HK1181412B - Curable polyorganosiloxane composition for use as an encapsulant for a solar cell module - Google Patents

Description

Curable polyorganosiloxane compositions for use as sealants for solar cell modules

The present invention relates to a curable polyorganosiloxane (polyorganosiloxane) composition for use as an encapsulant for solar cell modules, in particular for the encapsulation of photovoltaic modules, a cured polyorganosiloxane composition prepared therefrom and a photovoltaic module comprising the same. Suitably, the curable polyorganosiloxane composition is a liquid in the uncured state at room temperature (25 ℃) and cures to an elastomer and forms a permanent adhesion, especially to adjacent glass and plastic substrates, with a strong adhesion, especially after long-term outside weathering or after corresponding accelerated ageing tests.

In a typical photovoltaic solar cell module, crystalline or amorphous semiconductor solar cells are interconnected, mechanically supported and protected from environmental degradation by integrating the cells into a layered structure. The module generally comprises: a transparent front plate or substrate, preferably made of glass; and a rear "backing" or cover (superstrate), which is typically a plastic or metal sheet and sometimes glass. The semiconductor solar cells are typically partially or completely sealed by a sealing material and the interconnected solar cells are located between the front sheet and the backing layer.

Different materials have been considered or used as sealants. In early uses of solar modules for off-earth applications, silicone sealants were the material of choice because of their excellent insulating properties and stability to extreme temperature conditions and radiation. See, e.g., P.Berman and R.K. Yasui, Technical report 32-7547, Jet progress Laboratory, Calif. Institute of Technology, 1971. In General, silicone compositions curable by reaction of SiH-groups with silicon-bonded alkenyl groups (so-called addition cure materials) are described in the patent literature, for example Sylgard 182 or 184 by dow corning corp or RTV 615 by General Electric, for example in US 4056405, US 4093473, US4143949 or US 4167644. Silicone sealants were later found to be too expensive or too complex for widespread use in land modules. Organic polymers are becoming more important and Ethylene Vinyl Acetate (EVA) is considered to be the best encapsulant for modules with crystalline solar cells. However, EVA tends to fade over time under the influence of sunlight, a process that reduces module efficiency. Another disadvantage is the need for a vacuum laminator for making EVA sealed modules. To avoid such time consuming and complex processes, a process for economical module manufacture may be desirable. Silicone sealants in turn become a concern and especially addition cure materials because there are no cure byproducts (WO2005/006451 a 1). One of the most important conditions for the suitability of silicones is adhesion to the substrate, which is in contact with the sealant.

Addition-cured silicone materials generally adhere poorly to most substrates. For many years, numerous patent and scientific publications have disclosed the description of addition-cured materials with tack (e.g. US3,699, 072, US3,892,707, US4,077,943, US4,082,726, US4,087,585, US4,245,079, US4,257,936, US4,677,161, US4,701, 503, US4,721, 764, US4,912, 188, US5,051, 467, US5,106,933, US5,312,855, US5,364,921, US5,438,094, US5,516, 823, US5,536,803, US 6,743,515, US 7,119,159, US 7,288,322, US20030236380, US20050089696, WO 2008127, toshinouski and Akira Kasuya, j. adhision sci. technol. volume 3, No. 6, page 463-page 1989), the enormous variety and complexity of Adhesion phenomena reflecting the same and the general need to be solved with the same additives. Many patents are directed to the manufacture of composite materials composed of thermoplastic materials and silicone. Others are designed to use silicone as an adhesive on a metal substrate. Glass is also mentioned as a substrate in some cases. However, in these documents, only the adhesion properties (if present) of the initially cured silicone compositions are reported. However, for use in photovoltaic solar cell applications, any encapsulant must provide not only excellent initial adhesion properties, but also excellent long-term adhesion properties, given that the lifetime of the photovoltaic solar cell module is typically guaranteed for up to 25 years and given that the extreme weathering conditions to which the photovoltaic solar cell module is exposed include extreme temperature differences, humidity, ultraviolet light, and the like.

Furthermore, the encapsulant of the photovoltaic solar cell module must not release volatile components during its operation time that may lead to corrosion or fogging of the cell module material, which in turn may lead to failure or reduced efficacy of the photovoltaic solar cell module.

Other requirements for the encapsulant of a photovoltaic solar cell module than those mentioned above are the need for simultaneous primer-free adhesion to different substrates involved in the manufacture of the photovoltaic solar cell module, including glass, coated glass, and other substrates such as metals, polymers, etc. Primerless adhesion is required for a cost effective manufacturing process of photovoltaic modules. Other requirements for efficient and economical manufacturing are high curing speed and low temperature for cross-linking and adhesion formation.

Numerous publications have investigated the encapsulation of semiconductor devices, including LEDs or ICs (JP 2009235265; US 20060270792; US 20070032595; JP 6016942; US 5021494; JP 2006335857; US 20040178509; US 20037963; EP 1801163). However, the requirements for such semiconductor devices are not critical, since in general the moisture exposure, temperature variations and thermal expansion due to temperature variations, acid rain exposure, sun exposure are lower compared to solar modules. Also, the substrates used in the sealing of the semiconductor device are different from those used in the solar module. In the solar module used in the present invention, special glasses and films that are not used in semiconductor devices are used.

WO2005/006451 a1 describes solar cell modules with cured silicone sealants obtained by various curing mechanisms including hydrosilylation and the like. Various types of SiH crosslinking agents are mentioned (including Si-H only terminated crosslinking agents), however, they are not specified in terms of long-term service life. Likewise, the examples do not provide a clear disclosure of the nature of the SiH-crosslinking agent. It appears that Si-crosslinkers with low Si content have been used.

The present invention is based on the discovery that silicone sealants for photovoltaic modules that meet the above needs require a specific selection of SiH cross-linkers. The specific curable polyorganosiloxane compositions of the present invention pass accelerated aging tests without failing or reducing the efficacy of photovoltaic solar cell modules and can be cured at low temperatures.

The present invention provides a curable polyorganosiloxane composition for use as a sealant, said composition comprising:

(A) at least one polyorganosiloxane having at least two unsaturated hydrocarbyl residues,

(B) at least one polyorganohydrogensiloxane having at least 7 Si atoms, wherein the molar ratio of SiH groups to all Si atoms is greater than 0.55,

(C) at least one hydrosilylation catalyst,

(D) optionally at least one adhesion promoter,

(E) optionally at least one reinforcing filler,

wherein the molar ratio of the total amount of SiH groups in component (B) to the total amount of unsaturated hydrocarbyl residues in component (A) in the formulation is between 0.7 and 4, preferably between 1 and 4, wherein the encapsulant is for a solar cell module.

The term "encapsulant" as used in the present invention shall include, but is not limited to, materials that partially or completely cover substrates, including semiconductor elements (especially photovoltaic solar cell semiconductor elements), glass substrates, metal substrates, plastic substrates, and the like, all for use in solar cell modules, especially photovoltaic solar cell modules. "partially" in the context of the present invention may include the case where the substrate (including semiconductor elements, glass substrates, metal substrates, plastic substrates, etc., all for solar cell modules, in particular photovoltaic solar cell modules) is only partially covered by the cured silicone composition, e.g., partially covers the semiconductor elements, e.g., serves as a back layer (opposite the light receiving side) of the semiconductor elements, and optionally serves as leads connected to the semiconductor elements in the solar cell module, in particular photovoltaic solar cell module. "partially" may also include the use of a curable composition to simultaneously partially coat a portion of the glass substrate and a portion (especially the back side) of the semiconductor element, in particular to form a complete envelope surrounding the semiconductor element in the solar cell module. "partially" may also include the use of a curable composition to coat the semiconductor element on a surface (i.e., the side where light enters the solar cell module). "completely" may include in particular the case where the substrate (including semiconductor elements, glass substrates, metal substrates, plastic substrates, etc., all for solar cell modules, in particular photovoltaic solar cell modules) is completely surrounded by the cured silicone composition. Other embodiments of photovoltaic solar cell modules using the silicone encapsulant of the present invention are explained below. The silicone encapsulant of the present invention is characterized by improved adhesion to several possible materials used in photovoltaic solar cell modules, including glass substrates (with and without coatings), barrier foils (such as those made from fluorothermoplasts or EVA copolymers), semiconductor elements, such as crystalline or polycrystalline silicon or thin film silicon, such as amorphous, semi-crystalline silicon, gallium arsenide, copper indium diselenide, cadmium telluride, copper indium gallium diselenide. In addition, the silicone sealant of the present invention is characterized by improved adhesion to these substrates over a long period of time under severe conditions of high temperature change at high humidity. In a preferred embodiment, the silicone sealant of the present invention is in contact with a barrier foil, preferably a backing layer foil, while optionally contacting the semiconductor element.

