Hideaki Hagihara

Alternating Copolymerization of Ethylene and 5‐Hexen‐1‐ol with [Ethylene(1‐indenyl)(9‐fluorenyl)]‐zirconium Dichloride/Methylaluminoxane as the Catalyst

The copolymerization of ethylene and 5-hexen-1-ol pretreated with trimethylaluminium was performed using [ethylene(1-indenyl)(9-fluorenyl)]zirconium dichloride/methylaluminoxane as the catalyst. The 5-hexen-1-ol unit in the the copolymer could be increased to about 50 mol-% with increasing [5-hexen-1-ol/ethylene] ratio. 13 C NMR analysis proved that the poly(ethylene-co-(5-hexen-1-ol)) containing 50 mol-% of 5-hexen-1-ol units is an almost alternating copolymer.

Additive effects of trialkylaluminum on propene polymerization with (t-BuNSiMe2Flu)TiMe2-based catalysts

Abstract Propene polymerization was conducted by [η3:η1-tert-butyl(dimethylfluorenylsilyl)amido]dimethyltitanium combined with B(C6F5)3 or methylaluminoxane (MAO) as a cocatalyst in the presence or absence of various trialkylaluminums: Me3Al, Et3Al, iBu3Al (triisobutylaluminum) and Oct3Al (trioctylaluminum). In the case of living polymerization with B(C6F5)3 at −50°C, addition of Oct3Al and Et3Al increased the propagation rate. Et3Al also acted as a chain transfer reagent and selectively gave Al-terminated polymers, while Oct3Al induced chain transfer reaction only in high concentration. Little polymer was obtained in the presence of Me3Al or iBu3Al. When MAO was used as a cocatalyst, polymerization did not proceed at −50°C. The MAO system, however, showed high activity at 40°C and selectively gave low molecular weight polymers terminated with Al–C bonds. Contrary to the low temperature polymerization with B(C6F5)3 at −50°C, the polymer yield was enhanced by the addition of Me3Al and iBu3Al, while the molecular weight was reduced by Me3Al and enlarged by iBu3Al. On the other hand, Et3Al and Oct3Al significantly decreased both the polymer yield and the molecular weight under these conditions. It was found that additive effects of trialkylaluminums were strongly dependent on polymerization temperature as well as on the structure of the alkyl group.

Polymerization of methyl methacrylate with non-bridged zirconocene catalysts

Four non-bridged dimethylzirconocene complexes. i.e., bis(η 5 -cyclopentadienyl )dimethylzirconium (1), (η 5 -cyclopentadienyl) (η-fluorenyl)dimethylzirconium (2), bis(η 3 -indenyl)dimethylzirconium (3) and (η 5 -cyclopentadienyl)(η 5 -pentamethylcyclopentadienyl)dimethylzirconium (4) were synthesized and used as a catalyst for the methyl methacrylate polymerization combined with triphenylmethyl tetrakis(pentafluorophenyl)borate in the presence of ZnEt 2 or Al(i-Bu) 3 . The catalyst activity strongly depends on the zirconocene compound and decreases in the order 2 > 1 >> 3 4. The polymerization proceeds in a living manner when 1 and 2 are used combined with ZnEt 2 . On the other hand, stereoregularities of the resulting polymers are independent of the zirconocene compound, and syndiotactic-rich polymers are formed by a chain-end controlled mechanism.

Stereospecificity of propene polymerization with achiral titanocene‐based catalysts

Propene polymerization was conducted with titanocene (Cp 2 TiMe 2 . Cp * 2 TiMe 2 ; Cp = η 5 -C 5 H 5 , Cp * = η 5 -C5Me5)/organoborane (B(C 6 F 5 ) 3 , Ph 3 CB(C 6 F 5 ) 4 ) catalysts at -50°C using toluene as a solvent. The polymer obtained with Cp 2 TiMe 2 /Ph 3 CB(C 6 F 5 ) 4 is less isotactic than that obtained with Cp 2 TiMe 2 /B(C 6 F 5 ) 3 . However, the isospecificity of the former catalyst is improved with respect to that of the latter one when a toluene/CH 2 Cl 2 mixture is used as a solvent instead of toluene. As similar enhancement in isospecificity was observed when alkylaluminium is added to the polymerization system. On the other hand, only Ph 3 CB(C 6 F 5 ) 4 is an efficient cocatalyst for the propene polymerization with Cp * 2 TiMe 2 . The polymer obtained with Cp * 2 TiMe 2 /Ph 3 CB(C6F5)4 as catalyst is atactic, even in the presence of CH 2 Cl 2 or alkylaluminium. Based on these results, the stereospecificity of achiral titanocenes is discussed.

Control of molecular weight distribution of isotactic polypropylene obtained by a MgCl2-supported TiCl4 catalyst

Abstract It is of great importance in propene polymerization to control molecular weight and molecular weight distribution as well as isotacticity. Propene polymerization was carried out with an isospecific MgCl2/TiCl4-Cp2TiMe2 catalyst in the presence of various kinds of external Lewis bases. It was found that the molecular weight distribution of the isotactic polymer could be controlled while retaining high activity, high isospecificity and high molecular weight only by changing the kind and/or amount of the Lewis bases.

