Method for producing polybutylene succinate-based resin foam sheet, polybutylene succinate-based resin foam sheet, and cushioning material for packing

Abstract

To provide a method for producing a polybutylene succinate-based resin foam sheet which can produce a polybutylene succinate-based resin foam sheet corresponding to a wide-range density condition, and can produce a polybutylene succinate-based resin foam sheet that prevents lowering of cushioning performance.SOLUTION: There is provided a method for producing a polybutylene succinate-based resin foam sheet by extruding and foaming a foamable resin molten material obtained by kneading a polybutylene succinate-based resin and a physical foaming agent, wherein an addition amount of the physical foaming agent is 0.2 mol or more and 2 mol or less per 1 kg of a resin component constituting the foamable resin molten material, the physical foaming agent contains 90 mol% or more of a component (provided that total amount of dialkyl ether and carbon dioxide is 100 mol%) composed of 10 mol% to 100 mol% of dialkyl ether having a C1-3 alkyl group and 0 mol% to 90 mol% of carbon dioxide, and an addition amount of the dialkyl ether is 0.1 mol% or more per 1 kg of the resin component constituting the foamable resin molten material.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a polybutylene succinate-based resin foamed sheet, a polybutylene succinate-based resin foamed sheet, and a cushioning material for packaging using the polybutylene succinate-based resin foamed sheet. [Background technology]

[0002] From the viewpoint of reducing the environmental load, it is expected that polybutylene succinate-based resin, which is a biodegradable resin, can be used to produce foamed sheets applicable in various industrial fields such as packaging cushioning materials. As shown in Patent Documents 1 and 2, a method for producing a polybutylene succinate-based resin foamed sheet has been proposed in which a foamable resin melt obtained by kneading a polybutylene succinate-based resin and butane as a physical foaming agent is extruded and foamed to produce a polybutylene succinate-based resin foamed sheet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-211294 A [Patent Document 2] JP 2020-164686 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the method of producing a polybutylene succinate-based resin foamed sheet using butane as a physical foaming agent as shown in Patent Documents 1 and 2, when the amount of butane added is increased to produce a foamed sheet having a lower density, it is difficult to produce a good polybutylene succinate-based resin foamed sheet. Therefore, the method of producing a polybutylene succinate-based resin foamed sheet is required to be improved from the viewpoint of making it possible to produce a polybutylene succinate-based resin foamed sheet under a wide range of density conditions. Furthermore, in the method of producing a polybutylene succinate-based resin foamed sheet using butane as a physical foaming agent, the cushioning performance of the polybutylene succinate-based resin foamed sheet is easily reduced, and there is room for improvement in this respect.

[0005] One object of the present invention is to provide a method for producing a polybutylene succinate-based resin foamed sheet, which enables the production of a polybutylene succinate-based resin foamed sheet under a wide range of density conditions and which is resistant to deterioration in cushioning performance, a polybutylene succinate-based resin foamed sheet produced using the method, and a packaging cushioning material using the polybutylene succinate-based resin foamed sheet. [Means for solving the problem]

[0006] The present invention relates to the following aspects (1) to (7).

[0007] (1) A method for producing a polybutylene succinate-based resin foamed sheet by extruding and foaming a foamable resin melt obtained by kneading a polybutylene succinate-based resin and a physical foaming agent, comprising the steps of: the amount of the physical foaming agent added is 0.2 mol or more and 2 mol or less per 1 kg of a resin component constituting the foamable resin molten material, The physical foaming agent contains 90 mol % or more of a component consisting of 10 mol % to 100 mol % of a dialkyl ether having an alkyl group with 1 to 3 carbon atoms and 0 mol % to 90 mol % of carbon dioxide (wherein the total amount of the dialkyl ether and the carbon dioxide is 100 mol %), The amount of the dialkyl ether added is 0.1 mol or more per 1 kg of the resin component constituting the foamable resin melt. A method for producing a polybutylene succinate resin foam sheet. (2) The physical foaming agent does not contain a saturated hydrocarbon having 3 to 6 carbon atoms, or The physical foaming agent contains a saturated hydrocarbon having a carbon number of 3 to 6, and the amount of the saturated hydrocarbon added is 0.2 mol or less per 1 kg of a resin component constituting the foamable resin molten material. A method for producing the polybutylene succinate resin foam sheet according to the above (1). (3) The biomass content of the polybutylene succinate resin is 30% or more; The flexural modulus of the polybutylene succinate resin is 100 MPa or more and 1000 MPa or less. A method for producing the polybutylene succinate resin foamed sheet according to the above (1) or (2). (4) The density of the polybutylene succinate resin foam sheet is 30 kg / m 3 More than 200kg / m 3 Below is the A method for producing a polybutylene succinate resin foamed sheet according to any one of the above (1) to (3). (5) Density is 30 kg / m 3 More than 200kg / m 3 A polybutylene succinate-based resin foam sheet comprising: The polybutylene succinate-based resin foam sheet has an average bubble diameter in a thickness direction of 0.5 mm or more and 1.5 mm or less, The polybutylene succinate-based resin foamed sheet has a closed cell rate of 30% or more. (6) The polybutylene succinate-based resin foamed sheet according to the above (5), wherein the content of saturated hydrocarbons having 3 to 6 carbon atoms in the polybutylene succinate-based resin foamed sheet is 0.2 mol or less (including 0) per 1 kg of the polybutylene succinate-based resin foamed sheet. (7) A packaging cushioning material comprising the polybutylene succinate-based resin foam sheet according to (5) or (6), The polybutylene succinate resin foam sheet has a compression set of 5% or less as measured in accordance with JIS K 6767:1999. Effect of the Invention

[0008] According to the present invention, it is possible to provide a method for producing a polybutylene succinate-based resin foamed sheet that can produce a polybutylene succinate-based resin foamed sheet that is compatible with a wide range of density conditions and that is resistant to deterioration in cushioning performance, a polybutylene succinate-based resin foamed sheet produced using the method, and a packaging cushioning material using the polybutylene succinate-based resin foamed sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An example of an embodiment of the present invention will be described below. Note that the present invention is not limited to the embodiment described below.

[0010] [1. Manufacturing method of polybutylene succinate resin foam sheet] [1-1 Configuration] The manufacturing method according to the present invention is a method for manufacturing a foamed sheet by using an extrusion foaming method. Specifically, the manufacturing method according to the present invention is a method for manufacturing a polybutylene succinate-based resin foamed sheet by extrusion foaming a foamable resin melt containing a polybutylene succinate-based resin and a physical foaming agent. In this specification, the polybutylene succinate-based resin is referred to as a PBS-based resin, and the polybutylene succinate-based resin foamed sheet is referred to as a PBS-based resin foamed sheet. The PBS-based resin foamed sheet may also be simply referred to as a foamed sheet.

[0011] (Extruder) As the extruder used to carry out the extrusion foaming method, a general manufacturing apparatus for manufacturing an extruded foam sheet can be used. As an example, a tandem extruder, which is an extruder in which a first extruder and a second extruder are connected in series, is used as the manufacturing apparatus. In the tandem extruder, the first extruder is disposed on the upstream side, and the second extruder is disposed on the downstream side. A die for discharging the foamable resin melt is provided downstream of the second extruder in the manufacturing apparatus. For example, an annular die is connected as the die. Here, the description will be continued using the example of a manufacturing apparatus equipped with an annular die downstream of the second extruder. It is preferable that the manufacturing apparatus is provided with a mandrel, which is a cooling cylinder for cooling the cylindrical foam, downstream of the annular die, and a cutter for cutting the cylindrical foam that has been extruded and cooled into a sheet foam. In addition, it is preferable that the manufacturing apparatus is provided with a winder that takes up the cut-open sheet foam in a roll shape. The upstream side and the downstream side are determined based on the transport direction of the PBS resin that is the raw material resin of the foam sheet. Moreover, the manufacturing apparatus shown here is merely an example and is not limited to this.

