JPS6020519B2 - Manufacturing method of cardboard for moisture-proof cartons - Google Patents

Description

[Detailed description of the invention] This invention relates to a method for manufacturing moisture-proof cardboard for cardboard.

BACKGROUND OF THE INVENTION Moisture-proof cardboard for forming packaging containers (cartons) for hygroscopic products such as synthetic detergent powders having a basis weight in the range of 200 to 750 g/m are generally used.

The moisture-proof property required for the material of the above-mentioned packaging container is a moisture permeability value of 100 nights/pillow/2 fly hours or less, and if the moisture permeability is less than this value, hygroscopic products can be stored for a long time. It withstands. In addition, the above moisture permeability is JIS-Z
According to the measurement method of 0208. In addition, in order to form cartons, the ring crush strength is 30k9 or higher, and further improvement is required, and the ring crush strength is 30k9 or higher.
If it is less than 9, it will be difficult to form it with a box machine and the strength as a packaging material will decrease. The above ring crush strength is a value measured after being wet for 1 hour according to the measurement method of JIS-P8126. Conventionally, the above-mentioned moisture-proof material has generally been made by coating the surface of cardboard with thermoplastic synthetic resin or wax, or laminating a plastic film.
Since two steps were required: the step of making cardboard and the step of applying the above-mentioned moisture-proofing treatment to the obtained cardboard, the manufacturing process was complicated and the manufacturing cost was high.

In order to eliminate the above-mentioned drawbacks, the present invention provides a method for producing moisture-proof cardboard for cartons in which moisture-proofing properties are imparted during the papermaking process of the cardboard.

In other words, the present invention provides an intermediate layer containing a thermoplastic synthetic resin having a basis weight of 5 to 35% of the total basis weight, and an intermediate layer containing a thermoplastic synthetic resin having a basis weight of 5 to 35% based on the total basis weight. 2
60 to 750 ta' as paper stock and dry the paper stock at a temperature higher than the softening temperature of the resin, resulting in an IJ of cardboard.
This is a method for producing moisture-proof cardboard for cartons, which is characterized by having a crush strength of 30k9 or more.

The outer layer made of cellulose fibers in this invention is at least two papermaking layers formed by a normal papermaking process using normal wood pulp, linter pulp, wastepaper pulp, polynosic short fibers, hemp fibers, etc. as raw materials. .

The intermediate layer formed between the outer layers is made of a thermoplastic synthetic resin or a thermoplastic synthetic resin mixed with a small amount of cellulose fiber.
Fibrous, granular, powdery, and crushed forms of polyethylene, polypropylene, ethylene/propylene copolymer, ethylene/vinyl acetate copolymer, polyvinyl chloride, polyvinyl alcohol, acrylic resin, polyethylene terephthalate, polyamide, polystyrene, etc. are used.

A small amount of cellulose fibers may be mixed with the resin forming the intermediate layer, and the mixing ratio of the cane fibers varies depending on the pressurizing conditions during drying in the subsequent step. When drying the sandpaper material at the softening temperature of the resin without actively pressurizing it, the proportion of cellulose fibers mixed in the intermediate layer is 2% by weight or less based on the total amount of the intermediate layer, If it exceeds 2% by weight, the desired moisture resistance cannot be obtained even if the basis weight (the amount of resin deposited) of the intermediate layer is increased. In addition, when the paper stock is actively pressurized and dried at a temperature higher than the softening temperature of the resin, the mixing ratio of cellulose fibers can be increased in accordance with the increase in pressurizing pressure, but the desired moisture-proofing In order to obtain the desired properties, the mixing ratio of cellulose fibers in the intermediate layer should not exceed 5% by weight. The basis weight of the thermoplastic synthetic resin of the intermediate layer is 5 to 35% of the total basis weight. The basis weight ratio of the resin can be decreased as the pressure applied during drying increases. Also, under the same drying conditions, as the amount of resin increases, the moisture permeability decreases by 4. Table 1 shows appropriate ranges for the pressure conditions during drying, the basis weight of the outer layer, and the basis weight of the resin of the intermediate layer.

