Ink supply tube

Abstract

To provide an ink supply tube having high flexibility, moldability and shape recovery, and less irregularity on an inner surface.SOLUTION: An ink supply tube contains: a styrene-isobutylene-styrene block copolymer of 20 mass% or more and 30 mass% or less; a polytetrafluoroethylene-based resin of 0.5 mass% or more and 2 mass% or less; and a thermoplastic resin (excluding the styrene-isobutylene-styrene block copolymer and the polytetrafluoroethylene-based resin).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an ink supply tube.

Background Art

[0002] A large number of inkjet printing apparatuses have been developed. In an inkjet printing apparatus, it is common to use a flexible ink supply tube at the connection between an ink tank for storing ink and a print head portion. Such an ink supply tube is required to have not only flexibility, but also high gas barrier properties, high shape recovery after an external force is applied, and little elution of impurities. Furthermore, it is also required that the inner peripheral surface has few irregularities so as not to generate bubbles when the ink flows.

[0003] Here, inks used in inkjet printing apparatuses include water-based inks, solvent-based inks, UV-curable inks, etc., and the composition of the ink supply tube is often selected according to the type of ink. For example, in the ink supply tube of a printing apparatus using a water-based ink, butyl rubber or styrene-based thermoplastic elastomers are often used.

[0004] Butyl rubber has high gas barrier properties and can have high flexibility depending on its composition, but impurities may elute into the ink. Also, butyl rubber has the problem of being expensive because crosslinking is required during production. On the other hand, styrene-based thermoplastic elastomers have the advantage of not requiring a crosslinking step during the production of an ink supply tube and being relatively inexpensive. Conventionally, a styrene-ethylene-butylene-styrene copolymer (hereinafter also referred to as "SEBS") having high flexibility and shape recovery has been suitably used as the main component of an ink supply tube. Also, a styrene-isobutylene-styrene copolymer (hereinafter also referred to as "SIBS") having high gas barrier properties and flexibility has been suitably used as the main component of an ink supply tube (for example, Patent Document 1).

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2012-51368 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the aforementioned SIBS can sometimes have poor shape recovery. Therefore, attempts have been made to improve shape recovery by increasing the molecular weight. However, while increasing the molecular weight improves shape recovery, it tends to decrease flexibility and moldability. Furthermore, when ink supply tubes are made from high molecular weight SIBS, there is a problem in that irregularities tend to form on the inner surface of the ink supply tube, and air bubbles tend to form in the ink. The main objective of this invention is to provide an ink supply tube that has high flexibility, moldability, and shape recovery properties, and has minimal internal irregularities. [Means for solving the problem]

[0007] In other words, the present invention is Styrene-isobutylene-styrene block copolymer in an amount of 20% to 30% by mass, Polytetrafluoroethylene resin in an amount of 0.5% to 2% by mass, Thermoplastic resins (excluding the styrene-isobutylene-styrene block copolymer and the polytetrafluoroethylene resin) including It is an ink supply tube. , The thermoplastic resin comprises a styrene-ethylene-butylene-styrene block copolymer and an olefin-based resin. The amount of styrene-ethylene-butylene-styrene block copolymer in the ink supply tube is 50% by mass or more and 70% by mass or less. The amount of olefin resin in the ink supply tube is 10% by mass or more and 20% by mass or less. We provide tubes for supplying ink. [Effects of the Invention]

[0008] According to the present invention, an ink supply tube is provided that has high flexibility, moldability, and shape recovery properties, and has few internal irregularities. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view of an ink supply tube according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] The following describes an ink supply tube according to one embodiment of the present invention. The ink supply tube of this embodiment is a tube used to connect the ink tank and the print head within an inkjet printing apparatus. This ink supply tube is particularly suitable for use in inkjet printing apparatuses that use water-based inks. A schematic cross-sectional view of the ink supply tube is shown in Figure 1. The ink supply tube 100 may have a structure in which multiple (four in Figure 1) single-core tubes 11 are connected by connecting parts 12, as shown in Figure 1(a), or it may consist only of single-core tubes 11, as shown in Figure 1(b). Note that when multiple single-core tubes 11 are connected by connecting parts 12, as shown in Figure 1(a), it is common to separate the individual single-core tubes 11 by tearing or cutting the connecting parts 12 when using the tube, i.e., when placing it in an inkjet printing device. The shape of the connecting parts 12 is not particularly limited, and the width and thickness of the connecting parts 12 can be selected as appropriate.

