Manufacturing method for straws and manufacturing method for extendable straws

Abstract

To provide a method for manufacturing a straw having excellent processability for a widening part of a straw body made from an aliphatic polyester-based resin such as a biodegradable resin.SOLUTION: There is provided a method for manufacturing a straw, comprising a first step and a second step. In the second step of heating an end part of a straw body containing an aliphatic polyester-based resin to form a widened portion at the end part, a heating temperature t (°C) of the end part of the straw body satisfies the following formula (1): 0.50≤ΔHt / ΔHtotal≤0.791 (1) wherein ΔHt is a crystal melting enthalpy from t (°C) to a total crystal melting temperature (°C) in differential scanning calorimetry of a fully crystallized straw body, and ΔHtotal is a total crystal melting enthalpy from 20°C to the total crystal melting temperature (°C) in differential scanning calorimetry of the straw body.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a straw and a method for manufacturing an extendable straw. [Background technology]

[0002] As a drinking straw attached to a commercially available beverage container, for example, a two-stage telescopic straw is known. The telescopic straw is composed of a small-diameter inner straw having an expanded portion at its end, and a large-diameter outer straw having a contracted portion at its end. The telescopic straw is configured such that the inner straw is inserted into the outer straw. When the telescopic straw is lengthened, the expanded portion of the inner straw is engaged with the contracted portion of the outer straw so that the inner straw does not slip out of the outer straw.

[0003] For example, Patent Document 1 discloses a technique for forming a widened portion at the end of an inner straw by inserting and removing a heated mold having approximately the same shape as the widened portion formed at the end of the inner straw.

[0004] Aliphatic polyester resins are also used for various purposes. Among them, biodegradable resins such as poly(3-hydroxyalkanoate) resins have attracted attention as environmentally friendly resins due to their biodegradability. Attempts are being made to develop extendable straws using such biodegradable resins as raw materials. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-058514 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when forming a widened portion on a straw made of an aliphatic polyester resin such as a biodegradable resin, the technique described in Patent Document 1 leaves room for improvement in terms of processability of the widened portion.

[0007] One aspect of the present invention aims to provide a method for manufacturing a straw that has excellent processability for the widening portion of a straw body made from an aliphatic polyester resin such as a biodegradable resin, and a method for manufacturing an extendable straw. [Means for solving the problem]

[0008] In order to solve the above problems, a method for producing a straw according to one aspect of the present invention includes a first step of producing a tubular straw body using a resin composition containing an aliphatic polyester resin, and a second step of heating an end of the straw body to form a widened portion at the end. In the second step, the heating temperature t (°C) of the end of the straw body is calculated based on the following formula (1): 0.50≦ΔH t / ΔH total ≦0.791 (1) ΔH t : In the differential scanning calorimetry analysis of the straw body, the crystalline melting enthalpy from t (℃) to the total crystalline melting temperature (℃) ΔH total : Total crystalline melting enthalpy from 20℃ to the total crystalline melting temperature (℃) in differential scanning calorimetry of the fully crystallized straw body Meet the following. Effect of the Invention

[0009] According to one aspect of the present invention, the widening portion has excellent processability for a straw body made from an aliphatic polyester resin such as a biodegradable resin. [Brief description of the drawings]

[0010] [Figure 1]FIG. 1 shows a schematic diagram of an example of the second step in a manufacturing method according to one embodiment of the present invention, in which 101 is a cross-sectional view showing the schematic configuration of a straw body used in the second step, 102 to 104 are schematic views showing each step of the second step, and 105 is a cross-sectional view showing the schematic configuration of a straw manufactured by the second step. [Diagram 2] 1 is a graph showing an example of a DSC curve obtained by differential scanning calorimetry of a straw body, illustrating ΔHt and ΔHtotal. [Diagram 3] 301 and 302 are diagrams showing an example of a method for manufacturing an extendable straw according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An embodiment of the present invention will be described in detail below. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more, B or less." In addition, all documents described in this specification are incorporated herein by reference.

[0012] [Technical philosophy] The inventors of the present application have discovered that when a straw body is made from aliphatic polyester resins such as biodegradable resins, when a widened portion is formed at the end using a heated mold, the widened portion may crack or whiten, resulting in poor processability of the widened portion.

[0013] Therefore, the inventors of the present application conducted intensive research with the aim of developing an expandable straw made from aliphatic polyester resins such as biodegradable resins. As a result, the inventors of the present application focused on the relationship between the heating temperature of the end of the straw body that forms the widening part and the melting enthalpy of the straw body. They discovered that the workability of the widening part is excellent by setting a specific parameter related to the melting enthalpy of the straw body within a specific range, and arrived at the method of manufacturing the straw according to this embodiment.

[0014] That is, the method for producing a straw according to this embodiment (hereinafter, sometimes referred to as this production method) includes a first step of producing a tubular straw body using a resin composition containing an aliphatic polyester resin, and a second step of heating the end of the straw body to form a widened portion at the end. In the second step, the heating temperature t (°C) of the end of the straw body is expressed by the following formula (1): 0.50≦ΔH t / ΔH total ≦0.791 (1) ΔH t : In the differential scanning calorimetry analysis of the straw body, the crystalline melting enthalpy from t (℃) to the total crystalline melting temperature (℃) ΔH total : Total crystalline melting enthalpy from 20℃ to the total crystalline melting temperature (℃) in differential scanning calorimetry of the fully crystallized straw body It is a method to satisfy the above.

