Oil-resistant coating agent, oil-resistant coating method, oil-resistant packaging material, and oil-resistant tableware

Abstract

The present invention provides: an oil-resistant coating agent which exhibits excellent oil resistance and is obtained using mainly naturally derived materials that do not include petroleum-based materials or resin materials obtained using petroleum-based materials; an oil-resistant coating method in which said oil-resistant coating agent is used; an oil-resistant packaging material; and oil-resistant tableware. Provided is an oil-resistant coating agent of two-component type, the agent comprising: a main agent containing at least an alginate; and a secondary agent containing at least a polyvalent metal salt and xanthan gum. Provided is an oil-resistant coating method that includes: a main agent coating step for coating the main agent containing at least an alginate on a surface of a paper base; and a secondary agent supply step for supplying the secondary agent containing at least a polyvalent metal salt and xanthan gum to the main agent layer coated on the surface of the paper base. Provided is an oil-resistant packaging material that comprises an oil-resistant layer, which contains xanthan gum and a crosslinked body derived from a polyvalent metal alginate, on a surface of a paper base. Provided is an oil-resistant tableware that comprises a similar oil-resistant layer on an inner surface that is in contact with contents.

Description

Oil-resistant coating agent, oil-resistant coating method, oil-resistant packaging material, and oil-resistant tableware

[0001] The present invention relates to an oil-resistant coating agent, an oil-resistant coating method, an oil-resistant packaging material, and an oil-resistant tableware.

[0002] Conventionally, when various snacks and the like are sold at fast food restaurants, convenience stores, etc., simple bag- or box-shaped paper packaging containers are used so that the snacks can be consumed immediately. The packaging material for such packaging containers is required to be oil-resistant when used for foods that contain a lot of oil, such as French fries or fried chicken.

[0003] Fluororesin-based oil-proofing agents are commonly used as paper packaging materials that are oil-resistant. For example, greaseproof paper in which a fluororesin-based oil-proofing agent is coated on the surface of a base paper to form an oil-resistant layer, and greaseproof paper in which a fluororesin-based oil-proofing agent is internally incorporated into a paper substrate are known (see, for example, Patent Document 1). However, when greaseproof paper using a fluororesin-based oil-proofing agent is incinerated, various fluorine-containing decomposition products that may have an impact on the environment are generated. Because there are concerns that such fluorine-containing decomposition products may have an impact on the global environment and human health, there is a demand for packaging materials that do not use fluororesins as much as possible.

[0004] As an oil-resistant packaging material that does not use fluororesin, grease-resistant paper has been proposed in which the surface of a base paper is coated with a resin layer made of an oil-resistant or oil-repellent resin material such as polyvinyl alcohol or an acrylic resin (see, for example, Patent Documents 2 and 3). These grease-resistant papers made with resin materials contain relatively few substances that affect the global environment and human health in the exhaust gases during combustion.

[0005] Meanwhile, with the growing momentum for global environmental protection in recent years, attempts are being made to switch from petroleum-based or petroleum-based resin materials to naturally derived materials. As for materials used in oil-resistant packaging materials, the focus is on the development of packaging materials that do not use fluororesins, and there is no particular movement to switch from the above-mentioned resin materials to naturally derived materials. However, due to the trend in the world, attempts are being made to switch all materials to naturally derived materials, and it would be meaningful to try to realize this for oil-resistant packaging materials as well.

[0006] JP 2000-026601 JP 8-209590 JP 9-3795

[0007] Therefore, an object of the present invention is to provide an oil-resistant coating agent having excellent oil resistance, which is mainly made of naturally derived materials and does not contain petroleum-based materials or resin materials that utilize petroleum-based materials, an oil-resistant coating method using the oil-resistant coating agent, and oil-resistant packaging materials and oil-resistant tableware having excellent oil resistance.

[0008] The above object can be achieved by the following aspects of the present invention: That is, an oil-resistant coating agent according to one aspect of the present invention is a two-component oil-resistant coating agent comprising a main component containing at least an alginate salt and a sub-component containing at least a polyvalent metal salt and xanthan gum.

[0009] Another aspect of the present invention is an oil-resistant coating method, which includes a main agent coating step of coating the surface of a workpiece with a main agent containing at least an alginate, and an auxiliary agent supplying step of supplying an auxiliary agent containing at least a polyvalent metal salt and xanthan gum to the main agent layer coated on the surface of the workpiece.

[0010] Another aspect of the present invention is an oil-resistant packaging material that includes a base paper and an oil-resistant layer on the surface of the base paper, the oil-resistant layer including an alginate crosslinked with a polyvalent metal and xanthan gum. The base paper preferably has a coating layer on the surface.

[0011] Furthermore, the oil-resistant tableware according to another embodiment of the present invention has an oil-resistant layer on the inner surface that comes into contact with the contents, the oil-resistant layer containing an alginate cross-linked with a polyvalent metal and xanthan gum.

[0012] According to the present invention, it is possible to provide an oil-resistant coating agent having excellent oil resistance, which is mainly made of naturally derived materials and does not contain petroleum-based materials or resin materials that utilize petroleum-based materials, an oil-resistant coating method using the oil-resistant coating agent, and oil-resistant packaging materials and oil-resistant tableware having excellent oil resistance.

