Paper substrate and its manufacturing method

Abstract

To improve transparency of a paper substrate.SOLUTION: A paper substrate 1 includes an organic pigment 3 which can be melted by heating, and by heating the paper substrate 1 to a melting point of the organic pigment 3 or higher to melt the organic pigment 3, a gap between the pulp fibers 4 of the paper substrate 1 is buried with the organic pigment to improve its transparency. Also, by partially heating the paper substrate 1, the organic pigment 3 in a portion having been heated is melted, a gap between the pulp fibers 4 in the portion is buried with the organic pigment to improve its transparency.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a paper substrate and a method for producing the same. [Background technology]

[0002] In recent years, growing awareness of environmental protection has led to a shift from synthetic resin substrates to paper substrates. For example, in the case of window envelopes, the window portion is made of a translucent paper substrate such as glassine paper or tracing paper instead of a synthetic resin substrate such as cellophane, making them recyclable (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-29588 Summary of the Invention [Problem to be solved by the invention]

[0004] However, although translucent paper substrates such as glassine paper and tracing paper are recyclable, they have the drawback of being less transparent than synthetic resin substrates.

[0005] The present invention has been made in light of the above-mentioned circumstances, and has as its object to improve the transparency of paper substrates. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention is configured as follows.

[0007] (1) The paper base material according to the present invention contains an organic pigment that melts when heated.

[0008] The paper base material according to the present invention contains an organic pigment that melts when heated. By heating the paper base material and melting the organic pigment, the gaps between the pulp fibers in the paper base material can be filled with the organic pigment, thereby improving transparency.

[0009] Furthermore, by partially heating the paper base material, the organic pigment in the heated area is melted, filling the gaps between the pulp fibers in that area with the organic pigment, improving transparency. In other words, by selecting the area of ​​the paper base material to be heated, it is possible to arbitrarily select the area in which transparency is to be improved.

[0010] Furthermore, transparency can be improved by simply heating the paper substrate, and therefore transparency can be improved by heating the paper substrate when necessary.

[0011] (2) In a preferred embodiment of the present invention, at least a part of the organic pigment in the paper base is melt-solidified.

[0012] According to this embodiment, at least a portion of the paper base is heated to melt and solidify at least a portion of the organic pigment, so that the paper base has improved transparency at least in part.

[0013] (3) In another embodiment of the present invention, the paper base does not contain inorganic pigments.

[0014] According to this embodiment, the paper base does not contain inorganic pigments that reduce transparency, so transparency can be effectively improved by heating the organic pigments to melt and solidify them.

[0015] (4) In one embodiment of the present invention, the paper substrate is tracing paper or glassine paper.

[0016] According to this embodiment, the transparency of the paper substrate made of translucent tracing paper or glassine paper can be further improved.

[0017] (5) In another embodiment of the present invention, the organic pigment is in the form of particles, and the average particle size is 0.5 μm or more and less than 10 μm.

[0018] According to this embodiment, the average particle diameter of the particulate organic pigment is small, at 0.5 μm or more and less than 10 μm, so that, for example, a coating liquid containing the organic pigment can be smoothly penetrated and incorporated into the interior of the paper base material.

[0019] (6) The method for producing a paper substrate according to the present invention is a method for producing a paper substrate by coating or impregnating a base paper with a coating liquid, and the coating liquid contains an organic pigment that melts when heated.

[0020] According to the method for manufacturing a paper base material of the present invention, the paper base material is manufactured by coating or impregnating base paper with a coating liquid containing an organic pigment that melts when heated. By heating the paper base material and melting the organic pigment, the gaps between the pulp fibers of the paper base material are filled with the organic pigment, thereby improving transparency.

[0021] Furthermore, by partially heating the paper base material, the organic pigment in the heated area is melted, filling the gaps between the pulp fibers in that area with the organic pigment, improving transparency. In other words, by selecting the area of ​​the paper base material to be heated, it is possible to arbitrarily select the area in which transparency is to be improved.

[0022] Furthermore, transparency can be improved by simply heating the paper substrate, and therefore transparency can be improved by heating the paper substrate when necessary.

