JP3166763B2 - Foam particle mixed paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-density base paper having excellent heat insulating properties and heat retaining properties, which can be used, for example, for cups of instant noodles and tea, etc. The present invention relates to a sheet made of paper mixed with foam particles that is uniformly dispersed and held. More specifically, the present invention relates to foamed particles produced by blending expandable particles into pulp and making a sheet of paper, and then subjecting the sheet to strict adjustment of the water content before foaming, followed by heating and foaming. Related to mixed paper.

[0002]

2. Description of the Related Art Conventionally, high-molecular polymers such as styrene foam and polyethylene foam have been used for sheets used for food containers, packaging materials, and the like, because of their excellent heat insulation and heat retention properties, moldability, processability, and the like.
It is used in large quantities because it has good impact resistance and is inexpensive.However, due to recent demands for environmental pollution prevention, it has been used to reduce the amount of pollutants and soot that are not easily emitted even if it is naturally decomposed or burned. Conversion is underway. As a method of giving the paper substrate these functions, it is effective to give an air layer close to closed cells to the paper. Conventionally, as a method of giving bubbles close to closed cells to a paper-like base material, a method of providing a coating layer containing hollow capsules, a method of applying foaming capsules and then heating and foaming to reduce the density, a method of foaming There is known a method in which capsules are made together with pulp and foamed on a hot roll of a paper making machine.

[0003] Of these, in order to obtain a foamed paper that is truly effective for heat insulation, a method of applying a foaming agent to a coating layer to form a foamed state in only a part of the layer is more effective than a hollow capsule or foamed foam. It is desirable to mix the capsule with the pulp to distribute the capsule throughout the paper, and to make the entire paper foamed. However, the method of mixing hollow capsules and the like with pulp has a specific gravity difference between the pulp and the hollow capsules, so that it is difficult to make paper uniformly and uniformly, and is not very practical. Japanese Patent Application Laid-Open No. 52-39924 discloses a method for producing a bulky paper by adding a shirasu balloon at the time of papermaking. However, there is a problem that papermaking is difficult because the specific gravity is low and the paper floats on water. Further, as can be seen from the table shown in the examples, the density of the base paper made is 0.37 to 0.67 g / cm ³ , which is still higher than the low density comparable to expanded polystyrene.

On the other hand, Japanese Patent Publication No. 47-24263 discloses a method in which a foamable plastic is mixed with a fiber. As can be seen from Example 1, 6 g of pulp and 30 g of plastic are used. Yes, this is an invention mainly based on foamable plastic, and is different from a sheet mainly using paper. As a method of using the expandable capsule, for example, Japanese Patent Application Laid-Open No. 63-173686 discloses manufacturing a base paper of thermal paper. In this method, the density of the expanded base paper is 0.5 g. / Cm ³ , which proves that the foaming degree is still insufficient to obtain a product having the properties such as the effective heat insulating property and the cushioning property aimed at by the present invention.

[0005] Styrofoam, which is generally used as a heat insulating material, has a small thermal conductivity of about 0.045 w / m / k, but has a density of 0.
The thermal conductivity of 5 g / cm ³ paper was very large at 0.07 w / m / k, which proved to be insufficient as a heat insulating material. Furthermore, Japanese Patent Application Laid-Open No. 55-18116 describes a diaphragm produced by mixing microcapsules. Even with this diaphragm, the density is about 0.5 g / cm ³ , Is not obtained. Therefore, properties such as heat insulating property, heat retaining property, strength, cushioning property and the like are equal to those of expanded polystyrene of 0.1.
Low density paper of 0.3 g / cm ³ is not yet known and its development is desired.

