KR20220022812A - Eco-friendly Composition for paper coating comprising CNF - Google Patents

Abstract

The present invention relates to an eco-friendly composition for paper coating comprising a cellulose nanofiber (CNF) and, more specifically, to an eco-friendly composition for paper coating that can be recycled so as to reduce environmental pollution. The eco-friendly composition for paper coating comprising a CNF according to the present invention has excellent water resistance, oil resistance and safety, and thus can be used for food packaging containers. Meanwhile, according to the present invention, a coating composition, which enables eco-friendly recycling of paper when applied thereto, can be obtained.

Description

Eco-friendly Composition for paper coating comprising CNF

The present invention relates to an eco-friendly paper coating composition comprising CNF (Cellulose Nano Fiber), and more particularly, to an eco-friendly paper coating composition that can be recycled to reduce environmental pollution.

Paper is used for various purposes due to its ease of manufacture and processing, and the uses include food packaging, containers, and tableware.

However, since paper generally has weak physical properties to oil, water, and heat, there is a disadvantage in that when food is packaged or contained only with pure paper, water or oil leaks or the paper tissue is damaged and the structural form is broken.

For this reason, coated paper is used, and specifically, coated paper to which a coating that imparts oil/moisture resistance performance to paper is applied is used.

A representative material used for such coatings is polyethylene (PE). Polyethylene is non-toxic and has hard physical properties, so it is widely used in food containers, etc., and coated paper in which polyethylene in the form of a thin film is attached to paper by heat sealing is widely used.

However, polyethylene does not decompose in nature and has a disadvantage that carcinogenic VOCs (volatile organic solvents) are generated when heat is applied. In addition, there is a problem that the coated paper to which polyethylene is fused is impossible to recycle due to its non-decomposable physical properties. Therefore, polyethylene coated paper, which cannot be recycled, must be incinerated or landfilled at the time of disposal. However, there is a problem that it is not eco-friendly because it does not decompose naturally and emits toxic environmental hormones or VOCs when incinerated.

Accordingly, there is a growing demand for the development of a paper coating composition that is environmentally friendly and has excellent moisture/oil resistance to replace the existing non-environmental materials.

In order to solve the problems of the prior art as described above, the present invention is to provide an eco-friendly paper coating composition comprising a component that has moisture/oil resistance comparable to that of conventional polyethylene and is easily heat-sealed and easily decomposed. purpose of the invention.

The present invention provides a coating composition comprising CNF (cellulose nanofiber) in order to achieve the object as described above.

One embodiment of the present invention further comprises one or more resin compounds selected from the group consisting of ethylene acrylic acid copolymer (EAA), polyvinyl alcohol (PVA), and acrylic ester copolymer (acrylic ester copolymer) do.

According to another embodiment of the present invention, the coating composition is characterized in that it comprises 100 parts by weight of the resin compound and 2 to 10 parts by weight of the CNF aqueous solution, and further an antifoaming agent and/or a leveling agent. Preferably, it is characterized in that it contains 5 parts by weight of an aqueous CNF solution.

Another embodiment of the present invention is characterized in that the concentration of the CNF aqueous solution is 1-5%, preferably 2%.

According to the present invention, it is possible to obtain a coating composition that can be used in food packaging containers because of its excellent water resistance, oil resistance and safety, while enabling eco-friendly recycling of paper.

Paper products, which are widely used in food containers and packaging, are made with pulp as the main raw material, and are sometimes coated with food wax or synthetic resins to supplement the characteristics of paper products that are easily wetted by water. For the safety management of harmful substances or impurities that can be transferred to food, paper products made with pulp as the main raw material are stipulated in the standards for PCBs, arsenic, lead, formaldehyde, and optical brighteners. In addition, for processed paper coated with synthetic resin, the specification of the synthetic resin material is applied.

PCBs is an abbreviation for polychlorinated biphenyls, and is a kind of environmentally-derived pollutants with high persistence. In the case of printed paper products, the printed side should not come into contact with food because the printing ink ingredient may transfer to food and have a harmful effect on the human body. Even when printing on a surface that does not come in direct contact with food, the printing ink must be dried before use, and benzophenone, a component of the printing ink, must not be eluted beyond the standard (0.6 mg/L or less).

