Adhesive composition and adhesive tape

Abstract

To provide an adhesive composition that is suitable for sealing a food container formed from a paper material with relatively large surface roughness.SOLUTION: An adhesive composition according to one embodiment of the present invention has a styrene-isoprene-styrene copolymer having a diblock content of 50 mass% or more, and a tackifier including at least one selected from the group consisting of an aliphatic hydrocarbon resin having 5 carbon atoms and a softening point of 65°C to 75°C, and an aliphatic hydrocarbon copolymer resin having 5 and 9 carbon atoms and a softening point of 75°C to 85°C. A content of the tackifier is 80 to 170 pts.mass with respect to 100 pts.mass of the styrene-isoprene-styrene copolymer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive tape. [Background technology]

[0002] BACKGROUND ART From the viewpoint of reducing environmental impact, there is an increasing demand for food containers made of paper materials such as pulp (for example, pulp molded containers) instead of food containers made of synthetic resins. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-233935 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional food containers made of paper are sometimes sealed with a fitting mechanism, but because the container itself is prone to deformation and the fitting is loose and easily comes off, there is a demand for fastening with adhesive tape. However, when sealing food containers with adhesive tape, if the surface roughness of the paper material is large, conventional adhesive tape cannot exhibit sufficient adhesiveness.

[0005] The present invention has been made in view of the above-mentioned problems, and has as its object to provide an adhesive composition and adhesive tape suitable for sealing food containers made of paper materials with relatively high surface roughness. [Means for solving the problem]

[0006] One aspect of the present invention is a pressure-sensitive adhesive composition comprising a styrene-isoprene-styrene copolymer having a diblock content of 50% by mass or more, and a tackifier containing at least one of an aliphatic hydrocarbon resin having 5 carbon atoms and a softening point of 65 to 75°C, and an aliphatic hydrocarbon copolymer resin having 5 or 9 carbon atoms and a softening point of 75 to 85°C, wherein the content of the tackifier is 80 to 170 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer.

[0007] Another aspect of the present invention is a pressure-sensitive adhesive composition comprising a styrene-isoprene-styrene copolymer having a diblock content of 50% by mass or more and a tackifier containing an aliphatic hydrocarbon copolymer resin having 5 or 9 carbon atoms and a softening point of 90 to 110°C, wherein the content of the tackifier is 90 to 110 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer.

[0008] Yet another aspect of the present invention is a pressure-sensitive adhesive composition comprising a styrene-isoprene-styrene copolymer having a diblock content of 50% by mass or more, a first tackifier containing an aliphatic hydrocarbon resin having 5 carbon atoms and a softening point of 65 to 75°C, and a second tackifier containing an aliphatic hydrocarbon resin having 9 carbon atoms and a softening point of 93 to 103°C, wherein the content of the first tackifier is 85 to 95 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer, and the content of the second tackifier is 5 to 15 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer.

[0009] Yet another aspect of the present invention is a pressure-sensitive adhesive composition comprising a styrene-isoprene-styrene copolymer having a diblock content of 50% by mass or more, a tackifier containing an aliphatic hydrocarbon copolymer resin having 5 or 9 carbon atoms and a softening point of 95 to 105°C, and one or more softeners selected from the group consisting of paraffin oil, aromatic oil, and naphthenic oil, wherein the content of the tackifier is 115 to 135 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer, and the content of the softener is 50 to 70 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer.

[0010] Yet another aspect of the present invention is a pressure-sensitive adhesive composition comprising a styrene-isoprene-styrene copolymer having a diblock content of 50% by mass or more, a first tackifier containing an aliphatic hydrocarbon resin having 5 carbon atoms and a softening point of 65 to 75°C, and a second tackifier containing an aliphatic hydrocarbon resin having 9 carbon atoms and a softening point of 93 to 103°C, wherein the content of the first tackifier is 115 to 125 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer, and the content of the second tackifier is 25 to 35 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer.

