Ethylene-vinyl acetate copolymers and molded bodies, sheets and foams containing the same

Abstract

An object of the present application is to provide an ethylene-vinyl acetate copolymer which is excellent in impact strength, environmental stress cracking resistance, mold releasability, and transparency, and a molded body, a sheet, and a foam containing the same. An ethylene-vinyl acetate copolymer containing ethylene units and 11% by mass or more and 25% by mass or less of vinyl acetate units, and in which, when a molecular weight distribution and an absorbance I (‑CH2‑) attributable to methylene, an absorbance I (‑C＝O) attributable to carbonyl, and an absorbance I (‑CH3‑) attributable to methyl per unit of molecular weight are determined by GPC-FTIR, a slope P of a least square approximation straight line relationship of an absorbance ratio (I i(‑C＝O) / I i(‑CH2‑) ) with respect to a logarithm log(M i ) of each molecular weight M i in a half peak width region of the molecular weight distribution is 0.00 ≤ P ≤ 1.40, and an average Q of the absorbance ratio (I i(‑CH3) / I i(‑CH2‑) ) of each molecular weight M i in the half peak width region of the molecular weight distribution is 23.0 ≤ Q ≤ 30.0.

Description

TECHNICAL FIELD

[0001] The present application relates to an ethylene-vinyl acetate copolymer and a molded body, a sheet and a foam containing the same. BACKGROUND

[0002] The ethylene-vinyl acetate copolymer is excellent in properties such as transparency, softness, mechanical strength, electrical insulation, weather resistance, durability, and thus is used for artificial turf mat, automobile fender, drain hose and the like by injection molding or extrusion molding, and is processed into a single layer film or a laminated film by blown film or T-die film and the like, and is used for agricultural polyolefin film, automobile fender cover and the like in a wide industrial field.

[0003] As a film using the ethylene-vinyl acetate copolymer, for example, an ethylene-vinyl acetate copolymer film having high tear strength, heat retention even with high vinyl acetate content is proposed in Patent Literature 1.

[0004] PRIOR ART DOCUMENT

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2004-161881 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, with an increase in the vinyl acetate content, the ethylene-vinyl acetate copolymer has a tendency to have a lowered crystallization temperature and lowered mold release property, on the other hand, the transparency, softness, and adhesiveness are improved.

[0009] In recent years, as the use field of the ethylene-vinyl acetate copolymer is expanded, the market requires higher performance, and as a specific required performance, high transparency for improving the appearance design property, high environmental stress cracking resistance (hereinafter also referred to as "ESCR") in that it does not cause environmental stress cracking and cracking when left in a chemical under a constant stress application state, and high falling dart impact strength are required.

[0010] Generally, as a method for improving the ESCR, a method for increasing the molecular weight of the ethylene-vinyl acetate copolymer, a method for increasing the vinyl acetate content can be listed, but in the case of increasing the molecular weight, the processability is lowered, and in the case of increasing the vinyl acetate content, the mold release property has a tendency to be lowered as described above. Therefore, an ethylene-vinyl acetate copolymer excellent in the mold release property and the ESCR is required.

[0011] Regarding the ethylene-vinyl acetate copolymer film described in Patent Document 1, the higher the molecular weight of the ethylene-vinyl acetate copolymer, the lower the vinyl acetate content at each molecular weight. Therefore, there is room for improvement in transparency and ESCR.

[0012] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an ethylene-vinyl acetate copolymer having excellent impact strength, environmental stress cracking resistance, releasability and transparency, and a molded article, sheet and foam containing the ethylene-vinyl acetate copolymer.

[0013] Means used to solve problems

[0014] The present inventors have conducted intensive research to solve the above-mentioned problems. As a result, they have discovered that the above-mentioned problems can be solved by an ethylene-vinyl acetate copolymer having a predetermined number of branches and in which the proportion of vinyl acetate units remains constant or tends to increase as the molecular weight distribution changes from low molecular weight components to high molecular weight components. This has led to the completion of the present invention.

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

[0016] [1] An ethylene-vinyl acetate copolymer, wherein the ethylene-vinyl acetate copolymer contains ethylene units and 11% by mass or more and 25% by mass or less of vinyl acetate units, and

[0017] The molecular weight distribution and the absorbance attributable to the methylene group for each molecular weight were measured using GPC-FTIR. (-CH2-) , absorbance attributed to carbonyl group I (-C＝O) and the absorbance attributed to the methyl group I (-CH3-) hour,

[0018] In the half-peak width region of the molecular weight distribution, relative to each molecular weight M i Logarithm of log(M i ) absorbance ratio (I i(-C＝O) / I i(-CH2-) ) has a slope P of the least squares approximate linear relationship of 0.00≤P≤1.40, and

[0019] In the half-peak width region of the molecular weight distribution, each molecular weight M i The absorbance ratio (I i(-CH3) / I i(-CH2-) ) has an average value Q of 23.0≤Q≤30.0.

[0020] [2] The ethylene-vinyl acetate copolymer according to [1], wherein 13 The methyl branch content (20.07 ppm) of the ethylene-vinyl acetate copolymer determined by C-NMR was less than 0.16 / 100C.

[0021] [3] The ethylene-vinyl acetate copolymer according to [1] or [2], wherein the heat of fusion (ΔH) of the ethylene-vinyl acetate copolymer determined by differential scanning calorimetry is 43 J / g or more and 90 J / g or less.

[0022] [4] The ethylene-vinyl acetate copolymer according to any one of [1] to [3], wherein the melt flow rate of the ethylene-vinyl acetate copolymer is greater than or equal to 0.1 g / 10 min and less than 30 g / 10 min.

[0023] [5] A molded article comprising the ethylene-vinyl acetate copolymer according to any one of [1] to [4].

[0024] [6] A sheet comprising the ethylene-vinyl acetate copolymer according to any one of [1] to [4].

[0025] [7] A foam comprising the ethylene-vinyl acetate copolymer according to any one of [1] to [4].

[0026] Effects of the Invention

[0027] According to the present invention, there are provided an ethylene-vinyl acetate copolymer having excellent drop impact strength, environmental stress cracking resistance, releasability, and transparency, and a molded article, sheet, and foam containing the ethylene-vinyl acetate copolymer. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram for explaining the slope P measured by GPC-FTIR.

[0029] Figure 2 This is a schematic diagram for explaining the average value Q measured by GPC-FTIR.

[0030] Figure 3 Schematic diagram for explaining the temperature from the inlet to the outlet of the reactor. DETAILED DESCRIPTION

[0031] Hereinafter, an embodiment of the present invention (hereinafter referred to as “this 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.

[0032] [Ethylene-vinyl acetate copolymer]

[0033] The ethylene-vinyl acetate copolymer of the present embodiment contains ethylene units and 11% by mass or more and 25% by mass or less of vinyl acetate units, and the molecular weight distribution and the absorbance I attributable to the methylene group per molecular weight are measured by GPC-FTIR. (-CH2-) , absorbance attributed to carbonyl group I (-C＝O) and the absorbance attributed to the methyl group I (-CH3-) When, in the half-peak width region of the molecular weight distribution, relative to each molecular weight M i Logarithm of log(M i ) absorbance ratio (I i(-C＝O) / I i(-CH2-) ) is 0.00≤P≤1.40, and in the half-peak width region of the molecular weight distribution, each molecular weight M i The absorbance ratio (I i(-CH3) / I i(-CH2-) ) has an average value Q of 23.0≤Q≤30.0.

[0034] The present inventors have conducted extensive research and have discovered that the drop weight impact strength, environmental stress cracking resistance, mold release properties, and transparency can be further improved by including a large number of vinyl acetate units in the high molecular weight component of the ethylene-vinyl acetate copolymer and by having a large number of branches. The reasons for this are not particularly limited, but are believed to be as follows.

[0035] When the high molecular weight component of an ethylene-vinyl acetate copolymer contains a large number of vinyl acetate units, the crystallinity tends to decrease due to steric hindrance of the molecular chain, and the proportion of amorphous components in the ethylene-vinyl acetate copolymer increases. It is believed that when the proportion of amorphous components increases, the flexibility of the ethylene-vinyl acetate copolymer increases, the environmental stress cracking resistance of the resulting molded article further improves, and the transparency further improves.

[0036] Furthermore, when the high molecular weight component of the ethylene-vinyl acetate copolymer contains a large number of vinyl acetate units, the molecular chains tend to become more entangled, and the melt tension of the ethylene-vinyl acetate copolymer increases. It is believed that when the melt tension increases, the molecular chains are more easily oriented during injection molding, and the resulting molded article exhibits further improved drop weight impact strength.

