Absorbent paper for fruits and vegetables and its manufacturing method

Abstract

To provide absorbent paper for fruits and vegetables that absorbs moisture appropriately and also functions as a cushioning material. [Solution] The fiber used contains 70% or more by mass of naturally derived pulp relative to the total amount of fiber components used, and has a density of 0.75 g / m³. 2 The following is a type of absorbent paper for fruits and vegetables, characterized by a Clem water absorption rate of 40-160 mm.

Description

[Technical Field] 【0001】 This disclosure relates to absorbent paper for fruits and vegetables. More specifically, it relates to absorbent paper for fruits and vegetables that absorbs moisture appropriately and also functions as a cushioning material. [Background technology] 【0002】 Absorbent paper for fruits and vegetables is used as a backing for food products, absorbing moisture released from the food and ingredients. Required performance characteristics for absorbent paper for fruits and vegetables include water absorption capacity, water retention capacity, water absorption speed, ease of release from food, safety, hygiene, processability, and cushioning properties, and a balance of these is important. For example, while water absorption capacity is necessary, if the water absorption capacity is too high, it will absorb too much moisture from the fruits and vegetables, causing the humidity inside the box to become too low and potentially damaging the produce. On the other hand, if the water absorption capacity is too low and does not absorb moisture sufficiently, it will not be able to prevent moisture from seeping out of the produce, and may cause condensation during refrigeration during transport or storage, potentially reducing the product's value. Regarding cushioning, if it is too soft, it may deform or even tear under the weight of the produce, but if it is too hard, it may not function adequately as a cushioning material, or it may not tear even when wet, leading to problems. 【0003】 Various types of absorbent sheets and absorbent papers have been investigated for maintaining the freshness of such fruits and vegetables. For example, methods have been proposed to improve freshness preservation by limiting basis weight, smoothness, and water absorption (see, for example, Patent Document 1). In addition, it has been proposed to improve the freshness preservation function of absorbent paper by limiting basis weight, specific volume, softwood kraft pulp, wet tensile strength, etc., and by applying crepe-like properties (see, for example, Patent Documents 2-4). [Prior art documents] [Patent Documents] 【0004】 [Patent Document 1] Japanese Patent Application Publication No. 9-77603 [Patent Document 2] Japanese Patent Publication No. 2018-48425 [Patent Document 3] Japanese Patent Publication No. 2019-65417 [Patent Document 4] Japanese Patent Publication No. 2019-173193 [Overview of the Initiative] [Problems that the invention aims to solve] 【0005】 However, the absorbent papers disclosed in Patent Documents 1 to 4 do not address the balance between the amount of water absorbed and the absorption speed, nor their role as a cushioning material. Furthermore, the specific volume shown in these documents is insufficient for their effectiveness as a cushioning material. 【0006】 This disclosure also aims to provide absorbent paper for fruits and vegetables that absorbs moisture to a moderate degree and also functions as a cushioning material. 【0007】 Other purposes and effects of this disclosure will be readily apparent to those skilled in the art by referring to the following description. [Means for solving the problem] 【0008】 To solve the above problems, the present inventors have developed a material in which natural pulp accounts for 70% or more by mass of the total amount of fiber components used, and has a density of 0.75 g / m³. 2 The present invention was completed by finding that by using a fruit and vegetable absorbent paper with a Klem water absorption degree of 40-160 mm, it can absorb moisture appropriately and also function as a cushioning material. Specifically, the fruit and vegetable absorbent paper according to the present invention contains 70% or more by mass of naturally derived pulp relative to the total amount of fiber components used, and has a density of 0.75 g / m². 2 The following characteristics are that the Klem water absorption value is 40 to 160 mm. With this configuration, the Klem water absorption value is within an appropriate range, so it does not absorb too much moisture, and the density is within an appropriate range, so it functions as a cushioning material for fruits and vegetables. The Klem water absorption value here was measured according to JIS P8141:04 Paper and cardboard - Water absorption test method - Klem method. 