阅读说明：本技术 环保纸杯原纸制造方法 (Method for manufacturing environment-friendly paper cup base paper ) 是由 崔益瑄 李学周 卢胤希 金钟洙 于 2020-06-01 设计创作，主要内容包括：本发明涉及一种环保纸杯原纸的制造方法,更详细地,涉及一种环保纸杯原纸的制造方法,其特征在于,通过该方法制造具有优异的热粘附性、耐水性以及抗粘连性且容易再利用、在自然状态下生物降解的环保纸杯原纸。(The present invention relates to a method for producing an environmentally friendly raw cup paper, and more particularly, to a method for producing an environmentally friendly raw cup paper, which is characterized by producing an environmentally friendly raw cup paper having excellent thermal adhesiveness, water resistance, and blocking resistance, and being easily recycled and biodegradable in a natural state.)

1. A method for manufacturing environment-friendly paper cup base paper is characterized by comprising the following steps:

a base paper supply step of supplying base paper from a paper making section; and

a double-coating layer forming step of forming a double coating layer on the base paper by a coating unit after the base paper providing step,

thereby manufacturing the environment-friendly paper cup base paper which has the advantages of heat adhesiveness, water resistance and blocking resistance, is easy to recycle and is biodegradable in a natural state.

2. The method for producing environmentally friendly cupstock paper according to claim 1,

the double coating layer forming step includes:

a first coating layer forming step of forming a first coating layer on one side of the base paper by a first coating unit; and

a second coating layer forming step of forming a second coating layer on the first coating layer by a second coating unit after the first coating layer forming step.

3. The method for producing environmentally friendly cupstock paper according to claim 2,

the first coating layer forming step is a step of applying a first coating layer that imparts thermal adhesiveness and water resistance, and the second coating layer forming step is a step of applying a second coating layer that imparts blocking resistance.

4. The method for producing environmentally friendly Dixie cup base paper according to claim 3,

the first coating layer forming step includes:

a first coating liquid providing step of providing the first coating liquid coated on the base paper by a first coating liquid supply unit.

5. The method for producing environmentally friendly Dixie cup base paper according to claim 4,

providing a first masking liquid in the first masking liquid providing step, the first masking liquid including:

a first resin imparting thermal adhesiveness and water resistance; and

and a first defoaming agent for removing bubbles.

6. The method for producing environmentally friendly Dixie cup base paper according to claim 5,

providing a first masking liquid including a first resin having a glass transition temperature lower than a temperature of a paper cup manufacturing process in the first masking liquid providing step, thereby imparting thermal adhesiveness and water resistance.

7. The method for producing environmentally friendly Dixie cup base paper according to claim 6,

providing a first coating liquid including a first resin in the first coating liquid providing step, the first resin being an aqueous copolymer latex prepared by emulsion polymerization of a monomer mixture including an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and the aqueous copolymer latex including 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating units, and the first resin having a solid content of 46.5 wt%, a glass transition temperature of 3 ℃, and a minimum film forming temperature of 32 ℃.

8. The method for producing environmentally friendly Dixie cup base paper according to claim 5,

in the first coating liquid providing step, a first coating liquid is provided in which 0.002 parts by weight of the first defoaming agent is added based on the first resin.

9. The method for producing environmentally friendly Dixie cup base paper according to claim 4,

the first coating layer forming step includes:

a first coating liquid applying step of applying a first coating liquid on the base paper by a first coating head unit after the first coating liquid supplying step.

10. The method for producing environmentally friendly cupstock paper according to claim 9,

in the first coating liquid coating step, the first coating head unit coats the base paper with more than 7g/m²And less than 18g/m²Coating weight (g/m)²) And coating the first coating liquid.

11. The method for producing environmentally friendly cupstock paper according to claim 10,

the first coating layer forming step includes:

and a first coating liquid drying step of drying the first coating liquid applied to the base paper by a first drying unit after the first coating liquid applying step.

12. The method of producing environmentally friendly cupstock paper according to any one of claims 3 to 11,

the second coating layer forming step includes:

and a second coating liquid supply step of supplying the second coating liquid applied to the first coating layer by a second coating liquid supply unit.

13. The method for producing environmentally friendly cupstock paper according to claim 12,

providing a second masking liquid in the second masking liquid providing step, the second masking liquid including:

a second resin imparting blocking resistance;

the second defoaming agent is used for removing bubbles;

silica, to prevent surface stickiness; and

wetting agent, improving coating coverage.

14. The method for producing environmentally friendly cupstock paper according to claim 13,

providing a second dope containing a second resin having a glass transition temperature higher than a temperature in a paper cup manufacturing process in the second dope providing step, thereby imparting blocking resistance.

15. The method for producing environmentally friendly Dixie cup base paper according to claim 14,

providing a second coating liquid including a second resin in the second coating liquid providing step, the second resin being an aqueous copolymer latex prepared by emulsion polymerization of a monomer mixture including an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and the aqueous copolymer latex including 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating units, and the second resin having a solid content of 45.7 wt%, a glass transition temperature of 22 ℃, and a minimum film forming temperature of 20 ℃.

16. The method for producing environmentally friendly cupstock paper according to claim 13,

in the second coating liquid supply step, a second coating liquid is supplied in which 0.002 parts by weight of the second defoaming agent is added based on the second resin.

17. The method for producing environmentally friendly cupstock paper according to claim 13,

in the second coating liquid supply step, a second coating liquid is supplied in which the silica is charged in an amount of more than 0.05 parts by weight and less than 0.21 parts by weight based on the second resin.

18. The method for producing environmentally friendly cupstock paper according to claim 13,

in the second coating liquid supply step, a second coating liquid is supplied in which the wetting agent is added in an amount of more than 0 part by weight and less than 0.02 part by weight based on the second resin.

19. The method for producing environmentally friendly cupstock paper according to claim 12,

the second coating layer forming step includes:

a second coating liquid applying step of applying a second coating liquid on the first coating layer by a second coating head unit after the second coating liquid supplying step.

20. The method for manufacturing environmentally friendly cupstock paper as claimed in claim 19,

in the second coating liquid coating step, the second coating head unit coats the first coating layer with more than 1g/m²And less than 5g/m²Coating weight (g/m)²) And coating the second coating liquid.

21. The method for manufacturing environmentally friendly Dixie cup base paper according to claim 20,

the second coating layer forming step includes:

and a second coating liquid drying step of drying the second coating liquid coated on the first coating layer by a second drying unit after the second coating liquid coating step.

22. The method for producing environmentally friendly cupstock paper according to claim 1,

the double coating layer forming step includes:

a first coating layer forming step of forming a first coating layer on one side of the base paper by a first coating unit;

a third coating layer forming step of forming a third coating layer identical to the first coating layer on the other side of the base paper by a third coating unit after the first coating layer forming step;

a second coating layer forming step of forming a second coating layer on the first coating layer by a second coating unit after the third coating layer forming step; and

a fourth coating layer forming step of forming a fourth coating layer identical to the second coating layer on the third coating layer by a fourth coating unit after the second coating layer forming step.

Technical Field

The present invention relates to a method for producing an environmentally friendly cupstock paper, and more particularly, to a method for producing an environmentally friendly cupstock paper, which is characterized by producing an environmentally friendly cupstock paper having excellent thermal adhesiveness and blocking resistance, being easily recycled, and being biodegradable in a natural state.

Background

In order to manufacture the paper cup, a process of coating a substance having Barrier (Barrier) characteristics and having thermal adhesiveness (Heat adhesiveness) per se on the surface of paper is required.

The most widely used method for manufacturing the universal paper cup is a method of coating the surface of paper with Polyethylene (PE) melted by T-die treatment (melt).

Polyethylene is the most widely used coating for paper cups, which not only has barrier properties by itself, but also enables thermal adhesion between the coated surface and paper and between the coated surface and the coated surface, and thus has the best properties for manufacturing paper cups.

However, polyethylene is not biodegradable in a natural state, and a separate removal process is required in a Repulping (Repulping) process for reusing pulp used in paper cups, so that more than 90% of paper cups can be discarded without being recycled in practice.

Accordingly, there have been attempts in the related art to manufacture eco-friendly paper cups by coating materials other than polyethylene on paper.

A representative form of the current commercialized environment-friendly paper cup is a coated paper cup using polylactic Acid (PLA). Since polylactic acid is a polymer prepared using raw materials in the nature, not a petroleum-based compound, and is biodegradable under specific conditions, the related industry claims that paper cups manufactured using polylactic acid are environment-friendly paper cups.

However, polylactic acid is a polymer that is not degraded in a natural state but is degraded only under specific conditions, and thus is not generally biodegraded in a landfill state. Further, it is actually more difficult to recover pulp by coating polylactic acid than polyethylene in terms of resource recycling, and thus it is difficult to conclude that the coated paper cup using polylactic acid is an environment-friendly paper cup.

In order to produce an environmentally friendly paper cup, the base paper needs to have recyclability and biodegradability, but if these properties of the base paper are emphasized, the basic water resistance and workability of the paper cup base paper may not be ensured.

Fig. 1 is a view showing a conventional process for manufacturing a paper cup, and referring to fig. 1, in a general process for manufacturing a paper cup, a base paper of a paper cup is cut in accordance with a shape of a developed view of the paper cup, and then, as shown in fig. 1, a side paper S portion forming a side surface of the paper cup among the cut base paper is rolled up as shown in the figure, and then both end portions of the side paper S are adhered together.

In this case, since the coated surface for securing the water resistance of the paper cup is formed on the cupstock paper, the coated surface is adhered to the non-coated surface when the side paper S is rolled up and the end portions are connected, and thus excellent thermal adhesiveness is required between the coated surface and the non-coated surface.

