JP2014028469A - Sheet molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for alleviating inconvenience of dimensional variations of a molded sheet due to post-molding heating.SOLUTION: A sheet molding method includes a step of melt-extruding a thermoplastic resin in a sheet shape from a die 10 of an extrusion molder, and then cooling and solidifying the same by passage between a pair of cooling rolls 30. An average strain rate dε/dt[sec] calculated by (Formula) dε/dt=(V1/Z)ln(V1/V0) and a frequency ω[sec], which is a reciprocal of a relaxation time of the thermoplastic resin calculated by using a storage modulus (G') and a loss modulus (G") of the thermoplastic resin, satisfy a relation of dε/dt<ωat a temperature of a resin sheet 30 at a center between the die 10 and the cooling rolls 30. Furthermore, V0 is a speed of the thermoplastic resin extruded from the extrusion molder [mm sec]; V1 is a speed of collecting the sheet-shaped thermoplastic resin [mm sec]; and Z is an air gap [mm] between the die and the cooling rolls.

Description

  The present invention relates to a sheet forming method.

  There is a sheet molding method in which a resin is melt-extruded into a sheet form from a die of an extruder, and then cooled and solidified by passing between a pair of cooling rolls. For example, it is disclosed in Patent Document 1.

  Patent Document 2 discloses a solar cell sealing sheet obtained by forming a film of an ethylene-vinyl acetate copolymer resin (EVA).

JP 2011-224987 A Japanese Patent No. 3473605

  By the way, in recent years, the need for natural energy has increased, and solar power generation has attracted attention as clean energy.

  The solar cell module includes a power generation element that converts sunlight into electricity and a sealing sheet that seals and protects the power generation element. As the sheet for sealing, a sheet obtained by extrusion molding or calender molding of a thermoplastic resin is generally used. In the case of extrusion molding, the molten resin extruded into a sheet form from the die of the extruder is cooled with a processing roll and embossed as necessary, and a long sheet roll is obtained by winding it. Thereafter, the sheet is cut into a predetermined shape according to the shape of the power generation element. And the cut | disconnected sheet | seat is installed in the both surfaces or single side | surface of an electric power generation element, Then, these are heated and adhere | attached and integrated (sealing), and a solar cell module is obtained.

  Here, according to the study by the present inventors, the sheet shrinks due to heating when the power generating element is sealed with the sheet by heating and bonding, and becomes smaller than the plane area of the power generating element, for example. It turned out that it may become unable to seal enough. That is, the sheet cut into a predetermined shape may be shrunk by a subsequent heating to change its shape and fail to perform a predetermined function.

  In addition to solar cell sealing sheets, the sheet is used for cutting a sheet into a predetermined shape and used for other applications having a step of heating the sheet after cutting into a predetermined shape. However, the same disadvantage can occur.

  It is an object of the present invention to provide a technique for reducing the inconvenience that a molded sheet changes in dimensions due to subsequent heating.

According to the present invention,
A thermoplastic resin is melt-extruded in a sheet form from a die of an extruder, and then cooled and solidified by passing between a pair of cooling rolls;
Average strain rate dε / dt [sec ⁻¹ ] obtained by the following (formula),
The frequency ω _d [sec ⁻¹ ], which is the reciprocal of the relaxation time of the thermoplastic resin, determined using the storage elastic modulus (G ′) and loss elastic modulus (G ″) of the thermoplastic resin,
In average resin temperature is the temperature of the sheet of the thermoplastic resin in the middle of the cooling roll and the die, sheet forming method satisfies the relationship dε / dt <ω _d is provided.

(Expression) dε / dt = (V1 / Z) ln (V1 / V0)
Incidentally, V0 is the velocity [mm · ^{sec -1]} of the thermoplastic resin is extruded from the extruder, V1 is the speed of taking up the sheet of the thermoplastic resin [mm · ^{sec -1],} Z is an air gap [mm] between the outlet of the die through which the thermoplastic resin is extruded and the cooling roll.

  According to the present invention, it is possible to reduce the inconvenience that the molded sheet undergoes dimensional changes due to subsequent heating.

It is a conceptual diagram for demonstrating one process of the sheet forming method of this embodiment. It is a figure which shows the frequency dependence of the storage elastic modulus and loss elastic modulus of each of polyolefin-type resin (PO) and ethylene-vinyl acetate copolymer resin (EVA).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

<First Embodiment>
The inventors of the present invention have the inconvenience that the dimension of the formed sheet is changed by subsequent heating, because the orientation and stress generated in the sheet when the molten resin is extruded to form the sheet remain in the sheet. It was thought to be caused by cooling and solidifying.

  Therefore, the present inventors sufficiently increase the distance (air gap) from the die exit to the cooling roll, or sufficiently slow the sheet moving speed from the die exit to the cooling roll, We studied a technique to sufficiently relax the orientation and stress before the sheet extruded from the die cooled and solidified. According to such a technique, the sheet can be cooled and solidified after sufficiently relaxing the orientation and stress. That is, it is possible to eliminate the inconvenience that the orientation and stress remain on the sheet, and to eliminate the inconvenience that the formed sheet undergoes dimensional change by subsequent heating.

  However, if the air gap is made too large, or if the moving speed of the seat is made too slow, problems such as the line speed becoming too slow and the installation space for the equipment becoming too large may occur.

  Accordingly, the present inventors have invented a technique that can sufficiently remove the orientation and stress without unnecessarily increasing the air gap and unnecessarily slowing down the moving speed of the sheet. This will be described below.

  The sheet forming method of the present embodiment includes a forming step in which a thermoplastic resin is melt-extruded into a sheet form from a die of an extruder and then cooled and solidified by passing between a pair of cooling rolls. FIG. 1 shows a conceptual diagram of the molding process.

  As shown in FIG. 1, the resin sheet 30 extruded in a sheet form from the die 10 of the extruder is then cooled and solidified by passing between a pair of cooling rolls 20. In addition, you may emboss the sheet | seat surface by providing a recessed part and / or a convex part in the surface of the cooling roll 20. FIG. Since the processes before and after the molding process can be designed according to the prior art, description thereof is omitted here.

  In the sheet forming method of the present embodiment, there is no inconvenience that the line speed becomes too slow or the installation space of the equipment becomes too large, and the inconvenience that the formed sheet changes in dimensions due to subsequent heating. It includes a technology that can appropriately set the conditions in the molding process so as to reduce.

Specifically, the sheet forming method of the present embodiment includes an average strain rate dε / dt [sec ⁻¹ ] obtained by the following (formula), a storage elastic modulus (G ′) and a loss elastic modulus ( The frequency ω _d [sec ⁻¹ ], which is the reciprocal of the longest relaxation time (hereinafter referred to as relaxation time) of the thermoplastic resin obtained using G ″), is a sheet-like shape between the die 10 and the cooling roll 20. in average resin temperature is the temperature of the thermoplastic resin (resin sheet 30), to set these conditions so as to satisfy the relation of dε / dt <ω _d.