[0015] Furthermore, the manufacturing method of the extendable straw according to this embodiment is a method that includes this manufacturing method as one step.

[0016] According to this manufacturing method, in the second step, ΔH t / ΔH total Since formula (1) is satisfied, the widened portion has excellent workability. Hereinafter, the present manufacturing method will be described in detail.

[0017] (Aliphatic polyester resin) In this manufacturing method, an aliphatic polyester resin is used as the raw material for the straw body. The aliphatic polyester resin is not particularly limited, but is preferably biodegradable. The aliphatic polyester resin is preferably a poly(3-hydroxyalkanoate) resin (hereinafter, sometimes referred to as P3HA resin). In this specification, "P3HA resin" refers to a 3-hydroxyalkanoic acid repeating unit represented by the general formula: [-CHR-CH2-CO-O-] (wherein R is C n H 2n+1where n is an integer of 1 or more and 15 or less.) is a polyhydroxyalkanoate containing this as a repeating unit.

[0018] More specifically, the P3HA resin preferably contains 3-hydroxybutyrate (3HB) units. The P3HA resin is preferably one or more selected from the group consisting of poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HV3HH), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate). The P3HA resin may contain only one type, or may contain two or more types.

[0019] The P3HA resin is preferably a P3HA resin produced by a microorganism (a microbially produced P3HA resin). A microbially produced P3HA resin is usually composed only of D-form (R-form) polyhydroxyalkanoate monomer units. Among the microbially produced P3HA resins, P3HB, P3HB3HH, P3HB3HV, P3HB3HV3HH, and P3HB4HB are preferred, and P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are more preferred, in terms of ease of industrial production.

[0020] The P3HA resin can also be produced by, for example, the method described in International Publication No. 2010 / 013483. Commercially available P3HA resins include Kaneka Biodegradable Polymer PHBH (registered trademark) manufactured by Kaneka Corporation.

[0021] The P3HA resin also contains at least one copolymer of 3HB units and other hydroxyalkanoate units, and the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin account for 65.0 to 99.0 mol %, preferably 68.0 to 98.5 mol %, more preferably 70.0 to 98.5 mol %, and even more preferably 70.0 to 98.0 mol %, of all repeating units (100 mol %).

[0022] When the composition ratio of the 3HB repeating unit is 90.0 mol% or more, the rigidity of the P3HA resin is improved, the crystallization speed is accelerated, burrs are reduced, and productivity tends to be improved. On the other hand, when the composition ratio of the 3HB repeating unit is 99.0 mol% or less, the melting point is lower than the thermal decomposition temperature, so stable and continuous production is possible. The monomer composition ratio of the P3HA resin can be measured by gas chromatography or the like (see, for example, International Publication No. 2014 / 020838).

[0023] The molecular weight of the P3HA resin is not particularly limited as long as it shows substantially sufficient physical properties for the intended use. The weight average molecular weight of the P3HA resin is preferably in the range of 100,000 to 1,000,000, more preferably 150,000 to 700,000, further preferably 200,000 to 500,000, and particularly preferably 250,000 to 450,000. When the weight average molecular weight is 100,000 or more, appropriate mechanical strength is obtained. In addition, when the molecular weight is 1,000,000 or less, the increase in melt viscosity can be suppressed, and the moldability is excellent.

[0024] The weight average molecular weight can be measured by gel permeation chromatography (GPC) (Shodex GPC-101, manufactured by Showa Denko K.K.), using a polystyrene gel (Shodex K-804, manufactured by Showa Denko K.K.) as a column, and using chloroform as a mobile phase, and can be calculated as a molecular weight converted into polystyrene. In this case, a calibration curve is prepared using polystyrenes with weight average molecular weights of 31,400, 197,000, 668,000, and 1,920,000. As the column for the GPC, a column appropriate for measuring the molecular weight may be used.

[0025] According to this embodiment, when P3HA-based resin is used as the raw material for the straw body, marine pollution due to disposal can be suppressed, which can contribute to the achievement of Sustainable Development Goals (SDGs) such as Goal 12 "Ensure sustainable consumption and production patterns" and Goal 14 "Conserve and sustainably use the oceans and marine resources for sustainable development."

[0026] The aliphatic polyester resin is not limited to a P3HA resin, and may be, for example, at least one selected from the group consisting of polybutylene succinate (PBS), polybutylene succinate-co-butylene adipate (PBSA), and polylactic acid.

[0027] (1st step) In the first step, a cylindrical straw body is manufactured using a resin composition containing the above-mentioned aliphatic polyester resin. The resin composition used in the first step is not particularly limited as long as it contains the above-mentioned aliphatic polyester resin and can manufacture a cylindrical straw body containing the above-mentioned aliphatic polyester resin.

[0028] In a preferred embodiment, the resin composition contains a P3HA resin as an aliphatic polyester resin. In this embodiment, the resin composition may contain a second P3HA resin in addition to the P3HA resin. The second P3HA resin contains at least one copolymer of a 3HB unit and another hydroxyalkanoate unit, and the 3HB unit in the poly(3-hydroxyalkanoate) resin is preferably 65.0 to 90.0 mol%, more preferably 68.0 to 88.0 mol%, and even more preferably 70.0 to 85.0 mol% of all repeating units (100 mol%). When the resin composition further contains the second P3HA resin, the toughness of the straw body, which is a molded product, is excellent.