[0037] Furthermore, it is considered that when the number of branches of the ethylene-vinyl acetate copolymer is large, the entanglement of the molecular chains increases, and thus the crystallinity decreases, and the releasability and transparency of the obtained molded article are further improved.

[0038] In the present embodiment, GPC-FTIR is used to determine that a large number of vinyl acetate units are contained in the high molecular weight component of the ethylene-vinyl acetate copolymer and that the number of branches of the ethylene-vinyl acetate copolymer is large.

[0039] GPC-FTIR is a system that incorporates an FTIR instrument downstream of the GPC column. This allows for simultaneous molecular weight measurement by GPC and compositional analysis of samples eluted from the column using IR. This allows for measurement of, for example, changes in the monomer copolymerization ratio from the high molecular weight side to the low molecular weight side of the GPC chart.

[0040] In this GPC-FTIR, quantitative analysis of sample composition is usually performed by the intensity ratio of absorbance. For example, the absorbance I attributed to methylene in a certain molecular weight fraction is used to determine the relative absorbance of the sample. (-CH2-) and the absorbance attributed to the carbonyl group I (-C＝O) By comparing the absorbance ratio of the fractions, it is possible to evaluate whether the fraction contains more or fewer carbonyl groups based on the methylene group. In addition, by comparing the absorbance ratios of multiple fractions with different molecular weights, it is possible to evaluate whether the high molecular weight side or the low molecular weight side contains more or fewer carbonyl groups.

[0041] Hereinafter, the ethylene-vinyl acetate copolymer according to the present embodiment will be described in detail.

[0042] (Slope P)

[0043] Figure 1 A schematic diagram for explaining the slope P measured by GPC-FTIR is shown in FIG. Figure 1 In the figure, the left vertical axis represents the detection intensity of the copolymer in GPC, and the right vertical axis represents the absorbance ratio (I (-C＝O) / I (-CH2-) ). Moreover, the horizontal axis represents the molecular weight of the copolymer in logarithmic terms.

[0044] The slope P is defined as: the half-peak width of the molecular weight distribution relative to the molecular weight M i Logarithm of log(M i ) absorbance ratio (I i(-C＝O) / I i(-CH2-) ) is the slope of the least squares approximate linear relationship. i(-C＝O) / I i(-CH2-) ) is the absorbance attributed to the carbonyl group I i(-C＝O) and the absorbance attributed to methylene I i(-CH2-) The ratio represents the content ratio of carbonyl groups at each molecular weight of the ethylene-vinyl acetate copolymer.

[0045] Here, for example, the slope P being 0 or positive means that the proportion of the vinyl acetate unit is constant or tends to increase as the copolymer of the present embodiment changes from the low molecular weight component to the high molecular weight component of the molecular weight distribution. In other words, the slope P can also be referred to as a parameter indicating the distribution of the vinyl acetate unit (carbonyl group) in the molecular weight distribution.

[0046] As described above, the slope P being 0 or positive means that the vinyl acetate is selectively introduced into the high molecular weight component, which is important in the ethylene-vinyl acetate copolymer for exhibiting mechanical properties. Since the molecular weight of the vinyl acetate is larger than that of ethylene, the content of the vinyl acetate unit in the high molecular weight component is high, and there is a tendency to have a decrease in crystallinity due to steric hindrance of the molecular chain. Thus, even if the content of the vinyl acetate unit is equivalent as a whole, the ethylene-vinyl acetate copolymer having the slope P of 0 or positive has a higher proportion of amorphous component. Therefore, the environmental stress cracking resistance and transparency of the obtained molded article are further improved. In addition, the entanglement of the molecular chain of the ethylene-vinyl acetate copolymer having the slope P of 0 or positive is stronger, and thus the melt tension is improved, and therefore the orientation of the molecular chain is facilitated by injection molding or the like, and the falling dart impact strength of the obtained molded body is improved.

[0047] Here, the half peak width means the width of the peak having an intensity of half (1 / 2A) of the peak top height A in the peak of the molecular weight distribution. By defining the slope P in the half peak width region, it is possible to express the increasing tendency of the vinyl acetate unit without being affected by the detection error of the edge region of the peak of the molecular weight distribution. The same is also true for the average value Q described later.

[0048] In addition, the slope P is expressed as the slope of the following least square approximation linear relationship formula, and by expressing the relationship between the logarithm log(M i ) of each molecular weight M i and the absorbance ratio (I i(-C＝O) / I i(-CH2-) ) with respect to the molecular weight distribution as such an approximate straight line, it is possible to express the increasing / decreasing tendency of the vinyl acetate unit in the molecular weight distribution. Note that "a" is a constant in the following formula.

[0049] Absorbance ratio (I i(-C＝O) / I i(-CH2-) ) = slope P x log(M i ) + a

[0050] In the present embodiment, the above-mentioned slope P is 0.00 ≤ P ≤ 1.40, preferably 0.05 ≤ P ≤ 1.30, and more preferably 0.10 ≤ P ≤ 1.20. By the slope P being 0.00 or more, the ethylene-vinyl acetate copolymer contains a larger amount of vinyl acetate units in the high molecular weight component, and the falling dart impact strength, environmental stress cracking resistance, and transparency of the obtained molded body or the like are further improved. In addition, by the slope P being 1.40 or less, the mold release property of the obtained molded body or the like is further improved.

[0051] As a method for adjusting the slope P to the above-mentioned range, there is no particular limitation, and for example, a method in which the ethylene-vinyl acetate copolymer is polymerized using a tubular reactor, and the polymerization peak temperature is gradually decreased from the upstream to the downstream of the tubular reactor can be considered. Figure 3 A schematic diagram for explaining the temperature from the inlet to the outlet of the reactor is shown in FIG. 1. When the initiator is added after the addition of ethylene and vinyl acetate in the reactor, the temperature in the reactor rises due to the heat of polymerization, and the temperature rise is decreased by cooling the reactor. When the temperature at which the polymerization temperature is the highest at this time is taken as the polymerization peak temperature, the polymerization peak temperature on the downstream side is lower than that on the upstream side. It is considered that this is because, in the case where the polymerization temperature is high, the polymerization of ethylene is preferentially performed compared to the polymerization of vinyl acetate, and as the polymerization temperature becomes low, the polymerization of vinyl acetate becomes easy to perform. Therefore, by gradually decreasing the polymerization peak temperature from the upstream to the downstream of the tubular reactor, the polymerization of ethylene is preferentially performed on the upstream side, and the polymerization of vinyl acetate is preferentially performed on the downstream side where the molecular weight becomes high.

[0052] In addition, as one of the means for achieving the above-mentioned temperature condition, the reactor adopts a double-pipe structure, and the temperature of ethylene, vinyl acetate, and ethylene-vinyl acetate copolymer or the like flowing in the inner pipe can be adjusted using steam flowing in the outer pipe.

[0053] In addition, as another method for adjusting the slope P to the above-mentioned range, there is no particular limitation, and for example, the following can be listed: reducing the temperature difference due to the addition of raw materials or the like from the front and middle stages of the reactor; and / or making the temperature difference on the rear stage larger than that on the middle stage. Specifically, it is preferable to add raw materials such as ethylene and vinyl acetate from the front and middle stages of the reactor. In addition, preheating of ethylene and vinyl acetate added from the front and middle stages of the reactor can be listed. The temperature temporarily decreases due to the addition of raw materials such as ethylene and vinyl acetate from the middle of the tubular reactor, and the temperature rises due to the heat of polymerization. The temperature in the reactor changes depending on the raw material addition site like this, but in the present embodiment, in order to reduce the temperature difference on the front and middle stages of the reactor, by preheating and then adding ethylene and vinyl acetate, it is possible to maintain the state in which the polymerization of ethylene is preferentially performed on the front and middle stages. In addition, it is preferable to make the temperature difference on the rear stage larger than that on the middle stage.

[0054] In the GPC-FTIR, the absorbance I (-CH2-) attributed to the methylene group was measured based on the absorption at 2928 cm -1 -1. The absorbance I (-C＝O) attributed to the carbonyl group was measured based on the absorption at 1741 cm -1 -1. The specific measurement using the GPC-FTIR can be performed by the method described in the examples.

[0055] (mean value Q)

[0056] Figure 2 A schematic diagram for explaining the mean value Q measured using the GPC-FTIR is shown in FIG. 1. In FIG. 1, the left vertical axis indicates the detection intensity of the copolymer in the GPC, and the right vertical axis indicates the absorbance ratio (I i(-CH3) / I i(-CH2-) ) in the FTIR. Moreover, the horizontal axis indicates the molecular weight of the copolymer in logarithmic scale.