There is no fear of detecting harmful substances even if the paper-made tea bags are soaked in tea for a long time. Since no adhesive is used to seal the tea bag, heat or pressure is used, so there is no need to worry about the dissolution of the adhesive component. For reference, in addition to paper, synthetic resins such as polyamide, polypropylene, and polylactide with good heat resistance are often used in combination, and each material must meet the standards and/or specifications.

Paper cups are usually coated with polyethylene and are generally safe to use with hot water or beverages such as coffee. However, since the product is not made for microwave use and there is a risk that the coating may come off when food is cooked in a microwave oven, it is desirable to use a container marked “for microwave” when cooking food in a microwave oven.

In the case of non-food paper products such as calendars and A4 printing paper, fluorescent whitening agents, etc. may be used, so it is better not to come in direct contact with food.

Typical examples of paper used for food are the following.

△ Kraft paper is a paper manufactured from kraft pulp manufactured by a chemical method, and has high strength and is used for paper bags and paper bags.

△Oil-resistant paper, glassine paper: It is a translucent paper that has been given oil resistance by hydrating the cellulose fibers by crushing the pulp for a long time during the papermaking process.

△ Sulfuric acid paper (lactic acid paper): Paper produced by immersing pulp in sulfuric acid to expand and partially dissolve cellulose fibers. It has no odor and has a smooth surface.

△Wax paper: Wax-treated paper, as one of the moisture barrier packaging materials, has oil resistance and heat-adhesive properties.

△Corrugated cardboard: It is a cardboard made by bonding corrugated paper to an original cardboard. It uses relatively low weight and high compressive strength, so it is often used in the form of a box.

Paper absorbs water easily and generally has poor water resistance, so when manufacturing paper plates, paper lunch boxes, and paper foils, they are manufactured by coating synthetic resins such as polyethylene (PE), rather than simply making paper, and are in direct contact with food. Safety management is carried out by applying the standards and specifications of the materials used for the surface.

Paper (waste paper) has a long history of recycling along with scrap metal and is one of the most actively recycled items. The types of paper currently being recycled are newspaper, corrugated paper, high-quality paper, and mixed paper.

Waste paper grade is divided into three types according to the method of processing the waste paper and the shape of the final product. First, it is a paper substitute for pulp. Paper substitutes for pulp are recyclable papers that can be put directly into the pulp maker without processing, and the most used waste paper is computer-printed paper. Second, it is ink-free grade paper. Deinking grade paper is paper that goes through a chemical treatment process to remove ink, washes and bleaches, and then mixes it with the pulp. It is colored paper paper or printed white paper paper. It cannot be used directly as a pulp substitute, but is used to produce newsprint, tissue paper, napkins, paper towels, and cardboard for boxes. Third, it is bulk grade paper. Bulk grade paper is used directly to produce paper boxes, corrugated cardboard boxes, egg boxes, compressed cardboard, and construction papers such as felt paper and wallboard without ink removal.

Among these waste papers, paper cartons and paper cups use the highest quality natural pulp, so high-quality toilet paper can be produced if separated and recycled. General paper packs and paper cups cannot be recycled together with general waste paper because they are coated with resin or wax such as PE.

The composition for coating according to the present invention is characterized in that it does not use resin components that are difficult to decompose, and uses environmentally friendly components that are easy to decompose, while mixing cellulose nanofibers to solve these conventional problems.

Nanocellulose refers to nano-micrometer-sized rod-shaped particles or fibers in which cellulose chains form a bundle and are tightly bound. In general, nanocellulose has a tensile modulus similar to that of steel or Kevlar (100~160 GPa), a low density (0.8~1.5 g/cm3), and a large specific surface area. It is a bio-based material. Because of these advantages, it can be applied to various fields such as the packaging industry, the paper industry, filtration devices, artificial skin, and cosmetics.

