JP2003165181A - Biodegradable paper cup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide processed paper for a biodegradable paper cup improved in biodegradability, oil resistance, moistureproof properties and water resistance by the use of a hot-melt adhesive and not generating wrinkles in the surface of the outer layer thereof at the time of molding of the paper cup, and the biodegradable paper cup. <P>SOLUTION: The processed paper for the biodegradable paper cup has layered constitution of inner surface resin layer/paper layer (1)/hot-melt adhesive layer/ paper layer (2). The inner surface resin layer comprises a biodegradable resin, and the hot-melt adhesive layer is constituted of a composition based on the biodegradable resin. The biodegradable paper cup using the same is also disclosed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biodegradable processed paper for paper cups and a paper cup using the same, and more particularly to a paper cup suitable for a cup noodle container.

[0002]

2. Description of the Related Art Conventionally, expanded polystyrene cups and paper cups have been used as containers for cup noodles, but expanded polystyrene cups are not decomposed in the natural world when they are discarded outdoors or when they are landfilled. There is a problem of polluting the environment for a long time. Therefore, in most cases, polystyrene cups are currently incinerated. Further, the paper cup has less problems as compared with the foam polystyrene cup, but has the same problem because low density polyethylene (LDPE) is laminated as a resin layer on the inner surface.

Therefore, there is a strong demand for using a biodegradable resin for the inner resin layer of the paper cup. Properties required for such a processed paper for a paper cup and the resin layer on the inner surface of the paper cup include water resistance, oil resistance, moisture resistance and the like in addition to adhesiveness. However, when a biodegradable resin is used for the inner surface resin layer, a biodegradable resin satisfying all of these properties including adhesiveness is not known. The term "adhesiveness" as used herein means so-called heat sealing suitability, and as described later, when the body portions of the paper cups are joined, the joining is usually performed by heat sealing. Further, the moisture resistance is required to prevent the contents from absorbing moisture due to the permeation of humidity when the contents are dry products, thereby preventing deterioration of taste.

The use of a biodegradable resin for the inner surface resin layer of the paper cup is described in, for example, JP-A-6-62944 and JP-A-2000-109045.
Japanese Patent Application Laid-Open No. 6-62944 discloses a paper cup in which a biodegradable plastic layer made of a microbial-produced polyester or an aliphatic polyester is provided on one or both sides of the paper to prevent decomposition of the resin by heat sealing during cup molding. Have been described. Japanese Unexamined Patent Publication No. 2000-109045 describes a paper cup having water resistance, heat resistance, and biodegradability due to the structure of a water resistant layer made of biodegradable resin / paper / foamed heat insulating layer made of biodegradable resin. There is.

On the other hand, the present inventors considered the use of a biodegradable hot melt adhesive for the paper cup in view of the above-mentioned moisture resistance. This is because the hot melt adhesive is generally composed of rubber resin, wax, tackifier, etc., and it is easy to obtain a layer having high moisture resistance. Biodegradable hot melt adhesives are disclosed in JP-A-5-339557.
JP-A-7-278510, JP-A-10-2516
No. 12 publication.

Japanese Unexamined Patent Publication (Kokai) No. Hei 5-339557 contains polylactic acid or lactic acid and another hydroxycarboxylic acid copolymer and has a melt viscosity of 10 CPS-300 at 180 ° C.-210 ° C.
A 00 CPS homelt adhesive is disclosed. In particular,
It is described that it is suitable for bonding biodegradable plastics,
It is described that it can also be used for bonding paper, cloth, non-woven fabric, glass, aluminum and the like.

Japanese Unexamined Patent Publication (Kokai) No. 7-278510 discloses a biodegradable hot melt adhesive composed of natural rubber, raw rosin and wax, and its applications include paper labels, packaging, bookbinding, plywood and the like. ing.

Japanese Patent Laid-Open No. 10-251612 discloses a hot-melt adhesive containing a thermoplastic resin and a tackifier as main components, and as the thermoplastic resin, an aliphatic dicarboxylic acid (anhydride or ester), an alkyl group or Aliphatic dicarboxylic acid having alkenyl group (anhydride or ester)
And a hot-melt adhesive using an aliphatic polyester reacted with an aliphatic glycol, paper,
It is described that it is suitable for adhering biodegradable resins and the like, and uses such as assembling of packaging packages and adhesives for making food packaging containers are described.