[0011] Furthermore, the single-core tube 11 is a cylindrical structure made of a single layer. The outer diameter and inner diameter may vary within the single-core tube 11, but it is preferable that the single-core tube 11 has a uniform outer diameter and inner diameter from one end to the other. In both the embodiment shown in Figure 1(a) and the embodiment shown in Figure 1(b), the inner diameter and outer diameter of the single-core tube 11 are appropriately selected according to the structure of the inkjet printing device. In a typical ink supply tube 100 for an inkjet printing device, the inner diameter of the single-core tube 11 is about 1 mm to 3 mm, and the outer diameter is about 3 mm to 5 mm. On the other hand, the length of the single-core tube 11 is not limited. For example, it may be cut to a predetermined length to match the inkjet printing device, or it may be long so that the user (manufacturer of the inkjet printing device) can cut it to a predetermined length when using the ink supply tube 100.

[0012] Here, the ink supply tube 100 (single-core tube 11) contains at least styrene-isobutylene-styrene block copolymer (SIBS), polytetrafluoroethylene resin (hereinafter also referred to as "PTFE resin"), and thermoplastic resin.

[0013] SIBS is a triblock copolymer in which a styrene block mainly containing structural units derived from styrene or its derivatives and an isobutylene block mainly containing structural units derived from isobutylene are arranged in the order of styrene block / isobutylene block / styrene block. The ink supply tube 100 may contain only one type of SIBS, or it may contain two or more types of SIBS that differ, for example, in weight-average molecular weight or the ratio of styrene block to isobutylene block. Here, the ratio of styrene blocks to isobutylene blocks in the SIBS is appropriately selected according to the desired physical properties. A ratio of approximately 3:7 (styrene blocks:isobutylene blocks) is preferred. A higher proportion of styrene blocks tends to improve shape recovery, while a higher proportion of isobutylene blocks tends to improve flexibility. Furthermore, the melt flow rate (MFR), measured at 230°C and 2.16 kgf in accordance with JIS K7210 for SIBS, is preferably 6.0 or less, and more preferably less than 6.0. When the MFR of SIBS is within this range, the SIBS tends to mix more uniformly with thermoplastic resins, etc., as described later, and its shape recovery properties tend to be better. The amount of SIBS mentioned above is 20% by mass or more and 30% by mass or less of the total amount of ink supply tubes. When the amount of SIBS is 20% by mass or more, the gas barrier properties of the ink supply tubes tend to be good. On the other hand, when the amount of SIBS is 30% by mass or less, the surface smoothness of the resulting ink supply tubes, especially the surface smoothness inside the tubes, tends to be good, and air bubbles are less likely to form in the ink.