Nanocellulose can also be produced from bacteria such as Acetobacter xylinum, but bacterial culture is expensive and has a low volumetric yield, making it difficult to mass-produce. Therefore, currently most nanocellulose is obtained through top-down processing from wood pulp or non-wood plants. At this time, nanocellulose can be largely divided into cellulose nanofibril (CNF) and cellulose nanocrystal (CNC) according to the extraction method from biomass. Cellulose nanofibers are usually 5 to 100 nm in diameter (width) and several to several tens of μm in length, and are manufactured through mechanical treatment. Cellulose nanofibers are generally manufactured by mechanical treatment, but in nanocellulose raw wood or non-wood biomass, other than cellulose, materials such as hemicellulose and lignin are combined to form a rigid structure, so this structure Various pretreatment methods have been proposed in order to effectively crush them. The most used equipment in small units is a grinder. In the grinder, two ceramic grinding disks are spaced apart at an appropriate distance, and the lower disk rotates at high speed while the upper disk is fixed. Therefore, the cellulose fibers fed into the disk are compressed sideways in the disk by centrifugal force. At this time, there are rapidly rotating grinding stones on either side of the disk, which acts as a shear force and frictional force on the cellulose fiber, and as a result, nano-ization is made.

On the other hand, the most commercialized mechanical treatment is a high-pressure homogenizer. Cellulose fibers at a concentration of 1 to 2 wt% are mixed with distilled water to make a suspension, and then homogenized with a high-pressure homogenizer. Due to the high pressure, the fibers rapidly pass through a thin slit and are subjected to large shear and impact forces, and are separated in the form of nanosized fibers. The high-pressure homogenizer has the advantage of being able to make a large amount of nanofibers at a high speed.

Cellulose nanofiber is a nano-level fiber of cellulose fibers that form the basis of plant cells. It weighs 1/5 of iron, has 5 times the strength of iron, has a very large specific surface area, has little thermal deformation, and has dimensional stability. It has excellent physical properties. In addition, since it is a plant-derived material, there is no problem of environmental pollution when disposed of, and resources are abundant.

When these cellulose nanofibers are applied to a coating, useful effects that could not be obtained conventionally due to their fine size can be obtained.

For example, in the case of cement or flour sacks, the penetration of water or oil can be prevented with a general waterproof/oil-proof coating, but it is difficult to block moisture in the gaseous state due to the large number of pores. When cellulose nanofibers are used for the coating of these cement or flour bags, the pores of the paper are blocked to a microscopic size, preventing moisture from entering the inside, preventing lumps or deterioration, so it can be stored for a long time compared to general coatings. will do In other words, it has superior breathability and moisture absorption resistance compared to general waterproof/oil-proof coatings.

In addition, since the cellulose nanofiber has a certain level of viscosity, leveling can be improved during coating, and accordingly, it is possible to have a constant coating film thickness. If the viscosity of the coating composition is too high, coating defects such as craters or pinholes may occur. Cellulose nanofibers have an appropriate viscosity to form a uniform coating film without such coating defects.

In addition, the effect of imparting stability to the coated surface after coating can be obtained. When the coated paper is folded or folded, the coating performance is maintained without cracks, separation, or peeling from the paper, so it can be stable for cutting operations such as trays and cups of coated paper.

The above-described cellulose nanofiber can be included in the recycled paper manufacturing process as it is without the need for separate separation when the cellulose is cellulose, such as paper, when recycling (repulping), so that the effect of excellent recycling cost efficiency can be obtained.

Paper coated with the composition for coating according to the present invention can be recycled in an environment-friendly manner by dissolving it in water during the regeneration process and then performing alkali treatment.

The present inventors confirmed the effect of the coating composition of the present invention through the following experiments. However, the following experiments are for understanding and explaining the present invention in more detail, and they do not limit the scope of the present invention.

[Example]

Example 1

To 100 parts by weight (80 to 120) of Dow Primacor® 5980I, 5 parts by weight (1 to 20) of a 2% aqueous solution of CNF (cellulose nanofiber) was added and mixed. After that, add antifoaming agent and leveling agent, mix slowly for at least 1 hour, and then use Bar #12 ~ #16 to coat the coating amount to solid content to 4gsm ~ 10gsm, and then dry at 150℃ to test for waterproofing, oil prevention, and heat sealing. .