Components (A)

The compositions of the invention comprise at least one polyorganosiloxane (component (a)) having at least two unsaturated hydrocarbyl residues. Component (a) may comprise one or more polyorganosiloxanes having, on average, at least two alkenyl groups. Suitable components (A) can be described by the general formula (4),

[M_aD_bT_cQ_dR⁹ _e]_m(4)

wherein the index in formula (4) represents the ratio of siloxy units M, D, T and Q, which siloxy units may be blocked (blockwise) or randomly distributed in the polysiloxane. Within the polysiloxane, the individual siloxane units may be the same or different and

a =0 to 10

b =0 to 2000

c =0 to 50

d =0 to 1

e =0 to 300

m =1 to 1000

Wherein a, b, c, D and m are such that the viscosity of component (a) at 25 ℃ is less than 50000 mpa.s (at 25 ℃ with D =1 s)^-1Shear rate measurement of).

The viscosity of component (A) refers to the viscosity of component (A) alone or a mixture of components (A). In the latter case, the mixture comprises individual components (A) present therein which may have a viscosity of over 50000 mPa.s at 25 ℃, for example a resin component (A) comprising Q and or T units.

In the formula (4), the index should represent M based on the number average molecular mass_nAverage degree of polymerization P of_n。

In formula (4):

M=R₃SiO_1/2or M

D=R₂SiO_2/2Or D

T= RSiO_3/2Or T^*

Q=SiO_4/2，

Divalent R⁹Is a bridging group between the aforementioned siloxy groups, wherein each R, which may be the same or different, is selected from optionally substituted alkyl groups having up to 30 carbon atoms, optionally substituted aryl groups having up to 30 carbon atoms, poly (C) s having up to 1000 alkyleneoxy units₂-C₄) Alkylene ethers, the R radical being free of aliphatic unsaturation, and

wherein M = R¹ _pR_3-pSiO_1/2,D^*= R¹ _qR_2-qSiO_2/2, T^*=R¹SiO_3/2，

Wherein

p =0 to 3, preferably 1 to 3,

q =1 to 2, and

R⁹is defined as follows.

R is preferably selected from the group consisting of n-, iso-or tertiary alkyl, alkoxyalkyl, C₅-C₃₀Cycloalkyl or C₆-C₃₀Aryl, alkylaryl, which radicals may in turn be substituted by one or more O-, N-, S-or F-atoms, or poly (C) having up to 500 alkyleneoxy units₂-C₄) Alkylene ethers, the R group being free of aliphatic unsaturation.

Examples of suitable monovalent hydrocarbon groups include: alkyl, preferably, for example, CH₃-、CH₃CH₂-、(CH₃)₂CH-、C₈H₁₇-and C₁₀H₂₁-; and alicyclic groups such as cyclohexylethyl; aryl groups such as phenyl, tolyl, xylyl; aralkyl radicals, such as benzyl and 2-phenylethyl. Preferred monovalent halogenated hydrocarbon groups have the formula C_nF_2n+1CH₂CH₂Where n has a value of 1 to 10, for exampleE.g. CF₃CH₂CH₂-、C₄F₉CH₂CH₂-、C₆F₁₃CH₂CH₂-、C₂F₅-O(CF₂-CF₂-O)_1-10CF₂-、F[CF(CF₃)-CF₂-O]_1-5-(CF₂)_0-2-、C₃F₇-OCF(CF₃) -and C₃F₇-OCF(CF₃)-CF₂-OCF(CF₃)-。

Preferred groups for R are methyl, phenyl, 3,3, 3-trifluoropropyl.

R¹Selected from unsaturated groups comprising C = C group containing groups (alkenyl groups), for example: n-, iso-, tert-or cyclic alkenyl, C₆-C₃₀Cycloalkenyl radical, C₈-C₃₀Alkenylaryl, cycloalkenylalkyl, vinyl, allyl, methallyl, 3-butenyl, 5-hexenyl, 7-octenyl, ethylidene-norbornenyl, styryl, vinylphenethyl, norbornenyl-ethyl, limonene, optionally substituted with one or more O-or F-atoms; or a C.ident.C group-containing radical (alkynyl), which optionally contains one or more O-or F-atoms.

The alkenyl group is preferably attached to the terminal silicon atom and the olefin functionality is located at the end of the alkenyl group of the higher alkenyl group because the alpha, omega-dienes used to prepare the alkenylsiloxane are more readily available.

R¹Preferred groups of (a) are vinyl, 5-hexenyl, cyclohexenyl, limonyl (limonyl), styryl, vinylphenethyl.

R⁹Including, for example, divalent aliphatic or aromatic n-, iso-, tert-or cycloalkylene, arylene or alkylenearyl radicals having up to 14 carbon atoms. R⁹Forming a bridging element between the two siloxy units. R⁹The content of groups does not exceed 30 mol.%, preferably 20mol.%, of the total siloxy units. Preferably, R⁹Is absent. Suitable divalent hydrocarbon radicals R⁹Is superior toAlternative examples include any alkylene residue, preferably for example-CH₂-、-CH₂CH₂-、-CH₂(CH₃)CH-、-(CH₂)4-、-CH₂CH(CH₃)CH₂-、-(CH₂)₆-、-(CH₂)₈-and- (CH)₂)₁₈-; cycloalkylene groups such as cyclohexylene group; arylene radicals, e.g. phenylene, xylene, and combinations of hydrocarbon radicals, e.g. benzylidene, i.e. -CH₂CH₂-C₆H₄-CH₂CH₂-、-C₆H₄CH₂Preferred groups are α -, omega-ethylene, α -, omega-hexylene or 1, 4-phenylene.

Other examples include divalent halogenated hydrocarbon groups R⁹For example any divalent hydrocarbon radical R in which one or more hydrogen atoms have been replaced by halogen, e.g. fluorine, chlorine or bromine⁹. Preferably the divalent halogenated hydrocarbon residue has the formula-CH₂CH₂(CF₂)_1-10CH₂CH₂-, e.g. -CH₂CH₂CF₂CF₂CH₂CH₂-, or other examples of suitable divalent hydrocarbon ether groups and halogenated hydrocarbon ether groups include-CH₂CH₂OCH₂CH₂-、-C₆H₄-O-C₆H₄-、-CH₂CH₂CF₂OCF₂CH₂CH₂-and-CH₂CH₂OCH₂CH₂CH₂-。

As containing R, R¹And/or R⁹Such polymers of component (a) of the group are, for example, alkenyl-dimethylsiloxy or trimethylsiloxy terminated polydimethylsiloxanes which may contain siloxane units other than alkenylmethylsiloxy groups, dimethylsiloxy groups, for example poly (dimethyl-co-diphenyl) siloxane.

In general, component (A) of the compositions of the invention may be a composition containing oxygen and/or divalent radicals R⁹Any polyorgano of two or more silicon atoms linkedA siloxane compound in which each silicon atom is bonded to 0 to 3 monovalent groups, with the proviso that the polyorganosiloxane compound contains at least two silicon-bonded unsaturated hydrocarbon residues.

Having R and/or R¹The siloxane units of the group may be the same or different for each silicon atom. In a preferred embodiment, the structure is

R¹ _pR_3-pSiO[R₂SiO]_m1[R¹RSiO]_nSiR¹pR_3-p(1)

p =0 to 3, preferably 1,

m1 =0 to 2000, preferably 10 to 1000,

n =0 to 500, preferably 0 to 200.

A preferred polyorganosiloxane component (A) of the composition of the present invention is a substantially linear polyorganosiloxane (A1). The expression "substantially linear" includes polyorganosiloxanes (a1) containing no more than 0.2 mol.% (traces) of siloxy units in T or Q form. This means that the polymer (a) is preferably a linear, flowable fluid (a 1):

wherein R is¹R, p and m1 are as defined above,

provided that at least two alkenyl groups are present per molecule.

The preferred structure includes:

Vi_pMe_3-pSiO(Me₂SiO)_10-2000SiMe₃._PVi_p(1b)

PhMeViSiO(Me₂SiO)_10-2000SiPhMeVi(1c)。

in the group of alkenyl-containing siloxanes (a), it is preferred to add a second or third siloxane as component (a2) and/or (A3). The use of the so-called vinyl-rich polymer components (A2) and (A3) is to improve the mechanical properties and the crosslink density.

The polymer (a2) is selected from polymers of formulae (1d) to (1i), i.e. linear polyorganosiloxanes having other alkenyl side groups, in which the concentration of T-and Q-groups is lower than 0.2 mol.%, or polyorganosiloxanes having a higher concentration of T-and Q-groups than the previous polymers of type (a1) or (a 2).

The polymer (A2) is represented by formula (6)

R¹ _pR_3-p(R₂SiO)_b1(R^lRSiO)_b1xSiR_3-pR_p ¹(1d)

Me₃SiO(Me₂SiO)_b1(MeR¹SiO)_b1xSiMe₃(1e),

R¹Me₂SiO(Me₂SiO)_b1(Me R¹SiO)_b1xSiMe₂R¹(1f),

Wherein

b1 = >0 to 2000

b1x =0 to 500

b1 + b1x = >10 to 100

R¹R, p are as defined above,

r = is preferably vinyl, hexenyl, cyclohexenyl, limonyl (limonyl), styryl, vinylphenethyl.

