JPS5828400B2 - Taisuisei Taisiyafutsusei Narabini Suijyoukitoukaseinisgreta Kamiyokinoseizouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a paper container having excellent water resistance, boiling resistance, and water vapor permeability, and is particularly suitable for manufacturing a paper container having a search part such as a pot-shaped container. Concerning suitable methods.

Conventionally, as a manufacturing method for paper containers with water resistance, boiling resistance, and water vapor permeability, as shown in Japanese Patent Publication No. 454,716, synthetic resin powder is blended with wood pulp, and an appropriate amount of sizing agent is added. A method is known in which a valve seat is made by blending sulfuric acid band, and the valve seat is pressed into a desired shape and size.

However, although the valve seats used in this method are mixed with sizing agents and sulfuric acid, they are essentially just wood pulp mixed with synthetic resin powder, so they cannot be used in product containers. In order to maintain a certain degree of water vapor permeability, boiling resistance, and water resistance, the wall thickness must be kept within 1 inch, and therefore relatively deep containers cannot be manufactured using the above method. is the reality.

In other words, with the method disclosed in Japanese Patent Publication No. 45-4716, which involves stamping and molding a container from a valve seat that is simply compounded with synthetic resin powder, it is almost impossible to manufacture a paper container that has a cut-out portion with a depth of 30 mm or more. be.

As a method for manufacturing relatively deep paper containers such as pot-shaped containers, a method taught in Japanese Patent Publication No. 44-21592 is known.

This method uses two or more types of wood pulp slurry with different amounts of synthetic resin powder and two or more sand boxes with different sizes to make two or more types of similar container substrates, and then This is a method in which the container bases are fitted one after another and then heated and pressed in a mold to form a multilayer container body (
(Hereinafter, this method will be abbreviated as the pulp mold method for convenience.)
.

Using this pulp molding method, it is possible to manufacture paper containers with a depth of 30 mm or more, but this method requires the preparation of two or more types of wood pulp slurry with different amounts of synthetic resin powder. Of course, two or more types of similar container bases must be made individually and fitted together one after another, and furthermore, the sequentially fitted similar container bases must be heat-pressed. It cannot be denied that the manufacturing process is extremely complicated.

Therefore, the present invention can produce relatively deep paper containers, which could only be manufactured by pulp molding in the past.
Specifically, we are looking for paper containers that have a depth of 30 cm or more and have excellent water resistance, boiling resistance, and water vapor permeability.
, provides a manufacturing method using an extremely simple means of embossing molding, the gist of which is 80 to 50 wt%
A pulp mixture of wood pulp of
t% of hot water-insoluble synthetic resin powder, an appropriate amount of sizing agent, and sulfuric acid band are mixed together to form a valve seat with a thickness of 3 to 7 mπ, and this valve seat is heated at a temperature of 150 to 200 mπ.
After pre-pressing at 180-250°C to reduce the sheet thickness by 30-50%, the compressed sheet is punched into the desired shape and dimensions, and then the punched sheet is pressed at a temperature of 180-250°C and a pressure of 10%.
It consists of stamp molding under conditions of ~100 kg/crt't.

Moving on to explain the material of the valve seat used in the method of the present invention, first, as the wood pulp, bleached pulp manufactured from softwood, hardwood, bamboo, bagasse, rice straw, wheat straw, etc. is used.

On the other hand, the thermoplastic synthetic resin pulp referred to in the present invention is manufactured from thermoplastic synthetic resins such as high-density polyethylene, polypropylene, acetate, polyester, and polyamide, and has a melting point of 130°C or higher and an average fiber length of 0.8 mm or higher. Thermoplastic synthetic resin pulp (made of high-density polyethylene) manufactured by Mitsui Zerabak Co., Ltd., which is commercially available under the trade name "Shizui", is a typical example of this type of pulp-like material.

The mixing ratio of wood pulp and thermoplastic synthetic resin pulp is
In the present invention, it is possible to use wood pulp in a range of 80 to 50 wt% and thermoplastic synthetic resin pulp in a range of 20 to 50 wt%.

The above-mentioned pulp mixture contains 5 to 20wt on a pulp basis.
% of synthetic resin powder is blended, and as such synthetic resin powder, hot water-insoluble powder obtained from thermoplastic synthetic resins such as polyethylene, polyvinyl chloride, polyacrylate, polystyrene, polyester, polyamide, etc. is used. Ru.

It is preferable that the particle size of the powder is usually 200 mesh or less.

These synthetic resin powders fill the gaps between pulp fibers and contribute to improving the water resistance of product paper containers.

The valve seat of the present invention preferably also contains a sizing agent and a fixing agent, and any of the agents currently used in the paper industry can be used.

Incidentally, a rosin sizing agent is commonly used as a sizing agent, and sulfuric acid is commonly used as a fixing agent.

It goes without saying that additives commonly used in the paper cutting industry can also be incorporated into the valve seat of the present invention, if necessary.

The valve seat of the present invention can be manufactured from a slurry containing the above-mentioned materials by ordinary paper-forming means, provided that the sheet thickness is 3 to 7 m711.

In this case, if the sheet thickness deviates from the above range, it tends to be difficult to manufacture the paper container intended by the present invention.