[0011] Yet another aspect of the present invention is a pressure-sensitive adhesive tape comprising a substrate and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of any of the above aspects and laminated on the substrate.

[0012] The pressure-sensitive adhesive tape of the above embodiment may be used to seal a food container in which at least the container body is formed from a paper material, and the paper material has an arithmetic mean roughness (Ra) of 12 to 25 μm and a ten-point mean roughness (Rz) of 61 to 100 μm. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a technology relating to an adhesive composition and an adhesive tape suitable for sealing food containers made of paper materials with a relatively high surface roughness. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic cross-sectional view of a pressure-sensitive adhesive tape according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail. In this specification, the expression "a to b" in the description of a range of numerical values ​​means that the range is from a to b, unless otherwise specified.

[0016] (Adhesive composition) (Embodiment 1) The pressure-sensitive adhesive composition according to embodiment 1 contains a styrene-isoprene-styrene copolymer and a tackifier. The pressure-sensitive adhesive composition according to embodiment 1 will be described in detail below.

[0017] (styrene-isoprene-styrene copolymer) Styrene-isoprene-styrene copolymer (SIS) contains an SI diblock copolymer in addition to a triblock copolymer. The content of the SI diblock copolymer in the SIS (hereinafter referred to as the diblock content) is 50% by mass or more. A more preferred lower limit of the diblock content is 55% by mass or more, 60% by mass or more, 65% by mass or more, or 70% by mass or more. By setting the lower limit of the diblock content to the above values, the adhesive strength of the PSA composition or a PSA tape containing the PSA composition can be further increased, and ultimately the adhesive strength of the PSA composition or the PSA tape to a pulp-molded container can be increased. The upper limit of the diblock amount is not particularly limited, but is, for example, 90% by mass or less. The diblock content can be calculated from the peak area ratio of each copolymer measured by gel permeation chromatography (GPC). The content of the styrene-derived block is not particularly limited, but is preferably 30% by mass or less, 20% by mass or less, or 15% by mass or less. If the content of the aromatic vinyl monomer-derived block is within the above range, the pressure-sensitive adhesive layer does not become too hard, and adhesion to the pulp-molded container can be improved. The lower limit of the styrene-derived block content is not particularly limited, but from the viewpoint of maintaining the cohesive strength of the pressure-sensitive adhesive composition, a preferred lower limit is 8% by mass. The content of the styrene-derived block can be calculated from the peak area ratio of each block measured by 1H-NMR.

[0018] (tackifier) The tackifier contains at least one of an aliphatic hydrocarbon resin having a softening point of 65 to 75°C and a carbon number of 5, and an aliphatic hydrocarbon copolymer resin having a softening point of 75 to 85°C and a carbon number of 5, 9. The content of the tackifier is 80 to 170 parts by mass relative to 100 parts by mass of the SIS, which can improve the adhesive strength of the adhesive composition.

[0019] (Other ingredients) The pressure-sensitive adhesive composition according to embodiment 1 may contain other components within the range that does not impair the effects of the present invention. Examples of other components include an antioxidant.

[0020] (Embodiment 2) The pressure-sensitive adhesive composition according to embodiment 2 contains a styrene-isoprene-styrene copolymer and a tackifier. The pressure-sensitive adhesive composition according to embodiment 2 will be described in detail below.

[0021] (styrene-isoprene-styrene copolymer) The styrene-isoprene-styrene copolymer (SIS) has a diblock content of 50% by mass or more. The SIS of this embodiment is the same as that of embodiment 1, and therefore a description thereof will be omitted.

[0022] (tackifier) The tackifier contains an aliphatic hydrocarbon copolymer resin having 5 or 9 carbon atoms and a softening point of 90 to 110° C. The proportion of the aliphatic hydrocarbon copolymer resin having 5 carbon atoms to the total aliphatic hydrocarbon copolymer resin having 5 or 9 carbon atoms is preferably 50 to 80 mass %, more preferably 60 to 75 mass %. The content of the tackifier is 90 to 110 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer, which can improve the adhesive strength of the pressure-sensitive adhesive composition.

