Sheet and method for manufacturing the sheet

Abstract

To provide a sheet having an excellent oil resistance and low air resistance.SOLUTION: There is provided a sheet according to the embodiment comprises: a fibrous base material having fibers; and a fatty acid ester impregnated into the fibers of the fibrous base material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a sheet and a method for manufacturing the sheet. [Background technology]

[0002] It has been known in the field of food packaging materials and the like that fibrous substrates such as paper are processed to make them less susceptible to oil penetration. Specific processing methods include coating the fibrous substrate with a fluorine-based oil-resistant agent, or attaching a resin film such as polyethylene or a cured resin film to the fibrous substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5804300 Summary of the Invention [Problem to be solved by the invention]

[0004] However, fluorine-based oil-resistant agents can generate harmful gases when heated in a microwave oven, etc. Also, when a resin film or a cured resin film is laminated to a fibrous substrate, there is a problem that the air resistance increases.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a sheet that has excellent oil resistance and low air permeability resistance. [Means for solving the problem]

[0006] [1] A sheet comprising a fibrous base material having fibers and a fatty acid ester impregnated into the fibers of the fibrous base material. [2] The sheet according to [1], wherein the fatty acid ester has a softening point of 25°C or higher. [3] The sheet according to [1] or [2], wherein the fatty acid ester has a softening point of 150°C or lower. [4] The sheet according to any one of [1] to [3], wherein gaps are maintained between the fibers of the fibrous base material. [5] The sheet according to any one of [1] to [4], wherein the air permeability resistance of the sheet based on JIS P8117:2009 is 58 s / 100 mL or less. [6] The sheet according to any one of [1] to [5], wherein the fatty acid ester is at least one selected from the group consisting of rice wax, carnauba wax, and sucrose fatty acid ester. [7] The weight of the fatty acid ester on one side of the sheet is 3 g / m 2 The sheet according to any one of [1] to [6] above. [8] The sheet according to any one of [1] to [7], wherein the fibrous base material is paper. [9] The sheet according to any one of [1] to [8], which does not contain liquid paraffin. [9] A method for manufacturing a sheet, comprising the steps of: (1) a step of applying an emulsion in which an oil phase containing a fatty acid ester is dispersed in an aqueous phase to a fibrous substrate; (2) exposing the fibrous substrate to which the emulsion has been applied to a temperature equal to or higher than the softening point of the oil phase.

[11] The method according to

[10] , wherein the softening point of the oil phase is 25°C or higher.

[12] The method according to

[10] or

[11] , wherein the softening point of the oil phase is 150°C or lower.

[13] The method according to any one of

[10] to

[12] , wherein the fatty acid ester is at least one selected from the group consisting of rice wax, carnauba wax, and sucrose fatty acid esters.

[14] The method according to any one of

[10] to

[12] , wherein the fibrous base material is paper. Effect of the Invention

[0007] According to the present invention, there is provided a sheet which has excellent oil resistance and low air resistance. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view of a sheet according to the present embodiment. [Diagram 2] FIG. 2 is an SEM photograph of the surface of the sheet obtained in Experimental Example Z1. [Diagram 3] FIG. 3 is an SEM photograph of the surface of the sheet obtained in Experimental Example A1. [Figure 4] FIG. 4 is an SEM photograph of the surface of the sheet obtained in Experimental Example A2. [Diagram 5] FIG. 5 is an SEM photograph of the surface of the sheet obtained in Experimental Example A3. [Figure 6] FIG. 6 is an SEM photograph of the surface of the sheet obtained in Experimental Example A4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A sheet according to one embodiment of the present invention includes a fibrous base material having fibers, and a fatty acid ester impregnated into the fibers of the fibrous base material.

[0010] (fibrous base material) A fibrous substrate is an aggregate of fibers. Examples of fibrous substrates are paper, nonwoven fabrics, and woven fabrics.