After the side paper S is rolled into a cylindrical shape by adhesion between the coated side and the non-coated side, a base paper B forming the bottom surface of the paper cup is prepared and adhered to the lower portion of the side paper S rolled into a cylindrical shape. In this process, as shown in fig. 2, the base paper B is adhered to the side paper S while being folded, and thus the adhesion between the coated side and the non-coated side and the adhesion between the coated side and the coated side are required to be excellent.

Finally, in order to realize basic characteristics of a paper cup for containing a liquid or the like, it is important to form a coated surface for realizing water resistance on a base paper for the paper cup, and to have excellent thermal adhesiveness between the coated surface and a non-coated surface as well as between the coated surface and the coated surface.

However, as described above, even in the case where excellent thermal adhesiveness is required, excessive thermal adhesiveness may make the paper cup manufacturing process difficult. The reason for this is that, in the process in which the paper cup to which the side surface paper S and the base paper B are adhered is set in a forming die and rotated, and the manufacturing apparatus presses the upper portion of the rotated paper cup to form the curl portion C of fig. 2, if the thermal adhesiveness of the paper cup is higher than the desired thermal adhesiveness, adhesion occurs between the coated surface of the paper cup and the forming die, and after the curl portion C is formed, there may be a case in which the paper cup cannot be separated from the forming die. When a situation occurs in which the paper cup in the manufacturing process cannot be separated from the forming mold in time, the process operation of the curl portion C may be stopped, eventually resulting in a failure of the entire operation process. Also, the raw paper stacked for manufacturing the paper cups may adhere to each other, and when the finished paper cups are stacked, the stacked paper cups may adhere to each other.

Although the prior art using an acrylic copolymer resin easily designs a coating layer having thermal adhesiveness, blocking Resistance (Block Resistance) opposite to the thermal adhesiveness is required in an actual paper cup forming process, and thus it is difficult to satisfy both properties in one layer.

As described above, since the cupstock paper is required to have not only excellent water resistance and oil resistance of the coated surface but also thermal adhesiveness and blocking resistance, it is necessary to provide an environmentally friendly cupstock paper which satisfies these characteristics and has further recyclability and biodegradability. Therefore, it is not easy to produce a base paper satisfying all of the above properties, and there is a problem that when one property is satisfied, the other property is not satisfied.

Due to resource exhaustion, environmental pollution and other reasons, the demand of the related industries on environment-friendly cupstock paper is gradually increasing, but in the past, although the cupstock paper as the environment-friendly cupstock paper is claimed to be reusable, the actual repulping process cannot be smoothly carried out, most of waste cupstocks cannot be degraded even after six months, and in addition, the cupstock paper even has no basic elements which should be possessed by the cupstock paper, so that the applicant of the invention develops the environment-friendly cupstock paper which holds the basic characteristics which should be possessed by the cupstock paper.

Documents of the prior art

(patent document 1) Korean laid-open patent publication No. 10-2016-

Disclosure of Invention

Technical problem to be solved

The present invention has been made to solve the above problems.

An object of the present invention is to provide an environment-friendly cupstock paper which has excellent thermal adhesiveness, water resistance and blocking resistance, is easy to handle, can repulp a used cupstock, and is naturally degradable when exposed to soil or air.

Another object of the present invention is to provide an environment-friendly cupstock paper, which is formed by forming a double coating layer on a base paper, and simultaneously increases thermal adhesiveness between a coated side and the coated side and between the coated side and a non-coated side to secure water resistance, oil resistance, and the like of a cupstock, and increases anti-blocking property between the coated side and the non-coated side to easily remove the cupstock paper from a forming mold during a manufacturing process, or to prevent adhesion between stacked base papers or between finished cupstocks.

Another object of the present invention is to provide an environment-friendly cupstock paper, which is easily formed into a paper cup, does not cause water leakage, etc., has no problems in use because the paper cup is coated to be harmless to the human body, and can be reused even though a used paper cup is not subjected to a separate film removal process.

It is still another object of the present invention to provide an environment-friendly cupstock paper, which is formed by applying a first coating liquid on a base paper to form a first coating layer, thereby securing excellent thermal adhesiveness and water resistance by the first coating layer.

It is still another object of the present invention to provide an environment-friendly cupstock paper, which is formed by applying a second coating liquid on a first coating layer to ensure excellent blocking resistance by the second coating layer.

It is still another object of the present invention to provide an environment-friendly cupstock paper, which is capable of smoothly performing thermal adhesion even at a low temperature by preparing a first coating liquid using a first resin having a relatively low glass transition temperature.

It is still another object of the present invention to add a first defoaming agent to a first resin at the time of preparing a first coating liquid, thereby preventing generation of bubbles and removing bubbles.

Still another object of the present invention is to provide a base paper coated with the first coating liquid in an amount exceeding 7g/m²To prevent the water resistance and oil resistance of the paper cup from being drastically reduced and to make the coating amount of the first coating liquid less than 18g/m²To improve the recyclability of the base paper and to prevent the price of the base paper from increasing due to an increase in the amount of the first coating liquid applied.

It is still another object of the present invention to prepare a second coating liquid using a second resin having a relatively high glass transition temperature and apply the second coating liquid onto the first coating layer to form a second coating layer, thereby improving the blocking resistance of the base paper by the second coating layer.

It is still another object of the present invention to prevent generation of bubbles and remove bubbles by adding a second defoaming agent to the second resin when preparing the second coating liquid.

It is still another object of the present invention to prevent surface stickiness by charging silica at the time of preparing the second coating liquid.

Still another object of the present invention is to prevent the blocking resistance between the coated side and the non-coated side from being rapidly lowered by making the amount of silica to be charged in preparing the second coating liquid to be more than 0.06 parts by weight based on the second resin, and to prevent the thermal adhesiveness between the coated side and the coated side, the thermal adhesiveness between the coated side and the non-coated side, the hot water resistance and the cold water resistance from being out of the normal ranges by making the amount of silica to be less than 0.21 parts by weight based on the second resin.

It is still another object of the present invention to prevent the coagulation of the coating liquid due to the difference in surface tension by adding a wetting agent when preparing the second coating liquid, so that the second coating liquid can be uniformly coated on the entire surface of the first coating layer.

It is still another object of the present invention to prevent the decrease of the blocking resistance between the coated side and the non-coated side by making the amount of the wetting agent to be added at the time of preparing the second coating liquid more than 0 part by weight based on the second resin, and to prevent the decrease of the hot water resistance and the recyclability by making the amount of the wetting agent to be less than 0.02 part by weight based on the second resin, and to prevent the increase of the manufacturing cost due to the addition of the excessive wetting agent.

It is still another object of the present invention to provide a coating amount of the second coating liquid applied to the first coating layer exceeding 1g/m²Preventing the blocking resistance between the coated surface and the non-coated surface from being reduced sharply, and making the coating amount of the second coating liquid less than 5g/m²To prevent the thermal adhesiveness between the coated side and the non-coated side from deviating from the normal range.

It is still another object of the present invention to form a double coating layer including a first coating layer and a second coating layer on only one side of a base paper to reduce the production cost of a cupstock paper.

It is still another object of the present invention to form a double-coated layer including a first coated layer and a second coated layer on both sides of a base paper so that a base paper having a double-coated layer formed on both sides of a base paper can be used in the case where it is important to ensure water resistance and oil resistance of a paper cup.

Still another object of the present invention is to use a base paper having a double coating layer formed only on one side of a base paper as a side paper of a paper cup and use a base paper having a double coating layer formed on both sides of a base paper as a base paper of a paper cup, thereby being capable of producing a paper cup having excellent quality while reducing the production cost of the paper cup.

(II) technical scheme

The present invention is achieved by an embodiment having the following structure to achieve the object of the present invention described above.

According to one embodiment of the present invention, the present invention is characterized by comprising: a base paper supply step of supplying base paper from a paper making section; and a double coating layer forming step of forming a double coating layer on the base paper by a coating unit after the base paper providing step, thereby manufacturing an eco-friendly cupstock paper having thermal adhesiveness, water resistance, and blocking resistance, and being easily recycled, and being biodegradable in a natural state.

According to another embodiment of the present invention, the present invention is characterized in that the double coating layer forming step includes: a first coating layer forming step of forming a first coating layer on one side of the base paper by a first coating unit; and a second coating layer forming step of forming a second coating layer on the first coating layer by a second coating unit after the first coating layer forming step.

According to still another embodiment of the present invention, the invention is characterized in that the first coating layer forming step is a step of applying a first coating layer which imparts thermal adhesiveness and water resistance, and the second coating layer forming step is a step of applying a second coating layer which imparts blocking resistance.

According to still another embodiment of the present invention, the present invention is characterized in that the first coating layer forming step includes a first coating liquid supplying step of supplying the first coating liquid applied to the base paper by a first coating liquid supplying unit.

According to still another embodiment of the present invention, the present invention is characterized in that the first dope is supplied in the first dope supplying step, and the first dope includes: a first resin imparting thermal adhesiveness and water resistance; and a first defoaming agent for removing bubbles.

According to still another embodiment of the present invention, the present invention is characterized in that the first coating liquid including a first resin having a glass transition temperature lower than a temperature of a paper cup manufacturing process is provided in the first coating liquid providing step, thereby imparting thermal adhesiveness and water resistance.

According to still another embodiment of the present invention, the present invention is characterized in that the first coating liquid including a first resin is provided in the first coating liquid providing step, the first resin is an aqueous copolymer latex prepared by emulsion polymerization of a monomer mixture including an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and the aqueous copolymer latex includes 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating units, and the first resin has a solid content of 46.5 wt%, a Glass Transition Temperature (Tg) of 3 ℃, and a Minimum Film Forming Temperature (MFFT) of 32 ℃.

According to still another embodiment of the present invention, the first coating liquid supplying step supplies a first coating liquid in which 0.002 parts by weight of the first defoaming agent is added based on the first resin.