(Expression) dε / dt = (V1 / Z) ln (V1 / V0)
V0 is the velocity [mm · ^{sec -1]} of the thermoplastic resin is extruded from the extruder, V1 is the speed of taking up the sheet-shaped thermoplastic resin (resin sheet ^{30) [mm · sec -1]} , Z is an air gap [mm] between the outlet of the die 10 through which the thermoplastic resin is extruded and the cooling roll 20. V0 is obtained by dividing the volume velocity of the extruded thermoplastic resin by the lip cross-sectional area, and V1 is obtained as the rotational peripheral velocity of the roll 20, respectively.

In a range satisfying _{dε / dt <ω d, V1} , V0 without becomes too small, and, by setting them so as not to Z becomes too large, or the line speed too slow, and, Inconveniences such as excessive installation space for facilities can be reduced.

The resin temperature immediately after being extruded from the die 10 or less and, in the resin temperature above the temperature range immediately before sandwiched cooling roll 20, also controlled conditions so as to satisfy the relation of dε / dt <ω _d Good.

  The average resin temperature between the die 10 and the cooling roll 20, the resin temperature immediately after being extruded from the die 10, and the resin temperature immediately before being sandwiched between the cooling rolls 20 can be measured using, for example, an infrared radiation thermometer. it can.

Here, the frequency ω _d [sec ⁻¹ ] will be described. As described above, the frequency omega _d is the inverse of the relaxation time of the thermoplastic resin to be determined using the storage modulus of the thermoplastic resin (G ') and loss modulus (G ").

  This relaxation time can be estimated from the low-frequency behavior of the storage elastic modulus (G ′) and loss elastic modulus (G ″) of the thermoplastic resin obtained by melt viscoelasticity measurement. On the side, since G ′ shows a behavior with a slope of 2 and G ′ shows a behavior of a slope of 1, Gf is fitted to the data to find the frequency of the intersection of these approximate lines, and the reciprocal of this frequency is the relaxation time.

The melt viscoelasticity measurement is performed using a viscoelasticity measuring device (for example, a viscoelasticity testing machine (model ARES) manufactured by TA Instruments). Specifically, as a sample, a sheet having a thickness of 2 mm is obtained by pressing at 120 ° C., and then molded into a disk shape having a diameter of 25 mm × 2 mm, and measurement is performed under the following conditions. As data processing software, RSI Orchestrator VER. Use 6.6.3 (manufactured by TI Instruments Japan Co., Ltd.).
Geometry: Parallel plate Measurement temperature: 120 ° C (temperature above melting point)
Frequency: 0.01-100 rad / sec
Distortion rate: 1.0%

As described above, according to this embodiment, the melt viscoelasticity measurement is performed on the thermoplastic resin to be sheet-molded to calculate the frequency ω _d [sec ⁻¹ ], and then V 0 so as to satisfy dε / dt <ω _d. , V1 and Z can be set to form a sheet with sufficiently relaxed orientation and stress. As a result, it is possible to reduce the inconvenience that the formed sheet undergoes dimensional changes by subsequent heating. For this reason, it is possible to avoid inconveniences such as the sheet cut into a predetermined shape contracts by the subsequent heating and changes its shape, and the predetermined function cannot be performed.

Further, in the range satisfying _{dε / dt <ω d, V1} , V0 without becomes too small, and, by setting them so as not to Z becomes too large, the line speed is slowed unnecessarily And the inconvenience that the installation space of the equipment becomes unnecessarily large can be suppressed.

<Second Embodiment>
This embodiment is different from the first embodiment in that the sheet to be formed is limited to a solar cell sealing sheet. Other configurations are the same as those of the first embodiment. The sheet according to this embodiment includes a thermoplastic resin and at least one additive. This will be described below.

(Thermoplastic resin)
The kind of thermoplastic resin is not particularly limited, and can be, for example, a polyolefin resin or an ethylene-vinyl acetate copolymer resin. However, among these, polyolefin resins are preferable. Hereinafter, the reason will be described.

FIG. 2 shows the frequency dependence (logarithm-logarithmic plot) of viscoelasticity of the polyolefin resin (PO) and the ethylene-vinyl acetate copolymer resin (EVA) at 70 ° C. The storage modulus (G ′) and loss modulus (G ″) are plotted on the vertical axis, and the frequency is plotted on the horizontal axis. Relaxation time is measured in a region where the complex viscosity called the flow region is constant regardless of the frequency. Specifically, the intersection of each extrapolated line is obtained by using data in which G ′ indicates a slope 2 and G ″ indicates a slope 1. The frequency of the intersection is a frequency ω _d [sec ⁻¹ ], which is the inverse of the relaxation time.

From FIG. 2, ω _d [sec ⁻¹ ] is larger for PO than EVA. Therefore, than towards the PO is EVA, possible range increases of d? / Dt satisfying dε / dt <ω _d. As a result, the design range of V1, V0, and Z is wider in PO than in EVA.

(Polyolefin resin)
Although it does not specifically limit as polyolefin resin in this embodiment, For example, a low density ethylene resin, a medium density ethylene resin, an ultra low density ethylene resin, a propylene (co) polymer, 1-butene (co) heavy 4-methylpentene-1 (co) polymer, ethylene / α-olefin copolymer, ethylene / cyclic olefin copolymer, ethylene / α-olefin / cyclic olefin copolymer, ethylene / α-olefin / non Examples thereof include conjugated polyene copolymers, ethylene / α-olefin / conjugated polyene copolymers, ethylene / aromatic vinyl copolymers, ethylene / α-olefin / aromatic vinyl copolymers, and the like. These polyolefin resins may be used alone or in combination of two or more.

  Among these, an ethylene / α-olefin copolymer composed of ethylene and an α-olefin having 3 to 20 carbon atoms is required for transparency, adhesiveness, flexibility, heat resistance, and appearance as a solar cell sealing sheet. It is particularly preferable because of its excellent balance of various characteristics such as crosslinking characteristics, electrical characteristics and extrusion moldability.

  The polyolefin resin in the present embodiment preferably has a melt flow rate (MFR) of 10 to 50 g / 10 minutes measured at 190 ° C. and a load of 2.16 kg in accordance with ASTM D1238. More preferably, it is 27 g / 10 minutes. The MFR of the polyolefin resin can be adjusted by adjusting the polymerization temperature, the polymerization pressure, the molar ratio of the ethylene monomer concentration and the hydrogen concentration in the polymerization system, and the like.