[0006]

An object of the present invention is to provide a low-density body having a density of 0.1 to 0.3 g / cm ³ which is equivalent to that of expanded polystyrene, and has heat insulating properties, heat retaining properties, impact resistance, cushioning properties and the like. The present invention is to provide a foamed particle-mixed paper excellent in the above. Further, the present invention provides a sheet made by mixing foamable particles containing a liquid as a core substance and heat-foaming the sheet under strictly controlled conditions so that the density is 0.1 to 0.3 g / c.
m is ^3, excellent heat insulating property, and to provide a method of making paper with a cushioning property.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a low-density, bulky paper by foaming a sheet made by mixing foamable particles into pulp and heating the resulting sheet. Was heated and foamed at a water content of 65 to 72% to obtain a uniform bulky paper having a density of 0.1 to 0.3 g / cm ³ . The present inventors have conducted intensive studies with a focus on uniformly applying the necessary heat to the sheet before foaming, and as a result, determined the moisture content of the sheet before heating and foaming, the moisture content of the sheet during drying in the case of general papermaking. It has been found that a sheet excellent in uniform foaming properties can be produced by sending the sheet to a dryer with a considerably larger amount.

[0008] The present invention relates to a foam-particle-mixed paper, characterized in that the paper contains foam particles uniformly dispersed and held in a pulp fiber layer. The present invention also relates to a foamed particle-mixed paper which is a uniform and bulky sheet having a density of 0.1 to 0.3 g / cm ³ .

Further, the present invention relates to the above-mentioned foam-particle-mixed paper, which is produced by blending expandable particles with pulp and foaming a sheet made of paper by heating.

Further, the present invention provides a method for producing a sheet obtained by blending foamable particles with pulp and adjusting the water content of the sheet before foaming to 65 to 72%. The present invention relates to a manufactured paper made of foam particles.

Generally, in papermaking, the water content before drying with a dryer is usually as low as possible.
Usually, it is set to 0% or less. However, at this moisture content, good expansion of the expandable particles cannot be obtained. In the case of the foamed particle-mixed sheet of the present invention, when the sheet made from the pulp containing the expandable particles is adjusted to a water content of 65 to 72% and subjected to heat expansion, good expansion of the expandable particles is obtained. . Further, in such a high moisture region, since the bonding between the pulp is not complete, it is unlikely that the expansion of the foam is hindered, and since the pulp fibers can move, the foaming is sufficiently and uniformly performed. It is.

[0012] The method of producing the sheet of the present invention by foaming includes a method of adjusting the water content of the sheet to a predetermined amount and then simultaneously drying the sheet on a drier machine and foaming the sheet. Drying at the temperature of
After that, a method of performing a heat treatment after adjusting the water content to a predetermined amount by rehydrating the water is also possible.

As the pulp used in the present invention, any of those used in ordinary papermaking can be used. For example, wood pulp such as softwood or hardwood chemical pulp or mechanical pulp, waste paper pulp, non-wood natural pulp such as hemp or cotton, polyethylene, polypropylene or the like can be used as a raw material, and synthetic pulp and the like can be used in combination. . Acrylic fiber, rayon fiber,
Various fibers such as organic fibers such as phenol fibers, polyamide fibers, and polyethylene fibers, and inorganic fibers such as glass fibers, carbon fibers, and alumina fibers can be mixed.
However, from the viewpoint of papermaking properties, 50%
The blending of not less than weight% is superior in the formation and strength of the sheet.

The expandable particles used in the present invention are heat-expandable microcapsules in which a low-boiling solvent is encapsulated in microcapsules. These capsules are particles having an average particle size of 5 to 30 μm which expand about 4 to 5 times in diameter and 50 to 100 times in volume when heated at a relatively low temperature of 80 to 200 ° C. for a short time. Examples of low boiling point solvents include volatile organic solvents (swelling agents) such as isobutane, pentane, petroleum ether, hexane, low boiling point halogenated hydrocarbons, and methylsilane, and vinylidene chloride, acrylonitrile, acrylates,
It is wrapped in a thermoplastic resin consisting of a copolymer such as methacrylic acid ester. When heated above the softening point of the microcapsule membrane polymer, the membrane polymer begins to soften and, at the same time, the vapor of the contained expanding agent. Pressure rises,
The membrane expands and the capsule expands. The heat-expandable microcapsules expand at a relatively low temperature and in a short time to form closed cells, can provide a material having excellent heat insulating properties, and are relatively easy to handle. Matsumoto microspheres F-30D and F-30
-30GS, F-20D, F-50D, F-80D (Matsumoto Yushi Seiyaku Co., Ltd.), Expancel WU, DU
(Manufactured by Sweden, and sold by Nippon Philite Co., Ltd.), but are not limited to these. The compounding amount of the expandable particles is 1 to 40 parts, preferably 3 to 20 parts with respect to 100 parts of the pulp fiber. When the amount is 1 part or less, sufficient foaming cannot be obtained, and when the amount is 40 parts or more, from the viewpoint of economy. Not very appropriate.