Table 1 Pressure conditions No pressure 1-50k9/ground 50
k9/Lump or above outer layer basis weight (Y/N) 200-6002
15-620225-630 Resin basis weight (evening/final) 50
~12045~10035~90 Furthermore, the relationship between the resin basis weight (Y/N) of the intermediate layer and the moisture permeability is shown in the graph of FIG.

This graph is an example of cardboard (total basis weight 420 ta') in which an intermediate layer made of fibrous low-pressure polyethylene is interposed between an upper layer of bleached graft pulp and a lower layer of waste corrugated paper valves. The dotted line × indicates that the intermediate layer is made of 100% resin and was pressurized at 50k9/ground during drying, and the solid line Y
,Y,,Y2 are not pressurized during drying, Y has 100% resin in the middle layer, and Y,,Y2 has 10% resin in the middle layer, 2
Each of these is a mixture of 0% cellulose fiber. FIG. 2 is a graph showing the relationship between the resin basis weight (high/low) of the intermediate layer and the crush strength (k9).

The middle layer is made of 100% resin, the materials of the upper and lower layers are the same as those shown in FIG. 1 above, and the total basis weight is 360 m/m. The dotted line Xc indicates the case where a pressure of 50 kg' was applied during drying, and the solid line Yc shows the case where no pressure was applied during drying.
As seen in Figure 2, the ring crush strength increases when the intermediate layer resin basis weight exceeds 18 mm/〆 (5%), but when the intermediate layer resin basis weight exceeds 126 mm/〆 (35%) When it exceeds, it descends. The intermediate layer is sandwiched between at least two outer layers, and the upper and lower layers of the outer layer may not have the same basis weight or the same number of layers. The paper stock obtained by combining the intermediate layer and the outer layer is dried at a temperature higher than the softening temperature, preferably higher than the melting point, of the resin contained in the intermediate layer, and the drying temperature varies depending on the type of resin. 140-17 for
0qo is appropriate.

As a pressurizing means during drying, a normal pressurizing means such as a calender roll is applied. For example, in the case of polyethylene, the pressurizing pressure is 20 to 100 k9' and the time is 0.5 to 10 k9'.
A range of seconds is preferable, and the above conditions are appropriately selected depending on the type of resin, the basis weight of the intermediate layer and the outer layer, and the like. It goes without saying that ordinary fillers may be added to the intermediate layer and outer layer, and pigments, sizing agents, paper strength enhancers, wet strength enhancers, etc. may be added to the outer layer as appropriate. The method of the present invention simplifies the process by manufacturing moisture-proof carton cardboard in one process using a normal paper machine, whereas conventional paperboard for moisture-proof cartons is manufactured in two processes: paperboard making and moisture-proofing. , the cost will also be lower.

Moreover, since the outer layer is made of only cellulose fibers, the synthetic resin of the intermediate layer does not leak out during the paper making process and stain the felt or adhere to the surface of the drying cylinder. Therefore, it is possible to raise the drying temperature to the drying temperature of ordinary pulp paper, and therefore the paper making speed can be increased, which improves productivity and becomes economical. In addition, this moisture-proof cardboard for cartons has good printability and calligraphy and drawing properties, and the processing effect is clearly visible when it is subjected to gloss processing or embossing processing like ordinary pulp paper.

Examples of the present invention will be described below.

Example 1 Bleached kraft pulp (measured using C, S.F230 Canadian standard freeness tester) was added to
．． A surface layer with a basis weight of 60 yen/filter added with 3% sizing agent and 0.05% sulfuric acid, and waste paper pulp (C.S.
．． F440') with the same amount of sizing agent as the above surface layer,
Between the back layer of 240 grammage / final layer to which sulfuric acid band was added, % by weight of Kraft Valve 1 and short polyethylene fibers (manufactured by Mitsui Cerapac Co., Ltd., SWP-E400, melting point 131) were added.
℃, length 1.6 sail) 9% by weight and paper weight 100
Sample A was prepared by sandwiching the middle layer (C.S.F700) and drying it at 150° C. for 3 minutes without applying pressure.

