KR101220224B1 - Polyvinyl acetal film having improved reflectance and preparation method thereof - Google Patents

Abstract

PURPOSE: A polyvinylacetal film is provided to be used as a sealing film for a solar cell module by having excellent light resistance, penetration resistance, and reflectivity. CONSTITUTION: A polyvinylacetal film comprises a polyvinylacetal resin, and a titanium oxide which is heat-resistant coated and has a diameter of 0.4 micrometers or less. The reflectivity of the polyvinylacetal film to a wavelength of 350-1100 nm is 93% or more and the difference of a yellowness index according to EN 410 between before and after UV irradiation(ΔY.I.) is 2.0 or less. A manufacturing method of the polyvinylacetal film comprises: a step of manufacturing a raw material resin by mixing a plasticizer and the heat-resistant coated titanium oxide; and a step of melt-extruding the raw material resin at a temperature of 100-200 deg. C and cooling the extrudate to obtain a final film.

Description

Polyvinyl acetal film with excellent reflectivity and manufacturing method thereof {POLYVINYL ACETAL FILM HAVING IMPROVED REFLECTANCE AND PREPARATION METHOD THEREOF}

The present invention relates to a polyvinyl acetal film that can be used as an encapsulant in a solar module and a method for producing the same.

The solar cell constitutes the heart of a photovoltaic system that directly converts solar energy into electricity, and is manufactured using a single crystal, polycrystalline or amorphous silicon-based semiconductor. Solar cells are rarely used as they are, and generally, several to tens of solar cell elements are wired in series or in parallel, and variously packaged and united to protect the cells over a long period of time. The unit incorporated in this package is called a solar cell module.

Recently, solar cells have been attracting attention due to environmental problems and energy problems, and developments are being made. In general, a solar cell module has a structure in which two sheets of encapsulant surround a solar cell for a solar cell module between a glass substrate that is a front side transparent protective member and a backside protective film that is a back side protective member. Such a solar cell module is manufactured by laminating | stacking in order of a glass substrate, an encapsulating material sheet, a solar cell, an encapsulating material sheet, and a back protective film, heat-pressing, and carrying out an adhesive integration by crosslinking-hardening an encapsulating material sheet.

In general, the encapsulant sheet for a solar cell module uses a sheet made of a transparent soft resin containing a crosslinking agent, and an ethylene vinyl acetate (EVA) copolymer is mainly used as a main component of the resin. However, these EVA films are not suitable for use as thin film solar modules (particularly BIPV systems) in addition to power plant modules due to poor strength and penetration resistance. As a result, the film which improves the function using the polyvinyl acetal film as a sealing material of a solar module is currently developed.

WO 2009/035081 discloses an interlayer film for laminated glass prepared by dispersing titanium oxide particles having an average diameter of 0.4 to 2.0 µm in a polyvinyl acetal resin so as to be 2.0 to 7.0 x 10 ⁵ particles / cm 2. . However, when the polyvinyl acetal resin is used as the encapsulant of the solar module, there is a problem that the module efficiency is not higher than that of the EVA film. There is this.

Accordingly, there is a demand for the development of a new polyvinyl acetal film having excellent reflectance and improved yellowing resistance and impact resistance.

International Publication No. WO2009 / 035081

Accordingly, it is an object of the present invention to provide a polyvinyl acetal film excellent in penetration resistance, reflectance, and the like, even in various external environments.

According to the above object, the present invention comprises polyvinyl acetal resin and heat-resistant coated titanium oxide with a diameter of less than 0.4 ㎛, reflectance for wavelengths of 350 to 1100 nm is 93% or more, UV irradiation of the yellow index according to EN 410 The polyvinyl acetal film whose difference before and after (DELTA YI) is 2.0 or less is provided.

According to the above another object, the present invention comprises the steps of (a) preparing a raw material resin by mixing a polyvinyl acetal resin with a plasticizer and heat-resistant coated titanium oxide less than 0.4㎛ diameter; And (b) melt extruding and cooling the raw material resin to obtain a final film, the method for producing the polyvinyl acetal film .

The present invention also provides a solar module encapsulant film comprising a polyvinyl acetal film.

As described above, the polyvinyl acetal film of the present invention has improved light resistance and excellent light resistance and reflectance by a functional additive compared to a conventional EVA film, and thus can be used as an encapsulant film in a solar module to exhibit excellent performance. .

The film of the present invention is characterized in that the polyvinyl acetal resin comprises heat-resistant coated titanium oxide having a diameter of less than 0.4 m.