[0013] 1A and 1B are schematic diagrams of a coating device using a roll coating method, in which (a) is a single-roll type and (b) is a two-roll type (kiss-touch roll) coating device. The base paper "S Pearl Card" (basis weight 260 g / m) used in Example 5 (all the same in Examples 1 to 15) ２ 1 is a chart showing the infrared absorption spectrum (FT-IR) of the surface to be coated with an oil-resistant coating of the base paper "S Pearl Card" (basis weight 310 g / m) used in Example 16. ２ 1 is a chart showing the infrared absorption spectrum (FT-IR) of the surface to be coated with an oil-resistant coating of the base paper "HPS" (basis weight 230 g / m) used in Example 17. ２ 1 is a chart showing the infrared absorption spectrum (FT-IR) of the surface to be coated with an oil-resistant coating of the base paper "Shelly SZ" (basis weight 230 g / m) used in Example 18. ２ 1 is a chart showing the infrared absorption spectrum (FT-IR) of the surface to be coated with an oil-resistant coating of the base paper "Shelly SZ" (basis weight 320 g / m) used in Example 19. ２ 1 is a chart showing the infrared absorption spectrum (FT-IR) of the surface to be coated with an oil-resistant coating of the base paper "OK ​​Frace Pro" (basis weight 260 g / m) used in Example 20. ２ 2 is a chart showing the infrared absorption spectrum (FT-IR) of the surface to be coated with an oil-resistant coating of the base paper "Frosh White Card W" (basis weight 285 g / m) used in Example 21. ２ 1 is a chart showing the infrared absorption spectrum (FT-IR) of the surface to which the oil-resistant coating of

[0014] The oil-resistant coating agent, oil-resistant coating method, oil-resistant packaging material, and oil-resistant tableware of the present invention will be described in detail below with reference to preferred embodiments.

[0015] [Oil-resistant coating agent] The oil-resistant coating agent of the present invention is a two-component oil-resistant coating agent consisting of a main agent and an auxiliary agent, which combine to form an oil-resistant coating film during use. These main agent and auxiliary agent will be explained below, and their usage will be explained in the next section [Oil-resistant coating method].

[0016] (Base Agent) The base agent in the oil-resistant coating agent of the present invention contains at least an alginate. The base agent is in the form of an aqueous solution of alginate. The term "alginate" as used herein refers to a salt of alginic acid as well as derivatives thereof.

[0017] Usable alginates include sodium alginate, ammonium alginate, potassium alginate, and propylene glycol alginate, and two or more of these may be used in combination. These alginates are designated food additives under the Food Sanitation Act and are extremely safe as raw materials for oil-resistant coating agents used in food packaging. Among these, sodium alginate is preferred from the standpoints of ease of handling and availability.

[0018] The water constituting the base agent is not particularly limited, and in addition to ordinary city water, tap water, groundwater, industrial water, etc., deionized water, pure water, purified water, etc. may be used. The base agent may also contain water-retaining agents and antifoaming agents to prevent the alginic acid from drying, colorants to color the coating film or to distinguish it from the auxiliary agents, preservatives, viscosity modifiers, dispersants, etc. It is desirable that the base agent does not contain petroleum-based materials, or even resin materials that utilize petroleum-based materials. If it does contain them, it is preferable that the content be 5% or less, and more preferably 2% or less. The base agent can be prepared by mixing these components constituting the base agent using a blender or the like.

[0019] The concentration of alginate in the base agent cannot be generalized because it depends on the type of alginate used, the method of coating the base paper, the target coating thickness, etc., and can be appropriately designed depending on the conditions and purpose.

[0020] As a rough guideline, the upper limit of the alginate concentration in the base agent is preferably 20% or less by mass, more preferably 15% or less, and even more preferably 12% or less. If the alginate concentration in the base agent is too high, the viscosity may become too high, making it difficult to achieve a uniform coating, which is undesirable.

[0021] Similarly, the lower limit of the alginate concentration in the base agent is preferably 0.1% or more by mass, more preferably 1% or more, and even more preferably 5% or more. If the alginate concentration in the base agent is too low, the viscosity will be too low, making it difficult to ensure a sufficient film thickness, which is undesirable.

[0022] (Secondary Agent) The secondary agent in the oil-resistant coating agent of the present invention contains at least a polyvalent metal salt and xanthan gum. The secondary agent is in the form of an aqueous solution in which the polyvalent metal salt and xanthan gum are mixed. The "polyvalent metal salt" referred to here is a salt of a metal that becomes a divalent or higher cation, and is a salt of a metal ion that undergoes a crosslinking reaction with the alginate contained in the main agent.

[0023] Usable polyvalent metal salts include calcium salts, magnesium salts, barium salts, iron salts, copper salts, aluminum salts, and zinc salts. Specific examples include calcium chloride, calcium acetate, calcium carbonate, calcium citrate, calcium sulfate, calcium lactate, magnesium chloride, magnesium carbonate, ferric chloride, ferrous citrate, ferrous sulfate, and ferrous lactate. These polyvalent metal salts are food additives (designated additives) under the Food Sanitation Act, and are extremely safe as raw materials for oil-resistant coating agents used in food packaging materials. Among these, calcium chloride is preferably used from the standpoints of ease of handling and availability.

[0024] The concentration of the polyvalent metal salt in the auxiliary agent cannot be generalized because it depends on the type of polyvalent metal salt used, the type of alginate in the main agent coated on the base paper, the coating film thickness, etc., and can be designed appropriately depending on the conditions, purpose, etc. When designing the formulation of the auxiliary agent, the concentration in the auxiliary agent can be adjusted so that the required amount of polyvalent metal salt is supplied depending on the amount of alginate in the main agent coated on the base paper and the desired degree of crosslinking.

[0025] As a rough guideline, when the polyvalent metal salt in the auxiliary agent is calcium chloride, the upper limit of its concentration is preferably 20% or less by mass, more preferably 10% or less. If the concentration of the polyvalent metal salt in the auxiliary agent is too high, there is a risk that the unreacted portion with the alginate will precipitate on the surface of the coating film, which is undesirable.

[0026] Similarly, when the polyvalent metal salt in the main agent is calcium chloride, the lower limit of its concentration is preferably 0.1% or more by mass, more preferably 0.3% or more, and even more preferably 0.5% or more. If the concentration of the polyvalent metal salt in the auxiliary agent is too low, it is undesirable because it becomes difficult to supply the amount of polyvalent metal salt necessary for crosslinking the alginate.

[0027] In the case of polyvalent metal salts other than calcium chloride, the concentration may be appropriately determined in the same manner as in the case of calcium chloride, taking into consideration the atomic weight and reactivity of the elements contained therein.