[0023] (7) In one embodiment of the present invention, the method further comprises a step of coating the coating liquid on at least one surface of the base paper.

[0024] According to this embodiment, the coating liquid is applied to at least one surface of the base paper, and the organic pigment can be allowed to penetrate into the interior of the base paper.

[0025] Furthermore, when the base paper is thick, the organic pigment can be made to penetrate into the inside of the base paper by applying the coating liquid to both sides of the base paper.

[0026] (8) In another embodiment of the present invention, the method further comprises a step of heating at least a portion of the base paper coated with the coating liquid to melt and solidify at least a portion of the organic pigment.

[0027] According to this embodiment, by heating at least a portion of the base paper that has been coated and penetrated with a coating liquid containing an organic pigment, the organic pigment inside the base paper is melted and the gaps between the pulp fibers are filled with the organic pigment, thereby obtaining a paper base material with at least a portion that is highly transparent. In this case, by selecting the portion to be heated, a paper base material with increased transparency in any portion can be obtained.

[0028] (9) In yet another embodiment of the present invention, the dry coating amount of the organic pigment per unit volume in the coating step is 37.21 kg / m 3 More than 111.63kg / m 3 The following is the result.

[0029] According to this embodiment, the dry coating amount of organic pigment per unit volume of base paper is 37.21 kg / m 3 Since the above value is obtained, the transparency can be effectively improved. 3 Since the organic pigment is contained in the paper substrate in a stable manner, the organic pigment can be contained in the paper substrate in a stable manner.

[0030] (10) In yet another embodiment of the present invention, the coating liquid is an aqueous coating liquid containing an emulsion of the organic pigment.

[0031] According to this embodiment, the organic pigment can be permeated into the interior of the base paper by coating or impregnating the base paper with a coating liquid in which the organic pigment is sufficiently dispersed.

[0032] (11) In another embodiment of the present invention, the base paper is tracing paper or glassine paper.

[0033] According to this embodiment, it is possible to obtain a paper base material having improved transparency compared to a base paper made of semi-transparent tracing paper or glassine paper. [Effects of the Invention]

[0034] According to the present invention, the organic pigment contained in the paper base material is heated and melted to fill the gaps between the pulp fibers of the paper base material, thereby improving transparency.

[0035] Furthermore, by selecting the portion of the paper substrate to be heated, it is possible to arbitrarily select the portion where the organic pigment is to be melted, that is, the portion where transparency is to be improved.

[0036] Furthermore, transparency can be improved by simply heating the paper substrate, and therefore transparency can be improved by heating the paper substrate when necessary. [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 is a schematic diagram showing the general configuration of a paper substrate according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram of a portion of the paper substrate of FIG. 1 after heating. DETAILED DESCRIPTION OF THE INVENTION

[0038] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0039] FIG. 1 is a schematic diagram showing the general configuration of a paper substrate according to one embodiment of the present invention.

[0040] The paper substrate 1 of this embodiment is made of base paper 2 containing an organic pigment 3 that melts when heated. To increase transparency, the base paper 2 is preferably paper that does not contain inorganic pigments and has short pulp fiber lengths, for example, pulp fiber lengths of 0.1 mm to 1.5 mm. This base paper 2 is preferably translucent paper such as tracing paper or glassine paper, and in this embodiment, the base paper 2 is tracing paper.

[0041] The paper substrate 1 of this embodiment can be produced by applying a coating liquid containing particulate organic pigment 3 to one side of base paper and allowing the organic pigment 3 to penetrate into the interior of the base paper 2.

[0042] Inside the base paper 2, there are gaps between the pulp fibers 4, and since the organic pigment 3 in this embodiment is white, the paper substrate 1 in FIG. 1 is white and opaque.

[0043] When heated above its melting point, the organic pigment 3 melts, and when cooled, it solidifies and retains its shape.

[0044] Examples of materials for the organic pigment 3 include thermoplastic resins such as polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylic acid ester, polyacrylonitrile, polybutadiene, and copolymers thereof. The particulate organic pigment 3 is preferably solid particles, but may also be hollow particles, or both may be used in combination.