[0011] The paper is a sheet whose main component is vegetable pulp (fiber), and may be, for example, fine paper, pure white roll paper, kraft paper, Japanese paper, or paperboard. The vegetable pulp (fiber) may be wood pulp such as N-wood or L-wood, or non-wood pulp such as kenaf pulp or bagasse pulp. The paper may contain fibers other than vegetable pulp, such as rayon paper. In this specification, the term "main component" means that it accounts for 50% by mass or more.

[0012] The paper may contain optional additives such as strength agents, sizing agents, fillers, etc., as required.

[0013] Examples of wet strength agents include urea formaldehyde resins, melamine formaldehyde resins, polyamide polyamine epichlorohydrin (PAE), polyvinylamine (PVAm), etc. Examples of dry strength agents include cationic starch and cationic or amphoteric polyacrylamide copolymers.

[0014] Examples of the sizing agent include rosin-based sizing agents, alkyl ketene dimers, and alkenyl succinic anhydrides.

[0015] Examples of fillers are clay, kaolin, talc, calcium carbonate, titanium dioxide, silica.

[0016] Examples of the flame retardant include nitrogen compounds such as urea and ammonium compounds, hydroxides (preferably hydrates) such as magnesium hydroxide and aluminum hydroxide, and flame retardants containing phosphorus or halogen elements that have self-extinguishing properties. Among them, compounds containing water of crystallization such as magnesium hydroxide can be made flame retardant by the heat of vaporization of the water of crystallization during combustion and decomposition.

[0017] The nonwoven fabric is a sheet mainly composed of fibers other than vegetable pulp, and may be a wet nonwoven fabric such as a papermaking type, or a dry nonwoven fabric such as an adhesive type, a mechanically bonded type (needle punch, stitch bond), a spunbond type, etc. Specific examples of the nonwoven fabric include inorganic nonwoven fabrics such as glass nonwoven fabric and asbestos nonwoven fabric, and synthetic fiber nonwoven fabrics such as polyester nonwoven fabrics such as PET, polycarbonate nonwoven fabric, and polyolefin nonwoven fabric.

[0018] Examples of woven fabrics include cotton cloth, jersey, broadcloth, and the like.

[0019] The thickness of the fibrous base material is not particularly limited and can be appropriately set depending on the application. The basis weight of the fibrous base material is, for example, 30 g / m 2 or more, and 2 The basis weight of the fibrous base material may be, for example, 250 g / m 2 or less, and 2 It may be the following.

[0020] There is no particular limitation on the diameter of the fibers constituting the fibrous base material.

[0021] The fibrous base material has pores within each fiber that can hold an impregnating material, such as a fatty acid ester, within the pores.

[0022] (Fatty acid ester) A fatty acid ester is an ester of a fatty acid and an organic compound having a hydroxyl group. The carboxyl group of the fatty acid and the hydroxyl group of the organic compound having a hydroxyl group undergo dehydration condensation to form an ester bond. The fatty acid ester may be a single compound or a mixture of two or more compounds.

[0023] The number of carbon atoms in the fatty acid may be 10 or more, 12 or more, and 24 or less. The fatty acid may be a saturated fatty acid or an unsaturated fatty acid, and may be a straight chain or a branched chain.

[0024] An example of an organic compound having a hydroxyl group is an alcohol, which may be a monohydric alcohol such as an aliphatic alcohol, or a polyhydric alcohol such as glycerol. The number of carbon atoms in the aliphatic alcohol may be 8 or more, 10 or more, 20 or more, or 34 or less.

[0025] The organic compound having a hydroxyl group may be a sugar, an example of which is sucrose.

[0026] The fatty acid ester is preferably a wax ester. A wax ester is an ester of a saturated fatty acid having 10 or more carbon atoms and an aliphatic alcohol having 8 or more carbon atoms. Examples of wax esters include vegetable waxes such as rice wax and carnauba wax, and animal waxes such as beeswax and spermaceti.

