COATED PAPER

Abstract

An object of the present invention is to provide a coated paper that includes a coating layer containing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with few coating defects. As a solution, the present invention provides a coated paper including a coating layer containing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and an adhesive, on at least one side of a paper substrate. A solid content weight ratio of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) to the adhesive in the coating layer is 99.9/0.1 to 60.0/40.0.

Claims

1. A coated paper characterized in that: the coated paper includes a coating layer comprising poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and an adhesive, on at least one side of a paper base material, wherein a solid content weight ratio of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) to the adhesive in the coating layer is in a range of 99.9/0.1 to 60.0/40.0.

2. The coated paper according to claim 1, characterized in that a coating amount (dry weight) of the coating layer is in a range of 1.0 g/m.sup.2 or more and 50.0 g/m.sup.2 or less per one side.

3. The coated paper according to claim 1, characterized in that a grammage of the paper base material is in a range of 20 g/m.sup.2 or more and 600 g/m.sup.2 or less as measured in accordance with JIS P 8124.

4. The coated paper according to claim 1, characterized in that the paper base material has the coating layer comprising the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and the adhesive, on both sides of the paper base material.

5. The coated paper according to claim 1, characterized by further comprising a seal layer between the paper base material and the coating layer.

6. The coated paper according to claim 5, characterized in that a coating amount (dry weight) of the seal layer is in a range of 3.0 g/m.sup.2 or more and 15.0 g/m.sup.2 or less per one side.

7. The coated paper according to claim 1, characterized in that the adhesive includes at least one selected from the group consisting of polyvinyl alcohols, starches, cellulose derivatives, partially-saponified ethylene-vinyl acetate copolymers, styrene-butadiene copolymer latex, conjugated diene-based polymer latex of a methyl methacrylate-butadiene copolymer, and acrylic-based polymer latex.

8. The coated paper according to claim 7, characterized in that the adhesive includes at least one selected from the group consisting of fully-saponified polyvinyl alcohol and partially-saponified polyvinyl alcohol.

9. The coated paper according to claim 7, characterized in that the adhesive includes partially-saponified ethylene-vinyl acetate copolymers.

10. The coated paper according to claim 1, characterized in that the coating layer is a heat-sealing layer.

11. The coated paper according to claim 1, characterized in that the coating layer is a water-resistant layer.

12. The coated paper according to claim 1, characterized in that the coating layer is an oil-resistant layer.

13. The coated paper according to claim 1, which is formed as a paper cup.

14. The coated paper according to claim 1, which is formed as a paper container.

15. The coated paper according to claim 1, which is formed as a paper box.

16. The coated paper according to claim 1, which is formed as a paper plate.

17. The coated paper according to claim 1, which is formed as a paper tray.

18. The coated paper according to claim 13, wherein a grammage of the paper base material is in a range of 150 g/m.sup.2 or more and 300 g/m.sup.2 or less as measured in accordance with JIS P 8124.

Description

EXAMPLES

[0086] The present invention is explained in detail below using examples; however, the present invention is obviously not limited to these examples. It should be noted that, unless otherwise specified, “parts” and “%” in the example refer to “parts by weight” and “% by weight”, respectively. Tests were conducted based on the evaluation method as shown below on the obtained coated paper.

Example 1

(Preparation of Coating Liquid 1 for Coating Layer)

[0087] A PHBH aqueous dispersion liquid with a PHBH solid content concentration of 50% by weight was obtained by the method disclosed in Patent Literature 4. Subsequently, the PHBH aqueous dispersion liquid was hydrolyzed at 60° C. to adjust the molecular weight. This gave PHBH aqueous dispersion liquid with a PHBH weight-average molecular weight of 230,000.

[0088] Next, the PHBH aqueous dispersion liquid and the adhesive (fully-saponified polyvinyl alcohol 28-98 manufactured by KURARAY CO., LTD.) were mixed to achieve a solid content weight ratio of 99.9/0.1. To the mixture was further added water, followed by stirring, to prepare the coating liquid 1 for a coating layer with a solid content concentration of 40% by weight for the PHBH and the adhesive combined.

(Production of Coated Paper)

[0089] The coating liquid 1 for a coating layer was applied to one side of a paper base material (cup base paper with a grammage of 200 g/m.sup.2) by a bar blade method so that the coating amount in dry weight was 20.0 g/m.sup.2, which was then dried at 160° C. to obtain a coated paper.

Example 2

[0090] A coated paper was obtained in the same manner as Example 1 except that the solid content weight ratio of the PHBH aqueous dispersion liquid and the adhesive in the coating liquid 1 for a coating layer was changed to 99.0/1.0.

Example 3

[0091] A coated paper was obtained in the same manner as Example 1 except that the solid content weight ratio of the PHBH aqueous dispersion liquid and the adhesive in the coating liquid 1 for a coating layer was changed to 98.0/2.0.