【0009】 In the fresh produce blotting paper according to the present invention, it is preferable that the freeness of the fiber component is 500 to 800 ml of CSF. By adopting such a configuration, it does not absorb too much moisture and can also function as a cushioning material. 【0010】 The fresh produce blotting paper according to the present invention preferably has a thickness of 0.15 mm or more. By adopting such a configuration, it functions more preferably as a cushioning material, and even if it absorbs a small amount of moisture, it is difficult to break. 【0011】 The fresh produce blotting paper according to the present invention contains synthetic fibers, and it is preferable that the synthetic fibers are contained in an amount of 1 to 20% by mass based on the total amount of the fiber components. By using pulp fibers and synthetic fibers in combination, the water absorbency is increased, and the absorption amount can be controlled by increasing or decreasing the synthetic fibers. 【0012】 The fresh produce blotting paper according to the present invention preferably contains a wet strength agent in an amount of 0.05 to 0.8 parts by mass based on the total amount of the fiber components. By adopting such a configuration, it is possible to prevent breakage even when absorbing a large amount of moisture. 【0013】 It is preferable that the fresh produce blotting paper according to the present invention does not contain a polymer absorbent. By adopting such a configuration, freshness can be maintained by releasing the absorbed moisture. 【0014】 The present invention can also be regarded as a method for manufacturing fresh produce blotting paper. The method for manufacturing fresh produce blotting paper according to the present invention includes a step of preparing a fiber component mainly composed of naturally derived pulp, a step of beating the fiber component to obtain a slurry of 500 to 800 ml of CSF, and a step of papermaking fresh produce blotting paper using the slurry, wherein the naturally derived pulp is contained in an amount of 70% by mass or more based on the total amount of the fiber components, and the density of the fresh produce blotting paper is 0.75 g / m 2 is as follows, and is characterized in that the Cram water absorbency is 40 to 160 mm. And according to such a configuration, it is possible to easily manufacture fresh produce blotting paper that moderately absorbs moisture and also functions as a cushioning material. 【Effects of the Invention】 【0015】 According to the present disclosure, it is possible to provide a fresh produce blotting paper that moderately absorbs moisture and also functions as a cushioning material. 【Brief Description of the Drawings】 【0016】 [Figure 1] It is a chart showing the configuration and physical properties of the fresh produce blotting paper according to the examples and comparative examples. 【Modes for Carrying Out the Invention】 【0017】 Next, embodiments of the present invention will be shown and described in detail, but the present invention is not construed as being limited to these descriptions. As long as the effects of the present invention are achieved, the embodiments may be variously modified. 【0018】 The absorbent paper for fruits and vegetables according to this embodiment uses fibrous components such as naturally derived pulp and synthetic fibers, with naturally derived pulp being the main component. Here, the main component refers to the component that is present in the largest quantity by mass among the components constituting the absorbent paper for fruits and vegetables. In this embodiment, it is preferable that the amount of naturally derived pulp among the fibrous components constituting the base paper be 70% by mass or more, and more preferably 90% by mass. There are no particular limitations on the raw material pulp used for the base paper, but wood pulp and non-wood pulp are preferred, and wood fibers can be used particularly suitably. Examples of wood pulp include chemical pulps such as bleached softwood kraft pulp (NBKP), unbleached softwood kraft pulp (NUKP), bleached hardwood kraft pulp (LBKP), and unbleached hardwood kraft pulp (LUKP), mechanical pulps such as crushed wood pulp (GP) and thermomechanical pulp (TMP), and recycled paper pulp such as deinked pulp. Examples of non-wood pulp include kenaf, bagasse, bamboo, and cotton. One or more types of these naturally derived pulps can be used. Among the raw material pulps, LBKP has a low lignin content, making it suitable for making absorbent paper for fruits and vegetables that is flexible and easily absorbs moisture. If the effects of LBKP are desired, for example, it is preferable to include 10 to 50% by mass of LBKP, more preferably 15 to 40% by mass, and even more preferably 20 to 30% by mass, relative to the total amount of fiber components used. Furthermore, NBKP has a longer fiber length than LBKP, making it an effective pulp for maintaining the strength of absorbent paper for fruits and vegetables, and it is even more flexible than LBKP, making it suitable for use as a base for boxes, etc., as its shape can be easily changed. If the effects of NBKP are desired, for example, it is preferable to include 20 to 90% by mass of NBKP, more preferably 40 to 80% by mass, and even more preferably 50 to 75% by mass, relative to the total amount of fiber components used. 