a mold for afterpressing with a clearance of 1.5 mm and afterpressing. The appearance and dimensional accuracy were visually observed. The results are shown in the table.

From the above results, it is clear that according to the present invention, a pulp mold which is lightweight and has high dimensional accuracy can be produced at a high speed. It is also clear that the yield of the foaming agent can be increased.

[0022]

[Table 1]

[0023]

EFFECTS OF THE INVENTION 1) Since the yield of the foaming agent is good, and the papermaking speed is high, it is possible to produce an inexpensive pulp mold with high productivity. 2) It is possible to manufacture a pulp mold with extremely high dimensional accuracy, although there is some variation in density between mold parts. 3) Since it is not necessary to perform after-pressing, the breakage that has been generated in the conventional after-pressing does not occur. 4) Due to the expansion from the inside, the dimensional accuracy can be obtained with the regulated die, so that the degree of freedom of the shape of the die is large as compared with the conventional after-press method.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in which a wet papermaking pulp mold is set in a drying mold.

FIG. 2 is a cross-sectional view in which a pulp mold is foamed by heating a drying mold.

[Explanation of symbols]

 10 Drying male type 11 Drying female type 12 Heater 13 Clearance 14 Mold before foaming 15 Mold after foaming 20 Air holes

Claims (2)

[Claims] 1. A method for producing a pulp mold, which comprises the following steps. 1) Mixing 1 to 10% by weight of a thermally expansive microcapsule type foaming agent with respect to pulp to prepare a pulp slurry, 2) making a pulp mold by wet papermaking, and 3) freely making the above pulp mold. Transfer to a drying mold having a clearance equal to or smaller than the mold thickness when foamed, and 4) heat to foam and dry. 2. The method according to claim 1, wherein the foaming agent is an aggregate in which a plurality of microcapsules are aggregated.