Glass-containing thermoplastic acrylic resin composition and molded article thereof

Abstract

A thermoplastic acrylic resin composition is provided in which translucency properties are suitable for use as a top-sheet member of a photovoltaic cell, warping caused by temperature change is suppressed, and its weathering resistance is excellent; 0.1 to 50 parts by mass of a glass is contained in 100 parts by mass of the thermoplastic acrylic resin; an absolute value of a difference in refractive indices of the thermoplastic acrylic resin and the glass is 0.08 or lower; an average particle size of the glass is 100 to 2,000 μm; a softening temperature of the thermoplastic resin is 80° C. or higher; and the aspect ratio of the glass is 15 or greater. Also, a molded article which is obtained by molding the thermoplastic acrylic resin composition and has a YI value of 20 or lower after weathering-resistance testing. Further, a top-sheet member of a photovoltaic cell is made of the molded article.

Claims

1. A thermoplastic acrylic resin composition, comprising: a thermoplastic acrylic resin (A); and a glass (B), wherein the thermoplastic acrylic resin (A) containing 10 to 100% by mass of a methyl methacrylate unit, the mass-average molecular weight of thermoplastic acrylic resin (A) measured using GPC is 50,000 to 200,000, 0.1 to 50 parts by mass of the glass (B) are contained in 100 parts by mass of the thermoplastic acrylic resin (A), an absolute value of a difference of refractive indices of the thermoplastic acrylic resin (A) and the glass (B) is 0.08 or lower, an average particle size of the glass (B) is 100 to 2,000 μm, the glass (B) is a flake-type glass with an aspect ratio of 15 or greater, and a softening temperature of the thermoplastic acrylic resin composition measured by ASTM D648 is 80° C. or higher.

2. A molded article obtained by molding the thermoplastic acrylic resin composition according to claim 1.

Description

EXAMPLES

(1) In the following, the present invention is described in detail by examples. However, the present invention is not limited to such examples.

(2) “Parts” and “%” in examples mean “parts by mass” and “% by mass” respectively.

(3) (a) Total Light Transmission

(4) A haze meter (NDH 2000, made by Nippon Denshoku Industries, Co., Ltd.) with use of D65 light source was used to measure total light transmission (Tt) of test sheets before and after weathering-resistance tests. (Tt) is used as the index of translucency characteristics in the present embodiment.

(5) (b) Refractive Index

(6) An Abbe refractometer (DR-A1, made by Atago Co., Ltd.) and sodium D lines were used to measure a refractive index of thermoplastic acrylic resin (A).

(7) (c) Measuring Average Particle Size

(8) The average particle size (number-average particle size) of glass filler (B) was measured as follows: a solution was prepared by dispersing 10 mg of glass flakes in 5 mL of water, particle diameters were measured using a particle size analyzer (LA-910, made by Horiba, Ltd.), and the number-average value was calculated.

(9) (d) Measuring Average Thickness

(10) A digital microscope, KH-3000, made by Hirox, Inc. was used to obtain the average thickness of glass filler (B) by measuring thicknesses of 30 units of glass filler (B) and by calculating the simple average.

(11) (e) Light Resistance

(12) Using a metal weather tester, made by Daypla Wintes Co., Ltd. (model: KW-R5TP-A, light source: a water-cooled metal halide lamp), irradiation tests were conducted on test sheets prepared above using a filter KF-1 (wavelength of transmitted light 295 to 780 nm) under conditions of irradiance at 140 mW/cm.sup.2, black panel temperature of 63° C., and spraying with water.

(13) (f) YI Value (Yellow Index)

(14) Based on JIS-K7105, the YI values of test sheets above were measured before and after weathering-resistance testing.

(15) (g) Measuring Softening Temperature (HDT)

(16) Using thermoplastic acrylic resin compositions obtained in their respective examples or comparative examples, test sheets (1 cm×8 cm×4 mm-thick) were produced through injection molding, and annealed at 80° C. for 24 hours. Then, their heat distortion temperatures were determined under a low load (4.6 kg/cm.sup.2) based on ASTM D648.

(17) (h) Warping in Photovoltaic Module

(18) On a hot plate of a photovoltaic module laminator (LM-50X50-S, made by NPC Inc.), the following were laminated in this order: a molded article obtained in each example or comparative example, 150 mm×150 mm of encapsulant (EVA, 0.45 mm thick, made by C.I. Kasei Co., Ltd.), single photovoltaic cells connected in series (5 inches, polycrystalline silicon photovoltaic cells, made by Asuden Co., Ltd.), and 150 mm×150 mm of encapsulant (EVA, 0.45 mm thick, made by C.I. Kasei Co., Ltd.), and 150 mm×150 mm of a lower-surface protective member. Then, the laminate was sandwiched by 500 mm×500 mm template film, and vacuum-pressed under conditions of vacuum atmosphere, 135 degrees, 15 minutes and pressure of 101.3 kPa. Accordingly, photovoltaic modules were obtained. Warping in each module was visually observed and evaluated as follows:

(19) A: no warping observed in produced photovoltaic module

(20) B: warping observed in produced photovoltaic module

Example 1

(21) Ten parts of glass (B) (brand name “RCF-600” made by Nippon Sheet Glass Co., Ltd., refractive index of 1.520, average particle size of 437 μm, aspect ratio of 67) are added to 100 parts of poly(methyl methacrylate) resin (brand name “VHK” made by Mitsubishi Rayon Co., Ltd., mass-average molecular weight of 95,000, monomer unit composition: methyl methacrylate 99%, methyl acrylate 1%) as thermoplastic acrylic resin (A), and dry-blended.