  When the MFR is 10 g / 10 min or more, the fluidity of the solar cell sealing sheet is improved, and the productivity at the time of sheet extrusion molding can be improved. Moreover, since the scorch property of the sheet | seat for solar cell sealing falls, gelatinization can be suppressed. For this reason, since the torque of an extrusion molding machine falls, sheet molding can be made easy. Moreover, since the generation | occurrence | production of a gel thing can be suppressed in an extruder after a sheet | seat is obtained, generation | occurrence | production of the unevenness | corrugation in the surface of a sheet | seat can be suppressed, and the fall of an external appearance can be suppressed.

  In addition, if there is a gel material inside the sheet, cracks will occur around the gel material when voltage is applied, and the dielectric breakdown voltage will decrease, but by reducing the MFR to 10 g / 10 min or more, the dielectric breakdown voltage will decrease. Can be suppressed. Further, if there is a gel material inside the sheet, moisture permeation easily occurs at the gel material interface. However, by reducing the MFR to 10 g / 10 min or more, a decrease in moisture permeability can be suppressed.

  Moreover, when unevenness | corrugation generate | occur | produces on the sheet | seat surface, adhesiveness with glass, a cell, an electrode, and a back sheet will deteriorate at the time of the lamination process of a solar cell module, and adhesion | attachment becomes inadequate, but MFR shall be 50 g / 10min or less. Thereby, since molecular weight becomes large, adhesion to roll surfaces, such as a chill roll, can be suppressed. Therefore, peeling is unnecessary and it can be formed into a sheet having a uniform thickness. Furthermore, since it becomes a resin composition having “stiffness”, a thick sheet of 0.3 mm or more can be easily formed. Moreover, since the crosslinking characteristic (especially crosslinking rate) at the time of laminate molding of the solar cell module is improved, it can be sufficiently crosslinked to suppress a decrease in heat resistance. When the MFR is 27 g / 10 min or less, neck-in at the time of sheet molding can be suppressed and a wide sheet can be molded, and the crosslinking characteristics and heat resistance are further improved. A sheet can be obtained.

The polyolefin resin in the present embodiment preferably has a density measured in accordance with ASTM D1505 in the range of 0.865 to 0.884 g / cm ³ . The density of polyolefin resin can be adjusted with the content rate of an ethylene unit. That is, when the content ratio of the ethylene unit is increased, the crystallinity is increased and a polyolefin resin having a high density can be obtained. On the other hand, when the content ratio of the ethylene unit is lowered, the crystallinity is lowered and a polyolefin resin having a low density can be obtained.

When the density of the polyolefin resin is 0.884 g / cm ³ or less, the crystallinity is lowered and the transparency can be increased. Furthermore, extrusion molding at low temperature becomes easy, and for example, extrusion molding can be performed at 130 ° C. or lower. For this reason, even if an organic peroxide is kneaded into the polyolefin resin, it prevents the cross-linking reaction from proceeding in the extruder, prevents the occurrence of gel-like foreign matters on the sheet, and suppresses the deterioration of the sheet appearance. You can also Moreover, since the flexibility is high, it is possible to prevent the occurrence of cracking of the cells, which are solar cell elements, and the chipping of the thin film electrode, when the solar cell module is laminated.

On the other hand, if the density of the polyolefin-based resin is 0.865 g / cm ³ or more, the crystallization speed of the polyolefin-based resin can be increased, so that the sheet extruded from the extruder is not sticky, and peeling with the first cooling roll is difficult. It becomes easy and the sheet | seat for solar cell sealing can be obtained easily. Further, since stickiness is less likely to occur in the sheet, the occurrence of blocking can be suppressed, and the sheet feedability can be improved. Moreover, since it can fully bridge | crosslink, a heat resistant fall can be suppressed.

(Ethylene / α-olefin copolymer)
The ethylene / α-olefin copolymer composed of ethylene and an α-olefin having 3 to 20 carbon atoms in the present embodiment is obtained, for example, by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms. . As the α-olefin, usually, an α-olefin having 3 to 20 carbon atoms can be used alone or in combination of two or more. Among these, α-olefins having 10 or less carbon atoms are preferable, and α-olefins having 3 to 8 carbon atoms are particularly preferable.

  Specific examples of such α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3,3-dimethyl-1-butene, 4-methyl-1- Examples include pentene, 1-octene, 1-decene, and 1-dodecene. Among these, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene are preferable because of their availability. The ethylene / α-olefin copolymer may be a random copolymer or a block copolymer, but a random copolymer is preferred from the viewpoint of flexibility.

  The ethylene / α-olefin copolymer used in the present invention preferably satisfies the following requirements a1) to a4):

a1) While the content rate of the structural unit derived from ethylene is 80-90 mol%, the content rate of the structural unit derived from a C3-C20 alpha olefin is 10-20 mol%.
a2) Based on ASTM D1238, the MFR measured under the conditions of 190 ° C. and 2.16 kg load is 10 to 50 g / 10 min.
a3) The density measured according to ASTM D1505 is 0.865 to 0.884 g / cm ³ .
a4) The Shore A hardness measured according to ASTM D2240 is 60 to 85.

  The proportion of structural units derived from an α-olefin having 3 to 20 carbon atoms (hereinafter also referred to as “α-olefin unit”) contained in the ethylene / α-olefin copolymer of the present embodiment is 10 to 20 mol%. preferable.

  When the proportion of α-olefin units is 10 mol% or more, a sheet having high transparency can be obtained. Further, extrusion molding at a low temperature can be easily performed, and for example, extrusion molding at 130 ° C. or lower is possible.

  For this reason, even when the organic peroxide is kneaded into the ethylene / α-olefin copolymer, it is possible to suppress the progress of the crosslinking reaction in the extruder, and a gel-like foreign matter is generated on the sheet. The appearance can be prevented from deteriorating. Moreover, since moderate softness | flexibility is acquired, generation | occurrence | production of the crack of a solar cell element, the crack of a thin film electrode, etc. can be prevented at the time of lamination molding of a solar cell module.

  When the content ratio of the α-olefin unit is 20 mol% or less, the crystallization speed of the ethylene / α-olefin copolymer becomes appropriate, so the sheet extruded from the extruder is not sticky, and the first cooling roll Peeling is easy and a solar cell sealing sheet can be obtained efficiently. Further, since no stickiness occurs in the sheet, blocking can be prevented, and the sheet feeding property is improved. In addition, a decrease in heat resistance can be prevented.

(Additive)
Although it does not specifically limit as an additive in this embodiment, It selects from the additive generally used for the sheet | seat for solar cell sealing, and uses it suitably. Examples of additives generally used in solar cell sealing sheets include organic peroxides, silane coupling agents, crosslinking aids, ultraviolet absorbers, heat stabilizers, and light stabilizers. .