According to still another embodiment of the present invention, the present invention is characterized in that the first coating layer forming step includes a first coating liquid applying step of applying a first coating liquid on the base paper by a first coating head unit after the first coating liquid supplying step.

According to still another embodiment of the present invention, the present invention is characterized in that, in the first coating liquid coating step, the first coating head unit coats the base paper with more than 7g/m²And less than 18g/m²Coating weight (g/m)²) And coating the first coating liquid.

According to still another embodiment of the present invention, the first coating layer forming step includes a first coating liquid drying step of drying the first coating liquid coated on the base paper by a first drying unit after the first coating liquid coating step.

According to still another embodiment of the present invention, the present invention is characterized in that the second coating layer forming step includes a second coating liquid supplying step of supplying a second coating liquid applied to the first coating layer by a second coating liquid supply unit.

According to still another embodiment of the present invention, the present invention is characterized in that the second coating liquid is supplied in the second coating liquid supplying step, and the second coating liquid includes: a second resin imparting blocking resistance; the second defoaming agent is used for removing bubbles; silica, to prevent surface stickiness; and a wetting agent to improve coating coverage.

According to still another embodiment of the present invention, the present invention is characterized in that the second dope containing the second resin having a glass transition temperature higher than a temperature in a paper cup manufacturing process is provided in the second dope providing step, thereby imparting blocking resistance.

According to still another embodiment of the present invention, the present invention is characterized in that the second coating liquid containing a second resin is provided in the second coating liquid providing step, the second resin is an aqueous copolymer latex prepared by emulsion polymerization of a monomer mixture containing an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and the aqueous copolymer latex contains 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating units, and the second resin has a solid content of 45.7% by weight, a glass transition temperature of 22 ℃, and a minimum film forming temperature of 20 ℃.

According to still another embodiment of the present invention, the second coating liquid supplying step supplies a second coating liquid in which 0.002 parts by weight of the second defoaming agent is added based on the second resin.

According to still another embodiment of the present invention, the second coating liquid supplying step supplies the second coating liquid containing the silica in an amount exceeding 0.05 parts by weight and less than 0.21 parts by weight based on the second resin.

According to still another embodiment of the present invention, the second coating liquid is provided in the second coating liquid providing step by adding more than 0 part by weight and less than 0.02 part by weight of the wetting agent based on the second resin.

According to still another embodiment of the present invention, the present invention is characterized in that the second coating layer forming step includes a second coating liquid applying step of applying a second coating liquid on the first coating layer by a second coating head unit after the second coating liquid supplying step.

According to still another embodiment of the present invention, the invention is characterized in that, in the second coating liquid coating step, the second coating head unit coats the first coating layer with more than 1g/m²And less than 5g/m²Coating weight (g/m)²) And coating the second coating liquid.

According to still another embodiment of the present invention, the second coating layer forming step includes a second coating liquid drying step of drying the second coating liquid coated on the first coating layer by a second drying unit after the second coating liquid coating step.

According to still another embodiment of the present invention, the present invention is characterized in that the double coating layer forming step includes: a first coating layer forming step of forming a first coating layer on one side of the base paper by a first coating unit; a third coating layer forming step of forming a third coating layer identical to the first coating layer on the other side of the base paper by a third coating unit after the first coating layer forming step; a second coating layer forming step of forming a second coating layer on the first coating layer by a second coating unit after the third coating layer forming step; and a fourth coating layer forming step of forming a fourth coating layer identical to the second coating layer on the third coating layer by a fourth coating unit after the second coating layer forming step.

(III) advantageous effects

The present invention can obtain the following effects by the above embodiments, the structures, combinations, and use relationships described below.

The invention provides an environment-friendly base paper for paper cups, which has excellent thermal adhesiveness, water resistance and adhesion resistance, thereby having good operability, can repulpe used paper cups, and can be naturally degraded in a state of being exposed to soil or air.

The present invention provides an environment-friendly cupstock paper, which forms an environment-friendly cupstock paper by forming a double coating layer on a base paper, and simultaneously increases thermal adhesion between a coated surface and between the coated surface and a non-coated surface to ensure water resistance, oil resistance and the like of a cupstock, and increases anti-blocking property between the coated surface and the non-coated surface to easily remove the cupstock paper from a forming die during a manufacturing process or prevent adhesion between stacked base papers or between finished cupstocks.

The present invention provides an environment-friendly raw paper for paper cups, which is characterized in that the raw paper is easily formed into paper cups, does not cause water leakage, has no problem in use because the coating of the paper cups is harmless to human bodies, and can be reused even though the used paper cups are not subjected to a separate film removing process.

The present invention provides an environmentally friendly cupstock paper, which forms a first coating layer by coating a first coating liquid on a base paper, thereby ensuring excellent thermal adhesiveness and water resistance by the first coating layer.

The invention provides an environment-friendly cupstock, which forms a second coating layer by coating a second coating liquid on a first coating layer, thereby ensuring excellent anti-blocking performance through the second coating layer.

The present invention provides an environment-friendly cupstock paper, which uses a first resin having a relatively low glass transition temperature to prepare a first coating liquid, thereby enabling smooth thermal adhesion at low temperatures.

The present invention adds a first defoaming agent to a first resin when preparing a first dope, thereby preventing generation of bubbles and removing bubbles.

The invention makes the coating weight of the first coating liquid on the base paper exceed 7g/m²To prevent the water resistance and oil resistance of the paper cup from being drastically reduced and to make the coating amount of the first coating liquid less than 18g/m²To improve the recyclability of the base paper and to prevent the price of the base paper from increasing due to an increase in the amount of the first coating liquid applied.

The present invention prepares a second coating liquid using a second resin having a relatively high glass transition temperature and applies the second coating liquid onto the first coating layer to form a second coating layer, thereby improving the blocking resistance of the base paper by the second coating layer.

The present invention prevents generation of bubbles and removes bubbles by adding a second defoaming agent to the second resin when preparing the second dope.

In the present invention, silica is added to prepare the second coating liquid to prevent the surface from being sticky.

The amount of silica added in the preparation of the second coating liquid is more than 0.06 part by weight based on the second resin to prevent the blocking resistance between the coated surface and the non-coated surface from being rapidly reduced, and the amount of silica is less than 0.21 part by weight based on the second resin to prevent the thermal adhesiveness between the coated surface and the coated surface, the thermal adhesiveness between the coated surface and the non-coated surface, the hot water resistance and the cold water resistance from being out of the normal ranges.

In the present invention, a wetting agent is added in the preparation of the second coating liquid to prevent the coagulation of the coating liquid due to the difference in surface tension, so that the second coating liquid can be uniformly coated on the entire surface of the first coating layer.

The present invention prevents the decrease of the blocking resistance between the coated side and the non-coated side by making the amount of the wetting agent to be added in preparing the second coating liquid more than 0 part by weight based on the second resin, and prevents the decrease of the hot water resistance and the recyclability by making the amount of the wetting agent to be less than 0.02 part by weight based on the second resin, and prevents the increase of the manufacturing cost due to the addition of the excessive wetting agent.

The invention makes the coating weight of the second coating liquid coated on the first coating layer exceed 1g/m²Preventing the blocking resistance between the coated surface and the non-coated surface from being reduced sharply, and making the coating amount of the second coating liquid less than 5g/m²To prevent the thermal adhesiveness between the coated side and the non-coated side from deviating from the normal range.

The present invention forms the double coating layer including the first coating layer and the second coating layer on only one side of the base paper to reduce the production cost of the cupstock paper.

The present invention forms a double-coated layer including a first coated layer and a second coated layer on both sides of a base paper, so that a base paper having a double-coated layer formed on both sides of a base paper can be used in the case where it is important to ensure water resistance and oil resistance of a paper cup.

The present invention uses the base paper having the double coating layer formed only on one side of the base paper as the side paper of the paper cup, and uses the base paper having the double coating layer formed on both sides of the base paper as the base paper of the paper cup, thereby being capable of producing the paper cup having excellent quality while reducing the production cost of the paper cup.

Drawings

Fig. 1 is a diagram illustrating a conventional paper cup manufacturing process.

Fig. 2 is a view showing a cross section of a paper cup.

Fig. 3 is a view illustrating an eco-friendly cupstock paper according to one embodiment of the present invention.

Fig. 4 is a view illustrating an eco-friendly cupstock paper according to another embodiment of the present invention.

Fig. 5 is a view showing a hand sheet manufactured by decomposing a sample of cupstock paper according to an embodiment of the present invention.

Fig. 6 is a view showing handsheets produced by decomposing a sample of cupstock paper coated with Polyethylene (PE).

Fig. 7 is a view showing a hand sheet produced by decomposing a sample of cupstock paper coated with polylactic Acid (PLA).

FIG. 8 is a graph showing the results of the biodegradability test.

Fig. 9 is a view showing a method for manufacturing eco-friendly cupstock paper according to one embodiment of the present invention.

Fig. 10 is a diagram showing a first coating layer forming step of fig. 9.

Fig. 11 is a diagram showing a second coating layer forming step of fig. 9.

Fig. 12 is a view showing a method for manufacturing eco-friendly cupstock paper according to another embodiment of the present invention.

Fig. 13 is a view showing a cupstock paper produced by the production method of fig. 12.

Best mode for carrying out the invention

Hereinafter, preferred embodiments of the eco-friendly cupstock paper and the method for manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions or configurations will be omitted when it is determined that the detailed description does not unnecessarily obscure the gist of the present invention. Unless otherwise defined, all terms used in the present specification have the same meaning as the general meaning of the corresponding terms understood by those of ordinary skill in the art to which the present invention belongs, and if the general meaning conflicts with the meaning of the terms used in the present specification, the definitions used in the present specification are followed.