[0014] Furthermore, the polytetrafluoroethylene resin (PTFE resin) may be polytetrafluoroethylene or a derivative thereof, for example, a resin obtained by modifying polytetrafluoroethylene with acrylic. In this embodiment, a PTFE resin having fibril-forming ability is particularly preferred. A PTFE resin having fibril-forming ability refers to a resin (or structure, mixture, etc.) containing polytetrafluoroethylene (PTFE) which has a large molecular weight and tends to become fibrous due to external forces such as shear force. The number-average molecular weight of the PTFE that tends to become fibrous is, for example, several million to tens of millions. When the PTFE resin having fibril-forming ability is combined with the SIBS or the thermoplastic resin described later, the melt tension of the SIBS or thermoplastic resin is improved, and the surface smoothness of the inner surface of the ink supply tube tends to improve. Examples of PTFE resins with fibril-forming ability include core-sheath structures having a core made of high molecular weight PTFE and a sheath made of low molecular weight PTFE arranged around it; co-aggregated mixtures of high molecular weight PTFE and other resins; and mixtures obtained by polymerizing other monomers in the presence of high molecular weight PTFE and mixing PTFE with other resins. However, PTFE resins with fibril-forming ability are not limited to these. The amount of the PTFE-based resin is 0.5% by mass or more and 2% by mass or less with respect to the total amount of the ink supply tube. When the amount of the PTFE-based resin is 0.5% by mass or more, the surface smoothness of the obtained ink supply tube, particularly the surface smoothness inside the tube, tends to be good, and it becomes difficult for bubbles to generate in the ink. On the other hand, when the amount of the PTFE-based resin is 2% by mass or less, it becomes difficult for impurities to elute into the ink.

[0015] Also, the thermoplastic resin is a resin other than the above-mentioned SIBS and PTFE-based resins, and any resin compatible with these may be used. The type of the thermoplastic resin is appropriately selected according to desired physical properties, the type of the ink flowing inside the ink supply tube, and the like. Examples of preferred thermoplastic resins include styrene-ethylene-butylene-styrene block copolymer (SEBS), polyolefin-based resins, and the like. Examples of the polyolefin-based resins include, for example, olefin homopolymers such as polyethylene, polypropylene, and polybutene; copolymers of ethylene and α-olefins such as ethylene-propylene; and the like. Among these, SEBS and polyethylene are particularly preferred, and it is particularly preferred to contain both of them. When the above-mentioned SIBS and SEBS are combined, an extremely excellent ink supply tube having both the gas barrier property of SIBS and the shape recovery property of SEBS is obtained. The ratio of the contents of SIBS and SEBS in the ink supply tube is preferably about 1:1.5 to 1:3.5. Also, the amount of SEBS is preferably 50% by mass or more and 70% by mass or less with respect to the total amount of the ink supply tube, and more preferably 53% by mass or more and 63% by mass or less. When the amount of SEBS is 50% by mass or more, the shape recovery property of the obtained ink supply tube tends to be good. On the other hand, when the amount of SEBS is 70% by mass or less, the gas barrier property and the like of the ink supply tube tend to be good. On the other hand, when an olefin-based resin such as polyethylene is combined, the strength of the ink supply tube tends to be good. The amount of the olefin-based resin (particularly polyethylene) is preferably 10% by mass or more and 20% by mass or less with respect to the total amount of the ink supply tube, and more preferably 16% by mass or more and 17% by mass or less. In addition, the total amount of the thermoplastic resin is preferably 65% by mass or more and 79.5% by mass or less, more preferably 69% by mass or more and 79.5% by mass or less, based on the total amount of the ink supply tube. When the amount of the thermoplastic resin is within this range, the strength of the ink supply tube becomes good.

[0016] Moreover, the ink supply tube may further contain components other than those described above, as long as the object and effects of the present embodiment are not impaired.

[0017] The above-described ink supply tube preferably has the following physical properties. When the thickness of the ink supply tube is 6 mm, the durometer A hardness is preferably 40 or more and 50 or less. When the durometer A hardness of the ink supply tube is within this range, the ink supply tube is likely to have appropriate flexibility. The above durometer A hardness is a value measured with a durometer type A hardness meter in accordance with JIS K6253, by pressing a needle against a sheet made of the same material as the ink supply tube with a thickness of 6 mm, and adopting the value after 15 seconds from when the needle is pressed as the durometer A hardness. The durometer A hardness of the ink supply tube can be adjusted, for example, by the type of the above SIBS, the weight average molecular weight, etc.