However, if the above-mentioned hot melt adhesive is simply used for the inner resin layer of the paper cup, heat resistance,
There are problems with oil resistance and heat seal strength. Further, even when a hot melt adhesive is used for the outer layer, there are problems in heat resistance and heat seal strength, and there is a problem in that the product value is significantly impaired because it is sticky.

[0010]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above problems, and uses a hot melt adhesive, and has good biodegradability, oil resistance, moisture resistance, and water resistance. An object is to provide a processed paper for a sex paper cup.
Furthermore, another object of the present invention is to provide a processed paper for biodegradable paper cups in which wrinkles do not form on the outer layer surface during molding of the paper cup.

[0011]

The present invention includes the following inventions. (1) A processed paper having a layer structure of inner resin layer / paper layer (1) / hot melt adhesive layer / paper layer (2), wherein the inner resin layer comprises a biodegradable resin and is a hot melt adhesive layer. Is a processed paper for biodegradable paper cups, which is composed of a composition whose main component is biodegradable resin.

(2) The processed paper for biodegradable paper cups according to (1), wherein the biodegradable resin constituting the inner resin layer has a melting point or a flow starting temperature of 140 to 250 ° C.

(3) The composition having a biodegradable resin as a main component used in the hot melt adhesive layer has a flow initiation temperature of 1
It is 45 ° C or lower, and the melt viscosity at 150 ° C is 1-1.
The processed paper for a biodegradable paper cup according to item (1) or (2), which is 00 Pa.S.

(4) The paper layer (1) has a basis weight of 30 to 150 g.
/ M ^2, the basis weight of the paper layer (2) is 150~270g / m ² (1) to (3) a biodegradable paper processing paper cup according to any one of clauses.

The present invention further includes the following inventions. (5) Based on the method specified in JIS Z-0208, the value of the water vapor permeability measured at 40 ° C. and 90% RH is 10
The processed paper for biodegradable paper cups according to any one of the items (1) to (4), which is 0 g / m ² · 24 hours or less.

(6) The biodegradable resin used for the inner resin layer has a viscosity average molecular weight of 5,000 or more (1) to (5).
The processed paper for biodegradable paper cups according to any one of paragraphs.

(7) A paper cup made of the processed paper according to any one of the above items (1) to (6), with the resin layer on the inner surface facing the inner surface.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a processed paper having a layer structure of inner surface resin layer / paper layer (1) / hot melt adhesive layer / paper layer (2), and molding with the inner surface resin layer inside. It is about a paper cup made. It is necessary to use a high molecular weight resin for the inner surface resin layer (hereinafter sometimes referred to as a heat seal layer) in order to impart heat sealability, oil resistance, water resistance, etc., and as a result, the melting point or flow initiation temperature is high. Become. The heat-sealing property here means that heat-sealing can be carried out at an appropriate temperature and the heat-resistant strength of the sealed portion. That is, it is also necessary that the strength of the seal portion does not become weak when hot water of 100 ° C. is put inside the container.

When a resin is selected mainly for its heat-sealing property, it is extremely difficult to select a resin excellent in moisture resistance. Therefore, in the present invention, the hot melt adhesive layer is formed mainly for maintaining the moisture resistance. The adhesive layer also needs to be biodegradable. As described above, according to the present invention, by sharing the roles of the two biodegradable resin layers, the selection range of the resin used for each resin layer is expanded, and as a result, the optimum processed paper can be relatively easily prepared. It becomes possible to manufacture by the manufacturing method. Hereinafter, each configuration of the present invention will be described.

<Regarding Paper> The paper used in the present invention is not particularly limited, but due to the relationship between the cup moldability and the strength, the paper of the paper layer (1) has a base paper size of 30-30.
0 g / m ² , the base paper of the paper of the paper layer (2) has a basis weight of 70 to 300
Those having g / m ² can be used. Further, the total of two sheets can be 100 to 500 g / m ² .

