JP4634080B2 - Molding paper - Google Patents

Description

The present invention relates to excellent thermal formable molded paper processability mainly composed of synthetic pulp and wood pulp. More particularly trays, disposable containers (food, pharmaceutical, cosmetics, toys, etc.) about the thermoformable molding paper used in.

There is known a method for producing a tray, a disposable container (lunch box, folding box, etc.) by compression- molding paperboard mainly made of natural pulp such as white paperboard or chipball. In paperboard by this method, a large elongation paperboard when making the required deep drawn to can not be carried out or to deep-drawn out wrinkles paperboard or broken during molding. The flatness of the flange is poor and the top seal suitability is poor. There are defects such as inferior molding retention compared to plastic. For this reason, it has not been used only in shallow drawing.

This deep drawing process with improved molded, wood pulp paper, and further there is the shaping of synthetic pulp paper under wet conditions. However, the drying process requires time and drying energy, and efficiency and efficiency are poor. On the other hand, in order to obtain a deep-drawn molded product, a method has been developed in which synthetic pulp, natural pulp, or the like is applied to a paper machine and the papermaking screen itself is used as a molded product. However, in this case, a paper machine with a special structure cannot be used for high-speed production, and when changing the shape of the molded product, it is necessary to replace the paper machine screen each time. The problem remains. Various containers are also manufactured by compression molding and injection molding a mixture of synthetic resin and natural pulp, but this container is difficult to call paper and its use is naturally different.

When a high degree of processing is required for paperboard, an appropriate amount of thermoplastic synthetic fiber is blended with the raw material pulp and mixed. Although the paperboard obtained in this case is appropriately thermoplastic, it cannot be removed from the mold by simple hot pressing, and a product cannot be obtained. Therefore, a molded product cannot be obtained unless the paperboard as a material is preheated and softened and then cold pressed. Moreover, a preheating device is indispensable as the processing device, and costs and the number of processes are increased. In addition, many techniques have been disclosed as methods for producing molded paper (see, for example, Patent Documents 1 to 9). Particularly, deep drawability, molding retention characteristics, workability during hot press molding , and flatness of the flange portion. No proposal has been made on a molded paper that is excellent in conformity with the Containers and Packaging Recycling Law. Plastic containers are also used in convenience stores such as pizza and gratin, but there is a strong demand for paper.
Japanese Patent Publication No.51-22512 Japanese Examined Sho 52-21546 JP 52-25107 A JP 52-130772 A Japanese Patent Publication No.53-10622 JP 54-29369 A JP 54-108780 A Japanese Patent Publication No.59-17933 JP 2000-265400 A

An object of the present invention is to produce a molded sheet using a conventional paper machine Upon thermoforming, there are deep drawing suitability and molding retention, excellent workability at the time of hot press forming, opacity, oil resistance Water resistance, flatness of the flange part, excellent top seal suitability, and heat resistant applications, even if a film is applied, the wood pulp compounding ratio is 51% by weight or more, so that it can be used as paper in the container packaging recycling method. The purpose is to provide molded products with high production efficiency.

The present invention aims to solve the above-mentioned problems by paying attention to the above-mentioned problems and repeatedly studying them from the viewpoints of moldability and recyclability.

That is, the present invention is composed mainly of N-BKP (craftwood bleached kraft pulp), thermoplastic synthetic fibers and fillers, and is composed of three layers having a basis weight of 250 g / m ² or more composed of a surface layer, a middle layer and a back layer. In the thermoformed moldable paper, the blending ratio of the thermoplastic synthetic fiber is 20 to 30% by weight in the front layer and the back layer, and 30 to 100% by weight in the middle layer. is only N-BKP, its blending ratio is at 51 percent by weight or more state, and are Stockigt sizing degree not less than 1000 seconds in JIS P 8118, and the thermoplastic synthetic fiber is at the melting point 100 to 180 ° C. It is a multi-branched polyethylene-based synthetic pulp, and the oil repellency (kit No.) of the molded product after thermoforming is 7 or more according to TAPPI practical test method UM557 (1988 version). There relates thermoformable molding paper dynamic contact angle after 1 second when dropped tap water 4μl is characterized der Rukoto than 70 degrees.

  In one advantageous embodiment of the invention, the filler is titanium oxide, calcium carbonate, talc, clay, synthetic zeolite, calcium silicate.

In one advantageous embodiment of the present invention, the center line average roughness of the flange portion of the formed molded article is 20μm or less.

In one preferred embodiment of the present invention, a polyethylene film on the surface layer of the molded sheet, a polypropylene film, a polyester film, polybutylene terephthalate film, laminating with polymethylpentene film.