[0028] The auxiliary agent in the oil-resistant coating agent of the present invention contains xanthan gum as an essential component. In the auxiliary agent, xanthan gum primarily functions as a thickener. As described below, the auxiliary agent is supplied to the layer of the main agent coated on the base paper. However, supplying an aqueous solution of only a polyvalent metal salt would result in a viscosity that is too low.

[0029] That is, when a low-viscosity auxiliary agent is supplied to a planar target surface, the auxiliary agent spreads or is repelled, making it difficult to ensure the supply amount of the auxiliary agent. In particular, when the method for supplying the auxiliary agent to the target surface is the roll coating method (see FIG. 1), if the viscosity of the auxiliary agent is too low, it becomes difficult to retain it on the surface of the pickup roll (also called the applicator roll), making it difficult to supply a sufficient amount of auxiliary agent to the base agent layer. Furthermore, in the case of the bar coating method, the wet film after supply is repelled, making it difficult to apply the auxiliary agent uniformly to the entire surface. Therefore, in the present invention, xanthan gum is used as a viscosity modifier to increase the viscosity of the auxiliary agent.

[0030] By using xanthan gum as a viscosity modifier in the auxiliary agent, it is possible to achieve appropriate viscosity with a small amount of addition and achieve high oil resistance. Furthermore, even in the presence of moisture, the coating surface is less likely to become slimy, minimizing the impact on food that comes into contact with it and causing no discomfort to the consumer. Furthermore, alginate crosslinked films are vulnerable to excessive drying, but the xanthan gum remaining inside and on the surface of the coating film after the crosslinking reaction with the polyvalent metal salt in the auxiliary agent functions as a moisturizing agent to maintain moisture, protecting the coating film. As a thickening polysaccharide, xanthan gum is a food additive (existing additive) under the Food Sanitation Act, and is extremely safe as a raw material for oil-resistant coating agents used in food packaging materials.

[0031] The lower limit of the xanthan gum concentration in the auxiliary agent cannot be generally determined because it depends on the method of supplying the auxiliary agent to the target surface and various other conditions. For example, in the case of a supply method in which the auxiliary agent is directly supplied to the target surface, such as a spray method or a bar coating method, a relatively low viscosity is sufficient as long as the wet film after supply is maintained without being repelled. However, in the case of a roll coating method in which a liquid auxiliary agent is held on the surface of a pickup roll and then transferred to the target surface, a certain degree of high viscosity is required to hold the auxiliary agent on the roll surface. Furthermore, even in the case of the roll coating method, the required viscosity differs depending on whether the pickup roll is, for example, a gravure roll having unevenness on its surface due to engraving processing, or a mirror-finished roll having a mirror-finished surface.

[0032] Specifically, for example, when the pickup roll is a gravure roll, the lower limit of the xanthan gum concentration is preferably about 0.04% or more, more preferably 0.06% or more, by mass, although this depends on the degree of unevenness of the pickup roll. In this case, the viscosity of the auxiliary agent measured by a Brookfield viscometer (rotation speed: 30 rpm (revolutions / min), temperature condition: 25°C; the same applies hereinafter) is preferably 15 mPa s or more, more preferably 20 mPa s or more.

[0033] Furthermore, when the pickup roll is a mirror-finish roll, the lower limit of the xanthan gum concentration is preferably approximately 0.06% or more by mass, and more preferably 0.09% or more. In this case, the viscosity of the auxiliary agent measured by a Brookfield viscometer is preferably 20 mPa·s / 25°C or more, and more preferably 50 mPa·s / 25°C or more. In addition, when a supply method in which the auxiliary agent is directly supplied to the target surface, such as spray coating, bar coating, flow coating, or curtain coating, is used, the concentration is preferably approximately 0.02% or more by mass, and more preferably 0.04% or more. In this case, the viscosity of the auxiliary agent measured by a Brookfield viscometer is preferably 5 mPa·s / 25°C or more, and more preferably 15 mPa·s / 25°C or more.

[0034] On the other hand, the upper limit of the concentration of xanthan gum in the auxiliary agent is preferably 0.3% or less by mass, more preferably 0.26% or less, even more preferably 0.21% or less, and particularly preferably 0.18% or less. If the concentration of xanthan gum in the auxiliary agent is too high, slime will form when moisture comes into contact with the surface of the formed coating film, which may have an adverse effect on food that comes into contact with the film, which is undesirable.

[0035] Furthermore, the upper limit of the viscosity of the auxiliary agent measured with a Brookfield viscometer is preferably 500 mPa·s or less, more preferably 350 mPa·s or less, even more preferably 200 mPa·s or less, and particularly preferably 150 mPa·s or less. If the viscosity of the auxiliary agent is too high, the applicability decreases, which is undesirable. It is preferable to target a viscosity of around 100 mPa·s as measured with a Brookfield viscometer.

[0036] The water constituting the auxiliary agent is the same as that of the main agent. The auxiliary agent may also contain colorants, preservatives, dispersants, antifoaming agents, etc. to distinguish it from the main agent. As with the main agent, it is desirable that the auxiliary agent does not contain petroleum-based materials, or even resin materials that utilize petroleum-based materials. If it does contain petroleum-based materials, the content is preferably 5% or less, and more preferably 2% or less. The auxiliary agent can be prepared by mixing the components constituting these auxiliary agents using a blender or the like.

[0037] [Oil-resistant coating method] The oil-resistant coating method of the present invention comprises a main agent coating step and an auxiliary agent supplying step. The main agent coating step and the auxiliary agent supplying step are preferably performed in this order, but the order may be reversed. Furthermore, when the main agent coating step is performed first, it is preferable to have a first drying step between the main agent coating step and the auxiliary agent supplying step, and a second drying step after the auxiliary agent supplying step. Each of these steps will be explained below.