The polyvinyl acetal resin used in the present invention may be polyvinyl butyral resin, polyvinyl formal resin, glutaraldehyde-crosslinked polyvinyl butyral resin, or a blend resin thereof, among which polyvinyl butyral resin Most preferred.

Such polyvinyl acetal resin may contain 30 to 90% by weight, more preferably 50 to 75% by weight of the total weight of the film is good in impact resistance, mechanical properties, heat resistance when bonding with glass.

The film of the present invention contains triethylene glycol bis 2-ethylhexanoate (3G8), tetraethylene glycol diheptanoate (4G7), triethylene glycol bis 2-ethylbutyrate (3GH), triethylene glycol bis 2-heptanoate (3G7), dibutoxyethoxyethyl adipate (DBEA), dibutyl sebacate (DBS), bis 2-hexyl adipate (DHA), and mixtures thereof may be contained. Such a plasticizer may be contained in each resin layer at 8 to 68% by weight, more preferably 20 to 45% by weight based on the total weight of the film, and may be excellent in terms of heat resistance, mechanical properties, impact resistance, and water resistance of the film.

The heat-resistant coated titanium oxide is preferably alumina or alumina-silica coated titanium oxide, and the diameter of the particles is preferably less than 0.4 mu m. When the diameter is 0.4 μm or more, dispersion of the inorganic material in the film becomes difficult, so that aggregation between the inorganic materials occurs, the reflectance is not high, and there is a problem that the uniformity is inferior. More preferably, the diameter of the particles is 0.05 to 0.3 ㎛.

The heat-resistant coated titanium oxide is preferably 1 to 30% by weight, more preferably 3 to 20% by weight based on the weight of the film. Within the above range, there is an advantage of excellent reflectance and penetration resistance.

In addition, the film of the present invention, antioxidants, UV Stabilizer, UV Absorbent, Glass Adhesion Additives selected from modulators and mixtures thereof may be contained.

Specifically, as the antioxidant, Irganox, butylhydroxytoluene (BHT) and the like of Basf may be used; As the UV stabilizer, Tinuvin or the like of Basf may be used; Examples of UV absorbers include Chemisorb 12, Chemisorb 79, Chemisorb 74, Chemisorb 102, and Tinuvin from Basf. 328, Tinuvin 329, Tinuvin 326 and the like can be used; As the glass adhesion modifier, Mg, K, Na, epoxy-modified Si oil, or a mixture thereof may be used.

Such additives may be contained in an amount of 0.01 to 1.0% by weight, more preferably 0.2 to 0.5% by weight based on the weight of the film, in terms of thermal safety, light resistance, and glass bonding strength.

Polyvinyl acetal film of the present invention preferably has a total thickness of 0.2 to 2.0 mm, there is an advantage to improve the impact resistance and penetration resistance within the above range.

It is preferable that both of the surface roughness Rz of the film of this invention are 20 micrometers or more, for example, it may be 20-70 micrometers. When the surface roughness is in the above range, a blocking phenomenon may occur when the film is loaded during the process, and deairing may be more effectively performed during the glass bonding process.

Such polyvinyl acetal film of the present invention,

(a) preparing a raw material resin by mixing a polyvinyl acetal resin with an additive including a plasticizer and a heat-resistant coated titanium oxide having a diameter of less than 0.4 µm; And

(b) melt-extruding the raw material resin and cooling to obtain a final film.

In the above production method, polyvinyl acetal resin, plasticizer, additives, etc., which are the material components, may be mixed in each component and content range to have the composition of the film of the present invention as described above.

The melt extrusion temperature is preferably a temperature of 100 to 200 ℃, if it exceeds 200 ℃ thermal decomposition may occur as the thermal bond breaks the acetate bond of the lowest binding energy, the viscosity may be lowered by decomposition, Due to the volatilization of the plasticizer, workability may be degraded.

After the step (b) it may further include the step of the surface pattern treatment on both sides of the film so that both the surface roughness (Rz) of both sides to 20㎛ or more, specifically, the surface of the mat Rz 20㎛ or more It can be carried out through a process of heating and surface pressing using a roll, in which case blocking resistance and degassing resistance can be improved.

Polyvinyl acetal film of the present invention as described above, the polyvinyl acetal resin as a main component to improve the penetration resistance compared to conventional EVA film, and simultaneously improve the light resistance and reflectance by using titanium oxide having a diameter of less than 0.4㎛ coated heat-resistant Can be.

Preferably, the reflectance according to EN 410 of the film of the invention exhibits greater than 93% for wavelengths in the range from 350 to 1100 nm. Since the reflectance is more excellent when in the above range, there is an advantage that the solar efficiency increases when the solar module is applied.