(Organic peroxide)
The organic peroxide in the present embodiment is used as a radical initiator for graft modification of a silane coupling agent and a polyolefin resin, and further, during a crosslinking reaction during lamination molding of a polyolefin resin solar cell module. Used as a radical initiator. By graft-modifying a polyolefin-based resin with a silane coupling agent, a solar cell module having good adhesion to glass, a back sheet, a cell, and an electrode can be obtained. Furthermore, the solar cell module excellent in heat resistance and adhesiveness can be obtained by bridge | crosslinking polyolefin resin.

  The organic peroxide in the present embodiment only needs to be capable of graft-modifying a silane coupling agent on the polyolefin resin or cross-linking the polyolefin resin. In view of the balance between productivity in extrusion sheet molding and the crosslinking rate at the time of lamination of the solar cell module, the one minute half-life temperature of the organic peroxide is preferably 100 to 170 ° C.

  If the half-life temperature of the organic peroxide is 100 ° C. or higher, gel is unlikely to occur in the solar cell sealing sheet obtained from the resin composition at the time of extrusion sheet molding. And sheet forming can be facilitated. Moreover, since it can suppress that an unevenness | corrugation generate | occur | produces on the surface of a sheet | seat with the gel thing which generate | occur | produced in the extruder, the fall of an external appearance can be prevented. Moreover, since the generation | occurrence | production of the crack inside a sheet | seat can be prevented when a voltage is applied, the fall of a dielectric breakdown voltage can be prevented. Furthermore, it is possible to prevent a decrease in moisture permeability. Moreover, since it can suppress that an unevenness | corrugation generate | occur | produces on the sheet | seat surface, the adhesiveness with glass, a cell, an electrode, and a back sheet becomes favorable at the time of the lamination process of a solar cell module, and adhesiveness also improves. If the extrusion temperature of extrusion sheet molding is lowered to 90 ° C. or lower, molding is possible, but productivity is greatly reduced. When the one-minute half-life temperature of the organic peroxide is 170 ° C. or lower, it is possible to suppress a decrease in the crosslinking rate when the solar cell module is laminated, and thus it is possible to prevent a decrease in the productivity of the solar cell module. Moreover, the heat resistance of the sheet | seat for solar cell sealing and the fall of adhesiveness can also be prevented.

  Known organic peroxides can be used. Preferred specific examples of the organic peroxide having a 1 minute half-life temperature in the range of 100 to 170 ° C. include dilauroyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate Dibenzoyl peroxide, t-amylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxymaleic acid, 1 , 1-Di (t-amylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-amylperoxy) cyclohexane, t-amylperoxyisononanoate, t-amylperoxynormal Octoate, 1,1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di ( -Butylperoxy) cyclohexane, t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethylhexyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-amyl-peroxy Examples include benzoate, t-butyl peroxyacetate, t-butyl peroxyisononanoate, 2,2-di (t-butylperoxy) butane, t-butyl peroxybenzoate, and the like. Preferably, dilauroyl peroxide, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, t-butyl peroxyisononanoate, t-butyl peroxy-2-ethylhexyl carbonate, t-butyl peroxybenzoate, etc. Is mentioned. These organic peroxides may be used alone or in combination of two or more.

  Moreover, although the addition amount of an organic peroxide changes also with kinds of organic peroxide, it is preferable to use it in the ratio of 0.1-3 weight part with respect to 100 weight part of polyolefin resin, 0.2- It is particularly preferable to use it at a ratio of 3 parts by weight.

(Silane coupling agent)
The silane coupling agent in this embodiment is useful for improving the adhesion to a protective material, a solar cell element, and the like. For example, the compound which has a hydrolyzable group like an alkoxy group with an amino group or an epoxy group can be mentioned. Specifically, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (β-methoxyethoxysilane), γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane Etc. can be used. Preferred examples include γ-glycidoxypropylmethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and vinyltriethoxysilane, which have good adhesion. These silane coupling agents may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  Moreover, although the addition amount of a silane coupling agent changes with kinds of silane coupling agent, it is preferable to use it in the ratio of 0.1-4 weight part with respect to 100 weight part of polyolefin resin, It is particularly preferable to use it at a ratio of 3 parts by weight. Adhesiveness of the solar cell sealing sheet is excellent when it is at least the above lower limit. Moreover, the balance with the cost and performance of a solar cell sealing sheet is excellent in it being below the said upper limit.

(Crosslinking aid)
The crosslinking aid in this embodiment is effective for promoting the crosslinking reaction and increasing the degree of crosslinking of the polyolefin resin. For example, as the crosslinking aid, conventionally known ones generally used for olefin resins can be mentioned. Such a crosslinking aid is a compound having two or more double bonds in the molecule. Specifically, monoacrylates such as t-butyl acrylate, lauryl acrylate, cetyl acrylate, stearyl acrylate, 2-methoxyethyl acrylate, ethyl carbitol acrylate, methoxytripropylene glycol acrylate; t-butyl methacrylate, lauryl methacrylate, cetyl methacrylate Monomethacrylate such as stearyl methacrylate, methoxyethylene glycol methacrylate, methoxypolyethylene glycol methacrylate; 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate , Diethylene glycol diacrylate, tetraethylene glycol diacrylate Diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, etc .; 1,3-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate neo Dimethacrylates such as pentyl glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate; triacrylates such as trimethylolpropane triacrylate, tetramethylolmethane triacrylate, pentaerythritol triacrylate; Trimethylolpropane trimethacrylate Trimethacrylates such as methylolethane trimethacrylate; Tetraacrylates such as pentaerythritol tetraacrylate and tetramethylolmethane tetraacrylate; Divinyl aromatic compounds such as divinylbenzene and di-i-propenylbenzene; Triallyl cyanurate and triallyl isocyanurate A diallyl compound such as diallyl phthalate; a triallyl compound; an oxime such as p-quinonedioxime and pp′-dibenzoylquinonedioxime; and a maleimide such as phenylmaleimide.

  Among these crosslinking aids, more preferred are triacrylates such as diacrylate, dimethacrylate, divinyl aromatic compound, trimethylolpropane triacrylate, tetramethylolmethane triacrylate, pentaerythritol triacrylate; trimethylolpropane trimethacrylate , Trimethacrylates such as trimethylolethane trimethacrylate; tetraacrylates such as pentaerythritol tetraacrylate and tetramethylolmethane tetraacrylate; cyanurates such as triallyl cyanurate and triallyl isocyanurate; diallyl compounds such as diallyl phthalate; triallyl compound: p -Oximes such as quinonedioxime and pp'-dibenzoylquinonedioxime: phenylmaleimi And maleimides. Further, among these, triallyl isocyanurate is particularly preferable, and the balance between the generation of bubbles and the cross-linking property of the solar cell sealing sheet after lamination is most excellent. These crosslinking aids may be used alone or in combination of two or more.