[0027] The fatty acid ester may be an ester of sugar and fatty acid. An example of such an ester is sucrose fatty acid ester. Specific examples of sucrose fatty acid ester include sucrose dioleate, sucrose distearate, sucrose dipalmitate, sucrose dimyristate, sucrose dilaurate, sucrose monooleate, sucrose monostearate, sucrose monopalmitate, sucrose monomyristate, and sucrose monolaurate, and these may be used alone or in combination of two or more.

[0028] Particularly suitable fatty acid esters are rice wax, carnauba wax, and sucrose fatty acid esters, or any combination thereof.

[0029] (Softening point of fatty acid ester) The softening point of the fatty acid ester is preferably 25° C. or higher, and may be 30° C. or higher, 40° C. or higher, 50° C. or higher, 60° C. or higher, or 70° C. or higher. The softening point of the fatty acid ester may be 150° C. or lower. When the softening point of the fatty acid ester is 25° C. or higher, leakage of the fatty acid ester from the fibers during use is suppressed.

[0030] The softening point of the fatty acid ester can be measured based on JIS K 2207: 1996. When the fatty acid ester is a pure substance, the softening point and the melting point are equivalent values.

[0031] The amount of fatty acid ester per side of the sheet is 3g / m 2 may be 5 g / m or more, 2 It may be more than that.

[0032] The fibers may be impregnated with a component other than the fatty acid ester, an example of which is paraffin wax.

[0033] The fibers are preferably not impregnated with liquid paraffin, and the sheets are preferably not impregnated with liquid paraffin.

[0034] (structure) 1 is a schematic diagram of a cross section of a sheet 100 according to one embodiment. The sheet 100 includes a fibrous base material 10 composed of a large number of fibers 10a, and a fatty acid ester 20 impregnated in the fibers 10a.

[0035] The fatty acid ester 20 may be exposed on the surface of the fiber 10a, but it is preferable that the fatty acid ester 20 does not completely fill the spaces between the fibers 10a, and that gaps V through which gases, etc. can flow are maintained between the fibers 10a. The fatty acid ester 20 may be impregnated into each fiber throughout the entire thickness of the fibrous base material 10, but if the fatty acid ester 20 is impregnated into the fibers on either one of the surfaces in the thickness direction of the fibrous base material 10, the oil resistance of that surface can be improved. It is preferable that the fatty acid ester 20 does not form a film on the fibrous base material 10 so as to cover the entire fibrous base material 10 .

[0036] The air permeability resistance of the sheet 100 based on JIS P8117:2009 is preferably 58 s / 100 mL or less, may be 40 s / 100 mL or less, 30 s / 100 mL or less, 20 s / 100 mL or less, or may be 10 s / 100 mL or less.

[0037] (action) According to the sheet of this embodiment, the fibers of the fibrous base material are impregnated with fatty acid ester. Since the material impregnated into the fibers is fatty acid ester, the fibers are easily repelled, and therefore oil is less likely to penetrate into the fibers and gaps between the fibers in the sheet. In addition, since the fatty acid ester is impregnated into the fibers, not between the fibers, high breathability can be maintained. Since the softening point of the fatty acid ester is 25°C or higher, leakage of the fatty acid ester from the fibers during use is suppressed. Such sheets can be used as food packaging materials.

[0038] (Sheet manufacturing method) A method for producing a sheet according to one embodiment includes the steps of: (1) a step of applying an emulsion in which an oil phase containing a fatty acid ester is dispersed in an aqueous phase to a fibrous substrate; (2) exposing the fibrous base material coated with the emulsion to a temperature equal to or higher than the softening point of the oil phase.

[0039] Emulsions in which an oil phase containing a fatty acid ester is dispersed in an aqueous phase are commercially available as wax emulsions, for example, examples of which include rice wax emulsion and carnauba wax emulsion.

[0040] Alternatively, the above emulsion can be obtained by adding an oil phase component containing a fatty acid ester to water, further adding a surfactant as necessary, and stirring the mixture with a known stirrer. During stirring, heating and even reflux may be performed as necessary. The proportion of the fatty acid ester in the oil phase may be 50% by mass or more, 70% by mass or more, or 80% by mass or more.

