JPH11302991A - Low density paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare low density paper excellent in paper making property and easily controllable in strength and flexibility. SOLUTION: This low density paper contains foamed particles homogeneously dispersed and held in a pulp fiber layer containing curled fibers. The curled fibers are contained in an amount of >=10 wt.% and <=90 wt.% based on the total fiber weight, and the foamed particles are composed of foamed body of heat expandable microcapsules, and the foamed particles are added in an amount of >=1 wt.% and <=20 wt.% based on the total weight of the fibers including the curled fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-density paper mixed with expandable particles, and more particularly to a low-density paper mainly composed of pulp which can be used for various heat insulating materials, cushion materials, wall materials and the like. Things.

[0002]

2. Description of the Related Art Conventionally, polystyrene foam and polyethylene foam have been mainly used as heat insulating materials and cushion materials because of their low cost and good moldability, and high molecular polymers such as vinyl chloride resins have been mainly used as wall materials. However, in order to prevent environmental pollution in recent years, switching to a paper substrate or the like which is not easily disintegrated or emits pollutants and soot even when burned is being promoted.

As a method for imparting the heat insulating property and the cushioning property to the paper base material, it is effective to provide an air layer close to closed cells to the paper. Japanese Patent Publication No. 52-39924 discloses a method of internally adding a shirasu balloon during papermaking.
No. -18116 discloses a method of internally adding expandable microcapsules to paper. However, there is too much difference in specific gravity from pulp, and it is difficult to make paper uniformly and finely. At around 0.5 g / cm ³ , this is not a satisfactory level. Further, Japanese Patent Application Laid-Open No. Hei 5-339898 discloses a method for producing a low-density paper by defining the wet paper moisture of a sheet in which foamable microcapsules are added. However, in order to obtain low-density paper having excellent heat insulating properties and cushioning properties, when foamable microcapsules are used, the amount varies depending on the desired density. It has to be blended to a certain degree, resulting in a significant cost increase. Also, when the amount of the foamable microcapsules is large, it is difficult to foam uniformly, and the uniformity of the density is impaired.

On the other hand, as a method for obtaining low-density paper without using foamable microcapsules, Japanese Patent Application Laid-Open No. 9-41300 describes
Japanese Patent Application Laid-Open Publication No. HEI 9-175556 discloses that a so-called curled fiber in which pulp fibers are curled by a crosslinking agent is blended. In order to reduce the density by blending curled fibers, it is necessary to mainly use curled fibers.However, curled fibers are blended in a large amount because the entanglement between fibers is weak and the water retention is low. Then, not only papermaking becomes difficult, but also sheet strength does not appear. Therefore,
In Japanese Patent Application Laid-Open No. 9-41300, curled fibers are mainly used, and fine fibers are further blended to ensure strength.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a low-density paper which is easy to form, and whose sheet strength and flexibility are easily controlled.

[0006]

SUMMARY OF THE INVENTION The inventor of the present invention has made it easy to form paper and easily control sheet strength and flexibility in developing heat insulating materials, cushioning materials and wall coverings for low-density paper. As a result of intensive studies to obtain low-density paper, it is possible to reduce the amount of curled fiber and the amount of expandable particles by blending expandable particles with pulp fibers containing curled fibers. The present invention has been found that a sufficiently low density can be obtained and that the sheet strength and flexibility can be easily controlled. (1) A low-density paper containing foamable particles uniformly dispersed and held in a pulp fiber layer containing carded fibers. (2) The low-density paper according to (1), wherein the content of the curled fiber is from 10% by weight to 90% by weight based on the total fiber weight. (3) The low-density paper according to (1), wherein the foam particles are foams of thermally expandable microcapsule expandable particles. (4) The low-density paper according to claim 1, wherein the expandable particles are added in an amount of 1% by weight or more and 20% by weight or less based on the total weight of the fibers including the curled fibers.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a low-density paper obtained by mixing pulp fibers containing curled fibers and expandable particles. The curled fiber used in the present invention is
A pulp fiber in which deformation such as curl or twist is fixed by chemical bonding due to an intramolecular cross-linking reaction, and whose apparent length is smaller than that of the original fiber. Known carded fibers can be used. For example, there are a dry crosslinking method, an aqueous solution crosslinking method, and a substantially non-aqueous solution crosslinking method, which are described in U.S. Pat. Nos. 3,224,926, 3,241,553, and 4,033, respectively.
5,147. Formaldehyde and formaldehyde adducts are the most well-known as a cross-linking agent. In addition, C2-C8 dialdehyde and C2-C8 monoaldehyde having an acid functional group are used to cross-link the inside of the cellulosic fiber. (Japanese Patent Publication No. Hei 5-71702). After adding a cross-linking agent to the pulp fiber, mechanical stirring is performed, followed by fluffing and heat treatment, and when the fiber is fixed while being deformed, a curled fiber having a large curl is obtained.