By the way, the valve seat of the present invention is compressed in the pre-pressing process to reduce its thickness by 30 to 50% as described later, so if the thickness of the valve seat is 3r/L1rt or less, the thickness after the pre-pressing Compressed sheets are so thin that they may not be strong enough to withstand searching.

On the other hand, if the thickness of the valve seat is 7 mm or more, the compressed sheet after preliminary pressing will be too thick and the water vapor permeability will be impaired.

Next, each step of manufacturing a paper container from a valve seat will be explained. First, a valve seat with a thickness of 3 to 7 inches is pre-pressed.

This preliminary pressing is a process in which the valve seat is pressed for 2 to 5 seconds at a temperature of 150 to 200°C so that the thickness of the valve seat is reduced by about 30 to 50%. and thermoplastic synthetic resin pulp adhere to each other, giving the valve seat a certain degree of water resistance and boiling resistance.

One of the requirements of the present invention is to suppress the decrease in sheet thickness in the preliminary pressing process to 30 to 50%, and because the preliminary pressing is performed under these conditions, it is possible to suppress the reduction in sheet thickness in the subsequent embossing process. Because the sheet retains sufficient flexibility, it will not be damaged even if it is exposed to excessive force.

Although it is not essential, it is preferable to subject the compressed sheet to steaming treatment after the preliminary pressing in order to impart flexibility and flexibility to the sheet.

The valve seat compressed in the preliminary pressing process is then punched into a size and shape that corresponds to the size and shape of the container to be manufactured.

For example, when manufacturing a pot-shaped container with a bottom diameter of 50 mm and a depth of 55 mm, the above compressed sheet is
Punch out a circular shape of about 80 mm, and make the base 80 m long.
When manufacturing a box-shaped container measuring 130 mm x 130 mm and 40 mm deep, the compressed sheet is punched out into a rectangular shape of about 230 mm with 180 wt%.

In this case, it is preferable that creases and squeeze lines are added to the bent portions and squeezed portions of the punched sheet at the same time as punching.

The die cut sheet is then stamped.

In this embossing process, two punched sheets are pressed at a temperature of 180 to 250°C and a pressure of 10 to 100 kg/crA.
This process involves pressing for ~5 seconds, and through this process, the punched sheet is molded into the desired shape, and at the same time, the thermoplastic synthetic resin pulp and synthetic resin powder in the sheet sufficiently adhere the wood pulp to each other. As a result, finished paper containers have excellent water resistance and boiling resistance.

EXAMPLES An example of manufacturing a valve seat used in the present invention will be shown below, and then examples will be shown to specifically explain the effects of the present invention.

Manufacturing example of valve seat 30 kg of bleached hardwood pulp and 50 kg of bleached softwood pulp were charged into a Hydra pulper with 3000 J of water, and after completely disintegrating, synthetic wood pulp called rSWPJ (manufactured by Mitsui Zeraback Co., Ltd., average fiber length 0.9 20 kg of my company's high-density polyethylene) was added and stirred well.

After that, add rosin sizing agent to ※※1wt based on pulp.
%, polyvinyl chloride powder (passed through 270 meshes) with a degree of polymerization of 1200 was added to the slurry at 5 wt % based on the pulp, and sulfate was added at 3 wt % based on the pulp to adjust the pH of the slurry to 4.5.

Next, water was added until the pulp concentration became 0.8 wt%, and then this pulp slurry was formed into a sheet having the thickness shown in the table below using a valve sheet machine.

Thereafter, the valve seat was dried at a temperature of 95 to 105° C. for 40 minutes, and then preliminary pressed using a flat plate multistage press.

In this preliminary press, the sheet was pressed at 180℃ for 3 seconds while adjusting the sheet thickness to be reduced by 30 to 50%, and after the press was released, the compressed sheet was steam-treated for 2 seconds to produce 3 types of compressed sheets as shown in the table below. I got it.

It was observed that the surface of each compressed sheet was smooth, and that the thermoplastic synthetic resin pulp and synthetic resin powder present on the plane were partially melted and the wood pulps were partially fused together.

EXAMPLE The three types of compressed sheets mentioned above were each punched into predetermined shapes and dimensions, and then box-shaped containers, medical Norbon containers, and pot-shaped containers were each stamp-molded from the three punched sheets.

The container dimensions and embossing molding conditions are shown in the table below.

Next, the performance of the paper container of the present invention produced as described above and the paper container produced by the conventional pulp molding method was compared.

The results are shown in the table below. Note that a container with a thickness of 3.2 mm was used for the conventional pulp molded product.

Claims (1)

[Claims] A pulp mixture of 180 to 50 wt% of wood pulp and 20 to 50 wt% of thermoplastic synthetic resin pulp is blended with 5 to 20 wt% of hot water-insoluble synthetic resin powder and appropriate amounts of sizing agent and sulfuric acid based on the pulp. and make this thickness 3~
A 7-inch valve seat is made, and this valve seat is pre-pressed at a temperature of 150-200°C to a sheet thickness of 30-5mm.
After the reduction is reduced to 0%, this compressed sheet is punched into the desired shape and dimensions, and then the punched sheet is heated at a temperature of 180 to 25%.
A method for producing a paper container having excellent water resistance, boiling resistance, and water vapor permeability, which comprises embossing molding at 0°C and a pressure of 10 to 100 kg/ca.