Preferred groups for R are methyl, phenyl, 3,3, 3-trifluoropropyl.

Preferred values of b1x are less than 0.5 × b1, preferably 0.0001 × b1 to 0.25 × b1, more preferably 0.0015 × b1 to 0.2 × b 1.

(A2) Is of other preferred structure

Vi_pMe_3-pSiO(Me₂SiO_10-2000(MeViSiO)_1-1000SiMe_3-pVi_p(1g),

Me₃SiO(Me₂SiO)_10-2000(MeViSiO)_1-1000SiMe₃(1h),

PhMeViSiO(Me₂SiO)_10-2000(MePhSiO)_1-1000SiPhMeVi (1i) and wherein Me = methyl, Vi = vinyl, Ph = phenyl, and p = 03, preferably p = 1.

The third component of polymer (a), branched polymer (A3), is preferably selected from those of formula (4a) wherein the alkenyl-containing polyorganosiloxane (A3) has greater than 0.2 mol.% of T = RSiO₃/₂Or Q = SiO_4/2-a unit.

[M₀._4-4D_0-1000T_0-50Q_0-1]_1-1000(4a)

Wherein

M=R₃SiO_1/2Or M

D=R₂SiO_2/2Or D is^*

T=RSiO_3/2Or T

Q=SiO_4/2，

Wherein M, D and T are as defined above, carrying an unsaturated group R¹. The amount of such M, D and T units is preferably from 0.001 to 20mol.%, more preferably from 0.01 to 15 mol.%, most preferably from 0.1 to 10mol.%, based on all siloxy units.

The range of the fractional index is defined in terms of the number average molecular weight M_nPossible average degree of polymerization P_nThe range of (1). The index relates to the suitable viscosity defined later and describes the polymer without any solvent for viscosity adjustment.

Preferably, the branched polyorganosiloxanes (A2) and (A3) generally have a higher concentration of unsaturated groups R¹. Branched polymers(A3) Described for example in US 5109095. Preferably, the branched vinyl-rich polymer (a3) has the following ranges:

D : T>10: 1, preferably>33: 1, and/or respectively (M: Q) = 0.6-4: 1, e.g., [ M: Q ]₀.₇M*₀.₀₅Q]_10-500(1j)。

All of these polymers can be prepared by any conventional method for preparing triorganosiloxane-terminated polydiorganosiloxanes. For example, the correct ratio of suitable hydrolyzable silanes (e.g., vinyldimethylchlorosilane, trimethylchlorosilane, tetrachlorosilane, methyltrichlorosilane and dimethyldichlorosilane, or their corresponding alkoxysilanes) can be cohydrolyzed and condensed. Other reaction pathways may be alternatively followed during the equilibration reaction of 1, 3-divinyl-tetraorganodisiloxane (e.g. sym-divinyldimethyldiphenylsiloxane or divinyl-tetramethylsiloxane) which supplies the end groups of the polydiorganosiloxane, which equilibration reaction may be equilibrated with a suitable polydiorganosiloxane (e.g. octamethylcyclotetrasiloxane) in the presence of acidic or basic catalysts.

In a preferred embodiment, polymer component (a) is a mixture of polymers of formula (1a) and/or polymers of formula (1d) and/or (1j), wherein the average alkenyl content of the mixture is preferably less than 2mol.% of all siloxy units of mixture (a), wherein polymer (a1) is present in an amount higher than (a2) or (A3).

The viscosity of the polydiorganosiloxane (a) defined above for the purposes of the present invention means the cyclic polydiorganosiloxane fraction (measured at 50 ℃ and 20 mbar over 1 hour, less than 1 wt.%, preferably 0.5 wt.%) which is preferably substantially free of polyorganosiloxane.

By relative to M based on the number average molar weight_nGPC measurement of the polystyrene Standard of (A), the average polymerization degree P of the siloxane units (M, D, T, Q) of the Polymer (A)_nIs P_n>10 to 2000, more preferably in the range of 40 to 1000. Viscosity ranges for such polymersAt 25 ℃ and a shear rate D =1 s^-1At a pressure of from 10 to 100,000 mPa.s, more preferably from 40 to 50,000 mPa.s.

In a preferred embodiment, the polymer (a) has a molecular weight distribution at 25 ℃ and D =1 s^-1Lower than 15,000mpa.s in order to ensure that the viscosity of the sealant composition is sufficiently high, which is advantageous for sealing larger joints.

The alkenyl content of component (A) may here be determined by¹H NMR determination-see A.L. Smith (eds.). The Analytical Chemistry of Silicones, J.Wiley&Sons 1991, volume 112, page 356, and edited by Chemical Analysis, j.d. wineforder.

Components (B)- Crosslinking agent

Component (B) is at least one polyorganohydrogensiloxane having at least 7 Si atoms, in which the molar ratio of SiH groups to all Si atoms is greater than 0.55, preferably ≥ 0.6, still more preferably ≥ 0.7, particularly preferably 0.7 to 0.95.

Suitable polyorganohydrogensiloxanes (B) containing SiH units can be formally described by the general formula (2),

[M¹ _a2D¹ _b2T¹ _c2Q_d2R⁹ _e2]_m2(2)

in the siloxy unit

M¹Is as defined above, or M,

D¹(ii) = D, as defined above, or D,

T¹t, as defined above, or T x,

q is as defined above in the description of the invention,

R⁹as defined above, in the above-mentioned manner,

M**= HR₂SiO_1/2, D**= HRSiO_2/2, T**= HSiO_3/2，

a 2= 0.01 to 10, preferably =2 to 5, more preferably =2

b 2= 0 to 1000, preferably =10 to 500

c 2= 0 to 50, preferably =0

d 2= 0 to 1, preferably =0 or 1, most preferably =0

e 2= 0 to 3, preferably =0

m2= 1 to 1000, preferably =1 to 500, most preferably =1,

with the proviso that in formula (2) at least 7 Si atoms are present and the molar ratio of SiH-groups (siloxy groups containing SiH groups) to all Si-atoms is greater than 0.55. Preferably, component (B) is selected from polysiloxanes having only methyl or phenyl groups as organic residues.

Preferably, the polyorganohydrogensiloxane (B) has at least 10, preferably at least 15, more preferably at least 20, still more preferably at least 25 and most preferably at least 30 silicon atoms.

The siloxy units may be blocky or randomly distributed in the polymer chain.

The above index should be expressed on the basis of the number-average molecular mass M_nAverage degree of polymerization P of_n。

The range of M-, D-, T-and Q-units present in the molecule can cover almost all values representing fluids, flowable polymers, liquids and solid resins. Preferably, liquid linear, cyclic or branched siloxanes are used. Optionally, these siloxanes may contain additional traces of C remaining from synthesis₁-C₆Alkoxy or Si-hydroxy.

Preferred structures of component (B) in the compositions of the invention are siloxanes of the formulae (2a) to (2 d).

H_a1(R)_3-a1Si[RHSiO]_x[R₂SiO]_y[RR¹SiO]_zSi(R)_3-a1H_a1(2a)

More specifically:

HR₂SiO(R₂SiO)_y(RR¹SiO)_z(RHSiO)_xSiR₂H(2b)

HMe₂SiO(Me₂SiO)_y(RR¹SiO)_z(MeHSiO)_xSiMe₂H(2c)

Me₃SiO(MeHSiO)_xSiMe₃(2d)

wherein R and R¹R is preferably methyl and/or phenyl, R being as defined above¹Preferably vinyl, and the index 'a1' is 0 to 1, preferably 0, and

x =2 to 1000, preferably =2 to 500,

y =0 to 650, preferably =0 to 100,

z =0 to 65, preferably =0

7. ltoreq. x + y + z <1000, preferably 10. ltoreq. x + y + z <650,

wherein in each of the formulae (2a) to (2d) the molar ratio of SiH groups to all Si atoms is greater than 0.55.

Furthermore, there may be polyorganohydrogensiloxanes of the resin of the formula:

{[T¹][R¹⁰O_1/2]_n2}_m2(2e)

{[SiO_4/2}][R¹⁰O_1/2]_n2[M¹]₀,_01-10[T¹]_0-50[D]_1-1000}m2(2f)

wherein

T¹、M¹、D¹As defined above, in the above-mentioned manner,

n 2= 0 to 3

m2 is as defined above

R¹⁰Is hydrogen, C₁-C₂₅Alkyl groups such as methyl, ethyl, N-propyl, isopropyl, N-, iso-and tert-butyl, alkanoyl groups such as acyl, aryl, N = CHR such as butanone oxime, alkenyl groups such as propenyl,

wherein in the formulae (2e) to (2f), the molar ratio of SiH groups to all Si atoms is greater than 0.55 and the total number of Si atoms is at least 7

One preferred embodiment of compound (2f) is provided, for example, by a monomeric to polymeric compound, which may be represented by the formula [ (Me)₂HSiO_0.5)_kSiO_4/2]_1,5-1000Described, wherein the index k is from 0.3 to 4. Such liquid or resin molecules may contain significant concentrations of SiOH-and/or (C) of up to 10mol.% relative to the silicon atom₁-C₆) alkoxy-Si groups.