With such a configuration, it has deep drawing suitability and molding retention, excellent workability during hot press molding , opacity, oil resistance, water resistance, flange flatness, and top seal suitability. it has become possible for the first time to provide a molded paper was.

   Hereinafter, the present invention will be described in detail.

The present invention is a thermoformable molding paper having混抄the filler and wood pulp and thermoplastic synthetic fibers.
(Thermoplastic synthetic fiber)
Examples of the thermoplastic synthetic fibers used in the present invention include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, synthetic fibers such as polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylic ester, and polyacrylonitrile, and these. Mixtures can be used.

These thermoplastic synthetic fibers, the melting point, in the case of molding a molded sheet obtained by hot pressing, Toka not express sufficient thermoplastic in general mold temperature is too high, too low mold It is preferable to keep the shape after molding, and it is preferable that rapid cooling is required and the molding processability is not deteriorated, and it is usually 80 to 200 ° C.
The thermoplastic synthetic fiber in the present invention is more preferably a polyolefin-based synthetic pulp made of polyethylene or polypropylene having a multi-branched fiber property suitable for a wet papermaking process using a general-purpose paperboard machine. In particular, polyolefin-based synthetic pulp having a melting point of 100 to 180 ° C. is preferably used because it is excellent in adhesiveness at the time of heat melting. For example, what is marketed under the trade name of SWP from Mitsui Chemicals, Inc. can be used.

The form of these synthetic fibers may be short fibers or long fibers as long as they can be made by a paper machine, but is preferably within a range of 0.1 to 10 mm. If the thickness is 0.1 mm or less, there is little entanglement between the fibers, and it is difficult to form a sheet substantially. If the thickness is 10 mm or more, it is difficult to form a uniform sheet.
(Wood pulp)
As the wood pulp used in the present invention, wood bleached chemical pulp typified by N-BKP (conifer bleached kraft pulp) is mainly used. If necessary, L-BKP (hardwood bleached kraft pulp), mechanical pulp such as GP, TMP, and BCTMP, and waste paper pulp can be appropriately blended.
(Base paper)
In the multilayer paperboard of the present invention, the blending ratio of the thermoplastic synthetic fiber and the wood pulp is different in the surface layer, the back layer and the middle layer. Proper blending ratio deep drawing suitability and molding retention during thermoforming, is determined while watching the workability.

Blending of the thermoplastic synthetic fiber surface layer, 20-30% by weight in the backing layer, preferably especially from 20 to 25 wt%. If it is 30% by weight or more, it becomes easy to fuse to the mold during thermoforming, and the releasability is poor. In the middle layer, it is 30 to 100% by weight, preferably 40 to 90% by weight, and particularly preferably 45 to 85% by weight. If it is 30% by weight or less, the deep drawability and the mold retention after thermoforming are inferior. Moreover, even if it sticks a film, the mixture rate which makes the mixture rate of a wood pulp 51 weight% or more as a whole layer is preferable.

Surface, the back layer, the basis weight of the middle layer is not particularly limited, each preferably 10 to 300 g / m ^2, as the full thickness is at 250 g / m ² or more, more preferably 300 g / m ² or more It is.

The ratio of the thicknesses of the surface layer, the back layer, and the middle layer is not particularly limited, but the surface layer: middle layer: back layer = 1: 2: 1 to 1: 10: 1 is preferable from the viewpoint of expression that can be thermoformed. .
(Additives such as sizing agents)
In the paper material, paper strength agents, fillers, bands, yield improvers, dyes, fluorescent dyes and the like are appropriately used. As the paper strength agent, cationic starch and polyacrylamide are used.

  As the filler, titanium oxide, calcium carbonate, talc, clay, synthetic zeolite, calcium silicate and the like are used. In particular, titanium oxide is more preferable from the viewpoint of opacity.

  As the yield improver, colloidal silica, polyacrylamide, polyethyleneimine, or the like is used.

As the sizing agent in the paper material, when calcium carbonate is used as a filler, alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), neutral rosin, etc. are used. When a filler other than calcium carbonate is used, In addition, reinforced saponins and saponified rosins are used.
(Manufacturing method of base paper)
The production method of the base paper is not particularly limited, and a base paper is prepared through a press process and a drying process using a known paper machine, that is, a long net, a round net, a hybrid former, a gap former, and the like. In the middle of the process, starch, polyvinyl alcohol, polyacrylic amide using coating equipment such as size press, metering size press, gate roll coater, bar coater, blade coater, air knife coater, curtain coater, rod coater, etc. A coating liquid comprising an acrylic emulsion, a wax emulsion, a fluorine sizing agent alone or a mixture thereof can be applied to the base paper. As an auxiliary agent, a defoaming agent, a water retention agent, a thickening agent, a lubricant, a wetting agent, a release agent, a water resistance agent, a coloring agent, an antiseptic, a fluorescent brightening agent, An antistatic agent, a printability improving agent, or the like is appropriately used. In order to obtain a uniform film, an air knife coater is suitable.