In addition to the pulp slurry, various anionic, nonionic, cationic or amphoteric retention enhancers, paper-strength enhancers, sizing agents and the like are appropriately selected and used. Specifically, polyacrylamide-based cationic, nonionic,
Anionic and amphoteric resins, polyethyleneimine and its derivatives, polyethylene oxide, polyamine, polyamide, polyamidepolyamine and its derivatives, cationic and amphoteric starch, oxidized starch, carboxymethylated starch, vegetable gum, polyvinyl alcohol, urea formalin resin, Organic compounds such as melamine formalin resin and hydrophilic polymer particles, and aluminum compounds such as sulfuric acid band, alumina sol, basic aluminum sulfate, basic aluminum chloride and basic polyaluminum hydroxide, and further ferrous sulfate and chloride Inorganic compounds such as iron or colloidal silica and bentonite can be used in combination.

Examples of the sizing agent include various sizing agents such as a rosin sizing agent for acidic papermaking, a petroleum resin sizing agent, and an alkylketene dimer sizing agent and alkenyl succinic anhydride sizing agent for neutral papermaking. Can be.

In addition to these, generally known fillers can be mixed. For example, talc, kaolin,
Mineral fillers such as calcined kaolin, clay, diatomaceous earth, heavy calcium carbonate, magnesium carbonate, aluminum hydroxide, titanium dioxide, magnesium sulfate, silica, aluminosilicate, bentonite, and organic materials such as polystyrene particles and urea formalin resin particles And synthetic fillers. Furthermore, papermaking additive aids such as dyes, pH adjusters, slime control agents, defoamers, and tackifiers can also be used depending on the application.

It is also possible to apply starch, polyvinyl alcohol, a surface sizing agent, a pigment, etc. to the sheet surface by a coating method such as a size press or a gate roll on the paper containing the expandable particles of the present invention. . Papermaking is performed using the above constituent materials as main materials, and the target basis weight is 25 to 4
It is appropriately selected within the range of 00 g / m ² .

First, as a first manufacturing method of the present invention,
After forming a sheet in the wire part of the papermaking process, dewatering is performed in the press part. Usually, in order to facilitate subsequent drying, the water content is reduced to about 60% of that of the base paper, but in the present invention, in order to uniformly apply heat to the entire sheet, the water content is reduced by pressing loosely. Adjust to 65-72%. 72
%, It takes too much time to dry the sheet, which is not suitable. Although making the water content as high as 65 to 72% is not the common sense of papermaking, it is essential to uniformly foam the sheet, which is the object of the present invention. Thereafter, the sheet is sent to a dryer part to be dried and foamed. The temperature is preferably in the range of the maximum foaming temperature of the microcapsules ± 30 ° C. For example, in Matsumoto Microsphere F-30D, 13
It is preferably at 0 ± 30 ° C., particularly 110 to 140 ° C.
Desirably, it is in ° C.

In the second production method of the present invention, first, a sheet is formed into a sheet by a wire part in a paper making process, then dehydrated as much as possible to about 60% of normal moisture in a press part, and then in a temperature range where the foaming agent is not foamed. Dry to produce unfoamed base paper. If the water content at this time is in the range of 50 to 5%, there is no problem in production.