[0041] There is no limitation on the surfactant, and for example, morpholine, acrylic acid amide-sodium acrylate copolymer, etc. can be used.

[0042] There is no limitation on the method for applying the obtained emulsion to the fibrous substrate, and a bar coater, spray coater, gravure coater, curtain coater, etc. can be used.

[0043] The coated fibrous substrate is exposed to a temperature equal to or higher than the softening point of the oil phase to remove water from the coating and soften, preferably melt, the oil phase components, particularly the fatty acid ester, to impregnate the pores of the fiber. In order to sufficiently impregnate the fatty acid ester into the pores of the fiber, it is preferable to expose the substrate to a temperature 5°C or higher, 10°C or higher, or 20°C or higher than the softening point. The time for exposure to the temperature is not limited, but can be, for example, 1 minute to 2 hours.

[0044] Means for exposing the fibrous base material to a temperature equal to or higher than the softening point include a hot air dryer and an infrared heater.

[0045] Usually, the water in the emulsion is also removed prior to exposure to temperatures above the softening point.

[0046] (action) According to the present embodiment, after the emulsion containing the oil phase containing the fatty acid ester is applied, the fibrous substrate is exposed to a temperature equal to or higher than the softening point, so that the fatty acid ester can be impregnated into the fibers of the fibrous substrate, and therefore the above-mentioned sheet can be suitably produced. EXAMPLES

[0047] (Preparation of fatty acid ester emulsion A) Ion-exchanged water and a surfactant (morpholine) were added and dissolved in a flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet tube, to prepare an emulsifier aqueous solution. The atmosphere in the flask was then replaced with nitrogen, and rice wax was added. The flask was then immersed in a water bath and heated while stirring with a stirring blade. This resulted in the preparation of fatty acid ester emulsion A. The weight ratio of rice wax, emulsifier, and water was 40:4:56. After drying the emulsion, the softening point of the oil phase was measured and found to be 87°C.

[0048] (Preparation of fatty acid ester emulsion B) Fatty acid ester emulsion B was prepared in the same manner as fatty acid ester emulsion A, except that paraffin wax was added in addition to paraffin wax. The weight ratio of rice wax (softening point 87°C), paraffin wax, emulsifier, and water was 25:15:4:56. The softening point of the oil phase after drying of the emulsion was measured and found to be 70°C.

[0049] (Preparation of fatty acid ester emulsion C) Fatty acid ester emulsion C was prepared in the same manner as fatty acid ester emulsion A, except that carnauba wax was used instead of rice wax. The weight ratio of carnauba wax, emulsifier, and water was 30:5:65. The softening point of the oil phase after drying of the emulsion was measured and found to be 90°C.

[0050] (Preparation of fatty acid ester emulsion E) Fatty acid ester emulsion E was prepared in the same manner as emulsion C, except that sucrose fatty acid ester (specifically, sucrose stearate: Ryoto Sugar Ester S-270, Mitsubishi Chemical Corporation) was used instead of rice wax. The weight ratio of sucrose fatty acid ester, emulsifier, and water was 2:2:7. The softening point of the oil phase after drying of the emulsion was measured and found to be 61°C.

[0051] (Experimental Examples A1 to A4) Pure white roll paper (made by Nippon Paper Industries, basis weight 45g / m 2 ) was prepared and fatty acid ester emulsion A was applied once to one side of pure white roll paper using a bar coater No. 8. The coating amount was 7.3 g / m2 as the basis weight of the oil phase (solid). 2 The drying temperatures after coating were room temperature (25° C.), 60° C., 90° C., and 120° C. in the order of Experimental Examples A1 to A4. The drying time was 24 hours in Experimental Example A1, and 0.5 hours in Experimental Examples A2 to A4.

