Ethylene-vinyl acetate copolymer resin, molded article and foamed article

Abstract

The present invention relates to an ethylene-vinyl acetate copolymer resin, a molded article, and a foamed article. The present invention provides an ethylene-vinyl acetate copolymer resin that suppresses the generation of connected particles when manufacturing small particles and has desired foaming moldability, and a molded article and a foamed article using the ethylene-vinyl acetate copolymer resin. An ethylene-vinyl acetate copolymer resin comprising ethylene units and 3.0% by mass or more and less than 10.0% by mass of vinyl acetate units, having a melt flow rate of 0.1 g / 10 min or more and 1.0 g / 10 min or less under a load of 2.16 kg, an elution peak top temperature in an elution temperature-elution amount curve obtained by temperature-elution fractionation measurement of cross-fractionation chromatography of 58°C or more and 75°C or less, and a dw / dT at the elution peak top temperature of 6 or more and 12 or less.

Description

Technical Field

[0001] The present invention relates to an ethylene-vinyl acetate copolymer resin, a molded article and a foamed article. Background Art

[0002] Ethylene-vinyl acetate copolymer resins are used in a wide range of industrial fields as foamed molded articles, such as thermal insulation materials and cushioning materials, due to their excellent properties such as flexibility, mechanical strength, electrical insulation, weather resistance, and durability. Further improvements in these properties are desired.

[0003] Patent Document 1 proposes expandable composite resin particles and composite foamed molded articles obtained using the expandable composite resin particles. The expandable composite resin particles comprise an ethylene-vinyl acetate copolymer resin and a polystyrene-based resin, with the surface layer comprising the ethylene-vinyl acetate copolymer resin and the core comprising the polystyrene-based resin. The expandable composite resin particles are produced by impregnating styrene monomer into an ethylene-vinyl acetate copolymer resin suspended in water and polymerizing styrene in the ethylene-vinyl acetate copolymer resin.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5629689 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] In the preparation of the above-mentioned foamable composite resin particles, the particle size of the commercially available ethylene-vinyl acetate copolymer resin particles is large and difficult to directly compound. Therefore, it is necessary to use an extruder to granulate the ethylene-vinyl acetate copolymer resin particles again, for example, to perform a small particle treatment so that each 100 particles are about 40 mg to about 80 mg.

[0009] However, this process has the following problem in producing small particles: since the small particles are connected to each other to form connected particles, it is impossible to control the particle size as planned, and the yield in the composite process and the yield in the foaming process are reduced.

[0010] To address this problem, reducing the vinyl acetate content and melt flow rate of the ethylene-vinyl acetate copolymer resin tends to suppress the formation of connected particles during the production of small pellets. However, this, on the other hand, increases the melt tension, making uniform foaming difficult and tending to reduce foam moldability. In other words, it is difficult to achieve a balance between suppressing the formation of connected particles during the production of small pellets and achieving the desired properties of the composite foamed molded article.

[0011] Therefore, in view of the above problems, the present invention aims to provide an ethylene-vinyl acetate copolymer resin that suppresses the generation of connected particles when producing small particles and has desired foaming moldability, and a molded article and a foamed article using the ethylene-vinyl acetate copolymer resin.

[0012] Means used to solve problems

[0013] The present inventors have conducted intensive research to solve the problems of the above-mentioned prior art. As a result, they have discovered that the generation of connected particles during the production of small pellets can be suppressed by combining the specific physical properties of ethylene-vinyl acetate copolymer resins. In addition, the above-mentioned problems can be solved by using ethylene-vinyl acetate copolymer resins having a predetermined melt tension and desired foaming moldability, thereby completing the present invention.

[0014] The present invention provides an ethylene-vinyl acetate copolymer resin having a predetermined vinyl acetate unit content and a predetermined melt flow rate, and having a controlled crystal structure and branched structure as indicated by a predetermined elution peak top temperature in an elution temperature-elution amount curve obtained by temperature rising elution fractionation (TREF) measurement by cross fractionation chromatography (CFC) described later and a high elution peak intensity at the elution peak top temperature.

[0015] That is, the present invention is as follows. [1]

[0017] An ethylene-vinyl acetate copolymer resin, wherein the ethylene-vinyl acetate copolymer resin comprises ethylene units and 3.0% by mass or more and less than 10.0% by mass of vinyl acetate units,

[0018] The ethylene-vinyl acetate copolymer resin has a melt flow rate of 0.1 g / 10 min or more and 1.0 g / 10 min or less under a load of 2.16 kg,

[0019] The elution peak top temperature of the ethylene-vinyl acetate copolymer resin in the elution temperature-elution amount curve obtained by temperature-elution fractionation measurement of cross-fractionation chromatography is 58° C. or higher and 75° C. or lower, and

[0020] dw / dT at the elution peak top temperature is 6 or more and 12 or less. [2]

[0022] The ethylene-vinyl acetate copolymer resin according to [1], wherein the long chain branching degree gL of the ethylene-vinyl acetate copolymer resin is 0.20 or more and 0.35 or less,

[0023] The degree of long-chain branching gL refers to the minimum value among the branching indexes g' obtained by dividing the intrinsic viscosity of a polymer measured using a GPC measuring apparatus equipped with a differential refractometer, a viscosity detector, and a light scattering detector by the intrinsic viscosity of a linear polymer having the same absolute molecular weight as the polymer, within the absolute molecular weight range of 100,000 to 1,000,000 as measured using the GPC measuring apparatus. [3]