[0029] The second P3HA resin is not particularly limited as long as it is different from the above P3HA resin. Examples of the second P3HA resin include the resins exemplified as the above P3HA resin.

[0030] The content of the second P3HA resin is not particularly limited, but is preferably 50 parts by weight or less, more preferably 45 parts by weight or less, and even more preferably 40 parts by weight or less, relative to 100 parts by weight of the total P3HA resin. The lower limit of the content of the second P3HA resin is not particularly limited, and may be 0 parts by weight. The above-mentioned P3HA resin can be used as the second P3HA resin. In this specification, the term "total P3HA resin" refers to all P3HA resins contained in the resin composition in the present production method.

[0031] The resin composition may contain other resins besides the P3HA resin, so long as the effect of the present invention is not impaired. Examples of such other resins include aliphatic polyester resins such as polybutylene succinate adipate, polybutylene succinate, polycaprolactone, and polylactic acid, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate, polybutylene sebate terephthalate, and polybutylene azelate terephthalate. Only one type of other resin may be contained, or two or more types may be contained.

[0032] The content of the other resin is not particularly limited, but is preferably 50 parts by weight or less, more preferably 40 parts by weight or less, and even more preferably 30 parts by weight or less, relative to 100 parts by weight of the total P3HA resin. The lower limit of the content of the other resin is not particularly limited, and may be 0 parts by weight.

[0033] The resin composition does not need to contain an inorganic filler, but preferably further contains an inorganic filler. By containing an inorganic filler in the resin composition, the crystallization speed is improved, and effects such as reducing burrs and improving the production cycle are achieved.

[0034] The inorganic filler is not particularly limited, but examples thereof include talc, diatomaceous earth, white clay, clay, calcium carbonate, manganese carbonate, magnesium carbonate, barium sulfate, mica, silica, alumina, zircon, iron oxide, zinc oxide, titanium oxide, silicon nitride, boron nitride, aluminum nitride, silicon carbide, graphite, carbon black, ferrite, graphite, quartz, glass fiber, glass particles, etc. These may be used alone or in combination of two or more kinds.

[0035] The content of the inorganic filler is, for example, 0 to 60 parts by weight, preferably 5 to 50 parts by weight, more preferably 10 to 40 parts by weight, and particularly preferably 15 to 35 parts by weight, based on 100 parts by weight of the total P3HA resin. When the content of the inorganic filler is within the above range, both a sufficient crystallization rate and toughness can be achieved.

[0036] The resin composition may contain additives that can be used together with the P3HA resin, as long as they do not impair the effects of the present invention. Examples of such additives include colorants such as pigments and dyes, odor absorbents such as activated carbon and zeolite, fragrances such as vanillin and dextrin, plasticizers, antioxidants, weather resistance improvers, ultraviolet absorbers, crystal nucleating agents, lubricants, release agents, water repellents, antibacterial agents, and sliding property improvers. Only one type of additive may be contained, or two or more types may be contained. The content of these additives can be appropriately set by those skilled in the art depending on the purpose of use.

[0037] In addition, in the first step, the method for manufacturing the tubular straw body can be a known method as long as it uses a resin composition containing the aliphatic polyester resin described above. For example, the method for manufacturing the straw body includes the following melting step and molding step. A melting step in which a resin composition containing an aliphatic polyester resin is melted in an extruder. After the melting step, the resin composition is extruded from a circular die connected to the outlet of the extruder, poured into water, and solidified to form a tube shape in a molding step.

[0038] (2nd process) In the second step, the end of the straw body manufactured in the first step is heated to form a widened portion at the end. More specifically, the end of the straw body manufactured in the first step is locally heated. Then, a widening mold is inserted into the end softened by the heating to form a widened portion at the end of the straw body.

[0039] It is preferable that the local heating of the end of the straw body is performed by a preheated widening mold, which eliminates the need to provide a separate heating member for locally heating the end of the straw body.

[0040] FIG. 1 is a diagram showing a schematic example of the second step in the present manufacturing method. 101 in FIG. 1 is a cross-sectional view showing the schematic configuration of a straw body 31 used in the second step. 102 to 104 in FIG. 1 are diagrams showing the schematic steps of the second step. 105 in FIG. 1 is a cross-sectional view showing the schematic configuration of a straw 30 manufactured by the second step. As shown in the drawings, in this specification, the length direction (axial direction) of the straw body is referred to as the LD direction, and in the LD direction, one side (front side) is the LDa side, and the other side (rear side) is the LDb side.

[0041] As shown in 101 in Fig. 1, the straw body 31 used in the second step is manufactured in the first step and is tubular, preferably cylindrical. In Fig. 1, 101 to 105, the straw body 31 is cylindrical.

[0042] The straw body 31 may have a thickness that is sufficient for use as a straw, but is preferably 0.30mm to 0.45mm, and more preferably 0.35mm to 0.40mm. The straw body 31 may have an inner diameter that is sufficient for use as a straw, but is preferably 3.0mm to 4.5mm, and more preferably 3.5mm to 4.0mm.