(22) Next, using a single-screw extruder (30 mm φ single-screw extruder, made by TPIC Co., Ltd.) the resin is melt-kneaded at 250° C. and the extruded strands are cut into pellets. Accordingly, a thermoplastic acrylic resin composition is obtained.

(23) The above thermoplastic acrylic resin composition was molded using an injection molding machine (brand name “IS100EN,” made by Toshiba Machine Engineering Co., Ltd.) to obtain a 3 cm×3 cm×2 mm-thick sheet. The sheet was used as a test sheet. The evaluation results are shown in Table 1.

(24) The refractive index, average particle size and aspect ratio of glass are shown in Table 1.

Examples 2-7, Comparative Examples 1-4

(25) In the same manner described in example 1 except that the type of thermoplastic acrylic resin (A) and the type and amount of glass (B) were changed as shown in Table 1, molded articles were obtained respectively.

(26) Resins:

(27) BR-52: poly(methyl methacrylate/styrene) copolymer resin (brand name “BR-52” made by Mitsubishi Rayon Co., Ltd., mass-average molecular weight of 65,000, monomer unit composition: methyl methacrylate 75%, styrene 25%)

(28) PS: polystyrene resin (brand name “Toyo Styrene GP G200C,” made by Toyo Styrene Co., Ltd.)

(29) PC: polycarbonate resin (brand name “Panlite L-1225 WS,” made by Teijin Ltd.)

(30) Glass (B):

(31) glass flakes (brand name “RCF-2300,” made by Nippon Sheet Glass Co., Ltd.)

(32) glass flakes (brand name “RCF-I6Q,” made by Nippon Sheet Glass Co., Ltd.)

(33) glass flakes (brand name “RCF-15,” made by Nippon Sheet Glass Co., Ltd.)

(34) glass (hikes (brand name “REF-15,” made by Nippon Sheet Glass Co., Ltd.)

(35) The refractive indices, average particle sizes and aspect ratios of glass flakes are shown in Table 1.

(36) TABLE-US-00001 TABLE 1 differ- ence in resin/ before after before after glass weather weather weather weather warping resin glass flake flakes resis- resis- resis- resis- in refrac- refrac- refrac- tance tance tance tance photo- tive tive particle aspect tive test test test test HDT voltaic type index [part] type index size ratio [part] index Tt (%) Tt (%) YI YI (° C.) module Example 1 VHK 1.492 100 RCF-600 1.52 437 67 10 0.028 89 87 1.4 2.5 91 A Example 2 VHK 1.492 100 RCF-2300 1.52 192 45 10 0.028 91 89 0.9 2.4 95 A Example 3 VHK 1.492 100 RCF-160 1.52 356 76 10 0.028 92 90 0.8 2.2 93 A Example 4 VHK 1.492 100 RCF-600 1.52 437 67 40 0.028 87 81 1.9 4 102 A Example 5 VHK 1.492 100 RCF-2300 1.52 192 45 40 0.028 82 78 2.5 5.4 103 A Example 6 VHK 1.492 100 RCF-160 1.52 356 76 40 0.028 87 79 1.6 3.7 103 A Example 7 BR-52 1.514 100 RCF-600 1.52 437 67 10 0.006 90 86 1.6 3.5 83 A Compar- VHK 1.492 100 RCF-15 1.52 57 13 40 0.028 60 59 7.4 11.4 99 A ative Example 1 Compar- VHK 1.492 100 RCF-15 1.56 57 13 10 0.068 64 61 8.5 8.3 95 A ative Example 2 Compar- PS 1.594 100 RCF-600 1.52 437 67 10 0.074 86 65 5.3 27.4 73 B ative Example 3 Compar- PC 1.582 100 RCF-600 1.52 437 67 10 0.062 82 77 7.5 31.7 142 A ative Example 4

(37) As shown in Table 1, in molded articles using thermoplastic acrylic resin compositions according to an embodiment of the present invention, it is found that translucency characteristics are excellent (higher (Tt)), softening temperature (HDT) is high at 80° C. or higher, hardly any warping occurs when photovoltaic modules are formed, and weathering resistance is excellent (examples 1 to 7).

(38) Molded articles, formed using glass (B) with a smaller average particle size and a thermoplastic acrylic resin composition different from those in the above embodiment of the present invention, have lower translucency characteristics (comparative examples 1 and 2).

(39) Since the thermoplastic acrylic resin composition of comparative example 3 has a low softening temperature (HDT) at lower than 80° C., warping occurred when a photovoltaic module was produced. Also, notable deterioration in optical characteristics was observed after weathering-resistance testing.

(40) Since no thermoplastic acrylic resin was used in comparative example 4, its durability was low, with notable deterioration in optical characteristics observed after weathering-resistance testing.

INDUSTRIAL APPLICABILITY

(41) A thermoplastic acrylic resin composition according to an embodiment of the present invention has excellent translucency characteristics and weathering resistance, and suppresses warping caused by temperature change. In addition, a molded article according to the embodiment of the present, invention is suitable for use as a top-sheet member of a photovoltaic cell since it has excellent translucency characteristics and weathering resistance, and warping caused by temperature change is less likely to occur.