[0025] The ethylene-vinyl acetate copolymer resin according to [1] or [2], wherein the cumulative elution amount at 50°C in temperature rising elution fractionation measurement by cross fractionation chromatography of the ethylene-vinyl acetate copolymer resin is 15% by mass or less. [4]

[0027] The ethylene-vinyl acetate copolymer resin according to any one of [1] to [3], wherein the cumulative elution amount at 30°C in temperature rising elution fractionation measurement of cross fractionation chromatography of the ethylene-vinyl acetate copolymer resin is 3.0% by mass or less. [5]

[0029] A molded article comprising the ethylene-vinyl acetate copolymer resin according to any one of [1] to [4]. [6]

[0031] A foam comprising the ethylene-vinyl acetate copolymer resin according to any one of [1] to [4].

[0032] Effects of the Invention

[0033] According to the present invention, there can be provided an ethylene-vinyl acetate copolymer resin which suppresses the generation of connected particles when producing small particles and has desired foaming moldability, and a molded article and a foamed article using the ethylene-vinyl acetate copolymer resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is an example of calculating the elution peak top temperature and dw / dT in the elution temperature-elution amount curve obtained by TREF.

[0035] Figure 2 This is an example of calculating the cumulative elution amount at an elution temperature of 50°C in TREF.

[0036] Figure 3 This is an example of calculating the cumulative elution amount at an elution temperature of 30°C in TREF.

[0037] Figure 4 This is an example of calculating the degree of long-chain branching gL. DETAILED DESCRIPTION

[0038] Hereinafter, an embodiment of the present invention (hereinafter referred to as the present embodiment) will be described in detail, but the present invention is not limited thereto and various modifications can be made without departing from the spirit and scope of the present invention.

[0039] [Ethylene-vinyl acetate copolymer resin]

[0040] The ethylene-vinyl acetate copolymer resin of the present embodiment contains ethylene units and 3.0% by mass or more and less than 10.0% by mass of vinyl acetate units, has a melt flow rate (hereinafter referred to as MFR) of 0.1 g / 10 min or more and 1.0 g / 10 min or less under a load of 2.16 kg, an elution peak top temperature in a temperature rising elution fractionation measurement (hereinafter referred to as TREF) of cross-fractionation chromatography of 58° C. or more and 75° C. or less, and has a dw / dT at the elution peak top temperature of 6 or more and 12 or less.

[0041] The present inventors have conducted intensive research and have found that the ethylene-vinyl acetate copolymer having the above-mentioned structure suppresses the generation of connected particles when producing small particles and has excellent desired foaming properties.

[0042] It should be noted that dw / dT is the mass fraction of polymer eluted per unit temperature in TREF.

[0043] The ethylene-vinyl acetate copolymer resin of the present embodiment may contain other monomer units in addition to ethylene units and vinyl acetate units as needed. Other monomer units are not particularly limited, and examples thereof include α-olefin units derived from propylene, 1-butene, and the like.

[0044] Furthermore, the ethylene-vinyl acetate copolymer resin of the present embodiment may be a resin obtained by dry-blending or melt-blending two or more ethylene-vinyl acetate copolymer resins at any ratio. When two or more ethylene-vinyl acetate copolymer resins are used, the contents of vinyl acetate units and ethylene units relative to the total amount of these resins are preferably within the above-mentioned ranges.

[0045] (vinyl acetate units)

[0046] The content of vinyl acetate units relative to the total amount of the ethylene-vinyl acetate copolymer is 3.0% by mass or greater and less than 10.0% by mass, preferably 3.5% by mass or greater and 9.0% by mass or less, and more preferably 4.0% by mass or greater and 8.0% by mass or less. When the content of vinyl acetate units is within this range, an excellent balance is achieved between the amount of connected particles produced during the production of small particles and compatibility with polystyrene, and the composite foam molded article tends to have an excellent balance between productivity and mechanical properties.

[0047] The method for adjusting the content of vinyl acetate units is not particularly limited, and examples thereof include appropriately adjusting the amount of vinyl acetate monomer added, the polymerization temperature, and the polymerization pressure in the step of polymerizing the ethylene-vinyl acetate copolymer resin.

[0048] The vinyl acetate unit content in an ethylene-vinyl acetate copolymer can be measured by preparing a calibration curve using saponification and potentiometric titration as a standard test method in accordance with JIS K7192:1999, and converting the content to vinyl acetate using infrared spectroscopy as a control test method. More specifically, the content can be measured using the method described in the Examples below.

[0049] (ethylene unit)

[0050] The content of ethylene units in the ethylene-vinyl acetate copolymer is preferably 90.0% by mass or more and less than 97.0% by mass, more preferably 91.0% by mass or more and 96.5% by mass or less, and even more preferably 92.0% by mass or more and 96.0% by mass or less, relative to the total amount of the ethylene-vinyl acetate copolymer. When the content of ethylene units is within this range, there is a tendency to achieve an excellent balance between the amount of connected particles produced during the production of small particles and compatibility with polystyrene, and to achieve an excellent balance between productivity and mechanical properties of the composite foam molded article.