[0018] When the thickness of the ink supply tube is 6 mm, the compression set is preferably 45% or less. When the compression set of the ink supply tube is within this range, even when an external force is applied to the ink supply tube, the shape is likely to be restored. The above compression set is the ratio of the amount of deformation after compression to the thickness before compression when a sheet made of the same material as the ink supply tube with a thickness of 6 mm is press-molded and compressed at 70 °C for 22 hours at 25% in accordance with JIS K6262. Specifically, when the thickness before compression is t0 and the thickness after compression is t1, it is a value obtained by {(t0 - t1) / t0} × 100. The above permanent set can be adjusted, for example, by the type of the above SIBS, the weight average molecular weight, the ratio of SIBS to SEBS, etc.

[0019] When the thickness of the ink supply tube is 0.5 mm, the moisture permeability measured by the cup method at 40°C and 90% Rh is 5 g / m². 2 • 24 hours or less is preferable. When the moisture permeability of the ink supply tube is within this range, the solvent is less likely to evaporate from the ink flowing inside the ink supply tube, and the composition of the ink is less likely to change. The above moisture permeability can be adjusted, for example, by the SIBS content.

[0020] Furthermore, the maximum height Rz of the inner surface of the ink supply tube, measured in accordance with JIS B0601 (2001), is preferably 15 μm or less. When the roughness (Rz) of the inner surface of the ink supply tube is 15 μm or less, air bubbles are less likely to form in the ink when the ink flows or when the ink remains inside the ink supply tube. The above surface roughness can be adjusted, for example, by the amount of PTFE resin or the ratio of SIBS to SEBS.

[0021] The method for manufacturing the ink supply tubes is not particularly limited and can be manufactured by known methods. The above-mentioned SIBS, PTFE resin, and thermoplastic resin, as well as other components as needed, are mixed using closed-type or batch-type mixing equipment such as Laboplast mills, Brabenders, Banbury mixers, kneaders, and rolls; or continuous-type melt-mixing equipment such as single-screw or twin-screw extruders. The composition is then processed into ink supply tubes of the desired shape by methods such as extrusion molding, injection molding, press molding, and blow molding. Among these methods, extrusion molding is particularly efficient for manufacturing ink supply tubes. [Examples]

[0022] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited in any way by these examples, and the embodiments can be modified without departing from the spirit of the invention.

[0023] 1. Preparation of materials The following materials were used in the examples and comparative examples. The MFR (Melt Flow Rate) of the SIBS was measured at 230°C and 2.16 kgf in accordance with JIS K7210. (1) SIBS • SIBS-A: SIBSTAR 073T-UL (manufactured by Kaneka Corporation, MFR: 6g / 10 mins) • SIBS-B: SIBSTAR 103T-UL (manufactured by Kaneka Corporation, MFR: 0.1g / 10 mins) (2)Thermoplastic resin • SEBS: EARNESTON CJ103 (manufactured by Kuraray Co., Ltd.) • Polyethylene (PE) resin: (NUC Corporation, low-density polyethylene) (3)PTFE resin • A-3000: (Acrylic-modified PTFE resin, Metabrene (product name), manufactured by Mitsubishi Chemical Corporation) (4) Others • Acrylic processing aid: P-530A (manufactured by Mitsubishi Chemical Corporation)

[0024] 2. Preparation of ink supply tubes SIBS, thermoplastic resin, and PTFE resin (or acrylic processing aid) were mixed in a kneader with the composition shown in Table 1 below, and then pelletized in a pelletizer. However, in Comparative Examples 4 to 6, this process was omitted, and commercially available SIBS or SEBS pellets were used as is. The pellets were then melted and extruded from a die to produce single-core ink supply tubes with an outer diameter of 3.8 mm and an inner diameter of 1.8 mm.