[0038] (Base Coating Step) The base coating step in the oil-resistant coating method of the present invention is a step of coating the surface of the object to be treated with a base containing at least alginate. The base is as described in the section on the oil-resistant coating agent of the present invention. The "surface of the object to be treated" here refers to the surface of the base paper when an oil-resistant packaging material is to be obtained, and to the inner surface of the tableware that comes into contact with the contents when an oil-resistant tableware is to be obtained. In this way, when oil-resistant tableware is to be obtained, the shape of the tableware may first be formed and then the inner surface may be coated with the base material or the like to form an oil-resistant layer, as described below. Alternatively, an oil-resistant layer may be formed on the base paper to obtain an oil-resistant packaging material, and then the oil-resistant packaging material may be formed into the shape of the tableware.

[0039] The "base paper" as the treated material refers to a sheet that serves as the base of the oil-resistant packaging material, and typically uses so-called paper made by entangling fibers of plants or the like, combing them into a film, and drying them. However, fibers other than plants may also be used, components other than fibers may be included, and woven or nonwoven fabrics of various fibers may also be used. Furthermore, any film-like sheet can be used as the base paper in the present invention, even if it is not made from fibrous raw materials. In other words, the "base paper" in the present invention is a concept that also includes sheets that do not correspond to paper.

[0040] The base paper preferably has a coating layer on the surface on which the oil-resistant layer is to be formed. The coating layer formed on the surface of the base paper is generally formed by adding pigments and other additives to a binder, but the pigments and other additives are not essential components. As mentioned above, the "surface" here refers to the surface on which the oil-resistant layer is to be formed, and differs from the surface of ordinary paper, which is provided with a coating layer to improve design and printability, giving it a glossy, shiny, or other outer surface. In this case, the oil-resistant layer is formed on the surface that would be the back side of ordinary paper, and it is preferable to have a coating layer on this surface.

[0041] Examples of binders used in the coating layer include latexes such as styrene-butadiene latex, styrene-acrylic latex, and ethylene-vinyl acetate latex; natural polymers such as starch, casein, and soy protein; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; and synthetic polymers such as polyvinyl alcohol and alkali-soluble resins.

[0042] Pigments that can be incorporated into the coating layer include inorganic pigments such as natural mineral pigments, such as clay, talc, and ground calcium carbonate; composite synthetic pigments, such as satin white and litton; and semi-synthetic pigments, such as titanium oxide, precipitated calcium carbonate, and alumina hydroxide; as well as organic pigments, such as plastic pigments.

[0043] The thickness of the coating layer is not particularly limited, but is generally about 2 μm to 30 μm. The base paper having a coating layer on its surface may be any of various types of paper or coated paper that are commercially available with a coating layer on the surface on which the oil-resistant layer is formed. Specific examples include "S Pearl Card" manufactured by Mitsubishi Paper Mills, Ltd., "Shelly SZ" manufactured by Chuetsu Pulp & Paper Co., Ltd., "HPS" manufactured by Hokuetsu Corporation, "OK Frace Pro" manufactured by Oji Paper Co., Ltd., and "Frosh White Card W" manufactured by Nippon Paper Industries Co., Ltd.

[0044] Incidentally, some commercially available papers and coated papers are uncoated or coated on one side because they do not have a so-called coating layer, which provides gloss or luster for improving design or printability, on both sides or the back side (the side corresponding to the surface on which the oil-resistant layer is formed in this invention). However, even such uncoated sides may have a coating layer suitable for the surface on which the oil-resistant layer is formed. In other words, a coating layer suitable for the base paper in this invention may be an extremely thin coating layer that does not correspond to a so-called coating layer. Conversely, a thick coating layer exceeding 30 μm may be undesirable for the base paper to which this invention is applied.

[0045] Furthermore, the "tableware" as the object to be treated may be tableware made of paper such as paper plates, paper bowls, and paper cups, as well as tableware made of sheets using various fibers, similar to base paper, or other types of sheets. In other words, the concept of "tableware" in the present invention also includes tableware made of sheets that do not correspond to paper.

[0046] As a method for coating the base material, various conventionally known coating methods can be used. Specific examples include roll coating, spray coating, bar coating, flow coating, curtain coating, dip coating, slot die coating, lip coating, knife coating, and brush coating. When the substrate is a "base paper," it is preferable to use roll coating, because it has a simple and low-cost device configuration, is suitable for mass production, and can easily obtain a relatively uniform film thickness.

[0047] Figure 1 shows a schematic diagram of a coating device using the roll coating method. (a) in Figure 1 is an example of a single-roll type coating device, and (b) is an example of a two-roll type (kiss-touch roll) coating device. In the single-roll type coating device (hereinafter referred to as "coating device A"), as shown in Figure 1(a), a strip-shaped base paper 1 wound in n coils (not shown) is unwound, sent from the previous process, and proceeds in the direction of arrow A, where it wraps around a backup roll 2 for just under half a turn, changes direction, and is sent to the next process.

[0048] The top of the pickup roll 3 is disposed opposite the backup roll 2 with the base paper 1 interposed therebetween. The base paper 1 is inserted between the backup roll 2 and the pickup roll 3. In this device, the portion where the backup roll 2 and the pickup roll 3 face each other forms the nip portion Na where the pickup roll 3 and the base paper 1 come into contact. The bottom of the pickup roll 3 is immersed in the supply liquid 5 stored in the liquid tank 4, submerged below the liquid surface of the supply liquid 5. When this coating device is used for a base agent coating process, the base agent as the supply liquid 5 is stored in the liquid tank 4.

[0049] In the example of Fig. 1, the pickup roll 3 rotates in either the forward direction of arrow L (hereinafter referred to as forward rotation L) or the reverse direction of arrow R (also called "reverse", hereinafter referred to as reverse rotation R). Pits 31 are formed on the surface (circumferential surface) of the pickup roll 3 by engraving. In the example of Fig. 1, the pickup roll 3 is depicted as rotating in the forward direction L.