[0012] (Extrusion foaming) A raw resin is fed to a first extruder, additives are added as necessary, and a physical foaming agent is further fed, and these are melt-kneaded to obtain a foamable resin melt. The obtained foamable resin melt is transferred to a second extruder, where it is adjusted to a predetermined temperature. The foamable resin melt is extruded from the annular die of the second extruder under a pressure atmosphere (usually atmospheric pressure) lower than the pressure inside the extruder, and foams at the same time, to obtain a cylindrical foam. This cylindrical foam is taken up along a mandrel, and cut into a sheet shape by a cutter or the like provided downstream of the mandrel, to form a sheet foam, which is a PBS-based resin foam sheet. The sheet foam is wound into a roll by a winder.

[0013] In the above description, an example was given in which the production apparatus was equipped with an annular die, but the die may be a T-die, and a foam sheet can also be produced by extrusion foaming from a T-die. In addition, a case was described in which a cylindrical foam aligned along a mandrel was cut to produce a sheet-like foam, but a sheet-like foam may also be produced by crushing a cylindrical foam formed using an annular die in the radial direction of the cylindrical foam and fusing the inner surfaces of the cylindrical foam together to form a sheet.

[0014] (Foamable resin melt) The above-mentioned foamable resin melt contains a PBS-based resin as a raw material resin and a physical foaming agent.

[0015] (PBS-based resin) The PBS-based resin is a polymer obtained by polycondensation of a dicarboxylic acid containing succinic acid and a diol containing butanediol. The PBS-based resin is configured so that the total of a component derived from succinic acid and a component derived from butanediol is the main component. Specifically, the total ratio of the component derived from succinic acid and the component derived from butanediol in the PBS-based resin is 50% by mass or more. Note that the PBS-based resin may contain a component derived from a compound other than succinic acid and butanediol, so long as the total of the component derived from succinic acid and the component derived from butanediol is the main component. Examples of the other compounds include monocarboxylic acids such as lactic acid, glycolic acid, and 2-hydroxybutyric acid, dicarboxylic acids such as glutaric acid, adipic acid, pimelic acid, azelaic acid, and sebacic acid, and diols such as ethylene glycol, diethylene glycol, propylene glycol, 2-methyl-1,3-pentanediol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol.

[0016] When the PBS-based resin contains a component derived from another compound, the ratio of the component derived from the other compound is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, based on 100 parts by weight of the total of the component derived from succinic acid and the component derived from butanediol. In addition, from the viewpoint of stably increasing the cushioning performance of the PBS-based resin foamed sheet and from the viewpoint of more easily suppressing the decrease in the cushioning performance of the PBS-based resin foamed sheet, it is preferable that the PBS-based resin does not substantially contain a component derived from an aromatic dicarboxylic acid. More specifically, the ratio of the component derived from an aromatic dicarboxylic acid in the PBS-based resin is preferably 5 parts by mass or less (including 0) based on 100 parts by weight of the total of the component derived from succinic acid and the component derived from butanediol. Examples of aromatic dicarboxylic acids include terephthalic acid and the like.

[0017] (Biomass ratio) From the viewpoint of reducing the environmental load, it is preferable that the monomer constituting the PBS-based resin contains a biological (biomass) component. From this viewpoint, the PBS-based resin preferably has a biomass ratio of 30% or more, more preferably 40% or more, and even more preferably 50% or more.

[0018] The biomass content (%) of PBS-based resin is calculated based on the radioactive carbon (C) content of PBS-based resin in accordance with ASTM D 6866. 14 It can be identified by measuring the concentration of

[0019] (Flexural modulus) The flexural modulus (MPa) of the PBS-based resin is preferably 100 MPa or more and 1000 MPa or less. By setting the flexural modulus of the PBS-based resin to a value within such a range, it becomes easy to obtain the effect of enabling the production of a PBS-based resin foamed sheet under various density conditions (it becomes easy to obtain the effect of enabling the production of a PBS-based resin that can handle a wide range of density conditions) and to obtain an effect of obtaining a PBS-based resin foamed sheet whose cushioning performance is less likely to decrease. From the viewpoint of these effects, the flexural modulus of the PBS-based resin is more preferably 200 MPa or more and 900 MPa or less, and even more preferably 300 MPa or more and 800 MPa or less.

[0020] The flexural modulus (MPa) of the PBS-based resin can be determined in accordance with JIS K7171:2008.

[0021] (Melting Point) The melting point (°C) of the PBS resin is preferably from 105 to 130° C., more preferably from 110 to 120° C. In this case, it is easy to obtain a PBS resin foamed sheet having appropriate compression strength and appropriate cushioning performance.

[0022] The melting point of the PBS-based resin is determined based on JIS K7121-1987. Specifically, a non-foamed resin sheet formed from the PBS-based resin is first prepared as a test piece, and the test piece is conditioned based on "(2) Measurement of melting temperature after a certain heat treatment" in "3. Conditioning of the test piece" in JIS K7121-1987. The heating rate and cooling rate in the conditioning are both 10°C / min. The conditioned test piece is heated from 30°C to 230°C at a heating rate of 10°C / min to obtain a DSC curve, and the apex temperature of the melting peak that appears on the DSC curve is the melting point of the PBS-based resin. The flow rate of nitrogen gas in the measurement environment is 30 mL per minute. In addition, when multiple melting peaks appear on the DSC curve, the apex temperature of the melting peak with the highest height based on the baseline is the melting point of the PBS-based resin.

[0023] (Other polymers) The above-mentioned foamable resin melt may contain other polymers other than the PBS-based resin. Examples of other polymers other than the PBS-based resin include thermoplastic resins (excluding PBS-based resins) and elastomers. When the foamable resin melt contains other polymers, the blending amount of the other polymers is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the PBS-based resin.

[0024] (Physical foaming agent) The physical foaming agent contains 90 mol % or more of a component consisting of 10 mol % to 100 mol % of a dialkyl ether having an alkyl group with 1 to 3 carbon atoms and 0 mol % to 90 mol % of carbon dioxide (wherein the total amount of the dialkyl ether and the carbon dioxide is 100 mol %). The above component (hereinafter also referred to as component A) contained in the physical foaming agent will be described below.

[0025] (Component A) Component A contains a dialkyl ether in which the alkyl group has 1 to 3 carbon atoms.

[0026] (Dialkyl ether) The dialkyl ether contained in component A includes both compounds having two alkyl groups with the same carbon number (same type of alkyl group) and compounds having two alkyl groups with different carbon numbers (different types of alkyl groups). Examples of dialkyl ethers having an alkyl group with 1 to 3 carbon atoms include dimethyl ether, diethyl ether, methyl ethyl ether, etc. From the viewpoint of easily obtaining the effect of excellent ease of handling of the physical foaming agent during the production of a PBS-based resin foamed sheet and from the viewpoint of easily obtaining the effect of stably forming a PBS-based resin foamed sheet, it is preferable that the main component of the dialkyl ether having an alkyl group with 1 to 3 carbon atoms contained in component A is dimethyl ether. More specifically, "the main component of the dialkyl ether is dimethyl ether" means that the ratio of dimethyl ether in the dialkyl ether having an alkyl group with 1 to 3 carbon atoms is 50 mol % or more. Note that, from the viewpoint of further enhancing the above-mentioned effect of the dialkyl ether, the ratio of dimethyl ether in the dialkyl ether having an alkyl group with 1 to 3 carbon atoms is more preferably 60 mol % or more, even more preferably 80 mol % or more, and even more preferably 90 mol % or more.

