Katsuo Mitani

Melting and crystallization behaviors of injection‐molded polypropylene

The melting and crystallization behaviors of the skin layer in an injection-molded isotactic polypropylene (PP) have been studied, mainly in comparison with those of the core layer and subsidiarily in comparison with those of a compression-molded PP and a nucleator (talc)–added PP. The skin layer contains about 5% crystals, which have a high melting point of up to 184°C. They thermally vanish by melting once. The subsequent melting history will scarcely affect the melting behaviors. On the other hand, crystallization behaviors are strongly affected by the melting history. The skin layer crystallizes in a wide temperature range at high temperature. This tendency weakens with increasing melting temperature, approaching a constant and that of the core layer above 230°C, which suggests that the memory effect of the residual structure of PP vanishes by melting above 230°C. In explaining these experimental results, it is assumed that the residual structure substance is a melt orientation of molecular chains that works as crystallization nuclei and that the vanishing of the residual structure is nothing but a relaxation of the melt orientation.

Glycidyl methacrylate-styrene copolymer latex particles for immunologic agglutination tests

New latex particles for immunologic agglutination reaction were prepared by a seeded polymerization technique for the emulsifier-free copolymerization of styrene and glycidyl methacrylate. The surface of the latex particles was presumed to be dotted with hydrophilic domains, giving stability to the particles. The remaining areas, to which many antigens or antibodies were strongly adsorbed, were hydrophobic. Various groups of the glycidyl methacrylate-styrene latex particles were coated with human immunoglobulin G, and immunologic agglutinating potencies were compared by the box-titration method. Immunologic reactivities of the latex particles decreased with an increase of glycidyl methacrylate content at concentrations of 1 mol% or higher. Latex particles containing 0.5 to 0.75 mol% GMA caused strong immunologic agglutination besides showing good stability, indicating the availability of these latex particles. Glycidyl methacrylate-free polystyrene latex particles caused non-specific agglutination, while the immunologic agglutinating ability of glycidyl methacrylate-styrene latex particles, prepared by the unseeded polymerization technique was weak.

Polymerization Mechanism of Vinyl Chloride with Trialkylaluminum-Lewis Base Catalyst and Thermal Stability of Poly(vinyl Chloride)

Abstract The mechanism of vinyl chloride polymerization by the tri-ethylaluminum-Lewis base-carbon tetrachloride catalyst system and the thermal stability of the resulting polymer were investigated. When the Lewis base is multidentate, the resultant complex with triethylaluminum shows significantly high catalytic activity for radical polymerization of vinyl chloride in the presence of carbon tetrachloride to give a white powder with high molecular weight. Carbon tetrachloride accelerates the rate of polymerization and participates in an initiating process rather than in a propagating step. The thermal stability of the polymer prepared with this catalyst system is much superior to that of commercial polyvinyl chloride), although the numbers of the double bonds in a chain end and of the head-to-head linkage are similar in both samples, suggesting that the thermally unstable structures of the former react with triethylaluminum to give the thermally stable structure on the polymerization process.

Mechanism of Reaction of Polyvinyl Chloride) with Triethylaluminum

Abstract Polyvinyl chloride) was treated with triethylaluminum in 1,2-dichloroethane solution. Negligibly small amounts of hydrogen chloride are evolved from the modified polyvinyl chloride) in decomposition at 180°C for 150 min in nitrogen. Quantitative analysis of the rate of dehydrochlorination of the modified polymer gave a calculated activation energy for the alkylation of 8.3 kcal/mole in 1,2-dichloroethane solution; the concentration of the labile chlorines in the original polyvinyl chloride) was less than 0.25 mole % Furthermore, the fact that the average polyene length of the modified polymer for the thermal decomposition was much shorter than that of the starting material suggests that the labile chlorines inherent in the polymer exist not only in the chain end but also in the polymer chain.