Specific examples of preferred suitable compounds for component (B) in the composition of the present invention include

Me₃SiO-(MeHSiO)_5-650-SiMe₃,

(MeHSiO)₇,

HMe₂SiO(Me₂SiO)_0-300MePhSiO)_0-300(MeHSiO)_1-650SiMe₂H,

Me₃SiO(Me2SiO)_0-300(MePhSiO)_0-300(MeHSiO)_2-650SiMe₃,

Me₃SiO(Me₂SiO)_0-300(Ph₂SiO)_0-300(MeHSiO)_2-650iMe₃,

Wherein in each formula the molar ratio of SiH-groups to all Si-atoms is greater than 0.55 and the total number of Si atoms is at least 7.

Component (B) may be used as a single component of a polyorganosiloxane polymer or a mixture thereof.

If it is to beIn an attempt to increase the cure rate, it is preferred to use a composition having HMe₂SiO_0,5Some organopolysiloxane (B) or homo-polymeric MeHSiO-polymer of the units to adjust the curing rate to shorter times.

If it is necessary to increase the curing rate still further, this can be achieved, for example, by increasing the molar ratio of SiH to Si-alkenyl or by increasing the amount of catalyst (C).

Component (B) preferably has a viscosity of from 2 to 1000 mpa.s at 25 ℃.

Preferably, the crosslinking agent (B) should have at least more than 3, more preferably more than 15, still more preferably more than 20 and most preferably more than 25 SiH-groups per molecule.

In this formulation, the molar ratio of the total amount of SiH groups in component (B) to the total amount of unsaturated hydrocarbyl residues R in component (a) and if present in (B) is from 0.7 to 4, preferably from 1 to 4, more preferably from 0.8 to 2,5, more preferably from 1.0 to 2.1, still more preferably from 1.2 to 2, in order to provide a high efficiency photovoltaic module comprising the encapsulant according to the present invention.

Component (B) does not comprise component (D) or in other words is different from component (D).

Components (C)- Catalyst and process for preparing same

The composition of the present invention contains as component (C) at least one hydrosilylation catalyst selected from organometallic compounds, salts or metals and having the ability to catalyze hydrosilylation, wherein the metal is selected from Ni, Ir, Rh, Ru, Os, Pd and Pt compounds, as taught in the following patents: US3,159,601; US3,159,662; US3,419,593; US3,715,334; US3,775,452 and US3,814,730.

Component (C) used in the hydrosilylation reaction of the composition of the present invention is a catalyst compound that facilitates the reaction of the silicon-bonded hydrogen atoms of component (B) with the silicon-bonded olefinic substituents of component (a). The metal or organometallic compound can be any catalytically active metal and is typically a catalytically active component containing a platinum group metal. Without wishing to be bound by theory, it is believed that the catalyst (C) comprises complexes of sigma-and pi-bonded carbon ligands and ligands having S-, N, or P atoms, metal colloids or salts of the above metals. The catalyst may be present on a support, such as silica gel or powdered charcoal, which carries the metal, or a compound or complex of the metal. Preferably, the metal of component (C) is any platinum complex compound.

Typical platinum-containing catalyst components in the polyorganosiloxane compositions according to the invention are any form of platinum (0), (II) or (IV) compound which is capable of forming a complex with the phosphites according to the invention. The preferred complex is Pt-⁽⁰⁾Alkenyl complexes, such as alkenyl, cycloalkenyl, alkenyl siloxanes, such as vinylsiloxanes, because of their easy dispersibility in polyorganosiloxane compositions.

A particularly useful form of platinum complex is Pt with an aliphatically unsaturated organosilicon compound, e.g., 1, 3-divinyltetramethyldisiloxane⁽⁰⁾Complexes (vinyl-M2 or Karstedt's catalyst), as disclosed by US3,419,593, incorporated herein by reference, particularly preferred are cyclohexene-Pt, cyclooctadiene-Pt and tetravinyltetramethyl-tetracyclosiloxane (vinyl-D4).

Pt⁰The olefin complex is, for example, in 1, 3-divinyltetramethyldisiloxane (M)^Vi ₂) For example, hexachloroplatinic acid or other platinum chlorides by reduction with an alcohol in the presence of a basic compound such as an alkali metal carbonate or hydroxide.

The amount of platinum-containing catalyst component used in the compositions of the present invention is not narrowly limited, provided that a sufficient amount is present to accelerate the hydrosilylation between (a) and (B) at the desired temperature for the desired time (B) in the presence of all other ingredients of the composition of the present invention. The exact necessary amount of the catalyst component will depend on the particular catalyst, the amount of other inhibiting compounds and the SiH to olefin ratio and is not readily predictable. However, for platinum catalysts, the amount may be as low as possible for cost reasons. Preferably, more than one part by weight of platinum should be added per one million parts by weight of silicone components (a) and (B) to ensure cure in the presence of other undefined trace inhibitors. For the compositions of the invention to be used by the coating process of the invention, the amount of platinum-containing catalyst component used is preferably sufficient to provide from 1 to 200ppm, preferably from 2 to 100ppm, particularly preferably from 4 to 60ppm, by weight of platinum per weight of polyorganosiloxane components (A) + (B).

Preferably the amount is at least 10ppm by weight per total weight of (A) + (B).

The hydrosilylation catalyst may also be selected from catalysts capable of being photosensitized.

These photosensitizable catalysts preferably contain at least one metal selected from the group consisting of Pt, Pd, Rh, Co, Ni, Ir, or Ru. The catalyst capable of being photosensitized preferably comprises a platinum compound.

The catalyst, which can be photoactivatable, is preferably selected from organometallic compounds, i.e. including carbon-containing ligands or salts thereof. In a preferred embodiment, the photoactive catalyst (C) has metallic carbon bonds, including sigma-and pi-bonds. Preferably, the catalyst (C) capable of being photosensitized is an organometallic complex compound having at least one metallic carbon sigma bond, still more preferably a platinum complex compound preferably having one or more sigma-bonded alkyl and/or aryl groups, preferably alkyl groups. Sigma-binding ligands include, inter alia: sigma-bonded organic groups, preferably sigma-bonded C₁-C₆Alkyl groups, more preferably sigma-bonded methyl groups, sigma-bonded aryl groups such as phenyl groups, Si and O substituted sigma-bonded alkyl or aryl groups, e.g. triorganosilylalkyl groups, sigma-bonded silyl groups such as trihydrocarbylsilyl groups the most preferred photoactivatable catalysts comprise η with sigma-bonded ligands, preferably sigma-bonded alkyl ligands⁵- (optionally substituted) -cyclopentadienylplatinum complex compounds.

Other catalysts capable of being photosensitized include (η -diene) - (σ -aryl) -platinum complexes (see, e.g., US4,530,879).

The catalyst capable of being photosensitized may be used as it is or supported on a carrier.

The catalyst capable of being photosensitized is one that provides an additional option to extend the bath life of the reactive silicon-based composition in addition to the phosphites of the present invention and allows for extended processing times before the components gel.

Examples of catalysts that can be photosensitized include η -diene- σ -aryl-platinum complexes such as those disclosed in US4,530,879, EP122008, EP146307 (corresponding to US4,510,094 and the prior art documents cited herein), or US 2003/0199603; and platinum compounds, the reactivity of which can be controlled, for example, using azodicarboxylic acid esters (as disclosed in US4,640,939) or diketones.

Platinum compounds capable of being photosensitized which may be used are also those selected from the group having ligands selected from diketones (for example, benzoylacetone or acetylene dicarboxylate) and platinum catalysts embedded in a photodegradable organic resin. Other Pt catalysts are described, for example, in U.S. Pat. No. 3,715,334 or U.S. Pat. No. 3,419,593, EP 1672031A 1, and in Lewis, Colborn, Grade, Bryant, Sumpter and Scott in Organometallics,1995, 14, 2202-2213, all of which are incorporated herein by reference.

It is also possible to use Pt⁰The olefin complex and the addition thereto of a suitable photoactivatable ligand form in situ in the silicone composition to be shaped a catalyst capable of being photoactivated.

However, the catalyst capable of being photosensitized which can be used herein is not limited to these above examples.

The most preferred catalyst capable of being photosensitized to be used in the process of the present invention is (η)⁵-cyclopentadienyl) -trimethyl-platinum, (η)⁵-cyclopentadienyl) -triphenyl-platinum complexes, especially (η)⁵-methylcyclopentadienyl) -trimethyl-platinum.

The amount of catalyst capable of being photoactivatable is preferably from 1 to 500ppm and preferably within the same smaller range as defined for the heat-activatable hydrosilylation catalyst above.

As already explained above, the specific phosphites used according to the invention interact with those conventional transition metal compounds via a ligand exchange reaction, thereby influencing the hydrosilylation activity of the catalyst to provide a surprisingly excellent balance between storage stability after curing and high temperature reactivity.