The environment-friendly raw paper for paper cups 1 of the present invention is used for manufacturing paper cups, and is characterized in that it satisfies the processing characteristics and the use characteristics of raw paper for paper cups, and has recyclability and biodegradability, thereby being environment-friendly. Fig. 3 is a view illustrating an eco-friendly cupstock paper according to an embodiment of the present invention, and referring to fig. 3, the eco-friendly cupstock paper 1 includes a base paper 10 and a double coating layer 30.

The base paper 10 is a base paper forming the double coating layer 30 described later, and may be considered as a generic term for all types of paper that can be used when manufacturing paper cups. The base paper 10 is not limited to any particular paper, but preferably, the base paper 10 has a thickness of 180-²The basis weight of the range, and may be KAce PNC product of korean paper-making company (strain) made using 100% natural pulp containing no fluorescent material.

The double coating layer 30 is formed on the base paper 10, and as shown in fig. 3, the double coating layer 30 may be formed only on one side of the base paper 10, as shown in fig. 4, or may be formed on both sides of the base paper 10. Further, the base paper 1 having the double coating layer 30 formed only on one side of the base paper 10 and the base paper 1 having the double coating layer 30 formed on both sides of the base paper 10 may be separately manufactured, so that the base paper 1 having the double coating layer 30 formed only on one side of the base paper 10 may be used as a side paper of a paper cup, and the base paper 1 having the double coating layer 30 formed on both sides of the base paper 10 may be used as a base paper of a paper cup. The double coating 30 includes a first coating 31 and a second coating 33.

The first coating layer 31 is a coating layer formed on the base paper 10, and may be a coating layer formed on the base paper 10 by applying a predetermined amount of a first coating liquid to the base paper 10. The first coating layer 31 gives the cupped base paper thermal adhesiveness,Water resistance, oil resistance, and the like. The thermal adhesiveness of the first coating layer 31 is preferably such that the thermal adhesiveness temperature between the coated surface and the coated surface is 80 ℃ to 145 ℃, and may preferably be 115 ℃. In addition, the thermal adhesiveness of the first coating layer 31, the thermal adhesiveness temperature between the coated side and the non-coated side may be 90 ℃ or higher and 150 ℃ or lower, and may be more preferably 130 ℃. Such values are derived by experiment 1 described later. The first coating liquid is prepared from a first resin and a first defoaming agent, and the coating amount (g/m) of the first coating liquid coated on the base paper 10²) May preferably exceed 7g/m²And less than 18g/m². The amount of the first coating liquid applied (g/m) will be described in detail later²) The range of (1).

The first resin is an aqueous copolymer latex prepared by emulsion polymerization of a monomer mixture including an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and includes 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating unit, and has a solid content of 46.5 wt%, a Glass Transition Temperature (Tg) of 3 ℃, and a Minimum Film Forming Temperature (MFFT) of 32 ℃. Preferably, the first resin is ACRYCOTE of APEC corporation^TMAPC-200, which may comprise 46-47 wt% of an acrylate copolymer modified polymer resin, 52.9-53.9 wt% of water, and 0.1 wt% of other components.

The glass transition temperature refers to the temperature at which the polymeric material transitions from a rigid glassy state to a rubbery phase when the polymeric material is heated, i.e., the temperature at which the glass transition occurs.

The first resin has a low glass transition temperature, preferably, a glass transition temperature lower than the temperature of the paper cup manufacturing process, and thus the first resin exhibits high thermal adhesiveness (Heat adhesion) but low blocking Resistance (Block Resistance). Therefore, even if the process of manufacturing the paper cup is performed at a low temperature, adhesion may be caused between the forming mold and the base paper for the paper cup, and therefore, there may occur a case where the paper cup in production cannot be separated from the forming mold in time. In addition, the raw paper stacked for manufacturing the paper cups may adhere to each other, and when the finished paper cups are stacked, the stacked paper cups may also adhere to each other.

Accordingly, the present invention provides a cupstock paper 1 in which thermal adhesiveness and water resistance are improved by the first coating layer 31 and blocking resistance is improved by the second coating layer 33 described later.

The first resin exhibits thermal adhesiveness at 80 ℃ or higher and 150 ℃, and is characterized in that the temperature at which the first resin exhibits thermal adhesiveness is higher than the temperature at which the second resin described later exhibits blocking resistance. Preferably, the first resin exhibits thermal adhesiveness at 80 ℃ or higher and 145 ℃ or lower when adhering between the coated side and the coated side, and more preferably, exhibits thermal adhesiveness at about 115 ℃. In addition, the first resin exhibits thermal adhesiveness at 90 ℃ or higher and 150 ℃ or lower, and more preferably, at about 130 ℃ when adhering between the coated side and the non-coated side.

The first defoaming agent is used to prevent generation of bubbles and remove bubbles, and when the amount of the first resin is set to 1, the input amount of the defoaming agent may be preferably 0.002 parts by weight. More preferably, the first defoaming agent is a silicone-based defoaming agent mainly composed of Polydimethylsiloxane (PDMS) produced by Saehan silica chemical co., Ltd., korea, and may be a white suspension having a solid content of 38 wt% and a pH of about 7.0. More preferably, the first antifoaming agent may be FD-330 of stejohnchol chemical, which comprises 1-5 wt% of SORBITAN MONOSTEARATE (SORBITAN monostate), 30 wt% of Polydimethylsiloxane (polydimethysiloxane), 55-65 wt% of WATER (WATER), 1 wt% of SODIUM carboxymethylcellulose (SODIUM carboxymethylcellulose), and 5-10 wt% of SORBITAN octadecatrienate poly (oxo-1, 2-ethylene) derivative (SORBITAN, Trioctadecanoate, poly (oxy-1, 2-ethanodidiyl) derivs).

The second coating layer 33 is a coating layer formed on the first coating layer 31,and the second coating layer 33 may be a coating layer formed on the first coating layer 31 by applying a predetermined amount of a second coating liquid onto the first coating layer 31. Blocking resistance is imparted to the cupstock paper by the second coating layer 33. For the blocking resistance of the second coating layer 33, the thermal adhesion temperature between the coated side and the non-coated side may be preferably 90 ℃ or more and 120 ℃ or less, and may be more preferably 100 ℃. Such values are derived by experiment 1 described later. The second coating liquid is prepared from a second resin, a second defoaming agent, silica and a wetting agent, and the coating amount (g/m) of the second coating liquid applied onto the first coating layer 31²) May preferably exceed 1g/m²And less than 5g/m². The coating amount (g/m) of the second coating liquid will be described in detail later²) The range of (1).

The second resin is an aqueous copolymer latex which is prepared by emulsion polymerization of a monomer mixture containing an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and contains 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating unit, and has a solid content of 45.7 wt%, a glass transition temperature of 22 ℃, and a minimum film-forming temperature of 20 ℃. Preferably, the second resin is ACRYCOTE of APEC corporation^TMAPC-0829, which may comprise 45-47 wt% of an acrylate copolymer (Acrylic ester copolymer), 53-55 wt% of water, and 0.1 wt% of other components.

The second resin has a relatively higher glass transition temperature than the first resin, preferably, a glass transition temperature higher than a temperature of a manufacturing process of a paper cup, and thus the second resin is characterized by being excellent in blocking resistance. Therefore, with the second resin, adhesion between the cupstock paper and the forming die is not easily caused at low temperature, and adhesion between stacked cupstock paper or between stacked cups to each other can be prevented, and adhesion performance is exhibited only at high temperature such as high frequency adhesion or thermal adhesion.

The second coating liquid containing the second resin is applied to the first coat layer 31, and thus, when the second coat layer 33 is formed, the cupstock paper 1 excellent in thermal adhesiveness, water resistance, oil resistance, and blocking resistance can be provided.

The second resin exhibits blocking resistance at 80 ℃ or higher and 120 ℃ as described above, characterized in that the temperature at which the first resin exhibits thermal adhesiveness is higher than the temperature at which the second resin exhibits blocking resistance. Preferably, the second resin exhibits blocking resistance at 90 ℃ or more and 120 ℃ or less, more preferably, at about 100 ℃, when adhered between a coated side and a non-coated side.

The second defoaming agent is used to prevent generation of bubbles and remove bubbles, and when the amount of the second resin is set to 1, the amount of the second defoaming agent charged may be preferably 0.002 parts by weight. More preferably, the first defoaming agent added in the first resin and the second defoaming agent added in the second resin may be the same kind. That is, the second defoaming agent may be a silicone-based defoaming agent having Polydimethylsiloxane (PDMS) as a main raw material, which is manufactured by korean silicon chemical, and may be a white suspension having a solid content of 38 wt% and a pH of about 7.0.

The silica is added for preventing surface stickiness, and the input amount (part by weight) of the silica is preferably more than 0.06 part by weight and less than 0.21 part by weight based on the second resin, and derivation of the range will be described later. The kind of the silica is not limited to any particular kind, but may be preferably 100% Silica (SiO)₂) And may have a white powder form. More preferably, the SILICA may be made from the SS-65B product of MICRONIZED SILICA (MICRONIZED SILICA) of the chemical technology S-CHEMTECH (strain) and may consist of 100% amorphous SILICA (SILICA, amorpous).

The wetting Agent is added for the purpose of improving coating coverage, and in the present specification, the wetting Agent may be regarded as a broad concept including a Leveling Agent (Leveling Agent) having a wetting effect. In the process of applying the second coating liquid onto the first coating layer 31 having water resistance and oil resistance, a coagulation phenomenon of the coating liquid due to a difference in surface tension may occur, and thus the wetting agent is input to enable the second coating liquid to be uniformly applied on the entire surface of the first coating layer 31, thereby improving the fluidity and smoothness of the coating layer, and obtaining a coated surface excellent in coverage. The kind of the wetting agent is not limited, but is preferably BYK-3410 product manufactured by BYK corporation, which is a yellowish-brown liquid having a solid content of 50% by weight, and whose main components are succinic acid (butaneionic acid), 2-sulfo-,1,4-bis (2-ethylhexyl) ester (2-sulfo-,1,4-bis (2-ethylhexyl) ester), sodium salt (sodium salt).

