JP2010215762A - Ethylene-vinyl acetate copolymer composition and tarpaulin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EVA-resin composition having excellent flexibility, heat resistance, high-frequency welder processability or the like, and to provide a tarpaulin using the same. <P>SOLUTION: The EVA-resin composition includes a component (A) and a component (B) as EVA resins, wherein the content rate of the component (A) to the total EVA resin is 10-90 wt.% and the content rate of the component (B) to the total EVA resin is 10-90 wt.%. The tarpaulin is obtained by using the EVA-resin composition. The component (A) is an EVA resin containing vinyl acetate in a content of 25-50 wt.%. The component (B) is an EVA resin containing vinyl acetate in a content of <25 wt.%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an ethylene-vinyl acetate copolymer composition and a tarpaulin using the same, and more specifically, it has excellent flexibility, heat resistance, high-frequency welder processability, etc., and an ethylene-vinyl acetate copolymer for tarpaulin. The present invention relates to an ethylene-vinyl acetate copolymer composition suitable as a composition and a tarpaulin in which the ethylene-vinyl acetate copolymer is laminated on the surface of a base fabric.

  Conventionally, there is a flexible container as one of products using tarpaulin. The flexible container is printed on the surface located outside the tarpaulin, which is obtained by coating the both sides of the textile fabric as the base fabric with a coating technique such as calendering, as a coating material. And welded with a high frequency welder. As the fiber knitted fabric, a plain woven fabric is mainly used which is a polyester fiber and has a fiber thickness of 500 to 1000 denier and a driving number of 15 to 30 / inch, and the covering material has a vinyl acetate unit content of 15 to Using a resin composition in which 25% by weight of ethylene-vinyl acetate copolymer is mixed with a heat stabilizer, a processing aid, and a coloring pigment, the thickness is 0.5 to 1.5 mm mainly by a calendar processing method. The one formed to a thickness of is used.

  Tarpaulins are required to have flexibility, high-frequency welder processability (weldability by high-frequency welder), printability for product display, heat resistance, mechanical strength, etc. A conventional tarpaulin using a coalescence cannot satisfy all of these required characteristics, and particularly has a drawback that it is impossible to achieve both flexibility and heat resistance.

  That is, the ethylene-vinyl acetate copolymer has significantly different characteristics depending on the vinyl acetate unit content, and the one having a high vinyl acetate unit content is excellent in flexibility but inferior in heat resistance. Those having a low vinyl acetate unit content have good heat resistance, but have the disadvantage of poor flexibility.

For this reason, conventionally, an ethylene-vinyl acetate copolymer having a vinyl acetate unit content of about 20% by weight is blended with a component for improving flexibility, etc. Attempts have been made to balance the characteristics, and for example, the following proposals have been made.
(1) EPDM (ethylene / propylene / diene terpolymer) blended with ethylene-vinyl acetate copolymer at a predetermined ratio (Patent Document 1)
(2) An ethylene-α-olefin copolymer blended at a predetermined ratio with an ethylene-vinyl acetate copolymer (Patent Documents 1 and 2)
(3) A blend of ethylene-α-olefin copolymer and maleic acid-modified resin in a predetermined ratio to ethylene-vinyl acetate copolymer (Patent Document 3)
(4) What blended ethylene-α-olefin copolymer and styrene copolymer at a predetermined ratio to ethylene-vinyl acetate copolymer (Patent Document 5)

Japanese Patent Laid-Open No. 10-77066 JP 2001-80011 A JP 2002-120344 A JP 2003-176387 A JP 2008-88418 A

  However, none of the conventional tarpaulin compositions can sufficiently satisfy the required properties as a tarpaulin, and further improvement is desired.

  The present invention solves the above-mentioned conventional problems, and has an ethylene-vinyl acetate copolymer composition excellent in required properties as a tarpaulin such as flexibility, heat resistance, and high-frequency welder workability, and the ethylene-vinyl acetate copolymer. An object is to provide a tarpaulin using the composition.

  As a result of intensive studies to solve the above problems, the present inventors have compared ethylene-vinyl acetate copolymer having a relatively high vinyl acetate unit content and vinyl acetate unit content as an ethylene-vinyl acetate copolymer. It has been found that a composition having excellent properties such as flexibility and heat resistance can be obtained by using a relatively small amount of ethylene-vinyl acetate copolymer.