[0052] (Experimental Examples B1 to B4) Pure white roll paper (made by Nippon Paper Industries, basis weight 45g / m 2 ) was prepared, and fatty acid ester emulsion B was applied once to one side of pure white roll paper using a bar coater No. 8. The coating amount was 7.6 g / m2 in terms of the basis weight of the oil phase (solid). 2 The drying temperatures after coating were room temperature (25° C.), 60° C., 90° C., and 120° C. in the order of Experimental Examples B1 to B4. The drying time was 24 hours in Experimental Example B1, and 0.5 hours in Experimental Examples B2 to B4.

[0053] (Experimental Examples C1 to C4) Pure white roll paper (made by Nippon Paper Industries, basis weight 45g / m2 ) was prepared and fatty acid ester emulsion C was applied once to one side of pure white roll paper using a bar coater No. 8. The coating amount was 6.4 g / m2 as the basis weight of the oil phase (solid). 2 The drying temperatures after coating were room temperature (25° C.), 60° C., 90° C., and 120° C. in the order of Experimental Examples C1 to C4. The drying time was 24 hours in Experimental Example C1, and 0.5 hours in Experimental Examples C2 to C4.

[0054] (Experimental Examples E1~E2) Pure white roll paper (made by Nippon Paper Industries, basis weight 45g / m 2 ) was prepared and fatty acid ester emulsion E was applied once to one side of pure white roll paper using a bar coater No. 8. The coating amount was 5.7 g / m2 as the basis weight of the oil phase (solid). 2 The drying temperatures after coating were room temperature (25° C.) and 90° C. in the order of Experimental Examples E1 to E4. The drying time was 24 hours for Experimental Example E1 and 0.5 hours for Experimental Example E2.

[0055] (Experimental Example Z1) Pure white roll paper (made by Nippon Paper Industries, basis weight 45g / m 2 ) was prepared and the oil resistance, etc. were evaluated without coating the emulsion or drying it.

[0056] (evaluation) (Oil resistance test 1 (kit method)) The oil resistance of the sheet was evaluated using JAPAN TAPPI Paper and Pulp Test Method No. 41 (Paper and Paperboard - Oil Repellency Test Method - Kit Method). Specifically, the test liquid with each kit number shown in Table 1 was dropped onto the surface of the sheet, and after 15 seconds, the presence or absence of penetration into the sheet was judged visually. The highest kit number that did not penetrate was taken as the oil resistance value. The higher the kit method value, the better the oil resistance.

[0057] [Table 1]

[0058] (Salad oil resistance test A (room temperature)) Room temperature salad oil (AJINOMOTO smooth canola oil) was dropped onto the surface of the sheet, and after 24 hours at room temperature, the sheet was visually inspected for permeation. If the oil permeated within 24 hours, the time it took to permeate was recorded.

[0059] (Salad oil resistance test B) Salad oil (AJINOMOTO smooth canola oil) heated to 160°C in an oven is dropped onto the surface of the sheet, and after 5 minutes at room temperature, the presence or absence of penetration into the treated paper is visually determined.

[0060] Air resistance The air resistance of the sheet was measured in accordance with JISP8117 using a Gurley-type densometer (air hole diameter 28.6±0.1 mm).

[0061] The results are shown in Table 2. Figures 2 to 6 show SEM photographs of the surfaces of the sheets obtained in Experimental Example Z1 and Experimental Examples A1 to A4, respectively. [Table 2]

[0062] In Experimental Examples A1 and A2, no improvement in oil resistance was observed compared to Experimental Example Z1. In Experimental Example A2, air resistance was significantly increased compared to Experimental Example Z1. As can be seen from the SEM images of Figures 3 and 4, in Experimental Examples A1 and A2, the rice wax and paraffin wax, which are the oil phase of the emulsion, formed a film on the paper that covered the entire surface of the paper. In Experimental Examples A3 and A4, the oil resistance was significantly improved, and the air resistance was not so high, compared to Experimental Example Z1. As can be seen from the SEM photographs in Figures 5 and 6, a film was not formed that covered the entire surface of the paper, and the rice wax, which is the oil phase of the emulsion, was impregnated into the fibers, and the gaps between the fibers were maintained.

