Water–formaldehyde–hydrogen sulfide system. II. Formation and growth of thiomethylenic chains.

A linear polymer with a high melting point is obtained from the water–formaldehyde–hydrogen sulfide system in the presence of sulfuric acid. This polymer is substantially formed by a polythiomethylene chain with a few oxymethylene units. Its formation involves a topochemical reaction of the mercaptomethanol present in solution on the first separation solid of the system. On heating, the polymer loses oxymethylene units; in the same way, the first solid product separated from the system loses formaldehyde and undergoes a morphological and chemical transformation to polythiomethylene.     

醋酸丙酸纤维素的非均相合成及表征

采用非均相催化酯化法合成醋酸丙酸纤维素(CAP),在乙酸/乙酸酐/丙酸酐体系中,以浓硫酸为催化剂合成出一系列不同取代度的CAP,并FT IR分析证实了酯化产物的生成。研究酯化剂组成(不同比例的乙酸酐/丙酸酐)、原料聚合度、催化剂用量和反应时间对CAP粘度及热性能的影响以及产品CAP的酰基含量对溶解性的影响。得到较稳定热性能CAP的反应条件为:采用聚合度DP=1926的木纤维素,催化剂用量10%(wt,相当于纤维素),40℃酯化反应3h。     

Synthesis of poly(ester‐anhydride)s based on poly(ϵ‐caprolactone) prepolymer

The objective of this study was to prepare high molecular weight poly(ester‐anhydride)s by melt polycondensation. The polymerization procedure consisted of the preparation of carboxylic acid terminated poly(?‐caprolactone) prepolymers that were melt polymerized to poly(?‐caprolactone)s containing anhydride functions along the polymer backbone. Poly(?‐caprolactone) prepolymers were prepared using either 1,4‐butanediol or 4‐(hydroxymethyl)benzoic acid as initiators, yielding hydroxyl‐terminated intermediates that were then converted to carboxylic acid‐terminated prepolymers by reaction with succinic anhydride. Prepolymers were then allowed to react with an excess of acetic anhydride, followed by subsequent polycondensation to resulting high molecular weight poly(ester‐anhydride)s. Upon coupling of prepolymers, size exclusion chromatography analyses showed an increase from 3600 to 70,000 g/mol in number‐average molecular weight (M_n) for the 1,4‐butanediol initiated polymer, and an increase from 7200 to 68,000 g/mol for the 4‐(hydroxymethyl)benzoic acid‐initiated polymer. 4‐Hydroxybenzoic acid and adipic acid were also used as initiators in the preparation of poly(?‐caprolactone) prepolymers. However, with these initiators, the results were not satisfactory. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 176–185, 2001     

Effects of various factors on the formation of high molecular weight polyamic acid

The reaction of pyromellitic dianhydride (PMDA) and aromatic diamine in an aprotic solvent such as dimethylacetamide (DMAc) gives a solution of poly(amic acid). The effects of certain variables on the polymerization and some additives on the stability and imidization of the poly(amic acid)s were studied. It was found that the addition of PMDA portionwise to the solution of diamine always keeps the excess diamine in solution and enables one to obtain the highest molecular weight of poly(amic acid). When the addition process was reversed, either by the change or dehydration of solvent, a high molecular weight was not attained. The inevitable water in the solvent or the reaction medium is the major factor, and the more the water content in the solvent or the reaction medium, the larger is the probability of destruction of PMDA during the reaction and hence low molecular weight is obtained. If very pure monomers were used in the polymerization, the 1:1 of molar ratio is the optimum value. Excess diamine or dianhydride results in the exchange reaction with poly(amic acid) and causes a rapid degradation of polymer chain. This exchange reaction was proved by NMR measurements. The presence of electrophilic agents or the nucleophilic agents containing active protons in the poly(amic acid) solution promotes the decomposition of polymer and causes the brittleness of polyimide film in the curing process. Using acetic anhydride (A) to convert the poly(amic acid) to polyimide, pyridine (P) can protect the polymer chain from the nucleophilic attack by the anhydride. The mixture with proper ratio of A/P (1/1–15/1) can be used as good dehydrating agents. Meanwhile, according to the results to the results of experiments, we suggested the probable reaction mechanisms about how the water, amine, and anhydride destroy the polyamic acid chains.     

催化剂对4-乙酰氧基苯甲酸的合成影响研究

以对羟基苯甲酸(PHB)和乙酸酐(Ac2O)为原料,醋酸(HAc)为溶剂,考察浓硫酸和杂环化合物催化合成4-乙酰氧基苯甲酸(PABA),反应物配比为羟基苯甲酸∶乙酸酐∶醋酸=1∶1.05∶0.5,确定最佳催化剂加入量、反应时间和反应温度。结果表明,浓硫酸为催化剂时,最佳反应时间2 h,反应温度100℃,催化剂加入量为PHB质量的4%,产率67%;杂环化合物P为催化剂时,最佳反应温度80℃,反应时间2 h,催化剂加入量为PHB质量的0.3%,产率99.8%。杂环化合物比浓硫酸对PABA合成有更好的催化活性,反应条件温和,具有较好的工业化应用前景。     