[0051] (MFR)

[0052] The MFR of the ethylene-vinyl acetate copolymer resin of this embodiment is 0.1 g / 10 min to 1.0 g / 10 min, preferably 0.12 g / 10 min to 0.9 g / 10 min, more preferably 0.15 g / 10 min to 0.8 g / 10 min, and even more preferably 0.2 g / 10 min to 0.7 g / 10 min. When the MFR is within this range, there is a tendency for a better balance between the amount of connected particles generated and foaming properties when producing small pellets.

[0053] The method for adjusting the MFR of the ethylene-vinyl acetate copolymer resin is not particularly limited. For example, the method includes adjusting the reaction temperature, reaction pressure, and the type and / or amount of the chain transfer agent during polymerization to obtain the ethylene-vinyl acetate copolymer resin. More specifically, the MFR tends to increase with increasing reaction temperature, decreases with decreasing reaction pressure, and increases in the amount of chain transfer agent tends to increase the MFR.

[0054] In addition, MFR can be measured according to JIS K7210:1999 Code D (temperature = 190°C, load = 2.16 kg).

[0055] (elution peak top temperature in TREF)

[0056] The elution peak top temperature in TREF of the ethylene-vinyl acetate copolymer resin of this embodiment is 58°C to 75°C, preferably 60°C to 72°C, more preferably 62°C to 71°C, and even more preferably 63°C to 70°C. When the elution peak top temperature is within this range, the formation of connected particles during the production of small particles tends to be suppressed, and foaming moldability tends to be maintained.

[0057] The method for adjusting the elution peak top temperature to fall within the above range is not particularly limited, and examples thereof include a method of conducting polymerization while adjusting the MFR and the content of vinyl acetate units to fall within predetermined ranges, a method of suppressing the polymerization rate by using oxygen as a polymerization initiator to thereby uniformly conduct polymerization, a method of suppressing short chain branches by using a lower alkane as a chain transfer agent, and a method of adding water to an extruder during pelletization after polymerization to azeotropically remove low-crystalline components eluting at low temperatures.

[0058] The elution peak top temperature in TREF can be measured by the method described in the Examples below.

[0059] (dw / dT at the elution peak temperature of TREF)

[0060] The dw / dT at the elution peak temperature is 6 or more and 12 or less, preferably 7 or more and 11 or less, more preferably 8 or more and 10 or less, and even more preferably 8.5 or more and 9.5 or less. When the dw / dT at the elution peak temperature is within the above range, there is a tendency to suppress the generation of connected particles during the production of small particles.

[0061] The method for adjusting dw / dT at the elution peak temperature to fall within the above range is not particularly limited, and examples thereof include a method of conducting polymerization while adjusting the MFR and the content of vinyl acetate units to fall within predetermined ranges, a method of suppressing the polymerization rate by using oxygen as a polymerization initiator to thereby uniformly conduct polymerization, a method of suppressing short chain branches by using a lower alkane as a chain transfer agent, and a method of adding water to an extruder during pelletization after polymerization to azeotropically remove low-crystalline components eluting at low temperatures.

[0062] dw / dT at the elution peak top temperature in TREF can be measured by the method described in the Examples below.

[0063] (Degree of long chain branching in high molecular weight body gL)

[0064] The degree of long-chain branching gL in this embodiment is defined as the minimum value among the branching index g' obtained by dividing the intrinsic viscosity of a polymer measured using a GPC measuring apparatus equipped with a differential refractometer, a viscosity detector, and a light scattering detector by the intrinsic viscosity of a linear polymer having the same absolute molecular weight as the polymer, within the absolute molecular weight range of 100,000 to 1,000,000 as measured using the GPC measuring apparatus.

[0065] The degree of long-chain branching gL contained in the ethylene-vinyl acetate copolymer resin of this embodiment is preferably 0.20 or more and 0.35 or less, more preferably 0.22 or more and 0.33 or less, and even more preferably 0.25 or more and 0.30 or less. When gL is within the above range, the polymer structure has a high molecular weight and suppressed long-chain branches, thereby suppressing the melt tension within an appropriate range and tending to have excellent foaming properties.

[0066] Generally, when long chain branches are introduced into a polymer, the radius of inertia decreases compared to a linear polymer of the same molecular weight. Since a smaller radius of inertia corresponds to a smaller intrinsic viscosity, the ratio of the intrinsic viscosity (ηbranch) of a branched polymer to the intrinsic viscosity (ηlinear) of a linear polymer of the same molecular weight (ηbranch / ηlinear) decreases with the introduction of long chain branches. The branching index g' is defined as g' = ηbranch / ηlinear. A branching index g' less than 1 indicates the presence of branching. Lower values ​​of the g' indicate a greater number of introduced branches and a greater number of long chain branches.

[0067] There are no particular limitations on the method for adjusting the degree of long-chain branching gL in the polymer to fall within the above range. Examples include: a method of appropriately adjusting the polymerization temperature and polymerization pressure; a method of not adding an initiator in the late stage of polymerization; or a method of suppressing the long-chain branching reaction in the late stage of the polymerization reaction by diluting the polymerization initiator with a chain transfer agent when adding a polymerization initiator in the late stage of polymerization.

[0068] In addition, the long-chain branching degree gL can be measured by the method described in the Examples mentioned later.

