JP2013093392A - Manufacturing method of ethylene-vinyl acetate copolymer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a thick EVA sheet having no air bubble inside the sheet and having an improved yield.SOLUTION: A manufacturing method of an ethylene-vinyl acetate copolymer sheet comprises a step of mixing a resin composition containing an ethylene-vinyl acetate copolymer and then rolling with a calender roll 25, where the ethylene-vinyl acetate copolymer sheet has a thickness of 0.7 to 2.0 mm and the temperature of the resin composition supplied to the calender roll 25 is adjusted to 70 to 90°C.

Description

  The present invention relates to a method for producing an ethylene-vinyl acetate copolymer sheet used for solar cell sealing films, laminated glass interlayer films, and the like by calendering.

  Since an ethylene-vinyl acetate copolymer (hereinafter also referred to as EVA) sheet is excellent in transparency and adhesiveness, an antireflection layer and the like are provided in addition to a sealing film for solar cells and an intermediate film for laminated glass. It is widely used as an adhesive film for attaching an optical filter having a display to a display.

  When the EVA sheet is used as a solar cell sealing film, for example, as shown in FIG. 3, the surface-side transparent protective member 11 made of a glass substrate or the like, the solar cell sealing film 13A, and the connection tab 15 are electrically connected. A plurality of solar cell cells 14, a solar cell sealing film 13 </ b> B, and a back surface side protective member (back cover) 12 are laminated in this order, degassed under reduced pressure, and then heated and pressurized. Used for manufactured solar cells. The solar cell 14 is sealed by the solar cell sealing films 13A and 13B, and the respective members are bonded and integrated (Patent Document 1).

  Moreover, when using as an intermediate film for laminated glass, as shown in FIG. 4, the laminated glass manufactured by sandwiching the intermediate film 5 for laminated glass 5 between the two glass plates 7A and 7B and crosslinking and curing the laminated glass. Used for. Laminated glass is mainly used in windows of automobiles and buildings, and the interlayer film 5 for laminated glass prevents penetration resistance and scattering of broken glass (Patent Document 2).

  The EVA sheet used for this purpose is manufactured by forming a film containing a composition containing additives such as an ethylene-vinyl acetate copolymer and a crosslinking agent by various molding methods such as calendar molding, extrusion molding, and press molding. Is done. Among them, calender molding has a high production capacity and is generally widely used for producing sheets.

  As an apparatus used for calendar molding, for example, a calendar molding machine as described in Patent Document 3 is generally used. In this calendering machine, as shown in FIG. 1, a resin composition (raw material) containing EVA is put into a kneader 21, and after melt-kneading, the kneaded material 20 is conveyed by a conveyor belt 22 and supplied to a kneading roll 23. After that, the kneaded material formed into a film by the kneading roll 23 is conveyed by the conveyor belt 24. The kneaded material is rolled with a calendar roll 25 (first roll 25A, second roll 25B, third roll 25C, fourth roll 25D), and the rolled sheet is taken out with a take-off roll 26, and then a plurality of cooling rolls. The EVA sheet 30 obtained by cooling at 28 is wound up by a winder 29. When the EVA sheet is used for an interlayer film for laminated glass or a sealing film for solar cell, it is usually used after being formed to a thickness of about 0.4 to 0.6 mm (see Patent Documents 1 and 2).

JP 2008-091772 A JP 2007-319552 A JP 2007-160740 A

  By the way, in such calender molding, before rolling the resin composition with a calender roll, it is generally avoided that bubbles are generated in the resin composition at the time of kneading or in the bank 31 (see FIG. 1) where the resin composition stays. It is a problem that cannot be done. Even if bubbles are generated during production of an EVA sheet having a commonly used film thickness, there is no problem because the bubbles are removed during the rolling process with a calender roll or during lamination during product production.