[0050] As the pickup roll 3 rotates from a state immersed in the supply liquid 5 to a state above the liquid surface of the supply liquid 5, it scoops up the supply liquid 5 into the pits 31. The supply liquid 5 is carried to the nip Na while still held in the pits 31, and is transferred to the surface of the base paper 1 that is being inserted into the nip Na. The pits 31, which have been emptied after transferring the supply liquid 5 to the surface of the base paper 1, are again immersed in the supply liquid 5 by the forward rotation L of the pickup roll 3, scooping up the supply liquid 5, and are ready to transfer the next supply liquid 5 to the surface of the base paper 1. An air knife device (not shown) may be provided that blows air onto the surface of the base paper 1 to which the supply liquid 5 has been transferred, thereby leveling the amount of supply liquid 5 that has adhered.

[0051] On the other hand, a two-roll type coating device (hereinafter referred to as "coating device B") is equipped with two backup rolls 2a and 2b, as shown in Figure 1(b). In coating device B, a band-shaped base paper 1 wound in a coil (not shown) is unwound and fed from the previous process in the direction of arrow A, where it is wound around each of the two backup rolls 2a and 2b in turn, changes direction, and is sent to the next process. The two backup rolls 2a and 2b are spaced apart by a certain distance.

[0052] The top of the pickup roll 3 is disposed opposite each of the two backup rolls 2a, 2b, with the base paper 1 interposed between them. The base paper 1 is inserted between the two backup rolls 2a, 2b and the pickup roll 3. In this device, the arc portion on the outer periphery of the pickup roll 3 between the portion facing the backup roll 2a and the portion facing the backup roll 2b forms the nip portion Nb where the pickup roll 3 and the base paper 1 come into contact. In other words, compared to coating device A, coating device B has a higher efficiency in transferring the transfer liquid 51 from the pickup roll 3 to the base paper 1. It is also possible to first transfer the supply liquid 5 from the pickup roll 3 to another transfer roll (not shown) and then coat the base paper 1.

[0053] In both coating device A and coating device B, reverse coating can be performed by rotating the pickup roll 3 in the reverse direction R. In reverse coating, the peripheral surface of the pickup roll 3 rubs against the surface of the base paper 1 moving in the direction of arrow A, transferring the transfer liquid 51 onto the surface of the base paper 1. Reverse coating increases the contact area of ​​the peripheral surface of the pickup roll 3 per unit area of ​​the base paper 1, allowing more supply liquid 5 to be supplied.

[0054] As a method for coating the base material, either of the coating apparatuses A and B described with reference to Figures 1(a) and 1(b) can be used, which employ a roll coating method. The rotation direction of the pickup roll 3 can be either forward rotation L or reverse rotation R.

[0055] 1(a) and 1(b), a gravure roll having an engraved surface and irregularities is used as the pickup roll 3, but a mirror-finished roll having a mirror-finished surface may also be used. In FIGS. 1(a) and 1(b), the pits 31 are exaggerated by being drawn extremely long in the circumferential direction for the sake of explanation, but in reality they are extremely minute recesses, and the transferred coating layer 52 becomes a uniform, planar coating film with almost no trace of the shapes of the pits 31 remaining.

[0056] In the above example, the roll coating method is used to coat the base paper, but if other coating methods are used, the base agent can be coated by a conventionally known method depending on the type of object to be treated (base paper or tableware).

[0057] The amount of coating of the base agent in the base agent coating process cannot be generalized depending on the required level of oil resistance and the required level of cost reduction of the amount of base agent used, but in order to achieve a kit value of 6 or more according to the kit method described below, the dry mass of the base agent should be 1.5 g / m ２ It is preferable that the content is 1.8 g / m or more. ２ More preferably, it is 2.0 g / m or more. ２More preferably, it is equal to or greater than this.

[0058] On the other hand, there is no particular upper limit to the amount of coating of the main agent, but if it is too thick, the material will be wasted and the thickness of the packaging material will increase, making it difficult to handle. Therefore, it is set to about 10 g / m ２ Preferably, it is 5 g / m or less. ２ More preferably, it is:

[0059] (First Drying Step) The base paper whose surface has been coated with the base agent in the base agent coating step is dried in the first drying step until the base agent layer has formed to a certain extent. Drying methods include placing the base paper in a heated oven, passing it through a similar oven as in a production line process, exposing the base paper to hot, warm, or cold air, or leaving it in the air to dry naturally. If the base paper is simply stacked until it dries naturally between the steps after the base agent coating step, or if sufficient time is ensured for it to dry naturally as in a production line process, these are considered to be operations in the "first drying step," and no special operation as this step is necessary.

[0060] When an oven is used or hot or warm air is applied in this step, it is desirable not to dry the coating film of the base agent too much, so it is preferable to do so in an environment of 130°C or less for about 10 to 120 seconds.

[0061] (Subsidiary agent supplying step) In the oil-resistant coating method of the present invention, the auxiliary agent is supplied to the layer of the main agent coated on the surface of the base paper. The auxiliary agent is as described in the section on the oil-resistant coating agent of the present invention.

[0062] As a method for supplying the auxiliary agent, various conventionally known application methods such as those mentioned in the main agent coating process can be used. In this process, as in the main agent coating process, it is preferable to use a roll coating method, as it is suitable for mass production with a simple and low-cost device configuration and can easily achieve a relatively uniform supply amount. It is desirable to supply the auxiliary agent in an environment of 5 to 40°C and a humidity of 20 to 80%.

[0063] The coating apparatus A and coating apparatus B described above with reference to Figures 1(a) and 1(b) can also be used as a method for coating the auxiliary agent in this auxiliary agent supplying step. Furthermore, the rotation direction of the pickup roll 3 can be either forward rotation L or reverse rotation R. Furthermore, similar to the main agent coating step, various conditions can be appropriately selected for the pickup roll 3, such as a gravure roll or a mirrored roll.