[0043] The second step includes a preparation step indicated by 102 in FIG. 1, a preheating step indicated by 103 in FIG. 1, and a width increasing step indicated by 104 in FIG.

[0044] As shown in 102 of FIG. 1, in the preparation step, the straw body 31 and the widening processing die 10 are prepared. The widening processing die 10 is a die inserted into the end of the straw body 31 on the LDb side, and forms a widening portion at the end. The widening processing die 10 is preheated. The widening processing die 10 also includes a widening forming section 11 and a preheating section 12. The widening forming section 11 is provided on the LDb side with respect to the preheating section 12. The widening forming section 11 and the preheating section 12 are both cylindrical and coaxial with each other. The widening forming section 11 has a smaller diameter than the preheating section 12. The widening forming section 11 and the preheating section 12 form the widening processing die 10 into a two-stage cylindrical shape. The widening forming section 11 is a section that forms a widening portion for the straw body 31, and is a cylindrical shape with a diameter approximately the same as the inner diameter R2 of the widening portion. On the other hand, the preheating section 12 has a cylindrical shape with a diameter substantially the same as the inner diameter R1 of the non-widening section described later, that is, the inner diameter of the straw body 31. In addition, at least the edge portions on the LDa side of the widening molding section 11 and the preheating section 12 are chamfered so that the widening processing mold 10 can be inserted without damaging the inner surface of the straw body 31.

[0045] As shown in 103 of FIG. 1, in the preheating step, the preheating section 12 is inserted into the end of the straw body 31 on the LDb side. At this time, it is preferable to insert the preheating section 12 into the end of the straw body 31 on the LDb side by pushing the straw body 31 into the widening processing die 10 rather than pushing the widening processing die 10 into the straw body 30. In the preheating step, the preheating section 12 is inserted into the straw body 31 in the widening processing die 10, and the widening forming section 11 is not inserted into the straw body 31. Therefore, in the preheating step, the end of the straw body 31 on the LDb side is not widened. In the preheating step, the end of the straw body 31 on the LDb side is locally preheated. In this way, a preheating step is performed to locally preheat the end of the straw body 31 in the second step of forming the widening section in the straw body 31. This preheating process has the following advantages: (1) when inserting the widening processing mold 10 into the straw body 31, the force required to press the straw body 31 into the widening processing mold 10 can be reduced, and (2) whitening of the widening portion formed in the straw body 31 can be suppressed.

[0046] In addition, P3HA resin has a lower thermal conductivity than polypropylene resin, which is commonly used as a raw material for the straw body 30. Therefore, when the raw material for the straw body 30 is polypropylene resin, it is possible to form the widened portion without carrying out the preheating process. On the other hand, when the raw material for the straw body 30 is P3HA resin, it is effective to carry out the preheating process from the viewpoint of ease of processing the widened portion. Therefore, the preheating process is a process suitable for forming a widened portion in a straw body made of P3HA resin.

[0047] The preheating temperature t' (°C) of the end of the straw body 31 in the preheating step is not particularly limited and can be set appropriately according to the heating temperature t (°C) of the straw body 31 in the widening step described below. For example, the preheating temperature t' (°C) is preferably the heating temperature t (°C) ±30°C, and more preferably the same as the heating temperature t (°C). By having the preheating temperature t' (°C) within the above range, it is possible to reduce the force required to press the straw body 31 into the widening mold 10 when inserting the widening mold 10 into the straw body 31.

[0048] The preheating time s' in the preheating step is not particularly limited, but is preferably 0.1 to 1.0 seconds, and more preferably 0.3 to 0.8 seconds. The preheating time s' in the above range prevents excessive heating and suppresses deformation of the widened portion. For example, the preheating time s' is 0.5 seconds.

[0049] In this manufacturing method, the widening process is performed after the preheating process. As shown in 104 of FIG. 1, in the widening process, the widening molding part 11 is inserted into the end of the straw body 31 on the LDb side. In the widening process, both the widening molding part 11 and the preheating part 12 are inserted into the straw body 31 in the widening processing die 10. In the widening process, it is preferable to insert the widening molding part 11 into the end of the straw body 31 on the LDb side by pushing the straw body 31 into the widening processing die 10 rather than pushing the widening processing die 10 into the straw body 30. That is, it is preferable to move the straw body 31 further toward the LDb side from the state in which only the preheating part 12 is inserted into the end of the straw body 31 (the state of the preheating process). Then, the widening molding part 11 is brought into contact with the part preheated by the preheating part 12 at the end of the straw body 31. As a result, the end of the straw body 31 on the LDb side is locally heated and softened through preheating in the preheating process. Then, the end of the straw body 31 is molded along the two-stage cylindrical shape of the widening processing die 10. As a result, the widening portion 32 is formed at the end of the straw body 31 on the LDb side.

[0050] After the above-mentioned widening step, the widening processing die 10 is completely removed from the straw body 31, and the straw body 31 is cooled. This cooling produces a straw 30 with a widened portion 32 formed at the end on the LDb side.