  However, in the case of a thick EVA sheet, there is a problem that large bubbles remain because the clearance between the calender rolls in the rolling process is large, and the remaining bubbles do not escape even during lamination, resulting in poor production. A thick EVA sheet is used to prevent cell cracking during the production of laminated glass using a thick transparent substrate (glass) or a solar cell using a thin solar cell, and its demand has been increasing in recent years. Therefore, measures that can solve this problem are desired.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for producing a thick-film EVA sheet in which bubbles are prevented from remaining in the resulting sheet and yield is improved. .

  The above object is a method for producing an ethylene-vinyl acetate copolymer sheet comprising a step of kneading a resin composition containing an ethylene-vinyl acetate copolymer and rolling with a calender roll, wherein the ethylene-vinyl acetate copolymer comprises the steps of: The thickness of the polymer sheet is 0.7 to 2.0 mm, and the temperature of the resin composition supplied to the calender roll is adjusted to 70 to 90 ° C. This is achieved by a method for producing a polymer sheet.

  When producing a thick-film EVA sheet by conventional calendering, the temperature of the resin composition is lowered before the resin composition is kneaded and supplied to the calender roll, resulting in a decrease in fluidity. Therefore, there is a problem that bubbles remain without being removed. When producing an EVA sheet having a thickness of 0.7 to 2.0 mm as in the configuration of the present invention, by adjusting the temperature of the resin composition supplied to the calendar roll to 70 to 90 ° C., Since it can be rolled with a calender roll with good fluidity, it becomes possible to allow bubbles to escape during the rolling.

  Preferred embodiments of the present invention are as follows.

(1) The kneading is performed with a kneading roll, and the temperature adjustment is performed in a conveying means arranged between the kneading roll and the calender roll and conveying the kneaded resin composition to the calender roll. To do. Like this structure, the temperature of a resin composition can be efficiently maintained in the range of 70-90 degreeC by heating a resin composition in a conveyance means.

(2) The heating is performed by irradiating the resin composition with heat rays. The temperature can be adjusted simply and quickly.

(3) A conveyor belt is used as the conveying means, and the temperature is adjusted by setting the belt temperature of the conveyor belt to 40 to 70 ° C. It is possible to prevent a decrease in temperature by a simple method and maintain the resin composition at 70 to 90 ° C.

(4) The ethylene-vinyl acetate copolymer sheet has a thickness of 0.7 to 1.0 mm. Even in the thick film EVA sheet, when the thickness is 0.7 to 1.0 mm, the remaining of the bubbles can be surely prevented.

(5) The melt flow rate (measured at 190 ° C. under a load of 21.18 N according to JIS K7210) of the ethylene-vinyl acetate copolymer is 35 g / 10 minutes or less. By setting the fluidity of EVA within this range, it is possible to reliably prevent bubbles from remaining.

(6) The resin composition includes a crosslinking agent. According to the said temperature, even when a crosslinking agent is contained, an EVA sheet | seat can be manufactured, without making a crosslinking agent react.

(7) The ethylene-vinyl acetate copolymer sheet is a solar cell sealing film or a laminated glass interlayer film. The EVA sheet formed by the production method of the present invention can be suitably used as a solar cell sealing film or a laminated glass interlayer film.

  Moreover, this invention provides the ethylene-vinyl acetate copolymer sheet manufactured by the said manufacturing method.

  According to the method for producing an ethylene-vinyl acetate copolymer sheet according to the present invention, bubbles can be prevented from remaining inside the EVA sheet, and the yield can be improved. Therefore, a thick film EVA sheet having good adhesion and appearance can be obtained with high productivity.

It is the schematic which shows an example of a calendar molding machine. It is the schematic which shows the example of arrangement | positioning of a calendar roll. It is a schematic sectional drawing which shows an example of a solar cell. It is a schematic sectional drawing which shows an example of a laminated glass.

  Hereinafter, the manufacturing method of the EVA sheet | seat which concerns on this invention is demonstrated in detail with reference to drawings. FIG. 1 is a schematic view showing an example of a calendar molding machine used in the production method of the present invention.