The paper used in the present invention contains natural pulp fibers as a main component, and as the natural pulp,
Wood fibers (chemical pulp, mechanical pulp), non-wood fibers, waste paper pulp and the like are optionally used. Among the wood fibers, the chemical pulp includes kraft pulp that uses caustic soda and sodium sulfide during wood chip cooking,
Examples include sulfite pulp that uses sulfurous acid and hydrogen sulfite. These pulps may be unbleached or bleached. As mechanical pulp, ground wood pulp (GP) obtained by grinding logs with a grinder, refiner ground wood pulp (RGP) obtained by grinding (refining) waste wood from a sawmill, and wood. Thermo-mechanical pulp (TM) obtained by heating and refining chips
P) and the like.

These pulp fibers may be used alone or in combination with 2
It is possible to use more than one kind in combination. If necessary, biodegradable resin fibers can be mixed within the range that does not impair the effects of the present invention. Examples of biodegradable resins that can be used include aliphatic polyester, biodegradable cellulose acetate, polylactic acid, and polycaprolactone.

When the paper used in the present invention is made into paper, a filler, a paper-making chemical and the like may be added if necessary. As paper-making chemicals, sizing agents used in ordinary papermaking,
Examples include paper strength agents and yield improvers. Examples of the sizing agent include alkyl ketene dimer, styrene acrylic resin, rosin and the like. Paper strength agents and yield improvers include polyacrylamide resins, polyamide epichlorohydrin resins, polyethyleneimine and its derivatives, polyethylene oxide, polyamines, polyamides, polyamide polyamines and their derivatives, cationic and amphoteric starch, oxidized starch, carboxymethylated. Organic compounds such as starch, vegetable gum, polyvinyl alcohol, etc., and inorganic compounds such as sulfuric acid band, alumina sol, colloidal silica, bentonite, etc. are used in appropriate combination.

As the filler, talc, kaolin,
Calcined kaolin, clay, diatomaceous earth, heavy calcium carbonate, magnesium carbonate, aluminum hydroxide, titanium dioxide, magnesium sulfate, silica, aluminosilicate, bentonite and other mineral fillers, polystyrene particles, urea formalin resin particles, etc. Fillers and the like can be appropriately selected and used in combination. Further, a papermaking additive such as a dye, a pH adjusting agent, a slime control agent, an antifoaming agent, and a sticky agent can be appropriately used depending on the application.

A slurry of raw materials and chemicals composed of the above materials is made by a conventional method. The papermaking machine may be any of ordinary fourdrinier paper machine, cylinder paper machine, shortnet paper machine, inclined paper machine, various combination paper machines, etc., and is not particularly limited. The drying may be any of the conventional multi-cylinder dryer, Yankee dryer, through dryer, etc., and is not particularly limited. Further, in the present invention, the paper support obtained from the paper making step may be not only a single layer but also a laminated paper having two or more layers.

It is also possible to apply starch, polyvinyl alcohol, various surface sizing agents, pigments and the like to the surface of the sheet by a coating method such as a size press or a gate roll.

<Biodegradable Resin for Inner Surface Resin Layer> As the biodegradable resin used for the inner surface resin layer, polycaprolactone resin, biodegradable cellulose ester resin, polyalkylalkanoate resin, polylactic acid resin , Aliphatic polyester resins, starch resins, polyvinyl alcohol resins and the like. In addition, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid,
Polymers or copolymers such as

As described above, the inner resin layer is required to have heat sealability in addition to water resistance and oil resistance. The body heat seal in cup molding is generally 25
It is carried out by a method in which hot air at 0 ° C. to 300 ° C. is blown to melt the resin to be heat-sealed and the resin is immediately pressed. Therefore, the melting point or flow starting temperature of the inner surface resin is 2
It is preferably 50 ° C. or lower. Also, the sealing strength after sealing is not only adhesive at room temperature, but also needs to be sufficiently strong when hot water at 100 ° C is added. Therefore, the biodegradability used for the inner surface resin layer The melting point or the flow starting temperature of the resin is preferably 120 ° C. or higher. The melting point or the flow starting temperature is 140 to 250.
C., more preferably 140 to 230.degree. Therefore, the biodegradable resin used for the inner surface resin layer in the present invention preferably has a viscosity average molecular weight of 5,000 or more, more preferably 1
It is 10,000 to 1,000,000, most preferably 50,000 to 500,000. The thickness of the inner surface resin layer is about 10 to 100 μm, preferably 1 from the viewpoint of liquid leakage prevention and heat seal strength.
It is about 5 to 50 μm.