  The present invention has been achieved based on such findings, and the gist thereof is as follows.

[1] An ethylene-vinyl acetate copolymer composition containing two or more types of ethylene-vinyl acetate copolymers having different vinyl acetate unit contents, wherein the ethylene-vinyl acetate copolymer in the composition is: Including the component (A) and the component (B), the content of the component (A) in the total ethylene-vinyl acetate copolymer in the composition is 10 to 90% by weight, and the content of the component (B) is An ethylene-vinyl acetate copolymer composition, which is 10 to 90% by weight.
Component (A): Ethylene-vinyl acetate copolymer having a vinyl acetate unit content of 25 to 50% by weight Component (B): Ethylene-vinyl acetate copolymer having a vinyl acetate unit content of less than 25% by weight

[2] In [1], the difference between the vinyl acetate unit content of component (A) and the vinyl acetate unit content of component (B) is 3 to 40% by weight. Polymer composition.

[3] The ethylene-vinyl acetate copolymer according to [1] or [2], wherein the vinyl acetate unit content in the entire ethylene-vinyl acetate copolymer in the composition is 8 to 35% by weight. Composition.

[4] The ethylene-vinyl acetate copolymer according to any one of [1] to [3], wherein the proportion of the ethylene-vinyl acetate copolymer in the total polymer component in the composition is 50% by weight or more. Polymer composition.

[5] The ethylene-vinyl acetate copolymer composition according to any one of [1] to [4], further comprising the following component (C):
Component (C): Inorganic compound

[6] The ethylene-vinyl acetate copolymer according to [5], wherein the content of the component (C) is 3 to 30 parts by weight with respect to 100 parts by weight of all the polymer components in the composition. Composition.

[7] The ethylene-acetic acid according to [5] or [6], wherein the inorganic compound of component (C) is at least one hydrous inorganic compound selected from silica gel, hydrated alumina, and hydrous silicate. Vinyl copolymer composition.

[8] The ethylene-vinyl acetate copolymer composition according to any one of [1] to [7], which is an ethylene-vinyl acetate copolymer composition for tarpaulin.

[9] A fiber knitted fabric is used as a base fabric, and the layer of the ethylene-vinyl acetate copolymer composition according to any one of [1] to [8] is laminated on at least one surface thereof. Tarpaulin.

  According to the present invention, vinyl acetate content as two or more kinds of ethylene-vinyl acetate copolymers (hereinafter referred to as “EVA resin”) having different vinyl acetate unit contents (hereinafter referred to as “vinyl acetate content”). By using the component (A) having a relatively large amount and the component (B) having a relatively small amount of vinyl acetate, the component (A) has excellent flexibility and heat resistance and other properties due to the component (B). An excellent EVA resin composition is provided. Thus, although the details of the reason why each characteristic is effectively exhibited by using at least two kinds of EVA resins having different vinyl acetate contents are not clear, it is estimated as follows.

  That is, as a general theory, the component (A) is excellent in flexibility because of its high vinyl acetate content, but its heat resistance decreases because the melting point tends to be low. On the other hand, about component (B), since there is little vinyl acetate content, there exists a tendency for resin to become hard, but since melting | fusing point is high, heat resistance improves. In these resin crystals in which the components (A) and (B) are mixed, the crystal of the component (A) starts to collapse as the temperature increases, but it is presumed that the component B suppresses the movement. That is, it is inferred that the presence of the soft component (A) crystal in the hard component (B) crystal makes the crystal movement of the entire mixed resin smooth and soft. Further, the crystallinity of the component (B) is also lowered.

  In the present invention, as the component (A) and the component (B), those having a vinyl acetate content difference of 3 to 40% by weight, and the vinyl acetate content in the whole EVA resin in the composition is 8 to 35% by weight. By using as described above, the above effect can be obtained more reliably (claims 2 and 3).

  In addition, the EVA resin composition of the present invention provides good high-frequency weldability by using the EVA resin as a main component so that the proportion of the EVA resin in the total polymer component in the composition is 50% by weight or more. This is preferable (claim 4).

  In addition, the EVA resin composition of the present invention further contains an inorganic compound as a component (C) in an amount of 3 to 30 parts by weight with respect to 100 parts by weight of all polymer components in the composition. Preferably for improvement (claims 5 and 6), the inorganic compound is preferably at least one hydrous inorganic compound selected from silica gel, hydrated alumina and hydrous silicate (claim 7).