Components (D) ：

The curable polyorganosiloxane composition optionally comprises at least one adhesion promoter (D).

Component (D) is preferably selected from at least one of the following:

(D1) at least one organosiloxane comprising at least one alkoxysilyl group;

(D2) at least one organosilane comprising at least one alkoxysilyl group;

(D3) at least one aromatic organic compound having at least two aromatic moieties and at least one group reactive in hydrosilylation;

component (D1) is preferably a polyorganosiloxane comprising at least one unit selected from:

RHSiO_2/2and

R⁵(R)SiO_2/2，

wherein R is as defined above and may be the same or different, R⁵Selected from the group consisting of unsaturated aliphatic groups having up to 14 carbon atoms, epoxy-containing aliphatic groups having up to 14 carbon atoms, cyanurate-containing groups, and isocyanurate-containing groups, and

also comprises at least one unit of formula (3):

O_2/2(R)Si-R⁴-SiR_d(OR³)_3-d(3)

wherein

R is as defined above and may be the same or different,

R³selected from H (hydrogen) and alkyl groups having 1 to 6 carbon atoms, and may be the same or different,

R⁴is a bifunctional, optionally substituted hydrocarbon radical having up to 15 carbon atoms, which may contain one or more heteroatoms selected from O, N and S atoms, and which is bonded to the silicon atom by a Si-C bond, and

d is 0 to 2.

Examples of component (D1) include compounds of formulae (3 a-3D):

R¹¹is R or R⁵Wherein R, R³、R⁴And R⁵As defined above and may be the same or different,

s1 =0 to 6, preferably 1

t1 =0 to 6, preferably 1 or 2

s1 + t1 =2 to 6, preferably 2 or 3

With the proviso that at least one group- (OSi (R) H) -or- (OSi (R) is present in the compound¹¹) -; preferred are compounds of the formula:

(3b)

r, R therein³、R⁴And R¹¹As previously defined; and ring position isomers thereof, i.e., compounds of the formula:

(3c)

and ring position isomers thereof, the compounds of formula (I).

Further, compounds of the formula:

wherein:

R、R³、R⁴、R⁵as defined above

s =0 to 10, preferably =0 to 5

t =0 to 50, preferably =2 to 30

u =1 to 10, preferably =1

s + t+ u =≤ 70

With the proviso that at least one group- (OSi (R) H) -or- (OSi (R) is present in the compound⁵) -. These compounds may contain a certain amount of Q or T branching groups to replace the D units.

R⁵For example selected from:

。

component (D2) is preferably selected from compounds of formula (4):

X-(CR⁶ ₂)_e-Y-(CH₂)_eSiR_d(OR³)_3-d

wherein

X is selected from the group consisting of halogen, pseudohalogen, unsaturated aliphatic groups having up to 14 carbon atoms, epoxy-containing aliphatic groups having up to 14 carbon atoms, cyanurate-containing groups, and isocyanurate-containing groups,

y is selected from a single bond, a heteroatom group selected from-COO-, -O-, -S-, -CONH-, -HN-CO-NH-,

R⁶selected from hydrogen and R is as defined above,

e is 0, 1, 2, 3,4, 5, 6,7 or 8, and may be the same or different,

r is as defined above and may be the same or different,

R³as defined above and may be the same or different,

d is 0, 1 or 2.

Preferred examples of the component (D2) include:

(3e)

(3f)

(3g)

(3h)

wherein R and d are as defined above.

Component (D2) may additionally be used as an in situ surface treatment agent for filler (E) in addition to acting as a tackifier. It is preferred to use a mixture of silanes of component (D2) to obtain acceptable adhesion properties at reduced cost.

Component (D3) is preferably selected from compounds of formula (3 i):

wherein

R is 0 or 1, and R is a hydrogen atom,

R⁷which may be the same or different, are selected from the group consisting of a hydrogen atom, a hydroxyl group, a halogen atom, an alkyl group, an alkenyl group, an alkoxy group, an alkenyloxy group, an alkenylcarbonyloxy group and an aryl group, and

formula-E_f-Si(OR)_3-dR_dWherein R are the same or different and d is as defined above,

of the formula-O-Si (R)₂R¹Wherein R and R¹As defined above, in the above-mentioned manner,

formula-E_f-Si(R)₂A group of H, wherein R is as defined above,

wherein E is a divalent organic radical having up to 8 carbon atoms and from 0 to 3 heteroatom radicals selected from the group consisting of-O-, -NH-, C = O and-C (= O) O-, and

f is 0 or 1, and f is,

and Z is selected from the following groups:

or

Wherein R is⁸Selected from a hydrogen atom, a halogen atom, or a substituted or unsubstituted alkyl, aryl, alkenyl and alkynyl group, and

g is a positive number of at least 2,

wherein is selected from R⁷And R⁸At least one of said groups of (a) is reactive in hydrosilylation.

Preferred components (D3) include:

(3j)

wherein Z_r、R⁷、R³R and d are as defined above.

Components (E) Reinforcing filler

The curable polyorganosiloxane compositions used as sealants optionally comprise one or more reinforcing fillers (E) (if appropriate surface-modified). The reinforcing filler (E) is characterized by a thickness of 50m²BET surface area in g or more.

Generally, if the curable polyorganosiloxane composition is radiation cured, such fillers should be transparent and allow or have high light transmission.

The fillers include, for example, all fine-particle fillers, i.e. those having particles of less than 100 μm, i.e. preferably consisting of such particles. These fillers may be mineral fillers, such as silicates, carbonates, nitrides, oxides or silica. The fillers are preferably those known as reinforcing silicas, which allow the production of elastomers having sufficient transparency to radiation. Preference is given to using a crosslinking agentReinforcing silicas which are properties of high cure sealants, especially those which increase strength. Examples are BET surface areas of from 50 to 400 m²Per gram of pyrogenic or precipitated silica. Preferably, these fillers are surface hydrophobized. If component (E) is used, it is present in an amount of 1 to 100 parts by weight, preferably 0 to 70 parts by weight, even more preferably 0 to 50 parts by weight, even more preferably 5 to 45 parts by weight, based on 100 parts by weight of components (A) and (B).

BET surface area higher than 50m²The fillers/g allow the production of silicone elastomers with improved properties. Fumed silica is preferred in view of strength and transparency, and even more preferred silica is, for example, silica having a particle size of more than 200 m²200 and 300 of Aerosil with/g BET surface area, HDK N20 or T30, Cab-O-Sil MS7 or HS 5. As BET surface area increases, so does the transparency of the silicone mixture in which these materials are present. Examples of trade names for materials known as precipitated silica or wet silica are Vulkasil VN3 or FK 160 from Evonik (formerly Degussa), or Nipsil LP from Nippon SilicaK.K. and others.

Preference is given to using BET surface areas of 50m²A BET surface area of at least 150 m/g or more²Silica filler per gram. Such compositions can be photoactivated when desired due to sufficient transmittance.

The filler (E) may be subjected to any suitable conventional surface treatment with a suitable surface treatment belonging to hydrophobization with a suitable hydrophobizing agent, dispersion with a suitable dispersant, which surface treatment affects the interaction of the filler with the silicone polymer, for example, the thickening effect. The surface treatment of the filler is preferably a hydrophobization treatment with a silane or siloxane. For example, it can be performed in situ by adding silazanes such as hexamethyldisilazane and/or 1, 3-divinyltetramethyldisilazane, and adding water, and 'in situ' hydrophobization is preferred. It can also be carried out with other familiar filler treating agents having polyorganosiloxane diols with chain lengths of 2 to 50 and carrying unsaturated organic groups, with the aim of providing reactive sites for the crosslinking reaction.

Examples of commercially available silicas pre-hydrophobized with various silanes are: aerosil R972, R974, R976, or R812, or HDK 2000 or H30, for example. Examples of trade names for materials known as hydrophobized precipitated silicas or wet silicas are e.g. sipernat 10 or D15 from Evonik (formerly Degussa). The rheology (i.e. technical processability) of the non-curing silicone rubber mixture can be influenced by the amount of filler of the type in question, the choice of its amount, and the nature of the hydrophobization.

Conventional auxiliary additives

The curable polyorganosiloxane compositions used as sealants according to the invention may also comprise conventional auxiliary additives.

Such auxiliary or conventional additives may comprise stabilizers for hot air, oils and solvents, processing aids, mold release agents, wetting agents, pigments, functional fillers for increased thermal or electrical conductivity, low-surface or inert fillers (so-called fillers for extended volume), solvents, natural or synthetic fibers for reinforcement, foaming agents for initiating foaming, bactericides, fungicides or additives for increasing mold resistance.