[0023] (Other ingredients) The other components are the same as those in the first embodiment.

[0024] (Embodiment 3) The pressure-sensitive adhesive composition according to embodiment 3 comprises a styrene-isoprene-styrene copolymer, a first tackifier, and a second tackifier. The pressure-sensitive adhesive composition according to embodiment 3 will be described in detail below.

[0025] (styrene-isoprene-styrene copolymer) The styrene-isoprene-styrene copolymer (SIS) has a diblock content of 50% by mass or more. The SIS of this embodiment is the same as that of embodiment 1, and therefore a description thereof will be omitted.

[0026] (First tackifier) The first tackifier contains an aliphatic hydrocarbon resin having a softening point of 65 to 75°C and 5 carbon atoms. The content of the first tackifier is 85 to 95 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer, which can improve the adhesive strength of the pressure-sensitive adhesive composition.

[0027] (Second tackifier) The second tackifier contains an aliphatic hydrocarbon resin having a softening point of 93 to 103°C and 9 carbon atoms. The content of the second tackifier is 5 to 15 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer, which can improve the adhesive strength of the pressure-sensitive adhesive composition.

[0028] (Other ingredients) The other components are the same as those in the first embodiment.

[0029] (Embodiment 4) The pressure-sensitive adhesive composition according to embodiment 4 comprises a styrene-isoprene-styrene copolymer, a tackifier, and a softener. The pressure-sensitive adhesive composition according to embodiment 4 will be described in detail below.

[0030] (styrene-isoprene-styrene copolymer) The styrene-isoprene-styrene copolymer (SIS) has a diblock content of 50% by mass or more. The SIS of this embodiment is the same as that of embodiment 1, and therefore a description thereof will be omitted.

[0031] (tackifier) The tackifier contains an aliphatic hydrocarbon copolymer resin having 5 or 9 carbon atoms and a softening point of 95 to 105° C. The proportion of the aliphatic hydrocarbon copolymer resin having 5 carbon atoms to the total aliphatic hydrocarbon copolymer resin having 5 or 9 carbon atoms is preferably 50 to 80 mass %, more preferably 60 to 75 mass %. The content of the tackifier is 115 to 135 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer, which can improve the adhesive strength of the pressure-sensitive adhesive composition.

[0032] (softener) The softener is at least one selected from the group consisting of paraffin oil, aromatic oil, and naphthenic oil. The content of the softener is 50 to 70 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer, which reduces the viscosity of the pressure-sensitive adhesive composition and thereby improves the adhesive strength.

[0033] (Other ingredients) The other components are the same as those in the first embodiment.

[0034] (Embodiment 5) The pressure-sensitive adhesive composition according to embodiment 5 comprises a styrene-isoprene-styrene copolymer, a first tackifier, and a second tackifier. The pressure-sensitive adhesive composition according to embodiment 5 will be described in detail below.

[0035] (styrene-isoprene-styrene copolymer) The styrene-isoprene-styrene copolymer (SIS) has a diblock content of 50% by mass or more. The SIS of this embodiment is the same as that of embodiment 1, and therefore a description thereof will be omitted.

[0036] (First tackifier) The first tackifier contains an aliphatic hydrocarbon resin having a softening point of 65 to 75°C and 5 carbon atoms. The content of the first tackifier is 115 to 125 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer, which can improve the adhesive strength of the pressure-sensitive adhesive composition.

[0037] (Second tackifier) The second tackifier contains an aliphatic hydrocarbon resin having a softening point of 93 to 103°C and 9 carbon atoms. The content of the second tackifier is 25 to 35 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer, which can improve the adhesive strength of the pressure-sensitive adhesive composition.

[0038] (Other ingredients) The other components are the same as those in the first embodiment.