  The EVA resin composition of the present invention is excellent in flexibility, excellent in heat resistance and high-frequency welder processing, and suitable for various materials such as packaging materials, building materials, and document holders, table cloths, curtains, etc. However, it is industrially extremely useful as an EVA resin composition for tarpaulins (claim 8).

  The tarpaulin of the present invention has a fiber woven fabric as a base fabric, and is formed by laminating such a layer of the EVA resin composition of the present invention on at least one surface thereof, and has excellent flexibility and heat resistance. Excellent in workability and high-frequency welder processing, logistics materials such as flexible containers (flexible containers), civil engineering and construction materials such as construction covering sheets and curing sheets, industrial materials such as automobile hoods, tents, and water tanks Is preferably used.

It is sectional drawing which shows the welder welding method for preparation of the heat-resistant creep test piece in an Example.

  Hereinafter, embodiments of the EVA resin composition and tarpaulin of the present invention will be described in detail.

[EVA resin composition]
The EVA resin composition of the present invention comprises at least the following component (A) and component (B) as two or more types of EVA resins having different vinyl acetate contents, and component (A) in the total EVA resin in the composition: The content ratio is 10 to 90% by weight, and the content ratio of the component (B) is 10 to 90% by weight.
Component (A): EVA resin having a vinyl acetate content of 25 to 50% by weight Component (B): EVA resin having a vinyl acetate content of less than 25% by weight

<EVA resin>
Among the EVA resins contained in the composition of the present invention, if the vinyl acetate content of the component (A), which is an EVA resin having a relatively high vinyl acetate content, is larger than the above range, the vinyl acetate of the EVA resin of the entire composition is contained. When the content is increased, the heat resistance may be decreased. Conversely, when the content is less than the above range, the EVA content of the EVA resin in the entire composition may be decreased, and the flexibility may be decreased. The vinyl acetate content of component (A) is preferably 25 to 45% by weight.

  Moreover, when there is more vinyl acetate content of the component (B) which is EVA resin with comparatively little vinyl acetate content than the said range, there exists a possibility that heat resistance may fall because the vinyl acetate content of the EVA resin of the whole composition increases. There is. However, when there is too little vinyl acetate content of a component (B), there exists a possibility that a softness | flexibility may fall by reducing the vinyl chloride content of the EVA resin of the whole composition. The vinyl acetate content of the component (B) is preferably 2 to 24% by weight, more preferably 10 to 24% by weight, and still more preferably 15 to 20% by weight.

  The difference in vinyl acetate content between these components (A) and (B) (that is, the value (weight%) of (vinyl acetate content of component (A) -vinyl acetate content of component (B))) is 3 to 3 It is preferably 40% by weight, more preferably 5 to 30% by weight, and particularly preferably 10 to 25% by weight. If this difference in vinyl acetate content is too small, the effects of the present invention due to the combined use of EVA resins having different vinyl acetate contents cannot be obtained sufficiently, and if it is too much, it is difficult to achieve both flexibility and heat resistance. It becomes.

  In the present invention, the component (A) is 10 to 90% by weight, preferably 30 to 70% by weight, more preferably 40 to 60% by weight, and the component (B) in the total EVA resin in the composition. 10 to 90% by weight, preferably 30 to 70% by weight, more preferably 40 to 60% by weight, and the vinyl acetate content of the whole EVA resin in the composition is 8 to 35% by weight, further 15 to 30% by weight, In particular, it is preferably 15 to 25% by weight. The vinyl chloride content of the entire EVA resin in the composition varies depending on the vinyl chloride content of each of the component (A) and the component (B) and the blending ratio thereof. In the present invention, the vinyl acetate content of the entire EVA resin in the composition is excellent in balance of flexibility, fusing resistance, heat resistance, high frequency welding characteristics, etc., particularly when it is around 25% by weight. can get. In the present invention in which the component (A) and the component (B) are used in combination, it is surprising that the EVA resin content of the whole EVA resin in the composition is the same as that using a single EVA resin in the vicinity of 25% by weight. In comparison, an unexpected remarkable effect was found that the flexibility and anti-fusing property were excellent. In the present invention, the content of component (A) which is a high vinyl acetate content EVA resin is generally less than the above range, and the proportion of component (B) which is a low vinyl acetate content EVA resin. When the amount is more than the above range, the content of the vinyl acetate in the whole EVA resin in the composition tends to be too low and the flexibility tends to be inferior. Conversely, the proportion of the component (A) that is the high vinyl acetate content EVA resin If the proportion of the component (B) which is more than the range and the low vinyl acetate content EVA resin is less than the above range, the total vinyl acetate content of the EVA resin in the composition is excessively increased and the heat resistance tends to be inferior. In either case, it is not preferable.

