Transparent and highly tough acrylic polymer materials containing metal salts and ethylene vinyl alcohol copolymers

Abstract

To provide a polymer material that retains transparency and has improved toughness.SOLUTION: A polymer material contains polymethyl methacrylate, an ethylene vinyl alcohol copolymer, and a metal salt. The composition ratio of [polymethyl methacrylate: ethylene vinyl alcohol copolymer: metal salt] is preferably 80-92 wt.%: 4-10 wt.%: 4-10 wt.%.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention adds ethylene vinyl alcohol resin and metal salt to polymethyl methacrylate (acrylic) resin, which is used for window materials for automobiles and the like, thereby improving the toughness while increasing transparency. [Background technology]

[0002] Acrylic is widely used as a general-purpose resin because of its excellent transparency and surface hardness. However, it has the disadvantage of being brittle and having a small breaking strain, so soft rubber particles are added to brittle materials such as acrylic and polystyrene to improve their impact resistance and toughness.

[0003] Patent Document 1 discloses a methacrylic resin containing 50 to 97 mass% methacrylic acid ester monomer units, 3 to 30 mass% structural units having a ring structure in the main chain, and 0 to 20 mass% other vinyl monomer units copolymerizable with the methacrylic acid ester monomers, but does not mention the addition of a lithium salt. Non-Patent Document 1 describes the compatibility when acrylic and ethylene-vinyl alcohol copolymer are mixed, but the compatibility is low, and there is no report on making the mixture transparent by adding a metal salt. Non-Patent Document 2 describes the compatibility when acrylic and ethylene-vinyl alcohol copolymer are mixed in various compositions, but the ethylene content of the ethylene-vinyl alcohol copolymer is 21%, and there is no report on making the material transparent by adding a metal salt.

[0004] However, adding soft rubber particles to improve impact resistance and toughness reduces transparency, making it ineffective for applications that require transparency (optical displays and automotive glass). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Application No. 2017-179354 [Non-patent literature]

[0006] [Non-Patent Document 1] de Lima, Juliana Aristeia, and Maria Isabel Felisberti. "Poly (ethylene-co-vinyl alcohol) and poly (methyl methacrylate) blends: phase behavior and morphology." European polymer journal 44 (2008): 1140-1148. [Non-Patent Document 2] Michael M. Coleman, Xiaoming Yang, Hongxi Zhang, and Paul C. Painter. “Ethylene-co-vinylalcohol blends”, Journal of Macromolecular Science, Part B: Physics, 32 (1993): 295-326, Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to solve the above-mentioned problems and to provide a polymer material which maintains transparency and improves toughness by compatibilizing acrylic and ethylene-vinyl alcohol copolymer through the addition of a specific lithium salt. [Means for solving the problem]

[0008] The present invention which solves the above problems is as follows. (1) A polymer material characterized by containing polymethyl methacrylate, an ethylene-vinyl alcohol copolymer, and a metal salt. "Polymethyl methacrylate" may be written as "PMMA" and "ethylene-vinyl alcohol copolymer" as "EVOH." (2) The polymer material according to (1), wherein the composition ratio of the polymethyl methacrylate:the ethylene-vinyl alcohol copolymer:the metal salt is 80-92 wt %:4-10 wt %:4-10 wt %. Unless otherwise specified, the composition ratios are raw material composition ratios. However, since each component does not volatilize, has low reactivity, and sample preparation (drying, compression molding) does not exceed 150°C, the raw material composition ratios can be considered as sample (product) composition ratios. (3) The polymer material according to (1) or (2), wherein the ethylene-vinyl alcohol copolymer has an ethylene content of 29 to 44 wt %. (4) The polymer material according to any one of (1) to (3), wherein the polymethyl methacrylate has a weight average molecular weight of 80,000 to 500,000. The weight average molecular weight of polymethyl methacrylate is more preferably 80,000 to 200,000. (5) The polymer material according to any one of (1) to (4), wherein the metal salt is a Li salt. Effect of the Invention