As fillers or extenders (BET surface area)<50 m²Examples of materials per g) are known as non-reinforcing fillers. They include, for example, powdered quartz, diatomaceous earth, powdered white quartz, mica, alumina, and aluminum hydroxide. BET surface area of 0.2 to less than 50m²Titanium dioxide or iron oxide, zinc oxide, chalk or carbon black in a/g ratio can also be used as heat stabilizers. These fillers are available under various trade names, for example Sicron @, Min-U-Sil @, Dicalate @, Crystalite @. BET surface area of less than 50m²The material known as inert filler or filler should advantageously not contain particles of more than 100 μm used in silicone rubbers (<0.005 wt%) so that further processing does not cause problems during downstream processing (e.g., through screens or spray bars), or the mechanical properties of articles made therefrom are not adversely affected. In the presence of an opacifying fillerOf these, also particularly useful are non-transparent, especially inorganic, pigments or carbon blacks.

These opaque fillers are preferably used only when coloring is necessary or a physical function such as thermal conductivity or electrical conductivity is required.

The use of opaque, non-transparent fillers requires changing the general order of activation and shaping steps in the process. Typically, photo-activation by radiation follows the final forming process if no filler is used or a transparent filler is used. If an opaque, non-transparent filler is used that will inhibit photoactivation of the photoactivatable catalyst, a photoactivation step is performed prior to incorporation of the opaque, non-transparent filler and formation of the mixture.

The filler may also be a pigment, such as an organic dye or pigment or an inorganic pigment, as will be appreciated by those skilled in the art.

Auxiliary or conventional additives further include, for example, plasticizers, or mould release oils (release oils), or hydrophobic oils, such as polydimethylsiloxane oils, preferably having a viscosity of 0.001 to 10Pa.s at 25 ℃. Additional mould release or flow improvers may also be used, examples being fatty acid derivatives or fatty alcohol derivatives, fluoroalkyl surfactants. The compounds advantageously used here are those which rapidly dissociate and migrate to the surface. For example, known hot air stabilizers, such as Fe-, mn-, Ti-, Ce-, or La-compounds and organic salts thereof, preferably organic complexes thereof, can be used to increase the stability after hot air exposure. The auxiliary additives may also include so-called inhibitors for controlling the crosslinking reaction. However, the presence of those inhibitors is generally not preferred. However, if it is intended to extend the shelf life (pot-life) of the silicone composition to be shaped, for example, in the case where the non-transparent filler is to be compounded after photoactivation, the use of such inhibitors may be suitable to reduce the rate of curing. Examples of advantageous inhibitors include, for example, vinylsiloxanes, 1, 3-divinyltetramethyldisiloxane, or tetravinyl-tetramethyl-tetracyclosiloxane. It is also possible to use other known inhibitors, such as ethynylcyclohexanol, 3-methylbutynol, or dimethyl maleate.

The compositions of the present invention can be prepared by homogeneously mixing components (a) to (E) using a suitable mixing apparatus, such as a spatula, a drum roll, a mechanical stirrer, a three-roll mill, a sigma blade mixer, a dough mixer, a planetary mixer, a screw, a dissolver, a butterfly mixer, an extrusion mixer, or a vacuum mixer. The order in which components (a) - (E) are mixed is not critical, however, it is preferred that certain components may be mixed to form two or more packages that can be stored, if desired, and then mixed in a final step immediately before they are to be used.

Preferably, component (C) and a portion of components (a), (D) and (E) are mixed to provide a first package. Separately, components (a), (B), (D), (E) are mixed to provide a second package. The two packages may then be stored and then mixed homogeneously prior to use. Other combinations are also possible, but it is important to keep component (B) and component (C) separate.

The curable polyorganosiloxane composition used as a sealant according to the present invention preferably comprises:

100 parts by weight of component (A),

0.1 to 200 parts by weight of component (B), preferably 0.5 to 50 parts by weight,

from 0.5 to 1000, preferably from 1 to 100ppm, of component (C), based on the amount of transition metal and on the total amount of components (A) and (B),

0.01 to 5, preferably 0.1 to 5, more preferably 0.5 to 3 parts by weight of component (D),

0 to 50 parts by weight of component (E), preferably 0 to 40 parts by weight,

and optionally 0 to 15 parts by weight, preferably 0 to 6 parts by weight, of an adjuvant.

The amounts of components (a) and (B) are generally chosen in such a way that the molar ratio of the total amount of SiH groups in component (B) to the total amount of unsaturated hydrocarbyl residues in component (a) in the formulation is from 0.7 to 4, preferably from 0.7 to 2.4; more preferably 0.7 to 2.

Another particularly preferred embodiment of the present invention relates to a photoactivatable, curable polyorganosiloxane composition comprising:

(A) at least one polyorganosiloxane having at least two unsaturated hydrocarbyl residues,

(B) at least one polyorganohydrogensiloxane having at least 7 Si atoms, wherein the molar ratio of SiH groups to all Si atoms is greater than 0.35,

(C) at least one photo-activatable catalyst,

(D) optionally at least one tackifier selected from:

(D1) at least one organosiloxane comprising at least one alkoxysilyl group; and

(D3) at least one aromatic organic compound having at least two aromatic moieties and at least one group reactive in hydrosilylation;

(E) optionally at least one reinforcing filler.

The same definitions as explained above are used for this new composition, except that component (C), i.e. the hydrosilylation catalyst, is selected from a photoactivatable catalyst or a photoactivatable catalyst (synonymously for both terms), which is explained in detail above.

Such photoactivatable compositions are particularly preferred because they do not require thermal curing at high temperatures, thereby reducing thermal stress on solar cell modules, particularly photovoltaic modules. In addition, these compositions can be cured "on command" without shelf or shelf life time.

The addition-curable sealant of the present invention can be applied to the surface of the associated substrate of the solar module by any suitable means such as roll coating, spreading, spraying, calendering, and the like, and cured at a suitable temperature. The curing temperature and time required will depend on the particular choice of catalyst and inhibitor system.

The addition-curable sealant composition of the present invention comprising components (a) to (E) and an adjuvant at 25 ℃ and D =10 s^-1Preferably from 200 to 100000 mpa.s, preferably from 2500 to 80000 mpa.s, most preferably from 10500 to 70000 mpa.s.

Preferably, the sealant is cured at 50 to 120 ℃ for a time of 5 to 30 minutes. Other embodiments include the use of photoactivatable curable polyorganosiloxane compositions utilizing photoactivatable catalysts or initiators. Curing is then initiated by irradiation with light, in particular ultraviolet light having a maximum wavelength of 300 to 550 nm. Radiation curing is preferably carried out at room temperature (25 ℃).

Preferably, the sealant is applied at a dry thickness of about 150 to 2000 μm, more preferably about 200 to 600 μm.

The cured sealant of the present invention preferably has a transparency of greater than 80%, more preferably greater than 90% transmission, as measured photometrically at a wavelength of 400 nm at a thickness of 2 mm.

Many designs for photovoltaic modules have been published.

A typical solar cell module of the present invention may consist of: a front glass cover layer, a semiconductor cell (wafer or film), conductive traces, a substrate or backing layer, and a sealant that can partially or completely seal the semiconductor cell. Sealing does not necessarily mean a fixed contact between the silicone sealant and the semiconductor cell, as long as it fulfills the function of protecting the semiconductor cell. Preferably, the solar cell module of the present invention does not contain an EVA sheet between the glass cover layer and the semiconductor cell.

In addition, the solar cell module of the present invention may include a support frame, which is preferably made of metal (e.g., aluminum).

In a preferred embodiment of the invention, the cured silicone sealant forms together with the glass cover layer an enclosed space containing the semiconductor cell. This embodiment may include the case where the semiconductor cell is completely embedded in the cured silicone sealant in contact with the glass cover layer, or the case where the cured silicone sealant and the glass cover layer (including the semiconductor cell) form a void. In another preferred embodiment, the voids formed by the cured silicone sealant and the glass cover layer do not contain any other material than the semiconductor cells and the conductive traces.

In another preferred embodiment, the solar cell module of the invention has an outer backing layer, which preferably has a high glass transition temperature, for example greater than 120 ℃. Backing layer the backing layer substrate is a rigid or stiff backing layer to provide protection to the rear surface of the module. A wide variety of materials have been proposed for such substrates, which do not necessarily need to be light transmissive. They include the following materials: for example, an organic fluoropolymer such as ethylene-tetrafluoroethylene (ETFE), Tedlar, or polyethylene terephthalate (PET), PVDF (polyvinylidene fluoride), PVF (polyvinyl fluoride), a multilayer material such as PVF-PET-PVF, or EVA copolymer (although not preferred due to lower resistance to degradation) either alone or coated with a silicon and oxygen-based material (SiOx).

The outer backing layer previously described is preferably in contact with the cured silicone sealant of the present invention. As explained above, the cured silicone sealant provides excellent and durable adhesion to both the glass cover layer and the backing layer of the solar cell module, particularly to the fluorothermoplastic sheet as the backing layer.

The curable polyorganosiloxane composition is preferably used as a sealant in contact with glass.