[0027] (carbon dioxide) In addition to the dialkyl ether, component A may further contain carbon dioxide as described above. By using carbon dioxide in addition to the dialkyl ether as component A, a more flame-retardant PBS-based resin foamed sheet can be obtained. In addition, a PBS-based resin foamed sheet having a relatively small bubble diameter and a relatively smooth surface can be obtained.

[0028] (Ratio of dialkyl ether to carbon dioxide, ratio of component A contained in the physical blowing agent) As described above, in component A, the dialkyl ether having 1 to 3 carbon atoms in the alkyl group is 10 mol% to 100 mol% and the carbon dioxide is 0 mol% to 90 mol%. However, the total amount of the dialkyl ether and carbon dioxide is 100 mol%. Furthermore, component A is contained in the physical foaming agent at a ratio of 90 mol% or more. However, the total amount of the physical foaming agent is 100 mol%. By producing a PBS-type resin foamed sheet using a foamable resin melt to which a predetermined amount of a physical foaming agent configured such that "the ratio (in mol%) of the dialkyl ether and carbon dioxide constituting component A is within the above-mentioned range and the ratio (in mol%) of component A contained in the physical foaming agent is within the above-mentioned range", it is possible to produce a PBS-type resin foamed sheet that corresponds to a wide range of density conditions (density conditions of the PBS-type resin foamed sheet) and to obtain a PBS-type resin foamed sheet that is less likely to deteriorate in cushioning performance.

[0029] From the viewpoint of increasing the closed cell ratio of the obtained PBS resin foamed sheet, it is more preferable that Component A contains 50 mol % or more of dialkyl ether having 1 to 3 carbon atoms in the alkyl group and 50 mol % or less of carbon dioxide, and it is even more preferable that Component A contains 80 mol % or more of dialkyl ether having 1 to 3 carbon atoms in the alkyl group and 20 mol % or less of carbon dioxide. Note that, from the viewpoint of increasing the production stability of the PBS resin foamed sheet, it is preferable that Component A consists of a dialkyl ether having 1 to 3 carbon atoms in the alkyl group.

[0030] (Amount of physical foaming agent added to foamable resin melt) The amount (mol) of the physical foaming agent added in the foamable resin melt is 0.2 mol or more and 2 mol or less per 1 kg of the resin component constituting the foamable resin melt. Furthermore, for the dialkyl ether contained in the physical foaming agent, the amount (mol) of the dialkyl ether added in the foamable resin melt is 0.1 mol or more per 1 kg of the resin component constituting the foamable resin melt. When the amount of the physical foaming agent added satisfies the above range and the amount of the dialkyl ether added satisfies the above range, it is easy to exhibit both the effect that it is possible to produce a polybutylene succinate-based resin foam sheet under various density conditions and the effect that it is possible to obtain a polybutylene succinate-based resin foam sheet whose cushioning performance is not easily deteriorated. From the viewpoint of further enhancing this effect, the amount of the dialkyl ether added is preferably 0.2 mol or more, more preferably 0.3 mol or more, per 1 kg of the resin component constituting the foamable resin melt.

[0031] (Physical foaming agents other than component A) As long as the intended object of the present invention can be achieved, the physical foaming agent may contain other physical foaming agents other than component A. Examples of other physical foaming agents include inorganic physical foaming agents such as nitrogen, alcohols having 1 to 4 carbon atoms such as ethanol and propanol, and saturated hydrocarbons having 3 to 6 carbon atoms such as propane, normal butane, isobutane, normal pentane, and isopentane.

[0032] From the viewpoint of stable production of a PBS-based resin foamed sheet, it is preferable that the physical foaming agent does not substantially contain saturated hydrocarbons having 3 to 6 carbon atoms. Specifically, it is preferable that "the physical foaming agent does not contain saturated hydrocarbons having 3 to 6 carbon atoms" or "when the physical foaming agent contains saturated hydrocarbons having 3 to 6 carbon atoms, the amount of saturated hydrocarbons having 3 to 6 carbon atoms added is 0.2 mol or less per kg of the resin component constituting the foamable resin melt." Furthermore, when the physical foaming agent contains saturated hydrocarbons having 3 to 6 carbon atoms, from the viewpoint of stable production of a PBS-based resin foamed sheet, it is more preferable that the amount of saturated hydrocarbons having 3 to 6 carbon atoms added is 0.1 mol or less per kg of the resin component, and even more preferable that the amount of saturated hydrocarbons having 3 to 6 carbon atoms is 0.05 mol or less per kg of the resin component.

[0033] When carbon dioxide is contained in component A contained in the physical foaming agent, the amount of carbon dioxide added can be determined as a value such that the amount of the physical foaming agent added, the amount of the dialkyl ether added, the abundance ratio of component A in the physical foaming agent, and the abundance ratio of the dialkyl ether and carbon dioxide in component A satisfy the respective ranges described above.

[0034] (Additives) The foamable resin melt may contain additives, if necessary, in addition to the above-mentioned raw material resin and physical foaming agent. Examples of other additives include shrinkage inhibitors, antioxidants, heat stabilizers, antistatic agents, conductivity imparting agents, weather resistance agents, ultraviolet absorbers, flame retardants, inorganic fillers, etc.

[0035] (Shrinkage prevention agent) The shrinkage inhibitor may be the same compound as various shrinkage inhibitors generally used in producing extruded foam sheets. Examples of the shrinkage inhibitor include one or more compounds selected from the group consisting of fatty acid esters, fatty amines, and fatty acid amides. Among them, preferred examples of the shrinkage inhibitor include fatty acid esters such as monostearate glyceride.

[0036] In addition, the method for producing a PBS-based resin foamed sheet according to the present invention can obtain a PBS-based resin foamed sheet that does not shrink excessively even without adding a shrinkage inhibitor. The reason for this is unclear, but it is believed that the dialkyl ether contained in the physical foaming agent is relatively easy to dissolve in the PBS-based resin and is easily separated from the PBS resin during extrusion foaming, allowing the foamable resin melt to be foamed well. In addition, by producing a PBS-based resin foamed sheet without adding a shrinkage inhibitor, the risk of the shrinkage inhibitor bleeding out from the obtained PBS-based resin foamed sheet can be eliminated, and the risk of the components derived from the shrinkage inhibitor migrating to an object in contact with the PBS-based resin foamed sheet and causing contamination of the object can be eliminated. From the viewpoint of making the PBS-based resin foam sheet less susceptible to shrinkage and reducing the risk of bleed-out, the amount (parts by mass) of the shrinkage prevention agent added to the foamable resin molten material is preferably 2 parts by mass or less (including 0) relative to 100 parts by mass of the resin components constituting the foamable resin molten material, preferably 1 part by mass or less (including 0), more preferably less than 0.5 parts by mass (including 0), and particularly preferably less than 0.05 parts by mass (including 0).

[0037] [1-2 Actions and Effects] According to the method for producing a PBS-based resin foamed sheet of the present invention, it is possible to satisfactorily produce a PBS-based resin foamed sheet that can meet various density conditions, i.e., a wide range of density conditions including a relatively low density, as described later in [2. Polybutylene succinate-based resin foamed sheet].