If the blocking resistance of a portion of the second coating layer 33 is lowered, thermal adhesion occurs between the paper cup under manufacture and the forming mold during the manufacture of the paper cup, and thus, the paper cup may not be smoothly moved during the manufacture process of separating from the forming mold and moving to the next process, and adhesion may occur between the stacked base papers, and adhesion may occur between the stacked paper cups when the finished paper cup is stacked, and thus it is necessary to maintain such blocking resistance above a predetermined level. Therefore, it is possible to prevent the blocking resistance of the second coating liquid from decreasing below an appropriate level by adding the wetting agent to the second coating liquid.

Next, it was confirmed through specific experiments whether or not the paper cup satisfies the required characteristics, reusability, and biodegradability (see experiment 1), thermal adhesiveness, molding workability, and water leakage in the actual production process (see experiment 2), an appropriate range of the amount of the first coating liquid applied (see experiment 3), an appropriate range of the amount of the second coating liquid applied (see experiment 4), an appropriate range of the amount of silica added in the preparation of the second coating liquid (see experiment 5), and an appropriate range of the amount of the wetting agent added in the preparation of the second coating liquid (see experiment 6). The method used when measuring the experimental data is as follows.

< measuring method >

1. Thermal adhesiveness

With respect to the thermal adhesiveness, in order to evaluate a process in which adhesion occurs between the coated side and between the coated side and the non-coated side at the time of forming the paper cup, a temperature at which thermal adhesion occurs was measured. Adhesion was performed using a thermal adhesion tester with the pressure set at 100KPa and the time set at 1 second. The temperature was raised at intervals of 5 ℃ with the pressure and time constant to adhere the plurality of test pieces, and then by applying force to the adhered portions and detaching, the temperature at which the coated side was completely detached was recorded with data. The lower the temperature, the more advantageous the thermal adhesiveness between the coated side and the coated side (when the base paper of the paper cup is adhered), and the lower the temperature, the more advantageous the thermal adhesiveness between the coated side and the non-coated side (when the side paper of the paper cup is adhered).

2. Blocking resistance

For blocking resistance, in order to evaluate a process in which adhesion occurs between a coated side and a forming device at the time of forming a paper cup, a temperature at which thermal adhesion occurs was measured. Adhesion was performed using a thermal adhesion tester with the pressure set at 100KPa and the time set at 5 seconds. The temperature was raised at intervals of 5 ℃ with the pressure and time constant to adhere the plurality of test pieces, and then the maximum temperature at which the coated surface was not detached was recorded with data when the adhered portions were detached by applying force. As for the blocking resistance between the coated side and the non-coated side (between the base paper or between the base paper and the forming die), the higher the measured temperature is, the more the phenomenon of adhesion between the base paper or adhesion between the base paper and the forming die is reduced, and thus it can be evaluated that the cup forming workability is excellent.

3. Water resistance

To evaluate the water penetration characteristics through the surface of the paper, a bobby Size Test (Cobb Size Test) was applied. The coated side was contacted with water for a predetermined time according to TAPPI T441 bobr size test, and then the amount of water permeation was measured to perform evaluation. At this time, the amount of water was set to 100mL, and the contact time was based on 30 minutes, and hot water (90 ℃) and cold water (1 ℃) were used and measured according to the end use. Preferably, the water resistance to hot water may be prioritized over the water resistance to cold water. The measured value is the amount of water received through the paper surface, so the lower the value, the better the water resistance.

4. Recyclability

Assuming that the paper raw material is reused, the sample is decomposed, and the decomposed raw material is made into handsheets, and the formation value of the made handsheets is recorded with data. Formation, which is used to indicate the degree of uniform distribution of pulp fibers of paper, has a great influence on the air permeability (the degree of air permeation through the paper), opacity, and print quality of the paper. The formation was measured using a TechPAP optical type formation tester, and the value measured by the formation tester was the formation value when paper was made by dissolving paper again in water, and therefore, it is considered that the lower the value, the more excellent the recyclability.

5. Biodegradability

In order to simulate the phenomenon of biodegradation in the natural state, base paper was placed on a frame formed of Plastic (Plastic) and dividing the space into four regions, and then the frame was further placed on the base paper, which was then buried in a flower bed, and the morphological change of the portion of the base paper in contact with soil was observed with the passage of time. When the base paper was degraded in a form similar to that of plain paper, it was evaluated as being biodegradable in a natural state.

6. Cup formation testing

In order to evaluate the possibility of mass production in a general cup molding machine, the workability, the thermal adhesion state of the molded cup, water leakage, and the like were evaluated while performing a normal operation in a cup molding apparatus using a hot press and high frequency system.

< contents of experiment 1 >

For experimental purposes: confirming whether the required properties, recyclability and biodegradability of the paper cup are satisfied

Experimental method: 3 kinds of acrylic copolymer resins were prepared and distinguished.

The first resin is characterized in that it is an aqueous copolymer latex prepared by emulsion polymerization of a monomer mixture containing an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and contains 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the total repeating unit, and the first resin has a solid content of 46.5 wt%, a glass transition temperature of 3 ℃, and a minimum film-forming temperature of 32 ℃.

The second resin is characterized in that it is an aqueous copolymer latex prepared by emulsion polymerization of a monomer mixture containing an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and contains 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the total repeating unit, and the second resin has a solid content of 45.7 wt%, a glass transition temperature of 22 ℃, and a minimum film-forming temperature of 20 ℃.

The third resin is characterized in that it is an aqueous copolymer latex prepared by emulsion polymerization of a monomer mixture containing an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and contains 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the total repeating unit, and the third resin has a solid content of 46.0 wt%, a glass transition temperature of 10 ℃, and a minimum film-forming temperature of 25 ℃.

The first resin may represent a product excellent in thermal adhesiveness but poor in blocking resistance, the second resin may represent a product excellent in blocking resistance but poor in thermal adhesiveness, and the third resin may represent a product moderate in thermal adhesiveness and blocking resistance.

Examples 1 to 1

To the prepared first resin, 0.002 parts by weight of an antifoaming agent was added based on the first resin to prepare a first coating liquid. Further, 0.12 parts by weight of silica, 0.01 parts by weight of a wetting agent, and 0.002 parts by weight of an antifoaming agent were added to the second resin based on the second resin to prepare a second coating liquid. For the coating solution prepared as described above, 12g/m²Is applied to 350g/m²To form a first coating layer, and 3g/m²Is applied to the first coating layer to formA second coating layer, thereby forming a double coating layer on one side of the base paper.

Examples 1 to 2

Using 250g/m²And the double coating layer of example 1-1 was formed on both sides of the base paper identically.

Comparative examples 1 to 1

0.002 parts by weight of an antifoaming agent was added to the prepared first resin to prepare a coating solution, and 15g/m was added²Is applied to 350g/m²To form a single coating layer.

Comparative examples 1 to 2

Adding 0.12 parts by weight of silica, 0.01 parts by weight of wetting agent and 0.002 parts by weight of defoaming agent based on the second resin to the prepared second resin to prepare a coating solution, and adding 15g/m²Is applied to 350g/m²To form a single coating layer.

Comparative examples 1 to 3

Adding 0.12 parts by weight of silica, 0.01 parts by weight of wetting agent and 0.002 parts by weight of defoaming agent based on the third resin to the prepared third resin to prepare a coating solution, and adding 15g/m²Is applied to 350g/m²To form a single coating layer.

Comparative examples 1 to 4

Using a base paper coated with Polyethylene (PE) currently manufactured as a commercial product, 30g/m²Coating the polyethylene at 300g/m²On the base paper.

Comparative examples 1 to 5

30g/m using a base paper coated with polylactic Acid (PLA) currently manufactured as a commercial product²Coating the polylactic acid at 300g/m²On the base paper.

< results of experiment 1 >

[ Table 1]

Referring to table 1, in examples 1-1 and 1-2 in which a double coating layer was formed, the characteristics required for the paper cup, that is, the thermal adhesiveness between the coated side and the coated side, the thermal adhesiveness between the coated side and the non-coated side, the blocking resistance between the coated side and the non-coated side, and the water resistance, all showed values within the normal ranges.

More importantly, in examples 1-1 and 1-2, the formation value indicating recyclability was within the normal range of 40 or less, and therefore, it was numerically verified that recyclability was high. Further, fig. 5 is a view showing a hand sheet produced by decomposing the sample of the cupstock paper according to example 1-1, and referring to fig. 5, it is understood that the hand sheet produced from the base paper sample of the present invention has a uniform distribution of pulp fibers, and thus, has been confirmed to be excellent in recyclability.

On the contrary, fig. 6 is a view showing a hand sheet prepared by decomposing a sample of a polyethylene-coated cupstock paper (comparative examples 1 to 4), and fig. 7 is a view showing a hand sheet prepared by decomposing a sample of a polylactic acid-coated cupstock paper (comparative examples 1 to 5), and unlike fig. 5, in fig. 6 and 7, a coating film remains on the hand sheet, and it was confirmed that the pulp fiber distribution was not uniform, and thus it was confirmed that the reusability of a polyethylene-coated paper cup and a polylactic acid-coated paper cup was poor.

FIG. 8 is a graph showing results of a biodegradability test, and shows a state with time when plain paper, the base paper of example 1-1, the base paper of comparative example 1-4, and the base paper of comparative example 1-5 are buried in a flower bed.

It was confirmed that, in the case of plain paper which was not coated, it was naturally degraded with the lapse of time, and thus four areas in contact with soil were completely degraded after the lapse of 6 months.