The basis weight of the base paper is not particularly limited but ranges usually about 300 to 400 g / m ^2.

  The drying method after coating is not particularly limited, and examples include the following drying methods, that is, hot air drying, infrared drying, room temperature drying, freeze drying, and the like. From the drying efficiency, infrared drying and hot air drying are preferable. The drying temperature is not particularly limited, but it is generally sufficient to dry at 70 to 150 ° C.

Moreover, after paper coating coating drying, smoothing processing can be performed using a calendar device such as a super calendar, a machine calendar, or a soft calendar.
Example:
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited to these Examples. In the examples, “parts” and “%” represent “parts by weight” or “% by weight” unless otherwise specified.

<Create base paper>
Ingredients for front and back layers:
Based on the pulp slurry solid content, a pulp slurry composed of 20% by weight of polyethylene-based synthetic pulp (trade name: SWP E500, manufactured by Mitsui Chemicals; melting point 135 ° C.) and 80% by weight of Canadian Standard Freeness (CSF) 500 ml of N-BKP As a raw material, 0.8% cationic starch, 5% titanium oxide and 0.3% sizing agent (trade name: SE2360, manufactured by Seiko PMC) were added.

Middle layer ingredients:
Based on the pulp slurry solid content, a pulp slurry comprising 50% by weight of polyethylene synthetic pulp (trade name: SWP E500, manufactured by Mitsui Chemicals; melting point 135 ° C.) and Canadian standard freeness (CSF) 450 ml of N-BKP is 50% by weight. As a raw material, 0.8% cationic starch, 5% titanium oxide and 0.3% sizing agent (trade name: SE2360, manufactured by Seiko PMC) were added.

Using the above raw materials, a base paper having a surface layer basis weight of 70 g / m ² , an intermediate layer basis weight of 170 g / m ² , and a back layer basis weight of 70 g / m ² was made by papermaking and made into a size press having the following composition: A size press treatment was performed using the liquid, and a formed paper having a basis weight of 310 g / m ² was produced.
<Size press liquid formulation>
Polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.) 2 parts, oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) 2.5 parts, water 95.5 parts.

A molded paper of the present invention was obtained in the same manner as in Example 1 except that a base paper having a surface layer basis weight of 100 g / m ² , an intermediate layer basis weight of 170 g / m ² , and a back layer basis weight of 40 g / m ² was made. .

A molded paper of the present invention was obtained in the same manner as in Example 1 except that a laminated paper was obtained by laminating a 20 μm thick polybutylene terephthalate film in Example 1.

Ingredients for front and back layers:
Based on the pulp slurry solid content, a pulp slurry composed of 20% by weight of polyethylene-based synthetic pulp (trade name: SWP E500, manufactured by Mitsui Chemicals; melting point 135 ° C.) and 80% by weight of Canadian Standard Freeness (CSF) 500 ml of N-BKP As a raw material, 5% titanium oxide, 0.3% sizing agent (trade name: Colopearl E-5N, manufactured by Seiko PMC) and 0.3% sulfuric acid band were added.

Middle layer ingredients:
Based on the pulp slurry solid content, a pulp slurry composed of 70% by weight of polyethylene-based synthetic pulp (trade name: SWP E500, manufactured by Mitsui Chemicals; melting point 135 ° C.) and Canadian standard freeness (CSF) 450 ml of N-BKP 30% by weight As a raw material, 5% titanium oxide, 0.3% sizing agent (trade name: Colopearl E-5N, manufactured by Seiko PMC) and 0.3% sulfuric acid band were added.