The melting point referred to in the present invention means a differential scanning calorimeter (DSC-50 manufactured by Shimadzu Corporation or DS manufactured by Perkin Elmer Co., Ltd.).
It is the peak temperature in the case of showing a clear melting peak when measured at a heating rate of 10 ° C./min in the measurement by C-2 type). In addition, when there is no clear peak or when there is no melting point, the flow starting temperature is adopted instead of the melting point. Flow start temperature is flow tester (Shimadzu CL
T-500 type or CST-500 type), nozzle diameter 1 mm, nozzle length 10 mm, load 30 kg, preheating 6
The temperature is the temperature at which the polymer begins to flow out from the die when measured under the conditions of a temperature rise starting temperature of 50 ° C. and a heating rate of 3 ° C./min.

<Regarding Hot Melt Adhesive Layer> The biodegradable resin composition used in the hot melt adhesive layer of the present invention is basically a base polymer and an adhesive as in the case of a normal hot melt adhesive. It is composed of an imparting agent, and optionally contains a viscosity reducing agent such as wax. The base polymer is a polymer compound that is necessary for maintaining the strength of the moisture-proof layer as a structure and has an appropriate cohesive force, and is a biodegradable resin in the present invention. However, in order to enable hot melt coating, the base polymer itself also needs to be easily softened by heat, and also because the moisture-proof layer is not cracked by the molding process and the moisture-proof property is not lowered, A low softening point is required.

An example of such a biodegradable base polymer is polylactic acid or a copolymer of lactic acid and hydroxycarboxylic acid described in JP-A-5-339557. In addition, natural rubber described in JP-A-7-278510 can be mentioned. Furthermore, JP-A-10
Aliphatic polyesters having a side chain described in JP-A-251612 can be mentioned.

As the aliphatic polyester having a side chain, an aliphatic dicarboxylic acid (anhydride or ester), an aliphatic dicarboxylic acid having an alkyl group or an alkenyl group (anhydride or ester), and an aliphatic glycol are reacted. Aliphatic polyesters may be mentioned. In the above, examples of the aliphatic dicarboxylic acid and the like include succinic acid or its anhydride or its diester, and as the aliphatic dicarboxylic acid having an alkyl group or an alkenyl group, alkylsuccinic acid or alkenylsuccinic acid, or their anhydrides. Or a diester. Examples of the aliphatic glycol include 1,2-ethylene glycol, 1,4-butanediol and 1,6-hexanediol. A specific example is a polyester having an average molecular weight of about 50,000 obtained by polycondensing 60 mol of succinic acid, 40 mol of octenylsuccinic acid and 1,4-butanediol.

The polylactic acid or the copolymer of lactic acid and hydroxycarboxylic acid is preferably a polymer having a molecular weight of 20,000 to 500,000. As the hydroxycarboxylic acid, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid or the like can be used.

Natural rubber is present as rubber particles in the latex obtained from the rubber tree and has a rubber content of 30 to 40.
It is said that the weight% and the particle size are large and are 0.1 to 0.5 μm. The main component of the rubber particles in the latex is cis-1,4-polyisoprene, and the average degree of polymerization is about 5,000, but it is said that the surface of the rubber particles is covered with a phospholipid and protein layer. There is. The natural rubber used as the base polymer of the present invention is obtained by concentrating the latex to a rubber content of about 60% by weight and adding ammonia or the like as a preservative, or separating the rubber particles in the natural rubber latex by coagulating. It is possible to use dried, so-called raw rubber.