However, in these pulp fibers having cross-linking, the hydroxyl groups (-OH) of cellulose molecules are reduced by the cross-linking treatment, and therefore the hydrophilicity of such fibers is smaller than that of pulp not subjected to the cross-linking treatment. ,
The ability to form interfiber bonds is low, making papermaking difficult.
When the sheet is made of only the curled fiber, the strength after drying is extremely low.

Japanese Patent Application Laid-Open No. 9-41300 specifies the degree of water retention and the degree of curl (wet curl factor) of the curled fiber used. JP-A-9-4130
In the case of Japanese Patent Publication No. 0, since the means for lowering the density is determined only by the blend of the curled fibers, taking into account the balance between the papermaking property and the lowering of the density, the water retention is 25 to 65% and the wet curl factor is 0.5 to 1. .0. However, the densification of the present invention is determined by the combination of the curled fibers and the addition of the expandable particles. Therefore, the physical properties of the curled fiber that can be used are not limited as compared with the case where the low density is expressed only by the curled fiber. Even if the lowering of the density by the carded fiber is somewhat insufficient, the effect can be supplemented by adding the expandable particles. The flexibility of the sheet can be freely controlled by the amount of the curled fiber.

As described above, in the present invention, as a means for reducing the density of the sheet, ordinary wood pulp is mixed together with the curled fiber, and the amount of the curled fiber is reduced by the expandable particles. Has been reinforced.

As ordinary wood pulp, NBKP, L
Non-wood pulp such as BKP, NBSP, LBSP, other wood pulp, linter pulp, hemp pulp, kenaf pulp, bagasse pulp, or fine fibers such as microfibrils may be used. In addition, the curled fiber is not suitable for beating and is preferably used without being beaten, but other pulp can be appropriately selected whether beating or not.

The amount of the curled fiber is preferably from 10% by weight to 90% by weight based on the total fiber weight. If the amount is less than 10% by weight, the effect of reducing the density of the curled fiber is insufficient. If the amount exceeds 90% by weight, not only papermaking becomes difficult, but also the strength of the sheet is hardly exhibited.

[0013] The expandable particles are preferably expanded using thermally expandable microcapsule expandable particles as expandable particles. Some of the thermally expandable microcapsule expandable particles have different optimum expansion temperatures, but may be selected in consideration of the temperature conditions of the paper machine dryer. The addition amount of the expandable particles is 1 to 1 with respect to the total fiber weight including the curled fiber.
20% by weight is preferred. If the amount is less than 1% by weight, the effect of the foam particles generated is insufficient. If the amount exceeds 20% by weight, the cost is increased and the thickness in the width direction is difficult to control.

Examples of the papermaking chemicals include a sizing agent used in ordinary papermaking, a fixing agent thereof, a paper-strengthening agent, and, when an inorganic powder is blended, a retention agent thereof. As the sizing agent, there are internal sizing agents such as alkyl ketene dimer, styrene acrylic resin and rosin. As the fixing agent, a cationic chemical is selected. For example, in the case of neutral papermaking, a polyamide epichlorohydrin resin is used, and in the case of acidic papermaking, a chemical such as a sulfuric acid band is used. As a paper strength agent, there is a polyacrylamide-based paper strength agent. Of course, the present invention is not limited to the chemicals.

A slurry of the raw materials and chemicals comprising the above-mentioned materials is made into a paper by a conventional method. The papermaking may be any of ordinary fourdrinier paper machine, circular net paper machine, short net paper machine, inclined paper machine, various combination paper machine, and the like, and is not particularly limited. The basis weight of the low-density paper is not limited by various uses. Foaming and drying may be performed by any of ordinary multi-cylinder dryers, Yankee dryers, through dryers and the like, and are not particularly limited. However, the higher the dryer surface temperature and hot air temperature, the lower the density tends to be.

The low-density paper thus obtained may be impregnated with various polymer aqueous solutions and coated. The impregnation method may be either ordinary on-machine size press impregnation or off-machine impregnation. As the impregnating chemical, natural or synthetic resins such as starch, polyvinyl alcohol, methylolated melamine, SBR latex, and NBR latex are impregnated to enhance embossability. To impart flame retardancy, a flame retardant such as guanidine phosphate, guanidine sulfate, guanidine sulfamate, ammonium sulfamate, ammonium phosphate, or ammonium sulfate can be impregnated or coated. Further, the impregnation and coating resin are not limited to these, and can be appropriately selected depending on required characteristics.

[0017]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. In the following, “%” indicates “% by weight”.