[0064] The amount of the auxiliary agent to be supplied in the auxiliary agent supplying step cannot be generally determined depending on the dry mass of the main agent coated on the base paper, the concentration of the polyvalent metal salt in the auxiliary agent to be supplied, etc., and it is sufficient to design the supply so that a sufficient amount of polyvalent metal salt can be supplied for the crosslinking reaction with the alginate. A specific wet mass of the auxiliary agent to be supplied is 5 g / m ２ It is preferable that the content is 10 g / m or more. ２ On the other hand, there is no particular upper limit to the coating amount of the auxiliary agent, and the upper limit is naturally determined depending on the viscosity of the auxiliary agent, the supply method, etc.

[0065] (Second drying step) In the layer of the main agent to which the auxiliary agent is supplied by the operation of the auxiliary agent supply step, the alginate in the main agent and the polyvalent metal in the auxiliary agent undergo a cross-linking reaction to form a cross-linked body.Then, in order to evaporate excess water, it is dried by the second drying step.As the drying method in the second drying step, any of the drying methods described in the first drying step (including the case where no special operation is performed) can be adopted.The drying temperature, drying time, etc. also follow the conditions described in the first drying step.

[0066] [Oil-resistant packaging material, oil-resistant tableware] As described in the preceding section [Oil-resistant coating method], the two-component oil-resistant coating agent of the present invention can be used to produce articles such as oil-resistant packaging material and oil-resistant tableware of the present invention by operating the oil-resistant coating method of the present invention.

[0067] The oil-resistant packaging material of the present invention has an oil-resistant layer on the surface of a base paper, the oil-resistant layer containing a polyvalent metal-crosslinked alginate and xanthan gum. The oil-resistant tableware of the present invention also has an oil-resistant layer on the inner surface that comes into contact with the contents, the oil-resistant layer containing a polyvalent metal-crosslinked alginate and xanthan gum. The formed oil-resistant layer has xanthan gum in the gaps between the mesh-like membrane of the polyvalent metal-crosslinked alginate, and also present on the surface of the membrane.

[0068] Even when alginate is cross-linked with a polyvalent metal to form a cross-linked body, it is vulnerable to excessive drying, which may lead to pinholes, cracks, and even film collapse. However, in the oil-resistant packaging material of the present invention, xanthan gum penetrates into the oil-resistant layer and is present on the surface of the film, so it functions as a moisturizing agent to maintain moisture and protect the film.

[0069] Specific examples of oil-resistant packaging materials include packaging materials in the form of sheets, bags, boxes, trays, and cups. Specific examples of oil-resistant tableware include tableware such as plate-, bowl-, and cup-shaped containers (paper plates, paper bowls, paper cups, etc.), cutlery (paper spoons, paper forks, etc.), and straws (paper straws).

[0070] The oil-resistant coating agent, oil-resistant coating method, oil-resistant packaging material, and oil-resistant tableware of the present invention have been described above using preferred embodiments, but the oil-resistant coating agent, oil-resistant coating method, and oil-resistant packaging material of the present invention are not limited to the configurations of the above embodiments. Those skilled in the art can appropriately modify the oil-resistant coating agent, oil-resistant coating method, oil-resistant packaging material, and oil-resistant tableware of the present invention in accordance with conventional knowledge. Of course, such modifications are within the scope of the present invention as long as they still have the configuration of the present invention.

[0071] The oil-resistant coating agent, oil-resistant coating method, and oil-resistant packaging material of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0072] (1) Preparation of Main Agent A 10% (by mass) aqueous solution of sodium alginate was prepared, and this was designated as main agent M.

[0073] (2) Preparation of auxiliary agents for the examples Aqueous solutions were prepared so that the calcium chloride concentration was 5% (by mass) and the xanthan gum concentration was as shown in Table 1 below, and these were designated auxiliary agents J1 to J8 for the examples. The xanthan gum used was "Labor Gum (registered trademark) GS-C" manufactured by MP Gokyo Food & Chemical Co., Ltd. (the same applies hereinafter).

[0074] (3) Viscosity measurement of auxiliary agents The prepared auxiliary agents J1 to J8 and auxiliary agents H1 to H5 were measured for viscosity using a Brookfield viscometer at a rotation speed of 30 rpm (revolutions per minute) and a temperature of 25° C. The results are summarized in Table 1 below.

[0075] (4) Operation and Evaluation of Oil-Resistant Coatings in Examples 1 to 8 (4-1) Main Agent Coating Step Main agent M prepared using a coater machine was applied to a base paper using a #14 bar coater, resulting in a wet supply amount of 21 g / m ２ (Dry film thickness is 2.1 g / m ２ This is referred to as A-1 in Table 1 below.) The coating was carried out by the bar coating method. This coating operation was carried out in an environment of room temperature (around 20°C). The same conditions were used for the auxiliary agent supplying step described below. The base paper was "S Pearl Card" (basis weight 260 g / m) manufactured by Mitsubishi Paper Mills Co., Ltd. ２ A sheet of paper (25 cm x 20 cm in size) was used, and the back side of the surface to be used as the coating layer (glossy surface) was coated with the main agent.

[0076] (4-2) First Drying Step The base paper coated with the main component M was dried in a drying oven at a temperature of 120° C. for 30 seconds to form a coating film of the main component M.

[0077] (4-3) Subsidiary Agent Supplying Step After the base paper on which the coating film was formed was left to stand for 24 hours or more in an environment of a temperature of 23°C and a humidity of 50% RH, the auxiliary agent shown in the "Type" column of Examples 1 to 8 in Table 1 below was applied onto the coating film of the main agent coated on the surface of the base paper using a #20 bar coater without applying pressure, so that the supply amount in the wet state was 30 g / m.２ The coating was carried out by the bar coating method so that the thickness was equal to or greater than the above. The coating state at this time was evaluated as "suitability for the supply of auxiliary agents" according to the following criteria. The results are summarized in Table 1 below. ○: Uniform and good supply (coating) was possible. △: Unevenness occurred, but supply (coating) was possible over the entire area. ×: The viscosity was too low to spread, and supply (coating) over the entire area was not possible.