[0039] (adhesive tape) 1 is a schematic cross-sectional view of a pressure-sensitive adhesive tape 10 according to an embodiment. The pressure-sensitive adhesive tape 10 includes a substrate 20 and a pressure-sensitive adhesive layer 30.

[0040] The substrate 20 can be appropriately selected within a range that does not impair the effects of the present invention, but is preferably made of at least one material selected from the group consisting of polyethylene terephthalate (PET), polypropylene (PP), cellophane, and paper.

[0041] The thickness of the substrate 20 is not particularly limited, but can be, for example, 5 to 100 μm or 9 to 50 μm.

[0042] The surface of the substrate 20 may be subjected to an appropriate surface treatment. Examples of the surface treatment include a corona treatment to improve adhesion to the pressure-sensitive adhesive layer 30, which will be described later, and a release treatment applied to the surface opposite the pressure-sensitive adhesive layer 30.

[0043] The pressure-sensitive adhesive layer 30 is laminated on one main surface of the substrate 20. The pressure-sensitive adhesive layer 30 is formed from any of the pressure-sensitive adhesive compositions described above.

[0044] The pressure-sensitive adhesive tape 10 may include other layers that are conventionally known. Examples of such other layers include a primer layer that enhances adhesion between the substrate 20 and the pressure-sensitive adhesive layer 30, and a separator layer that is provided in contact with the pressure-sensitive adhesive layer 30 and is removed before use. In consideration of productivity and environmental impact, a straight winding (no separator) is preferred.

[0045] (Method of manufacturing adhesive tape) The pressure-sensitive adhesive tape 10 according to the embodiment can be produced by a conventionally known method. For example, the pressure-sensitive adhesive tape 10 can be produced by the following procedure.

[0046] First, the components for the adhesive composition are mixed and stirred to prepare the adhesive composition (adhesive composition production step). Next, the adhesive composition is applied onto the substrate, and then the applied composition is sequentially wound up to the required length by a winding roller (coating step). Finally, the rolled rod is cut to a required width to produce an adhesive tape (cutting step).

[0047] In addition to the above procedure, the adhesive tape may be produced by transferring an adhesive layer formed in advance on a separator to a substrate.

[0048] (Application) The pressure-sensitive adhesive tape according to the above-described embodiment is used to seal food containers made of paper material such as pulp, etc. The food containers are, for example, pulp-molded containers.

[0049] The calculated average roughness (Ra) of the paper material of the food container is 12 to 25 μm, and the ten-point average roughness (Rz) is 61 to 100 μm. The arithmetic average roughness (Ra) is calculated in accordance with JIS B 0601 using a small surface roughness measuring instrument. The ten-point average roughness (Rz) is also calculated in accordance with JIS B 0601 using a small surface roughness measuring instrument.

[0050] As described above, the adhesive tape of this embodiment has good adhesion to food containers made of paper materials having a specified surface roughness, and is therefore suitable for use in sealing such food containers.

[0051] In the food container described above, both the container body and the lid that closes the container body may be made of a paper material having the above-mentioned surface roughness, or the container body may be made of a paper material having the above-mentioned surface roughness and the lid may be made of a transparent plastic material, so that the contents contained in the container body can be seen. In other words, in the food container described above, at least the container body is made of a paper material. Furthermore, the above-mentioned food container may be in a form in which the container body and the lid are integrated and can be freely folded back via a hinge, or the container body and the lid may be separate parts and the lid may be fitted into the opening of the container body.

[0052] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations can also be adopted. [Example]

[0053] EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0054] (container) Five types of pulp-molded containers (pulp food containers) A to E with different surface roughness were prepared. The surface roughness of the paper portion of each pulp-molded container was measured using a small surface roughness measuring device. Specifically, the surface roughness (arithmetic mean roughness (Ra) and ten-point mean roughness (Rz)) was measured at eight locations on the paper surface, and the average value was calculated for each. The results (average values) obtained for surface roughness are shown in Table 1.