Using the above raw materials, a base paper weight of 70 g / m ² , a middle layer basis weight of 170 g / m ² , and a back layer basis weight of 70 g / m ² are made using a circular paper machine, and then a size press solution having the following composition is used. A size press treatment was performed to produce a formed paper having a basis weight of 310 g / m ² .
<Size press liquid formulation>
6.5 parts of polyvinyl alcohol (trade name: AP-17, manufactured by Nippon Vinegar Poval), 1.7 parts of polyamide epoxy resin (trade name: SR675A, manufactured by Sumitomo Chemical Co., Ltd.), 91.8 parts of water.
Comparative Example 1:
<Create base paper>
Ingredients for front and back layers:
Based on the pulp slurry solid content, a pulp slurry composed of 10% by weight of polyethylene-based synthetic pulp (trade name: SWP E500, manufactured by Mitsui Chemicals; melting point 135 ° C.) and 90% by weight of Canadian Standard Freeness (CSF) 500 ml of N-BKP As a raw material, 0.3% sizing agent (trade name: Colopearl E-5N, manufactured by Seiko PMC) and 0.3% sulfuric acid band were added.

Middle layer ingredients:
The pulp slurry solid content is based on a pulp slurry composed of 90% by weight of polyethylene-based synthetic pulp (trade name: SWP E500, manufactured by Mitsui Chemicals; melting point 135 ° C.) and Canadian standard freeness (CSF) 450 ml of N-BKP 10% by weight. As a raw material, 0.3% sizing agent (trade name: Colopearl E-5N, manufactured by Seiko PMC) and 0.3% sulfuric acid band were added.

Using the above raw materials, a base paper having a surface layer basis weight of 60 g / m ² , an intermediate layer basis weight of 260 g / m ² , and a back layer basis weight of 30 g / m ² was made by papermaking and made into a size press having the following composition: and papermaking molded paper having a basis weight of 350 g / m ² performs size press treatment using the liquid.
<Size press liquid formulation>
Polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.) 2 parts, oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) 2.5 parts, water 95.5 parts.
Comparative Example 2:
A molded paper was obtained in the same manner as in Example 4 except that the titanium content in Example 4 was changed to 0 part.
Comparative Example 3:
<Create base paper>
Ingredients for front and back layers:
A pulp slurry composed of 40% by weight of polyethylene-based synthetic pulp (trade name: SWP E500, manufactured by Mitsui Chemicals) and 60% by weight of N-BKP with 500 ml of Canadian Standard Freeness (CSF) is sizing based on the solid content of the pulp slurry. (Product name: SE2360, manufactured by Seiko PMC) 0.3% and sulfuric acid band 0.3% were added as raw materials.

Middle layer ingredients:
A pulp slurry comprising 20% by weight of a polyethylene-based synthetic pulp (trade name: SWP E500, manufactured by Mitsui Chemicals) and 450% of Canadian Standard Freeness (CSF) N-BKP by 80% by weight, and a sizing agent (based on the pulp slurry solid content) (Product name: SE2360, manufactured by Seiko PMC) 0.3% and sulfuric acid band 0.3% were added as raw materials.

Using the above raw materials, a base paper having a surface layer basis weight of 70 g / m ² , an intermediate layer basis weight of 170 g / m ² , and a back layer basis weight of 70 g / m ² was made by papermaking and made into a size press having the following composition: A size press treatment was performed using the liquid, and a formed paper having a basis weight of 310 g / m ² was produced.
<Size press liquid formulation>
Polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.) 2 parts, oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) 2.5 parts, water 95.5 parts.
Comparative Example 4:
In Example 4, a base paper having a surface layer basis weight of 50 g / m ² , a middle layer basis weight of 140 g / m ² , and a back layer basis weight of 50 g / m ² was made by combining the base papers, followed by size press treatment using a size press solution having the following composition. Then, a molded paper was obtained in the same manner as in Example 4 except that a molded paper having a basis weight of 240 g / m ² was made.
<Size press liquid formulation>
Polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.) 2 parts, oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) 2.5 parts, water 95.5 parts.