  In the present invention, the EVA resin is not limited to the use of two types having different vinyl acetate contents, and three or more types of EVA resins having different vinyl acetate contents may be used. Even in this case, the object of the present invention can be achieved by keeping the vinyl acetate content of the entire EVA resin in the composition within the above range. However, using too many types of EVA resin requires labor for material input and management, and its blending design, etc., so usually two or three types of EVA resins having different vinyl acetate contents are used. It is preferable.

  The EVA resin used in the present invention has an MFR of 0.05 to 50 g / 10 min, preferably 0.1 to 40 g / 10 min measured under test conditions: 190 ° C. and 21.18 N (2.16 kg) load. Yes, more preferably 0.5 to 10 g / 10 min. When the MFR is less than 0.05 g / 10 min, the processability to a film or sheet as the EVA resin composition is inferior. On the other hand, when the MFR exceeds 50 g / 10 min, the mechanical strength as the EVA resin composition. Will be inferior. Moreover, it is preferable that two or more types of EVA resins having different vinyl acetate contents used in the present invention have similar MFRs in order to ensure mutual compatibility. Therefore, for example, the MFR of component (A) and the component The difference from the MFR of (B) is preferably 15 g / 10 min or less, particularly 10 g / 10 min or less.

  Note that the MFR and vinyl acetate content of the EVA resin according to the present invention are as described in JIS K6924-2 1997, “Plastics—Ethylene / Vinyl Acetate (E / VAC) Molding and Extrusion Materials—Part 2: How to Make Test Pieces” It is obtained by measuring in accordance with the appendix “Testing Methods for Ethylene / Vinyl Acetate Resin” in “How to Obtain Properties”.

<Other polymer components>
The EVA resin composition of the present invention preferably comprises the above-mentioned EVA resin as a main component and does not contain other polymer components. However, if necessary, in the conventional tarpaulin composition, in order to improve the properties of the EVA resin It may contain a polymer component such as a resin other than an EVA resin such as EPDM, an ethylene-α-olefin copolymer, a styrene-based copolymer, and rubber. By blending EPDM or the like, flexibility can be imparted, but conversely, heat resistance may be lowered, so adjustment of the blending amount is important. Moreover, with the EVA resin composition of the present invention, it is possible to realize a composition that sufficiently satisfies the required characteristics by using only EVA resins having different vinyl acetate contents, and obtaining materials, managing materials, and designing materials by minimizing material varieties. In order to simplify the process and when importance is attached to the recyclability of the resin, it may be preferable not to use any other polymer component other than the EVA resin.
In the EVA resin composition of the present invention, the EVA resin in the total polymer component is preferably 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 80% by weight or more. In some cases, the polymer component in the EVA resin is It is preferable to consist essentially of EVA resin.

<Inorganic compounds>
The EVA resin composition of the present invention preferably contains an inorganic compound as component (C) in order to improve high-frequency welder processability and the like. In particular, in the present invention, when heat resistance is required, it is preferable to add an inorganic compound such as silica.

As the component (C), a water-containing inorganic compound that is an inorganic compound to which water is bonded is preferable. Typically, for example, silica gel [SiO ₂ .nH ₂ O], hydrated alumina [Al ₂ O ₃ .nH ₂ O], hydrated aluminum silicate _{[Al 2 O 3 · mSiO 2 ·} nH 2 O ], hydrated calcium silicate [CaO · mSiO ₂ · nH ₂ O], hydrated magnesium silicate [MaO · mSiO ₂ · nH ₂ O], such as A hydrous silicate etc. are mentioned. These can be used alone or in combination of two or more. The moisture introduced by such an inorganic compound contributes to heat generation when performing high-frequency welder processing, so that the high-frequency welder workability can be greatly improved, for example, by increasing the thermal welding strength.