[0057] The mean value Q is defined as the average of the absorbance ratio (I i / I i(-CH3) / I i(-CH2-) ) of each molecular weight M i(-CH3) in the half peak width region of the molecular weight distribution. The absorbance ratio (I i(-CH2-) / I i(-CH3) ) is the ratio of the absorbance I i(-CH2-) attributed to the methyl group to the absorbance I i(-CH3) attributed to the methylene group, and indicates the content ratio of the methyl group at each molecular weight of the ethylene-vinyl acetate copolymer. Since the proportion of the end of the ethylene-vinyl acetate copolymer terminated with the methyl group is high, a higher content ratio of the methyl group means a larger number of branches. Therefore, a higher average of the absorbance ratio (I i(-CH2-) / I i(-CH3) ) means a larger number of branches of the copolymer of the present embodiment.

[0058] Note that the absorbance ratio (I i(-CH2-) / I (-CH2-) ) calculated in the above-described manner indicates the amount of carbon atoms in the "-CH3" relative to 1000 carbon atoms in the "-CH2-". In addition, the mean value Q refers to the average of the carbon atoms in the "-CH3" relative to 1000 carbon atoms in the "-CH2-" in the half peak width region of the molecular weight distribution.

[0059] In this embodiment, the average value Q is 23.0 ≤ Q ≤ 30.0, preferably 23.5 ≤ Q ≤ 28.0, and more preferably 24.0 ≤ Q ≤ 26.0. When the average value Q is 23.0 or greater, entanglement of molecular chains in the ethylene-vinyl acetate copolymer increases, thereby reducing crystallinity and improving transparency. Furthermore, when the average value Q is 30.0 or less, mold releasability is further improved.

[0060] The method for adjusting the average Q value to fall within the above range is not particularly limited and can be controlled by adjusting the amounts of the chain transfer agent, vinyl acetate, and initiator, etc. For example, a method in which the amount of propylene used as a chain transfer agent is set to 0.30 mol% or less, preferably 0.28 mol% or less, and more preferably 0.25 mol% or less can be mentioned.

[0061] When more than 0.3 mol % of propylene is added, dehydrogenation in the molecular chain of the ethylene-vinyl acetate resin increases, generating free radicals. The free radicals then combine with each other to cause a termination reaction, which tends to reduce the number of branches.

[0062] Furthermore, raw materials such as ethylene and vinyl acetate are preferably added to the reactor from the front and middle sections. By adding raw materials such as ethylene and vinyl acetate from the reactor inlet and carrying out polymerization, a polymer layer and a gas layer coexist within the reactor. By adding new raw materials such as ethylene and vinyl acetate to the reactor, the polymer layer and the gas layer are stirred, accelerating polymerization and thereby appropriately adjusting the number of branches.

[0063] It should be noted that when raw materials such as ethylene and vinyl acetate are added only from the reactor inlet, the amount of polymer obtained is small, which is not preferable from the viewpoint of productivity.

[0064] In GPC-FTIR, the absorbance attributed to the methylene group is (-CH2-) Press 2928cm -1 The absorbance of the methyl group was measured. (-CH3) Press 2960cm -1 The specific measurement by GPC-FTIR can be performed by the method described in the examples.

[0065] (Methyl branched chain)

[0066] Depend on 13The methyl branch of the ethylene-vinyl acetate copolymer of the present embodiment is preferably 0.00 / 100C or more and less than 0.16 / 100C, more preferably 0.00 / 100C or more and 0.13 / 100C or less, further preferably 0.00 / 100C or more and 0.10 / 100C or less, as determined by C-NMR. By having a methyl branch of less than 0.16 / 100C, the resulting molded body and the like have a tendency to further improve in the balance of the dart impact strength, the environmental stress cracking resistance, the mold releasability, and the transparency.

[0067] The methyl branch can be adjusted by the kind and amount of chain transfer agent. In addition, the method for measuring the methyl branch can be in accordance with the method described in the examples.

[0068] (Melting heat)

[0069] The melting heat (ΔH) of the ethylene-vinyl acetate copolymer of the present embodiment, as determined by differential scanning calorimetry, is preferably 43 J / g or more and 90 J / g or less, more preferably 50 J / g or more and 88 J / g or less, further preferably 61 J / g or more and 83 J / g or less. By having a melting heat within the above range, the resulting molded body and the like have an excellent balance of the dart impact strength, the environmental stress cracking resistance, the mold releasability, and the transparency.

[0070] The melting heat can be adjusted by the vinyl acetate concentration, the molecular weight distribution, and the like. In addition, the method for measuring the melting heat can be in accordance with the method described in the examples.

[0071] (Melt flow rate)

[0072] The melt flow rate of the ethylene-vinyl acetate copolymer of the present embodiment is preferably 0.1 g / 10 minutes or more and less than 30 g / 10 minutes, more preferably 0.6 g / 10 minutes or more and 10 g / 10 minutes or less, further preferably 0.8 g / 10 minutes or more and 4.0 g / 10 minutes or less. By having a melt flow rate within the above range, the resulting molded body and the like have a tendency to further improve in the dart impact strength and the environmental stress cracking resistance.

[0073] As the method for adjusting the melt flow rate of the ethylene-vinyl acetate copolymer, there is no particular limitation, and for example, a method of adjusting the reaction temperature and / or the reaction pressure at the time of polymerization to obtain the ethylene-vinyl acetate copolymer can be cited. More specifically, at the time of polymerization to obtain the ethylene-vinyl acetate copolymer, when the reaction temperature is increased, there is a tendency for the melt flow rate of the ethylene-vinyl acetate copolymer to increase, and when the reaction pressure is increased, there is a tendency for the melt flow rate of the ethylene-vinyl acetate copolymer to decrease.

[0074] The melt flow rate can be measured according to JIS K7210:1999, No. D (temperature = 190°C, load = 2.16 kg).

[0075] (vinyl acetate unit)

[0076] The content of the vinyl acetate unit is preferably 11% by mass or more and 25% by mass or less, more preferably 12% by mass or more and 23% by mass or less, and even more preferably 13% by mass or more and 20% by mass or less, relative to the total amount of the ethylene-vinyl acetate copolymer. By having the content of the vinyl acetate unit within the above range, the balance of the falling weight impact strength, the environmental stress cracking resistance, the mold releasability, and the transparency of the obtained molded body and the like is excellent.

[0077] As a method of adjusting the content of the vinyl acetate unit, there is no particular limitation, and for example, the following can be cited: appropriately adjusting the amount of addition of the vinyl acetate monomer, the polymerization temperature, the polymerization pressure, and the like in the process of polymerizing to obtain the ethylene-vinyl acetate copolymer.

[0078] Note that the content of the vinyl acetate unit can be measured by, according to JIS K7192:1999, as a reference test method, preparing a calibration curve by saponification and potentiometric titration, and as a comparison test method, converting to vinyl acetate by infrared spectroscopy. Specifically, it can be measured by the method described in the Examples described later.

[0079] (ethylene unit)

[0080] The content of the ethylene unit is preferably 75% by mass or more and 89% by mass or less, more preferably 77% by mass or more and 88% by mass or less, and even more preferably 80% by mass or more and 87% by mass or less, relative to the total amount of the ethylene-vinyl acetate copolymer. By having the content of the ethylene unit within the above range, the balance of the falling weight impact strength, the environmental stress cracking resistance, the mold releasability, and the transparency of the obtained molded body and the like is excellent.

[0081] The ethylene-vinyl acetate copolymer of the present embodiment can contain a monomer unit other than the ethylene unit and the vinyl acetate unit. As the other monomer unit, there is no particular limitation, and for example, a unit derived from propylene or the like can be cited. From the viewpoint of the falling weight impact strength, the environmental stress cracking resistance, and the transparency, the monomer unit other than the ethylene unit and the vinyl acetate unit is preferably 0.3% by mole or less, relative to the ethylene unit.

[0082] The ethylene-vinyl acetate copolymer of the present embodiment can also use a substance obtained by dry blending or melt blending two or more kinds of ethylene-vinyl acetate copolymers in an arbitrary ratio. In the case of using two or more kinds of ethylene-vinyl acetate copolymers, the content of the vinyl acetate unit in the entire of these resins is preferably within the above range.

[0083] [Method for producing ethylene-vinyl acetate copolymer]

[0084] The ethylene-vinyl acetate copolymer of the present embodiment can be obtained, for example, by polymerizing ethylene and vinyl acetate in the presence of a polymerization initiator under pressurized heating, but is not particularly limited. A chain transfer agent can be added as necessary in the polymerization system.