[0009] The lithium salt reduces the crystallinity of the ethylene-vinyl alcohol copolymer, thereby making it compatible with acrylic, and thus making it possible to provide a polymer material that maintains transparency and has improved toughness. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1A is a Venn diagram showing the effect of hydrogen bonding interaction by the addition of EVOH and the improvement in compatibility by the addition of a Li salt, and the relationship between the two, for one embodiment of the polymer material of the present invention; FIG. 1B is a diagram showing the effect of hydrogen bonding interaction by the addition of EVOH, using a specific chemical formula; and FIG. 1C is a diagram showing the improvement in compatibility by the addition of a Li salt, using a specific chemical formula. [Diagram 2](a) PMMA / EVOH29 (95 / 5 wt / wt), (b) (a) with 5 wt% LiTESI per (a), (c) (a) with 5 wt% LiClO4 per (a), (d) (a) with 5 wt% LiBr per (a), (e) PMMA / EVOH44 (95 / 5 wt / wt), (f) (e) with 5 wt% LiTESI per (a), (g) (e) with 5 wt% LiClO4 per (e), (h) (e) with 5 wt% LiBr per (e). [Diagram 3] FIG. 1 is a diagram showing the shape of a dumbbell test piece used in a tensile test. [Figure 4] FIG. 1 shows the stress-strain curves of PMMA, PMMA / EVOH, and PMMA / EVOH / Li(5). [Diagram 5] FIG. 1 shows the results of dynamic mechanical analysis (DMA) of PMMA, PMMA / EVOH, and PMMA / EVOH / Li(5). [Figure 6] FIG. 1 shows the results of differential scanning calorimetry (DSC) for EVOH, PMMA / EVOH, PMMA / EVOH / Li(1), PMMA / EVOH / Li(5), and PMMA. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be made without departing from the scope of the invention.

[0012] 1(a) shows a Venn diagram of the effect of hydrogen bonding interaction by adding EVOH and the improvement in compatibility by adding Li salt for one embodiment of the polymer material of the present invention. The present invention combines the intersecting portion of the two, that is, the effect of hydrogen bonding interaction and the improvement in compatibility by adding Li salt. In one embodiment of the polymer material, hydrogen bonding interaction is expressed by the interaction between the hydroxyl group of EVOH and the carbonyl group of PMMA by adding EVOH as shown in (b) of the same document, while improvement of compatibility is expressed by the bonding of oxygen atoms of adjacent carbonyl groups of different PMMA via Li cation by adding Li salt as shown in (c) of the same document.

[0013] (Example) <Transparency> Films (100 μm thick) were prepared using the compositions illustrated in Figures 2(a)-(h). These films were then placed on a piece of white paper with "Nagoya Institute of Technology" written in black on a white background, and their transparency was visually observed. For example, (a) was PMMA / EVOH29 (95 / 5wt / wt), that is, the composition ratio was 95wt% PMMA (Sigma-Aldrich Japan, Mw=120,000) and 5wt% EVOH29 (Mitsubishi Chemical, ethylene content=29mol%). Also, (b) was (a) with 5wt% LiTESI (lithium bis(trifluoromethane)sulfonylimide), that is, the composition ratio of LiTFSI was 4.76wt% (=5 / (100+5)). It was prepared by mixing PMMA, EVOH, and LiTFSI in hexafluoro-2-propanol (HFIP), followed by solution casting and compression molding to obtain a film.

[0014] In (c), LiClO4 (lithium perchlorate) was substituted for LiTFSI in (b), and in (d), LiBr (lithium bromide) was substituted for LiTFSI. lithium) was used. In (e), EVOH44 (Mitsubishi Chemical, ethylene content = 44 mol%) was used instead of EVOH29 in (a). And (g) and (h) were the same as (c) and (d). It was found that the addition of EVOH reduced the transparency of the film. The addition of LiTFSI improved the transparency of the film, and the transparency improved further as the amount added increased. Combined with the results in Table 2 below, it can be seen that the addition of LiTFSI reduced the transparency of the film. It was believed that this reduced the crystallinity of the film and improved its transparency.

[0015] <Visible light transmittance measurement> The visible light transmittance at wavelengths of 600 nm and 400 nm was measured for samples prepared using the films in Fig. 2(a)-(h), as well as for the sample prepared in Fig. 2(b) with 1 wt% LiTFSI (instrument: U-3310 spectrophotometer, Hitachi High-Technologies). The results of the light transmittance measurements are summarized in Table 1. Comparative Example 1 was a commercially available PMMA alone.

[0016] [Table 1]

[0017] From Table 1, the corresponding films are shown in FIG. 2(b) (Example 1), (d) (Example 2), and none ( Example 4 That is, in Example 1, the visible light transmittance was 88.4% (600 nm) and 86.1% (400 nm), in Example 2, the visible light transmittance was 68.0% (600 nm) and 64.6% (400 nm), in Example 3, the visible light transmittance was 58.7% (600 nm) and 53.6% (400 nm), Example 4 The visible light transmittance was 72.5% (600 nm) and 55.2% (400 nm), both of which exceeded 50% and were therefore practical values.