  In the EVA resin composition of the present invention, the content of the component (C) inorganic compound is 3 to 30 parts by weight, more preferably 5 to 25 parts by weight, particularly 5 to 15 parts by weight, based on 100 parts by weight of the total polymer component. It is preferable that If the content of the inorganic compound is too small, the effect of improving the high-frequency welder workability due to the blending of the inorganic compound cannot be sufficiently obtained, and if it is too large, the flexibility may be lowered.

  In particular, in the EVA resin composition of the present invention, among two or more types of EVA resins having different vinyl acetate contents, high-frequency welder weldability can be ensured with the high vinyl acetate content of the aforementioned high vinyl acetate content component (A). Since it can do, compared with the conventional EVA resin composition for tarpaulins, content of an inorganic compound can be reduced and it is effective also for the improvement of a softness | flexibility also in this point.

<Other ingredients>
In the EVA resin composition of the present invention, various additives usually used for thermoplastic resins in addition to the above-described polymer component and inorganic compound, as long as they do not impair the effects of the present invention, if necessary, for example, , Antioxidants, heat stabilizers, light stabilizers, UV absorbers, nucleating agents, neutralizing agents, lubricants, antistatic agents, antiblocking agents, slipping agents, antifogging agents, dispersants, flow improvers, A release agent, an adhesion-imparting agent, a flame retardant, a colorant, a filler other than the component (C), and the like may be added. These components may be contained in each component, and may be mix | blended at the time of manufacture of an EVA resin composition.

<MFR of composition>
The EVA resin composition of the present invention preferably has an MFR of 0.1 to 50 g / 10 minutes, particularly 0.3 to 30 g / 10 minutes, measured under the above conditions. When the MFR is less than 0.1 g / 10 minutes, the molding processability to a film or sheet as the EVA resin composition is inferior, which is not preferable. On the other hand, when the MFR exceeds 50 g / 10 minutes, the mechanical strength and workability are not preferable. Is not preferable.

To adjust a given MFR, the following formula:
100 × log (MFR _X ) = W _A log (MFR _A ) + W _B log (MFR _B ) +.
The ratio and MFR of each component can be adjusted based on the above. _Here, W A, _{W B,} respectively, represent the proportion of the component (A), component (B) _{(wt%), MFR X, MFR A} , respectively MFR _B, EVA resin composition, component (A) Represents the MFR of the component (B).

<Method for adjusting and molding composition>
The EVA resin composition of the present invention requires a high-vinyl acetate EVA resin as the component (A) and a low-vinyl acetate EVA resin as the component (B), more preferably an inorganic compound as the component (C). After mixing uniformly with other polymer components and additives, etc. used by tumbler blender, ribbon blender, V-type blender, Henschel mixer, etc., single or twin screw extruder, roll, Banbury mixer, kneader, The EVA resin composition is prepared by melt-kneading with a lavender or the like, and the EVA resin composition is melt-extruded into a film shape or a sheet shape by a calendering process or a molding machine equipped with a T die or an annular die, and then cooled. Etc.

[Tapollin]
The tarpaulin of the present invention has a fiber knitted fabric as a base fabric, and a layer of the EVA resin composition is laminated on at least one side, preferably on both sides. For example, a calendering method, an extrusion laminating method, a dry laminating method, and an impregnation method can be used. Among these, a calendar processing method is preferable.

  Specifically, the tarpaulin of the present invention is prepared by forming the EVA resin composition prepared above into a sheet shape by a calender roll and melt laminating it on a base fabric, or forming it into a sheet form from a sheet forming machine equipped with a T die. It is manufactured by melt-extrusion and extrusion laminating and laminating on a base fabric, or dry laminating and laminating a molded sheet and base fabric using an adhesive.

  In addition, the temperature of the EVA resin composition at the time of melt lamination on one side or both sides of the base fabric is usually about 140 to 160 ° C., for example, in the case of a calendering method, and the thickness of the EVA resin composition layer Is about 100 to 1000 μm per surface.

Further, as the fiber knitted fabric constituting the base fabric, those conventionally used for this type of base fabric are used, for example, synthetic fibers such as polyester fibers, polyamide fibers, polyolefin fibers, polyacryl fibers, or the like. Woven fabrics such as plain weave, twill weave and satin weave such as natural fibers such as cotton and hemp, or knitted fabrics.
The thickness of the fiber is about 200 to 1000 denier. For example, in the case of plain weave, the number of driven-in is about (10-30) × (15-35) / inch. These fiber knitted and woven fabrics generally have a width of about 0.5 to 3 m and a thickness of about 0.2 to 1 mm.