[0038] According to the method for producing a PBS-type resin foamed sheet of the present invention, it is possible to produce a sheet having a closed cell ratio (%) and an average cell diameter (VD) (mm) that satisfy a specific range under various density conditions (density conditions of a PBS-type resin foamed sheet) as described later in [2 Polybutylene succinate-based resin foamed sheet], so that it is possible to obtain a PBS-type resin foamed sheet whose shock-absorbing performance is unlikely to decrease under various density conditions. According to the method for producing a PBS-type resin foamed sheet of the present invention, it is possible to produce a sheet having a compression set suppressed to a predetermined value or less under various density conditions as described later. Therefore, it is possible to obtain a PBS-type resin foamed sheet whose shock-absorbing performance is unlikely to decrease under various density conditions.

[0039] [1-3 Application example of the manufacturing method for PBS-based resin foam sheet] In the above-mentioned method for producing a PBS-based resin foamed sheet according to the present invention, one embodiment of a method for producing a single-layer foamed sheet has been described. The method for producing a PBS-based resin foamed sheet according to the present invention may be applied to a method for producing a multi-layer foamed sheet having a foam layer (corresponding to the above-mentioned PBS-based resin foamed sheet) and a resin layer.

[0040] (Method of manufacturing multi-layer foam sheet) In the method for producing a multi-layer foamed sheet, a foamable resin melt containing a PBS-based resin and a resin melt for forming a resin layer containing a predetermined resin are co-extruded to produce a multi-layer extruded foamed sheet having a foamed layer containing a PBS-based resin and a resin layer provided on at least one side of the foamed layer. The method for producing a multi-layer foamed sheet can be carried out by using a commonly known co-extrusion device. For example, the co-extrusion device can be a co-extrusion device in which a co-extrusion annular die is attached to the downstream side of an extruder for forming a foamed layer and the downstream side of an extruder for forming a resin layer is connected to the co-extrusion annular die. The method for producing a PBS-based resin foamed sheet according to the present invention can be applied to the step of forming a foamed layer containing a PBS-based resin in the method for producing a multi-layer foamed sheet.

[0041] [2 Polybutylene succinate resin foam sheet] [2-1 Configuration] The polybutylene succinate-based resin foamed sheet (PBS-based resin foamed sheet) according to the present invention is a foamed sheet using polybutylene succinate-based resin as a base resin. The PBS-based resin foamed sheet according to the present invention can be obtained, for example, by the production method shown in the above-mentioned [1. Production method of polybutylene succinate-based resin foamed sheet]. In the following, the method described in detail in [1. Production method of polybutylene succinate-based resin foamed sheet] will be referred to as the production method according to the present invention.

[0042] (density) The PBS resin foam sheet according to the present invention has a density of 30 kg / m 3 More than 200kg / m 3 From the viewpoint of making the PBS-based resin foamed sheet lighter, the density of the PBS-based resin foamed sheet is set to 160 kg / m 3 It is preferable that the density is less than 100 kg / m 3 It is more preferable that the density is 30 kg / m or less. 3 More than 200kg / m 3 Foamed sheets can be obtained over a wide range of densities, including the following relatively low densities (relatively high expansion ratios):

[0043] Density of PBS resin foam sheet (kg / m 3 ) is the basis weight (g / m2) of the PBS resin foam sheet. 2 ) is BW, and the average thickness (mm) of the PBS-based resin foam sheet is AT, 2 It is specified as a value determined by converting the value (BW) / (AT) obtained by dividing the BW by the average thickness (mm).

[0044] (Basic weight) Basis weight of PBS resin foam sheet (g / m 2) can be a value determined by the following method. That is, a sheet piece of a given size (e.g., length: 100 mm × width: length in the width direction of the foamed sheet × thickness: thickness of the foamed sheet) is cut out from the PBS-based resin foamed sheet. The cut-out sheet piece is used as a test specimen. The area (m 2 ) and the mass (g) of the test piece. 2 ) is the basis weight (g / m2) of the PBS resin foam sheet. 2 ) is defined as:

[0045] (Average thickness) The average thickness (mm) of the PBS-based resin foam sheet can be determined by the following method. Measurement points are set at predetermined positions on the surface of the PBS-based resin foam sheet. A plurality of positions are selected at 50 mm intervals along the width direction of the foam sheet within the surface of the PBS-based resin foam sheet excluding 20 mm at both ends in the width direction of the PBS-based resin foam sheet, and the selected positions are set as measurement points. The thickness of the PBS-based resin foam sheet at each measurement point is measured using a thickness gauge to obtain a measured value. The average value of the measured values ​​set at each measurement point is calculated, and the calculated value is set as the thickness (mm) of the foam sheet. The width direction of the PBS-based resin foam sheet is set as a direction perpendicular to both the extrusion direction of the foamable resin melt when producing the PBS-based resin foam sheet and the thickness direction of the PBS-based resin foam sheet. The thickness gauge is not particularly limited, but for example, a dial thickness gauge (manufactured by PEACOCK, model: H-2.4N) can be used.

[0046] (Closed bubble rate) The PBS-based resin foamed sheet according to the present invention has a closed cell ratio of 30% or more. The PBS-based resin foamed sheet can be a sheet whose shock-absorbing performance is unlikely to decrease when the closed cell ratio is 30% or more. The PBS-based resin foamed sheet having a closed cell ratio of 30% or more can be obtained, for example, by using the above-mentioned production method according to the present invention. Specifically, a physical foaming agent containing a specific amount of component A containing at least a dialkyl ether is used during extrusion foaming, and a foamable resin melt to which a predetermined amount of dialkyl ether is added is extrusion foamed, thereby obtaining a PBS-based resin foamed sheet having a closed cell ratio of a predetermined value or more in a wide density range including a relatively small density. From the viewpoint of obtaining a sheet whose shock-absorbing performance is unlikely to decrease, the closed cell ratio of the PBS-based resin foamed sheet is preferably 40% or more, more preferably 50% or more, and even more preferably 60% or more. The upper limit of the closed cell ratio of the PBS-based resin foamed sheet may be 95%, 90%, or 80%.

[0047] (How to determine the closed cell ratio) The closed cell ratio (%) of the PBS-based resin foam sheet can be determined as follows. A plurality of test pieces are prepared by cutting the PBS-based resin foam sheet from the vicinity of the center of the width direction of the sheet with dimensions of length: 25 mm x width: 25 mm x foam sheet thickness. A test piece is prepared as a laminate of a plurality of test pieces so that the total thickness (total thickness of the test pieces) is closest to 20 mm. In accordance with procedure C described in ASTM D2856-70, an air comparison specific gravity meter (e.g., Toshiba Beckman Co., Ltd. 930 type) is used to measure the actual volume (sum of the volume of the closed cells and the volume of the resin part): Vx (L) of the test piece. The obtained value is used to calculate the closed cell ratio (%) of the test piece according to the following formula (1). The above measurement is performed on five test pieces, and the arithmetic average value of the closed cell ratio obtained in each measurement is taken as the closed cell ratio (%) of the PBS-based resin foam sheet.