【0019】 As synthetic fibers used in the base paper, PET fibers, nylon fibers, polyester fibers, acrylic fibers, etc., can be used. By using pulp and synthetic fibers in combination, the synthetic fibers can penetrate the gaps between the pulp fibers and moderately inhibit hydrogen bonding, thereby lowering the density of the absorbent paper for fruits and vegetables, and as a result, the water absorption rate of the absorbent paper for fruits and vegetables can be improved. As for the amount of these synthetic fibers to be blended, for example, when blending PET fibers, it is preferable to include 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 3 to 10% by mass, relative to the total amount of fiber components used. If the blending amount is less than 1% by mass, the effect of lowering the density is low, and if it exceeds 20% by mass, not only is the decrease in strength of the absorbent paper for fruits and vegetables significant, but the effect of lowering the density also plateaus and the efficiency decreases. 【0020】 The fiber components of the absorbent paper for fruits and vegetables according to this embodiment are prepared as a pulp slurry with an appropriate degree of beating using a disintegrator and a beating machine. In this invention, it is preferable to have a CSF of 500 to 800 ml according to the Canadian Standard for Filtration (JIS P 8121:1995 Method for Testing the Filtration of Pulp). More preferably, it is CSF 550 to 750 ml, and even more preferably CSF 600 to 700 ml. If the CSF is less than 500 ml, the density may be too high, impairing the cushioning properties, and the voids will also be small, which may prevent the desired Clem water absorption from being achieved. On the other hand, if the CSF exceeds 800 ml, the density may be too low, causing fruits and vegetables to sink too deeply, damaging them or causing them to absorb too much moisture, and the strength of the absorbent paper for fruits and vegetables will also be low, making it prone to tearing. 【0021】 The absorbent paper for fruits and vegetables according to this embodiment is formed by using a pulp slurry adjusted to an appropriate degree of beating as the raw material slurry and making paper in a paper machine. Any known paper machine can be used. That is, it can be made using a wire mesh paper machine, a cylinder mesh paper machine, a hybrid former, a gap former, etc. The absorbent paper for fruits and vegetables may be a single layer or a multilayer of two or more layers, but if the thickness of the absorbent paper for fruits and vegetables is 300 μm or more, multilayer making is preferred. This suppresses unevenness and allows for more uniform support of fruits and vegetables. For example, if the thickness is 300 μm or more, it can be made of four layers. 【0022】 The density of the absorbent paper for fruits and vegetables according to this embodiment is 0.75 g / cm³. 2 The following is preferred: Preferably 0.70 g / cm³. 2 The following, and more preferably 0.65 g / cm³ 2 The following is the result: 0.75 g / cm³ 2 If the amount exceeds 0.30 g / cm³, it may harden and its function as a cushioning material may decrease. 2 If the density is less than this, depending on the thickness, the produce may sink too much and not function as a cushioning material, potentially damaging the produce. The density can be adjusted by controlling the degree of beating of the pulp slurry, the type and proportion of synthetic fibers, the addition of bulking agents, etc. 【0023】 The absorbent paper for fruits and vegetables according to this embodiment has a crem water absorption degree of 40 to 160 mm. Preferably, it is 60 to 140 mm, and more preferably 70 to 120 mm. If the crem water absorption degree is less than 40 mm, the removal of moisture from fruits and vegetables is slow, and as a result of not being able to absorb moisture sufficiently, the commercial value of the fruits and vegetables is impaired. On the other hand, if the crem water absorption degree exceeds 160 mm, it absorbs too much moisture, causing the fruits and vegetables to wilt or get damaged. By providing an appropriate level of moisture absorption, fruits and vegetables can be kept fresh. The crem water absorption degree has an inverse relationship with density and can be adjusted in almost the same way as density. Specifically, the crem water absorption degree can be adjusted by adjusting the degree of beating of the pulp slurry, adjusting the press pressure on the paper machine, adjusting the type and blending ratio of synthetic fibers, and adjusting the calender pressure conditions. 