[0085] The polymerization method of the ethylene-vinyl acetate copolymer is not particularly limited, and for example, autoclave method, pipe method can be exemplified. Among them, it is preferable to use a pipe reactor having a long ring structure. By using a pipe reactor, the polymerization temperature and the polymerization pressure can be appropriately adjusted in each region from the upstream to the downstream.

[0086] The average polymerization temperature is preferably 150°C or higher and 280°C or lower, more preferably 180°C or higher and 240°C or lower. In addition, the average polymerization pressure is preferably 100 MPa or higher and 275 MPa or lower, more preferably 120 MPa or higher and 270 MPa or lower, further preferably 180 MPa or higher and 265 MPa or lower.

[0087] Note that the reactor can have a plurality of sites for supplying ethylene, vinyl acetate, and a polymerization initiator. Near each feeding portion, the temperature temporarily decreases due to the addition of raw materials and the like, but then the temperature in the reactor rises again due to the heat of polymerization. In the present embodiment, since the raw materials supplied from the front section and the middle section are added to the pipe reactor after being pressurized, although the temperature is somewhat increased by pressurization, it is preferable to preheat the supplied raw materials. Thereby, the temperature decrease in the upstream can be suppressed by supplying raw materials having a higher temperature. Therefore, from the viewpoint of controlling the slope P, the polymerization temperature can be gradually decreased from the upstream to the downstream of the polymerization.

[0088] Note that in the present embodiment, the front section of the reactor refers to a position (an inlet) of 0% to 10% of the entire length of the reactor, the middle section of the reactor refers to a position of 10% to 40% of the entire length of the reactor from the inlet, and the rear section of the reactor refers to a position of 40% to 70% of the entire length of the reactor from the inlet.

[0089] The ethylene and vinyl acetate supplied to the reactor can be in a gaseous state or a liquid state, and is preferably in a gaseous state (gas).

[0090] As the polymerization initiator, there is no particular limitation, and for example, a radical generator such as a peroxide can be exemplified. As the radical generator such as a peroxide, there is no particular limitation, and for example, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyacetate, t-butyl peroxyneopentanoate, di-t-butyl peroxide, and the like can be exemplified.

[0091] As the chain transfer agent, there is no particular limitation, and for example, alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and the like; alkanes or alkenes such as ethane, propane, propylene, butane, 1-butene, 2-butene, and the like; ketones or aldehydes such as acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methyl isopropyl ketone, formaldehyde, acetaldehyde, n-butyraldehyde, isobutyraldehyde, n-pentanal, iso-pentanal, and the like can be exemplified.

[0092] The ethylene-vinyl acetate copolymer obtained by polymerization in the above-described manner is preferably separated from the raw material and pelletized into a granular shape using an extruder. For example, in the case of using a tubular system, the raw material and the like and the ethylene-vinyl acetate copolymer are preferably separated while reducing the pressure using a high-pressure separator and a low-pressure separator, and the ethylene-vinyl acetate copolymer in a molten state is pelletized into a granular shape using an extruder.

[0093] In the high-pressure separator and the low-pressure separator, the ethylene-vinyl acetate copolymer in a molten state and unreacted gases such as ethylene gas and vinyl acetate gas as the raw material exist in the form of a gas-liquid mixed fluid. The unreacted gases can be recovered from the upper portion of the vessel of each separator and reused in polymerization.

[0094] After the ethylene-vinyl acetate copolymer is pelletized using an extruder, it is preferable to be dried in a silo in which the pellets are stored.

[0095] The ethylene-vinyl acetate copolymer of the present embodiment can contain, as necessary, known additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, an antifog agent, a coloring pigment, and the like.

[0096] As the antioxidant, there is no particular limitation, and for example, phenolic antioxidants such as 2,6-di-t-butyl-4-methylphenol, pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate octadecyl, and the like; phosphorus-containing antioxidants such as tris(2,4-di-t-butylphenyl) phosphite, 4,4-biphenylene diphosphite tetrakis(2,4-di-t-butylphenyl) ester, and the like; phosphorus / phenolic antioxidants such as 6-t-butyl-4-[3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yloxy)propyl]-o-cresol, and the like; sulfur-containing antioxidants such as dilauryl thiodipropionate, and the like can be exemplified.

[0097] [Shaped body]

[0098] The shaped body of the present embodiment contains the ethylene-vinyl acetate copolymer described above. The shaped body of the present embodiment is not particularly limited, and can be obtained by, for example, injection molding, extrusion molding, or stretch molding, and can be suitably used for various applications. Specifically, the shaped body is not particularly limited, and can be exemplified by, for example, artificial turf mats, mudguards for automobiles, mudguard covers, drain hoses, and the like. In addition, the shaped body can also be used as a fiber or the like.

[0099] [Sheet]

[0100] The sheet of the present embodiment contains the ethylene-vinyl acetate copolymer described above. As a method for manufacturing the sheet, for example, T-die molding, inflation molding, calender molding, chip molding, or the like can be exemplified. T-die molding or inflation molding is particularly preferred.

[0101] The sheet of the present embodiment can be suitably used for mudguards for automobiles, mudguard covers. Note that the "sheet" refers to a sheet-shaped plastic sheet having a thickness of 250 μm or more. The thickness of the sheet of the present embodiment is preferably 250 μm or more, more preferably 300 μm to 10 mm, or 0.5 mm to 10 mm.

[0102] In addition, the sheet of the present embodiment can have a laminated structure having other layers in addition to the layer containing the ethylene-vinyl acetate copolymer described above. As a method for manufacturing such a laminated sheet, there is no particular limitation, and for example, a method manufactured by lamination by a lamination process, or a method manufactured by a laminated extrusion process can be exemplified.

[0103] [Expanded body]

[0104] The expanded body of the present embodiment contains the ethylene-vinyl acetate copolymer described above. The expanded body of the present embodiment is not particularly limited, and can be obtained by, for example, using expanded fine particles or the like, and can be suitably used for various applications such as cushion flooring materials.

[0105] [Examples]

[0106] Hereinafter, the present application will be described more specifically using examples and comparative examples. The present application is not limited by any of the following examples.

[0107] [GPC-IR measurement (slope P of carbonyl group)]

[0108] The GPC-IR measurement (slope P of carbonyl group) was performed under the following conditions. As pretreatment of the sample, the sample was weighed, solvent (TCE to which 0.05% BHT was added) was added, and it was dissolved by shaking at 110°C for 1 hour. For calibration of the molecular weight, a cubic approximation curve using a standard polystyrene manufactured by Tosoh Corporation was used. Note that the molecular weight was converted to polyethylene molecular weight using a factor.

[0109] The average molecular weight was calculated from the elution curve using SEC-FTIR software (manufactured by Thermo Nicolet) based on the peak area of the absorbance at 2850 cm -1 ~ 2940 cm -1 -1. Note that the average molecular weight was calculated from the elution curve using SEC-FTIR software (manufactured by Thermo Nicolet) based on the peak area of the absorbance at 2850 cm -1 -1. Note that the average molecular weight was calculated from the elution curve using SEC-FTIR software (manufactured by Thermo Nicolet) based on the peak area of the absorbance at 2850 cm -1 -1. Note that the average molecular weight was calculated from the elution curve using SEC-FTIR software (manufactured by Thermo Nicolet) based on the peak area of the absorbance at 2850 cm

[0110] Regarding the slope P of the carbonyl group, GPC (device: HLC-8121 GPC / HT manufactured by Tosoh Corporation) was used to measure, and the graph of the vinyl acetate ratio (VAc ratio) in each molecular weight region was calculated using an Avatar 370 manufactured by Thermo Nicolet as a detector, and a quadratic approximation line. Note that regarding the elution curve of GPC-IR, the value of the component amount (d(W) / d(logM)) at 1 / 2 of the value of the component amount (d(W) / d(logM)) at the peak top of the GPC measurement was calculated and used as 1 / 2A, and the VAc ratio in the molecular weight range of 1 / 2A was obtained.

[0111] (Measurement conditions)

[0112] GPC device: HLC-8121 GPC / HT (manufactured by Tosoh)

[0113] FT-IR device: Avatar 370 (manufactured by Thermo Nicolet)

[0114] Column: TSKgel GMH HR - H (20) HT (inner diameter 7.8 mm x 30 cm) x 2 (manufactured by Tosoh)

[0115] Eluent: Tetrachloroethylene (manufactured by Fuji Photo Film and Otsuka Pharmaceutical, special grade)

[0116] Flow rate: 0.7 mL / minute

[0117] Sample concentration: 2.0 mg / mL

[0118] Injection amount: 0.3 mL

[0119] Column temperature: 110°C

[0120] Detector temperature: 110°C

[0121] Measurement wave number: 4000cm -1 ~650cm -1

[0122] Resolution: 4cm -1

[0123] Scan times: 8 times / 1 point

[0124] Based on the obtained IR data, the absorbance ratio (I i(-C＝O) / I i(-CH2-) ), in the half-peak width region, the molecular weight M is expressed by the approximate linear relationship obtained by the least squares method. i Logarithm of log(M i ) and absorbance ratio (I i(-C＝O) / I i(-CH2-) ) relationship (refer to Figure 1 ). The slope P is obtained based on the approximate linear relationship obtained in this way.