[0048]

number

[0049] In the above formula (1), Va, W, and ρ are as follows: Va: Apparent volume (cm) of the PBS-based resin foam sheet specimen used for measurement 3 ) W: Mass (g) of the PBS-based resin foamed sheet specimen used in the measurement ρ: Density of the resin constituting the PBS resin foam sheet (g / cm 3 )

[0050] (Average bubble diameter (VD)) The PBS-based resin foamed sheet according to the present invention has an average bubble diameter (VD) in the thickness direction of the PBS-based resin foamed sheet (hereinafter simply referred to as the thickness direction) of 0.5 mm to 1.5 mm. When the average bubble diameter (VD) in the thickness direction of the PBS-based resin foamed sheet is 0.5 mm to 1.5 mm, the sheet has good cushioning performance and is less likely to deteriorate. From this viewpoint, the average bubble diameter (VD) in the thickness direction of the PBS-based resin foamed sheet is preferably 0.6 mm to 1.4 mm, more preferably 0.7 mm to 1.3 mm. By using the above-mentioned production method according to the present invention, a PBS-based resin sheet having an average bubble diameter (VD) in the thickness direction of 0.5 mm to 1.5 mm can be obtained.

[0051] (Bubble deformation rate (VD / TD)) The PBS-based resin foamed sheet according to the present invention is preferably a sheet having a bubble deformation ratio (VD / TD) of 0.5 or more and 1.2 or less. The bubble deformation ratio (VD / TD) indicates the ratio of the average bubble diameter (VD) in the thickness direction of the foamed sheet to the average bubble diameter (TD) in the width direction of the foamed sheet. When the bubble deformation ratio (VD / TD) of the PBS-based resin foamed sheet is 0.5 or more and 1.2 or less, it becomes easier to obtain a sheet that exhibits good cushioning performance as a PBS-based resin foamed sheet. From the viewpoint of easily exhibiting good cushioning performance, the bubble deformation ratio (VD / TD) is preferably 0.5 or more and 1.2 or less, more preferably 0.6 or more and 1.1 or less, and even more preferably 0.7 or more and 1.0 or less. By using the above-mentioned production method according to the present invention, a PBS-based resin sheet having a bubble deformation ratio (VD / TD) of 0.5 or more and 1.2 or less can be obtained. The width direction of the PBS resin foam sheet is a direction perpendicular to both the extrusion direction of the foamable resin melt in producing the PBS resin foam sheet and the thickness direction of the PBS resin foam sheet.

[0052] (Bubble deformation ratio (TD / MD)) The PBS-based resin foamed sheet according to the present invention is preferably a sheet having a bubble deformation ratio (TD / MD) of 0.8 or more and 1.5 or less. The bubble deformation ratio (TD / MD) indicates the ratio of the average bubble diameter (TD) in the width direction of the foamed sheet to the average bubble diameter (MD) in the extrusion direction of the foamed sheet. When the bubble deformation ratio (TD / MD) of the PBS-based resin foamed sheet is 0.8 or more and 1.5 or less, a sheet exhibiting good cushioning performance as a PBS-based resin foamed sheet is more easily obtained. From the viewpoint of easily exhibiting good cushioning performance, the bubble deformation ratio (TD / MD) is preferably 0.9 or more and 1.4 or less. By using the above-mentioned production method according to the present invention, a PBS-based resin sheet having a bubble deformation ratio (TD / MD) of 0.8 or more and 1.5 or less can be obtained.

[0053] The above-mentioned average cell diameter (VD), cell deformation ratio (VD / TD) and cell deformation ratio (TD / MD) can be determined, for example, by appropriately adopting the following methods for determining the average cell diameter (VD), the method for determining the average cell diameter (TD) and the method for determining the average cell diameter (MD).

[0054] (How to determine the mean bubble diameter (VD)) The PBS-based resin foam sheet is cut along its width direction (TD direction). As a result, a sheet piece having a predetermined length (e.g., 10 cm) in the extrusion direction (MD direction) and the entire sheet width (the length in the width direction is the entire width of the PBS-based resin foam sheet) is cut out as the PBS-based resin foam sheet. The thickness of the sheet piece is the thickness of the PBS-based resin foam sheet. Such a sheet piece is used as a measurement sheet for measuring the bubble diameter. Five points are randomly selected from the cut surface of the measurement sheet, and each point is determined as an observation target part. The observation target part is enlarged to a predetermined magnification (e.g., 50 times) using a microscope, and an enlarged image of the observation target part is taken so that the entire cut surface in the thickness direction of the foam sheet is included in the observation field. In the enlarged image, all bubbles observed in the observation field (excluding bubbles intersecting the boundary that divides the observation field from the outside) are identified, and the bubble diameter (mm) is measured as the maximum length of each bubble along the thickness direction (VD direction). The arithmetic mean value is calculated by averaging the measured bubble diameters in the thickness direction for each bubble diameter. This arithmetic mean value is defined as the average bubble diameter (VD) in the thickness direction of the PBS-based resin foamed sheet. The average bubble diameter (VD) is a value (mm) specified based on the cross section in the width direction (TD cross section).

[0055] (How to determine the mean bubble diameter (TD)) Based on the enlarged image of the observation area, all bubbles observed in the observation field (excluding bubbles intersecting the boundary separating the observation field from its outside) were identified, and the bubble diameter (mm) was measured as the maximum length of each bubble along the width direction (TD direction). With the exception of this, the average bubble diameter in the width direction (TD) of the PBS-based resin foamed sheet can be determined in the same manner as described in the above-mentioned method for determining the average bubble diameter (VD).

[0056] (How to determine the mean bubble diameter (MD)) At the widthwise center of the measurement sheet shown in the above-mentioned method for specifying the average bubble diameter (VD), the measurement sheet is cut along the extrusion direction to prepare a sheet piece with the cross section of the center exposed. Then, this sheet piece is used as a measurement sheet for the average bubble diameter (MD), and an observation target portion is selected at the cross section of the center portion. Based on the enlarged image of the observation target portion, all bubbles observed in the observation field (excluding bubbles intersecting the boundary that divides the observation field and its outside) are identified, and the bubble diameter (mm) is measured as the maximum length of each bubble along the extrusion direction (MD direction). For other points, the average bubble diameter (MD) in the extrusion direction of the PBS-based resin foamed sheet can be specified in the same manner as described in the above-mentioned method for specifying the average bubble diameter (VD).

[0057] (Less deterioration of cushioning performance) The PBS-based resin foam sheet according to the present invention is a sheet whose shock-absorbing performance is not easily deteriorated. The term "the shock-absorbing performance is not easily deteriorated" refers to a property in which, even if compressive strain occurs in the PBS-based resin foam sheet when stress is applied to the PBS-based resin foam sheet in the thickness direction (VD direction) for a predetermined time (long period of time), the compressive strain can be reduced or eliminated to a predetermined level or more after the stress is removed (the shock-absorbing performance is not easily impaired). The degree of resistance to deterioration of the shock-absorbing performance of the PBS-based resin foam sheet can be indicated by the value of the compression set (hereinafter, simply referred to as compression set) measured according to JIS K 6767:1999. The PBS-based resin foam sheet according to the present invention is preferably a sheet whose compression set is 5% or less. In addition, by using the production method according to the present invention, a sheet whose shock-absorbing performance is not easily deteriorated and whose compression set is 5% or less can be obtained as a PBS-based resin foam sheet.