Next, the unfoamed base paper is given water again to adjust the water content to 65 to 72%, and then dried by a drier for foaming. In this method, the temperature of the dryer or hot air dryer for producing unfoamed base paper is preferably 40 ° C. or more lower than the maximum foaming temperature of the foaming agent. Is preferably at the maximum foaming temperature ± 30 ° C. For example, when F-30D is used, the temperature is 80 ° C. or less for producing unfoamed base paper and 130 ± 30 ° C. for producing foamed base paper.
Desirably, it is in ° C.

This second manufacturing method is preferable when the speed of the paper machine for making paper is high or the maximum temperature cannot be too high. For the production of foamed base paper mentioned here, the temperature of the dryer is low but the temperature of the dryer is low, such as a Yankee dryer. This is useful because there are advantages such as the use of a paper machine that can be easily raised, and the use of a paper passing line that is designed so that wrinkles do not easily form in the foamed base paper. In any case, in order to effectively produce a low-density foam base paper having a density of 0.1 to 0.3 g / cm ³ of the present invention, the moisture of the base paper entering the foaming dryer is 65 to 72%, It turns out that it is necessary to be higher than usual.

[0023]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted thereto. In the following, all percentages and parts are weight% and parts.

Example 1 Canadian Standard Freeness (CSF) 80% of hardwood bleached pulp (LBKP) beaten to 450 ml and Canadian Standard Freeness (CSF)
SF) Softwood bleached pulp (NBK) beaten to 470 ml
P) 20% of pulp (100 parts) is dispersed in a pulp slurry, and expandable microcapsule particles (Matsumoto Microsphere F-30 manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.)
D, particle diameter 10-20 μm, maximum foaming temperature 130 ° C.) 1
0 parts, dry paper strength enhancer (Polystron 117, manufactured by Arakawa Chemical Industry Co., Ltd.) 0.2 parts, cationized starch (CATO-15, manufactured by Oji National Co., Ltd.) 1.0 part, alkyl ketene dimer sizing agent (Arakawa Chemical Industry Co., Ltd., Size Pine K903) 0.03 part, wet paper strength enhancer (DIC Hercules, Kaimen 557H) 0.4 part were added with good stirring, and the pulp concentration was 0.03%. PH 7.3
To make a base paper. Using the obtained papermaking raw material, a paper having a basis weight of 300 g / m ² was formed using a square hand-made sheet machine (80 mesh) according to a conventional method, and 3 kg was obtained.
/ Cm ² for 1 minute, then sandwiched with filter paper 5kg
Was adjusted and the water content was adjusted to 66% by changing the number of filter papers and the number of rolls used. Thereafter, the sheet was dried twice on the front and back sides with a rotary drier having a surface temperature of 140 to 150 ° C. (manufactured by FCS Corporation, speed 0.36 cm / s) to obtain a sheet. After that, the basis weight, thickness, and density were measured according to JIS, and
The presence or absence of uneven foaming was evaluated by visual inspection.

Example 2 After pressing, foamed paper was prepared in the same procedure as in Example 1 except that the number of filter papers was changed and the water content was adjusted to 70% with a coach roll, and the physical properties were measured.

Comparative Example 1 A foamed paper was prepared in the same procedure as in Example 1 except that the amount of water was adjusted to 60% by a coach roll after changing the number of filter papers after pressing, and the physical properties were measured.

Comparative Example 2 Same as Example 1 except that after the pressing, the moisture content was adjusted to 75% by a coach roll by changing the number of filter papers to be sandwiched, and the paper was passed through a dryer two times on each side for drying. The foamed paper was prepared according to the procedure described above, and the physical properties were measured.

Example 3 A foamed paper was prepared in the same procedure as in Example 1 except that the basis weight was changed to 200 g / m ² , and the physical properties were measured.

Example 4 A foamed paper was prepared in the same manner as in Example 1 except that the basis weight was adjusted to 100 g / m ² and the dried paper was passed through a dryer once, and the physical properties were measured.