[Usage]
The EVA resin composition of the present invention is preferably used for tarpaulin applications, but in addition, it is formed into a desired shape by high-frequency welder processing as a film or sheet or the like, such as a surface protection material for fashion bags, decorative plywood, etc. It can also be used for packaging materials, wallpaper materials, building materials such as interior materials, and various miscellaneous materials such as document holders, desk mats, tablecloths, curtains, stationery, and toys.

In addition, the tarpaulin of the present invention using such an EVA resin composition of the present invention is cut into a desired shape by cutting, high-frequency welder, etc. It is suitably used for civil engineering and building materials such as sheets and curing sheets, and industrial materials such as automobile hoods, tents, and water tanks.
In addition, the high frequency welder process in that case is normally made by the welding time of 1 to 60 second in the frequency range of 10-100 MHz.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

  In the following, as the EVA resin composition raw material, the following were used.

<EVA resin>
EVA-18; EVA resin content = 18% by weight, MFR (190 ° C.) = 1.0 g / 10 min EVA resin (“Evertate CV2166” manufactured by Sumitomo Chemical Co., Ltd.)
EVA-20; vinyl acetate content = 20 wt%, MFR (190 ° C.) = 2.5 g / 10 min EVA resin (“Novatec EVA LV541” manufactured by Nippon Polyethylene Co., Ltd.)
EVA-25; EVA resin content = 25% by weight, MFR (190 ° C.) = 2.0 g / 10 min EVA resin (“Evaflex P2505” manufactured by Mitsui DuPont Polychemical Co., Ltd.)
EVA-28; EVA resin content = 28% by weight, MFR (190 ° C.) = 1.0 g / 10 min EVA resin (“Evaflex EV270” manufactured by Mitsui DuPont Polychemical Co., Ltd.)
EVA-33; EVA resin content = 33% by weight, MFR (190 ° C.) = 1.0 g / 10 min EVA resin (“Evaflex EV170” manufactured by Mitsui DuPont Polychemical Co., Ltd.)
EVA-41; EVA resin content = 41% by weight, MFR (190 ° C.) = 2.0 g / 10 min EVA resin (“Evaflex EV40LX” manufactured by Mitsui DuPont Polychemical Co., Ltd.)

<Other polymer components>
(Ethylene copolymer (PE))
d (0.868); density = 0.868 g / cm ³ , MFR (190 ° C.) = 0.5 g / 10 min ethylene copolymer (“ENGAGE EG8150” manufactured by DuPont Dow Elastomers)
d (0.88); density = 0.880 g / cm ³ , MFR (190 ° C.) = 2.2 g / 10 min ethylene copolymer (“Kernel KF241” manufactured by Nippon Polyethylene Co., Ltd.)
d (0.903); Density = 0.868 g / cm ³ , MFR (190 ° C.) = 2.0 g / 10 min ethylene copolymer (“Kernel KF261” manufactured by Nippon Polyethylene Co., Ltd.)

(Elastomer)
EPDM: Mooney viscosity ML _{1 + 4} (100 ° C.) = 90 EPDM resin (“EP57C” manufactured by JSR Corporation)
SEBS; density = 0.89 g / cm ³ , styrene content = 10%, MFR (230 ° C.) = 3.5 g / 10 min HSBR resin (“DYNARON 1320P” manufactured by JSR Corporation)

<Inorganic compounds>
Silica gel: “Tokushiru GU” manufactured by Tokuyama Corporation, chemical formula: SiO ₂ · nH ₂ O, content: 88% by weight or more (based on dry weight)

[Examples 1-7, Comparative Examples 1-9]
Each component shown in Table 1 was mixed in the ratio shown in Table 1, and stirred well. Thereafter, the mixture was uniformly kneaded at 160 ± 10 ° C. for 10 minutes using a test roll manufactured by Tokuden Co., Ltd., and a 0.30 mm film sheet was taken out from the kneaded composition on a carrier paper.

  The vinyl acetate content of the EVA resin composition of the obtained film sheet was calculated from the blending ratio of the EVA resin used, and the results are shown in Table 1.

  Next, each obtained film sheet was evaluated by the method shown below, and the results are shown in Table 1.