[0125] It should be noted that the absorbance I attributed to the methylene group (-CH2-) Press 2928cm -1 The absorbance of the carbonyl group was measured. (-C＝O) Press 1741cm -1 The absorption was measured.

[0126] [GPC-IR measurement (average value Q of terminal methyl groups)]

[0127] GPC-IR measurement (average value Q of terminal methyl groups) was performed under the following conditions. As a sample pretreatment, the sample was weighed, and a solvent, o-dichlorobenzene, was added and dissolved by shaking at 140°C for 90 minutes. Molecular weight calibration was performed using 12 points of the MW (molecular weight) of standard polystyrene manufactured by Tosoh Corporation in the range of 1050 to 20600000. The MW of each standard polystyrene was multiplied by a coefficient of 0.43 to obtain the molecular weight converted to polyethylene. The elution time and the molecular weight converted to polyethylene were plotted and a primary calibration curve was prepared to determine the weight average molecular weight (Mw) and number average molecular weight (Mn).

[0128] The amount of terminal methyl group was measured using six points in the range of 2.6 to 45.9 of CH3 / 1000C with a Composition Calibration Kit (Octene) manufactured by Polymer Char Co., Ltd., and a calibration curve was prepared, and the measurement was performed using GPC (device: GPC-IR manufactured by Polymer Char Co., Ltd.). FT-IR (IR5 manufactured by Polymer Char Co., Ltd.) was used as a detector.

[0129] Note that, regarding the amount of terminal methyl group, the value of the component amount (d(W) / d(logM)) at 1 / 2 of the peak top value of the component amount (d(W) / d(logM)) measured by GPC was found and was taken as 1 / 2A, and for the range of the molecular weight of 1 / 2A, the average value Q of the amount of CH3 per 1000C was calculated.

[0130] (Measurement conditions)

[0131] Device: GPC-IR manufactured by Polymer Char Co., Ltd.

[0132] Detector: IR5 manufactured by Polymer Char Co., Ltd.

[0133] Column: UT-807 manufactured by Showa Denko K.K. (1) and GMHHR-H(S)HT manufactured by Tosoh Corp. (2) were connected in series and used

[0134] Mobile phase: o-dichlorobenzene

[0135] Column temperature: 140°C

[0136] Flow rate: 1.0 ml / min

[0137] Sample concentration: 16 mg / 8 mL

[0138] From the obtained IR data, the absorbance ratio (I i(-CH3) / I i(-CH2-) ) at each molecular weight was calculated, and in the half peak width region, the average value of the absorbance ratio (I i(-CH3) / I i(-CH2-) ) was calculated, and thus the average value Q was obtained.

[0139] Note that the absorbance I (-CH2-) was measured at 2928 cm -1 , and the absorbance I (-CH3) was measured at 2960 cm -1 .

[0140] [Content determination of vinyl acetate unit]

[0141] According to JIS K7192:1999, as a reference test method, a standard curve was prepared by saponification and potentiometric titration using a VAc standard sample of ethylene-vinyl acetate copolymer whose content of vinyl acetate unit was known, and as a control test method, the content of vinyl acetate unit (VA content) in the ethylene-vinyl acetate copolymer resins obtained in the examples and comparative examples was determined by infrared spectroscopy.

[0142] [Measurement of Melt Flow Rate (MFR)]

[0143] The melt flow rate of the ethylene-vinyl acetate copolymers obtained in the examples and comparative examples was measured according to JIS K7210:1999 No. D (temperature = 190°C, load = 2.16 kg).

[0144] [ 13 C-NMR Measurement (Methyl Branch)

[0145] 13 C-NMR Measurement (Methyl Branch) was performed under the following conditions. As a sample pretreatment, a sample was weighed, solvent o-dichlorobenzene was added, and it was dissolved by shaking at 140°C for 180 minutes. The measurement of the methyl branch used an AVANCE 500 HD nuclear magnetic resonance device of Bruker, and was performed with the signal of the methylene carbon at 29.9 ppm as a reference.

[0146] The ratio of the methyl branch was calculated from the ratio of the area intensities of the signal of the methylene carbon (29.9 ppm) and the methyl branch (20.07 ppm) observed in the above measurement. 13 The ratio of the methyl branch was calculated from the ratio of the area intensities of the signal of the methylene carbon (29.9 ppm) and the methyl branch (20.07 ppm) observed in the above measurement. 13 The ratio of the signal around 20.07 ppm in the C-NMR spectrum (Assignment of Branching Species of Low Density Polyethylene Based on C-13 NMR, Takao Nishida et al., P774 (29) 980) was calculated.

[0147] (Measurement Conditions)

[0148] Measurement device: AVANCE-500HD manufactured by Bruker

[0149] Observed nucleus: 13 C

[0150] Observed frequency: 125.77 MHz

[0151] Pulse width: 5.0 microseconds

[0152] PD: 5 seconds

[0153] Measurement temperature: 120°C

[0154] Cumulative number: 8000 times

[0155] Reference: PE (-eee-) signal, 29.9 ppm

[0156] Solvent: o-dichlorobenzene-d4

[0157] Sample concentration: 5% by weight / volume

[0158] Dissolution temperature: 140°C

[0159] [Difference Scanning Calorimetry (Heat of Fusion)]

[0160] The measurement of the heat of fusion ΔH was performed using a DSC (manufactured by PerkinElmer, trade name: DSC8000). Specifically, 8 mg of the ethylene-vinyl acetate copolymer obtained in the examples and comparative examples was weighed and placed in an aluminum sample pan as a sample. An aluminum lid was installed on the aluminum sample pan, and set in a differential scanning calorimeter. While purging nitrogen at a flow rate of 20 mL / minute, the sample for measurement and a reference sample were held at 0°C for 1 minute, then temperature- increased to 150°C at a rate of 200°C / minute, held at 150°C for 5 minutes, temperature-decreased at a rate of 10°C / minute, held at 0°C for 5 minutes, and then the total heat calculated from the melting peak area from 0°C to 150°C was divided by the mass of the sample, whereby the heat of fusion (ΔH) was obtained.

[0161] [Drop Weight Impact Strength]

[0162] Using the ethylene-vinyl acetate copolymer obtained in the examples and comparative examples, a flat test piece of 100 mm x 100 mm x 2.0 mm was produced using a Sumitomo full-electric injection molding machine SE130DUZ-C360 (setting the cylinder temperature to 200°C, and setting the mold temperature to 40°C) under conditions of an injection time of 20 seconds, and a cooling time of 30 seconds. The flat test piece obtained was subjected to a drop weight impact test using a graphic impact tester (manufactured by Toyo Seiki Co., Ltd.) under the following conditions, and the total absorbed energy was measured.

[0163] (Conditions)

[0164] Holder diameter: 76 mm

[0165] Firing pin diameter: 12.7 mm

[0166] Firing pin weight: 6.5 kg

[0167] Height: 100 cm

[0168] Temperature: 23°C

[0169] [Environmental stress cracking resistance (ESCR)]

[0170] As an evaluation of environmental stress cracking resistance, the determination of b-ESCR (constant strain environmental stress cracking test) of the ethylene-vinyl acetate copolymers obtained in the examples and comparative examples was performed according to ASTM D 1693. Using a 10 mass% aqueous solution of IGEPAL (registered trademark) CO-630 manufactured by Rhodia Japan (K.K.) as a test solution, the time when the probability of cracking due to environmental stress was 50% (hereinafter referred to as F50 value) was determined, which was taken as the value of the environmental stress cracking resistance (ESCR) of the ethylene-vinyl acetate copolymer. The unit was h (hour). The larger the value, the more excellent the environmental stress cracking resistance.

[0171] [Measurement of transparency (haze)]

[0172] On a smooth iron plate having a thickness of 5 mm, an aluminum plate having a thickness of 0.1 mm was placed, and further on the aluminum plate, a polyethylene terephthalate film (Lumirror manufactured by Toray Industries, Inc.) having a thickness of 50 μm was placed. A mold having a length of 200 mm in the longitudinal direction, a width of 200 mm in the lateral direction, and a thickness of 3.1 mm was placed thereon, and 130 g of the ethylene-vinyl acetate copolymer obtained in the examples and comparative examples was added to the mold. Then, the same polyethylene terephthalate film as described above, the same aluminum plate as described above, and the same iron plate as described above were further placed thereon.