[0058] (Method of measuring compression set) The compression set (%) of the PBS-based resin foam sheet is a value measured based on JIS K 6767:1999. The compression set (%) of the PBS-based resin foam sheet can be specifically specified as follows based on the description of "4. Compression set" in JIS K 6767:1999. First, cut out a plurality of sheet pieces with dimensions of 50 mm length x 50 mm width x foam sheet thickness from the PBS-based resin foam sheet. The cut out sheet pieces are stacked together to produce a laminate with a thickness of about 25 mm. This laminate is used as a test specimen. Three test specimens are prepared. For each test specimen, a compression tester is used to compress the test specimen by loading stress in the thickness direction of the test specimen until 25% of the thickness of the test specimen is compressed (until the thickness of the test specimen is 75% of the thickness before compression), and the test specimen is left in the compressed state for 22 hours. The specimen is then released from the compressed state (stress is removed), and the thickness (mm) of the specimen is measured 24 hours after it was released from the compressed state. The measured thickness is designated as TH1, and the thickness of the specimen before compression is designated as TH. The thickness of the specimen before compression is designated as 100%, and the percentage change in thickness (%) of the specimen is calculated as ((TH-TH1) / TH) x 100. This value is calculated for each specimen. The arithmetic mean value of the calculated values ​​is regarded as the compression set (%) of the PBS-based resin foam sheet.

[0059] (Compressive stress at 25% strain) The compressive stress (kPa) of the PBS-based resin foamed sheet at 25% strain is preferably 20 kPa or more and 300 kPa or less. When the compressive stress of the PBS-based resin foamed sheet at 25% strain satisfies this range, the PBS-based resin foamed sheet is a sheet that is likely to exhibit good cushioning performance. From the viewpoint of exhibiting good cushioning performance, the compressive stress of the PBS-based resin foamed sheet at 25% strain is more preferably 25 kPa or more and 250 kPa or less, and further preferably 30 kPa or more and 200 kPa or less.

[0060] (Method of measuring compressive stress (kPa) at 25% strain) The compressive stress (kPa) of the PBS-based resin foam sheet at 25% strain is the compressive stress at 25% strain measured based on JIS K 6767:1999. Therefore, the compressive stress of the PBS-based resin foam sheet at 25% strain is specified using the same method as the method described in the measurement method of the compression permanent set described above. That is, a plurality of sheet pieces are cut out from the PBS-based resin foam sheet with dimensions of 50 mm length × 50 mm width × thickness of the PBS-based resin foam sheet, and a plurality of laminates with a thickness of about 25 mm are produced by stacking the plurality of sheet pieces. Each of these laminates is used as a test specimen. Then, a compression test is performed using a compression tester to compress one of the test specimens in the thickness direction at a compression speed of 10 mm / min. The compression test measured the compressive stress (kPa) of the test specimen at 25% strain. The measurement of the compressive stress (kPa) was performed for each of the plurality of test specimens, and the arithmetic average value of the measured compressive stresses was taken as the compressive stress at 25% strain. The number of the multiple test specimens can be, for example, three.

[0061] (non-crosslinked) The PBS-based resin foam sheet according to the present invention is preferably a non-crosslinked foam sheet. Non-crosslinked means that the gel fraction is less than 5% (including 0). The non-crosslinked foam sheet can be obtained by avoiding the application of a process of forming a crosslinked structure in the resin by reacting the PBS-based resin with a crosslinking agent such as a multifunctional compound, or a process of forming a crosslinked structure in the foam sheet by irradiating with an electron beam, etc. The non-crosslinked foam sheet has an excellent balance between compressive strength and cushioning performance, can be produced at low cost, and is easy to recycle recovered raw materials, so it can be widely used for applications such as cushioning materials used in packaging. By using the production method according to the present invention, a non-crosslinked foam sheet can be obtained as a PBS-based resin foam sheet.

[0062] (Method of Measuring Gel Fraction) The gel fraction of the PBS-based resin foamed sheet can be determined as follows. Approximately 50 mg of the PBS-based resin foamed sheet is precisely weighed, and immersed in 25 ml of xylene at 130°C for 3 hours. The sheet is then filtered through a 200-mesh stainless steel wire net and washed with acetone. The insoluble matter remaining on the wire net is then vacuum-dried, and the mass (mg) of the insoluble matter is precisely weighed, and the gel fraction (%) is calculated as a percentage according to the following formula (2). The mass (mg) of the foam weighed in formula (2) is the mass of the PBS-based resin foamed sheet precisely weighed before immersion in xylene.

[0063]

number

[0064] (Content of saturated hydrocarbons with carbon numbers of 3 to 6 in PBS resin foam sheet) The PBS-based resin foam sheet according to the present invention is preferably a sheet in which the content of saturated hydrocarbons having a carbon number of 3 to 6 (carbon number of 3 or more and 6 or less) is 0.2 mol or less (including 0 (mol)) per 1 kg of the PBS-based resin foam sheet. When the content of saturated hydrocarbons having a carbon number of 3 to 6 in the PBS-based resin foam sheet is 0.2 mol or less per 1 kg of the PBS-based resin foam sheet, or when the PBS-based resin foam sheet does not contain hydrocarbons having a carbon number of 3 to 6 (the content of saturated hydrocarbons having a carbon number of 3 to 6 is 0 mol), even if the foam sheet is stored in a sealed space such as a container for export, the hydrocarbon concentration in the sealed space can be prevented from reaching the explosion limit concentration. In addition, the PBS-based resin foam sheet can be a flame-resistant sheet. From this viewpoint, the content of saturated hydrocarbons having a carbon number of 3 to 6 in the PBS-based resin foam sheet is preferably 0.1 mol or less (including 0) per 1 kg of the PBS-based resin foam sheet, and more preferably 0.05 mol or less (including 0) per 1 kg of the PBS-based resin foam sheet. According to the above-mentioned production method of the present invention, since substantially no saturated hydrocarbons having 3 to 6 carbon atoms are added to the foamable molten resin, a PBS-based resin foamed sheet having a content of saturated hydrocarbons having 3 to 6 carbon atoms of 0.2 mol or less (including 0) per kg of the PBS-based resin foamed sheet can be obtained.

[0065] (Method for determining the content of saturated hydrocarbons with 3 to 6 carbon atoms) The content of saturated hydrocarbons having 3 to 6 carbon atoms in the PBS-based resin foamed sheet can be measured by applying gas chromatography using a headspace method to the PBS-based resin foamed sheet aged for 24 hours from the time of production.

[0066] [2-2 Actions and Effects] The PBS resin foam sheet according to the present invention has a density of 30 kg / m 3 More than 200kg / m 3Even in a wide density range including a relatively low density such as the following range, by having a specific closed cell diameter and average cell diameter, the sheet has excellent resistance to deterioration of cushioning performance. In addition, the PBS resin foamed sheet according to the present invention has excellent environmental load reduction properties because the raw resin is biodegradable.

[0067] [3.Application examples of polybutylene succinate resin foam sheets] The polybutylene succinate-based resin foam sheet (PBS-based resin foam sheet) according to the present invention can be suitably used as a packaging cushioning material. Examples of the packaging cushioning material include cushioning materials used for packaging electronic devices, fruits, and the like. When used as a packaging cushioning material, the PBS-based resin foam sheet may be subjected to secondary molding. The PBS-based resin foam sheet may be cut into a desired shape according to the shape of packaging materials or packaged items, for example. The PBS-based resin foam sheet may also be subjected to thermoforming.

[0068] From the viewpoint of obtaining a packaging cushioning material having excellent resistance to deterioration in cushioning performance, it is preferable that the PBS-based resin foamed sheet forming the packaging cushioning material has a compression set of 5% or less as measured based on the above-mentioned JIS K 6767: 1999. Since the PBS-based resin foamed sheet obtained by the production method of the present invention has a compression set of 5% or less, the production method of the present invention can be used to produce a packaging cushioning material configured to have a compression set of 5% or less.