[0069] (Cumulative elution amount at a specific temperature in TREF)

[0070] In this embodiment, the cumulative elution amount at a specific temperature in TREF refers to: in TREF, a sample solution in which a sample is dissolved in a solvent is prepared, the sample solution is introduced into a sample chamber, and then the sample chamber is heated from room temperature to 140°C at a heating rate of 40°C / min, and then maintained for 120 minutes, and then the temperature of the sample chamber is cooled to 30°C at a cooling rate of 0.5°C / min, and then maintained for 20 minutes to allow the sample to precipitate on the surface of the filler in the sample chamber, and then the temperature of the sample chamber and the column is heated from 30°C at a heating rate of 20°C / min. The total mass of the sample eluted during the period from heating from 30°C to reaching the specific temperature.

[0071] (Cumulative elution amount at 50°C in TREF)

[0072] The cumulative elution amount at 50°C in TREF of the ethylene-vinyl acetate copolymer resin of this embodiment is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 9.0% by mass or less. When the cumulative elution amount is within the above range, even for an ethylene-vinyl acetate copolymer resin having a relatively high vinyl acetate unit content, the generation of connected particles during the production of small particles tends to be further suppressed.

[0073] The method for adjusting the cumulative elution amount to fall within the above range is not particularly limited, and examples thereof include a method of performing polymerization while controlling the MFR and the content of vinyl acetate units within predetermined ranges; a method of uniformly performing polymerization by suppressing the polymerization rate by using oxygen as a polymerization initiator; a method of suppressing short chain branches by using a lower alkane as a chain transfer agent; and a method of azeotropically removing low-crystalline components eluted at low temperatures by adding water to an extruder during pelletization after polymerization.

[0074] The cumulative elution amount at 50° C. in TREF can be measured by the method described in the Examples below.

[0075] (Cumulative elution amount at 30°C in TREF)

[0076] Furthermore, the cumulative elution amount at 30°C in TREF of the ethylene-vinyl acetate copolymer resin of this embodiment is preferably 3.0% by mass or less, more preferably 2.5% by mass or less, and even more preferably 2.0% by mass or less. When this cumulative elution amount is within the above range, even for an ethylene-vinyl acetate copolymer resin having a relatively high vinyl acetate unit content, the generation of connected particles during the production of small particles tends to be further suppressed.

[0077] The method for adjusting the cumulative elution amount to fall within the above range is not particularly limited, and examples thereof include a method of performing polymerization while controlling the MFR and the content of vinyl acetate units within predetermined ranges; a method of uniformly performing polymerization by suppressing the polymerization rate by using oxygen as a polymerization initiator; a method of suppressing short chain branches by using a lower alkane as a chain transfer agent; and a method of azeotropically removing low-crystalline components eluted at low temperatures by adding water to an extruder during pelletization after polymerization.

[0078] The cumulative elution amount at 30° C. in TREF can be measured by the method described in the Examples below.

[0079] [Method for producing ethylene-vinyl acetate copolymer resin]

[0080] The ethylene-vinyl acetate copolymer resin of the present embodiment can be obtained, for example, by polymerizing an ethylene monomer and a vinyl acetate monomer under pressure and heating in the presence of a polymerization initiator and a chain transfer agent, but is not particularly limited.

[0081] The polymerization method of the ethylene-vinyl acetate copolymer resin is not particularly limited, and examples thereof include an autoclave method and a tubular method. Of these, the tubular method is preferred from the viewpoint of suppressing the formation of long-chain branches in high molecular weight products.

[0082] The average polymerization temperature is preferably 150° C. to 280° C., more preferably 180° C. to 240° C. The average polymerization pressure is preferably 100 MPa to 350 MPa, more preferably 120 MPa to 280 MPa, and even more preferably 180 MPa to 270 MPa.

[0083] It should be noted that the reactor has multiple locations for adding ethylene monomer, vinyl acetate monomer, and polymerization initiator. Hereinafter, in this embodiment, the front section of the reactor refers to the location where the ratio (B / A) of the straight-line distance (B) from the reactor inlet to a predetermined location to the overall reactor length (A) is greater than or equal to 0% and less than 10%. The middle section of the reactor refers to the location where the above B / A is greater than or equal to 10% and less than 40%. The rear section of the reactor refers to the location where the above B / A is greater than or equal to 40% and less than 70%.

[0084] The ethylene monomer and vinyl acetate monomer supplied to the reactor may be in a gaseous state or a liquid state, but are preferably in a gaseous state (gas).

[0085] The polymerization initiator is not particularly limited, and examples thereof include oxygen contained in the air, oxygen purified from the air, and commercially available free radical initiators. The free radical initiator is not particularly limited, and examples thereof include tert-butyl peroxypivalate (TBPP), tert-butyl peroxy-2-ethylhexanoate (TBPO), tert-butyl peroxyacetate (TPA), and di-tert-butyl peroxide (DTBP).

[0086] The polymerization initiator in the front section of the reactor preferably contains oxygen. The presence of oxygen can reduce the reaction rate immediately after the start of polymerization, and tends to produce an ethylene-vinyl acetate copolymer resin containing a large number of crystalline parts more uniformly through a uniform polymerization reaction.

[0087] The chain transfer agent is not particularly limited, and examples thereof include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol; lower alkanes such as ethane, propane, and butane; and ketones or aldehydes such as acetone, methyl ethyl ketone, diisobutyl ketone, methyl isopropyl ketone, formaldehyde, and acetaldehyde.