[0078] (4-4) Second drying step The base paper coated with the main agent and supplied with the auxiliary agent was placed in an oven heated to 120°C and dried for 70 seconds to form an oil-resistant coating film, thereby obtaining an oil-resistant packaging material (number of layers = 4). The state of crosslinking of the formed coating film was confirmed and evaluated as "crosslinked state" according to the following criteria. The results are summarized in Table 1 below. ○: Entirely crosslinked. △: Insufficient crosslinking. ×: Not crosslinked.

[0079] (4-5) Evaluation of Slime When Water is Dropped Water was dropped in a line to a width of about 5 mm and a length of about 150 mm onto the oil-resistant coating film of the oil-resistant packaging material of Examples 1 to 8, and after leaving it for 1 minute, the state of slime was evaluated by touching with a finger according to the following criteria. The results are summarized in Table 1 below. ◎: No slime felt. ○: Almost no slime felt. △: Slight slime felt. ×: Slime felt.

[0080] (4-6) Evaluation of Kit Value The kit values ​​of the oil-resistant coating films of the oil-resistant packaging materials of Examples 1 to 8 were determined by the oil repellency test method for paper and paperboard (kit method) specified in JAPAN TAPPI Paper and Pulp Test Method No. 41. The values ​​determined for n=4 were averaged to obtain the kit value of the evaluation results, which were evaluated according to the following criteria. The results are summarized in Table 1 below. ◎: 8 or more ○: 5 or more but less than 8 △: 2 or more but less than 5 ×: Less than 2

[0081] (4-7) Evaluation of the number of pinholes About 2.5 ml of Kit 16 reagent (heptane 100%) used in the kit method was dropped onto the oil-resistant coating film of the oil-resistant packaging material of Examples 1 to 8, and after leaving it for 15 seconds, ２ The number of pinholes was visually counted and evaluated according to the following criteria. The results are summarized in Table 1 below: ⊚: 25 or less ◯: 26 to 50 △: 51 or more

[0082] (5) Operation and Evaluation of Oil-Resistant Coatings in Examples 9 to 15 In "(4) Operation and Evaluation of Oil-Resistant Coatings in Examples 1 to 8," the dry film thickness of the base material was 3.6 g / m for Examples 9 and 10. ２ (In Table 1, this is indicated as A-2), and Examples 13, 14, and 15 are 4.3 g / m ２ (In Table 1, this is designated as A-3.) In addition, J4 was used as the auxiliary agent, and oil-resistant coating operations were carried out and evaluated in the same manner as in Examples 1 to 8, except that the auxiliary agent supplying step (4-3) was replaced by a supplying method using a roll coating method, and the drying time in the second drying step (4-4) was set to 15 seconds. The results are summarized in Table 1 below.

[0083] For roll coating, a kiss-touch type device as shown in Figure 1(b) was used. A gravure roll (roll diameter 240 mm) having a surface with oblique lines 70 was used as the pickup roll 3. In Examples 9, 11, and 13, forward rotation L was used, and the base paper feed speed (roll surface movement speed) was 24 m / min. In Examples 10, 12, 14, and 15, reverse rotation R (reverse) was used, and the base paper feed speed and roll surface movement speed were both 24 m / min. In Examples 12 and 15, an air knife device was operated to blow air onto the surface of the base paper to which the auxiliary agent had been supplied. The amount of auxiliary agent supplied when wet (the amount supplied after the air knife was activated if an air knife was used) was 10 g / m ２ In Example 12, the coating amount was 13 g / m ２ and 11 g / m ２ 15g / m2 with forward and reverse rotation R (without air knife) ２ It is estimated to be around 10:00.

[0084] The evaluation criteria for "supply suitability of auxiliary agent" were as follows: ◯: Adhered well to the pickup roll and was evenly transferred to the base paper. △: Adhered to the pickup roll, but unevenness occurred during transfer to the base paper. ×: Repelling was observed on the surface of the pickup roll, and it was not possible to transfer to the entire base paper.

[0085] (6) Preparation of Comparative Examples: In "(2) Preparation of Examples," an aqueous solution containing no xanthan gum was prepared, and this was designated Comparative Example auxiliary agent H1. Similarly, aqueous solutions were prepared using a thickener (hydroxypropyl guar gum or guar gum) shown in Table 1 below instead of xanthan gum, to the concentrations shown in Table 1, and these were designated Comparative Example auxiliary agents H2 to H5.

[0086] (7) Operation and Evaluation of Oil-Resistant Coatings of Comparative Examples 1 to 5 The operation and evaluation of oil-resistant coatings were carried out in the same manner as in Examples 1 to 8, except that the auxiliary agents used in "(4) Operation and Evaluation of Oil-Resistant Coatings of Examples 1 to 8" were changed to auxiliary agents H1 to H5. The results are summarized in Table 1 below.

[0087]

[0088] (8) Discussion of the results of Examples 1 to 15 and Comparative Examples 1 to 5 As can be seen from the results of Examples 1 to 15, a two-component oil-resistant coating agent containing an aqueous solution of alginate as the main agent, a sub-agent containing calcium chloride as a cross-linking agent, and xanthan gum was used to form a coating film that was homogeneous and had excellent oil resistance, and which did not or only slightly became slimy when it came into contact with water.

[0089] In contrast, in Comparative Example 1, in which xanthan gum was not blended as an auxiliary agent, the supply of the auxiliary agent was non-uniform, resulting in variations in film thickness. On the other hand, in Comparative Examples 2 and 3, in which hydroxypropyl guar gum was used as an auxiliary agent, the blending amount was too large to achieve a viscosity with excellent auxiliary agent supply suitability (Comparative Example 2), and both Comparative Examples 2 and 3 felt slimy when in contact with water. When guar gum was blended in the same amount (Comparative Examples 4 and 5), the supply of the auxiliary agent was non-uniform, resulting in variations in film thickness, and the film felt slimy when in contact with water.