Example 1-1 showed no large change until 4 weeks elapsed compared to plain paper, but then started to degrade, and after 6 months elapsed, four areas in contact with soil were all completely degraded as in plain paper.

On the other hand, it was confirmed that in comparative examples 1 to 4 coated with polyethylene, the coated film portion remained not corroded even after 6 months passed, and likewise, in comparative examples 1 to 5 coated with polylactic acid, only the paper portion was degraded and the coated film portion remained unchanged without being degraded after 6 months passed.

In conclusion, the existing paper cup base paper is proved to be not environment-friendly, while the paper cup base paper of the invention is a biodegradable environment-friendly material.

In addition, in comparative example 1-1 in which a single coating layer was formed of a first resin, the blocking resistance between the coated side and the non-coated side was measured to be lower than the normal range, and therefore, when a paper cup was manufactured using the base paper of comparative example 1-1, adhesion occurred between the base paper and a forming die, etc., and a problem of operation stoppage occurred, and in comparative example 1-2 in which a single coating layer was formed of a second resin, silica, a wetting agent, and an antifoaming agent, the thermal adhesion between the coated side and the thermal adhesion between the coated side and the non-coated side were significantly higher than the normal range, and therefore, there was a problem that the temperature required for thermal adhesion was excessively high.

In comparative examples 1 to 3, the thermal adhesiveness between the coated side and the non-coated side was out of the normal range, and the hot water resistance and the cold water resistance did not satisfy the normal range.

< contents of experiment 2 >

For experimental purposes: confirmation of thermal adhesiveness, molding workability and Water leakage in the actual production Process

Experimental method: in order to evaluate the possibility of mass production in a general paper cup forming machine, a conventional operation was performed by using a hot press and a high frequency type cup forming apparatus. The cup forming machine was manufactured by itself under the operating conditions that 55 cups were produced per minute, high frequency adhesion was performed on the side paper sheet at a current of 3A, and the temperature of bottom paper adhesion was 340 ℃.

In example 2-1 of experiment 2, the forming operation was performed in a commercial paper cup forming machine by using example 1-1 of experiment 1 as a side paper of a paper cup and example 1-2 of experiment 1 as a base paper.

In comparative examples 2-1 to 2-3 of experiment 2, the forming operation was performed in a commercial paper cup forming machine by using comparative examples 1-1 to 1-3 of experiment 1 as side paper of the paper cup and using example 1-2 of experiment 1 as bottom paper of the paper cup.

In comparative examples 2-4 and 2-5 of experiment 2, the forming operation was performed in a commercial paper cup forming machine under the same conditions as the usual operation by using the base papers of comparative examples 1-4 and 1-5 of experiment 1.

In experiment 2, a measurement method different from the above measurement method was used to confirm operability during actual manufacturing and water leakage during use.

The thermal adhesiveness was evaluated as a detached state by forcibly detaching the adhered portion, and was evaluated as good when the paper was detached and as poor when the adhered surface was detached.

With regard to the forming operability 1, water was sprayed onto the base paper after thompson processing so that the base paper could become soft during forming, but in this case, the stacked base papers were stuck to each other, resulting in a problem of difficulty in supplying individual sheets, and therefore, in order to confirm such a problem, whether the base paper was easily separated into individual sheets after thompson processing and water spraying operation was evaluated as good when the base paper was easily separated, and as bad when sticking between the base papers was evaluated.

Regarding the molding workability 2, whether or not the separation was normal without adhesion to the molding die in the molding operation was evaluated, and when the separation was good, it was evaluated as good, and when adhesion occurred between the base paper and the molding die, it was evaluated as bad.

With respect to the molding workability 3, whether or not the normal operation could be performed without stopping when the operation was performed at a speed of 60/min for 1 hour was evaluated, and when not stopped, it was evaluated as good, and when stopped, it was evaluated as bad.

Regarding water leakage, it was confirmed whether or not water was leaked within 30 minutes by pouring coffee heated to 90 ℃ into the formed cup, and when there was no water leakage, it was evaluated as good, and when there was water leakage, it was evaluated as bad.

< results of experiment 2 >

[ Table 2]

Item

Example 2-1

Comparative example 2-1

Comparative examples 2 to 2

Comparative examples 2 to 3

Comparative examples 2 to 4

Comparative examples 2 to 5

Thermal adhesiveness

Good effect

Good effect

Failure of the product

Failure of the product

Good effect

Good effect

Molding workability 1

Good effect

Failure of the product

Good effect

Good effect

Good effect

Good effect

Molding workability 2

Good effect

Failure of the product

Good effect

Failure of the product

Good effect

Good effect

Workability of Molding 3

Good effect

Failure of the product

Good effect

Failure of the product

Good effect

Good effect

Leakage of water

Good effect

-

Failure of the product

-

Good effect

Good effect

Referring to table 2, the example 2-1 of experiment 2 showed good quality in terms of thermal adhesiveness, molding workability and water leakage, as in comparative examples 2-4 and 2-5 which are commercial articles.

On the other hand, in comparative example 2-1 of experiment 2 in which the base paper of comparative example 1-1 of experiment 1 was used as the side paper of the paper cup and the base paper of example 1-2 of experiment 1 was used as the base paper, the heat adhesiveness was good, but the surface was sticky, so that the molding workability was not good, and a normal paper cup could not be produced. The reason for this is that, as shown in experiment 1, the base paper of comparative example 1-1 had very low blocking resistance, and adhesion occurred between the coated side and the non-coated side.

In addition, in comparative example 2-2 of experiment 2 using the base paper of comparative example 1-2 of experiment 1 as the side paper of the paper cup and the base paper of example 1-2 of experiment 1 as the base paper, normal operation of the paper cup was possible, but when the adhesive surface of the formed cup was forcibly separated, the adhesive surface was detached to confirm that it was bad, and a water leakage phenomenon was observed in the finished paper cup.

In the evaluation items of experiment 1, the base paper of comparative examples 1 to 3, in which the thermal adhesion between the coated side and the non-coated side was out of the normal range and the hot water resistance and the cold water resistance could not satisfy the normal ranges, was used as the side paper of a paper cup, and the base paper of examples 1 to 2 was used as the base paper of the paper cup to perform the manufacturing operation of the paper cup, and as a result, the thermal adhesion was poor, and the whole operability was poor similarly to comparative example 2-1, and therefore, the paper cup could not be manufactured.

As described above, it was confirmed that the paper cup forming operation was performed in a commercial paper cup forming machine by using example 1-1 of experiment 1 as the side paper of the paper cup and example 1-2 of experiment 1 as the base paper of the paper cup, and as a result, an environment-friendly paper cup having basic characteristics, recyclability and biodegradability which the paper cup should have was produced.

In addition, when the base papers of comparative examples 1 to 3 of experiment 1 were used as side paper of paper cups, the workability was so poor that the paper cup forming operation could not be performed in the actual process of manufacturing paper cups, and therefore, even if the glass transition temperature of the resin was at an intermediate level satisfying the thermal adhesiveness and the blocking resistance, the thermal adhesiveness and the forming workability could not be satisfied at the same time by only a single coating layer, and the water resistance was remarkably lowered.

< contents of experiment 3 >

For experimental purposes: confirming the proper range of the first coating liquid coating amount

Experimental method: to an acrylic copolymer first resin, 0.002 parts by weight of an antifoaming agent was added based on the first resin to prepare a first dope. The first resin is an aqueous copolymer latex prepared by emulsion-polymerizing a monomer mixture containing an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and contains 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating unit, and has a solid content of 46.5 wt%, a glass transition temperature of 3 ℃, and a minimum film-forming temperature of 32 ℃.

Further, 0.12 parts by weight of silica, 0.01 parts by weight of a wetting agent, and 0.002 parts by weight of an antifoaming agent were added to the acrylic copolymer second resin based on the second resin to prepare a second coating liquid. The second resin is an aqueous copolymer latex prepared by emulsion-polymerizing a monomer mixture containing an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and contains 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating unit, and has a solid content of 45.7 wt%, a glass transition temperature of 22 ℃, and a minimum film-forming temperature of 20 ℃.

By adjusting the coating weight (g/m) of the first coating liquid²) At 350g/m²Is formed with a first coating layer and is formed by coating a base paper with a coating layer of 3g/m²Is applied onto the formed first coating layer to form a second coating layer, thereby forming a double coating layer on the base paper, by the above<Measurement method>The base paper produced by this process was measured for thermal adhesiveness between the coated side and the coated side, thermal adhesiveness between the coated side and the non-coated side, and anti-blocking property between the coated side and the non-coated side, hot water resistance, cold water resistance, recyclability, and biodegradability.

< results of experiment 3 >

[ Table 3]

Referring to Table 3, it was confirmed from examples 3-2 to 3-5 that when the coating amount of the first coating liquid was 8g/m²In the above case, the thermal adhesiveness between the coated surface and the coated surface, the thermal adhesiveness between the coated surface and the non-coated surface, the blocking resistance between the coated surface and the non-coated surface, the hot water resistance, the cold water resistance, the recyclability, and the biodegradability are within the normal ranges.

However, the first coating liquid is appliedThe cloth amount is 7g/m²Since example 3-1 (1) had a problem of rapid decrease in hot water resistance and cold water resistance, it was found that the amount of the first coating liquid applied was preferably more than 7g/m²。

Further, in the case of comparing examples 3 to 4 and examples 3 to 5, it was found that the increase in the coating amount hardly affected the quality of the base paper, the formation value judged to be recyclability in examples 3 to 5 showed an increasing tendency, and the price of the base paper increased with the increase in the coating amount of the first coating liquid, and thus it was found that the coating amount of the first coating liquid was preferably less than 18g/m²。

In conclusion, the application amount (g/m) of the first coating liquid was measured in experiment 3²) Preferably more than 7g/m²And less than 18g/m²。

< contents of experiment 4 >

For experimental purposes: confirming the proper range of the coating amount of the second coating liquid

Experimental method: to an acrylic copolymer first resin, 0.002 parts by weight of an antifoaming agent was added based on the first resin to prepare a first dope. The first resin is an aqueous copolymer latex prepared by emulsion-polymerizing a monomer mixture containing an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and contains 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating unit, and has a solid content of 46.5 wt%, a glass transition temperature of 3 ℃, and a minimum film-forming temperature of 32 ℃.