【0024】 The thickness of the absorbent paper for fruits and vegetables according to this embodiment is preferably 0.15 mm or more, more preferably 0.20 mm or more, and most preferably 0.50 mm or more. If the thickness is less than 0.15 mm, the cushioning function will be reduced, and the strength of the absorbent paper may decrease. There is no particular upper limit, but if the thickness increases too much, it becomes difficult to bend and difficult to fold as bottom paper, so the practical upper limit is about 2 mm. 【0025】 The absorbent paper for fruits and vegetables according to this embodiment preferably contains a wet-strength agent. By adding a wet-strength agent, tearing and other damage do not occur even under water absorption, and the dimensions do not change easily. Preferred wet-strength agents used here are polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, and melamine resin. The amount of wet-strength agent added is preferably 0.05 to 0.8 parts by mass, more preferably 0.1 to 0.5 parts by mass, per 100 parts by mass of fiber components. In addition, other papermaking additives such as internal sizing agents, fillers, yield improvers, dyes, aluminum sulfate, and bulking agents can be used within a range that does not impair the effects of the present invention. However, from the viewpoint of water absorption, the amount of internal sizing agent is preferably 0.1 parts by mass or less per 100 parts by mass of fiber components, the amount of filler is preferably 1 part by mass or less per 100 parts by mass of fiber components, and from the viewpoint of use with fruits and vegetables, the amount of dye is preferably 0.1 parts by mass or less per 100 parts by mass of fiber components, and it is more preferable that none of these be used. 【0026】 The absorbent paper for fruits and vegetables according to this embodiment may use a bulking agent as a means of reducing density. A polyoxyalkylene alkyl ether or a nonionic surfactant is preferred as the bulking agent. A higher alcohol is particularly preferred as the polyoxyalkylene alkyl ether. Examples of nonionic surfactants include oil-based nonionic surfactants, sugar alcohol-based nonionic surfactants, sugar-based nonionic surfactants, polyhydric alcohol-type nonionic surfactants, and other nonionic surfactants. Examples of such bulking agents include KB-85 and KB-130 (manufactured by Kao Corporation). Other bulking agents include fatty acid amides, hydroxyethyl derivatives of fatty acid amides, fatty acid polyamidoamine epichlorohydrin reaction products, and fatty acid polyamidoamines, but caution is required when using these as they exhibit sizing properties and inhibit water absorption. 【0027】 The absorbent paper for fruits and vegetables according to this embodiment preferably does not contain a superabsorbent polymer. Here, "superabsorbent polymer" refers to the so-called superabsorbent polymer (SAP) used in diapers and sanitary products. When a superabsorbent polymer is added to the raw material slurry, it absorbs water and swells up immediately, making its addition to absorbent paper for fruits and vegetables impractical. Examples of such superabsorbent polymers include sodium polyacrylate. 【0028】 The fruit and vegetable absorbent paper according to this embodiment is not limited in terms of the drying method for the base paper, and methods such as hot air drying, infrared drying, and drum drying can be used. On the paper machine, a cylinder dryer can be used alone or in combination with others for drying, and the drying temperature is preferably set appropriately in the range of 80 to 200°C, and more preferably in the range of 80 to 160°C. 【0029】 In this embodiment, it is preferable not to perform a smoothing treatment on the fruit and vegetable absorbent paper after drying, as this reduces the overall density of the paper. If a smoothing treatment is performed to an extent that does not affect the invention, a machine cander, soft calender, super calender, etc., can be used. 【0030】 For the surface sizing treatment of the fruit and vegetable blotting paper according to this embodiment, it is preferably not carried out because there is a risk that the pulp fibers on the surface will be exposed and the water absorption will be impaired. When performing surface sizing treatment to the extent that it does not affect the invention, pond methods such as size press, transfer methods such as gate roll coater and sizator can be used. It is preferable to use water-soluble polymers such as starch, polyvinyl alcohol, and polyacrylamide-based resins as the size liquid. 