The tackifier will be described. The tackifier is also called a tackifier, and it is preferable to use it to enhance hot tackiness during hot melt coating,
At the same time, it also dissolves with the base polymer and acts to reduce the melt viscosity of the entire mixture. In the present invention, when used, it is necessary to use a biodegradable tackifier.
As an example, in the specification of Japanese Patent Application No. 2000-100699 of the present applicant, rosin, terpene, rosin ester, shellac, polyalkylene alkanoate polyol, low molecular weight polycaprolactone diol proposed as a plasticizer for natural rubber biodegradable resin. , Low molecular weight polycaprolactone triol, etc. can be used. Anything else,
Terpene-phenol resin, low molecular weight polylactic acid, etc. can also be used.

The viscosity reducing agent may be added, if necessary, in order to improve the fluidity of the biodegradable resin composition during hot melt coating. As the viscosity reducing agent, a so-called wax can be used, but in the present invention, it is necessary that it is biodegradable, and various plant-based or mineral-based natural waxes can be used. For example, carnauba wax, castor wax, rice wax, paraffin wax, montan wax, microcrystalline wax and the like can be used. In addition, low molecular weight aliphatic polyester, fats and oils such as soybean oil, and low molecular weight polyether can be used. These viscosity reducing agents also contribute to the improvement of moisture resistance.

In the present invention, a natural polysaccharide such as starch or a biodegradable auxiliary agent such as protein may be added in order to assist the biodegradability of the base pomer.

The blending ratio of each of the above-mentioned components differs depending on the material, and therefore cannot be generally stated.
˜500 parts by mass is preferred. Further, it is preferable to add 5 to 50 parts by mass of the viscosity reducing agent to 100 parts by mass of the total of the base polymer, the biodegradable auxiliary and the tackifier. In any case, the biodegradable resin composition for hot melt coating was measured by Brookfield type single cylinder rotational viscometer at 150 according to the measuring method specified in JIS K-6862.
It is preferable to adjust to a range of 0.1 to 1000 Pa.S when measured at ° C. If the viscosity is lower than this range, it may penetrate into the paper excessively to lower the moisture resistance, or stains may be visible on the paper surface. If it is higher than this, it becomes difficult to form a coating film having a uniform thickness. The hot melt coating is usually carried out at about 140 ° C to 250 ° C, but there is a risk of thermal decomposition if the temperature is raised, so that it is possible to start the flow at a temperature of 145 ° C or lower and to coat at 150 ° C is preferable. .

In the present invention, the merit of setting an appropriate viscosity range is related to not only the above-mentioned points but also moisture resistance. Generally, the moisture resistance of the composite paper is considered to depend on the thickness of the resin film, but when the voids of the cellulose fiber are sufficiently filled with the resin, the moisture resistance of the crystal itself of the cellulose fiber is also exerted, and It is possible to obtain a superior moisture-proof property estimated from the moisture-proof layer of Therefore, the viscosity may be selected so that the vicinity of the surface layer of the paper is sufficiently impregnated with the hot melt resin composition.

Further, particles such as pigments or fine fibers may be added to the biodegradable resin composition having the above-mentioned composition. Moisture resistance is improved by their addition, or
Heat resistance of laminated paper is improved. When the above-mentioned particles or fine fibers are organic resins, they must be biodegradable resins. Examples of biodegradable resins include polycaprolactone-based resins, biodegradable cellulose ester resins, polyalkylalkanoate-based resins, polylactic acid-based resins, starch-based resins, polyvinyl alcohol-based resins, and the like. In addition, 3-hydroxybutyric acid, 4-hydroxybutyric acid,
Examples thereof include polymers or copolymers of 3-hydroxyvaleric acid and the like. As biodegradable cellulose ester,
It is desirable to use the cellulose acetate having a degree of acetylation of 30 to 56% disclosed by the present applicant in JP-A-2000-341092.

Examples of the inorganic particles include calcium carbonate, clay, kaolin, silica, aluminum hydroxide, zinc oxide and titanium oxide. Further, in order to further improve the moisture resistance, a tabular pigment is preferable. The tabular pigment preferably has an aspect ratio of 4 or more, and particularly preferably 6 or more. The aspect ratio mentioned here is a value obtained by dividing the average particle diameter by the laser diffraction method by the average plate thickness of the tabular grains. The particle size measurement by the laser diffraction method is made by Shimadzu Corporation "Laser diffraction method particle size distribution measuring device SALD-2
000J ". As such a tabular pigment, kaolin, talc, mica, sericite, aluminum hydroxide and the like are desirable.