  Although the addition amount of the crosslinking aid varies depending on the kind of the crosslinking aid, it is preferably used at a ratio of 0.05 to 5 parts by weight with respect to 100 parts by weight of the polyolefin resin. When the addition amount of the crosslinking aid is within the above range, an appropriate crosslinking structure can be obtained, and heat resistance, mechanical properties, and adhesiveness can be improved.

(UV absorber)
Specific examples of the ultraviolet absorber in the present embodiment include 2-hydroxy-4-normal-octyloxybenzophenone, 2-hydroxy-4methoxybenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, 2-hydroxy- Benzophenones such as 4-methoxy-4-carboxybenzophenone and 2-hydroxy-4-N-octoxybenzophenone; 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, 2- (2 Benzotrializoles such as -hydroxy-5-methylphenyl) benzotriazole; salicylic acid esters such as phenylsulcylate and p-octylphenylsulcylate are used. These ultraviolet absorbers may be used alone or in a combination of two or more.

  Although the addition amount of a ultraviolet absorber changes also with kinds of ultraviolet absorber, it is preferable to use it in the ratio of 0.005-5 weight part with respect to 100 weight part of polyolefin resin. When the addition amount of the ultraviolet absorber is within the above range, the effect of improving the weather resistance stability is sufficiently secured, and the transparency of the solar cell sealing sheet and the glass, back sheet, cell, electrode, aluminum and This is preferable because it can prevent a decrease in adhesiveness.

(Light stabilizer)
Examples of the light stabilizer in the present embodiment include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, poly [{6- (1,1,3,3-tetramethylbutyl) amino- 1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4- Hindered amine type and hindered piperidine type compounds such as piperidyl) imino}] are preferably used. These light stabilizers may be used alone or in a combination of two or more.

  Although the addition amount of a light stabilizer changes also with kinds of light stabilizer, it is preferable to use it in the ratio of 0.005-5 weight part with respect to 100 weight part of polyolefin resin. When the addition amount of the light stabilizer is in the above range, the effect of improving the weather resistance stability is sufficiently ensured, and the transparency of the solar cell sealing sheet and the glass, back sheet, cell, electrode, aluminum and This is preferable because it can prevent a decrease in adhesiveness.

(Heat resistance stabilizer)
Specifically, as the heat stabilizer in this embodiment, tris (2,4-di-tert-butylphenyl) phosphite, bis [2,4-bis (1,1-dimethylethyl) -6-methyl Phenyl] ethyl ester phosphorous acid, tetrakis (2,4-di-tert-butylphenyl) [1,1-biphenyl] -4,4′-diylbisphosphonite, and bis (2,4-di-tert) Phosphite heat stabilizers such as -butylphenyl) pentaerythritol diphosphite; lactone systems such as the reaction product of 3-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene 3,3 ′, 3 ″, 5,5 ′, 5 ″ -hexa-tert-butyl-a, a ′, a ″-(methylene-2,4,6-triyl) tri-p-cresol 1 , 3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxyphenyl) benzylbenzene, pentaerythritol tetrakis [3- (3,5-di-tert-butyl- 4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, thiodiethylenebis [3- (3,5-di-tert-butyl-4-hydroxy) Hindered phenol heat stabilizers such as phenyl) propionate], sulfur heat stabilizers, amine heat stabilizers, etc. Among these, phosphite heat stabilizers and hindered phenol heat stabilizers can be mentioned. These heat stabilizers may be used alone or in combination of two or more. It can have.

  Although the addition amount of a heat stabilizer changes with kinds of heat stabilizer, it is preferable to use it in the ratio of 0.005-5 weight part with respect to 100 weight part of polyolefin resin. When the addition amount of the heat stabilizer is in the above range, the effect of improving the resistance to high temperature and high humidity, heat cycle resistance and heat stability is sufficiently secured, and the solar cell sealing sheet is transparent. And deterioration of adhesiveness with glass, backsheet, cell, electrode and aluminum can be prevented.

(Other additives)
Various additives other than the additives described above can be appropriately contained in the additive of the present embodiment as long as the object of the present invention is not impaired. For example, various resins other than polyolefin resins, various rubbers, plasticizers, fillers, pigments, dyes, antioxidants, antistatic agents, antibacterial agents, antifungal agents, flame retardants, crosslinking aids, light diffusing agents, discoloration One or more additives selected from an inhibitor, a dispersant and the like can be appropriately added.

(Pellets mainly composed of polyolefin resin)
The method for producing pellets mainly composed of the polyolefin resin in the present embodiment is not particularly limited. For example, the polyolefin resin is melt-kneaded and extruded into a strand shape or a sheet shape by a single screw or twin screw extruder, Examples thereof include a method obtained by cutting into pellets to obtain a predetermined particle size using a pelletizer. In addition, you may make the pellet contain the additive mentioned above suitably in the range which does not impair the objective of this invention.

  Moreover, it is preferable that the average particle diameter of a pellet is the range of 0.2-10 mm. When the average particle size of the pellets is within the above range, the balance between the agitation of the pellets mainly composed of a polyolefin-based resin, which will be described later, and the impregnation time of the additives in the pellets is excellent.

(Method for producing solar cell sealing sheet)
It continues and demonstrates an example of the manufacturing method of the sheet | seat for solar cell sealing in this embodiment. In addition, the sheet | seat for solar cell sealing of this embodiment can also be manufactured with another manufacturing method.

  The manufacturing method of the sheet | seat for solar cell sealing in this embodiment is a process which produces an additive containing pellet by impregnating the additive A to the pellet which has polyolefin resin as a main component, and the said additive containing pellet. A step of extruding into a sheet while being supplied to an extruder and melt-kneaded in a cylinder.

(Process of adjusting additive A)
The property of the additive A to be impregnated in advance in the pellet is preferably a liquid from the viewpoint of excellent impregnation into the pellet.

  The additive A is preferably prepared in advance by dissolving or dispersing at least one solid solid additive in the liquid additive. By impregnating or dispersing the solid additive in the liquid additive, the impregnation property of the solid additive into the pellet can be improved. At this time, in order to improve the solubility or dispersibility of the solid additive, a diluting solvent may be appropriately added.

  The method for dissolving or dispersing the solid additive is not particularly limited. For example, the liquid additive is placed in a stirring mixer such as a Henschel mixer, a tumbler mixer, a super mixer, or a rotary mixer, and the solid additive is added to the mixer. By adding and stirring and mixing, a solution containing the additive can be prepared.

  The temperature for stirring and mixing is not particularly limited, but may be room temperature or may be heated to about 30 to 120 ° C. in order to increase the stirring efficiency. Since it can improve the melt | dissolution or dispersion | distribution rate of a solid additive as it is more than the said lower limit, productivity of the sheet | seat for solar cell sealing can be improved. Moreover, deterioration of an additive can be suppressed as it is below the said upper limit.