  In this calendering machine, an ethylene-vinyl acetate copolymer and, if necessary, a resin composition (raw material) containing additives such as a crosslinking agent are charged into a kneading machine 21, and after melt-kneading, the kneaded product 20 is transferred by a conveyor belt 22. It is conveyed and supplied to the kneading roll 23. The kneaded material that has been heated and kneaded by the kneading roll 23 (usually 70 to 90 ° C.) to form a film is conveyed by the conveyor belt 24, and the first roll 25A and the second roll 25B that are calendar rolls (generally also called heat rolls). Supply between. At this time, a bank 31 in which the resin composition is retained is generated in the gap between the first roll 25A and the second roll 25B. The resin composition supplied to the calendar roll 25 is rolled by the first roll 25A, the second roll 25B, the third roll 25C, and the fourth roll 25D, and the rolled sheet is taken out by the take-off roll 26. Then, it cools with the 5 cooling rolls 28, and the EVA sheet 30 wound up by the winder 29 is obtained by winding the obtained EVA sheet 30 in the roll shape.

  In the present embodiment, the first roll 25A and the second roll 25B are arranged so as to be substantially horizontal, the third roll 25C is arranged vertically downward with respect to the second roll 25B, and the third roll 25C The 4th roll 25D is arrange | positioned so that it may become substantially horizontal. The embossing roll 27 is appropriately provided when the sheet surface needs to be processed to be uneven, and is disposed after the take-off roll 26.

  What is characteristic in the method for producing an EVA sheet of the present invention is that when producing a thick EVA sheet having a thickness of 0.7 to 2.0 mm after the film formation, the calender rolls 25A and 25B The resin composition supplied between them is adjusted to a temperature of 70 to 90 ° C, preferably 80 to 90 ° C. Thus, entrainment of bubbles can be prevented by adjusting the temperature of the resin composition supplied to the calender roll 25 and preventing the fluidity from decreasing. If the temperature is lower than 70 ° C., the fluidity is lowered, and bubbles generated in the bank 31 may be left in the sheet during kneading. If the temperature exceeds 90 ° C., the crosslinking agent contained in the EVA resin composition reacts. A cross-linking reaction may occur. In the present invention, the temperature immediately before being supplied to the calendar roll 25, that is, the temperature of the resin composition when supplied to the calendar rolls 25A and 25B shown in FIG. Moreover, it is preferable that the thickness of the EVA sheet after film formation is 0.7 to 1.0 mm from the viewpoint that bubbles can be reliably prevented from entraining.

  In the present invention, the heating means for adjusting the temperature is not particularly limited as long as the resin composition can be adjusted in the range of 70 to 90 ° C. For example, a method in which a heater is installed above the conveyor belt 24 and the resin composition moving on the conveyor belt 24 is directly heated, a heater is installed inside the conveyor belt 24, and the resin composition is indirectly transferred by the heated belt. And a method of heating the conveyor belt 24 by performing a cycle in which the resin composition is conveyed from the kneading roll 23 onto the conveyor belt 24 and then returned to the kneading roll 23 for a certain time. At this time, the belt temperature of the conveyor belt 24 is preferably 40 to 70 ° C. By setting it as this temperature, the temperature fall of the resin composition after heat-kneading can be prevented efficiently, and it can adjust to the said temperature. The length of the conveyor belt 24 in the length direction is generally 10 to 20 m.

  The temperature of the resin composition can be measured by bringing a contact thermometer into direct contact with the resin composition, or using a non-contact thermometer such as an infrared method or a light temperature method. It is preferable to measure the temperature with a non-contact thermometer because it does not affect the workability of the EVA sheet. Moreover, the calendar molding machine may be provided with a cooling means for performing cooling when the resin composition is not intended to exceed 90 ° C. Examples of the cooling means include a cooler that blows cold air made of an inert gas such as nitrogen or air to the resin composition, and such a cooler may be installed above the conveyor belt 24, for example.