[0025] 3. Measurement and evaluation of physical properties The ink supply tubes were evaluated and their physical properties were assessed as follows. The results are shown in Table 1. (1) Measurement of Durometer A hardness The pellets prepared in each example and comparative example were press-molded into 6 mm thick sheets. Then, in accordance with JIS K6253, the indenter of a durometer type A hardness tester was applied, and the value was measured after 15 seconds. (2) Measurement of compression set Sheets prepared using the same method as for measuring durometer A hardness were compressed by 25% at 70°C for 22 hours, in accordance with JIS K6262. The ratio of the thickness after compression (amount of deformation) to the thickness before compression was then measured. (3) Measurement of moisture permeability The pellets prepared in each example and comparative example were press-molded into 0.5 mm thick sheets. Then, the moisture permeability at 40°C and 90% Rh was measured using the cup method. (4) Measurement of the inner surface roughness of the tube The ink supply tubes prepared in each example and comparative example were cut open, and the surface roughness of the inner surface was measured in accordance with JIS B0601 (2001) to determine the maximum height Rz. (5) Evaluation of whether or not bubbles are formed The ink supply tubes prepared in each example and comparative example were immersed in ink for 14 days under conditions of 30°C and 10% Rh, and the presence or absence of air bubbles was checked. ○: No bubbles can be seen with the naked eye. ×: Bubbles can be seen with the naked eye. (6) Evaluation of impurity elution 50g of ink supply tubes prepared in each example and comparative example were immersed in ink for 3 months under conditions of 30°C and 10% Rh, and the presence or absence of leaching of impurities was checked. ○: Impurities such as Si, dirt, foreign matter, and oil are below the standard value. ×: Impurities such as Si, dirt, foreign matter, and oil are detected at levels exceeding the standard.

[0026] 3.Results [Table 1]

[0027] As shown in Table 1 above, when the ink contained 20% to 30% by mass of SIBS and 0.5% to 2% by mass of PTFE resin, the inner surface roughness of the tube was small (15 μm or less), and no bubbles were observed in the ink. Furthermore, no impurity leaching into the ink was observed in these ink supply tubes. In addition, the durometer A hardness was between 40 and 50, and the compression set was 45% or less. In other words, the shape recovery was good. Furthermore, the moisture permeability (gas barrier property) was 5 g / m 2 • The time was less than 24 hours and was very good (Examples 1-5). In contrast, Comparative Example 6, which consisted only of SEBS and did not contain SIBS or PTFE-based resins, showed good flexibility and shape recovery, but low moisture permeability (gas barrier properties). On the other hand, Comparative Examples 4 and 5, which consisted only of SIBS resin, had large compression set, meaning they had poor shape recovery. Furthermore, the inner surface roughness of the tubes was large, making it easy for air bubbles to form in the ink. Also, even when SIBS resin was included, if its amount was less than 20% by mass, the gas barrier properties were low. Furthermore, when PTFE resin was not included, or when an acrylic processing aid was included instead of PTFE resin, the inner surface roughness of the tube was large, and air bubbles were easily generated in the ink (Comparative Examples 1 and 3). In addition, when there was too much PTFE resin, Si elution was confirmed (Comparative Example 2). [Industrial applicability]

[0028] The ink supply tube of the present invention has high flexibility, moldability, and shape recovery properties, and has few internal irregularities. Therefore, it can be suitably used in inkjet printing equipment, particularly inkjet printing equipment for printing with water-based inkjet inks. [Explanation of Symbols]

[0029] 11 Single-core tube 12 Connecting part 100 ink supply tubes

Claims

[Claim 1] A styrene-isobutylene-styrene block copolymer in an amount of 20% to 30% by mass, Polytetrafluoroethylene resin in an amount of 0.5% to 2% by mass, Thermoplastic resins (excluding the styrene-isobutylene-styrene block copolymer and the polytetrafluoroethylene resin) It is an ink supply tube that includes, The thermoplastic resin comprises a styrene-ethylene-butylene-styrene block copolymer and an olefin-based resin. The amount of styrene-ethylene-butylene-styrene block copolymer in the ink supply tube is 50% by mass or more and 70% by mass or less. The amount of olefin resin in the ink supply tube is 10% by mass or more and 20% by mass or less. Ink supply tube.

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