  The time for stirring and mixing is not particularly limited, but it is preferable to carry out until the solid additive is uniformly dissolved or dispersed visually.

  Here, the liquid additive in the present embodiment refers to an additive that is liquid at room temperature. Although it does not specifically limit as a liquid additive in this embodiment, An organic peroxide, a silane coupling agent, and a crosslinking adjuvant correspond mainly in the additive mentioned above.

  Moreover, the solid additive in this embodiment means an additive that is solid at room temperature. Although it does not specifically limit as a solid additive in this embodiment, Among an additive mentioned above, a ultraviolet absorber, a heat-resistant stabilizer, and a light stabilizer correspond mainly.

(Process for producing additive-containing pellets)
Next, a process for producing an additive-containing pellet by impregnating additive A with a pellet mainly composed of a polyolefin-based resin will be described.

  First, pellets mainly composed of a polyolefin-based resin and the prepared additive A are supplied to a stirring mixer such as a Henschel mixer, a tumbler mixer, a super mixer, or a rotary mixer.

  Next, the agitation mixer is stirred to bring the pellet mainly composed of polyolefin resin into contact with the additive A, and the additive A is impregnated into the pellet to produce an additive-containing pellet. In addition, it is preferable to supply the whole amount of pellets before rotating the stirring mixer. On the other hand, the total amount of the additive A may be supplied before rotating the stirring mixer, or may be supplied separately. In view of being able to uniformly impregnate with pellets, it is preferable to divide and feed the mixture into a stirring mixer.

  The motor power value of the stirring mixer at the time of stirring and mixing and the motor integrated power value of the stirring mixer at the time of stirring and mixing are design matters that can be determined according to the impregnation rate and the processing amount of the additive.

  The temperature of the pellet when the additive A is impregnated into the pellet mainly composed of polyolefin resin is not particularly limited, and may be room temperature or may be heated to about 30 to 50 ° C. in order to increase the impregnation rate. Absent. Since the impregnation rate to the pellet of the solution containing an additive can be improved as it is more than the said lower limit, productivity of the sheet | seat for solar cell sealing can be improved. Moreover, deterioration of an additive can be suppressed more as it is below the said upper limit. Further, it is possible to further suppress the fusion between the pellets and the fusion of the pellets to the stirring mixer. In addition, the temperature of a pellet means the surface temperature of a pellet.

  The time for impregnating additive A into pellets mainly composed of polyolefin resin is not particularly limited because it varies depending on the amount of treatment, but is preferably 0.2 to 3 hours, more preferably 0.3 to 2 hours. Additive A can be sufficiently impregnated to the inside of the pellet when the amount is not less than the above lower limit. When the amount is not more than the above upper limit value, the deactivation of the additive can be further suppressed. Whether the pellets have been impregnated with the additive A can be confirmed by the motor power value of the stirring mixer. When the impregnation is completed, the moistness of the pellet disappears, and the power value of the motor increases rapidly. By confirming the motor power value, it is possible to confirm whether or not the impregnation of the additive is completed even with a resin having a low impregnation rate of the additive A such as a polyolefin resin.

  According to the method for producing a solar cell sealing sheet in the present embodiment, the pellet A mainly containing a polyolefin resin is impregnated with the additive A in advance, thereby suppressing the deterioration of the additive A and inside the pellet. Additive A can be uniformly distributed. Therefore, a solar cell sealing sheet in which the additive A is uniformly dispersed in the sheet can be stably obtained.

(Process to extrude into sheet)
Next, a process of extruding the additive-containing pellets into a sheet while supplying the pellets to an extruder and melt-kneading them in a cylinder will be described.

  Examples of the extruder in the present embodiment include various known biaxial extruders and single screw extruders. The extrusion molding machine has a hopper as a raw material supply port at the most upstream part and a die such as a T die or a ring die at the most downstream end part. A screw is arranged in the cylinder, and the pellets thrown into the cylinder are heated and melted by a heater arranged outside the cylinder, sent downstream by a rotating screw, and extruded from a T-die or the like into a sheet shape. . As the extruder, a twin screw extruder is preferable because of excellent kneading performance.

  The additive-containing pellets are supplied from a hopper into an extruder, melt-kneaded and extruded from a die such as a T-die attached to the tip of the extruder to obtain a sheet for sealing a solar cell.

  The extrusion temperature is not particularly limited, but it is preferable to melt and knead the mixture at a temperature lower than the one-hour half-life temperature of the organic peroxide to be used and to extrude it into a sheet form. By doing so, deactivation of the organic peroxide can be suppressed.

  Specifically, the extrusion temperature is 100 to 130 ° C. By making extrusion temperature more than the said lower limit, productivity of the sheet | seat for solar cell sealing can be improved. Moreover, deterioration of an additive can be suppressed by making extrusion temperature below the said upper limit. Further, the gelation of the resin can be suppressed.

And the sheet | seat for solar cell sealing extruded from T die | dye etc. is cooled and solidified with uniform thickness with a cooling roll, and is wound up with a winder. V0 (speed at which the thermoplastic resin is extruded from the extruder [mm · sec ⁻¹ ]), V1 (speed at which the sheet-shaped thermoplastic resin is taken [mm · sec ⁻¹ ]), Z (between the die and the cooling roll) air gap [mm] in) is set to satisfy the dε / dt <ω _d. In a range satisfying _{dε / dt <ω d, V1} , V0 Gayori large and so Z is smaller value, it is possible to set these.

(Step of further adding additive B into the cylinder)
In the process of extruding into a sheet in the present embodiment, the same or different additive B as the additive A is further added into the cylinder between the raw material supply port and the screw tip using the liquid injection nozzle. May be. A well-known thing can be used as a liquid injection | pouring nozzle.

  By carrying out like this, the quantity of the additive A impregnated to a pellet previously can be reduced, the impregnation time of the said additive can be shortened, and the productivity of the sheet | seat for solar cell sealing can be improved. In particular, polyolefin resin has a slower impregnation rate of additives than polar copolymers such as ethylene / vinyl acetate copolymer, so additive A that impregnates the pellets in advance with pellets and liquid injection nozzle A method of adding the additive separately to the additive B to be added is effective. By carrying out like this, the productivity of the sheet | seat for solar cell sealing which has polyolefin resin as a main component can be improved more. In addition, it is preferable that the property of the additive B is a liquid from the viewpoint of excellent impregnation into the pellets as well as the property of the additive A.

  The amount of additive B added from the liquid injection nozzle is not particularly limited, but is preferably 0.01 parts by weight or more and 10 parts by weight or less when the total amount of additive A and additive B is 100 parts by weight. 1 to 5 parts by weight is more preferable. Within the above range, the uniformity of the additive within the sheet and the balance of sheet productivity are further improved.