In addition, when the yellow index (Y.I.) was measured based on ASTM E313 for the film of the present invention, the difference between the initial value and the value after UV irradiation (ΔY.I.) may be less than 2.0 under conditions of 400 to 1100 nm. Since it is possible to increase the visible light region transmittance within the above range, the solar efficiency is increased when the solar module is applied, and impact and mechanical properties, transparency, visibility, and quality are increased when bonding with glass.

In addition, the penetration height of the penetration resistance test of the polyvinyl acetal film laminated glass according to the KS L 2007 standard may have a penetration resistance of more than 4m. Within this range there are excellent advantages in terms of shock absorption, glass protection, and safety.

In addition, as evaluation of the pummel bonding force, the amount of glass remaining in the film after cooling the 2.1T glass-polyvinyl acetal film-2.1T glass laminate to -18 ° C and successively using a hammer is 30 to 80%. If it is less than 30%, the bonding strength between the glass and the film is poor, and if it is more than 90%, the bonding strength is too high and the film may be torn, which is undesirable.

In addition, after immersing the 2.1T glass-polyvinyl acetal film-2.1T glass laminate in water at 100 ° C. for 6 hours as an evaluation of the whitening distance, the whitening distance measured from the edge portion of the laminate may be less than 7 mm. Within the above range, it is excellent in water resistance to prevent oxidation of the solar module electrode and protects the module, which has the advantage of having long-term durability.

Accordingly, when the film of the present invention is used as an encapsulant film in the solar module, it is possible to increase the efficiency of the solar module.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are illustrative of the present invention, and the present invention is not limited to the following examples.

The components used in the following examples and comparative examples are as follows:

-Polyvinyl butyral (PVB) resin: 70 mol% butylation degree, number average molecular weight 140,000, Tg 72 ℃, GH, Xingwei China

-Ethylene vinyl acetate (EVA): VA 28%, 1626-EVA, Hanwha Petrochemical, Korea

-Triethylene glycol bis 2-ethylenehexanoate: purity of at least 97.0%, WVC3800, Celanese, Germany

-Chemisorb 12: Benzophenone series, Chemipro Chemicals, Japan

-Chemisorb 79: Benzotriazole series, Chemiprosseong Co., Japan

Irganox: hindered phenolic, Basf, Germany

Butylhydroxytoluene (BHT): Lanxess, Vulkanox, Germany

Mg, K, and Na: Mg acetate, K acetate, Na acetate, OCI Corporation, Korea

Alumina-silica coated titanium oxide particles 0.3 탆 in diameter: R105, Dupont, USA

Alumina coated 0.2 μm diameter titanium oxide particles: R104, Dupont, USA

-0.5㎛ titanium oxide particles: COTIOX KA-100, Cosmo Chemical, Korea

-Titanium oxide particles with diameter 2.0㎛: COTIOX KA-300, Cosmo Chemical, Korea

Example 1

Based on 100% by weight of the raw material resin, 59.69% by weight of polyvinyl butyral (PVB) resin, 30% by weight of triethylene glycol bis 2-ethylenehexanoate as a plasticizer, 0.2% by weight of Chemisorb 79 as a UV absorber, Irganox 0.1 as an antioxidant A raw material resin composition was prepared by adding% by weight, 0.01% by weight of Mg + K + Na as a glass adhesion modifier, and 10% by weight of alumina-silica coated diameter 0.3 μm titanium oxide.

The raw resin composition was melt extruded through a twin screw extruder equipped with one kneader at a melting temperature of 150 ° C., and cooled on a casting roll at 160 ° C. to obtain a film.

The film cooled by the casting roll was heat-pressed at a temperature of 100 ° C. in a matrol having a Rz 70 μm roughness to finally complete a film having a surface roughness Rz of 25 μm and a total thickness of 0.76 mm.

Example 2 and Comparative Examples 1 and 2

A polyvinyl acetal film was prepared in the same manner as in Example 1, except that a resin composition having a composition as shown in Table 1 was used as the raw material resin composition.

Test Example

The physical properties of the polyvinyl acetal films prepared in Examples and Comparative Examples were evaluated as follows, and the results are shown in Table 1 below.

* Reflectance

In accordance with EN 410 the reflectance of the polyvinyl acetal film for the wavelength of 350 to 1100 nm was measured. Specifically, a glass-polyvinyl acetal film-back sheet (PVDF / PET) laminated structure laminated by laminating at 150 ° C. for 15 minutes by heating and pressure to prepare a specimen, and using a Hunter Lab's measuring device, a reflection mode It measured on condition of.