[0051] As shown in 105 of FIG. 1, the straw 30 manufactured by the second step has a configuration including a widening portion 32 and a non-widening portion 33. In the straw body 31 (straw 30), the widening portion 32 corresponds to the portion widened by the widening molding portion 11, and the non-widening portion 33 corresponds to the portion other than the widening portion 32 that is not widened. In this manufacturing method, the ratio (R2 / R3) of the inner diameter R2 of the widening portion 32 to the inner diameter R3 of the non-widening portion is not particularly limited, but is preferably 1.1 to 1.3, and more preferably 1.23 to 1.28. By having the ratio of the inner diameter R2 to the inner diameter R3 within the above range, the effect of strengthening the hook between the straw 30 and the outer straw when assembling an extendable straw with the straw 30 as the inner straw while maintaining the rigidity of the widening portion 32 is achieved.

[0052] In addition, in this manufacturing method, the ratio of the inner diameter R2 to the inner diameter R3 can be controlled, for example, by setting the ratio of the diameter of the widening molding part 11 of the widening processing die 10 to the inner diameter of the straw body 31. As described above, in the widening processing die 10, the preheating part 12 is approximately the same as the inner diameter of the straw body 31, so the ratio of the inner diameter R2 to the inner diameter R3 can also be controlled by setting the ratio of the diameter of the widening molding part 11 to the preheating part 12.

[0053] (Heating temperature t (℃) of the end of the straw body 31 in the second step) Here, this manufacturing method is characterized by the setting conditions for the heating temperature t (°C) for the end of the straw body 31 when forming the widening portion 32 at the end of the straw body 31 as described above. When the second process shown in 102 to 104 in Fig. 1 is included, this manufacturing method is characterized by the setting conditions for the heating temperature t (°C) for the end of the straw body 31 in the widening process shown in 104 in Fig. 1. The heating temperature t (°C) for the end of the straw body 31 can be controlled by adjusting the heating temperature of the widening processing mold 10.

[0054] In the second step of the present production method, the heating temperature t (°C) is expressed by the following formula (1): 0.50≦ΔH t / ΔH total≦0.791 (1) ΔH t : In the differential scanning calorimetry analysis of the straw body 31, the enthalpy of crystalline fusion from t (℃) to the total crystalline fusion temperature (℃) ΔH total : Total crystalline melting enthalpy from 20°C to the total crystalline melting temperature (°C) in differential scanning calorimetry of the fully crystallized straw body 31 Meet the following.

[0055] In this manufacturing method, ΔH total is the total crystal fusion enthalpy of the fully crystallized straw body 31, and is a value determined according to the fully crystallized conditions of the straw body 31. On the other hand, ΔH t is the crystalline melting enthalpy of the straw body 31 used in this manufacturing method, and is not a value that is determined according to the complete crystallization conditions of the straw body 31. When an aliphatic polyester resin such as P3HA resin is used as the raw material, the straw body 31 gradually crystallizes over, for example, one week after molding. In this manufacturing method, the straw body 31 to be widened may be in the middle of crystallization or may be completely crystallized. Therefore, in this manufacturing method, ΔH t of the sample to be measured and ΔH total The measurement target samples may be different from each other or may be the same.

[0056] Since the heating temperature t (°C) is set to satisfy the above formula (1), it has the effect of providing excellent processability for the non-widened portion 33. Specifically, it has the effects of (1) preventing the whitening phenomenon of the widened portion 32, and (2) preventing the widened portion 32 from cracking.

[0057] FIG. 2 shows an example of a DSC curve obtained by differential scanning calorimetry of the straw body 31. t and ΔH total2 is a graph for explaining the above. In the graph shown in FIG. 2, the total crystal melting temperature is indicated as t1. Note that FIG. 2 shows the case where a completely crystallized straw body 31 is subjected to differential scanning calorimetry. In the following, ΔH t of the sample to be measured and ΔH total The case where the sample to be measured is the same as the sample to be measured will be described.

[0058] In this specification, the "total crystal melting temperature t1" is defined as follows. A sample of 1 to 5 mg of the straw body 31 is heated from -30°C to 180°C at a rate of 10°C / min using a differential scanning calorimeter to melt the sample of the straw body 31 and obtain an endothermic curve. In the obtained endothermic curve, for the melting point peaks present in the range of 20°C to 180°C, the melting point peak temperature at which the amount of endothermic heat becomes maximum is defined as Tm, and the temperature at which endothermic heat is no longer observed is defined as the total crystal melting temperature t1. If there is another melting point peak on the higher temperature side than Tm, the temperature at which that endothermic heat is no longer observed is defined as the total crystal melting temperature t1.

[0059] First, ΔH total That is, the total crystalline melting entropy is calculated from all melting peaks in differential scanning calorimetry measured on the fully crystallized straw body. The total crystalline melting enthalpy calculated from all melting peaks refers to the sum of each crystalline melting enthalpy. Specifically, for example, in the DSC curve shown in FIG. 2, a straight line is drawn between the baselines before the start of melting and after the end of melting, and the total crystalline melting enthalpy is calculated as the area of ​​the melting region (hatched region in FIG. 2) surrounded by the straight line and the DSC curve. The straight line is a straight line connecting the heat flow at 20°C and the heat flow at the total crystalline melting temperature t1.

[0060] ΔH t is the crystalline melting enthalpy from t (°C) to the total crystalline melting temperature t1 (°C) in the differential scanning calorimetry of the straw body 31. t is calculated as the area of ​​the region from the heating temperature t to the total crystal melting temperature t1 in the melting region above, which shows the total crystal melting entropy. ΔH tis the area of ​​the region from the heating temperature t to the total crystal melting temperature t1 in the shaded region in FIG. 2, for example.