The invention also relates to a method for manufacturing a photovoltaic solar cell module, comprising the steps of: the method comprises the steps of applying a curable polyorganosiloxane composition to at least one substrate comprised by the photovoltaic solar cell module, and curing the polyorganosiloxane composition so as to provide a seal to such substrate of the photovoltaic solar cell module. Preferably, the polyorganosiloxane composition is applied between a glass cover layer of a photovoltaic solar cell module and a semiconductor cell so as to fill a gap between the glass cover layer and the semiconductor cell. The surface of the semiconductor cell carries the semiconductor material (in particular silicon) and optionally the lead, so that in this embodiment the encapsulant is in direct contact with the semiconductor material (in particular silicon) and optionally the lead and the glass cover layer.

The semiconductor cells of the photovoltaic solar cell module may have wires directed toward the light receiving side and/or the opposite side.

The present invention encompasses preferred embodiments in which the encapsulant covers only the back side (meaning the side opposite the light-receiving side) of the semiconductor cells of the photovoltaic solar cell module. This embodiment includes the possibility that the sealant is connected to the glass cover layer, so that a gap is formed between the semiconductor cell and the glass cover layer.

The invention also encompasses preferred embodiments in which the encapsulant completely covers the semiconductor cells of the photovoltaic solar module. Also this embodiment comprises the possibility that the sealant is connected to the glass cover layer, thereby forming an interlocking layer between the glass cover layer and the semiconductor cell.

The method of manufacturing a solar cell module of the present invention may be carried out continuously or discontinuously (in batches), preferably continuously.

Types of glass used to make solar cell glass overlays and particularly useful for adhering the cured silicone sealant of the invention include rolled glass, float glass. Because these types of glass used in solar cell manufacturing typically have inorganic or organic protective coatings, the cured silicone sealant of the present invention also requires excellent adhesion properties to such protective coatings. The protective glass coating may include: inorganic protective coatings, such as metal oxide coatings, e.g., silica-based coatings, titania-based coatings; an organic protective coating, such as a fluororesin coating. The special function of the glass protective coating is to prevent the exudation which makes the glass cloudy or opaque.

The present invention is explained in more detail in the following examples.

Examples

Test program

Test procedure for adhesion on glass

The test method substantially followed ASTM C794-06. If not otherwise indicated, a standard 50mm x 150 mm float glass plate having a thickness of 2 mm was used for the adhesion test. The glass plates were washed with 2-propanol and air dried. Samples were prepared using a micro-sieve wire grid (Rocholl GmbH; 25 mm wide and 300 mm long; wire thickness: 0.5 mm; screen width 1 mm. times.1 mm).

The procedure is as follows: the glass plate was coated with a silicone sealant to a thickness of 4 mm. The grid is pressed into the coating and a second layer of silicone sealant is coated on top. The grids overlap on one side. The silicone sealant outside the grid was wiped off. The sample was placed in an oven preheated to 90 ℃ for 10 minutes. The samples were stored at ambient conditions for at least 12 hours and then tested. For adhesion testing, silicone was cut by a scalpel 2 to 3 mm deep from the glass on the side of the specimen where the grids overlapped. The test specimen was held vertically in a tensile testing machine. The free end of the grid is clamped in a suitable clamp of the load cell. The grid was pulled at 50 mm/min to make a 180 ° angle with the glass plate.

In the case of pure cohesive failure in the silicone, the adhesion was rated positive. In the case of initial adhesion, the test specimens were subjected to accelerated ageing and retested after different time intervals. To accelerate aging under heat and moisture, the test specimens were placed in a climate chamber at 85 ℃ and 85% relative humidity. The adhesion test described above was repeated after 1000 hours. If not otherwise mentioned, three samples were tested for each material.

Test procedure for adhesion on plastics

Will Tedlar^®The foil is used as a representative example of a plastic backing layer for a solar module. Test specimens were prepared and tested similarly as described above for glass. The metal grid is replaced by a foil. The glass plate was coated with a silicone sealant to a thickness of 4 mm and the foil was then pressed well onto the coating. The silicone paste on the outside of the foil was wiped off. For the accelerated aging test, the specimens were subjected to 85 ℃ and 85% relative humidity for 1000 hours.

Preparation of the sealant

The sealant was prepared in a plastic beaker with a kitchen mixer. The filler batch is carefully diluted with a polyorganosiloxane having at least two alkenyl groups, followed by the addition of other ingredients. The mixture was degassed under vacuum prior to use.

Filler batch (F1) Preparation of

The filler batch (F1) was made as follows: 22.5 kg of vinyl-terminated linear polydimethylsiloxane having a viscosity of 10Pa.s at 25 ℃ were placed in a planetary mixer and mixed with 2.8 kg of hexamethyldisilazane and 0.9 kg of water. The BET surface area is 300 m²12.0kg of pyrogenic silica per g are added gradually and mixed until a hard mixture is obtained. The mixture was stirred and heated to reflux for 30 minutes. The volatiles were distilled off and then pulled under vacuum for 30 minutes. The mixture was diluted with 7.8kg of the above polydimethylsiloxane. The resulting filler batch, when used to prepare the following sealants, was calculated as 71.7% vinyl-terminated polymer having 28.3% silica and a viscosity of 10 pa.s.

Examples 1 : sealants with different crosslinkers

52 g of the filler batch (F1) were mixed with the various crosslinker components (B) in the amounts (g) listed in% in Table 1, 0.12 g of a Karstedt-type platinum solution with 1% platinum, 10.5. mu.l of the inhibitor ethynylcyclohexanol- (1) (ECH), and the mixture was subsequently brought to 100 g with approximately 46.5 to 47.5g of vinyl-terminated linear polydimethylsiloxane having a viscosity of 10 Pa.s.

All examples 1.1-1.4 contained about 14.7 wt% filler, 12 ppm platinum and 100ppm inhibitor ECH. The material had a liquid to pasty, slightly sagging consistency.

Comparative examples

Comparative examples 1.3 and 1.4 demonstrate that linear cross-linkers outside the inventive SiH ratio range do not adhere to glass, even under initial stage test conditions, whereas examples 1.1 and 1.2 adhere well in the fresh state and even after accelerated aging for 1000 hours at 85 ℃ and 85% relative humidity. The sealants 1.1 and 1.2 were also tested on Tedlar @ foil (PVF) and failed to adhere after 1000 hours at 85 ℃ and 85% relative humidity. This observation indicates that compositions without other tackifiers do not adhere as completely to both glass and plastic, such as PVF, of the backing layer as desired.

Examples 2 : with different crosslinking agents and adhesion promoters (D1) Sealing agent of

The composition used an additional silicone adhesion promoter (D1) in this example, which was methacryloxypropyltrimethoxysilane and D in a 1:1 molar ratio according to formula (3c) in this example^H ₃Addition products of D.

52 g of the filler batch (F1) were mixed with the various crosslinker components (B) in the amounts (g) listed in% in Table 2, 0.12 g of a Karstedt-type platinum solution with 1% platinum, 10.5. mu.l of the inhibitor ethynylcyclohexanol- (1) (ECH), 0.7 g of tackifier (D1) and the mixture was subsequently brought to 100 g with approximately 44.7-46.8 g of vinyl-terminated linear polydimethylsiloxane having a viscosity of 10 Pa.s.

All examples 2.1 to 2.10 contained about 14.7% by weight of filler, 12 ppm of platinum and 100ppm of inhibitor ECH and 0,7 g of tackifier (D1). The material had a liquid to pasty, slightly sagging consistency.

Comparative examples

Comparative examples 2.7 to 2.10, in which the crosslinker structure is outside the scope of the invention but with tackified siloxanes (D1), adhere well to the glass in the initial state. However, all samples failed after 1000 hours at 85 ℃ and 85% humidity, but the samples of examples 2.7-2.10 were maintained at 85 ℃ and 85% relative humidity for 250 hours.

The samples of examples 2.1 to 2.6 comprising component (B) as defined according to the invention passed the test at 85 ℃ and 85% relative humidity for 1000 hours without adhesive failure in the peel adhesion test.

In addition, the adhesion to Tedlar ® foil (PVF) was tested with example 2.6. The sealant adhered in initial testing and maintained at 85 ℃ and 85% relative humidity for 1000 hours without any loss of adhesion to the foil.

Examples 3 : sealants with different crosslinkers and tackifiers

In example 3, the adhesion promoter component (D2), the siloxane of example 2, and the silane are combined as component (D2):

mom = methacryloxypropyltrimethoxysilane, CH₂=C(CH₃)COO(CH₂)₃Si(OCH₃)₃

Glymo = glycidoxypropyltrimethoxysilane, (C)₂H₃O)CH₂O(CH₂)₃Si(OCH₃)₃

Sealants were prepared as described in examples 1 and 2, including approximately 14.7% filler, vinyl terminated polysiloxane having a viscosity of 10pa.s, 12 ppm platinum, 100ppm ECH and amounts of crosslinker and adhesion promoter as listed in table 3.

Comparative examples

Examples 3.1 to 3.4 show sufficient adhesion under 1000 hours of test conditions if 2 or 1 (i.e. if at least (D2) tackifier is present), whereas, for example, example 3.5 with component (B) having a SiH molar ratio of less than 0.5 shows insufficient adhesion at 85 ℃ and 85% humidity for 1000 hours.