Thermal stabilization of poly(vinyl chloride) treated with organoaluminium compounds: 2. Effect of solvents

Abstract Poly(vinyl chloride) was treated with organoaluminium compounds in various solvents. The strong Lewis acids, alkyl-aluminium chlorides, predominantly cause the decomposition of PVC rather than the alkylation of the polymer regardless of solvents. In non-polar hydrocarbons, the treatment of PVC with trialkylaluminiums leads to increased heat sensitivity. In 1,2-dichloroethane solution and in benzene slurry, the trialkylaluminium-treated PVC exhibits significant improvement in thermal stability over unmodified PVC due to the exchange of the labile chlorines inherent in the polymer for relatively more stable alkyl groups. The apparent activation energy of the reaction of PVC with triethylaluminium in benzene slurry is the same as that in 1,2-dichloroethane solution, but the initial rate of alkylation of the polymer in benzene is about 10 times faster than that of the polymer in 1,2-dichloroethane. The aluminium concentration in the PVC particles is about twice that calculated from the swelling ratio of the PVC particles in benzene, suggesting that triethylaluminium not only penetrates into the swollen particles but is also adsorbed on the surface of the PVC particles to cause the increase in the aluminium concentration around the labile chlorines in the polymer chain. The alkylated PVC, compounded with only small amounts of zinc soap including an epoxidized oil and a chelating compound, shows excellent initial stabilization and long-term stability superior to the starting polymer even when this is compounded with 3 parts organotin stabilizers.

Synthesis and Characteristics of Poly(vinyl chloride) with Broad Molecular Weight Distribution.

塩化ビニルの気相重合において, 重合時の相対圧力の変化および2段気相重合により分子量分布の広い塩化ビニル重合体を合成し, 得られた塩化ビニル重合体の熱安定性および加工性 (溶融粘度, 溶融時間) について検討した. 分子量分布は, 重合時の相対圧力が約0.5の時に最大となり, その値は4.2となった. 気相重合で得られた塩化ビニル重合体中の三級塩素およびアリル位の塩素の量は, 分子量の減少とともに増加した. さらに, 脱塩化水素量も同様に分子量の減少とともに増加した. 流動性については, 分子量分布の広い塩化ビニル重合体の低重合度組成の影響が大きく認められ, 溶融粘度が低下した. 溶融時間については, 2段気相重合により得られた分子量分布の広い塩化ビニル重合体は, 分子量分布の狭い塩化ビニル重合体に比べて溶融時間が短くなることが明らかとなった.

Preparation and application of low molecular weight poly(vinyl chloride). III. Mechanical properties of blended poly(vinyl chloride)

The blending effect of poly(vinyl chloride) with relatively higher molecular weight (HMW-PVC) and relatively lower molecular weight (LMW-PVC) has been investigated by measuring various mechanical properties: melt properties, tensile strength, tensile modulus, and impact strength. The blended PVC has slightly improved melt properties in comparison with the HMW-PVC used. The tensile strength of the blended PVC is related to the weight-average polymerization degree (Pw) of LMW-PVC and the LMW-PVC content. At the LMW-PVC content of 20%, the tensile strength of blended PVC is a maximum: approximately 58 MPa.

Synthesis of plasticized poly(vinyl chloride) powders by gas phase polymerization.

ポリ塩化ビニル (PVC) と種々の可塑剤 (2-エチルヘキシルフタラート, アジピン酸系ポリエステル, トリクレジルポスファート) 系について, PVCを上記可塑剤存在下にPVCの貧溶媒を添加し沈殿重合続いて気相重合を行うことにより, 可塑剤がPVC粒子内にミクロ分散した粉体流動性に富むPVC粒子を合成した.上記の方法により合成した可塑剤含有PVC粒子について, 粒子のモルフォロジー及び気相重合に用いるPVCと非相溶である有機溶媒を含めた三成分混合系でのFlory-Hugginsの相互作用パラメーター (χ値) を用いてPVC気相重合方法の検討を行った. 可塑化効率については, 動力学的粘弾性スペクトルの結果に基づいて検討を行い, 本重合法による可塑剤含有PVCは, 同一組成の可塑剤をブレンドした可塑化PVCより可塑化効率が極めて高いことが判明した.