Example 4

[0092] A coated paper was obtained in the same manner as Example 1 except that the solid content weight ratio of the PHBH aqueous dispersion liquid and the adhesive in the coating liquid 1 for a coating layer was changed to 90.0/10.0.

Example 5

[0093] A coated paper was obtained in the same manner as Example 1 except that the solid content weight ratio of the PHBH aqueous dispersion liquid and the adhesive in the coating liquid 1 for a coating layer was changed to 80.0/20.0.

Example 6

[0094] A coated paper was obtained in the same manner as Example 1 except that the solid content weight ratio of the PHBH aqueous dispersion liquid and the adhesive in the coating liquid 1 for a coating layer was changed to 75.0/25.0.

Example 7

[0095] A coated paper was obtained in the same manner as Example 1 except that the solid content weight ratio of the PHBH aqueous dispersion liquid and the adhesive in the coating liquid 1 for a coating layer was changed to 70.0/30.0.

Example 8

[0096] A coated paper was obtained in the same manner as Example 1 except that the solid content weight ratio of the PHBH aqueous dispersion liquid and the adhesive in the coating liquid 1 for a coating layer was changed to 60.0/40.0.

Example 9

(Preparation of Coating Liquid 2 for Coating Layer)

[0097] A PHBH aqueous dispersion liquid and an adhesive (partially-saponified ethylene-vinyl acetate copolymer RS-1713 manufactured by KURARAY CO., LTD.) were mixed to achieve a solid content weight ratio of 98.0/2.0. To the mixture was further added water, followed by stirring, to prepare the coating liquid 2 for a coating layer with a solid content concentration of 40% by weight for the PHBH and the adhesive combined.

(Production of Coated Paper)

[0098] A coated paper was obtained in the same manner as Example 1 except that the coating liquid 1 for a coating layer was changed to the coating liquid 2 for a coating layer.

Example 10

(Preparation of Coating Liquid for Seal Layer)

[0099] Kaolin (KCS manufactured by Imerys) and a binder (fully-saponified polyvinyl alcohol 28-98 manufactured by KURARAY CO., LTD.) were mixed to achieve a solid content weight ratio of 90.0/10.0. To the mixture was further added water, followed by stirring, to prepare a coating liquid for a seal layer with a solid content concentration of 35% by weight.

(Production of Coated Paper)

[0100] The coating liquid for a seal layer was applied to one side of a paper base material (cup base paper with a grammage of 200 g/m.sup.2) by a bar blade method so that the coating amount in dry weight was 10.0 g/m.sup.2, which was then dried to obtain the seal layer coated paper.

[0101] The coating liquid 2 for a coating layer was applied to the seal layer of the seal layer coated paper by a bar blade method so that the coating amount in dry weight was 20.0 g/m.sup.2, which was then dried at 160° C. to obtain the coated paper.

Example 11

[0102] A coated paper was obtained in the same manner as Example 9 except that the solid content weight ratio of the PHBH aqueous dispersion liquid and the adhesive in the coating liquid 2 for a coating layer was changed to 90.0/10.0.

Example 12

(Preparation of Coating Liquid 3 for Coating Layer)

[0103] A PHBH aqueous dispersion liquid and an adhesive (oxidized starch PLV-500 manufactured by Sanwa Starch Co., Ltd.) were mixed to achieve a solid content weight ratio of 90.0/10.0. To the mixture was further added water, followed by stirring, to prepare the coating liquid 3 for a coating layer with a solid content concentration of 40% by weight.

(Production of Coated Paper)

[0104] A coated paper was obtained in the same manner as Example 1 except that the coating liquid 1 for a coating layer was changed to the coating liquid 3 for a coating layer.

Example 13

[0105] A coated paper was obtained in the same manner as Example 9 except that the coating amount of the coating layer in dry weight was changed to 1.0 g/m.sup.2.

Example 14

[0106] A coated paper was obtained in the same manner as Example 9 except that the coating amount of the coating layer in dry weight was changed to 5.0 g/m.sup.2.

Example 15

[0107] A coated paper was obtained in the same manner as Example 9 except that the coating amount of the coating layer in dry weight was changed to 10.0 g/m.sup.2.

Example 16

[0108] A coated paper was obtained in the same manner as Example 9 except that the coating amount of the coating layer in dry weight was changed to 30.0 g/m.sup.2.

Example 17

[0109] A coated paper was obtained in the same manner as Example 9 except that the coating amount of the coating layer in dry weight was changed to 40.0 g/m.sup.2.

Example 18

[0110] A coated paper was obtained in the same manner as Example 9 except that the coating amount of the coating layer in dry weight was changed to 50.0 g/m.sup.2.