Example 2

After adding 5 parts by weight (1 to 20) of CNF 2% aqueous solution to 100 parts by weight of Daeyang Corporation's polysol (DC-9740) and mixing, add 50 parts by weight of water to adjust the concentration and make a 15% aqueous solution, followed by an antifoaming agent, leveling agent was added and mixed slowly for at least 1 hour, and then it was coated using Bar #12 ~ #16 with a coating amount of 4gsm ~ 10gsm relative to the solid content. It was dried at 150℃ and tested for waterproof, oil-proof, and heat sealing.

Example 3

After adding 5 parts by weight (1 to 20) of CNF 2% aqueous solution to 100 parts by weight of Nucrel 0910 (Dow) and mixing, add 50 parts by weight of water to adjust the concentration and make a 15% aqueous solution, then add antifoaming agent and leveling agent for 1 hour After mixing the mixture slowly, it was coated with a coating amount of 4gsm ~ 10gsm to the solid content using Bar #12 ~ #16. It was dried at 150℃ and tested for waterproof, oil-proof, and heat sealing.

Example 4

Nucrel 0910 (Dow) 80 parts by weight, Daeyang Polysol (DC-9740) 20 parts CNF 2% aqueous solution 5 parts by weight (1 to 20) After mixing, 50 parts by weight of water to adjust the concentration and 15% aqueous solution In order to prevent dry blaock when coating the drug, add 10 parts by weight of WAX (5 ~ 20), an antifoaming agent, and a leveling agent, mix slowly for at least 1 hour, and then use Bar #12 ~ #16 to apply the coating amount to the solid content. was coated with 4gsm ~ 10gsm. It was dried at 150℃ and tested for waterproof, oil-proof, and heat sealing.

Comparative Example 1 (excluding CNF)

Add 15 parts by weight of epichlorohydrin, a curing agent, to 100 parts by weight of a 10% aqueous solution of PVA, add an antifoaming agent and a leveling agent, and mix slowly for at least 1 hour. coated. It was dried at 150℃ and tested for waterproof, oil-proof, and heat sealing.

Comparative Example 2 (excluding CNF)

After mixing 80 parts by weight of Nucrel 0910 (Dow) and 20 parts by weight of Daeyang Polysol (DC-9740), add 50 parts by weight of water to adjust the concentration and make a 15% aqueous solution. After adding 10 parts by weight (5 to 20), an antifoaming agent, and a leveling agent, and mixing them slowly for at least 1 hour, they were coated using Bar #12 to #16 in a coating amount of 4gsm to 10gsm relative to the solid content. It was dried at 150℃ and tested for waterproof, oil-proof, and heat sealing.

5980!(Dow): Dissolve 100g of 20% Ethylene Acrylic Acid aqueous solution with 400g of water and 96g~150g of Dimethylethanolamine

DC_9740 (Daeyang Polysol): acrylic ester copolymer. Methylmethacrylate, n-butyl, 2-ethylhexylacrylate, acrylic acid copolymer 30~40%, Triethoxyoctyl silane 1.0~7.0%

NUCREL™ 0910(Dow): Acid copolymer. A copolymer of ethylene (91% by weight) and methacrylic acid (9% by weight).

WAX (Ocean Polysol): emulsion

Above, although the present invention has been described in detail through the <Examples>, the present invention is not limited to the above embodiments, and may be modified in various forms, and within the technical spirit of the present invention, the present invention belongs It is clear that many modifications are possible by those of ordinary skill in the art. In addition, within the scope that does not depart from the technical spirit of the present invention described in the claims, various types of substitution, modification and change will be possible by those skilled in the art to which the present invention belongs, and this is also the scope of the present invention will be said to belong to

Claims (3)

A composition for eco-friendly coating, characterized in that it contains CNF (Cellulose Nanofiber).
The method of claim 1,
An eco-friendly coating composition, characterized in that it further comprises at least one resin compound selected from the group consisting of ethylene acrylic acid copolymer (EAA), polyvinyl alcohol (PVA), and acrylic ester copolymer.
3. The method of claim 2,
100 parts by weight of the resin compound and 0.02 to 0.5 parts by weight of CNF, and an antifoaming agent and/or a leveling agent in addition, an eco-friendly coating composition.