[0045] The paper base material 1 of this embodiment contains an organic pigment 3 that melts when heated. When the paper base material 1 is heated above the melting point of the organic pigment 3, the heated organic pigment 3 melts and penetrates into and fills the gaps between the pulp fibers 4, making the paper base material transparent and improving transparency compared to the original base paper before the coating liquid containing the organic pigment 3 is applied.

[0046] The molten organic pigment 3 is cooled and solidifies in a state where it fills the gaps between the pulp fibers 4, thereby maintaining transparency.

[0047] Before heating, the paper base material 1 has organic pigment 3 dispersed within the base paper 2, so by locally heating a portion of the paper base material 1, the gaps between the pulp fibers 4 in the heated portion are filled with the molten organic pigment 3, making the heated portion transparent and improving its transparency. In other words, by selecting the portion to be heated, any portion of the paper base material 1 can be made transparent.

[0048] FIG. 2 is a schematic diagram showing the general configuration of a paper base material 1a obtained by heating a part of the paper base material 1 in FIG. 1 to heat, melt, and solidify the organic pigment 3. In FIG.

[0049] In the heated portion indicated by arrow A, the particulate organic pigment 3 inside melts and penetrates into the gaps between the pulp fibers 4, filling the gaps and solidifying as organic pigment 3a upon cooling.

[0050] Therefore, unlike the white, opaque paper substrate 1 in Figure 1, the heated parts of the paper substrate 1a in Figure 2 are transparent, and the transparency is improved compared to the original base paper before the coating liquid containing the organic pigment 3 is applied.

[0051] In this embodiment, the solid content of the coating liquid containing the organic pigment 3 to be coated on one side of the base paper was as shown in Table 1 below.

[0052] [Table 1]

[0053] As shown in Table 1, the solid content of the coating liquid was 80% by weight of the organic pigment and 20% by weight of the latex emulsion as the aqueous binder, on a dry weight basis.

[0054] The organic pigment used in the formulation of Table 1 was Banstar SP765 (trade name) manufactured by Chubu Saiden Co., Ltd. The average particle size of this organic pigment was approximately 0.5 μm, and its melting point was 100°C to 120°C.

[0055] As the latex emulsion, LX430 (trade name) manufactured by Zeon Corporation was used.

[0056] To improve transparency, it is desirable to increase the proportion of organic pigment, but taking into consideration the coatability of the coating liquid on the base paper, the organic pigment was set at 80% by weight.

[0057] A coating liquid containing solids consisting of this organic pigment and latex emulsion is applied to one side of the base paper and allowed to penetrate into the interior of the base paper.

[0058] Since the coating liquid contains a latex emulsion of an organic pigment, the water content of the coating liquid can be reduced, thereby reducing shrinkage after heating.

[0059] An experiment was conducted to determine the appropriate solid content concentration of this coating liquid.

[0060] In this experiment, four types of coating liquids, No. 1 to No. 4, with different solid content concentrations were prepared as shown in Table 2 below, and each coating liquid was applied to one side of tracing paper, heated to a temperature above the melting point of the organic pigment, and the occurrence of wrinkles and opacity after cooling were evaluated. The tracing paper coated with the coating liquid was placed in a dryer and heated.

[0061] [Table 2]

[0062] Tracing paper has a basis weight of 47 g / m 2 Tracing paper with a thickness of 43 μm and an opacity of 32% was used.

[0063] The opacity was measured in accordance with JIS-P-8149.

[0064] The dry coating amount of the coating liquid is 4g / m 2 It was decided.

[0065] The occurrence of wrinkles was evaluated on a three-point scale: "○" if there were no wrinkles or if another layer could be coated on top of it without any problems; "△" if there were some wrinkles or undulations but it was possible to coat another layer on top of it; and "×" if there were severe wrinkles and it was not possible to coat another layer on top of it.

[0066] The tracing papers coated with coating liquids of each solid content concentration No. 1 to No. 4 and then heated showed opacity values ​​that were smaller than the original opacity of 32%, and all showed improved transparency.