In addition, after drying the above-mentioned paper stock at 150q○ for 20 seconds, a pressure of 50k9/cm was applied at the same temperature for 1 second to obtain sample B.
It was created. The properties of the above samples A and B and conventional commercial products C and D are shown in Table 2.

Commercially available products C and D on the top of Table 2 have polyethylene on the back of the cardboard.
After laminating or coating with a thermoplastic synthetic resin such as ethylene or vinyl acetate, a piece of kraft paper of approximately 60 to 80 treads is laminated.

As seen in Table 2 above, the moisture permeability of Samples A and B is as low as that of commercial products C and 0, and the ring lash strength is much greater than that of commercial products C and D.

The above samples A and B and commercially available products C and D all had an air permeability of 180 $ec/100 (JIS-P8117) or higher. Example 2 Using a 6-layer Ultraformer paper machine with a width of 170 mm, the first and second layers were made from exposed kraft pulp, and the third and fourth layers were made from exposed kraft pulp.
A layer of waste paper, a mixed paper of 10% waste paper and 90% polyethylene fiber (same as in Example 1) for the fifth layer, and 6 pieces of waste paper for the sixth layer.
The combined paper stock with a total basis weight of 420 mm and a resin basis weight of the fifth layer of 83 mm/final was sand-formed at a speed of 0 min., and then in a drum dryer with a surface temperature of 140 qo. After drying, it was passed through six stages using the weight of the calender roll (pressure 5k9/volume).

The test results of the obtained cardboard are shown in Table 3. Table 3 The taper stiffness in Table 3 is a value measured according to JIS-P8125, and the ply bond is a value measured using a BRDA type ply bond tester.

Example 3 A laminated paper material obtained by using the raw materials in Example 1 above and varying the total basis weight and the amount of thermoplastic synthetic resin with respect to the total basis weight was dried in 150 qo and 2-calm sand, and then dried at the same temperature. The ring crush strength of each sample obtained by applying pressure of 50k9/water for 1 second is shown in Table 4 and Figure 3.

As seen in Table 4 and Figure 3 above, the total basis weight is 2.
When the ring crush strength is smaller than 60 mm/cane, the ring crush strength does not improve much even if the total basis weight or the resin percentage to the total basis weight increases, but when the total basis weight becomes 260 mm or more, the ring crush strength increases. will improve significantly as the total number of children increases.

This example also shows that the ring crush strength can be adjusted over a wide range by appropriately selecting the total basis weight and the amount of intermediate layer resin. And resin quantity pine. The ring crush strength of the second group of 5% is larger than the ring crush strength of the first group with a small resin content and the third group with a large resin content, and the ring crush strength of the second group with a resin content of 5% is larger than that of the third group with a large resin content. This is almost the same as the relationship with Ngkuratshu strength.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the basis weight of the resin in the intermediate layer and moisture permeability in the present invention, FIG. 2 is a graph showing the relationship between the basis weight of the resin in the intermediate layer and IJ crush strength, and FIG. FIG. 3 is a graph showing the relationship between total basis weight and IJ crush strength in Table 4 of Example 3. Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. An intermediate layer containing a thermoplastic synthetic resin with a basis weight of 5 to 35% of the total basis weight is made of at least two layers made of cellulose fibers.
Between the outer layers of the layers, the basis weight is 260 to 750 g/
Moisture-proofing, characterized in that the laminated paper stock of m^2 is dried at a temperature higher than the softening temperature of the resin, and the resulting cardboard has a ring crush strength of 30 kg or more. Manufacturing method of cardboard for cartons. 2. Mixing 20% by weight or less of cellulose fiber in the middle layer,
A method for producing moisture-proof cardboard for cartons according to claim 1, wherein the drying is performed without applying pressure. 3. Mixing 50% by weight or less of cellulose fiber in the middle layer,
The method for producing moisture-proof cardboard for cartons according to claim 1, wherein the drying is performed under a pressure of 1 kg/cm^2 or more. 4. The method for producing a moisture-proof carton cardboard according to any one of claims 1 to 3, wherein the thermoplastic synthetic resin is polyethylene.