  Further, the calender molding machine may be provided with a control means (not shown) for adjusting ON / OFF of the heating means and the cooling means and strength adjustment according to information from the thermometer. This makes it possible to constantly monitor the temperature and control the resin composition to a temperature in the range of 70 to 90 ° C.

  The rotation speed of the calendar rolls 25A, 25B, 25C, and 25D is preferably 1 to 30 m / min, particularly 1 to 20 m / min. The rotation speed is usually set to satisfy 25A <25B <25C <25D. The temperature of the calendar roll is preferably 50 to 90 ° C, particularly 80 to 90 ° C.

  The thickness of the EVA sheet can be set by setting the interval between the calendar rolls 15C and 15D so as to have a desired sheet thickness. Thereby, an EVA sheet having a thickness of 0.7 to 2.0 mm can be obtained.

  In addition, in this invention, the arrangement | positioning form of a calendar roll is not specifically limited, All the arrangement | positioning forms conventionally used properly according to the objective can be employ | adopted. For example, as shown in FIG. 2, (a) 3 in-line type, (b) 3 incline type, (c) 4 in-line type, (d) reverse L type, (e) Z type, (f) incline Z type, (g) 5 type etc. are mentioned.

  Hereinafter, the EVA resin composition for producing an EVA sheet will be described in detail.

[Ethylene-vinyl acetate copolymer (EVA)]
The vinyl acetate content in EVA is preferably 20 to 35% by mass, particularly 22 to 26% by mass. If the amount is less than 20% by mass, the workability of the EVA sheet may be reduced. If the amount exceeds 35% by mass, carboxylic acid, alcohol, and the like are generated, and foaming is likely to occur at the interface with the member in contact with the EVA sheet. There is a fear.

  Moreover, the melt flow rate (MFR) of EVA is preferably 35 g / 10 min or less, particularly 2 to 6 g / 10 min. If it is too low, the fluidity is lowered, and the generated bubbles may be difficult to escape. If it is higher than this range, the workability may be lowered. In addition, the value of the melt flow rate (MFR) in this invention is measured based on the conditions of 190 degreeC and load 21.18N according to JISK7210.

[Crosslinking agent]
In the present invention, the resin composition containing EVA preferably contains a crosslinking agent for forming a crosslinked structure of the ethylene-vinyl acetate copolymer. By forming a crosslinked structure, the sealing performance when used in a solar cell module and the adhesive performance when used in laminated glass can be improved. As the cross-linking agent, it is preferable to use an organic peroxide because an EVA sheet having improved temperature dependency of adhesive strength, moisture resistance, and penetration resistance can be obtained.

  Any organic peroxide may be used as long as it decomposes at a temperature of 100 ° C. or higher and generates radicals. The organic peroxide is generally selected in consideration of the film formation temperature, the adjustment conditions of the composition, the curing temperature, the heat resistance of the adherend, and the storage stability.

  Examples of the organic peroxide include a benzoyl peroxide curing agent, tert-hexyl peroxypivalate, tert-butyl peroxypivalate, and tert-butyl peroxy 2 from the viewpoint of processing temperature and storage stability of the resin. -Hexyl carbonate, 3,5,5-trimethylhexanoyl peroxide, di-n-octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethyl Hexanoate, succinic acid peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (2-ethylhexanoylperoxy) Hexane, 1-cyclohexyl-1-methylethyl peroxide 2-ethylhexanoate, tert-hexylperoxy-2-ethylhexanoate, 4-methylbenzoyl peroxide, tert-butylperoxy-2-ethylhexanoate, m-toluoyl + benzoyl peroxide, benzoyl Peroxide, 1,1-bis (tert-butylperoxy) -2-methylcyclohexanate, 1,1-bis (tert-hexylperoxy) -3,3,5-trimethylcyclohexanate, 1,1 -Bis (tert-hexylperoxy) cyclohexanate, 1,1-bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (tert-butylperoxy) cyclohexane, 2, , 2-bis (4,4-di-tert-butylperoxysic Hexyl) propane, 1,1-bis (tert-butylperoxy) cyclododecane, tert-hexylperoxyisopropyl monocarbonate, tert-butylperoxymaleic acid, tert-butylperoxy-3,3,5-trimethyl Hexane, tert-butylperoxylaurate, 2,5-dimethyl-2,5-di (methylbenzoylperoxy) hexane, tert-butylperoxyisopropyl monocarbonate, tert-butylperoxy-2-ethylhexyl monocarbonate, Examples include tert-hexyl peroxybenzoate, 2,5-di-methyl-2,5-di (benzoylperoxy) hexane, and the like.