[0067] However, in coating solution No. 2, with a solids content of 20 wt%, the water content was high at 80 wt%, which caused the tracing paper to shrink significantly after heating, resulting in slight wrinkles and undulations.In coating solution No. 1, with a solids content of 10 wt%, the water content was even higher at 90 wt%, which caused the tracing paper to shrink even more significantly after heating, resulting in severe wrinkles, making it difficult to form another layer on the resulting tracing paper.

[0068] Although the tracing paper obtained by applying the No. 2 coating solution and heating showed wrinkles as described above, it was possible to form another layer by applying it on the resulting tracing paper.

[0069] On the other hand, the tracing paper obtained by applying and heating No. 3 coating liquid with a solid content of 30% by weight and the tracing paper obtained by applying and heating No. 4 coating liquid with a solid content of 40% by weight had relatively low water contents of 70% by weight and 60% by weight, respectively, so no wrinkles or undulations were observed.

[0070] However, the coating solution with a solid content of 40% by weight had a high viscosity, making it difficult to apply.

[0071] To ensure good coatability and prevent wrinkles and undulations, the solid content in the coating solution is preferably 20% by weight or more and less than 40% by weight, and more preferably 20% by weight or more and 30% by weight or less.

[0072] Next, an experiment was conducted to investigate the appropriate particle size of the particulate organic pigment.

[0073] In this experiment, organic pigments with average particle sizes of 0.5 μm, 1.0 μm, 2.0 μm, and 10 μm, as shown in Table 3 below, were used as the organic pigments with the formulation shown in Table 1 above, and four types of coating liquids, No. 5 to No. 8, with a solid content of 25% by weight were prepared. Each of the prepared coating liquids was applied to the above-mentioned 47 g / m² coatings. 2 , 4g / m on one side of tracing paper with a thickness of 43μm and an opacity of 32% 2 The organic pigment was heated to a temperature equal to or higher than the melting point of the organic pigment, and the opacity of each tracing paper was measured after cooling.

[0074] [Table 3]

[0075] As shown in Table 3, as the average particle size decreases from No. 8 to No. 5, the opacity value decreases and transparency improves.

[0076] No. 8, which has an average particle size of 10 μm, has an opacity value of 33%, which is greater than the opacity of the original tracing paper, which was 32%.

[0077] This is thought to be because the average particle size of the organic pigment is relatively large at 10 μm, so it is unable to completely penetrate into the tracing paper, with some remaining on the coated surface and preventing it from becoming transparent.

[0078] Therefore, the average particle size of the particulate organic pigment is preferably less than 10 μm.

[0079] Table 3 shows that transparency is improved compared to the original tracing paper when the average particle size of the organic pigment is between 0.5 μm and 2.0 μm.

[0080] Next, an experiment was conducted to examine the coating amount of the coating liquid.

[0081] In this experiment, the same coating liquid as No. 5 in Table 3 above, that is, a coating liquid with a solid content of 25% by weight containing an organic pigment with an average particle size of 0.5 μm in the proportions in Table 1 above, was applied to a sheet of paper with a basis weight of 47 g / m 2 The organic pigments were heated to temperatures above the melting point of the organic pigments, and the occurrence of wrinkles and opacity after cooling were evaluated. No. 12 shows the case where coating was applied to both sides of tracing paper that was 85 μm thick, which is roughly twice the thickness of 43 μm.

[0082] [Table 4]

[0083] In Table 4, Nos. 5, 9, 10, and 11 have a wet coating amount of the coating liquid of 16 g / m 2 , 24g / m 2 , 32g / m 2 , and 8g / m 2 Each was coated so that

[0084] As mentioned above, the solid content concentration is 25% by weight in all cases, so the dry coating amount of coating liquids No. 5, No. 9, No. 10, and No. 11 is 4 g / m 2 , 6g / m 2 , 8g / m 2 , and 2 g / m 2 No. 5 has the same dry coating amount as No. 5 in Table 3 above.