[0088] Among them, butane is preferred as a chain transfer agent. It is more preferred to add it in stages throughout the front, middle, and back sections of the reactor. In this case, it is more preferred to add it to the back section of the reactor simultaneously to dilute the polymerization initiator. The use of butane tends to facilitate the formation of crystalline portions in the polymer, and the staged addition throughout the reactor tends to facilitate the formation of crystalline portions uniformly.

[0089] Furthermore, when the polymerization initiator is added at the latter stage of the reactor, a reaction that generates long chain branches in the high molecular weight product tends to occur easily. Therefore, by mixing it with the initiator and adding it at the same site, the reaction that generates long chain branches tends to be suppressed.

[0090] The ethylene-vinyl acetate copolymer resin obtained by polymerization in the above manner is subjected to pressure reduction in a high-pressure separator and a low-pressure separator to separate the unreacted raw materials and the ethylene-vinyl acetate copolymer resin. The molten ethylene-vinyl acetate copolymer is then granulated into pellets using an extruder. In this case, an extruder equipped with a venting mechanism is preferably used, and it is preferable to add water and remove low-crystalline components by azeotropic distillation.

[0091] In the high-pressure separator and the low-pressure separator, the molten ethylene-vinyl acetate copolymer resin and the unreacted gases such as ethylene gas and vinyl acetate gas serving as raw materials exist in the form of a gas-liquid mixed fluid. The unreacted gas can be recovered from the upper part of the container of each separator and reused in the polymerization reaction.

[0092] The ethylene-vinyl acetate copolymer resin of the present embodiment may contain known additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, an antifogging agent, and a coloring pigment as needed, but is not particularly limited.

[0093] The antioxidant is not particularly limited, and examples thereof include phenolic antioxidants such as 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; phosphorus-containing antioxidants such as tris(2,4-di-tert-butylphenyl) phosphite and tetrakis(2,4-di-tert-butylphenyl)-4,4-biphenylenediphosphite; phosphorus-containing / phenolic antioxidants such as 6-tert-butyl-4-[3-(2,4,8,10-tetra-tert-butyldibenzo[d,f]][1,3,2]dioxaphosphep-6-yloxy)propyl]-o-cresol; and sulfur-containing antioxidants such as dilauryl thiodipropionate.

[0094] [Molding]

[0095] The molded article of the present embodiment comprises the above-mentioned ethylene-vinyl acetate copolymer resin. There are no particular restrictions on the molded article of the present embodiment. For example, it can be obtained by known injection molding, extrusion molding or stretch molding, and can be appropriately used for various purposes. As such uses, specifically, there are no particular restrictions. For example, artificial turf mats, automobile fenders, fender covers, drainage hoses, etc. can be cited. In addition, it can also be used as fibers, etc.

[0096] [Foam]

[0097] The foam of this embodiment contains the above-mentioned ethylene-vinyl acetate copolymer resin, and may further contain other components in addition to the ethylene-vinyl acetate copolymer resin as needed. As other components, there are no particular restrictions, for example, they may include: ethylene-α-olefin block copolymer (OBC); ethylene-α-olefin random copolymer (POE); fluoropolymers such as fluororesins and fluororubbers; polyamide resins such as polyamide 6, polyamide 11, polyamide 12, polyamide 6,6, and polyamide 610, polyamide elastomers and other polyamide polymers; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyvinyl chloride resin; acrylic resins such as polymethyl methacrylate; polysiloxane elastomers, ethylene propylene rubber (EPR), ethylene propylene diene monomer rubber (EPDM), butadiene rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), natural rubber (NR), styrene-butadiene rubber (SR), styrene-butadiene rubber (SR), ethylene propylene diene monomer (EPDM ... Polyethylene resins such as low-density polyethylene resin (LDPE), linear low-density polyethylene resin (LLDPE), and high-density polyethylene resin (HDPE); polypropylene resins such as propylene homopolymer (homoPP), random polypropylene resin (random PP), and segmented polypropylene resin (block PP); cyclic olefin polymers (COP) and cyclic olefin copolymers (COC); polyurethane polymers such as polyester polyurethane resin and polyether polyurethane resin; styrene polymers such as polystyrene resin, acrylonitrile-styrene resin (AS resin), acrylonitrile-butadiene-styrene resin (ABS resin), and styrene thermoplastic elastomer (TPS).

[0098] In addition, the above-mentioned styrene-based thermoplastic elastomer (TPS) is not particularly limited, and examples thereof include: styrene-ethylene-butylene copolymer (SEB), styrene-butadiene-styrene copolymer (SBS), a hydrogenated product of SBS (styrene-ethylene-butylene-styrene copolymer (SEBS)), styrene-isoprene-styrene copolymer (SIS), a hydrogenated product of SIS (styrene-ethylene-propylene-styrene copolymer (SEPS)), styrene-butadiene-isoprene-styrene copolymer (SBIS), a hydrogenated product of SBIS (styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS)), styrene-isobutylene-styrene copolymer (SIBS), styrene-butadiene-styrene-butadiene copolymer (SBSB), and styrene-butadiene-styrene-butadiene-styrene copolymer (SBSBS).

[0099] The foam of this embodiment can be used in a wide range of industrial fields such as insulation materials and cushioning materials by a known method. As a method for producing the foam of this embodiment, it is particularly preferred to produce a composite foam molding by compounding an ethylene-vinyl acetate copolymer resin with a polystyrene resin by the above-mentioned method. It is more preferred to produce a composite foam molding by compounding by polymerizing a styrene monomer in the presence of an ethylene-vinyl acetate copolymer resin.