<About the coating method> Next, the coating method will be described. The method of the present invention is characterized in that two sheets of paper are laminated with a melted biodegradable resin composition. In the present invention, the temperature of the molten biodegradable resin composition supplied to the paper is preferably in the range of 120 ° C to 300 ° C, more preferably about 140 ° C to 220 ° C, in the so-called hot melt coating range. is there. According to the method of the present invention, the biodegradable resin is melted and applied at a high temperature of, for example, 140 ° C. or higher, so that the resin is completely sterilized and microorganisms that decompose the resin are attached. Never

In the present invention, the device for supplying the molten resin to the paper may be either a roll coater or a die coater. In a die coater, a molten resin film may be supplied between two sheets of paper and pressure-bonded, or a molten resin film may be formed on one sheet of paper and another sheet of paper may be pressure-bonded onto it. It is also possible. With a roll coater, it is rational to form a molten resin film on one sheet of paper and press another sheet of paper on it.

In the die coater, a general method of supplying the molten resin to the die head with a pump or a screw may be adopted. However, it is preferable to reduce the thickness unevenness as much as possible in order to sufficiently exhibit the moisture-proof property with a small amount of coating of an expensive biodegradable resin. A thin, uniform coating also has faster biodegradability. Therefore, the most recommended coater in the method of the present invention is a method having a gear roll in the die and controlling the coating amount by the rotation speed of the gear roll. An example of such a device is the GPD (Gear Pump Die) system of Yuri Roll Machine Co., Ltd.

The biodegradable resin has a risk of being decomposed in the presence of oxidation or water, and in any of the apparatuses, the molten resin contains oxygen and oxygen during melting, transportation to a die, and coating completion. It is preferable to eliminate water vapor as much as possible and create an atmosphere in which nitrogen gas is replaced. In addition, it is preferable to provide a step of defoaming while applying a back pressure in a step of supplying the molten resin to the die head, for example, with a device such as a vent type screw extruder. This is because moisture resistance is impaired if air bubbles remain in the molten resin. According to the above-mentioned GPD system, the above-mentioned nitrogen gas replacement and defoaming can be performed. Therefore, it is preferable to use the GPD system also in this respect. When this system is used, coating can be performed with a considerably high viscosity. Therefore, in some cases, it is possible to apply only the base polymer without using the tackifier and the viscosity additive.

As described above, the moisture permeability is important in the present invention, and the processed paper for biodegradable paper cups of the present invention is
40 according to the method specified in JIS Z-0208
The water vapor transmission rate measured at 90 ℃ and 90% RH is 100g / (m
That it is preferably ^2-24 hours) or less. For that purpose, the rice grammage of the moisture-proof layer is preferably about 10 to 50 g / m ² . According to the above-mentioned GPD system, since it can be applied uniformly without bubbles, the object of the present invention can be achieved even with 10 to 40 g / m ² .

Further, the procedure for making processed paper will be specifically described in relation to the inner surface resin layer. First, a biodegradable resin that serves as a heat-sealing layer is melt-extruded and laminated on the surface of the paper (1) that is inside the paper cup. Next, a hot-melt adhesive containing a biodegradable resin as a main component is melt-coated on the surface of the paper (1) or the paper (2), and the other paper is pressure-bonded to bond the two papers to each other. A processed paper is obtained in which the resin layer / paper layer (1) / hot melt adhesive / paper layer (2) are laminated. Alternatively, the paper (1) and the paper (2) may be laminated with a hot melt adhesive, and the inner surface resin layer may be melt extrusion laminated on the paper (1). In any method, the biodegradable resin film may be laminated on the paper (1) with an adhesive.

It is also possible to further provide a resin layer on the outside of the paper layer (2), perform printing, or provide a print protection layer. At that time, it is preferable that those components are biodegradable as much as possible.

<Regarding Cup Molding> Next, cup molding will be described. When manufacturing a paper cup from processed paper, the side blank and bottom blank punched out from the processed paper are heated by a heating means such as hot air to form the paper layer (1) inside and at the same time, heat seal layer and paper layer ( 2) Heat seal and bond. In this way, oil resistance, moisture resistance,
The paper cup of the present invention having good water resistance and non-sticky surface is obtained.