[0085] No. 12 was made by coating both sides of tracing paper that was approximately twice as thick as No. 5 with a wet coating amount of 16 g / m2 on each side of the tracing paper. 2 Therefore, the wet coating amount on both sides was 16 x 2 g / m 2The dry coating amount is 4 x 2 g / m 2 This becomes:

[0086] Table 4 also shows the dry coating weight of organic pigments per volume.

[0087] Dry coating amount of No. 11 coating solution: 2 g / m 2 Then, the organic pigment content is 1.6 (= 2 × 0.8) g / m 2 Therefore, the dry coating amount of organic pigment per volume is 37.21 kg / m 3 This indicates that the dry coating weight of organic pigment is the lowest among Nos. 5, 9, 10, 11, and 12. No. 11, which has the lowest dry coating weight of organic pigment, has an opacity of 29%, which is an improvement in transparency compared to the original opacity of 32% for the tracing paper. Therefore, the dry coating weight of organic pigment per volume for No. 11 is 37.21 kg / m. 3 More preferably, it is equal to or greater than this.

[0088] No.10 dry coating amount 8g / m 2 Then, the organic pigment content is 6.4 (= 8 × 0.8) g / m 2 Therefore, the dry coating amount of organic pigment per volume is 148.84 kg / m 3 Among Nos. 5, 9, 10, 11, and 12, the dry coating weight of the organic pigment is the highest. No. 10, which has the highest dry coating weight of the organic pigment, has poor coatability and is costly due to the large amount of organic pigment used. Therefore, from the standpoints of coatability and economy, the dry coating weight of the organic pigment per volume is 148.84 kg / m for No. 10. 3 Preferably, it is less than 1000 .mu.m.

[0089] In addition, the amount of water in No. 10 is 24 (= 32 - 8) g / m 2 Because the amount of the ink was so large, the tracing paper shrunk significantly after heating, causing severe wrinkles, making it difficult to form another layer on the resulting tracing paper. Also, the opacity could not be measured.

[0090] To prevent wrinkles, the amount of water should be 24 (= 32 - 8) g / m 2 It is preferable that it is less than 1000 .mu.m.

[0091] No.9 dry coating weight 6g / m 2 Then, the organic pigment content is 4.8 (= 6 × 0.8) g / m 2 Therefore, the dry coating amount of organic pigment per volume is 111.63 kg / m 3 This indicates that the dry coating amount of organic pigment is the second highest after No. 10. No. 9, which has the second highest dry coating amount of organic pigment per volume, has an opacity of 25%, which is an improvement in transparency compared to No. 11, which has an opacity of 29%.

[0092] As mentioned above, the dry coating amount of organic pigment per volume was 148.84 kg / m for No. 10. 3 It is preferable that the dry coating weight of the organic pigment No. 9 is less than 111.63 kg / m, which has improved transparency. 3 More preferably, it is:

[0093] In addition, as mentioned above, the dry coating amount of organic pigment per volume was 37.21 kg / m for No. 11. 3 The dry coating amount of organic pigment per volume is preferably 37.21 kg / m or more. 3 More than 111.63kg / m 3 Preferably, it is:

[0094] No.5 dry coating amount 4g / m 2 Then, the organic pigment content is 3.2 (= 4 × 0.8) g / m 2 Therefore, the dry coating amount of organic pigment per volume is 74.42 kg / m 3 No. 5 has an opacity of 21%, which is much more transparent than No. 11, which has an opacity of 29%.

[0095] A dry coating weight of 4 g / m was applied to each side of tracing paper that was approximately twice as thick as No. 5. 2No. 12, which was coated with each of the above, had a dry coating amount of organic pigment per volume of 75.29 kg / m, which was almost the same as No. 5. 3 The transparency of No. 12 was 21%, the same as No. 5. In other words, if the dry coating amount of organic pigment per volume is approximately the same, the opacity will be approximately the same whether it is coated on one side of thin tracing paper or on both sides of thick tracing paper.