In forming paper obtained in this way, blank physical properties of the molded sheet, the molding processability of a molded sheet was evaluated by the respective following methods, it is shown in Table 1.
[Blank physical properties of the molded paper evaluation]
The physical properties of the blank paper were measured according to JIS and the following method after adjusting the humidity of the molded paper at 23 ° C. and 50% RH.
Basis weight: JIS P 8124.
Thickness and density: JIS P 8118.
Steecht size: JIS P 8122.
[Molding suitability evaluation of the molded paper]
Oiliness (Kit No.): TAPPI practical test method UM557.
Water resistance: With FIBRO 1100 DAT MKII (manufactured by FIBRO), tap water 4.0
The dynamic contact angle after 1 second when μl was dropped was measured.
Resistance to soy sauce: 2 ml of commercially available soy sauce was dropped onto the inner surface of the container after the molding process, and the back-through state after 24 hours was evaluated.
◯: No soaking, soaking but no show-through.
X: There is an inside out and it cannot endure practical use.
Sauce resistance: 2 ml of commercially available seasoning sauce (trade name: Bulldock Worcester sauce; manufacturer: Bulldock Sauce Co., Ltd.) was dropped on the inner surface of the container after the molding process, and the strike through state after 24 hours was evaluated.
○: No soaking. There are no see-throughs.
X: There is an inside out and it cannot endure practical use.
Mold moldability : Using a 30 mm deep tray molding machine, set male and female molds , perform continuous molding at a temperature (145 ± 5) ° C., press pressure 50 kg / cm ² , press time 4 seconds, material destruction, The presence or absence of wrinkles and molding retention were evaluated.
◯: Good, Δ: Slightly inferior, ×: Inferior, not practical.
Mold release properties: The same process as the mold moldability was evaluated releasability from the mold.
◯: Good, Δ: Slightly inferior, ×: Inferior, not practical.
Flatness of the flange portion: The center line average roughness was measured with a universal surface shape measuring device manufactured by Kosaka Laboratory Ltd.
Opacity: The degree of transparency of the flange part, the side part, and the bottom part of the molded product was visually evaluated.
○: No transparency, Δ: Somewhat transparent, ×: Completely transparent and unusable for practical use.

表の結果及び実施例から明らかなように、本発明の成形紙は、木材パルプと熱可塑性合成繊維と填料を主体とした坪量２５０ｇ／ｍ²以上の多層抄き板紙において、木材パルプの配合率が全層として５１重量％以上である熱成形可能な成形紙を製造することにより、深絞り適性及び成形保持性があり、熱プレス成形時の作業性に優れ、不透明性、耐油性、耐水性があり、フランジ部の平坦性が良く、トップシール適性も備えた成形紙を提供することを可能とした。また耐熱用途ではフィルム貼りを行っても木材パルプの配合率を５１重量％以上としたことにより容器包装リサイクル法で紙として扱われる。

As is clear from the results of the table and the examples, the molded paper of the present invention is composed of a wood pulp, a thermoplastic synthetic fiber, and a multilayer paperboard having a basis weight of 250 g / m ² or more mainly composed of a wood pulp, a blend of wood pulp. by rate to produce a thermoformable molding paper is 51 wt% or more as a whole layer, there are deep drawing suitability and molding retention, excellent workability at the time of hot press forming, opacity, oil resistance, water resistance Therefore, it is possible to provide a molded paper having good flatness of the flange portion and having top sealability. In heat-resistant applications, even if a film is attached, the wood pulp is treated as paper by the Containers and Packaging Recycling Law by setting the blending ratio of wood pulp to 51% by weight or more.

  Specifically, in Comparative Examples 1 to 3 not containing a filler, the molding paper is opaque, the blending ratio of the thermoplastic synthetic fiber in the middle layer is 20% by weight, and that of the front and back layers is 40% by weight. Since the blending amount was out of the range of the present invention, the moldability and mold releasability were poor, and the flatness of the flange portion was not measurable. In the case of Comparative Example 4, the soy sauce resistance and the source resistance were very poor and the moldability was insufficient due to the lack of basis weight and paper thickness.

Claims (4)

It is composed mainly of N-BKP (craftwood bleached kraft pulp), thermoplastic synthetic fiber and filler, and is composed of three layers of paper with a basis weight of 250g / m ² or more, consisting of a surface layer, middle layer and back layer. In the possible molding paper, the blending ratio of the thermoplastic synthetic fiber is 20 to 30% by weight in the surface layer and the back layer, and 30 to 100% by weight in the middle layer, and the wood pulp is only N-BKP as the total layer. , and the and the the blend ratio is 51 wt% or more state, and are Stockigt sizing degree not less than 1000 seconds in JIS P 8118, and a multi-branched polyethylene wherein the thermoplastic synthetic fiber is at the melting point 100 to 180 ° C. This is a synthetic pulp, the oil repellency (kit No.) of the molded product after thermoforming is 7 or more according to TAPPI practical test method UM557 (1988 version), and tap water 4 μm Thermoformable molding paper dynamic contact angle after 1 second, characterized in der Rukoto than 70 degrees when dropped. Filler is titanium oxide, calcium carbonate, talc, clay, synthetic zeolite, thermoformable molding sheet according to claim 1, characterized in that the calcium silicate. Claim 1 or 2 thermoformable molding paper, wherein the center line average roughness of the flange portion of the formed molded article is 20μm or less. The thermoformable molding according to any one of claims 1 to 3 , wherein a polyethylene film, a polypropylene film, a polyester film, a polybutylene terephthalate film and a polymethylpentene film are laminated on the surface layer of the molding paper. paper.