【Example】 【0031】 Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In addition, "parts" and "%" in the examples indicate "mass parts" and "mass%" respectively, unless otherwise specified. The number of added parts is the value in terms of solid content. 【0032】 <Example 1> 25 parts of LBKP, 68 parts of NBKP, and 7 parts of PET fiber were mixed and beaten to a pulp slurry with a Canadian Standard Freeness (CSF) of 640 ml, and 0.2 parts of sulfate band was added to obtain a raw material slurry. Using the obtained raw material slurry, a 4-layer wet paper consisting of 1 layer on the surface, 2 layers in the middle layer, and 1 layer on the back layer was combined and paper was made by a cylinder mold paper machine. Then, it was dewatered in the press part and dried to obtain a fruit and vegetable blotting paper. The basis weight of each layer was 175 g / m 2 for a total of 700 g / m 2 in total. 【0033】 <Example 2> A fruit and vegetable blotting paper was obtained in the same manner as in Example 1 except that the CSF of the pulp slurry was changed from 640 ml to 500 ml. 【0034】 <Example 3> A fruit and vegetable blotting paper was obtained in the same manner as in Example 1 except that the CSF of the pulp slurry was changed from 640 ml to 800 ml. 【0035】 <Example 4> Absorbent paper for fruits and vegetables was obtained in the same manner as in Example 1, except that the absorbent paper for fruits and vegetables obtained in Example 1 was subjected to a smoothing treatment. After the smoothing treatment, the density was 0.58 g / cm³. 3 From 0.75 g / cm³ 3 That's what happened. 【0036】 <Example 5> Absorbent paper for fruits and vegetables was obtained in the same manner as in Example 1, except that 0.3 parts of a wet paper strength agent (product name: WS-4021 / manufactured by Seikou PMC Co., Ltd.) was added to the pulp slurry. 【0037】 <Example 6> 0.3 parts of a wet paper strength agent (product name: WS-4021 / manufactured by Seikoh PMC) were added to the pulp slurry, and the basis weight of each of the four layers was 175 g / m². 2 Total 700g / m 2 All four layers are 105g / m² 2 Total 420g / m 2 Absorbent paper for fruits and vegetables was obtained in the same manner as in Example 1, except that the above was not applicable. 【0038】 <Example 7> 0.3 parts of a wet paper strength agent (product name: WS-4021 / manufactured by Seikoh PMC) were added to the pulp slurry, and the basis weight of each of the four layers was 175 g / m². 2 Total 700g / m 2 The paper is made in three layers, with each layer weighing 40g / m². 2 Total 120g / m 2 Absorbent paper for fruits and vegetables was obtained in the same manner as in Example 1, except that the above was not applicable. 【0039】 <Example 8> Absorbent paper for fruits and vegetables was obtained in the same manner as in Example 1, except that the raw material composition was changed from LBKP 25 parts, NBKP 68 parts, PET fiber 7 parts to LBKP 25 parts, NBKP 75 parts, PET fiber 0 parts, and 0.3 parts of a wet paper strength agent (product name: WS-4021 / manufactured by Seikoh PMC Co., Ltd.) was added to the pulp slurry. 【0040】 <Comparative Example 1> A water-absorbing paper for fruits and vegetables was obtained in the same manner as in Example 1, except that the CSF was changed from 640 ml to 450 ml. 【0041】 <Comparative Example 2> 160g / m² from 4-ply papermaking 2 A single layer was formed, then water was squeezed in a press and dried to obtain a base paper for absorbent paper for fruits and vegetables. Four sheets of this paper were stacked, and 20 g / m² of polymer absorbent resin (SG-N21, manufactured by Sanyo Chemical Industries, Ltd.) was added between the layers. 2 The material was added and layered to obtain absorbent paper for fruits and vegetables. 【0042】 <Comparative Example 3> The density was reduced to 0.60 g / cm³ through a smoothing process. 3 From 0.85 g / cm³ 3 A water-absorbing paper for fruits and vegetables was obtained in the same manner as in Example 1, except that it was changed to [the specified value]. 【0043】 <Comparative Example 4> A comparison was conducted using commercially available high-quality paper-based wrapping paper. 【0044】 <Comparative Example 5> We conducted the comparison using commercially available cardboard boxes. 【0045】 <Freeness measurement method> The measurement was performed according to JIS P8121-2:12 Pulp - Methods for testing filtration efficiency - Part 2, Canadian standard filtration efficiency method. 