Example 19

[0111] A coating liquid for a seal layer was applied to one side of a paper base material (cup base paper with a grammage of 200 g/m.sup.2) by a bar blade method so that the coating amount in dry weight was 10.0 g/m.sup.2, which was then dried to obtain the seal layer coated paper.

[0112] The coating liquid 2 for a coating layer was applied to the seal layer of this seal layer coated paper by a bar blade method so that the coating amount in dry weight was 10.0 g/m.sup.2, which was then dried at 160° C. to obtain the coated paper.

Comparative Example 1

[0113] A coated paper was obtained in the same manner as Example 1 except that the solid content weight ratio of the PHBH aqueous dispersion liquid and the adhesive (fully-saponified polyvinyl alcohol) in the coating liquid 1 for a coating layer was changed to 100/0.

Comparative Example 2

[0114] A coated paper was obtained in the same manner as Example 1 except that the solid content weight ratio of the PHBH aqueous dispersion liquid and the adhesive (fully-saponified polyvinyl alcohol) in the coating liquid 1 for a coating layer was changed to 50.0/50.0.

Comparative Example 3

[0115] A coated paper was obtained in the same manner as Example 12 except that the solid content weight ratio of the PHBH aqueous dispersion liquid and the adhesive (oxidized starch) in the coating liquid 3 for a coating layer was changed to 50.0/50.0.

(Evaluation Method)

[0116] The obtained coated paper was evaluated as follows. The results are shown in Table 1.

(1) Coating Defects

[0117] A scanning electronic microscope was used to observe the surface of the coating layer, and the presence/absence of coating defects such as cracks or pinholes in a 1-mm square area (an area of 1 mm.sup.2) was confirmed. Coating defects were evaluated according to the following criteria.

[0118] [Evaluation Criteria] [0119] ◯: No coating defect was found. [0120] X: Coating defect was found.

(2) Adhesion to Base Material

[0121] A cellophane tape (25 mm in width) was adhered to the surface of the coating layer, and a rubber roller having a width of 130 mm and a weight of 1.8 kg was rolled over the cellophane tape under its own weight back and forth 5 times to closely attach the cellophane tape to the surface of the coating layer.

[0122] Immediately after that, the cellophane tape was vigorously peeled off. The ratio of the area where the coating layer attached to the cellophane tape and was peeled from the surface of the paper base material (the area of interfacial fracture) with respect to the area to which the cellophane tape was adhered, or the ratio of the area where part of the paper base material attached to the cellophane tape together with the coating layer, so that the paper base material was damaged (the area of internal fracture of the paper base material) was calculated. The adhesion to the paper base material was evaluated according to the following criteria. When the evaluation was “⊚”, “◯”, or “Δ”, there is no practical issue. It should be noted that, when the evaluation for the ratio of the area where the coating layer was peeled off differs from the evaluation for the ratio of the area where the paper base material was damaged, more strict evaluation was chosen.

[Evaluation Criteria]

[0123] ⊚: The ratio of the area where the coating layer was peeled off was less than 5%, or the ratio of the area where the paper base material was damaged was 95% or more. [0124] ◯: The ratio of the area where the coating layer was peeled off was 5% or more and less than 10%, or the ratio of the area where the paper base material was damaged was 90% or more and less than 95%. [0125] Δ: The ratio of the area where the coating layer was peeled off was 10% or more and less than 30%, or the ratio of the area where the paper base material was damaged was 70% or more and less than 90%. [0126] X: The ratio of the area where the coating layer was peeled off was 30% or more, or the ratio of the area where the paper base material was damaged was less than 70%.

(3) Heat Sealability

[0127] Two 100-mm square test pieces were cut out from the obtained coated paper, and the pieces of coated paper were brought into contact with each other, which were then heat-sealed under a pressurizing temperature of 160° C., a pressurizing pressure of 2 kgf/cm.sup.2, and a pressurizing time of one second.

[0128] The heat-sealed test pieces were peeled apart by hand, and the peeled portion was visually observed to evaluate heat sealability according to the following criteria. When the evaluation was “◯” or “Δ”, there was no practical issue.

[Evaluation Criteria]

[0129] ◯: Peeling occurred inside the paper base material (paper base material was ruptured). [0130] A: Peeling occurred mostly inside the paper base material (paper base material was ruptured). [0131] X: Peeling occurred between the coating layers.

(4) Water Resistance

[0132] Water absorptiveness (Cobb value) was measured in accordance with “Paper and board—Determination of water absorptiveness—Cobb Method” specified in JIS P 8140: 1998 at any two points on the surface of the coating layer with a contact time of 120 seconds.

[0133] The average value of water absorptiveness (Cobb value) measured at two points was adopted as a value of water resistance, and water resistance was evaluated according to the following criteria. When the evaluation was “⊚”, “◯”, or “Δ”, there was no practical issue.