Further, 0.12 parts by weight of silica, 0.01 parts by weight of a wetting agent, and 0.002 parts by weight of an antifoaming agent were added to the acrylic copolymer second resin based on the second resin to prepare a second coating liquid. The second resin is an aqueous copolymer latex prepared by emulsion-polymerizing a monomer mixture containing an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and contains 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating unit, and has a solid content of 45.7 wt%, a glass transition temperature of 22 ℃, and a minimum film-forming temperature of 20 ℃.

By mixing 12g/m²The first coating liquid is coated at 350g/m²Forming a first coating layer on the base paper, and adjusting the coating amount (g/m) of the second coating liquid on the formed first coating layer²) Forming a second coating layer to form a double coating layer on the base paper. Then, by the above<Measurement method>The coated surface and the coated surface were measured for the cupstock papers having different coating amounts of the second coating liquid, and the thermal adhesiveness between the coated surface and the non-coated surface, the blocking resistance between the coated surface and the non-coated surface, the hot water resistance, the cold water resistance, the recyclability, and the biodegradability were measured, and the results are shown in the following table.

< results of experiment 4 >

[ Table 4]

Referring to Table 4, it was confirmed in examples 4-2 to 4-4 that when the coating amount of the second coating liquid was 2g/m²In the above case, the thermal adhesiveness between the coated surface and the coated surface, the thermal adhesiveness between the coated surface and the non-coated surface, the blocking resistance between the coated surface and the non-coated surface, the hot water resistance, the cold water resistance, the recyclability, and the biodegradability are within the normal ranges. However, the amount of the second coating liquid applied was 1g/m²In example 4-1, since a problem of a rapid decrease in the blocking resistance between the coated side and the non-coated side was observed, it was found that the amount of the second coating liquid to be applied preferably exceeded 1g/m²。

The amount of the second coating liquid is more than 5g/m²In examples 4 to 5 (a), it was confirmed that the thermal adhesiveness between the coated side and the non-coated side was out of the normal range, and it was therefore deduced that the coating amount of the second coating liquid was preferably less than 5g/m²。

Therefore, the amount of the second coating liquid applied (g/m)²) Preferably in a range of more than 1g/m²And is smallAt 5g/m²。

< contents of experiment 5 >

For experimental purposes: confirming an appropriate range of the amount of silica added in the production of the second coating liquid

Experimental method: by mixing 12g/m²Is coated at 350g/m²Forming a first coating layer on the base paper, and coating 3g/m on the formed first coating layer²The second coating liquid of (a) forms a second coating layer, thereby forming a double coating layer on the base paper.

At this time, 0.002 parts by weight of an antifoaming agent was added to the acrylic copolymer first resin based on the first resin to prepare the first coating liquid. The first resin is an aqueous copolymer latex prepared by emulsion-polymerizing a monomer mixture containing an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and contains 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating unit, and has a solid content of 46.5 wt%, a glass transition temperature of 3 ℃, and a minimum film-forming temperature of 32 ℃.

And, 0.01 parts by weight of a wetting agent, 0.002 parts by weight of an antifoaming agent and silica were put into the acrylic copolymer second resin based on the second resin, wherein different amounts of the silica were put into the acrylic copolymer second resin to prepare a plurality of the second coating liquids. The second resin is an aqueous copolymer latex prepared by emulsion-polymerizing a monomer mixture containing an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and contains 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating unit, and has a solid content of 45.7 wt%, a glass transition temperature of 22 ℃, and a minimum film-forming temperature of 20 ℃.

The thermal adhesiveness between the coated side and the coated side, the thermal adhesiveness between the coated side and the non-coated side, the blocking resistance between the coated side and the non-coated side, the hot water resistance, the cold water resistance, the recyclability, and the biodegradability were measured by the above < measurement method >.

< results of experiment 5 >

[ Table 5]

Referring to examples 5-1 to 5-5 of Table 5, it was confirmed that the blocking resistance between the coated side and the non-coated side was drastically reduced in example 5-1 in which 0.05 parts by weight of silica was charged based on the second resin, and the blocking resistance between the coated side and the non-coated side was within the normal range in example 5-2 in which 0.06 parts by weight of silica was charged based on the second resin, and therefore it was confirmed that the charged amount of silica preferably exceeded 0.05 parts by weight when the amount of the second resin was set to 1 at the time of producing the second coating liquid.

However, in example 5-4, it was confirmed that the thermal adhesion between the coated side and the coated side, the thermal adhesion between the coated side and the non-coated side, the blocking resistance between the coated side and the non-coated side, the hot water resistance, the cold water resistance, the recycling property and the biodegradability were all within the normal ranges when the amount of silica added was 0.20 parts by weight, but in example 5-5, it was confirmed that the thermal adhesion between the coated side and the coated side, the thermal adhesion between the coated side and the non-coated side, the hot water resistance and the cold water resistance were out of the normal ranges when the amount of silica added was 0.21 parts by weight.

Therefore, it is found by this experiment that the amount of silica (part by weight) added based on the second resin is preferably more than 0.05 part by weight and less than 0.21 part by weight.

< contents of experiment 6 >

For experimental purposes: confirming an appropriate range of the amount of the wetting agent to be added in the production of the second coating liquid

Experimental method: by mixing 12g/m²Is coated at 350g/m²A first coating layer is formed on the base paper,and coating the first coating layer formed by coating with 3g/m²The second dope of (2) forms a second coating layer, thereby manufacturing a cupstock paper having a double coating layer.

Wherein 0.002 parts by weight of an antifoaming agent is added to the acrylic copolymer first resin based on the first resin to prepare the first dope. The first resin is an aqueous copolymer latex prepared by emulsion-polymerizing a monomer mixture containing an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and contains 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating unit, and has a solid content of 46.5 wt%, a glass transition temperature of 3 ℃, and a minimum film-forming temperature of 32 ℃.

And, 0.12 parts by weight of silica, 0.002 parts by weight of an antifoaming agent and an antifoaming agent were put into the acrylic copolymer second resin based on the second resin, wherein the wetting agents were added in different amounts to prepare second coatings having the content of the wetting agents different from each other. The second resin is an aqueous copolymer latex prepared by emulsion-polymerizing a monomer mixture containing an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and contains 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating unit, and has a solid content of 45.7 wt%, a glass transition temperature of 22 ℃, and a minimum film-forming temperature of 20 ℃.

The thermal adhesiveness between the coated side and the coated side, the thermal adhesiveness between the coated side and the non-coated side, the blocking resistance between the coated side and the non-coated side, the hot water resistance, the cold water resistance, the recyclability, and the biodegradability were measured for the cupstock papers having different amounts of the humectant charged as described in the above < measurement method >, and the results are shown below.

< results of experiment 6 >

[ Table 6]

Referring to examples 6-1 to 6-5 in Table 6, it was confirmed that in example 6-1 in which no wetting agent was added based on the second resin, the blocking resistance between the coated side and the non-coated side was significantly reduced.

On the contrary, in example 6-2 in which 0.005 parts by weight of the wetting agent was added, it was confirmed that the blocking resistance between the coated side and the non-coated side was within the normal range, and therefore, the wetting agent was added to improve the blocking resistance between the coated side and the non-coated side.

However, when the amount of the humectant was increased, the production cost of the cupstock paper increased accordingly, and in examples 6 to 5 in which the amount of the humectant was 0.02 parts by weight, the hot water resistance and the recyclability tended to decrease even though the amount of the humectant was within the normal range, and therefore, it was experimentally confirmed that the amount of the humectant was preferably less than 0.02 parts by weight.

In summary, the amount of the wetting agent to be added (part by weight) is preferably more than 0 part by weight and less than 0.02 part by weight based on the second resin.

Fig. 9 is a view illustrating a method (S1) of manufacturing eco-friendly cupstock paper according to an embodiment of the present invention, and the method (S1) of manufacturing eco-friendly cupstock paper is described below with reference to fig. 9, which relates to a method of manufacturing eco-friendly cupstock paper having excellent thermal adhesiveness, water resistance, and blocking resistance, and being easily recycled and biodegradable in a natural state, and includes a base paper providing step (S10) and a double coating layer forming step (S30).

The base paper providing step (S10) is a step of providing the base paper 10 from the paper making section, and the base paper 10 is a base paper forming the double coating layer 30 and can be regarded as a general concept of all kinds of paper that can be used when manufacturing paper cups. The base paper 10 is not limited to any particular paper, but the base paper 10 preferably has 200-350g/m²And may be KAce PNC product of korean paper-making company (ltd.) made using 100% natural pulp containing no fluorescent material. The paper making section may be considered to be a broad outlineIt is thought that it includes not only an On-Machine process (On-Machine) of directly producing the base paper 10 and continuously supplying the base paper 10 to the coating unit, but also an Off-Machine process (Off-Machine) of supplying the base paper 10, which is wound by a Reel (Reel) to be conveyed, to the coating unit. An example of producing the base paper 10 from the paper making section is explained below, in which first dewatering is performed by gravity, and when a web (web) having a water content of about 50-60% is formed by pressing, it is dried again by a drying unit to reduce the water content to about 2-7%. Thereafter, the starch-based sizing liquid is applied to the web in a dry state in a Size Press (Size Press), and the web is dried again in a drying unit (After Dryer) so as to have a moisture content of about 2 to 10%, and finally, the thickness of the paper is adjusted and the surface of the paper is smoothed, whereby the base paper 10 can be formed.