[0061] In this manufacturing method, ΔH total ΔH t Ratio of (ΔH t / ΔH total ) is in the range of 0.50 to 0.791, and preferably in the range of 0.573 to 0.612.

[0062] It is preferable that the present manufacturing method further includes a curing step in which the straw body 31 manufactured in the first step is stored under predetermined curing conditions (curing time, curing temperature, etc.) until the second step. ΔH t The DSC curve used to calculate ΔH changes depending on, for example, the curing time of the straw body 31 in the curing process. t The value of can be controlled by adjusting the heating temperature t and the curing time. The longer the curing time, the higher the elastic modulus tends to be.

[0063] On the other hand, ΔH total As described above, the value of ΔH is determined according to the complete crystallization conditions of the straw body 31. total The value of cannot be controlled by adjusting the heating temperature t and the curing time. When an aliphatic polyester resin such as P3HA resin is used as the raw material, the straw body 31 gradually crystallizes over, for example, one week after molding. In this case, it is calculated based on the DSC curve obtained from the differential scanning calorimetry of the straw body 31 after curing for one week (7 days).

[0064] The above curing time is ΔH total ΔH t Ratio (ΔH t / ΔH total ) is not particularly limited as long as it is possible to set it in the above-mentioned numerical range, but it is preferably 10 minutes to 2 weeks, and more preferably 2 hours to 4 days. In addition, the above-mentioned curing temperature is total ΔH t Ratio (ΔH t / ΔH total) is not particularly limited as long as it can be within the above-mentioned numerical range, but is preferably 60°C to 130°C, and more preferably 80°C to 125°C.

[0065] In addition, in this manufacturing method, ΔH total ΔH t Ratio (ΔH t / ΔH total ) can be within the above-mentioned numerical range, the heating temperature t and the curing time can be set arbitrarily. In this manufacturing method, the heating temperature t and the curing time are, for example, (i) for a curing time of 10 minutes to 12 hours, the heating temperature t is 50°C to 120°C, (ii) for a curing time of more than 12 hours and 4 days or less, the heating temperature t is 80°C to 120°C, and (iii) for a curing time of more than 4 days and 2 weeks or less, the heating temperature t is 85°C to 110°C.

[0066] More specifically, for a curing time of 2 hours, the heating temperature t is 60°C to 110°C. For a curing time of 3 days, the heating temperature t is 80°C to 110°C. For a curing time of 7 days (1 week), the heating temperature t is 85°C to 100°C.

[0067] When the aliphatic polyester resin is a P3HA resin, ΔH total and ΔH t The DSC curve used to calculate ΔH varies depending on, for example, the average content ratio of other hydroxyalkanoate units in all monomer units constituting the P3HA resin component of the resin composition used in the first step. total and ΔH t The value of can also be controlled by adjusting the average content ratio and the heating temperature t.

[0068] (Method of manufacturing the extendable straw according to this embodiment) The manufacturing method of the extendable straw according to the present embodiment includes the above-mentioned present manufacturing method as one step. The manufacturing method of the extendable straw according to the present embodiment can be a conventionally known method as long as it is a method for manufacturing an extendable straw using the straw 30 manufactured by the present manufacturing method.

[0069] 301 and 302 in Fig. 3 are diagrams showing an example of a method for manufacturing the extendable straw S according to this embodiment. The method for manufacturing the extendable straw according to this embodiment includes a preparation step shown in 301 in Fig. 3 and an assembly step shown in 302 in Fig. 3.

[0070] As shown in 301 of Fig. 3, in the preparation step, the straw 30 manufactured by the present manufacturing method and the straw 40 are prepared. In the extendable straw S, the straw 30 corresponds to a small-diameter inner straw having a widened portion 32 at the end on the LDb side, where the diameter is widened. The straw 40 corresponds to a large-diameter outer straw having a narrowed portion 43 at the end on the LDa side, where the diameter is narrowed (see 302 of Fig. 3).

[0071] The straw 40 has a non-reduced width portion 42 and a reduced width portion 43. The inner diameter of the non-reduced width portion 42 is larger than the inner diameter of the reduced width portion 43 and the inner diameter of the widened width portion 32 of the straw 30. The inner diameter of the reduced width portion 43 is smaller than the inner diameter of the non-reduced width portion 42 and larger than the inner diameter of the non-widened width portion 33 of the straw 30. The straw 40 can be manufactured by a conventionally known method applied to the manufacturing method of the extendable straw S. For example, the straw 40 can be manufactured by a method similar to this manufacturing method for a straw body having the inner diameter of the reduced width portion 43. That is, a widening processing mold having a preheating portion with the same diameter as the diameter of the reduced width portion 43 and a widening forming portion with the same diameter as the diameter of the non-reduced width portion 42 is prepared, and the widening processing mold is used to form a widened width portion (corresponding to the non-reduced width portion 42) at the end portion on the LDb side of the straw body having the inner diameter of the reduced width portion 43 by a method similar to this manufacturing method.