[0173] This was placed in a compression molding machine (SFA-37 manufactured by Kanno Metal Industry Co., Ltd.) whose temperature was adjusted to 180°C, and preheating was performed at 180°C, 0.1 MPa for 180 seconds, and then degassing (10 MPa) was performed for 5 seconds, and pressurization was performed at 180°C, 15 MPa for 120 seconds.

[0174] After the pressurization was completed, the sample was taken out, and after 5 seconds, it was placed in a compression molding machine (SFA-37 manufactured by Kanno Metal Industry Co., Ltd.) whose temperature was adjusted to 25°C, and pressurization was performed at 25°C, 10 MPa for 300 seconds while cooling was performed, whereby a press sheet was produced. After the cooling, the press sheet taken out from the mold was left to stand in an environment having a temperature of 23°C and a humidity of 50% for 24 hours or more.

[0175] The thickness of the press-molded sheet obtained in the above manner was measured using a constant pressure thickness gauge (manufactured by TECLOCK Corporation, Model PG-02, minimum display 0.001 mm), and a portion having a thickness of 3.1 mm in the press-molded sheet was selected. Then, haze value was measured according to ASTM D1003 using a HAZE METER HM-150 manufactured by MURAKAMI COLOR TECHNOLOGY RESEARCH LABORATORY CO., LTD. at the portion having a thickness of 3.1 mm. The smaller the haze value, the more excellent the transparency.

[0176] [Release property]

[0177] Using the ethylene-vinyl acetate copolymers obtained in the examples and comparative examples, a needle gate flat plate test piece of 200 mm x 200 mm x 4.0 mm was produced using a Sumitomo all-electric injection molding machine SE130DUZ-C360 (setting the cylinder temperature to 200°C and the mold temperature to 40°C) under conditions of an injection time of 20 seconds and a cooling time of 30 seconds, and the release property from the mold in the case where the ejection from the mold was performed once under the following standards was evaluated: 4 points (electric type), ejection protrusion force: 10 kN, ejection speed: 10 mm / s, and ejection number: 1.

[0178] O: The number of flat plates that did not release from the mold after molding 10 pieces was 0

[0179] Δ: The number of flat plates that did not release from the mold after molding 10 pieces was 1 or more but less than 5

[0180] X: The number of flat plates that did not release from the mold after molding 10 pieces was 5 or more

[0181] O and Δ were determined to be acceptable.

[0182] [Example 1]

[0183] Polymerization was performed using a tubular reactor having a plurality of feed ports. Specifically, ethylene and vinyl acetate preheated to 160°C were introduced into the reactor from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Then, ethylene and vinyl acetate preheated to 160°C were additionally introduced from the feed port on the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator was introduced from the middle stage side and the rear stage side. Note that the amount of vinyl acetate was 7 mol% relative to ethylene as a whole.

[0184] The average polymerization temperature of the tubular reactor was set to 221°C, and the polymerization pressure was set to 236 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak top temperature at the initial stage was 250°C, the peak top temperature at the middle stage was 246°C, the peak top temperature at the rear stage was 230°C, and the temperature at the reactor outlet was 171°C. In addition, the difference between the valley bottom temperature before and after the introduction of ethylene, vinyl acetate, and the polymerization initiator at the feed port on the middle stage side was 10°C, and the difference between the valley bottom temperature before and after the introduction of the polymerization initiator at the feed port on the rear stage side was 66°C.

[0185] The ethylene-vinyl acetate copolymer discharged from the tubular reactor was introduced into a high-pressure separator, and unreacted gas and the like were separated. Subsequently, the ethylene-vinyl acetate copolymer discharged from the high-pressure separator was introduced into a low-pressure separator, and residual unreacted gas and the like were separated, whereby an ethylene-vinyl acetate copolymer in a molten state was obtained.

[0186] The obtained ethylene-vinyl acetate copolymer in a molten state was sent to an extruder, and pelletized, whereby an ethylene-vinyl acetate copolymer pellet was obtained. The physical properties and characteristics of the obtained ethylene-vinyl acetate copolymer were measured by the above-described methods. The measurement results are shown in Table 1.

[0187] [Example 2]

[0188] Ethylene, vinyl acetate, and propylene were preheated to 160°C, and introduced into the reactor from the feed ports on the front stage side and the middle stage side of the tubular reactor, and the amount of propylene was 0.11 mol% relative to ethylene in total, and an ethylene-vinyl acetate copolymer of Example 2 was obtained in the same manner as in Example 1, except for this.

[0189] [Example 3]

[0190] Ethylene, vinyl acetate, and propylene were preheated to 160°C, and introduced into the reactor from the feed ports on the front stage side and the middle stage side of the tubular reactor, and the amount of propylene was 0.17 mol% relative to ethylene in total, and an ethylene-vinyl acetate copolymer of Example 3 was obtained in the same manner as in Example 1, except for this.

[0191] [Example 4]

[0192] Ethylene and vinyl acetate preheated to 160°C were introduced into the reactor from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Subsequently, ethylene and vinyl acetate preheated to 160°C were additionally introduced from the feed port on the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced from the middle stage side and the rear stage side. Note that the amount of vinyl acetate was 7 mol% relative to ethylene as a whole.

[0193] The average polymerization temperature of the tubular reactor was set to 222°C, and the polymerization pressure was set to 264 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak top temperature of the initial stage was 255°C, the peak top temperature of the middle stage was 237°C, the peak top temperature of the rear stage was 230°C, and the temperature of the reactor outlet was 175°C. In addition, the difference between the valley bottom temperature before and after the introduction of ethylene, vinyl acetate, and a polymerization initiator at the feed port on the middle stage side was 20°C, and the difference between the valley bottom temperature before and after the introduction of a polymerization initiator at the feed port on the rear stage side was 69°C, and otherwise, the ethylene-vinyl acetate copolymer of Example 4 was obtained in the same manner as in Example 1.

[0194] [Example 5]

[0195] Ethylene and vinyl acetate preheated to 160°C were introduced into the reactor from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Subsequently, ethylene and vinyl acetate preheated to 160°C were additionally introduced from the feed port on the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced from the middle stage side and the rear stage side. Note that the amount of vinyl acetate was 7 mol% relative to ethylene as a whole.

[0196] The average polymerization temperature of the tubular reactor was set to 240°C, and the polymerization pressure was set to 264 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak top temperature of the initial stage was 275°C, the peak top temperature of the middle stage was 268°C, the peak top temperature of the rear stage was 255°C, and the temperature of the reactor outlet was 189°C. In addition, the difference between the valley bottom temperature before and after the introduction of ethylene, vinyl acetate, and a polymerization initiator at the feed port on the middle stage side was 27°C, and the difference between the valley bottom temperature before and after the introduction of a polymerization initiator at the feed port on the rear stage side was 64°C, and otherwise, the ethylene-vinyl acetate copolymer of Example 5 was obtained in the same manner as in Example 1.

[0197] [Example 6]

[0198] Ethylene and vinyl acetate preheated to 160°C were introduced into the reactor from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Subsequently, ethylene and vinyl acetate preheated to 160°C were additionally introduced from the feed port on the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced from the middle stage side. Note that the amount of vinyl acetate was 8.1 mol% relative to ethylene as a whole.

[0199] The average polymerization temperature of the tubular reactor was set to 195°C, and the polymerization pressure was set to 264 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak temperature on the front stage was 238°C, the peak temperature on the middle stage was 220°C, and the temperature at the outlet of the reactor was 150°C. In addition, the difference between the valley temperature and the peak temperature before and after the introduction of ethylene, vinyl acetate, and a polymerization initiator at the feed port on the middle stage side was 7°C, and otherwise, the ethylene-vinyl acetate copolymer of Example 6 was obtained in the same manner as in Example 1.

[0200] [Example 7]

[0201] Ethylene and vinyl acetate preheated to 160°C were introduced into the reactor from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Subsequently, ethylene and vinyl acetate preheated to 160°C were additionally introduced from the feed port on the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced from the middle stage side. Note that the amount of vinyl acetate was 8.1 mol% relative to ethylene as a whole.

[0202] The average polymerization temperature of the tubular reactor was set to 196°C, and the polymerization pressure was set to 264 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak temperature on the front stage was 238°C, the peak temperature on the middle stage was 220°C, and the temperature at the outlet of the reactor was 155°C. In addition, the difference between the valley temperature and the peak temperature before and after the introduction of ethylene, vinyl acetate, and a polymerization initiator at the feed port on the middle stage side was 7°C, and otherwise, the ethylene-vinyl acetate copolymer of Example 7 was obtained in the same manner as in Example 1.