  As the benzoyl peroxide-based curing agent, any can be used as long as it decomposes at a temperature of 70 ° C. or higher to generate radicals, and those having a decomposition temperature of 50 hours or higher with a half-life of 10 hours are preferable, It can be appropriately selected in consideration of preparation conditions, film formation temperature, curing (bonding) temperature, heat resistance of the adherend, and storage stability. Usable benzoyl peroxide curing agents include, for example, benzoyl peroxide, 2,5-dimethylhexyl-2,5-bisperoxybenzoate, p-chlorobenzoyl peroxide, m-toluoyl peroxide, 2, Examples include 4-dichlorobenzoyl peroxide and t-butyl peroxybenzoate. The benzoyl peroxide curing agent may be used alone or in combination of two or more.

  As organic peroxides, in particular 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 1,1-bis (tert-hexylperoxy) -3,3,5-trimethylcyclohexane, Tert-butyl peroxy 2-hexyl carbonate is preferred.

  The content of the organic peroxide is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. If the content of the organic peroxide is small, the durability performance after crosslinking obtained may be lowered, and if it is increased, the compatibility with the copolymer may be deteriorated.

[Crosslinking aid]
The resin composition containing EVA may further contain a crosslinking aid as necessary. The cross-linking aid can improve the gel fraction of the ethylene-vinyl acetate copolymer and improve the adhesion and durability of the EVA sheet.

  The content of the crosslinking aid is generally 10 parts by mass or less, preferably 0.1 to 5 parts by mass, more preferably 0.1 to 2.5 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. Used in the department. Thereby, the EVA sheet | seat which is excellent in adhesiveness is obtained.

  Examples of the crosslinking aid (compound having a radical polymerizable group as a functional group) include trifunctional crosslinking aids such as triallyl cyanurate and triallyl isocyanurate, and (meth) acrylic esters (eg, NK ester) ) Monofunctional or bifunctional crosslinking aids. Of these, triallyl cyanurate and triallyl isocyanurate are preferable, and triallyl isocyanurate is particularly preferable.

[Adhesion improver]
The EVA sheet may further contain an adhesion improver in order to improve the adhesion performance when used for laminated glass and solar cell modules. As the adhesion improver, a silane coupling agent can be used. Thereby, it becomes possible to form an EVA sheet having an excellent adhesive force. As silane coupling agents, γ-chloropropylmethoxysilane, vinylethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane , Γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- Mention may be made of (aminoethyl) -γ-aminopropyltrimethoxysilane. These silane coupling agents may be used alone or in combination of two or more. Of these, γ-methacryloxypropyltrimethoxysilane is particularly preferred.

  The content of the silane coupling agent is 5 parts by mass or less, preferably 0.1 to 2 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

[Others]
EVA sheet is used to improve or adjust various physical properties (mechanical strength, optical properties, heat resistance, light resistance, crosslinking speed, etc.) of the film as needed, plasticizer, acryloxy group-containing compound, methacryloxy group. Various additives such as a containing compound and / or an epoxy group-containing compound, an ultraviolet absorber, a light stabilizer, and an anti-aging agent may be included.

  Since the EVA sheet produced by the production method of the present invention has no bubbles inside and has good adhesion and appearance, it can be preferably used as an interlayer film for laminated glass or a sealing film for solar cells. .