[0090] (9) Test to Confirm the Influence of Base Paper (Examples 16 to 21, Comparative Examples 6 to 9) In Example 5, only the base paper was replaced with that shown in Table 2 below (size 25 cm × 20 cm), and the main agent and the sub-agent were prepared under all other conditions identical to those of Example 5, and the operations (4-1) to (4-4) in the section "(4) Procedures and Evaluation of Oil-Resistant Coatings in Examples 1 to 8" (excluding the evaluation of the crosslinked state) were carried out to coat the base paper, thereby obtaining the oil-resistant packaging materials of Examples 16 to 21 (n number = 4).

[0091] The surface on which the oil-resistant coating layer was formed was evaluated for processability using the following evaluation criteria. In the evaluation criteria below, "left and right" refer to both sides perpendicular to the direction of coating by the bar coater. "Bottom" refers to the vicinity of the edge on the side where coating by the bar coater ends. The results are summarized in Table 2 below.

[0092] ◎: No scratches are found on the oil-resistant coating layer, or slight scratches less than 0.5 mm wide are found on the left and right sides of the oil-resistant coating layer. ○: Scratches less than 0.5 mm wide are found on the left and right sides and lower center of the oil-resistant coating layer. △: Scratches 0.5 mm wide or more are found on the left and right sides and lower center of the oil-resistant coating layer. ×: Significant scratches are found over the entire surface. -: The liquid has penetrated deep into the base paper.

[0093] The base papers used in Examples 5, 16, 18 and 19 were left as they were without any coating, and were designated Comparative Examples 6 to 9, respectively.

[0094] The infrared absorption spectrum (FT-IR) charts of the oil-resistant coating surface of the base paper used in Examples 5 and 16 to 21 are shown in Figures 2 to 8. In these FT-IR charts, －１ ~1600cm －１ The absorption peak observed between is considered to represent the presence of the coating layer.

[0095] Furthermore, the base papers used in Examples 5 and 16-21 were subjected to a water resistance test using the Edgewick method, in which the time required for water to penetrate all layers was measured. In the Edgewick method, the base paper was cut into 1 cm x 5 cm pieces, waterproof tape was attached to the front and back of each piece, and the piece was immersed in room temperature water to measure the time required for water to penetrate all layers. The results are summarized in Table 2 below.

[0096] The evaluation criteria for the water resistance test of this base paper were as follows: ◎: Not penetrated to the entire layer even after 24 hours of immersion. ○: Not penetrated to the entire layer even after 18 hours of immersion, but fully penetrated within 24 hours. △: Not penetrated to the entire layer even after 12 hours of immersion, but fully penetrated within 18 hours. ×: Penetrated to the entire layer within 12 hours of immersion.

[0097] The obtained oil-resistant packaging materials of Examples 15 to 21 and the papers of Comparative Examples 6 to 9 were subjected to "(4-6) Evaluation of Kit Value" in the same manner as in Examples 1 to 8. These results are shown together with the results of Example 5 in Table 2 below.

[0098]

[0099] (10) Test to confirm the adhesion of the auxiliary agent to the surface of the roll The following test was carried out to confirm the adhesion of the auxiliary agent to the surface of the pickup roll. First, a test machine was prepared by removing the backup roll 2 and the base paper 1 from the coating apparatus shown in Figure 1(a). For the pickup roll 3, a mirror-finished roll with a roll diameter of 80 mm and a gravure roll with 70 oblique line irregularities were used.

[0100] Secondary agents J1 to J7 and secondary agent H1 were charged into liquid tank 4 as supply liquid 5. The roll was rotated so that the movement speed of the roll surface was 2 m / min, 5 m / min, and 10 m / min, and the adhesion state of the secondary agent at each movement speed was confirmed. The results are shown in Table 3 below. The evaluation criteria are as follows. When two evaluations are listed, it means that the state is intermediate between the two evaluation indices. ○ High: Adhered well to the pickup roll. The amount of adhesion was clearly large. ○: Adhered well to the pickup roll. △: Adhered to the pickup roll but unevenness was confirmed. ×: Repelling was observed on the surface of the pickup roll.

[0101]

[0102] (10) Discussion of the results of the test to confirm the adhesion of auxiliary agents to the roll surface For auxiliary agents J1 to J7 used in the examples, the auxiliary agents could be adhered to the roll surface by appropriately controlling the movement speed of the roll surface for both the mirrored roll and the gravure roll. In particular, J3 to J5, which contained xanthan gum in an amount of 0.1 to 0.175% by mass, showed good adhesion under all conditions. Furthermore, the gravure roll showed good adhesion even when the xanthan gum concentration was lower than that of the mirrored roll.

[0103] 1: Base paper, 2, 2a, 2b: Backup roll, 3: Pick-up roll, 31: Pit, 4: Liquid tank, 5: Supply liquid, 51: Transfer liquid, 52: Coating layer

Claims

1. A two-component oil-resistant coating agent comprising a main agent containing at least an alginate salt and a sub-agent containing at least a polyvalent metal salt and xanthan gum.

2. An oil-resistant coating method comprising: a base agent coating step of coating the surface of a workpiece with a base agent containing at least an alginate; and an auxiliary agent supplying step of supplying an auxiliary agent containing at least a polyvalent metal salt and xanthan gum to the layer of the base agent coated on the surface of the workpiece.

3. An oil-resistant packaging material having an oil-resistant layer on the surface of a base paper, the layer containing an alginate crosslinked with a polyvalent metal and xanthan gum.

4. The oil-resistant packaging material according to claim 3, wherein the base paper has a coating layer on the surface.

5. An oil-resistant tableware having an oil-resistant layer on the inner surface that comes into contact with the contents, the oil-resistant layer comprising an alginate cross-linked with a polyvalent metal and xanthan gum.