(1) Tensile modulus In accordance with JIS-K-7127 “Plastic film and sheet tensile test method”, using a Shimadzu tensile tester “AGS-500D”, type 2 test piece (total length 115 mm, parallel part Evaluation was performed by conducting a tensile test at a test speed of 5 mm per minute for a width of 6 mm and a distance between grips of 80 mm.

(2) Fusing resistance Two test pieces cut into a width of 20 mm and a length of 30 mm from each sheet are stacked and sandwiched between two glass plates, placed in a heating bath at 80 ° C., and a load of 2 kg is applied. Leave for 24 hours, visually observe the presence or absence of adhesion, cracks, damage, film peeling, and other abnormalities on the surface after standing, very good anti-fusing property (◯), practical level of anti-fusing property (△), Evaluation was based on poor adhesion resistance (x).

(3) Tensile strength No. 4 test piece (total length 120mm, parallel part) using Shimadzu tensile tester "AGS-500D" in accordance with JIS-K-7127 "Plastic film and sheet tensile test method" Evaluation was conducted by conducting a tensile test at a test speed of 200 mm / min and an ambient temperature of 60 ° C. for a width of 10 mm and a distance between grips of 50 mm.

(4) High-frequency welding suitability With a high-frequency welder ("YC7000F" manufactured by Yamamoto Vinita), the tuning adjusters were set to 55, 56, and 57, and high-frequency welding was performed for 7 seconds respectively, and the welding state was visually confirmed.

In addition, after mixing and heating with a Banbury mixer at the blending ratio of the EVA resin compositions of Example 4 and Comparative Examples 2, 3, and 6 in Table 1, the mixture was uniformly kneaded with a mixing roll and heated at around 150 ° C. The sheet is molded into a sheet with a thickness of 0.3 mm using a calendered roll, welded and laminated on both sides of a polyester plain woven fabric (fiber 750 denier, number of driven 20.5 × 21 / inch), and a tarpaulin with a thickness of 0.75 mm is formed. Manufactured. The obtained tarpaulins were evaluated by the methods shown below, and the results are shown in Table 2.

(5) Fusing resistance In the same evaluation style as "(2) Fusing resistance" in the sheet, the temperature in the heating tank was 70 ° C.

(6) Heat-resistant creep As shown in FIG. 1, the end portions of the two tarpaulin specimens 1A and 1B were overlapped on a straight line with a width of 8 cm, and the welder was overlapped with a 3 cm width × 18 cm welder blade. Hung from the part. Thereafter, a 2 cm interval was provided, and the welder was further hung with the same welder blade. In the drawing, the hatched and dotted portions are welder welds 3. As a high-frequency welder, “YO-5A type” manufactured by Yamamoto Vinita was used, and welding was performed under the conditions of a welding time of 10 seconds, an anode current of 0.34 A, and a cooling time of 8 seconds.

  A sample having a width of 3 cm and a length of 30 cm or more including a welded joint is collected from the tarpaulin welded and bonded under the above conditions, and this is used as a heat-resistant creep test piece. This test piece is placed on a creep tester and heated to 40 ° C. A heat resistant creep test was conducted for 24 hours under a load of 40 kgf. The results were evaluated based on good heat resistant creep (◯), practical heat resistant creep level (Δ), and poor heat resistant creep (×).

(7) Flexural rigidity Take a 30mm x 170mm strip test piece from the tarpaulin, fix both ends of the test piece with two sets of chucks with a width of 40mm, and set the distance between the two chucks to 60mm. The test piece is bent between the chucks to form an arc bridge, and the apex portion of the arc bridge of the test piece has an inverted conical shape with a sphere having a radius of 5 mm at the tip and a length of 40 mm. The maximum load (unit: N) until the test piece was buckled was measured with a strain gauge compressed at a speed of 60 mm / min with a pressing tool equipped with a head and connected to the pressing tool (23 ° C., 50 % RH). The smaller this value, the better the flexibility.

  Tables 1 and 2 show the following.