* △ Y.I (Yellow index change) measurement

The yellowness index of the polyvinyl acetal film was evaluated according to EN 410. Specifically, the lamination structure of glass-polyvinyl acetal film-glass was laminated in a laminator at a temperature of 150 ° C. for 15 minutes by heating and pressing to prepare a specimen, and the initial value under the conditions of 400-1100 nm using Hunter Lab's measuring device. And the difference value (ΔYI) between the values after UV irradiation were calculated.

* Drop height

Based on KS L 2007, the penetration resistance of the glass by which the polyvinyl acetal film was laminated was evaluated. Specifically, the laminated structure of 2.1T glass-polyvinyl acetal film-2.1T glass of 300mm x 300mm was laminated in a laminator at 150 ° C. for 15 minutes by heating and pressing to prepare a specimen, and then, a steel ball of 2.26 kg was prepared. The height (MBH) through which the specimen penetrated was measured.

* Glass adhesion evaluation

Laminated structure of glass-polyvinyl acetal film-backsheet (PVDF / PET) was laminated by laminating in a laminator at 150 ℃ for 15 minutes by heating and pressing to make a specimen, and using a universal testing machine (UTM, QM100, Cumulsis) By pulling 180 degrees at a tensile rate of 50mm / min was measured the force taken when the film is removed from the glass.

* Fummel Bonding Force Evaluation

The adhesive force between the polyvinyl acetal film and the glass was evaluated through the evaluation of the pummel bonding force. Specifically, a laminated structure of 2.1T glass-polyvinyl acetal film-2.1T glass of 300 mm x 300 mm was laminated in a laminator at 150 ° C. for 15 minutes by heating and pressing to prepare a specimen, and the specimen was −18 ° C. After cooling and continuous with the same force with a hammer, the amount of glass remaining in the polyvinyl acetal film is measured, and the case where there is no glass remaining on the film is set to 0, and all the glass remains on the film. A value of 0 to 10 was assigned as 10.

(The numbers in parentheses in the table above represent the weight percentage of each component.)

As shown in Table 1, the polyvinyl acetal film of the embodiment according to the present invention exhibited excellent performance compared to the polyvinyl acetal film of the comparative example according to the prior art in reflectance, yellowing resistance, impact resistance and the like.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, It is to be understood that the invention may be practiced within the scope of the appended claims.

Claims (9)

Polyvinyl acetal resin and heat-resistant coated titanium oxide having a diameter of less than 0.4 μm,
The polyvinyl acetal film whose reflectance with respect to the wavelength of 350-1100 nm is 93% or more, and the difference value ((DELTA) YI) before and after UV irradiation of the yellow index according to EN 410 is 2.0 or less.
The method of claim 1,
The heat-resistant coated titanium oxide, alumina or alumina-silica coated titanium oxide, characterized in that contained in the polyvinyl acetal film in an amount of 1 to 30% by weight, polyvinyl acetal film.
The method of claim 1,
The polyvinyl acetal resin is a polyvinyl butyral (PVB) resin, characterized in that contained in an amount of 30 to 90% by weight, polyvinyl acetal film.
The method of claim 1,
The surface roughness (Rz) of both surfaces of the said polyvinyl acetal film is 20 micrometers or more, The polyvinyl acetal film characterized by the above-mentioned.
The method of claim 1,
The polyvinyl acetal film is triethylene glycol bis 2-ethylhexanoate (3G8), tetraethylene glycol diheptanoate (4G7), triethylene glycol bis 2-ethylbutyrate (3GH), triethylene glycol bis 2-hep 8 to 68% by weight of a plasticizer selected from tanoate (3G7), dibutoxyethoxyethyl adipate (DBEA), dibutyl sebacate (DBS), bis 2-hexyl adipate (DHA), and mixtures thereof Polyvinyl acetal film, characterized in that it contains.
The method of claim 1,
The polyvinyl acetal film, polyvinyl acetal, characterized in that it contains an additive selected from antioxidants, UV stabilizers, UV absorbers, glass adhesion control agents and mixtures thereof in an amount of 0.01 to 1% by weight based on the weight of the film. film.
The method of claim 1,
The polyvinyl acetal film is a polyvinyl acetal film, characterized in that the penetration height is greater than 4m as a result of the penetration resistance test of polyvinyl acetal film laminated glass according to KS L 2007 standard.
(a) preparing a raw material resin by mixing a polyvinyl acetal resin with a plasticizer and heat-resistant coated titanium oxide having a diameter of less than 0.4 µm; And
(b) Melt-extrusion and cooling the raw material resin at a temperature of 100 to 200 ℃ to obtain a final film, the method of producing a polyvinyl acetal film of claim 1.
A solar module encapsulant film comprising the polyvinyl acetal film of any one of claims 1 to 7.