Kinetic Features of Living Polymerization of Propene with the [t-BuNSiMe2Flu]TiMe2/B(C6F5)3 Catalyst

Propene polymerization was conducted by [η1:η3-tert-butyl(dimethylfluorenylsilyl)amido]dimethyltitanium combined with B(C6F5)3 as a cocatalyst. Living polymerization proceeded at -50 °C in the presence of suitable amounts of B(C6F5)3 and AlOct3. Addition of AlOct3 and excess B(C6F5)3 drastically increased the polymer yield and molecular weight with a small increase in the number of polymer chains. The results indicated that these Lewis based enhanced the propagation rate although chain transfer reaction was slightly induced. The time-conversion curve showed that the polymerization rate depended on almost second order of propene concentration

Quick Preparation of Moisture-Saturated Carbon Fiber-Reinforced Plastics and Their Accelerated Ageing Tests Using Heat and Moisture

A quick method involving the control of heat and water vapor pressure for preparing moisture-saturated carbon fiber-reinforced plastics (CFRP, 8 unidirectional prepreg layers, 1.5 mm thickness, epoxy resin) has been developed. The moisture-saturated CFRP sample was obtained at 120 °C and 0.2 MPa water vapor in 72 h by this method using a sterilizer (autoclave). The bending strength and viscoelastic properties measured by a dynamic mechanical analysis (DMA) remained unchanged during repetitive saturation and drying steps. No degradation and molecular structural change occurred. Furthermore an accelerated ageing test with two ageing factors, i.e., heat and moisture was developed and performed at 140–160 °C and 0.36–0.62 MPa water vapor pressure by using a sealed pressure-proof stainless steel vessel (autoclave). The bending strength of the sample decreased from 1107 to 319 MPa at 160 °C and 0.63 MPa water vapor pressure in 9 days. Degraded samples were analyzed by DMA. The degree of degradation for samples was analyzed by DMA. CFRP and degraded CFRP samples were analyzed by using a surface and interfacial cutting analysis system (SAICAS) and an electron probe micro-analyzer (EPMA) equipped in a scanning electron microscope.

Highly Accelerated Aging Method for Poly(ethylene terephthalate) Film Using Xenon Lamp with Heating System

PET films were degraded at temperature higher than 100°C with steam and xenon light by using the newly developed system. Degradation products obtained using the proposed and conventional systems were essentially the same, as indicated by the similar increase in the intensity of the carbonyl peak near 1685 cm−1 in the FT-IR spectra of irradiated specimens and spectrum of original PET film. Elastic moduli derived from the stress-strain (SS) curves obtained in tensile tests were almost the same in the case of the proposed and conventional systems and were independent of the heating temperature, light intensity, and irradiation time. Tensile strength of degraded PET films decreases with increasing heating temperature. Tensile strengths of PET films degraded at same temperature decrease linearly with increasing intensity of xenon light. The lifetime at 90% strength of PET films was calculated. Attempts were made to express this lifetime as functions of the light intensity and the reciprocal of the absolute temperature by using the Eyring model. Estimated lifetime 15.9 h of tensile test using Eyring model for PET film agreed with the lifetime 22.7 h derived from data measured using the xenon weather meter.

Development of novel MgCl2 supported catalyst with trivalent titanocene complex of Cp2TiCl2AlCl2 for propylene polymerization

Three kinds of MgCl2-supported trivalent titanocene catalyst (Cat. 1: Cp2TiCl2AlCl2/MgCl2, Cat. 2: CpCp*TiCl/MgCl2, Cat. 3: Cp2TiCl/MgCl2) were prepared and tested for propylene polymerization. It was found that Cat. 1, combined with ordinary alkylaluminum as cocatalyst, produced PP containing 31.8 wt % of isotactic PP in fairly good yield. On the other hand, Cats. 2 and 3 hardly showed any activity. The effects of diisopropyldimethoxysilane (DIPDMS) on isospecificity of the Cat. 1 also were investigated. The isotactic index (I.I.) of PP was improved drastically by the addition of DIPDMS as external donor and reached the value as high as 98.4%, even in the absence of any internal donors.

Structure-property relationships of polypropylene-based nanocomposites obtained by dispersing mesoporous silica into hydroxyl-functionalized polypropylene. Part 1: toughness, stiffness and transparency

AbstractThe long-range objective of this study is to provide better understanding of the relationship between the structures and properties of PP-based nanocomposites containing mesoporous silica (MPS). In this investigation, nanocomposites composed of MPSs with various porosity structures (two types of Santa Barbara Amorphous No. 15 (SBA-15) with pores of 4.4 or 8.0 nm, and Mobile Composition of Matter No. 41 (MCM-41) with pores of 2.9 nm) and polypropylene (PP) or functionalized PP containing hydroxyl groups (PPOH) were developed. Their physical properties were then evaluated. The nanocomposite containing PPOH and SBA-15 with a large pore size (SBA-15-L) showed higher toughness, stiffness, and transparency than the other nanocomposites. Our results indicated that the larger pore size of SBA-15-L and the high affinity between PPOH and the MPS surface led to an efficient pore-filled state of SBA-15-L with polymer molecules, forming a nanocomposite with better mechanical strength and transparency.Nanocomposites composed of mesoporous silica (MPS) materials with various porosity structures (two types of SBA-15 with pores of 4.4 or 8.0 nm, and MCM-41 with pores of 2.9 nm and polypropylene (PP) or functionalized PP containing hydroxyl groups (PPOH) were developed. The nanocomposite containing PPOH and SBA-15 with a pore of 8.0 nm showed higher toughness, stiffness, and transparency than the other nanocomposites.