[0069] The packaging cushioning material using the PBS-based resin foam sheet according to the present invention has excellent biodegradability and reduces the environmental load because the base resin is a PBS-based resin. 3 More than 200kg / m 3Even in a wide range of densities, as long as the foam sheet satisfies the condition that the average bubble diameter in the thickness direction is 0.5 mm or more and 1.5 mm or less, and the closed cell ratio is 30% or more, it is possible to form a packaging cushioning material that is resistant to deterioration in cushioning performance (small compression set).

[0070] Next, a more detailed explanation will be given using examples. EXAMPLES

[0071] The PBS-based resin foam sheet was produced using a tandem extruder consisting of a first extruder (65 mmφ) and a second extruder (90 mmφ) connected together with a circular die (diameter 60 mm) attached downstream of the second extruder.

[0072] As shown in Table 1, compounds that can be used as physical foaming agents include dimethyl ether (referred to as DME in Table 1) and carbon dioxide (referred to as CO 2 In the above, s-Bu was prepared. The above-mentioned dimethyl ether corresponds to a dialkyl ether. Dimethyl ether and carbon dioxide constitute the above-mentioned component A. s-Bu is a mixture of isobutane and normal butane in a mass ratio (isobutane:normal butane) of 30:70, and corresponds to a saturated hydrocarbon having a carbon number of 3 to 6.

[0073] The raw resin used to make the PBS-based resin foam sheet was a polybutylene succinate-based resin (PBS-based resin) (manufactured by Mitsubishi Chemical Corporation, product model number: FZ91PB), and the additive used was a sodium bicarbonate citrate-based air bubble regulator (manufactured by Dainichiseika Chemicals, product model number: PO217K).

[0074] The flexural modulus of the prepared PBS resin is 650 MPa and its density is 1260 kg / m 3 Its melting point was 113°C and its biomass content was 50%.

[0075] (Flexural modulus) The flexural modulus of the PBS-based resin was specified as follows in accordance with JIS K7171:2008. The PBS-based resin was heat-pressed at 180°C to produce a sheet with a thickness of 4 mm, and a sheet piece with a length of 80 mm, width of 10 mm, and thickness of 4 mm was cut out from this sheet, and this sheet piece was used as the test specimen. The conditions for the flexural modulus test were that the radius R1 of the indenter and the radius R2 of the support table were both 5 mm, the distance between the supports was 64 mm, and the test speed was 2 mm / min.

[0076] (Melting Point) The melting point of the PBS-based resin was determined based on JIS K7121-1987. Specifically, the state of the PBS-based resin as a test piece was adjusted based on "(2) When the melting temperature is measured after a certain heat treatment" in "3. Condition adjustment of the test piece" described in JIS K7121-1987. The test piece after the condition adjustment was heated from 23°C to 230°C at a heating rate of 10°C / min to obtain a DSC curve. The flow rate of nitrogen gas in the measurement environment was 30 mL per minute. The apex temperature of the melting peak that appeared on the DSC curve was taken as the melting point. The measurement device used was a heat flux differential scanning calorimeter (manufactured by SII Nanotechnology Co., Ltd., model number: DSC7020).

[0077] (Biomass ratio) The biomass content (%) of the PBS-based resin was determined based on the method in accordance with ASTM D 6866 described above.

[0078] Examples 1 to 5 (Formation process of foamable resin melt) A polybutylene succinate resin and a bubble control agent were supplied to a tandem extruder and kneaded. The bubble control agent was added in an amount of 0.5 parts by mass relative to 100 parts by mass of the polybutylene succinate resin. A physical foaming agent was injected midway through the first extruder and further kneaded. This resulted in the formation of a foamable resin melt. In all of Examples 1 to 5, the physical foaming agent had component A. In Table 1, the amount of each compound constituting the physical foaming agent is shown in terms of the amount (mol / kg) added per 1 kg of the resin component (PBS resin) constituting the foamable resin melt, and the proportion of dimethyl ether (referred to as DME proportion in Table 1) (mol%) in the physical foaming agent is also shown.

[0079] (Extrusion foaming process) The foamable resin melt was transferred to the second extruder and adjusted to about 115°C (foaming temperature). The foamable resin melt was then extruded from an annular die provided downstream of the second extruder and foamed to obtain a cylindrical foam. The cylindrical foam was cut open with a cutter while being cooled with a mandrel having a diameter of 212 mm, and further taken up in a roll by a winder under the conditions of the take-up speed (m / min) shown in Table 1 to obtain a PBS-based resin foam sheet.

[0080] The basis weight (g / m2) of the obtained PBS-based resin foamed sheet was 2 ), average thickness (mm), density (kg / m 3), closed cell ratio (%), and average cell diameter (mm) were measured. As for the average cell diameter (mm), the average cell diameter in the thickness direction (VD), the average cell diameter in the width direction (TD), and the average cell diameter in the extrusion direction (MD) were measured. The results of each measurement are shown in Table 2. In addition, in Table 2, the cell deformation ratio is also shown. As the cell deformation ratio, the ratio of the average cell diameter in the thickness direction (VD) to the average cell ratio in the width direction (TD) (the average cell diameter in the thickness direction (VD) when the average cell ratio in the width direction is set to 1), and the ratio of the average cell diameter in the width direction (TD) to the average cell ratio in the extrusion direction (MD) (the average cell diameter in the width direction (TD) when the average cell ratio in the extrusion direction is set to 1) are shown in the (VD / TD) and (TD / MD) columns in Table 2, respectively.

[0081] For PBS resin foam sheets, the basis weight (g / m 2 ), average thickness (mm), density (kg / m 3 ), closed cell content (%), average cell diameter in the thickness direction (VD) (values ​​measured based on a cross section extending in the width direction (TD cross section)), average cell diameter in the width direction (TD), and average cell diameter in the extrusion direction (MD) were measured according to the methods described above.

[0082] The obtained PBS-based resin foamed sheet was used to measure the compressive stress (kPa) at 25% strain, the compression set (%), and the content (mol / kg) of saturated hydrocarbons having 3 to 6 carbon atoms. The results of each measurement are shown in Table 2. In Table 2, the content (mol / kg) of saturated hydrocarbons having 3 to 6 carbon atoms is referred to as "saturated hydrocarbon content."

[0083] (Method of measuring compressive stress (kPa) at 25% strain) The compressive stress (kPa) of the PBS-based resin foam sheet at 25% strain is the compressive stress at 25% strain measured based on JIS K 6767:1999. A number of sheet pieces were cut out from the PBS-based resin foam sheet with dimensions of 50 mm length x 50 mm width x thickness of the PBS-based resin foam sheet, and a laminate with a thickness of about 25 mm was produced by stacking the multiple sheet pieces. Three laminates were produced. Each of these laminates was used as a test specimen. Using a compression tester, one of the test specimens was compressed in the thickness direction at a compression speed of 10 mm / min. The compressive stress (kPa) of the test specimen at 25% strain was measured by the compression test. The compressive stress (kPa) was measured for each of the three test specimens, and the arithmetic average value of the measured compressive stresses was taken as the compressive stress at 25% strain.