Example 3.4 also shows, for example, a duration of 1000 hours for Tedlar^®Good adhesion of the foil, i.e. polyvinyl fluoride (PVF DuPont). The sealant adhered in an initial test and did not lose any adhesion to the PVF-foil over 1000 hours at 85 ℃ and 85% relative humidity.

Examples 4 : sealant with photo-activatable metal catalyst

52 g of vinyl-terminated polydimethylsiloxane polymer having a viscosity of 10Pa.s at 25 ℃ were mixed as component (A) with 29 g of hexamethyldisilazane-treated Aerosil 300 obtained according to the preparation method of the filler batch (F1). Then 16.7 g of vinyl terminated polydimethylsiloxane having a viscosity of 10Pa.s was further added to the resulting mixture. 0.9 g Dynasilan GLYMO (glycidoxypropyltrimethoxysilane), 0.25 g Dynasilan MEMO (methacryloxypropyltrimethoxysilane) as component (D2), 1 g according to formula 3c were subsequently addedTackifier (D1), 0.9 g of trimethylsilyl-terminated poly (co-diphenyl-methylhydrodimethylsiloxane) M as component (B)₂D^Ph ₂D^H ₂₅D₄. In a sealed dark glove box under red or yellow light (excluding at least blue and uv light) of a bulb lamp, 10 g of such a component mixed light activatable metal catalyst, which is trimethyl (methyl-cyclopentadienyl) -platinum (IV) dissolved in 1 pa.s of vinyl terminated polydimethylsiloxane at 25 ℃, was used to form a platinum concentration of 24ppm Pt in the total composition of this example. D in component (B)^HThe unit to total Si unit ratio was 0.76, in this example the SiH to Si-vinyl ratio was 1.9.

Adopts a UV lamp Panacol UV-H255 type LH365E 250W 320-405 nm as a light source and 120mW/cm²( = 1200 mJ/cm²) And a distance of 5 cm, the composition was irradiated for 10 seconds.

The cured composition adheres with a peel force of 10-12N/mm and cohesive failure to sheets of PVC (polyvinyl chloride), PA 6.6 (polyamide), PBT (polybutylene terephthalate) occurs after storage for 7 days at 25 ℃.

After storage at 25 ℃ for 90 minutes, the cured composition adhered to the glass with a peel force of 8N/mm.

The peel force was measured by the above test method (ASTM C794-06).

Example 4 demonstrates that photoactivatable compositions using a tackifier (D1) also adhere to various substrates.

Claims (11)

1. A method of making a photovoltaic solar cell module, the method comprising the steps of: applying a curable polyorganosiloxane composition to at least one substrate comprised by a photovoltaic solar cell module and curing said curable polyorganosiloxane composition so as to provide a seal to such substrate of the photovoltaic solar cell module, wherein said curable polyorganosiloxane composition comprises:

(A) at least one polyorganosiloxane with at least two unsaturated hydrocarbon residues, consisting of a linear polyorganosiloxane (A1) containing not more than 0.2 mol.% of siloxy units of the T or Q type,

(B) at least one polyorganohydrogensiloxane having at least 7 Si atoms, wherein the molar ratio of SiH groups to all Si atoms is greater than 0.55,

(C) at least one hydrosilylation catalyst,

(D) at least one tackifier, wherein component (D) is selected from at least one of: (D1) the method comprises the following steps At least one organosiloxane comprising at least one alkoxysilyl group; (D2) the method comprises the following steps At least one organosilane comprising at least one alkoxysilyl group; (D3) the method comprises the following steps At least one aromatic organic compound having at least two aromatic moieties and at least one group reactive in hydrosilylation,

(E) optionally at least one reinforcing filler,

wherein the molar ratio of the total amount of SiH groups in component (B) to the total amount of unsaturated hydrocarbyl residues in component (A) in the formulation is between 0.7 and 4.

2. The method of claim 1, wherein component (a) is a compound of formula (1):

R¹ _aR_3-aSiO[R₂SiO]_m[R¹RSiO]_nSiR¹ _aR_3-a(1)

r is selected from the group consisting of optionally substituted alkyl having up to 30 carbon atoms, optionally substituted aryl having up to 30 carbon atoms, poly (C) having up to 1000 alkyleneoxy units₂-C₄) Alkylene ethers, the R groups being free from aliphatic unsaturation,

R¹selected from aliphatic or aromatic groups having up to 30 carbon atoms, comprising a C ═ C group-containing group (alkenyl) or a C ≡ C group-containing group (alkynyl), optionally containing one or more O or F atoms,

a is 0 to 3

m is 0 to 2000

n is 0 to 500.

3. The process according to any one of the preceding claims, wherein component (B) is a compound of formula (2 a):

H_a(R)_3-aSi[RHSiO]_x[R₂SiO]_y[RR¹SiO]_zSi(R)_3-aH_a(2a)

r, R therein¹A is as defined above, a is,

7≤x+y+z<1000。

4. the process according to claim 1 or 2, wherein component (C) is at least one transition metal compound, wherein the transition metal is selected from the group consisting of nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum.

5. The method of claim 1 or 2, wherein component (D1) is an organosiloxane comprising at least one unit selected from the group consisting of:

RHSiO_2/2and

R⁵(R)SiO_2/2，

wherein R is as defined above and may be the same or different, R⁵Selected from the group consisting of unsaturated aliphatic groups having up to 14 carbon atoms, epoxy-containing aliphatic groups having up to 14 carbon atoms, cyanurate-containing groups, and isocyanurate-containing groups,

and further comprising at least one unit of formula (3):

O₂/₂(R)Si-R⁴-SiR_d(OR³)_3-d(3)

wherein

R is as defined above and may be the same or different,

R³selected from H (hydrogen) and alkyl groups having 1 to 6 carbon atoms, and may be the same or different,

R⁴is a difunctional, optionally substituted hydrocarbon radical having up to 15 carbon atoms, which may contain one or more heteroatoms selected from O, N and S atoms, and which is bonded to the silicon atom by an Si — C bond, and d is from 0 to 2.

6. The process according to claim 1 or 2, wherein component (D2) is selected from compounds of the formula:

X-(CR⁶ ₂)_e-Y-(CH₂)_eSiR_d(OR³)_3-d

wherein

X is selected from the group consisting of halogen, pseudohalogen, unsaturated aliphatic groups having up to 14 carbon atoms, epoxy-containing aliphatic groups having up to 14 carbon atoms, cyanurate-containing groups, and isocyanurate-containing groups,

y is selected from single bond, heteroatom group selected from-O-, -S-, -CONH-, -HN-CO-NH-,

R⁶selected from hydrogen and R as defined above,

e is 0, 1, 2, 3,4, 5, 6,7, or 8, and may be the same or different,

r is as defined above and may be the same or different,

R³as defined above and may be the same or different,

d is as defined above and may be the same or different.

7. The process according to claim 1 or 2, wherein component (D3) is selected from compounds of the formula:

wherein

r is a number of 0 or 1,

R⁷which may be the same or different, are selected from the group consisting of a hydrogen atom, a hydroxyl group, a halogen atom, an alkyl group, an alkenyl group, an alkoxy group, an alkenyloxy group, an alkenylcarbonyloxy group and an aryl group, and

formula-E_f-Si(OR)_3-dR_dWherein R are the same or different and d is as defined above,

of the formula-O-Si (R)₂R¹Wherein R and R¹As defined above, in the above-mentioned manner,

formula-E_f-Si(R)₂A group of H, wherein R is as defined above,

wherein E is a divalent organic radical having up to 8 carbon atoms and from 0 to 3 heteroatom radicals selected from the group consisting of-O-, -NH-, C ═ O, and-C (═ O) O-, and

f is 0 or 1, and f is,

and Z is selected from the following groups:

wherein R is⁸Selected from the group consisting of hydrogen atoms, halogen atoms, substituted or unsubstituted alkyl, aryl, alkenyl and alkynyl groups, and g is a positive number of at least 2, wherein R is selected from the group consisting of⁷And R⁸At least one of said groups of (a) is reactive in hydrosilylation.

8. The process according to claim 1 or 2, wherein component (E) is selected from the group consisting of BET surfaces of at least 150m²Silica per gram.

9. The method of claim 1 or 2, the curable polyorganosiloxane composition comprising:

100 parts by weight of component (A),

0.1 to 200 parts by weight of component (B),

0.5 to 1000ppm, based on the amount of transition metal and based on the sum of components (A) and (B), of component (C),

0.01 to 5 parts by weight of component (D),

0 to 50 parts by weight of component (E).

10. The method of claim 1 or 2, wherein the curable polyorganosiloxane is a photo-activatable, curable polyorganosiloxane composition.

11. A photovoltaic solar cell module comprising a front glass cover layer, a semiconductor cell comprising a semiconductor material, electrically conductive tracks, a backing layer and a sealant which can partially or completely seal the semiconductor cell, the sealant being obtained by curing a polyorganosiloxane composition as defined in claim 1.