  Moreover, it is preferable that the additive B injected into the cylinder does not substantially contain at least one of an organic peroxide and a silane coupling agent. Since these additives fall under the category of dangerous goods, special equipment for safety measures is required for the extruder when directly injected into the cylinder. Therefore, the production facility can be simplified by substantially not including the organic peroxide and the silane coupling agent in the additive B injected into the cylinder.

  On the other hand, in the present embodiment, it is preferable that the additive A includes at least one of an organic peroxide and a silane coupling agent as a liquid additive.

  Moreover, in this embodiment, it is preferable that the additive B contains a crosslinking aid. Among the liquid additives described above, the crosslinking aid has a slower impregnation rate into the polyolefin-based resin than other liquid additives. Therefore, the amount of the crosslinking aid in the additive A that is impregnated into the pellets in advance can be reduced by adding the crosslinking aid to the additive B injected into the cylinder. As a result, the impregnation time of the additive A into the pellet can be shortened, and the productivity of the solar cell sealing sheet containing a polyolefin resin as a main component can be further improved.

  When the total amount of the crosslinking aid used for the production of the solar cell sealing sheet of this embodiment is 100% by weight, the crosslinking aid contained in the additive B is 0.05% by weight or more and 5% by weight or less. Preferably, 0.5% by weight or more and 3% by weight or less is more preferable. Within the above range, the impregnation time of the additive A into the pellet can be further shortened, and the productivity of the solar cell sealing sheet containing a polyolefin resin as a main component can be further improved.

  In addition, the manufacturing method of the sheet | seat for solar cell sealing of this embodiment has as a main component the polyolefin resin whose weight change rate is 3 weight% or less when immersed in a liquid crosslinking adjuvant at 150 degreeC for 3 hours. This is particularly effective when the pellets to be used are used as raw materials. Since such a polyolefin resin has a particularly slow impregnation rate of the additive, the kneading of the polyolefin resin and the additive in the extruder is further insufficient, and the additive is easily segregated in the sheet. Therefore, when such a polyolefin resin is used, the method for producing a solar cell sealing sheet of this embodiment is particularly effective.

  The liquid crosslinking aid used when measuring the weight change rate of the polyolefin resin relative to the crosslinking aid is, for example, triallyl isocyanurate.

  Thus, in the manufacturing method of the sheet | seat for solar cell sealing in this embodiment, an additive passes the inside of an extrusion molding machine only once. Therefore, it can suppress that a various additive deactivates by the heating in an extrusion molding machine, or the frictional heat with a screw blade | wing, and can manufacture the sheet | seat for solar cell sealing excellent in quality stably.

  Moreover, in the manufacturing method of the sheet | seat for solar cell sealing in this embodiment, in order to improve deaeration property, after extruding in a sheet form, it is preferable to emboss the surface of a sheet | seat.

  Although it does not specifically limit as a method of embossing the surface of the sheet, a sheet extruded from a T-die, an embossing roll having an embossed pattern on the surface, and a rubber roll disposed opposite to the embossing roll, And a method of embossing the surface of the sheet while pressing the embossing roll against the molten sheet. The obtained sheet may be heated again to be melted and embossed.

  The thickness of the solar cell sealing sheet in this embodiment is not particularly limited, but is usually 0.01 to 2 mm, preferably 0.1 to 1.2 mm, and more preferably 0.3 to 0.9 mm. . When the thickness is within this range, breakage of glass, solar cell elements, thin film electrodes, etc. in the laminating step can be suppressed, and a high amount of photovoltaic power can be obtained by securing sufficient light transmittance. Furthermore, it is preferable because the solar cell module can be laminated at a low temperature.

  The roll-shaped solar cell sealing sheet obtained in the present embodiment is then cut according to the solar cell module size. And the cut | disconnected sheet | seat is installed in the both sides | surfaces or single side | surface of a photovoltaic cell (power generation element). Then, these laminated bodies are integrated by applying a pressure with a press pressure of 0.4 to 1 atm while heating at 140 to 200 ° C. for 5 to 30 minutes. In addition, a laminated body is a sheet | seat for surface side transparent protection members (example: glass plate), a 1st sheet | seat for solar cell sealing, a photovoltaic cell, a sheet | seat for 2nd solar cell sealing, and a back surface side, for example. A protective member (eg, a back sheet obtained by laminating various sheets) may be laminated in this order. Since the structure of the front surface side transparent protective member, the solar battery cell, and the back surface side protective member can be realized according to the prior art, description thereof is omitted here.

  According to the present embodiment, similarly to the first embodiment, it is possible to reduce the inconvenience that the formed sheet undergoes dimensional changes due to subsequent heating. For this reason, a sheet | seat shrink | contracts by the heating at the time of sealing a photovoltaic cell (power generation element) with the sheet | seat for solar cell sealing, for example, it becomes smaller than the plane area of a photovoltaic cell (power generation element), and a photovoltaic cell Inconveniences such as (power generation element) cannot be sufficiently sealed can be avoided.

Example 1
(Synthesis of ethylene / α-olefin copolymer)
To one supply port of a 50 L internal polymerization vessel equipped with a stirring blade, 8.0 mmol / hr of a toluene solution of methylaluminoxane as a cocatalyst and bis (1,3-dimethylcyclopentadienyl) zirconium as a main catalyst Supply dichlorinated hexane slurry at a rate of 0.025 mmol / hr and triisobutylaluminum hexane at a rate of 0.5 mmol / hr, so that the total amount of dehydrated and purified normal hexane used as the polymerization solvent and polymerization solvent is 20 L / hr. Was fed continuously with dehydrated and purified normal hexane. At the same time, ethylene is continuously supplied to another supply port at a rate of 3 kg / hr, 1-butene at 15 kg / hr, and hydrogen at a rate of 6 NL / hr, a polymerization temperature of 90 ° C., a total pressure of 3 MPaG, and a residence time of 1.0. Continuous solution polymerization was performed under conditions of time. The ethylene / α-olefin copolymer normal hexane / toluene mixed solution produced in the polymerization vessel is continuously discharged through a discharge port provided at the bottom of the polymerization vessel, and the ethylene / α-olefin copolymer solution is discharged. The jacket portion was led to a connecting pipe heated with 3 to 25 kg / cm ² steam so that the normal hexane / toluene mixed solution was 150 to 190 ° C. Immediately before reaching the connecting pipe, a supply port for injecting methanol, which is a catalyst deactivator, is attached, and methanol is injected at a rate of about 0.75 L / hr. The mixture was merged into a combined normal hexane / toluene mixed solution. The normal hexane / toluene mixed solution of the ethylene / α-olefin copolymer kept at about 190 ° C. in the connection pipe with steam jacket is a pressure provided at the end of the connection pipe so as to maintain about 4.3 MPaG. The liquid was continuously fed to the flash tank by adjusting the opening of the control valve. In the transfer to the flash tank, the solution temperature and the pressure adjustment valve opening are set so that the pressure in the flash tank is about 0.1 MPaG and the temperature of the vapor part in the flash tank is maintained at about 180 ° C. It was broken. Thereafter, the strand was cooled in a water tank through a single screw extruder having a die temperature set at 180 ° C., and the strand was cut with a pellet cutter to obtain an ethylene / α-olefin copolymer as pellets. The yield was 2.2 kg / hr.