Example 5 The basis weight was 100 g / m ² , and the blowing agent to be added was F-20.
D (Matsumoto Microsphere F-20D, manufactured by Matsumoto Yushi-Seiyaku Co., Ltd., particle diameter 10-20 μm, maximum foaming temperature 1
A foamed paper was prepared in the same procedure as in Example 1 except that the temperature was changed to 20 ° C.), and the physical properties were measured.

Example 6 A foamed paper was prepared in the same procedure as in Example 1 except that the basis weight was 100 g / m ² and the amount of the foaming agent was 5 parts, and the physical properties were measured.

Example 7 A foamed paper was prepared in the same procedure as in Example 1 except that the basis weight was 100 g / m ² and the amount of the foaming agent was 15 parts, and the physical properties were measured.

Example 8 A foamed paper was prepared in the same procedure as in Example 1 except that the basis weight was 100 g / m ² and the amount of the foaming agent was 20 parts, and the physical properties were measured.

Table 1 shows the results.

[Table 1]

As is clear from Table 1, the water content was 65%
Below this, the thickness is still insufficient and the density is too high. Further, the unevenness of foaming is so great that a uniform sheet cannot be obtained. When the water content is 75% or more, the thickness and density are sufficient, but drying is not possible unless a large number of passes through a dryer, and therefore, uneven foaming is likely to occur. Therefore, it can be said that the range of 65 to 72% is appropriate for the water content. Further, Examples 4 and 6, 7 and 8 show the difference depending on the concentration of the foaming agent. The more the foaming agent is added, the lower the thickness and the density.

Example 9 In the same manner as in Example 1, after adjusting the amount of water after pressing, an unfoamed base paper was prepared by drying the water with a rotary drier having a surface temperature lowered to about 80 ° C., and then containing water again. To 69%, and subjected to foam drying treatment with a rotary dryer having a surface temperature of 140 ° C. The obtained sheet was measured for basis weight, thickness, and density according to JIS, and evaluated by visual inspection for the presence or absence of uneven foaming.

Comparative Example 3 A foamed base paper was prepared by performing the same treatment as in Example 9 except that the water content after re-hydration was changed to 60%.

Table 2 shows the results.

[Table 2]

In Table 2, the density of each of the examples and comparative examples is in the range of 0.1 to 0.3 g / cm ^3. However, when the completed sheet is the comparative example, there is a lot of uneven foaming and heat is not sufficiently transmitted. It is thought that it was. That is, even when made from unfoamed base paper, it is important that the water content be in the range of 65 to 72%. As is evident from the above results, the present invention was able to significantly improve the foaming properties of the foam particle-mixed paper.

[0040]

According to the present invention, by adjusting the water content of the sheet after pressing to 65 to 72% and then sending it to the drying step, heat can be uniformly transmitted into the sheet. The foamable particles mixed and uniformly dispersed and maintained in the sheet expand and form uniform closed cells, so they have lower density and heat insulation, heat insulation, strength, cushioning, and impact resistance than conventional products. The present invention provides a foamed particle-mixed paper excellent in the above.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-73594 (JP, A) JP-A-50-135183 (JP, A) JP-A-60-59198 (JP, A) 24263 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21H 11/00-27/42

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein the diameter is about 4 to 5 times the volume by heating per 100 parts by weight of a fiber layer containing at least 50% by weight of natural pulp and the balance being fibers selected from synthetic pulp, synthetic fibers and inorganic fibers. Is heated and dried in the drying step simultaneously with the heat-expandable foamable particles, in which 3 to 20 weights of the heat-expandable foamable particles having an average particle size of 5 to 30 μm that expands 50 to 100 times are dispersed. Foamed, uniformly mixed paper with foam particles having a density of 0.1 to 0.3 g / cm ³ . 2. The drying step is characterized in that after adjusting the moisture content of the wet-mixed sheet to a predetermined amount, the sheet is heated and dried on a Yankee dryer and simultaneously foamed with heat-expandable expandable particles. 2. The paper for uniformly mixing foam particles according to claim 1.