[Evaluation Criteria]

[0134] ⊚: Average value of water absorptiveness (Cobb value) was 5 g/m.sup.2 or less. [0135] ◯: Average value of water absorptiveness (Cobb value) exceeded 5 g/m.sup.2 and was 10 g/m.sup.2 or less. [0136] Δ: Average value of water absorptiveness (Cobb value) exceeded 10 g/m.sup.2 and was 20 g/m.sup.2 or less. [0137] X: Average value of water absorptiveness (Cobb value) exceeded 20 g/m.sup.2.

(5) Oil Resistance

[0138] The Kit number was measured at any five points on the surface of the coating layer in accordance with “Paper and Paperboard—Testing Method for Oil Repellency—Kit Method” specified in JAPAN TAPPI No. 41: 2000.

[0139] The average value of the Kit number measured at five points was adopted as a value of oil resistance, and water resistance was evaluated according to the following criteria. When the evaluation was “◯” or “Δ”, there was no practical issue.

[Evaluation Criteria]

[0140] ◯: Average value of Kit number was 12. [0141] Δ: Average value of Kit number was 10 or higher and lower than 12. [0142] X: Average value of Kit number was lower than 10.

TABLE-US-00001 TABLE 1 Example Example Example Example Example Example Example Example 1 2 3 4 5 6 7 8 Paper Oken 20 20 20 20 20 20 20 20 base smoothness material (seconds) Coating PHBH 99.9 99.0 98.0 90.0 80.0 75.0 70.0 60.0 layer Fully- 0.1 1.0 2.0 10.0 20.0 25.0 30.0 40.0 saponified polyvinyl alcohol Partially- 0 0 0 0 0 0 0 0 saponified ethylene- vinyl acetate copolymer Oxidized 0 0 0 0 0 0 0 0 starch Coating 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 amount (g/m.sup.2) Seal layer Absence Absence Absence Absence Absence Absence Absence Absence Coating defect ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Adhesion to paper base Δ ◯ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ material Heat sealability ◯ ◯ ◯ ◯ ◯ ◯ Δ Δ Water resistance ◯ ◯ ◯ ◯ ◯ ◯ ◯ Δ Oil resistance ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Example Example Example Example Example Example Example Example 9 10 11 12 13 14 15 16 Paper Oken 20 20 20 20 20 20 20 20 base smoothness material (seconds) Coating PHBH 98.0 98.0 90.0 90.0 98.0 98.0 98.0 98.0 layer Fully- 0 0 0 0 0 0 0 0 saponified polyvinyl alcohol Partially- 2.0 2.0 10.0 0 2.0 2.0 2.0 2.0 saponified ethylene- vinyl acetate copolymer Oxidized 0 0 0 10.0 0 0 0 0 starch Coating 20.0 20.0 20.0 20.0 1.0 5.0 10.0 30.0 amount (g/m.sup.2) Seal layer Absence Presence Absence Absence Absence Absence Absence Absence Coating defect ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Adhesion to paper base ⊚ ⊚ ⊚ ◯ Δ ◯ ⊚ ⊚ material Heat sealability ◯ ◯ ◯ ◯ Δ ◯ ◯ ◯ Water resistance ⊚ ⊚ ⊚ ◯ Δ Δ ◯ ⊚ Oil resistance ◯ ◯ ◯ ◯ Δ Δ ◯ ◯ Example Example Example Comparative Comparative Comparative 17 18 19 Example 1 Example 2 Example 3 Paper Oken 20 20 20 20 20 20 base smoothness material (seconds) Coating PHBH 98.0 98.0 98.0 100 50.0 50.0 layer Fully- 0 0 0 0 50.0 0 saponified polyvinyl alcohol Partially- 2.0 2.0 2.0 0 0 0 saponified ethylene- vinyl acetate copolymer Oxidized 0 0 0 0 0 50.0 starch Coating 40.0 50.0 10.0 20.0 20.0 20.0 amount (g/m.sup.2) Seal layer Absence Absence Presence Absence Absence Absence Coating defect ◯ ◯ ◯ X ◯ ◯ Adhesion to paper base ⊚ ⊚ ⊚ X ⊚ ◯ material Heat sealability ◯ ◯ ◯ ◯ X X Water resistance ⊚ ⊚ ⊚ Δ X X Oil resistance ◯ ◯ ◯ Δ ◯ X

[0143] The coated paper of Examples 1 to 19 according to the present invention had no coating defect in the coating layer and showed performance attributed to PHBH contained in the coating layer.

[0144] The coated paper obtained in Comparative Example 1 in which the coating layer did not include the adhesive showed a coating defect in the coating layer, and adhesion between the coating layer and the paper base material was poor.

[0145] The coated paper obtained in Comparative Examples 2 and 3 in which the coating layer included a large amount of adhesive had a coating layer without coating defects, but performance attributed to PHBH was not sufficiently manifested.