[0055] [Table 1]

[0056] (adhesive tape) Adhesive compositions were prepared using the components and amounts shown in Tables 2 to 9, and applied to a cellophane substrate. Each of the adhesive tapes of Examples 1 to 24 and Comparative Examples 1 to 49, each 15 mm wide, was prepared using the procedure for the adhesive tape manufacturing method described above. The raw materials shown in Tables 2 to 9 are as follows. Styrene-isoprene-styrene copolymer 1: Quintac 3433N, manufactured by Zeon Corporation Styrene-isoprene-styrene copolymer 2: Quintac 3421, manufactured by Zeon Corporation Styrene-isoprene-styrene copolymer 3: Quintac 3270, manufactured by Zeon Corporation Styrene-isoprene-styrene copolymer 4: Quintac 3520, manufactured by Zeon Corporation Styrene-isoprene-styrene copolymer 5: Eneos Material Co., Ltd., SIS 5403 Styrene-isoprene-styrene copolymer 6: Eneos Material Co., Ltd., SIS 5505 Tackifier 1: Quinton B170 manufactured by Zeon Corporation Tackifier 2: Quinton N180, manufactured by Zeon Corporation Tackifier 3: Quinton A100 manufactured by Zeon Corporation Tackifier 4: Quinton G100B, manufactured by Zeon Corporation Tackifier 5: Super Ester A-100, manufactured by Arakawa Chemical Industries, Ltd. Tackifier 6: Nitto Chemical Co., Ltd., Knit Resin (registered trademark) Coumarone G-90 Tackifier 7: Super Ester A-75, manufactured by Arakawa Chemical Industries, Ltd. Tackifier 8: Petokol (registered trademark) LX, manufactured by Tosoh Corporation Antioxidant 1: Nonflex EBP, manufactured by Seiko Chemical Co., Ltd. Softener 1: Sankyo Yuka Kogyo Co., Ltd., SNH100

[0057] (Adhesion to pulp mold) Container A was used as the adherend. Three pieces of adhesive tape were prepared for each Example and Comparative Example. A test piece of adhesive tape was pressed onto the container A using a 300g pressure roller. One minute after pressing, the adhesive tape was peeled from the edge of the main body (bowl portion) toward the bottom, and the adhesive strength was measured using a universal tensile tester. The average adhesive strength of the three points was calculated, and a sample with an average adhesive strength of 1.5 N / 10 mm or more was considered to have passed. However, samples in which the adhesive failed cohesively during adhesive strength measurement were considered to have failed even if the average adhesive strength was 1.5 N / 10 mm or more.

[0058] (Sealability evaluation when dropped) 200 g of contents were placed in container C, and the lid was placed on top. Adhesive tape was attached in two places so as to straddle the outer edge of the lid and the main body (bowl portion). The adhesive tape had an area of ​​15 mm x 30 mm. Three samples were prepared. After 3 rounds of finger pressure (approximately 300g of pressure), 20 minutes later, Container C was hung from a support pole by a 10cm long string, and when Container C was lifted up to the support pole and dropped, the number of times until the adhesive tape peeled off was counted. The data for the 3 points was rounded up or down, and 10 times or more was considered a pass.

[0059] (Applicability evaluation) Test pieces of adhesive tape (15 mm wide, 100 mm long) were attached to the paper portion of pulp molded containers A to E, sealing them so that the adhesive tape was 50 mm long on both the lid and the body (bowl portion). When applying the adhesive tape, light pressure was applied with the pad of a finger. After application, the containers were left to stand for 24 hours in an environment of 40°C and 75% RH, and then the adhesiveness of the adhesive tape was evaluated according to the following evaluation criteria. A rating of 4 or higher was considered a pass. <Evaluation criteria> 5: There is no lifting of the adhesive tape over the entire application surface, or the lifting area is less than 1% of the application surface, and there is high resistance when peeling the adhesive tape 4: There is no lifting of the adhesive tape over the entire application surface, or the lifting area is less than 1% of the application surface, and the resistance when peeling the adhesive tape is low 3: The adhesive tape is floating over an area of ​​1% to less than 20% of the adhesive surface. 2: The adhesive tape is floating over 20% to less than 50% of the application surface. 1: The adhesive tape is floating over 50% or more of the application surface.