[0100] [Example]

[0101] Hereinafter, the present invention will be described in detail using Examples and Comparative Examples. However, the present embodiment is not limited to the following Examples and Comparative Examples.

[0102] [Determination of vinyl acetate unit content]

[0103] In accordance with JIS K7192:1999, as a reference test method, a calibration curve was prepared by saponification and potentiometric titration using an ethylene-vinyl acetate copolymer resin having a known vinyl acetate unit content. As a control test method, the vinyl acetate unit content (VA content) in the ethylene-vinyl acetate copolymer resins obtained in Examples and Comparative Examples was measured by infrared spectroscopy.

[0104] [Melt flow rate (MFR) measurement]

[0105] The MFR of the ethylene-vinyl acetate copolymer resin was measured in accordance with JIS K7210: 1999 Code D (temperature = 190°C, load = 2.16 kg).

[0106] [Temperature Rising Elution Fractionation (TREF) in Cross-Fraction Chromatography]

[0107] The elution temperature-elution amount curve obtained by TREF measurement was measured as follows to determine the temperature at which the local elution per unit temperature of the ethylene-vinyl acetate copolymer as a sample reaches a maximum, that is, the elution peak temperature, dw / dT at the elution peak temperature, the cumulative elution amount at an elution temperature of 50°C, and the cumulative elution amount at an elution temperature of 30°C.

[0108] First, prepare a sample solution by dissolving 20 mg of ethylene-vinyl acetate copolymer resin in 0.5 mL of o-dichlorobenzene, and introduce this sample solution into the sample chamber. The sample chamber is then heated from room temperature to 140°C at a heating rate of 40°C / minute and held for 120 minutes. Next, the temperature of the sample chamber is lowered to 30°C at a cooling rate of 0.5°C / minute and held for 20 minutes to allow the sample to precipitate on the surface of the filler in the sample chamber. Next, the temperature of the sample chamber and column is sequentially raised from 30°C to 120°C at a heating rate of 20°C / minute. During the heating process, each specified measurement temperature is maintained for 21 minutes before the temperature is raised to the next measurement temperature.

[0109] Thus, the concentration of the sample, i.e., the ethylene-vinyl acetate copolymer resin, eluted at each measurement temperature was detected. Then, an elution temperature-elution amount curve was created based on the mass fraction (mass %) of the sample eluted amount and the corresponding column temperature (°C), and the elution amount of the sample at each measurement temperature was determined.

[0110] The measurement conditions are as follows.

[0111] Equipment: Automated 3D analyzer CFC-2 manufactured by Polymer Char

[0112] Column: Stainless steel microsphere column (3 / 8 inch outer diameter, 150 mm length)

[0113] Eluent: o-dichlorobenzene (for high performance liquid chromatography)

[0114] Sample solution concentration: Sample (ethylene-vinyl acetate copolymer resin) 20 mg / o-dichlorobenzene 0.5 mL

[0115] Injection volume: 0.5 mL

[0116] Pump flow rate: 1.0mL / min

[0117] Detector: Infrared spectrophotometer IR4 manufactured by Polymer Char

[0118] Detection wave number: 3.42μm

[0119] [Calculation of gL by 3D-GPC measurement]

[0120] As a GPC apparatus having a differential refractometer (RI), a viscosity detector (Viscometer) and a light scattering detector, Alliance GPCV2000 from Waters was used. In addition, as a light scattering detector, DAWN-E from Wyatt Technology, which is a multi-angle laser light scattering detector (MALLS), was used. The detectors were connected in the order of MALLS, RI, and Viscometer. The mobile phase solvent was 1,2,4-trichlorobenzene (with the antioxidant Irganox1076 added at a concentration of 0.5 mg / mL). The flow rate was 1 mL / min. As a column, two GMHHR-H(S)·HT from Tosoh Corporation were connected and used. The temperature of the column, the injection part and each detector was 140°C. The sample concentration was set to 1 mg / mL. The injection volume (sample loop capacity) was 0.2175 mL.

[0121] When determining the absolute molecular weight (M) obtained by MALLS and the intrinsic viscosity ([η]) obtained by Viscometer, the data processing software ASTRA (version 4.73.04) included with MALLS was used.

[0122] The branching index (g') is calculated as the ratio (ηbranch / ηlinear) of the intrinsic viscosity (ηbranch) obtained by measuring the sample using the above-mentioned Viscometer to the intrinsic viscosity (ηlinear) obtained by separately measuring a linear polymer having the same absolute molecular weight (M) as the polymer contained in the sample. The minimum value of the above g' within the molecular weight range of 100,000 to 1,000,000 based on the absolute molecular weight obtained by MALLS is defined as gL.

[0123] [Foaming moldability index]

[0124] The melt tension (mN) was measured using Capilograph 1D manufactured by Toyo Seiki Co., Ltd. under the following conditions.

[0125] Barrel diameter: 9.55mm

[0126] Hole diameter: 2.095mm

[0127] Hole length: 7.98mm

[0128] Inflow angle: 90 degrees

[0129] Temperature: 190°C

[0130] Piston speed: 6mm / min

[0131] Pulling speed: 2mm / min

[0132] The foaming moldability was evaluated based on the following indices.