Example 1 Softwood bleached kraft pulp (30 g) was placed in a 1-liter double-arm kneader (model: S-1, manufactured by Moriyama Seisakusho), and a non-formaldehyde crosslinking agent (trade name: Sumitex NF-) was added. 500K, manufactured by Sumitomo Chemical Co., Ltd.) and its auxiliaries (trademark: Sumitex ACCELATOR X-6)
0, manufactured by Sumitomo Chemical Co., Ltd.) in an amount of 3.0% and 0.25%, respectively, based on the weight of the dried pulp, and then water was added to adjust the solid content to 35%. Each was rotated at 60 rpm and 100 rpm, and a stirring treatment was performed for 20 minutes. Thereafter, the pulp was taken out of the kneader, the pulp was loosened by hand, and then the pulp mass was disintegrated and fluffed with a laboratory Warren blender. Then, the fluffed pulp was put into a blow dryer at a temperature of 150 ° C. After drying for 2 hours in a restrained state, the dried pulp was taken out of the dryer and cooled. Thus, a curled fiber was produced.

This curled fiber 20% and NBKP
40% and LBKP 40% (all unbeaten) were mixed, and expanded as heat expandable microcapsules (EXPAN).
CEL053, manufactured by Nippon Philite Co., Ltd.) was added at 10% based on the total fiber weight, and a papermaking chemical was added at the following absolute dry weight%.
Alkyl ketene dimer (size pine K902, Arakawa Chemical Co., Ltd.) 0.1% as a sizing agent, cationized starch (CP-10A, Daiwa Chemical Industry Co., Ltd.) 0.8% as a fixing agent, poly as a paper strength agent Acrylamide (Polystron 117, manufactured by Arakawa Chemical Industry Co., Ltd.)%, And polyamide resin (Alafixus 125, Arakawa Chemical Industry Co., Ltd.) 0.3% as a wet paper strength agent. From the thus prepared stock, paper having a basis weight of 80 g / m ² was made using a laboratory hand-making machine. Drying was performed at 140 ° C. using a rotary dryer. By drying, the expandable particles were expanded to obtain a low-density paper. The density, tensile strength, and Gurley stiffness of the obtained low-density paper were measured. The papermaking property was evaluated for the quality of wire peeling.

Measurement Method Density: According to JIS P 8118. Tensile strength: according to JIS P 8113. Gurley stiffness: according to TAPPI T543om-94. Papermaking properties were shown by the following four grades. ◎. Peel off cleanly from wire. ：: There is no particular problem although a little fluff remains on the wire. Δ: About 50% of the sheet remains on the wire. ×: not peeled off from the wire

Example 2 Using the curled fiber of Example 1, 80% of curled fiber and 20% of NBKP were mixed to form 3 expandable particles.
A low density paper was obtained in the same manner as in Example 1 except that% was added.

Example 3 50% of the curled fiber of Example 1 and NBKP20
% And LBKP 30% were mixed, and papermaking was performed in the same manner as in Example 1 except that 3% of expandable particles were added to obtain a low-density paper.

Example 4 50% of the curled fiber of Example 1 and NBKP20
% And LBKP 30% (however, NBKP / LBKP was beaten to 450 ml of freeness CSF), and papermaking was performed in the same manner as in Example 1 except that 10% of expandable particles were added to obtain a low-density paper.

Example 5 15% of the curled fiber of Example 1 and NBKP40
%, And LBKP 45% (not beaten), and papermaking was performed in the same manner as in Example 1 except that 15% of expandable particles were added.
A low density paper was obtained.

Comparative Example 1 A low-density paper was obtained by mixing 100% of the curled fiber of Example 1 without blending the expandable particles.

Comparative Example 2 5% of the curled fiber of Example 1, 20% of NBKP,
A low density paper was obtained in the same manner as in Example 1 except that 75% of LBKP was mixed and 10% of expandable particles were added. Table 1 shows the measurement results of the examples and the comparative examples.

[0027]

[Table 1]

As is clear from Table 1, the low-density paper obtained by blending curled fibers and expandable particles within a predetermined range and having good foaming properties has good papermaking properties, low density, and sufficient strength. Further, the flexibility of the paper can be freely controlled by the amount of the curled fiber (Examples 1 to 5).

On the other hand, curled fiber 100%
The low-density paper made in the above, even without blending the expandable particles,
Although the density can be lowered, the papermaking property is poor and the strength is hardly developed (Comparative Example 1). When the amount of the curled fiber is small, the effect of reducing the density by the curled fiber is small, and the sheet becomes hard (Comparative Example 2).

[0030]

As described above, according to the present invention,
The low-density paper obtained by containing the expandable particles in the pulp layer containing the carded fiber has good papermaking properties, the sheet strength and flexibility can be freely controlled, and cushioning materials, heat insulating materials, packaging materials and walls It is possible to provide a low-density paper that can be widely applied to a packaging material.

Claims (4)

[Claims] A low-density paper comprising foam particles uniformly dispersed and held in a pulp fiber layer containing curled fibers. 2. The low-density paper according to claim 1, wherein the content of the curled fiber is from 10% by weight to 90% by weight based on the total fiber weight. 3. The low-density paper according to claim 1, wherein the foam particles are foams of thermally expandable microcapsule expandable particles. 4. The low-density paper according to claim 1, wherein the expandable particles are contained in an amount of 1% by weight to 20% by weight based on the total weight of the fibers including the curled fibers.