  When used as an interlayer film for laminated glass, for example, a laminated glass is manufactured by interposing an EVA sheet (intermediate film) manufactured according to the present invention between two transparent substrates and joining them together. . As the transparent substrate, for example, a plastic film may be used in addition to a glass plate such as a silicate glass, an inorganic glass plate, and a non-colored transparent glass plate. Examples of the plastic film include a polyethylene terephthalate (PET) film, a polyethylene aphthalate (PEN) film, and a polyethylene butyrate film, and a PET film is preferred. The thickness of the transparent substrate is generally about 0.05 to 20 mm.

  Laminated glass is usually produced by sandwiching an EVA sheet between two transparent substrates, laminating the laminate, degassing it under reduced pressure, and pressing it under heating (high temperature laminating step) to form an EVA sheet. The ethylene-vinyl acetate copolymer contained is crosslinked and cured, and the layers are joined and integrated. In the case of crosslinking and curing, the laminate is generally heat-treated at 100 to 150 ° C., particularly around 135 ° C. for 10 minutes to 120 minutes, preferably 10 minutes to 60 minutes. The cross-linking curing may be performed after pre-bonding at a temperature of, for example, 80 to 120 ° C. The heat treatment is particularly preferably, for example, at 135 ° C. for 10 to 30 minutes (atmospheric temperature). Moreover, it is preferable to perform the said heat processing, applying the press pressure of 0-800 KPa to a laminated body. Although cooling of the laminated body after crosslinking is generally performed at room temperature, the faster the cooling, the better.

  Moreover, when using an EVA sheet | seat for the sealing film for solar cells, the EVA sheet | seat (sealing film) manufactured by this invention is normally interposed between the surface side transparent protection member and the back surface side protection member. Then, the cells for solar cells are sealed by crosslinking and integrated to produce a solar cell. In order to sufficiently seal the solar cell, the front side transparent protective member, the front side sealing film, the solar cell, the back side sealing film and the back side protective member are laminated in that order, After pre-pressing under reduced pressure and degassing the air remaining in each layer, the sealing film may be crosslinked and cured by heating and pressurization.

  Here, the side of the solar cell irradiated with light (light receiving surface side) is referred to as “front surface side”, and the side opposite to the light receiving surface of the solar battery cell is referred to as “back surface side”.

  The surface-side transparent protective member used for solar cells is usually preferably a glass substrate such as silicate glass. As for the thickness of a glass substrate, 0.1-10 mm is common, and 0.3-5 mm is preferable. The glass substrate may generally be chemically or thermally strengthened. The back side protective member is a plastic film such as polyethylene terephthalate (PET). In consideration of heat resistance and moist heat resistance, a fluorinated polyethylene film, particularly a fluorinated polyethylene film / Al / fluorinated polyethylene film is used in this order. A film laminated with is preferable.

For example, the heating and pressing may be performed by using a vacuum laminator to heat the laminated body at a temperature of 135 to 180 ° C., further 140 to 180 ° C., particularly 155 to 180 ° C., a degassing time of 0.1 to 5 minutes, and a press pressure of 0.1 to 0.1 minutes. What is necessary is just to heat-press in 1.5 kg / cm < ² > and press time for 5 to 15 minutes. At the time of this heating and pressurizing, the EVA contained in the front side sealing film and the rear side sealing film is cross-linked, whereby the front side transparent protective member, the rear side, through the front side sealing film and the rear side sealing film. The solar cell can be sealed by integrating the transparent member and the solar cell.

  Hereinafter, the present invention will be described with reference to examples.

  EVA sheets having the thicknesses shown in Table 1 were prepared from the resin compositions having the following composition by using a calendar molding machine shown in FIG. At this time, the resin composition on the conveyor belt 24 shown in FIG. 1 was heated to each temperature shown in Table 1 to adjust the temperature. The temperature adjustment is carried out by conveying the resin composition heated and kneaded (kneading temperature: 90 ° C.) with the kneading roll 23 shown in FIG. 1 to the conveyor belt 24, supplying it to the calender roll 25, returning to the kneading roll 23, and again the conveyor belt. 24 was carried out by changing the belt temperature of the conveyor belt 24 to the temperature shown in Table 1 by carrying out a cycle of conveying the belt 24 for 1 hour.