[0084] (Method of measuring compression set (%)) The compression set (%) of the PBS-based resin foam sheet was measured based on JIS K 6767:1999. Three test specimens were prepared in the same manner as the measurement method of the compressive stress (kPa) at 25% strain described above. Using a compression tester, the test specimen was compressed by 25% in the thickness direction (compressed to 75% of the thickness before compression), and left in this state for 22 hours. The compressed state was then released, and the thickness of the test specimen was measured after 24 hours to obtain the measured thickness. When the measured value is TH1 and the thickness of the laminate before the compression test is TH, the change in the measured thickness after the compression test when the thickness of the laminate before the compression test is 100% ((TH-TH1) / TH×100) (%) was taken as the compression set of the test specimen. This measurement was performed on three test specimens, and the arithmetic average value of the changes in the measured thickness was taken as the compression set.

[0085] (Method for measuring the content (mol / kg) of saturated hydrocarbons with 3 to 6 carbon atoms) The content (residual amount) (mol / kg) of saturated hydrocarbons having carbon numbers of 3 to 6 in the PBS-based resin foam sheet was measured by gas chromatography using the headspace method as follows. First, the roll-shaped material, which is the PBS-based resin foam sheet wound into a roll, was cured for 24 hours after the end of winding under conditions of 23°C and atmospheric pressure. After curing, a sheet piece of about 0.3 g was taken as a measurement sample from the vicinity of the center in the width direction of the PBS-based resin foam sheet wound into the roll-shaped material, and the measurement sample was sealed in a glass bottle for measurement. Next, a quantitative analysis of the content of saturated hydrocarbons having carbon numbers of 3 to 6 remaining in the measurement sample was performed by FID (hydrogen flame ionization detection) using a headspace gas chromatograph "GC353B" manufactured by GL Science Co., Ltd. In the measurement of the quantitative analysis, a column "CP-PoraPLOTQ Model CP-7553" manufactured by VARIAN Co., Ltd. was used. The measurement sample in the glass bottle was melted at a temperature of 160°C, and the physical foaming agent remaining in the measurement sample was degassed to separate the physical foaming agent from the measurement sample, and then the physical foaming agent separated from the measurement sample was poured into a column at a temperature of 50°C to separate each component constituting the physical foaming agent, and each component was quantified using a flame ionization detector (FID detector). From the quantified value, the content (mol / kg) of saturated hydrocarbons with carbon numbers of 3 to 6 per 1 kg of the PBS-based resin foam sheet was calculated.

[0086] Comparative Examples 1 to 5 In Comparative Examples 1 to 5, the forming step and the extrusion step of the foamable resin melt were carried out in the same manner as in Examples 1 to 5. However, as the conditions of the physical foaming agent, the conditions of the compound and the added amount shown in Comparative Examples 1 to 5 in Table 1 were used. Note that, in Table 1, the added amount of each compound constituting the physical foaming agent is also shown as the added amount (mol / kg) per 1 kg of the resin component (PBS-based resin) constituting the foamable resin melt, and further, the ratio (mol%) of dimethyl ether in the physical foaming agent is also shown.

[0087] In Comparative Example 1 and Comparative Examples 3 to 5, PBS-based resin foamed sheets were obtained. In Comparative Example 2, when the foamable resin melt was extruded, the foaming agent was separated from the foamable resin melt and spouted out of the die at irregular intervals, so that a good foamed sheet could not be obtained. In addition, in Comparative Example 2, the take-up speed could not be determined.

[0088] The PBS-based resin foamed sheets obtained in Comparative Example 1 and Comparative Examples 3 to 5 were measured for basis weight (g / m) in the same manner as in Examples 1 to 5. 2 ), average thickness (mm), density (kg / m 3 ), expansion ratio (times), closed cell ratio (%), and average cell diameter (mm) were measured. Regarding the average cell diameter (mm), the average cell diameter in the thickness direction (VD), the average cell diameter in the width direction (TD), and the average cell diameter in the extrusion direction (MD) were measured. The results of each measurement are shown in Table 2. Note that Table 2 also shows the cell deformation rate.

[0089] The PBS resin foamed sheets obtained in Comparative Example 1 and Comparative Examples 3 to 5 were used to measure the compressive stress (kPa) at 25% strain, the compression set (%) measured based on JIS K 6767:1999, and the saturated hydrocarbon content (mol / kg) in the same manner as in Examples 1 to 5. The results of each measurement are shown in Table 2.

[0090] [Table 1]

[0091] [Table 2]

[0092] According to Example 1 and Comparative Example 1, it was confirmed that the use of component A containing a dialkyl ether as a physical foaming agent allows the foamed sheet to have a high closed cell ratio. In addition, it was confirmed that the compression set of Example 1 was suppressed more than that of Comparative Example 1, and thus a PBS-based resin foamed sheet excellent in resistance to deterioration of cushioning performance could be obtained. According to Examples 1 to 3, it was confirmed that the use of component A containing a dialkyl ether as a physical foaming agent allows the foaming ratio to be increased. According to Example 3 and Comparative Example 4, it was confirmed that the use of a dialkyl ether as a physical foaming agent within a specific range allows the foamed sheet to maintain the closed cell ratio and suppress the compression set within a predetermined range.

Claims

1. A method for producing a polybutylene succinate-based resin foamed sheet by extruding and foaming a foamable resin melt obtained by kneading a polybutylene succinate-based resin and a physical foaming agent, comprising the steps of: the amount of the physical foaming agent added is 0.2 mol or more and 2 mol or less per 1 kg of a resin component constituting the foamable resin molten material, The physical foaming agent contains 90 mol % or more of a component consisting of 10 mol % to 100 mol % of a dialkyl ether having an alkyl group with 1 to 3 carbon atoms and 0 mol % to 90 mol % of carbon dioxide (wherein the total amount of the dialkyl ether and the carbon dioxide is 100 mol %), The amount of the dialkyl ether added is 0.1 mol or more per 1 kg of the resin component constituting the foamable resin melt. A method for producing a polybutylene succinate resin foam sheet.

2. The physical foaming agent does not contain a saturated hydrocarbon having 3 to 6 carbon atoms, or the physical foaming agent contains a saturated hydrocarbon having a carbon number of 3 to 6, and the amount of the saturated hydrocarbon added is 0.2 mol or less per 1 kg of a resin component constituting the foamable resin molten material; A method for producing the polybutylene succinate resin foamed sheet according to claim 1.

3. The polybutylene succinate resin has a biomass content of 30% or more; The flexural modulus of the polybutylene succinate resin is 100 MPa or more and 1000 MPa or less. A method for producing the polybutylene succinate resin foamed sheet according to claim 1 or 2.

4. The density of the polybutylene succinate resin foam sheet is 30 kg / m ３ More than 200kg / m ３ Below is the A method for producing the polybutylene succinate resin foamed sheet according to claim 1 or 2.

5. Density is 30 kg / m ３ More than 200kg / m ３ A polybutylene succinate-based resin foam sheet comprising: The polybutylene succinate-based resin foamed sheet has an average cell diameter in a thickness direction of 0.5 mm or more and 1.5 mm or less, The polybutylene succinate-based resin foamed sheet has a closed cell rate of 30% or more.

6. 6. The polybutylene succinate-based resin foamed sheet according to claim 5, wherein the content of saturated hydrocarbons having a carbon number of 3 to 6 in the polybutylene succinate-based resin foamed sheet is 0.2 mol or less (including 0) per 1 kg of the polybutylene succinate-based resin foamed sheet.

7. A packaging cushioning material comprising the polybutylene succinate-based resin foamed sheet according to claim 5 or 6, The polybutylene succinate resin foam sheet has a compression set of 5% or less as measured in accordance with JIS K 6767:1999.

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