JPS604319B2 - Paperboard-like synthetic pulp paper and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a paperboard-like synthetic pulp paper made by mixing thermoplastic synthetic resin-based short fibers with fiber-based fibers, and a method for producing the same.

Many synthetic valve papers, which are made by mixing wood pulp with synthetic resin powder, synthetic fibers, etc., and their manufacturing methods are known, but they have not yet been put into practical use.

Conventional synthetic pulp paper has a thermoplastic synthetic resin exposed on its surface, so it has poor calligraphy and printability, and the effect of gloss processing is not sufficient. In particular, one of the major reasons why conventional synthetic pulp paper has not been put into practical use is that during the manufacturing process of synthetic pulp paper, the wet paper layer spread on felt is compressed and dehydrated using a cylinder or upper felt. As a result, the synthetic resin contained in the wet web layer adheres to the felt surface and stains the felt, making it troublesome to clean, especially when synthetic resin powder is mixed. Also, during drying, if the surface temperature of the dry syringe is raised above the melting point of the synthetic resin, the synthetic resin will become dry syringe. Since the surface of the paper is fused to the surface of the paper, the surface temperature of the drying shilling must be lowered, which slows down the drying speed, and the overall production capacity of the continuous papermaking process is significantly lower than that of conventional pulp paper production. This is because, as a result, there are many disadvantages such as increased manufacturing costs. There are known methods of coating the surface of the drying cylinder with fluororesin, silicone resin, etc. to prevent the adhesion of synthetic resins, but these methods are not sufficient.
In addition, special thin paper (Tokubatsu 1989-1983) is made by heat-pressing and integrating a paper made of a moderate material made of polyolefin-based synthetic polypropylene and an outer layer of two outer layers made of wood bulbs. 155703) is known.

This known special paper uses a mixture of 6% by weight or more of polyolefin synthetic pulp and 4% by weight or less of wood pulp in the middle layer, and the basis weight of the middle layer is 50% by weight or less. Therefore, it is aimed at paper with low moisture permeability and thin thickness. This invention is fundamentally different from the purpose of the above-mentioned known thin paper-like special paper, and the basis weight of the middle layer is large.
The present invention provides a practical paperboard-like synthetic pulp paper with high moisture permeability and high ring crush strength.

That is, this application includes two inventions, and the first invention is a cellulose fiber containing thermoplastic synthetic resin short fibers in an amount of 15% by weight or more and less than 5% by weight and having a basis weight of 150 to 800 y/m.
A second base material layer and an outer surface layer made of fibers having a basis weight of 20 to 50 yen/fiber and formed on at least one side of the base material layer are integrated by pressure heat. The second invention is a paperboard-like synthetic pulp paper having a basis weight of 150 to 800 yen/that is made of cellulose fibers containing thermoplastic synthetic resin staple fibers in an amount of 15% by weight or more and less than 5% by weight. Basis weight 2 made of cellulose fiber on at least one side of the layer
0 to 50 minutes / A method for producing paperboard-like synthetic pulp paper, characterized in that the outer layer is laminated and the laminated sheet is pressurized at a temperature higher than the softening point of the thermoplastic synthetic resin. be. The fiber-based fibers that are the main components of the paperboard-like synthetic pulp paper of this invention are ordinary wood pulp, linter pulp, polynosic short fibers, and other fibers used in the production of conventional pulp paper, such as hemp fibers. Therefore, waste paper pulp can also be used as a raw material.

The thermoplastic synthetic resin short fibers contained in the base material layer of the paperboard-like synthetic pulp paper of this invention include polyethylene, polypropylene, polyethylene terephthalate, polyamide, polyvinyl alcohol, polypynychloride, polystyrene,
It is a synthetic fiber made from thermoplastic synthetic resin such as acrylic resin. The amount of synthetic resin mixed in the base layer is 15% by weight or more and less than 5% by weight based on the total solid content of the base layer. When the amount of synthetic fibers is less than 15% by weight, the effect of mixing synthetic fibers, for example, the improvement of various properties such as the binding properties of fiber-based fibers, wet strength, waterproofness, and physical properties when dry is achieved. If it is not possible and the amount is more than 5% by weight,
Water absorption, air permeability, and moisture permeability are undesirably reduced, and furthermore, the paper quality becomes brittle, causing cracking and cracking, and the folding strength is reduced, causing the properties of synthetic pulp paper to be lost. The basis weight of the base material layer is preferably 150 to 800 m/w, and when used for corrugated board materials, wallpaper, roofing materials, etc., the basis weight is small, and it is used for hot press molding of lunch boxes, etc. In this case, use a large basis weight of about 700 yen/me 4 degrees.