The double coating layer forming step (S30) is a step of forming the double coating layer 30 on the base paper by a coating unit after the base paper providing step (S10). The coating unit forms a double coating layer on the base paper 10 supplied from the paper making section through the base paper supplying step (S10). The coating unit includes not only a coater for papermaking but also a gravure coater, a flexo coater, a Roll-to-Roll coater, and the like, which are Off-Machine type coaters, and it is not limited to a specific coater. The double coating layer 30 may be formed on one side of the base paper 10, and may also be formed on both sides of the base paper 10. The double coating layer forming step (S30) includes a first coating layer forming step (S31) and a second coating layer forming step (S33).

The first coating layer forming step (S31) refers to a step of forming a first coating layer 31 on one side of the base paper 10 by a first coating unit. The first coating unit may include: a first coating liquid supply unit for supplying a first coating liquid; a first coating head unit for coating the base paper 10 with the first coating liquid; and a first drying unit that dries the coated first coating liquid. As described above, the first coat layer 31 is a layer formed of the first coating liquid including the first resin and the first defoaming agent, and is considered to be a portion that causes the cupstock paper to exhibit excellent thermal adhesiveness, water resistance, and oil resistance. Fig. 10 is a view illustrating the first coating layer forming step (S31) of fig. 9, the first coating layer forming step (S31) including a first coating liquid supplying step (S311), a first coating liquid applying step (S313), and a first coating liquid drying step (S315).

The first coating liquid supplying step (S311) is a step of supplying the first coating liquid to be coated on the base paper 10 by a first coating liquid supplying unit. The first dope includes a first resin and a first defoaming agent, and as described above, the first resin is characterized by having a glass transition temperature lower than the temperature during the manufacturing process of a paper cup, and thus has excellent thermal adhesiveness and water resistance. Specifically, the first resin is an aqueous copolymer latex which is prepared by emulsion polymerization of a monomer mixture including an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and which includes 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating unit, and the first resin may have a solid content of 46.5 wt%, a glass transition temperature of 3 ℃, and a minimum film-forming temperature of 32 ℃. The first defoaming agent is preferably added in an amount of 0.002 parts by weight based on the first resin.

The first coating liquid applying step (S313) is a step of applying the first coating liquid on the base paper 10 by the first coating head unit after the first coating liquid supplying step (S311). As can be seen from the above experiment, the amount (g/m) of the first coating liquid applied was determined²) Preferably more than 7g/m²And less than 18g/m². Examples of the coating method include Blade coating (Blade Coater), roll coating (Rod Coater), Air Knife coating (Air Knife Coater), Curtain coating (Curtain Coater), and the like, and suitable methods for environment-friendly coating include Air Knife coating, roll coating, and Blade coating in this order. However, in the present invention, the coating manner of the first coating head unit is not limited to any particular manner, and various manners may be used.

The first coating liquid drying step (S315) is a step of drying the first coating liquid applied to the base paper 10 by a first drying unit after the first coating liquid applying step (S313). The first drying unit may be a heater of an Infrared Ray (IR) system, and is a concept including a scarf dryer, a drum dryer, and the like for a general coater. When the first coat layer 31 is formed on both sides of the base paper 10, it may be preferable that the first coating liquid is applied to one side and dried, and then the first coating liquid is applied to the other side and dried.

The second coating layer forming step (S33) refers to a step of forming a second coating layer 33 on the first coating layer 31 by a second coating unit after the first coating layer forming step (S31). The second coating unit may include: a second coating liquid supply unit for supplying a second coating liquid; a second coating head unit for coating the base paper 10 with a second coating liquid; and a second drying unit drying the coated second coating liquid. As described above, the second coating layer 33 is a layer formed of the second coating liquid including the second resin, the second defoaming agent, silica, and the wetting agent, and can be regarded as a portion that causes the cupstock paper to exhibit excellent blocking resistance. Fig. 11 is a view illustrating the second coating layer forming step (S33) of fig. 9, and referring to fig. 11, the second coating layer forming step (S33) includes a second coating liquid supplying step (S331), a second coating liquid applying step (S333), and a second coating liquid drying step (S335).

The second coating liquid providing step (S331) refers to a step of providing a second coating liquid to be coated on the first coating layer 10 by a second coating liquid supply unit, the second coating liquid including a second resin, a second defoaming agent, silica, and a wetting agent. The second resin is characterized in that it has a glass transition temperature higher than that during the paper cup manufacturing process, and thus has excellent blocking resistance. Preferably, the second resin is an aqueous copolymer latex prepared by emulsion-polymerizing a monomer mixture including an acrylic monomer and a carboxylic acid-based monomer in the presence of a reactive emulsifier and a polyfunctional silicone polymer, and includes 80% or more of a repeating unit derived from the acrylic monomer and the carboxylic acid-based monomer with respect to the entire repeating unit, and has a solid content of 45.7 wt%, a glass transition temperature of 22 ℃, and a minimum film-forming temperature of 20 ℃. It is preferable to add 0.002 parts by weight of the second defoaming agent based on the second resin, and it can be understood from the above experimental results that the amount (parts by weight) of the silica added may be more than 0.05 parts by weight and less than 0.21 parts by weight based on the second resin, and the wetting agent may be more than 0 parts by weight and less than 0.02 parts by weight based on the second resin.

The second coating liquid applying step (S333) is a step of applying a second coating liquid onto the first coating layer 31 by a second coating head unit after the second coating liquid providing step (S331). As described above, the coating amount (g/m) of the second coating liquid²) Preferably more than 1g/m²And less than 5g/m². Examples of the coating method include Blade coating (Blade Coater), roll coating (Rod Coater), Air Knife coating (Air Knife Coater), Curtain coating (Curtain Coater), and the like, and suitable methods for environment-friendly coating include Air Knife coating, roll coating, and Blade coating in this order. However, the coating manner of the second coating head unit is also not limited to any particular manner, and may include various manners.

The second coating liquid drying step (S335) is a step of drying the second coating liquid applied on the first coating layer 31 by a second drying unit after the second coating liquid applying step (S333). The second drying unit may also be an IR type heater, like the first drying unit, and may include a scarf dryer, a drum dryer, and the like for a general coater. In the case of forming the second coat layer 33 on both sides of the base paper 10 on the premise that the first coat layer 31 is formed, it is preferable that the second coating liquid is applied to the first coat layer 31 on one side and dried, and then the second coating liquid is applied to the first coat layer 31 on the other side and dried.

Fig. 12 is a view illustrating a method of manufacturing eco-friendly cupstock paper according to another embodiment of the present invention, and fig. 13 is a view illustrating a cupstock paper manufactured by the manufacturing method of fig. 12, in which the double coating layer 30 is formed only on one side of the base paper 10 in the embodiment of fig. 9, and in the examples of fig. 12 and 13, the double coating layer 30 is formed on both sides of the base paper 10. In this case as well, it is preferable that the double coating layers 30 formed on one side and the other side of the base paper 10, respectively, are identical to each other.

The base paper portion of the paper cup requires higher water and oil resistance, and therefore, the side paper of the paper cup forms the double coating 30 only on one side, and the base paper of the paper cup forms the double coating 30 on both sides, thereby realizing more excellent performance of the paper cup without greatly increasing the production cost of the base paper of the paper cup.

For this reason, unlike the embodiment of fig. 9, the embodiment of fig. 12 and 13 is characterized in that a third coat forming step (S32) is further included between the first coat forming step (S31) and the second coat forming step (S33), and a fourth coat forming step (S34) is added after the second coat forming step (S33).

If it is said that the first coating layer forming step (S31) is a process of forming the first coating layer 31 on one side of the base paper 10 by a first coating unit, the third coating layer forming step (S32) may be a process of forming the third coating layer 32 identical to the first coating layer 30 on the other side of the base paper 10 by a third coating unit. That is, the coatings formed by the first coating layer forming step (S31) and the third coating layer forming step (S32) are identical to each other, and the only difference is on which side of the base paper 10 the coating layer is formed. Therefore, the above description about the first coating layer 31 may be directly applied to the third coating layer 32, and the description about the first coating layer forming step (S31) may also be directly applied to the third coating layer forming step (S32).

When the first coating layer 31 and the third coating layer 32 are formed on both sides of the base paper 10, respectively, the second coating layer forming step (S33) is performed after the third coating layer forming step (S32), so that the second coating unit forms the second coating layer 33 on the first coating layer 31. After the second coat forming step (S33), a fourth coat forming step (S33) is performed in which a fourth coat 34 identical to the second coat 33 is formed on the third coat 32 by a fourth coating unit (S33).

The second coat forming step (S33) differs from the fourth coat forming step (S34) only in that the second coat 33 is formed on the first coat 31 in the second coat forming step (S33), the fourth coat 34 is formed on the third coat 32 in the fourth coat forming step (S34), and the second coat 33 is the same as the fourth coat 34, and therefore, the above-mentioned explanation about the second coat 33 can be directly applied to the fourth coat 34, and the explanation about the second coat forming step (S33) can also be directly applied to the fourth coat forming step (S34).

The foregoing detailed description is illustrative of the invention. In addition, the foregoing illustrates and describes the preferred embodiments of the present invention, and the invention is capable of use in various other combinations, permutations and environments. That is, the present invention can be changed or modified within the scope of the inventive concept disclosed in the present specification, the scope equivalent to the disclosed content, and/or the technical scope or knowledge in the art. The above-described embodiments illustrate the best mode for carrying out the technical idea of the invention and are susceptible of various changes required in the specific application fields and uses of the invention. Therefore, the above detailed description of the invention is not intended to limit the invention to the embodiment disclosed. Furthermore, the claims should be construed to include other embodiments.