[0072] As shown in 302 of FIG. 3, in the assembly process, the straw 30 is inserted into the end of the straw 40 on the LDa side to manufacture the extendable straw S. In the assembly process, the straw 30 is inserted from the end of the straw 40 on the LDa side so that the widening portion 32 contacts the inner surface of the non-reduced width portion 42 and the non-widening portion 33 contacts the inner surface of the reduced width portion 43. As a result, when the straw 30 is moved toward the LDa side to lengthen the extendable straw S, the step between the widening portion 32 and the non-widening portion 33 is engaged with the step between the non-reduced width portion 42 and the reduced width portion 43. As a result, the straw 30 does not slip out of the straw 40.

[0073] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0074] That is, one embodiment of the present invention is as follows.

[0075] <1> A first step of manufacturing a cylindrical straw body 31 using a resin composition containing an aliphatic polyester resin; A second step of heating the end of the straw body 31 to form a widened portion 32 at the end, In the second step, the heating temperature t (°C) of the end of the straw body 31 is calculated by the following formula (1): 0.50≦ΔH t / ΔH total ≦0.791 (1) ΔH t : In the differential scanning calorimetry analysis of the straw body 31, the crystalline melting enthalpy from t (℃) to the total crystalline melting temperature (℃) ΔH total : Total crystalline melting enthalpy from 20°C to the total crystalline melting temperature (°C) in differential scanning calorimetry of the fully crystallized straw body 31 A method for manufacturing a straw 30 that satisfies the above requirements.

[0076] <2> The aliphatic polyester resin is a poly(3-hydroxyalkanoate) resin. <1> A method for manufacturing straws 30.

[0077] <3> In the straw 30, when the portion other than the widened portion 32 that is not widened is defined as a non-widened portion 33, the ratio of the inner diameter R2 of the widened portion 32 to the inner diameter R3 of the non-widened portion 33 is 1.1 to 1.3. <1> or <2> A method for manufacturing straws 30.

[0078] <4> <1> ~ <3> A method for manufacturing an extendable straw S, comprising any one of the above manufacturing methods for a straw 30 as one step. EXAMPLES

[0079] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0080] The substances used in the examples and comparative examples are shown below.

[0081] [Poly(3-hydroxyalkanoate) resin] PHB: Poly(3-hydroxybutyrate) (weight average molecular weight is 300,000 g / mol) It was produced according to the method described in Comparative Example 1 of WO 2004 / 041936. PHB: Poly(3-hydroxybutyrate) (weight average molecular weight is 300,000 g / mol) It was produced according to the method described in Comparative Example 1 of WO 2004 / 041936. P3HB3HH-3: P3HB3HH (average content ratio 3HB / 3HH = 97.1 / 2.9 (mol% / mol%), weight average molecular weight is 300,000 g / mol) It was produced in accordance with the method described in Example 2 of WO 2019 / 142845. P3HB3HH-13: P3HB3HH (Kaneka Biodegradable Polymer PHBH (registered trademark)) (average content ratio 3HB / 3HH = 87.1 / 12.9 (mol% / mol%), weight average molecular weight is 330,000 g / mol) P3HB3HH-30: P3HB3HH (average content ratio 3HB / 3HH = 70.5 / 29.5 (mol% / mol%), weight average molecular weight is 640,000 g / mol) It was produced in accordance with the method described in Example 9 of WO 2019 / 142845.

[0082] [Additives] Additive-1: Behenamide (Nippon Fine Chemicals: BNT-22H) Additive-2: Erucamide (Neutron-S, manufactured by Nippon Fine Chemical Industries, Ltd.).

[0083] [Plasticizer] Plasticizer: Glycerin diacetomonolaurate (BIOCIZER, manufactured by Riken Vitamin Co., Ltd.).

[0084] 1. Preparation of Resin Composition Pellets A blend of 12.0 parts by weight of PHB, 52.2 parts by weight of P3HB3HH-3, 22.8 parts by weight of P3HB3HH-30, and 13.0 parts by weight of P3HB3HH-13 was further blended with 1.0 part by weight of additive-1, 0.5 part by weight of additive-2, and 4.3 parts by weight of a plasticizer.

[0085] The obtained resin material (resin mixture) was fed into a φ26 mm co-rotating twin-screw extruder with the cylinder temperature and die temperature both set at 150° C., and strands of the resin material were extruded at 20 kg / hour. The extruded resin material was passed through a water tank filled with hot water at 40° C. to solidify the strands, and cut with a pelletizer to obtain resin composition pellets.

[0086] 2. Forming the tube (straw body) (first step) The cylinder temperature and die temperature of a φ50 mm single-screw extruder connected to an annular die (outer diameter 15 mm, inner diameter 13.5 mm) were set to 160°C, and resin pellets were added and extruded into a tube. The extruded tube was passed through a 40°C water bath located 100 mm away from the annular die and taken up at a speed of 25 m / min. As a result, a tube with a wall thickness of 0.25 mm, an outer diameter of 5.5 mm, and a length of 100 mm was obtained. The tube thus obtained was then cured to form a straw body. Straw bodies cured for 2 hours, 3 days, and 7 days were prepared.

[0087] 3. Processing the widened section (second process) To process the widening portion, a widening processing die having a preheated portion with an outer diameter of 5 mm and a widening forming portion with an outer diameter of 6.2 mm was used (see Figure 1). The widening processing die was preheated to a predetermined temperature (heating temperature t°C). The edges of the widening forming portion and the preheated portion were chamfered so that the widening processing die could be inserted without damaging the inner surface of the straw body.