[0203] [Example 8]

[0204] Ethylene and vinyl acetate preheated to 160°C were introduced into the reactor from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Subsequently, ethylene and vinyl acetate preheated to 160°C were additionally introduced from the feed port on the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced from the middle stage side and the rear stage side. Note that the amount of vinyl acetate was 5.8 mol% relative to ethylene in total.

[0205] The average polymerization temperature of the tubular reactor was set to 212°C, and the polymerization pressure was set to 236 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak top temperature of the initial stage was 245°C, the peak top temperature of the middle stage was 227°C, the peak top temperature of the rear stage was 218°C, and the temperature of the reactor outlet was 155°C. In addition, the difference between the valley bottom temperature before and after the introduction of ethylene, vinyl acetate, and a polymerization initiator at the feed port on the middle stage side was 19°C, and the difference between the valley bottom temperature before and after the introduction of a polymerization initiator at the feed port on the rear stage side was 50°C, and otherwise, the ethylene-vinyl acetate copolymer of Example 8 was obtained in the same manner as in Example 1.

[0206] [Example 9]

[0207] Ethylene, vinyl acetate, and propylene preheated to 160°C were introduced into the reactor from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Subsequently, ethylene and vinyl acetate preheated to 160°C were additionally introduced from the feed port on the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced from the middle stage side and the rear stage side. Note that the amount of vinyl acetate was 7 mol% relative to ethylene in total, and the amount of propylene was 0.27 mol% relative to ethylene.

[0208] The average polymerization temperature of the tubular reactor was set to 221°C, and the polymerization pressure was set to 236 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak top temperature of the initial stage was 252°C, the peak top temperature of the middle stage was 247°C, the peak top temperature of the rear stage was 229°C, and the temperature of the reactor outlet was 170°C. In addition, the difference between the valley bottom temperature before and after the introduction of ethylene, vinyl acetate, and a polymerization initiator at the feed port on the middle stage side was 26°C, and the difference between the valley bottom temperature before and after the introduction of a polymerization initiator at the feed port on the rear stage side was 65°C, and otherwise, the ethylene-vinyl acetate copolymer of Example 9 was obtained in the same manner as in Example 1.

[0209] [Example 10]

[0210] Ethylene and vinyl acetate preheated to 160°C were introduced into the reactor from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Subsequently, ethylene and vinyl acetate preheated to 160°C were additionally introduced from the feed port on the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced from the middle stage side. Note that the amount of vinyl acetate was 7.0 mol% relative to ethylene as a whole.

[0211] The average polymerization temperature of the tubular reactor was set to 224°C, and the polymerization pressure was set to 236 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak temperature on the front stage side was 252°C, the peak temperature on the middle stage was 221°C, and the temperature at the outlet of the reactor was 173°C. In addition, the difference between the valley temperature and the peak temperature before and after the introduction of ethylene, vinyl acetate, and a polymerization initiator at the feed port on the middle stage side was 25°C, and otherwise, the ethylene-vinyl acetate copolymer of Example 10 was obtained in the same manner as in Example 1.

[0212] [Comparative Example 1]

[0213] Ethylene and vinyl acetate were introduced from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Subsequently, ethylene and vinyl acetate were additionally introduced from the feed port on the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate and di-tert-butyl peroxide as polymerization initiators were introduced from the middle stage side and the rear stage side. Note that the amount of vinyl acetate was 7 mol% relative to ethylene as a whole.

[0214] The average polymerization temperature of the tubular reactor was set to 235°C, and the polymerization pressure was set to 264 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak temperature on the front stage side was 243°C, the peak temperature on the middle stage was 255°C, the peak temperature on the rear stage was 275°C, and the temperature at the outlet of the reactor was 191°C. In addition, the difference between the valley temperature and the peak temperature before and after the introduction of ethylene, vinyl acetate, and a polymerization initiator at the feed port on the middle stage side was 64°C, and the difference between the valley temperature and the peak temperature before and after the introduction of a polymerization initiator at the feed port on the rear stage side was 44°C, and otherwise, the ethylene-vinyl acetate copolymer of Comparative Example 1 was obtained in the same manner as in Example 1.

[0215] [Comparative Example 2]

[0216] Ethylene, vinyl acetate and propylene were introduced from the feed port of the front stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Next, ethylene and vinyl acetate were additionally introduced from the feed port of the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate and di-tert-butyl peroxide as polymerization initiators were introduced from the middle stage side and the rear stage side. Note that the amount of vinyl acetate was 2 mol% relative to ethylene, and the amount of propylene was 0.5 mol% relative to ethylene in total.

[0217] [Comparative Example 3]

[0218] Ethylene, vinyl acetate and propylene were introduced from the feed port of the front stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Next, ethylene and vinyl acetate were additionally introduced from the feed port of the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate and di-tert-butyl peroxide as polymerization initiators were introduced from the middle stage side and the rear stage side. Note that the amount of vinyl acetate was 2 mol% relative to ethylene, and the amount of propylene was 0.5 mol% relative to ethylene in total.

[0219] The average polymerization temperature of the tubular reactor was set to 237°C, and the polymerization pressure was set to 264 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak top temperature of the front stage side was 260°C, the peak top temperature of the middle stage was 265°C, the peak top temperature of the rear stage was 275°C, and the temperature of the reactor outlet was 198°C. In addition, the difference between the valley bottom temperature before and after the introduction of ethylene, vinyl acetate and a polymerization initiator at the feed port of the middle stage side was 67°C, and the difference between the valley bottom temperature before and after the introduction of a polymerization initiator at the feed port of the rear stage side was 44°C, and otherwise, the ethylene-vinyl acetate copolymer of Comparative Example 3 was obtained in the same manner as in Example 1.

[0220] [Comparative Example 4]

[0221] Ethylene, vinyl acetate and propylene were introduced from the feed port of the front stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Next, ethylene and vinyl acetate were additionally introduced from the feed port of the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate and di-tert-butyl peroxide as polymerization initiators were introduced from the middle stage side and the rear stage side. Note that the amount of vinyl acetate was 2 mol% relative to ethylene, and the amount of propylene was 0.5 mol% relative to ethylene in total.

[0222] The average polymerization temperature of the tubular reactor was set to 229°C, and the polymerization pressure was set to 264 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak top temperature on the front stage side was 250°C, the peak top temperature on the middle stage was 260°C, the peak top temperature on the rear stage was 275°C, and the temperature at the reactor outlet was 197°C. In addition, the difference between the valley bottom temperature before and after the introduction of ethylene, vinyl acetate, and the polymerization initiator at the feed port on the middle stage side was 63°C, the difference between the valley bottom temperature before and after the introduction of the polymerization initiator at the feed port on the rear stage side was 40°C, and otherwise, the ethylene-vinyl acetate copolymer of Comparative Example 4 was obtained in the same manner as in Example 1.

[0223] [Comparative Example 5]

[0224] Ethylene, vinyl acetate, and propylene were introduced from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Then, ethylene and vinyl acetate were additionally introduced from the feed port on the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate and di-tert-butyl peroxide as polymerization initiators were introduced from the middle stage side and the rear stage side. Note that the amount of vinyl acetate was 4 mol% relative to ethylene, and the amount of propylene was 0.8 mol% relative to ethylene in total.

[0225] The average polymerization temperature of the tubular reactor was set to 229°C, and the polymerization pressure was set to 264 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak top temperature on the front stage side was 250°C, the peak top temperature on the middle stage was 260°C, the peak top temperature on the rear stage was 275°C, and the temperature at the reactor outlet was 205°C. In addition, the difference between the valley bottom temperature before and after the introduction of ethylene, vinyl acetate, and the polymerization initiator at the feed port on the middle stage side was 55°C, the difference between the valley bottom temperature before and after the introduction of the polymerization initiator at the feed port on the rear stage side was 49°C, and otherwise, the ethylene-vinyl acetate copolymer of Comparative Example 5 was obtained in the same manner as in Comparative Example 4.

[0226] [Comparative Example 6]

[0227] Ethylene and vinyl acetate were introduced from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Then, ethylene and vinyl acetate were additionally introduced from the feed port on the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator was introduced from the middle stage side. Note that the amount of vinyl acetate was 14 mol% relative to ethylene in total.

[0228] The average polymerization temperature of the tubular reactor was set to 200°C, and the polymerization pressure was set to 265 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak top temperature on the front stage side was 210°C, the peak top temperature on the middle stage was 223°C, and the temperature at the reactor outlet was 171°C. In addition, the difference between the valley bottom temperature and the peak top temperature before and after the introduction of ethylene, vinyl acetate, and a polymerization initiator at the feed port on the middle stage side was 48°C, and otherwise, the ethylene-vinyl acetate copolymer of Comparative Example 6 was obtained in the same manner as in Comparative Example 4.