If the basis weight of the base material layer is less than 150 m/m, the strength characteristics of the paperboard-like synthetic pulp paper, such as ring crush strength, will deteriorate and become impractical, and if it exceeds 800 m/m, the paper will not form properly in a normal paper machine. The paper crumbles and becomes difficult to make paper. The outer layer that is laminated onto at least one side of the base material layer is a cellulose fiber layer that does not contain the synthetic fibers, and has a basis weight of 2.
0-50 evening/fu. If the basis weight is less than 20 kg/mt, the synthetic fibers contained in the base layer will ooze out to the outer layer and adhere to the surface of the drying cylinder, and it is operationally difficult to make it thin like this. If the basis weight of the outer layer exceeds 50 m/h, the properties of the synthetic pulp paper will be impaired, particularly the zero wet strength will be reduced. In this invention, in order to combine the outer layer with the base material layer, the green paper layer is formed by normal combining means, and after being dehydrated by pressing it between two felts, it is heated and dried in a drying cylinder. Ru.

Next, the dried sheet is heated and pressurized at a temperature above the softening point of the thermoplastic synthetic resin, preferably above the melting point.

For example, if the synthetic fiber is polyethylene, the heating temperature is preferably 140 to 180°C, the pressure is 20 to 100 kg/ground, and the time is 0.5 to 10 seconds. Each condition is determined by the type of synthetic fiber, the mixing ratio, the synthetic It is appropriately selected depending on the basis weight of the base layer and outer layer of the pulp paper. In addition, when the basis weight of the base material layer is 4 mm, the sheet can be integrated by pressurizing and heating with a part of the heating cylinder in the drying step. In addition, ordinary fillers are added to the base layer and outer layer,
It goes without saying that pigments, sizing agents, paper strength agents, wet reinforcing agents, etc. may be added to the outer layer as appropriate.

The wet strength and surface abrasion properties of the paperboard-like synthetic pulp paper obtained by the method of this invention tend to be lower than those of synthetic pulp paper without an outer layer, but these wet properties have been improved. If necessary, on the surface of the outer layer,
Approximately 10% surface reinforcing agent such as polyethylene, polypropylene, paraffin, polypynyl alcohol, polyvinyl acetate, etc.
% of the aqueous dispersion by a calender method, a size press method, an air knife coater method, etc. at a liquid volume of 5 to 20 days per day, and then dried.

Further, in order to particularly improve the wet strength of the outer layer, a thermosetting resin such as a melamine resin or an epichlorohydrin resin may be added to the fibers of the outer layer.

The above-mentioned outer layer treatment is more effective if both are used together.

According to the method of this invention, since the outer surface layer has a fiber layer containing no synthetic fibers, the synthetic resin in the intermediate layer spills out during the papermaking process and stains the felt, or adheres to the surface of the drying cylinder. There's nothing to do.

Therefore, it is possible to raise the drying temperature to the drying temperature of ordinary pulp paper, and as a result, the papermaking speed is increased, productivity is improved, and it becomes more economical. In addition, this paperboard-like synthetic pulp paper has good printability and calligraphy and drawing properties, and its effects are clearly visible when it is subjected to gloss processing and embossing processing like ordinary pulp paper.

The paperboard-like synthetic pulp paper of this invention has excellent water resistance, greater moisture permeability than conventional synthetic pulp paper, good surface water absorption, good dimensional stability against moisture, and is also strong. Because of its great characteristics, reinforced cardboard,
Packaging fields such as cartons for liquids such as milk and juice, frozen food cartons, containers fields such as trays, tableware, lunch boxes, cup noodle containers, etc., molded products field such as Teesbun Hawk, wallpapers, roofing materials, etc. It can be used in a wide range of fields such as building materials and sterile materials.

The present invention will be specifically explained below using examples.

Example 1 Polyethylene short fibers (manufactured by Mitsui Zerapack Co., Ltd., SWP-E790, softening point 135°C,
A paper with a basis weight of 200 mm was prepared by mixing 3% by weight of the total fiber amount (length 1.6 side), and the paper was exposed on one side and the kraft pulp was combined with different basis weights to make sample pieces. It was created.

This sample piece was coated with a fluorine resin at a temperature of 16
It was heated on a hot plate at 0:00 pm, and a 1.2-thick willow metal plate with a chrome-plated surface was layered on top of it, and after being left for 10 minutes, it was heated to a temperature of 15 mm in diameter and 3.5 mm in weight. A 5K9 metal roll was placed on the top surface of the metal plate and made to reciprocate twice to observe the state of adhesion of the synthetic resin to the metal plate.

. The linear pressure applied to the sample piece in this test was 1.7
It was 5k9/th. In addition, 160 qo of the above sample piece,
Pressure 100k9/ground, after hot pressing for 5 seconds, JI
The ring crush strength after 1 hour of wetness was measured according to the measurement method of S-P8126.

Furthermore, moisture permeability (evening/
〆・24r) was measured. The results of the above tests are shown in Table 1. Table 1 As shown in Table 1 above, if the basis weight of the surface layer is less than 20 mm/kg, resin adhesion to the metal plate will be observed, and if the basis weight of the surface layer exceeds 50 mm/cm, resin adhesion will occur. This is not preferred from a practical point of view since the mechanical strength of the paperboard is rapidly reduced and the properties of paperboard-like synthetic pulp paper are lost.