[0096] The opacity of No. 5, 21%, and the opacity of No. 9, 25%, are both improved in transparency compared to the opacity of No. 11, 29%, so the dry coating amount of organic pigment per volume is 74.42 kg / m for No. 5. 3 Above, No. 9's 111.63 kg / m 3 More preferably, it is:

[0097] The paper base material 1 shown in Figure 1 contains an organic pigment 3 that melts when heated. By heating the paper base material 1 to above the melting point of the organic pigment 3 at the required timing, the organic pigment 3 melts and penetrates into the gaps between the pulp fibers 4, filling these gaps and making the paper transparent, while also improving transparency compared to the original base paper.

[0098] Therefore, the paper substrate 1 can be heated to become transparent when necessary.

[0099] In this case, if the entire paper base material 1 is heated to above the melting point of the organic pigment 3, the entire paper base material 1 can be made transparent, and if any part of the paper base material 1 is heated to above the melting point of the organic pigment 3 using a hot plate or the like corresponding to that part, the organic pigment 3 in that part will melt and penetrate into the gaps in the pulp fibers 4, filling the gaps and making that part transparent.

[0100] Therefore, for example, in a wrapping paper made of a paper base material 1, it is possible to heat and make transparent all but a part of it, for example, all but the part where the barcode is printed, while leaving the part where the barcode is printed white, making the wrapping paper transparent so that the inside can be seen.

[0101] Furthermore, for example, by heating a portion corresponding to the shape of a letter or figure, and making that portion transparent, the color of the base can be seen, enabling design use such as displaying the shape of the letter or figure in the color of the base.

[0102] In this embodiment, a white, opaque paper substrate 1 is provided to the user, and the user can heat the entire paper substrate 1 or any part of it to a temperature above the melting point of the organic pigment 3 at a time of their choice to make it transparent for use.

[0103] Alternatively, the entire white paper base material 1 or any desired portion thereof may be heated to a temperature equal to or higher than the melting point of the organic pigment 3 to make it transparent, and the transparent paper base material may be provided to the user.

[0104] In the above embodiment, a coating liquid containing an organic pigment is applied to the base paper to allow the organic pigment to penetrate into the interior of the base paper, but the base paper may also be impregnated with a coating liquid containing the organic pigment to allow the organic pigment 3 to penetrate into the interior of the base paper. [Explanation of symbols]

[0105] 1,1a Paper base material 2 Base paper 3,3a Organic pigments 4 Pulp Fiber

Claims

1. The ink contains a particulate organic pigment that melts when heated and has an average particle size of 0.5 μm or more and less than 10 μm, The organic pigment is selected from the group consisting of polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylic acid ester, polyacrylonitrile, polybutadiene, and copolymers thereof. A paper substrate characterized by:

2. At least a part of the organic pigment of the paper base is melted and solidified. The paper substrate of claim 1.

3. The paper base does not contain inorganic pigments; The paper substrate according to claim 1 or 2.

4. The paper substrate is tracing paper or glassine paper; The paper substrate according to claim 3.

5. A method for producing a paper substrate by coating or impregnating a base paper with a coating liquid, comprising: the coating liquid contains a particulate organic pigment that melts when heated and has an average particle diameter of 0.5 μm or more and less than 10 μm, The organic pigment is selected from the group consisting of polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylic acid ester, polyacrylonitrile, polybutadiene, and copolymers thereof. A method for producing a paper substrate, comprising:

6. The method includes a step of coating the coating liquid on at least one surface of the base paper. A method for producing the paper substrate according to claim 5.

7. a step of heating at least a portion of the base paper coated with the coating liquid to melt and solidify at least a portion of the organic pigment, The method for producing the paper substrate according to claim 6.

8. The dry coating amount of the organic pigment per unit volume in the coating step is 37.21 kg / m ３ More than 111.63kg / m ３ Below is the A method for producing the paper base material according to claim 6 or 7.

9. the coating liquid is an aqueous coating liquid containing an emulsion of the organic pigment; A method for producing the paper base material according to any one of claims 5 to 8.

10. The base paper is tracing paper or glassine paper. A method for producing the paper base material according to any one of claims 5 to 9.

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