[0060] [Table 2]

[0061] [Table 3]

[0062] [Table 4]

[0063] [Table 5]

[0064] [Table 6]

[0065] [Table 7]

[0066] [Table 8]

[0067] [Table 9] [Industrial Applicability]

[0068] The adhesive composition and adhesive tape of this embodiment have good adhesion to food containers made of paper materials having a specified surface roughness, and can therefore be suitably used to seal such food containers. [Explanation of symbols]

[0069] 10 adhesive tape, 20 substrate, 30 adhesive layer

Claims

1. a styrene-isoprene-styrene copolymer having a diblock content of 50% by mass or more; a tackifier containing at least one of an aliphatic hydrocarbon resin having 5 carbon atoms and a softening point of 65 to 75°C, and an aliphatic hydrocarbon copolymer resin having 5 and 9 carbon atoms and a softening point of 75 to 85°C; and The pressure-sensitive adhesive composition has a tackifier content of 80 to 170 parts by mass relative to 100 parts by mass of the styrene-isoprene-styrene copolymer.

2. a styrene-isoprene-styrene copolymer having a diblock content of 50% by mass or more; a tackifier containing an aliphatic hydrocarbon copolymer resin having 5 or 9 carbon atoms and a softening point of 90 to 110°C; and The pressure-sensitive adhesive composition has a tackifier content of 90 to 110 parts by mass relative to 100 parts by mass of the styrene-isoprene-styrene copolymer.

3. a styrene-isoprene-styrene copolymer having a diblock content of 50% by mass or more; a first tackifier containing an aliphatic hydrocarbon resin having 5 carbon atoms and a softening point of 65 to 75°C; a second tackifier containing an aliphatic hydrocarbon resin having 9 carbon atoms and a softening point of 93 to 103°C; and the content of the first tackifier is 85 to 95 parts by mass relative to 100 parts by mass of the styrene-isoprene-styrene copolymer, The pressure-sensitive adhesive composition, wherein the content of the second tackifier is 5 to 15 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer.

4. a styrene-isoprene-styrene copolymer having a diblock content of 50% by mass or more; a tackifier containing an aliphatic hydrocarbon copolymer resin having 5 or 9 carbon atoms and a softening point of 95 to 105°C; one or more softeners selected from the group consisting of paraffin oil, aromatic oil, and naphthenic oil; and the content of the tackifier is 115 to 135 parts by mass relative to 100 parts by mass of the styrene-isoprene-styrene copolymer, The pressure-sensitive adhesive composition, wherein the content of the softener is 50 to 70 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer.

5. a styrene-isoprene-styrene copolymer having a diblock content of 50% by mass or more; a first tackifier containing an aliphatic hydrocarbon resin having 5 carbon atoms and a softening point of 65 to 75°C; a second tackifier containing an aliphatic hydrocarbon resin having 9 carbon atoms and a softening point of 93 to 103°C; and the content of the first tackifier is 115 to 125 parts by mass relative to 100 parts by mass of the styrene-isoprene-styrene copolymer, The pressure-sensitive adhesive composition, wherein the content of the second tackifier is 25 to 35 parts by mass per 100 parts by mass of the styrene-isoprene-styrene copolymer.

6. A pressure-sensitive adhesive tape comprising: a substrate; and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to claim 1 laminated on the substrate.

7. 7. The pressure-sensitive adhesive tape according to claim 6, which is used for sealing a food container, at least the container body being formed from a paper material, the paper material having an arithmetic mean roughness (Ra) of 12 to 25 μm and a ten-point mean roughness (Rz) of 61 to 100 μm.

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