【0046】 <Density measurement method> The measurements were taken according to JIS P8118:14 Paper and cardboard - Test methods for thickness, density and specific volume. 【0047】 <Water absorption measurement method> The water absorption test was performed according to JIS P8141:04 Paper and cardboard - Water absorption test method - Klem method. The immersion time was 10 minutes ± 10 seconds, and the average value of the Klem water absorption in the longitudinal and transverse directions was used. 【0048】 <Method for measuring specific tensile strength> The tensile strength was measured according to JIS P8135:98 Paper and cardboard - Wet tensile strength test method. 【0049】 <Method for measuring specific wet tensile strength> The specific wet tensile strength was determined by dividing the value measured according to JIS P8135:98 Paper and cardboard - Wet tensile strength test method by the basis weight. Comparative Example 2 was deemed unmeasurable because delamination occurred when immersed in water. 【0050】 Figure 1 shows the composition and physical properties of the absorbent papers for fruits and vegetables obtained in each example and comparative example. As shown in Figure 1, the absorbent papers for fruits and vegetables obtained in Examples 1 to 8 had an appropriate water absorption rate and high cushioning effect, and were at a level that posed no practical problems. In contrast, the absorbent paper for fruits and vegetables obtained in Comparative Example 1 had a slow water absorption rate and low density, resulting in low cushioning properties and making it easy to damage fruits and vegetables. The absorbent paper for fruits and vegetables obtained in Comparative Example 2 used a superabsorbent polymer used in diapers, etc., between the layers, resulting in a water absorption rate faster than the desirable range, which easily removed excess moisture from fruits and vegetables and made it easy to damage them. In addition, because it is a superabsorbent polymer, it cannot be incorporated on a paper machine that uses water. Therefore, a superabsorbent polymer was added between the layers, but when measuring the specific wet tensile strength, interlayer delamination occurred when immersed in water, making measurement impossible. Interlayer delamination also occurred during actual use, making it easy to tear. The absorbent paper for fruits and vegetables obtained in Comparative Example 3 had a high density due to the smoothing treatment, resulting in a slow water absorption rate and poor cushioning properties, making it easy to damage fruits and vegetables. Comparative Example 4 uses high-quality packaging paper, but its poor water absorption and high density resulted in poor cushioning, causing damage to the produce. Comparative Example 5 uses corrugated cardboard, but its poor water absorption made it unsuitable for practical use.

Claims

[Claim 1] The total amount of fiber components used contains 70% or more of naturally derived pulp, and the density is 0.75 g / m³. 2 The following is a type of absorbent paper for fruits and vegetables characterized by a water absorption rate of 40 to 160 mm. [Claim 2] The absorbent paper for fruits and vegetables according to claim 1, characterized in that the freeness of the fiber component is CSF 500 to 800 ml. [Claim 3] The absorbent paper for fruits and vegetables according to claim 1 or 2, characterized in that it has a thickness of 0.15 mm or more. [Claim 4] The absorbent paper for fruits and vegetables according to claim 1 or 2, characterized in that the fiber component includes synthetic fibers in addition to pulp, and the synthetic fibers are present in an amount of 1 to 20% by mass relative to the total amount of the fiber component. [Claim 5] The absorbent paper for fruits and vegetables according to claim 1 or 2, characterized in that it contains 0.05 to 0.80 parts by mass of a wet-strengthening agent relative to the total amount of fiber components. [Claim 6] The fruit and vegetable absorbent paper according to claim 1 or 2, characterized in that the fruit and vegetable absorbent paper does not contain a polymer absorbent. [Claim 7] The process involves preparing a fiber component primarily composed of naturally derived pulp, The steps include: beating the aforementioned fibrous components to obtain a slurry of 500-800 ml of CSF; The process includes the step of making absorbent paper for fruits and vegetables using the slurry, The aforementioned naturally derived pulp accounts for 70% or more by mass of the total fiber content, and the density of the absorbent paper for fruits and vegetables is 0.75 g / m². 2 The following is a method for manufacturing absorbent paper for fruits and vegetables, characterized in that the Klem water absorption degree is 40 to 160 mm.

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