[0088] Preheating process: The preheating part of the widening processing mold was inserted into the end of the straw body manufactured in step 2, and the end of the straw body was preheated for 0.5 seconds.

[0089] Widening process: The widening processing mold was pressed further in, bringing the widening molding part into contact with the end of the straw body, and this was held for 1 second.

[0090] After the widening process, the widening processing mold was completely removed from the straw body 31, and a widened portion was formed at the end of the straw body.

[0091] The evaluation methods used in the examples and comparative examples are described below.

[0092] [Measurement of melting peak temperature and crystal melting enthalpy in differential scanning calorimetry: ΔH t / ΔH total Calculation of The straw body samples were prepared by weighing approximately 2 mg of each straw body prepared at each curing time. The measured samples were then heated from -30°C to 180°C at a heating rate of 10°C / min using a differential scanning calorimeter (TA Instruments, DSC25 model), and the crystalline melting enthalpy was calculated from the DSC curve obtained when the samples were heated from -30°C to 180°C.

[0093] In the DSC curve obtained by performing differential scanning calorimetry on a straw body sample that had been cured for 7 days, the crystalline melting enthalpy from 20°C to the total crystalline melting temperature was calculated as the total crystalline melting enthalpy ΔH total The heat energy was calculated as (J / g).

[0094] In the DSC curve obtained by performing differential scanning calorimetry on the straw body samples prepared for each curing time, the crystalline melting enthalpy from the heating temperature t℃ to the total crystalline melting temperature is calculated as the crystalline melting enthalpy ΔH t The heat energy was calculated as (J / g).

[0095] And the total crystal fusion enthalpy ΔH obtained total and the enthalpy of crystal fusion ΔH t (J / g), ΔH t / ΔH total was calculated.

[0096] [Evaluation of workability of widened section] The widened portion formed in step 3 was observed to evaluate its workability. The evaluation criteria for the workability of the widened portion were as follows: "Whitening": Whitening is observed in the widened area. "Crack": Cracks are observed in the widened area. "Moldable": The widening is molded without whitening or splitting.

[0097] Example 1 The tube prepared in 2. above was used as the straw body after curing for 2 hours. The heating temperature t of the widening processing die was set to 110°C, and the widened part was processed according to 3. above, and the workability of the widened part was evaluated. Differential scanning calorimetry was also performed on the straw body, and ΔH t / ΔH total was calculated.

[0098] ΔH of straw body t / ΔH total The evaluation results of the workability of the widened portion are shown in Table 1.

[0099] (Examples 2 to 14) The straw body was processed in the same manner as in Example 1, except that the curing time of the tube produced in 2 and the heating temperature t of the widening processing mold were set to the conditions shown in Table 1. Differential scanning calorimetry was performed on each of the straw bodies of Examples 2 to 14, and ΔH t / ΔH total was calculated.

[0100] ΔH of straw body t / ΔH total The evaluation results of the workability of the widened portion are shown in Table 1.

[0101] (Comparative Examples 1 to 14) The widened portion of the straw body was processed in the same manner as in Example 1, except that the curing time of the tube produced in 2 and the heating temperature t of the widening processing mold were set to the conditions shown in Table 2. Differential scanning calorimetry was performed on each of the straw bodies of Comparative Examples 1 to 14, and ΔH t / ΔH total was calculated.

[0102] ΔH of straw body t / ΔH total The evaluation results of the workability of the widened portion are shown in Table 2.

[0103] [Table 1]

[0104] [Table 2]

[0105] From the results in Tables 1 and 2, the ΔH t / ΔH total It was found that when the ratio is 0.50 to 0.791, the widened portion can be formed without any problems in workability. [Industrial Applicability]

[0106] The present invention can be used in the field of straw manufacturing. [Explanation of symbols]

[0107] 30 Straws 31 Straw body 32 Widening section 33 Non-widening section S Extendable Straw

Claims

1. A first step of producing a cylindrical straw body using a resin composition containing an aliphatic polyester resin; A second step of heating the end of the straw body to form a widened portion at the end, In the second step, the heating temperature t (°C) of the end of the straw body is calculated based on the following formula (1): 0.50≦ΔH ｔ / ΔH ｔｏｔａｌ ≦0.791 (1) ΔH ｔ : In the differential scanning calorimetry analysis of the straw body, the crystalline melting enthalpy from t (°C) to the total crystalline melting temperature (°C) ΔH ｔｏｔａｌ : Total crystalline melting enthalpy from 20°C to the total crystalline melting temperature (°C) in differential scanning calorimetry of a fully crystallized straw body A method for manufacturing straws that satisfies the above requirements.

2. The method for producing a straw according to claim 1, wherein the aliphatic polyester resin is a poly(3-hydroxyalkanoate) resin.

3. In the straw, when the portion other than the widened portion that is not widened is defined as the non-widened portion, The method for manufacturing a straw according to claim 1 or 2, wherein the ratio of the inner diameter of the widened portion to the inner diameter of the non-widened portion is 1.1 to 1.

3.

4. A method for producing an extendable straw, comprising the method for producing the straw according to claim 1 or 2 as one step.

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