By the way, when a biodegradable paper cup is produced from a processed paper having a layer structure of inner resin layer / paper layer (1) / hot melt adhesive layer / paper layer (2) with the inner resin layer being the inner surface, Wrinkles may be more wrinkled on the paper layer (2) which is the outer surface of the side blank during the production of the paper cup, which may impair the cosmetic appearance.

In order to explain this problem, the molding of the body of the paper cup will be described below. Molding of the paper cup body is performed after heating the heat-sealed portions on both sides of the side blank obtained by punching the processed paper in a fan shape to 160 ° C. or higher. This is a temperature required to exert the adhesiveness of the heat seal layer having a high melting point or a high flow start temperature, but the hot melt adhesive layer having a relatively low flow start temperature is softened more than the heat seal layer. The body part is molded with the paper layer (1) inside and the side blank wound around the mandrel, and the surface of the outer paper layer (2) moves toward the adhesive part while the molding wings press the surface. Then, the shape of the paper cup is adjusted so that the heat-sealing layer and the heat-sealing portion of the paper layer (2) face each other. Finally, the inner surface resin layer and the outer surface of the paper layer (2) are heat-sealed by pressing from above the heat-sealing portion with a seal bar.

At this time, the paper layer (1) is in contact with the mandrel and is pressed and fixed so that it does not shift, but the surface of the paper layer (2) with which the molding wings come into contact is squeezed by the molding wings. become. There is a gap in the hot melt adhesive layer that is softened by heating,
It is considered that wrinkles are generated on the surface of the paper layer (2) due to the shift at the joint portion of the container where the wing operation ends. Alternatively, when the adhesive portion is pressed by the seal bar, a shift occurs in the softened hot melt adhesive layer, and the paper layer (2)
It is conceivable that wrinkles may occur on the surface of the paper layer (2) due to the deviation of the paper layer from the paper layer (1).

In order to eliminate this wrinkle, the heat sealing temperature may be lowered to such an extent that the biodegradable hot melt adhesive does not melt or soften, but strong adhesion cannot be obtained.
The present inventors have determined that the biodegradable resin used for the hot melt adhesive has a melt viscosity at 150 ° C. of 1 to 1000 Pa.S.
It was found that wrinkles were reduced in the range of. More preferably, it is 5 to 1000 Pa.S. 150 ° C. is a temperature that serves as a standard temperature inside the paper when the resin of the inner surface resin layer is heated and melted to about 140 to 250 ° C. and the inner surface resin layer and the surface of the paper layer (2) are bonded together. Also,
The occurrence of the above-mentioned wrinkles can be reduced by considering the balance between the two papers. That is, the paper layer (1)
Sheet rice basis is 30 to 150 g / m ² of, as the base paper rice basis of the paper layer (2) is that 150~270g / m ^2, to the paper layer (1) the low basis weight than the paper layer (2) Is preferred.

[0054]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

<Example 1> Cup base paper (150 g /
m ² ) on the surface of biodegradable resin of natural rubber 77% (mass%: same below), rosin tackifier (Haritac manufactured by Harima Kasei) 3%, microcrystalline wax 10
%, Natural paraffin wax 10%, hot melt resin composition (viscosity 150 ° C., 5 Pa.S, flow starting temperature 1
10 ° C.) to 160 ° C. and a coating amount of 25 using a gear pump die coater (manufactured by Yuri Roll Machinery Co., Ltd.)
g / m ^{2 After} coating, sandwich cup base paper (15
0 g / m ² ) is attached to the resin layer by pressure bonding to form a paper layer (1) /
A processed base paper in which the hot melt adhesive / paper layer (2) was sequentially laminated was obtained. Polylactic acid-based biodegradable resin (Mitsui Chemicals LACEA, 160 ° C.) was also applied to one surface of this processed base paper.
Was melt-extruded and laminated at 30 g / m ² to obtain a processed paper in which the inner surface resin layer / paper layer (1) / hot melt adhesive / paper layer (2) were sequentially laminated. A side blank and a bottom blank of a container were punched out from this processed paper, and a paper cup (1) was formed inside by a molding machine manufactured by Herraf GmbH (Germany) with the paper layer (1) inside. The molding conditions were such that the side seal portion and the bottom seal portion both had a heating temperature of 300 ° C. (hot air outlet), and the blank surface temperature was approximately 200 ° C. I was able to mold the cup without any particular molding problems. When 100 g of calcium chloride was put in the inside of the paper cup and sealed, the moisture permeability was measured and it was 30 g / m ² . Further, the biodegradability was that it decomposed within 2 months in a well-cultivated field, and the shape of the container was almost not retained.