[0133] ○: greater than or equal to 80mN and less than 120mN

[0134] △: 60mN or more and less than 80mN or 120mN or more and less than 130mN

[0135] ×: 130 mN or more (no foaming)

[0136] [Amount of connected particles generated]

[0137] Ethylene-vinyl acetate copolymer resin was melt-kneaded using a 20 mm single-screw extruder and pelletized by underwater cutting to obtain pellets. The rotation speed was adjusted so that 100 pellets of the ethylene-vinyl acetate copolymer resin pellets weighed 40 mg.

[0138] 100 g of the obtained small pellets were visually confirmed, and the connected particles were removed. The mass of the connected particles in the pellets was measured. Based on the mass ratio, the amount of connected particles generated during the production of small pellets was evaluated using the following indicators.

[0139] ○: less than 1%

[0140] △: greater than or equal to 1% and less than 10%

[0141] ×: 10% or more

[0142] [Comprehensive evaluation]

[0143] Based on the results of the amount of connected particles generated and foam moldability, comprehensive evaluation was performed as follows.

[0144] ◎: 0 means 2

[0145] 0: 0 is 1, △ is 1

[0146] △: △ is 2

[0147] ×: There is at least one ×

[0148] [Example 1]

[0149] The monomers were prepared in an amount of 1.90 mol% relative to the amount of ethylene monomer and vinyl acetate monomer. The monomers and polymerization initiator were added to the tubular reactor in stages, at the front, middle, and back stages, and polymerization was initiated. Compressed air (oxygen concentration of 21%) was used as the initiator in the front stage, an initiator with a ratio of TBPO:DTBP = 3:7 was used in the middle stage, and an initiator with a ratio of TBPO:DTBP:butane = 3:6:1 was used in the back stage. The average polymerization temperature was set to 230°C, the average polymerization pressure was set to 220 MPa, and the average butane concentration was set to 0.5 mol%, and the polymerization was completed. After the polymerization, the mixture was introduced into a high-pressure separator and a low-pressure separator in sequence to separate the mixture into ethylene-vinyl acetate copolymer resin and a gas containing residual monomers. The resulting melt of the ethylene-vinyl acetate copolymer resin was fed into an extruder and pelletized to obtain an ethylene-vinyl acetate copolymer resin.

[0150] [Example 2]

[0151] Polymerization was carried out in the same manner as in Example 1 under the conditions shown in Table 1, except that water was added so as to account for 0.5% by weight relative to the melt of the ethylene-vinyl acetate copolymer resin and the extruder was operated at -0.009 MPa (indicated as water-degassing extrusion in Tables 1 and 2), followed by granulation to obtain the ethylene-vinyl acetate copolymer resin of Example 2.

[0152] [Examples 3 to 8 and Comparative Examples 1 to 7]

[0153] Ethylene-vinyl acetate copolymer resins of Examples 3 to 8 and Comparative Examples 1 to 7 were obtained by the same operation as in Example 1 and Example 2 except that the conditions were changed to those shown in Tables 1 and 2, respectively.

[0154] The physical properties and characteristics of the obtained ethylene-vinyl acetate copolymer resin were measured by the methods shown above, and the measurement results are summarized in Tables 3 and 4.

[0155]

[0156]

[0157]

[0158]

Claims

1. An ethylene-vinyl acetate copolymer resin, wherein The ethylene-vinyl acetate copolymer resin comprises ethylene units and 3.5% by mass or more and 9.1% by mass or less of vinyl acetate units, The ethylene-vinyl acetate copolymer resin has a melt flow rate of 0.1 g / 10 min or more and 1.0 g / 10 min or less under the conditions of a temperature of 190° C. and a load of 2.16 kg, The elution peak top temperature of the ethylene-vinyl acetate copolymer resin in the elution temperature-elution amount curve obtained by temperature-elution fractionation measurement of cross-fractionation chromatography is 60° C. or higher and 72° C. or lower, and The dw / dT at the elution peak top temperature is 8.0 or more and 11.0 or less, wherein the dw / dT is the mass fraction of the polymer eluted per unit temperature in the temperature-eluting fractionation measurement of cross-fractionation chromatography, The temperature-elution fractionation determination of the cross-fractionation chromatography is carried out in the following manner: A sample solution was prepared by dissolving 20 mg of ethylene-vinyl acetate copolymer resin in 0.5 mL of o-dichlorobenzene. This sample solution was introduced into a sample chamber. The sample chamber was then heated from room temperature to 140°C at a heating rate of 40°C / min and held for 120 minutes. The temperature of the sample chamber was then lowered to 30°C at a cooling rate of 0.5°C / min and held for 20 minutes to allow the sample to precipitate on the surface of the filler in the sample chamber. The temperature of the sample chamber and column was then sequentially raised from 30°C to 120°C at a heating rate of 20°C / min. During the heating, the corresponding temperature was held at each specified measurement temperature for 21 minutes before the temperature was raised to the next measurement temperature. The concentration of the sample eluted at each measurement temperature, i.e., the ethylene-vinyl acetate copolymer resin, was thus detected. An elution temperature-elution amount curve was then created based on the mass fraction (mass %) of the sample elution amount and the corresponding column temperature (°C). The elution amount of the sample at each measurement temperature was determined. The measurement conditions are as follows: Column: stainless steel microsphere column Eluent: o-dichlorobenzene Injection volume: 0.5 mL Pump flow rate: 1.0mL / min Detector: infrared spectrophotometer.