[0063] In Experimental Examples B1 and B2, there was almost no improvement in oil resistance compared to Experimental Example Z1. In Experimental Examples B3 and B4, there was a significant improvement in oil resistance compared to Experimental Example Z1, and the air resistance did not increase significantly. In Examples B3 and B4, a film was not formed that covered the entire surface of the paper, and the rice wax, which is the oil phase of the emulsion, was impregnated into the fibers, maintaining the gaps between the fibers.

[0064] In Experimental Example C1, no improvement in oil resistance was observed compared to Experimental Example Z1, but air resistance increased significantly. In Experimental Example C2, oil resistance was significantly improved compared to Experimental Example Z1, but air resistance increased significantly. In Experimental Examples C3 and C4, oil resistance was significantly improved compared to Experimental Example Z1, but air resistance did not increase significantly. In Examples C3 and C4, a film covering the entire surface of the paper was not formed, and the rice wax, which is the oil phase of the emulsion, was impregnated into the fibers, maintaining gaps between the fibers.

[0065] In Experimental Examples D1 and D2, oil resistance was improved compared to Experimental Example Z1, but air resistance increased significantly. In Experimental Examples D3 and D4, oil resistance was greatly improved compared to Experimental Example Z1, but air resistance did not increase significantly. In Examples D3 and D4, a film covering the entire surface of the paper was not formed, and the rice wax, which is the oil phase of the emulsion, was impregnated into the fibers, maintaining gaps between the fibers.

[0066] In Example E1, oil resistance was improved compared to Example Z1, but air resistance increased significantly. In Example E2, oil resistance was greatly improved compared to Example Z1, but air resistance did not increase significantly. In Example E2, a film was not formed that covered the entire surface of the paper, and the rice wax, which is the oil phase of the emulsion, was impregnated into the fibers, maintaining gaps between the fibers.

[0067] As described above, it was confirmed that experimental examples A3, A4, B3, B4, C3, C4, D3, and D4 achieved low air resistance and high oil resistance. [Explanation of symbols]

[0068] 10...fibrous base material, 10a...fiber, 20...fatty acid ester, 100...sheet, V...gap.

Claims

1. A sheet comprising: a fibrous base material having fibers; and a fatty acid ester impregnated into the fibers of the fibrous base material.

2. The sheet according to claim 1 , wherein the fatty acid ester has a softening point of 25° C. or higher.

3. 3. The sheet according to claim 1, wherein the fatty acid ester has a softening point of 150°C or lower.

4. The sheet according to claim 1 or 2, wherein gaps are maintained between the fibers of the fibrous base material.

5. The sheet according to claim 1 or 2, wherein the sheet has an air resistance based on JIS P8117:2009 of 58 s / 100 mL or less.

6. The sheet according to claim 1 or 2, wherein the fatty acid ester is at least one selected from the group consisting of rice wax, carnauba wax, and sucrose fatty acid ester.

7. The weight of the fatty acid ester on one side of the sheet is 3 g / m ２ The sheet according to claim 1 or 2.

8. 3. The sheet of claim 1 or 2, wherein the fibrous substrate is paper.

9. 3. The sheet according to claim 1 or 2, which does not contain liquid paraffin.

10. A method for manufacturing a sheet, comprising the steps of: (1) applying an emulsion in which an oil phase containing a fatty acid ester is dispersed in an aqueous phase to a fibrous substrate; (2) exposing the fibrous substrate to which the emulsion has been applied to a temperature equal to or higher than the softening point of the oil phase.

11. The method according to claim 10, wherein the softening point of the oil phase is 25°C or higher.

12. 12. The method according to claim 10 or 11, wherein the softening point of the oil phase is below 150°C.

13. 12. The method according to claim 10 or 11, wherein the fatty acid ester is at least one selected from the group consisting of rice wax, carnauba wax, and sucrose fatty acid ester.

14. 12. The method of claim 10 or 11, wherein the fibrous substrate is paper.

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