<Example 2> The same as Example 1 except that the molecular weight of the natural rubber-based biodegradable resin was changed and the viscosity of the hot melt resin composition at flowing temperatures of 120 ° C and 150 ° C was used as 50 Pa.S. A paper cup was obtained in the same manner. I was able to mold the cup without any particular molding problems. When 100 g of calcium chloride was put in the inside of the paper cup and sealed, the moisture permeability was measured and it was 30 g / m ² . Further, the biodegradability was that it decomposed within 2 months in a well-cultivated field, and the shape of the container was almost not retained.

Example 3 Bleached kraft paper (70 g / m ² ) was used as the paper (1), the coating amount of the polylactic acid-based biodegradable resin was 30 g / m ² , and the paper (2) was for sandwiching. A paper cup was obtained in the same manner as in Example 1 except that bleached kraft paper (230 g / m ² ) was used. The shape of the obtained paper cup was extremely good without generation of wrinkles, and when 100 g of calcium chloride was put inside the paper cup and sealed, the moisture permeability was measured and found to be 21 g / m ² . Further, the biodegradability was degraded in 2 months in a well-cultivated field, and the shape of the container was almost not retained.

With respect to the paper cups of the respective examples, the occurrence of wrinkles, biodegradability, and water vapor permeability of the processed paper were evaluated. Occurrence of wrinkles on paper cup: Visual observation. Biodegradability of paper cups: Paper cups were buried in the soil of a field, dug out at regular intervals, and the shape was visually observed. Moisture permeability of processed paper: Measured by the method of JIS Z-0208 and displayed in g / m ² · 24 Hr.

[0059]

The biodegradable paper cup of the present invention has oil resistance,
It is a biodegradable paper cup that has good moisture resistance and waterproof properties and does not have wrinkles on the surface, and is suitable for a wide range of containers such as cup noodles, favorite beverages such as coffee, juice, ice cream, frozen desserts and yogurt. Particularly preferred as a cup noodle container.

Continued front page    F-term (reference) 3E086 AB01 AD06 BA04 BA14 BA15                       BA24 BB71 BB74 BB90 CA01                 4F100 AK01A AK01C BA04 BA07                       BA10A BA10D BA13 CB03C                       DG10B DG10D GB16 JA04A                       JA04C JA06C JA13B JA13D                       JC00A JC00C JL00 JL12C                       YY00A YY00B YY00C YY00D

Claims (5)

[Claims] 1. A processed paper having a layer structure of inner surface resin layer / paper layer (1) / hot melt adhesive layer / paper layer (2),
A processed paper for a biodegradable paper cup in which the inner surface resin layer is made of a biodegradable resin and the hot melt adhesive layer is made of a composition containing the biodegradable resin as a main component. 2. The melting point or flow starting temperature of the biodegradable resin forming the inner surface resin layer is 140 to 250 ° C.
Processed paper for the described biodegradable paper cup. 3. The composition having a biodegradable resin as a main component used in the hot melt adhesive layer has a flow starting temperature of 145.
℃ or less, the melt viscosity at 150 ℃ 1-100
The processed paper for biodegradable paper cups according to claim 1 or 2, which has 0 Pa.S. 4. The paper layer (1) has a basis weight of 30 to 150 g / m 2.
^{2. The} processed paper for a biodegradable paper cup according to any one of claims 1 to 3, wherein the paper layer (2) has a tsubo of 150 to 270 g / m ² . 5. A paper cup made of the processed paper according to any one of claims 1 to 4 with the inner resin layer being on the inner surface side.