  The temperature of the resin composition and the belt temperature of the conveyor belt 24 were measured with an infrared non-contact thermometer. Each calender roll was adjusted to a speed of 6 to 10 m / min and a temperature of 85 to 90 ° C.

(Formulation of EVA resin composition)
EVA 100 parts by mass (vinyl acetate content: 24% by mass, MFR: 2.5 g / 10 min)
Crosslinking agent (t-butylperoxy 2-hexyl carbonate) 2.5 parts by mass Crosslinking aid (triallyl isocyanurate) 2.0 parts by mass Silane coupling agent (γ-methacryloxypropyltrimethoxysilane) 0 .5 parts by mass

<Evaluation method>
The obtained EVA sheet was visually observed for the presence of bubbles and its length (L). The bubble length L indicates the length of the bubble extending elliptically by rolling during calendar molding, and its unit is mm.

  Further, the EVA sheet was sandwiched between two glasses (3.0 mm), and the presence or absence of bubbles was visually confirmed on the EVA sheet after being laminated at 135 ° C. with a vacuum laminator. The results are shown in Table 1.

<Evaluation results>
As shown in Table 1, when the temperature of the EVA resin composition is 70 to 90 ° C, the number of bubbles may be smaller than those of Comparative Examples 1 to 3 that are 50 ° C and 60 ° C, respectively. Admitted. In particular, in Examples 2 and 3 at 80 ° C. and 90 ° C., no bubbles were observed.

5 Intermediate Films 7A and 7B for Laminated Glass Transparent Substrate 11 Front Side Transparent Protection Member 12 Back Side Protection Member 13A Solar Cell Sealing Film (Front Side)
13B Solar cell sealing film (back side)
14 Solar Cell 15 Connection Tab 21 Kneading Machine 22 Conveyor Belt 23 Kneading Roll 24 Conveyor Belt 25A, 25B, 25C, 25D Calendar Roll 26 Take-off Roll 27 Embossing Roll 28 Cooling Roll 29 Winding Machine 30 EVA Sheet 31 Bank

Claims (9)

A method for producing an ethylene-vinyl acetate copolymer sheet comprising a step of kneading a resin composition containing an ethylene-vinyl acetate copolymer and rolling with a calender roll,
The ethylene-vinyl acetate copolymer sheet has a thickness of 0.7 to 2.0 mm; and
The manufacturing method of the ethylene-vinyl acetate copolymer sheet | seat characterized by adjusting the temperature of the said resin composition supplied to the said calender roll to 70-90 degreeC. Kneading with a kneading roll,
The temperature adjustment is performed by heating in a transport unit that transports the kneaded resin composition disposed between the kneading roll and the calender roll to the calender roll. 2. The production method according to 1.   The manufacturing method according to claim 2, wherein the heating is performed by irradiating the resin composition with heat rays.   The manufacturing method according to claim 2 or 3, wherein a conveyor belt is used as the conveying means, and the temperature adjustment is performed by setting the belt temperature of the conveyor belt to 40 to 70 ° C.   The thickness of the said ethylene-vinyl acetate copolymer sheet is 0.7-1.0 mm, The manufacturing method in any one of Claims 1-4 characterized by the above-mentioned.   6. The melt flow rate (measured at 190 ° C. under a load of 21.18 N according to JIS K7210) of the ethylene-vinyl acetate copolymer is 35 g / 10 min or less. The production method according to item.   The said resin composition contains a crosslinking agent, The manufacturing method of any one of Claims 1-6 characterized by the above-mentioned.   The manufacturing method according to claim 1, wherein the ethylene-vinyl acetate copolymer sheet is a solar cell sealing film or a laminated glass interlayer film.   The ethylene-vinyl acetate copolymer sheet manufactured by the manufacturing method of any one of Claims 1-7.

Images