Comparative Examples 1 and 2 are tarpaulin EVA resin compositions used for general flexible containers.
Comparative Example 5 is an EVA resin composition for tarpaulin used in a heat-resistant flexible container, and heat resistance is increased by adding high-density PE, but it becomes hard (elastic modulus increases).
In Comparative Examples 3 and 4, flexibility was examined, and PE having a low density was added to soften it (lower the elastic modulus), but the anti-fusing performance deteriorates. Moreover, since the total vinyl acetate content falls and the silica gel content is also small in the comparative example 3, high frequency weldability falls.
Comparative examples 6 and 7 were also examined for flexibility, and rubber was blended and softened (lowering the elastic modulus), but the high-temperature tensile strength decreased.
Comparative Example 8 also examined flexibility, and is a composite of Comparative Examples 3 and 4 and Comparative Examples 6 and 7. In this example, the vinyl acetate content is further reduced, and the high frequency weldability is greatly reduced.
Comparative Example 9 was also examined for flexibility, and softened with a single EVA having a high vinyl acetate content, but poor fusion resistance. In addition, the high temperature tensile strength also decreases.

  On the other hand, in Examples 1 to 7 of the present invention, by using a mixture of two types of EVA resins having different vinyl acetate contents, compared to the comparative example, Flexibility can be increased (decrease in elastic modulus) without reducing the high temperature tensile strength. Moreover, since the vinyl acetate content is high, for example, Examples 3 and 4 do not decrease the high frequency weldability as in Comparative Example 3 even if the amount of silica gel is reduced.

  From the above results, it can be seen that according to the present invention, an EVA resin composition and a tarpaulin excellent in flexibility, heat resistance and high-frequency welder processability are provided.

The EVA resin composition of the present invention is excellent in flexibility, heat resistance and high-frequency welder processability, so it can be used for packaging materials, building materials, and various miscellaneous materials such as document holders, tablecloths, and curtains. It can be used suitably.
In addition, tarpaulin in which the EVA resin composition is laminated on the surface of the base fabric is excellent in flexibility, heat resistance and high-frequency welder workability, so that it can be used for logistics materials such as flexible containers, construction coating sheets, curing It can be suitably used for civil engineering and building materials such as sheets, industrial materials such as automobile hoods, tents, and water tanks, and logistics materials such as flexible containers. In particular, since the tarpaulin of the present invention is excellent in flexibility and excellent in folding workability, it is suitable as a material for manufacturing a flexible container.

1A, 1B Tarpaulin specimen 2 Overlapping part 3 Welder welding part

Claims (9)

An ethylene-vinyl acetate copolymer composition comprising two or more types of ethylene-vinyl acetate copolymers having different vinyl acetate unit contents, wherein the ethylene-vinyl acetate copolymer in the composition comprises the following components (A ) And component (B), the content of component (A) in the total ethylene-vinyl acetate copolymer in the composition is 10 to 90% by weight, and the content of component (B) is 10 to 90%. An ethylene-vinyl acetate copolymer composition, characterized in that the content is% by weight.
Component (A): Ethylene-vinyl acetate copolymer having a vinyl acetate unit content of 25 to 50% by weight Component (B): Ethylene-vinyl acetate copolymer having a vinyl acetate unit content of less than 25% by weight   The ethylene-vinyl acetate copolymer composition according to claim 1, wherein the difference between the vinyl acetate unit content of the component (A) and the vinyl acetate unit content of the component (B) is 3 to 40% by weight. object.   3. The ethylene-vinyl acetate copolymer composition according to claim 1, wherein the vinyl acetate unit content in the entire ethylene-vinyl acetate copolymer in the composition is 8 to 35% by weight.   The ethylene-vinyl acetate copolymer composition according to any one of claims 1 to 3, wherein the proportion of the ethylene-vinyl acetate copolymer in all polymer components in the composition is 50% by weight or more. object. The ethylene-vinyl acetate copolymer composition according to any one of claims 1 to 4, further comprising the following component (C).
Component (C): Inorganic compound   6. The ethylene-vinyl acetate copolymer composition according to claim 5, wherein the content of the component (C) is 3 to 30 parts by weight with respect to 100 parts by weight of all the polymer components in the composition.   The ethylene-vinyl acetate copolymer composition according to claim 5 or 6, wherein the inorganic compound of component (C) is at least one hydrous inorganic compound selected from silica gel, hydrated alumina, and hydrous silicate. object.   8. The ethylene-vinyl acetate copolymer composition according to claim 1, which is an ethylene-vinyl acetate copolymer composition for tarpaulin.   A tarpaulin comprising a textile knitted fabric as a base fabric and a layer of the ethylene-vinyl acetate copolymer composition according to any one of claims 1 to 8 laminated on at least one surface thereof. .

Images