(Sheet making process)
50 parts by weight of organic peroxide (2-ethylhexanoxycarbonyl-tert-butyl peroxide) and 50 silane coupling agent (vinyltriethoxysilane) in a first stirring tank having an internal volume of 50 L having a stirring blade Additive A, which was mixed with parts by weight and stirred at room temperature for 30 minutes, was sufficiently stirred and mixed.

  Next, the above-mentioned ethylene / α-olefin copolymer pellets are held in a 200 L inverted conical stirring tank having a spiral ribbon blade, and 1 part by weight of additive A is added to 100 parts by weight of the pellets. The mixture was stirred for 30 minutes under a 40 ° C. heating environment. As a result, the pellets of the ethylene / α-olefin copolymer impregnated with the additive A were obtained and dried to obtain impregnated pellets.

  Next, in a second stirring tank having an internal volume of 50 L having a stirring blade, 1 part by weight of an antioxidant (Irganox 1010) is blended with 99 parts by weight of a crosslinking aid (triallyl isocyanurate), and the temperature is 35 ° C. The mixture was stirred for 2 hours and sufficiently dissolved to obtain additive B.

  Next, the impregnated pellets were supplied to the raw material supply port of the twin screw extruder using a weight type feeder. Furthermore, the additive B was supplied to the liquid addition nozzle attached to the intermediate part between the raw material supply port and the screw tip using a plunger pump, and the additive was injected into the cylinder from the liquid addition nozzle. At this time, the addition amount was adjusted so that the liquid addition amount was 1 part by weight with respect to 100 parts by weight of the resin. A T-die was attached to the extruder, and the extruded molten sheet was cooled and solidified with a cooling roll and then wound up.

Thermoplastic resin: ethylene-α-olefin copolymer, mfr = 25 g / 10 min, d = 0.870 g / cm ³ , ω _{d at} 70 ° C. = 7.1 sec ⁻¹
-Average resin temperature between T-die and cooling roll: 70 ° C
Dε / dt = 0.032 sec ⁻¹ (extruder die exit speed V0 = 0.54 m / min, take-off speed V1 = 1.04 m / min, distance between die exit and take-up roll Z = 0.35 m)

  The average resin temperature between the T die and the cooling roll was obtained by measuring the resin temperature between the T die and the cooling roll using an infrared radiation thermometer.

(Cutting and heating)
The sheet formed as described above was cut into 10 cm × 10 cm. Then, it heated on 150 degreeC and the conditions for 15 minutes. The sheet size after heating was 9.8 cm × 9.8 cm. The shrinkage in the MD direction was 2%.

<Comparative Example 1>
(Sheet making process)
25 parts by weight of organic peroxide (2-ethylhexanoxycarbonyl-tert-butyl peroxide), 25 parts by weight of silane coupling agent (vinyltriethoxysilane) in an internal volume 50 L stirring tank having a stirring blade, 49 parts by weight of a crosslinking aid (triallyl isocyanurate) and 1 part by weight of an antioxidant (Irganox 1010) were blended and stirred at 35 ° C. for 2 hours to prepare a sufficiently dissolved and mixed additive C.

  Next, EVA pellets (VA 33%) were held in a 50 L inverted conical stirring vessel with a spiral ribbon blade, and 2 parts by weight of additive C was added to 100 parts by weight of the pellets. For 30 minutes. As a result, an EVA pellet in which the additive C was impregnated into an EVA pellet and dried was obtained.

  Next, the impregnated pellets were supplied to the raw material supply port of the twin screw extruder using a gravimetric feeder. A T-die was attached to the extruder, and the extruded molten sheet was cooled and solidified with a cooling roll and then wound up.

Thermoplastic resin: ethylene-vinyl acetate-olefin copolymer, mfr = 15 g / 10 min, d = 0.98 g / cm ³ , ω _{d at} 70 ° C. = 2.2 × 10 ⁻² sec ⁻¹
-Average resin temperature between T-die and cooling roll: 70 ° C
Dε / dt = 0.032 sec ⁻¹ (extruder die exit speed V0 = 0.54 m / min, take-off speed V1 = 1.04 m / min, distance between die exit and take-up roll Z = 0.35 m)

  The average resin temperature between the T die and the cooling roll was obtained by measuring the resin temperature between the T die and the cooling roll using an infrared radiation thermometer.

(Cutting and heating)
The sheet formed as described above was cut into 10 cm × 10 cm. Then, it heated on 150 degreeC and the conditions for 15 minutes. The sheet size after heating was 4.9 cm × 10.1 cm. The shrinkage in the MD direction was 51%.

Thus, sheets of Example 1 satisfying the relation of dε / dt <ω _d is contracted by heating is sufficiently small, d? / Dt <Comparative Example 1 not satisfying the relation of omega _d sheet, by heating It contracted greatly.

10 die 20 cooling roll 30 resin sheet

Claims (4)

A thermoplastic resin is melt-extruded in a sheet form from a die of an extruder, and then cooled and solidified by passing between a pair of cooling rolls;
Average strain rate dε / dt [sec ⁻¹ ] obtained by the following (formula),
The frequency ω _d [sec ⁻¹ ], which is the reciprocal of the relaxation time of the thermoplastic resin, determined using the storage elastic modulus (G ′) and loss elastic modulus (G ″) of the thermoplastic resin,
In average resin temperature is the temperature of the sheet of the thermoplastic resin in the middle of the cooling roll and the die, sheet forming method satisfies the relationship dε / dt <ω _d.
(Expression) dε / dt = (V1 / Z) ln (V1 / V0)
Incidentally, V0 is the velocity [mm · ^{sec -1]} of the thermoplastic resin is extruded from the extruder, V1 is the speed of taking up the sheet of the thermoplastic resin [mm · ^{sec -1],} Z is an air gap [mm] between the outlet of the die through which the thermoplastic resin is extruded and the cooling roll. The sheet forming method according to claim 1,
The sheet molding method, wherein the thermoplastic resin is a polyolefin resin. In the sheet forming method according to claim 1 or 2,
The sheet | seat shaping | molding method used for the use which has the process of heat-processing, after the shape | molded sheet | seat is cut | judged to predetermined shape. In the sheet forming method according to claim 3,
The use of the formed sheet is a sheet forming method which is a sheet for sealing a solar cell.

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