[0018] <Tensile test> Tensile tests were performed on PMMA, PMMA / EVOH, and PMMA / EVOH / Li (5) using a dumbbell tester with the shape shown in Figure 3, and the results are shown in Figure 4 as stress-strain curves for PMMA, PMMA / EVOH, and PMMA / EVOH / Li (5). PMMA / EVOH refers to PMMA / EVOH29 (95 / 5 wt / wt, Comparative Example 2), and PMMA / EVOH / Li (5) refers to PMMA / EVOH29 (95 / 5 wt / wt) + LiTFSI 5 wt% (Example 1). The measurement conditions for the tensile test were as follows: Apparatus: Tensile tester DAT100C (Abe Seisakusho Co., Ltd.), Tensile speed: 0.05 mm / sec, Atmosphere: Air, Measurement temperature: 28°C.

[0019] The following was learned from Figure 4. That is, the sample to which only EVOH29 was added (Comparative Example 2) showed some improvement in breaking strain and breaking stress compared to PMMA, but showed almost the same tensile properties as PMMA. On the other hand, the sample to which EVOH29 and LiTFSI were added (Example 1) showed a decrease in Young's modulus, the appearance of a yield point, and an improvement in breaking strain. From Table 2, it is believed that this result is due to the decrease in crystallinity by the addition of LiTFSI and the decrease in Young's modulus and the improvement in breaking strain due to hydrogen bonds between the carbonyl group and the hydroxyl group.

[0020] [Table 2]

[0021] The Young's modulus, breaking stress and breaking strain of PMMA, PC, PS and glass are shown in Table 3.

[0022] [Table 3]

[0023] <Dynamic Mechanical Analysis (DMA)> The dynamic viscoelasticity measurement was carried out using PMMA / EVOH etc. as described in the tensile test. The test pieces were cut to have dimensions of 40 mm x 5 mm x 0.1 mm, and measurements were performed in tension mode with a chuck distance of 10 mm to measure the temperature dependence of the storage modulus (E') and loss modulus (E"). The results of the dynamic viscoelasticity measurements shown in Figure 5 indicate that the addition of EVOH shifts the Tg to the lower temperature side. These results are also shown in Table 3. The measurement conditions for dynamic viscoelasticity measurement were as follows: Apparatus: DMS6100 (Seiko Instruments Inc.), Frequency: 0.1 Hz, Heating rate: 2°C / min, Temperature range: 30°C to 170°C, Atmosphere: Nitrogen

[0024] <Differential Scanning Calorimetry (DSC)> Differential scanning calorimetry was performed using the same method as the dynamic viscoelasticity measurement, and also using PMMA / EVOH / Li (1). The results of differential scanning calorimetry shown in Figure 6 indicate that the melting peak disappears due to the addition of Li, as shown in region 1 showing the melting peak. The measurement conditions for differential scanning calorimetry were as follows: Apparatus: differential scanning calorimeter (PerkinElmer Japan Co., Ltd.) Atmosphere: Nitrogen, and the measurement program was the following 1) to 5). 1) Heat from 30°C to 200°C at 20°C / min, 2) Hold at 200°C for 1 minute, 3) Cool from 200°C to 30°C at 20°C / min, 4) Hold at 30°C for 1 minute, 5) Heat from 30°C to 200°C at 20°C / min

[0025] The dynamic viscoelasticity measurement results, differential scanning calorimetry results, and EVOH thermal properties are summarized in Table 4. In the table, PMMA / EVOH29 / LiTFSI refers to PMMA / EVOH29(95 / 5wt / wt) / Li(5).

[0026] [Table 4]

[0027] From the results of differential scanning calorimetry, the melting temperatures of each component in the sample are as follows: PMMA is 111°C (=glass transition temperature), EVOH44 is 184°C (=crystalline melting temperature), and Li salt (LiTFSI) is none (non-crystalline). Therefore, if the temperature is 200°C or higher, all components will be in a molten state, and melt mixing is considered possible. This makes it possible to melt mix PMMA, EVOH, and Li salt without using a solvent (e.g. HFIP). [Industrial Applicability]

[0028] In this invention, we present a technology that adds a Li salt to a mixture of acrylic and EVOH to improve compatibility and transparency, while also significantly improving the brittleness of conventional acrylic. [Explanation of symbols]

[0029] 1: Melting peak region

Claims

1. A polymer material comprising polymethyl methacrylate, an ethylene-vinyl alcohol copolymer, and a lithium salt, the lithium salt being a lithium salt that reduces the crystallinity of the ethylene-vinyl alcohol copolymer, the lithium salt being bis(trifluoromethane)sulfonylimide.

2. 2. The polymer material according to claim 1, wherein the ethylene-vinyl alcohol copolymer has an ethylene content of 29 to 44 wt %.

3. 3. The polymer material according to claim 1, wherein the weight average molecular weight of the polymethyl methacrylate is 80,000 to 500,000.

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