2. The ethylene-vinyl acetate copolymer resin according to claim 1, wherein The content of the vinyl acetate unit is 3.5% by mass or more and 9.0% by mass or less relative to the total amount of the ethylene-vinyl acetate copolymer.

3. The ethylene-vinyl acetate copolymer resin according to claim 1 or 2, wherein The content of the vinyl acetate unit is 4.0% by mass or more and 8.0% by mass or less relative to the total amount of the ethylene-vinyl acetate copolymer.

4. The ethylene-vinyl acetate copolymer resin according to claim 1 or 2, wherein The ethylene-vinyl acetate copolymer resin has a melt flow rate of 0.12 g / 10 min or more and 0.9 g / 10 min or less under conditions of a temperature of 190° C. and a load of 2.16 kg.

5. The ethylene-vinyl acetate copolymer resin according to claim 1 or 2, wherein The ethylene-vinyl acetate copolymer resin has a melt flow rate of 0.15 g / 10 min or more and 0.8 g / 10 min or less under conditions of a temperature of 190° C. and a load of 2.16 kg.

6. The ethylene-vinyl acetate copolymer resin according to claim 1 or 2, wherein The ethylene-vinyl acetate copolymer resin has a melt flow rate of 0.2 g / 10 min or more and 0.7 g / 10 min or less under conditions of a temperature of 190° C. and a load of 2.16 kg.

7. The ethylene-vinyl acetate copolymer resin according to claim 1 or 2, wherein The elution peak top temperature is 62° C. or higher and 71° C. or lower.

8. The ethylene-vinyl acetate copolymer resin according to claim 1 or 2, wherein The elution peak top temperature is 63° C. or higher and 70° C. or lower.

9. The ethylene-vinyl acetate copolymer resin according to claim 1 or 2, wherein dw / dT at the elution peak top temperature is 8 or more and 10 or less.

10. The ethylene-vinyl acetate copolymer resin according to claim 1 or 2, wherein dw / dT at the elution peak top temperature is 8.5 or more and 9.5 or less.

11. The ethylene-vinyl acetate copolymer resin according to claim 1 or 2, wherein The ethylene-vinyl acetate copolymer resin has a long chain branching degree gL of 0.20 or more and 0.35 or less, The degree of long-chain branching gL refers to the minimum value among the branching indexes g' obtained by dividing the intrinsic viscosity of a polymer measured using a GPC measuring apparatus equipped with a differential refractometer, a viscosity detector, and a light scattering detector by the intrinsic viscosity of a linear polymer having the same absolute molecular weight as the polymer, within the absolute molecular weight range of 100,000 to 1,000,000 as measured using the GPC measuring apparatus.

12. The ethylene-vinyl acetate copolymer resin according to claim 11, wherein The ethylene-vinyl acetate copolymer resin has a degree of long-chain branching gL of 0.22 or more and 0.33 or less.

13. The ethylene-vinyl acetate copolymer resin according to claim 11, wherein The ethylene-vinyl acetate copolymer resin has a degree of long-chain branching gL of 0.25 or more and 0.30 or less.

14. The ethylene-vinyl acetate copolymer resin according to claim 1 or 2, wherein The ethylene-vinyl acetate copolymer resin has a cumulative elution amount of 15% by mass or less at 50° C. in temperature-elution fractionation measurement using cross-fractionation chromatography.

15. The ethylene-vinyl acetate copolymer resin according to claim 14, wherein The ethylene-vinyl acetate copolymer resin has a cumulative elution amount of 12% by mass or less at 50° C. in temperature-elution fractionation measurement using cross-fractionation chromatography.

16. The ethylene-vinyl acetate copolymer resin according to claim 14, wherein The ethylene-vinyl acetate copolymer resin has a cumulative elution amount of 9.0% by mass or less at 50° C. in temperature-elution fractionation measurement using cross-fractionation chromatography.

17. The ethylene-vinyl acetate copolymer resin according to claim 1 or 2, wherein The ethylene-vinyl acetate copolymer resin has a cumulative elution amount of 3.0% by mass or less at 30° C. in temperature-elution fractionation measurement using cross-fractionation chromatography.

18. The ethylene-vinyl acetate copolymer resin according to claim 17, wherein The ethylene-vinyl acetate copolymer resin has a cumulative elution amount of 2.5% by mass or less at 30° C. in temperature-elution fractionation measurement using cross-fractionation chromatography.

19. The ethylene-vinyl acetate copolymer resin according to claim 17, wherein The ethylene-vinyl acetate copolymer resin has a cumulative elution amount of 2.0% by mass or less at 30° C. in temperature-elution fractionation measurement using cross-fractionation chromatography.

20. The ethylene-vinyl acetate copolymer resin according to claim 1 or 2, wherein The ethylene-vinyl acetate copolymer resin was evaluated as 0 or △ in the evaluation of foam moldability, ○: Melt tension is greater than or equal to 80mN and less than 120mN; Δ: Melt tension is 60 mN or more and less than 80 mN or 120 mN or more and less than 130 mN.

21. A molded article, wherein The molded article comprises the ethylene-vinyl acetate copolymer resin according to any one of claims 1 to 20.

22. A foam, wherein: The foam comprises the ethylene-vinyl acetate copolymer resin according to any one of claims 1 to 20.

23. The foam according to claim 22, wherein The foam further comprises a styrenic polymer.

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