[0229] [Comparative Example 7]

[0230] Ethylene and vinyl acetate were introduced from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Then, ethylene and vinyl acetate were additionally introduced from the feed port on the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator was introduced from the middle stage side. Note that the amount of vinyl acetate was 12.5 mol% relative to ethylene in total.

[0231] The average polymerization temperature of the tubular reactor was set to 210°C, and the polymerization pressure was set to 265 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak top temperature on the front stage side was 220°C, the peak top temperature on the middle stage was 230°C, and the temperature at the reactor outlet was 180°C. In addition, the difference between the valley bottom temperature and the peak top temperature before and after the introduction of ethylene, vinyl acetate, and a polymerization initiator at the feed port on the middle stage side was 59°C, and otherwise, the ethylene-vinyl acetate copolymer of Comparative Example 7 was obtained in the same manner as in Comparative Example 1.

[0232] [Comparative Example 8]

[0233] Ethylene and vinyl acetate were introduced from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Note that the amount of vinyl acetate was 7.0 mol% relative to ethylene in total.

[0234] The average polymerization temperature of the tubular reactor was set to 228°C, and the polymerization pressure was set to 236 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak top temperature on the front stage side was 255°C, and the temperature at the reactor outlet was 175°C, and otherwise, the ethylene-vinyl acetate copolymer of Comparative Example 8 was obtained in the same manner as in Comparative Example 1.

[0235] [Comparative Example 9]

[0236] Ethylene and vinyl acetate preheated to 160°C were introduced into the reactor from the feed port on the front stage side of the tubular reactor, and then, tert-butyl peroxy-2- ethylhexanoate as a polymerization initiator was introduced to initiate polymerization. Then, ethylene and vinyl acetate preheated to 160°C were additionally introduced from the feed port on the middle stage side of the tubular reactor, and then, tert-butyl peroxy-2-ethylhexanoate and di-tert-butyl peroxide as polymerization initiators were introduced from the middle stage side. Note that the amount of vinyl acetate was 7 mol% relative to ethylene in total.

[0237] The average polymerization temperature of the tubular reactor was set to 240°C, and the polymerization pressure was set to 276 MPa. In addition, the polymerization temperature of the tubular reactor was adjusted so that the peak temperature at the front stage was 275°C, the peak temperature at the middle stage was 268°C, the peak temperature at the rear stage was 255°C, and the temperature at the outlet of the reactor was 191°C. In addition, the difference between the valley temperature and the peak temperature before and after the introduction of ethylene, vinyl acetate, and a polymerization initiator at the feed port on the middle stage side was 28°C, and the difference between the valley temperature and the peak temperature before and after the introduction of a polymerization initiator at the feed port on the rear stage side was 64°C, and otherwise, the ethylene-vinyl acetate copolymer of Comparative Example 9 was obtained in the same manner as in Example 1.

[0238]

[0239]

[0240] Industrial applicability

[0241] The ethylene-vinyl acetate copolymer of the present application has industrial applicability as a resin raw material used in a wide range of industrial fields.

Claims

1. An ethylene-vinyl acetate copolymer, wherein, The ethylene-vinyl acetate copolymer contains 75 mass% or more and 89 mass% or less of ethylene units and 11 mass% or more and 25 mass% or less of vinyl acetate units, The ethylene-vinyl acetate copolymer does not include long chain branches per 1,000 carbon atoms of 13 The ethylene-vinyl acetate copolymer having a long chain branch content of 0.1 to 2 determined by C-NMR measurement, The ethylene-vinyl acetate copolymer has a melt flow rate of 0.1 g / 10 minutes or more and less than 30 g / 10 minutes, The ethylene-vinyl acetate copolymer has a heat of fusion (ΔH) of 43 J / g or more and 90 J / g or less, which is measured by differential scanning calorimetry, When the molecular weight distribution and the absorbance I (-CH2-) attributed to methylene groups per molecular weight are determined using GPC-FTIR (-C＝O) and the absorbance I (-CH3-) attributed to methyl groups, In the half-peak width region of the molecular weight distribution, relative to each molecular weight M i Logarithm of log(M i ) absorbance ratio (I i(-C＝O) / I i(-CH2-) ) has a slope P of the least squares approximate linear relationship of 0.00≤P≤1.40, and In the half-width region of the molecular weight distribution, each molecular weight M i The average value Q of the absorbance ratio (I i(-CH3) / I i(-CH2-) ) is 23.0 ≤ Q ≤ 30.

0.

2. The ethylene-vinyl acetate copolymer of claim 1, wherein, The slope P is 0.05 ≤ P ≤ 1.

30.

3. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein, The slope P is 0.10 ≤ P ≤ 1.

20.

4. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein The average value Q is 23.5 ≤ Q ≤ 28.

0.

5. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein, The average value Q is 24.0 ≤ Q ≤ 26.

0.

6. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein From 13 The ethylene-vinyl acetate copolymer has a methyl branch (20.07 ppm) of less than 0.16 / 100C as determined by C-NMR.

7. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein The methyl branches of the ethylene-vinyl acetate copolymer determined by 13 The methyl branches of the ethylene-vinyl acetate copolymer determined by C-NMR (20.07 ppm) were 0.00 / 100C or more and 0.13 / 100C or less.

8. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein, The ethylene-vinyl acetate copolymer of the present application has a methyl branch content of 0.00 / 100C or more and 0.10 / 100C or less, as determined by C-NMR. 13 The ethylene-vinyl acetate copolymer of the present application has a methyl branch content of 0.00 / 100C or more and 0.10 / 100C or less, as determined by C-NMR.

9. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein, The content of the vinyl acetate units is 12 mass% or more and 23 mass% or less.

10. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein, The content of the vinyl acetate units is 13 mass% or more and 20 mass% or less.

11. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein, The content of the ethylene units is 77 mass% or more and 88 mass% or less.

12. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein, The content of the ethylene units is 80 mass% or more and 87 mass% or less.

13. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein, The ethylene-vinyl acetate copolymer further contains monomer units other than the ethylene units and the vinyl acetate units.

14. The ethylene-vinyl acetate copolymer of claim 13, wherein, The monomer units other than the ethylene units and the vinyl acetate units are units derived from propylene.

15. The ethylene-vinyl acetate copolymer of claim 13, wherein, The monomer units other than the ethylene units and the vinyl acetate units are 0.3 mol% or less relative to the ethylene units.

16. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein, The ethylene-vinyl acetate copolymer has a heat of fusion (ΔH) of 50 J / g or more and 88 J / g or less, which is measured by differential scanning calorimetry.

17. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein, The ethylene-vinyl acetate copolymer has a heat of fusion (ΔH) of 61 J / g or more and 83 J / g or less, which is measured by differential scanning calorimetry.

18. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein, The ethylene-vinyl acetate copolymer has a melt flow rate of 0.6 g / 10 minutes or more and 10 g / 10 minutes or less.

19. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein, The ethylene-vinyl acetate copolymer has a melt flow rate of 0.8 g / 10 minutes or more and 4.0 g / 10 minutes or less.

20. The ethylene-vinyl acetate copolymer of claim 1 or 2, wherein, The ethylene-vinyl acetate copolymer is evaluated as 〇 or △ in the evaluation of the mold releasability, The ethylene-vinyl acetate copolymer is used to produce a needle-shaped gate flat test piece, and the mold releasability is evaluated in the case where the flat is released from the mold under the following standards: 4 points, ejector protrusion force: 10 kN, ejector speed: 10 mm / s, and number of ejections: 1 time, 〇: The number of flats that are not released from the mold after 10 pieces are molded is 0; △: The number of flats that are not released from the mold after 10 pieces are molded is 1 or more and less than 5.

21. A shaped body, wherein, The molded body contains the ethylene-vinyl acetate copolymer according to any one of claims 1 to 20.

22. A tablet, wherein, The sheet contains the ethylene-vinyl acetate copolymer according to any one of claims 1 to 20.

23. The sheet of claim 22, wherein, The thickness of the sheet is 250 μm or more.

24. The sheet of claim 22 or 23, wherein, The thickness of the sheet is 300 μm to 10 mm.

25. The sheet of claim 22 or 23, wherein, The thickness of the sheet is 0.5 mm to 10 mm.

26. A foam, wherein, The foamed body contains the ethylene-vinyl acetate copolymer according to any one of claims 1 to 20.

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