Example 2 When making paper from the sample piece obtained in the above Example 1 with a basis weight of 30 mm, polyamide, polyamine, and epichlorohydrin resin were added to the pulp paper as a wet reinforcing agent to the pulp paper of the outer layer. Paper was made by mixing 1% by weight of
mixed processing).

Further, the upper surface of the outer surface layer was coated with a water bath liquid (manufactured by Seitetsu Kagaku Co., Ltd., trade name: Zaixen A) containing 10% polyolefin resin as a coating agent at a ratio of 10 liquid/force (coating treatment).

Furthermore, a sample piece was prepared in which the above-mentioned post-treatment was also applied. The ring crush strength of each of the above sample pieces was measured under the same conditions as in Example 1, and the results are shown in Table 2. Table 2 Example 3 A mixture of 8% by weight of bleached kraft pulp and 2% by weight of polyethylene fibers (same as in Example 1) was used as the base layer, and only bleached kraft pulp was used as the outer layer, Using a 6-layer Ultraformer paper machine with a width of 170 mm, the base layer has a basis weight of 290 mm/m, and the outer layer has a basis weight of 30 mm/m on each side. of/minute,
A paperboard-like synthetic pulp paper was produced under the condition that the surface temperature of the drying cylinder was 14,000.

Further, the outer layer of the obtained paperboard-like synthetic pulp paper was subjected to the same coating treatment as in Example 2 by a calendering method. For comparison, the basis weight of only the above intermediate layer without providing an outer layer is 350.
Evening: That paperboard-like synthetic pulp paper was made into sandpaper, but in this case, if the surface temperature of the drying cylinder was increased to 120°C or higher, the synthetic resin would adhere to the surface of the drying cylinder, so the surface temperature of the drying cylinder was lowered to 115qo, and therefore The paper had to be made at a speed of 28 m/min.

Therefore, in Example 3 of this invention, the productivity was approximately three times that of the comparative example, and there was no staining of the felt, and the paper could be made under the same paper-making conditions as ordinary pulp paper. . Table 3 shows the results of measuring the performance of the obtained synthetic pulp. As can be seen in Table 3, the performance of Example 3 without post-treatment is slightly lower but still within the useful range, and the one with post-treatment has slightly improved properties compared to Comparative Example. .

In Table 3, the dry value is the value measured after leaving the sample piece at 20qo and 65% RH for more than two hours, and the wet value is the value measured at 220°C.
The above properties are the values measured after immersion in water for 1 hour.
Measured according to S-P8126.

Also. Water absorption is a value expressed as a percentage of the weight increase after soaking in 20 qo water with respect to the dry weight.
Example 4 Using the same polyethylene fibers (PEF) and bleached kraft pulp (BKP) as in Example 1, the upper and lower outer layers were made of BKP only and had a basis weight of 30 mm, and the upper and lower outer layers were made of BKP and PEF, and the PEF content was reduced. The sheet formed with the base material layer having a changed basis weight of 160 ta' was heated at a temperature of 16,000 and a pressure of 15 k.
9/c and heat treated for 2 minutes to produce paperboard-like synthetic pulp papers with a total basis weight of 220 m/m. The results of measuring the physical properties of these paperboard-like synthetic pulp papers are shown in Table 4 and the graphs in the drawings.

Table 4 In addition, in Table 4, the occurrence of cracks and cracks is shown when a score line is made by pressing the cutting edge on the surface of the sample, the sample is placed on a pending tester, and the sample is bent 180 degrees using the line as a fulcrum. The occurrence of pops and cracks was observed, and those without pops and cracks were marked with ○, those with some cracks were marked with △, and those with pops and cracks were marked with x.

Moreover, the MIT bending strength is a value measured according to JIS-P8115. As can be seen from Table 4 above and the graphs in the drawings, sample No. 1 with a PEF content of 12.5% by weight. 1
Sample No. 1 has a low ring crush strength, especially a dry/wet ratio %, and has a PEF content of 5% by weight or more. 5, 6, and 7, the moisture permeability and MIT bending strength suddenly decreased, and
Cracks occur.

[Brief explanation of the drawing]

The drawing is a graph showing the physical properties of synthetic pulp paper when the synthetic fiber content of the base layer is changed.

Claims (1)

[Claims] 1 15% by weight or more of thermoplastic synthetic resin short fibers, 50% by weight or more
Basis weight 150~ consisting of cellulose fiber containing less than % by weight
A base layer of 800 g/m^2 and an outer layer made of cellulose fibers with a basis weight of 20 to 50 g/m^2, which are laminated on at least one side of the base layer, are integrated by pressure heat. A paperboard-like synthetic pulp paper characterized by: 2 15% by weight or more of thermoplastic synthetic resin short fibers, 50% by weight or more
Basis weight 150~ consisting of cellulose fiber containing less than % by weight
An outer surface layer made of cellulose fiber and having a basis weight of 20 to 50 g/m^2 is laminated on at least one side of a base material layer of 800 g/m^2, and the laminated sheet is heated to the softening point of the thermoplastic synthetic resin. A method for producing paperboard-like synthetic pulp paper, characterized by integrating under pressure at a temperature above.