大麻秆浆制备醋酸纤维素的研究

以大麻秆浆和醋酸为原料制备了醋酸纤维素。考察了硫酸用量、保温温度、保温时间、醋酐用量和冰醋酸用量对醋酸纤维素取代度和聚合度的影响。采用红外光谱和X射线衍射分析对醋酸纤维素进行了表征。实验结果表明:增加硫酸用量、提高保温温度和延长保温时间可提高醋酸纤维素的取代度,但聚合度下降;增加醋酸酐用量可提高醋酸纤维素的取代度,对聚合度影响不大;增加冰醋酸用量可提高醋酸纤维素的聚合度,对取代度影响不大。制备醋酸纤维素的适宜条件为:硫酸、醋酸酐和冰醋酸对大麻秆浆的质量比分别为0.13、9.0和9.0,保温温度为50℃,保温时间为1 h。该条件下制备的醋酸纤维素取代度为2.92,聚合度为121。由醋酸纤维素的红外光谱可证实纤维素与醋酸酐之间醋化反应的发生。X射线衍射分析表明大麻秆浆经醋化反应后,纤维素晶型发生了明显的变化。     

妊娠双烯醇酮醋酸酯的合成

研究了以薯蓣皂素为原料合成妊娠双烯醇酮醋酸酯生产工艺中的开环、氧化和水解3步反应。实验结果表明,薯蓣皂素与醋酐、冰醋酸在高压釜中160℃下反应9h,中间产物假薯蓣皂素醋酸酯的收率达到94 6%。CrO3按n(假薯蓣皂素醋酸酯)∶n(CrO3)=1∶2 2的量比与醋酸钠和水配制成氧化剂溶液,与开环反应液在0～5℃下滴加反应1h,然后回流水解反应1 5h左右,氧化-水解2步反应收率达到88%～90%。经分离,妊娠双烯醇酮醋酸酯产品总收率达到82 3%,较工业平均生产水平72%～74%有较大的提高。     

1,3-二乙酰氧基-2-乙酰氧基甲氧基丙烷的合成

以环氧氯丙烷为起始原料与浓盐酸反应制得1,3-二氯-2-丙醇,再在浓硫酸催化下与多聚甲醛缩合得1,3-二氯-2-丙醇的半缩甲醛,不经分离,直接用醋酐酰化得1,3-二氯-2-乙酰氧基甲氧基丙烷,后者与醋酸钠反应得标题化合物。以环氧氯丙烷计4步反应总收率为55.6%。     

Synthesis of cellulose triacetate-I from microfibrillated date seeds cellulose (<Emphasis Type="Italic">Phoenix dactylifera L.</Emphasis>)

Cellulose triacetate (CTA) has successfully been synthesized from microfibrillated date seeds cellulose. The cellulosic material under study constituted 84.9% amorphous phase with a degree of polymerization of 950. Acetylation was conducted at 50 °C under optimized heterogeneous conditions by acetic anhydride as acetyl donor, acetic acid as solvent and sulfuric acid as catalyst. In this process, cellulose was acetylated without dissolving the material throughout. The acetylated cellulose chains on the surface were dissolved gradually in acetic acid, which created new accessible zones. The yield of cellulose triacetate was studied varying acetic acid, acetic anhydride and catalyst concentrations, as well as reaction times. The ratio between the intensity of the acetyl C=O stretching band at around 1740 cm^?1 and the intensity of C–O stretching vibration of the cellulose backbone at 1020–1040 cm^?1 was used to optimize the reaction time. The optimal reaction conditions of 8% concentration of sulfuric acid, acetic anhydride/cellulose weight ratio of 3:1, acetic acid/cellulose weight ratio of 7:1, reaction time of 3 h and reaction temperature of 50 °C have given highest yield of cellulose triacetate, of about 79%. The obtained date seeds-based cellulose triacetate was characterized thoroughly by Fourier transform infrared (FTIR), X-ray diffraction (XRD), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The synthesized product was identified as cellulose triacetate-I (CTA-I) characterized by a melting temperature of 217 °C and a decomposition temperature of 372 °C. These results demonstrated that date seeds can be used as potential source of microfibrillated cellulose which can be easily functionalized.     

双烯醇酮醋酸酯的合成新工艺研究

以从脱胶后胡芦巴的脚渣料中提取的胡芦巴薯蓣皂苷元为原料,经裂解、过氧化氢氧化、水解消除反应合成双烯醇酮醋酸酯。结果表明,与冰醋酸及醋酐在180℃下反应5 h,中间产物假薯蓣皂苷元醋酸酯的收率达到95.48%。采用均匀设计对过氧化氢氧化工艺进行了优化,确定氧化工艺优化条件为:催化剂加量为4.2%,30%过氧化氢加量∶假薯蓣皂苷元醋酸酯=2.5∶1,30℃反应1.5 h,再沸腾回流水解反应3 h,收率可达63.38%。     

不同分子量聚酯的羟值分析方法

用醋酐／高氯酸／乙酸乙酯法，醋酐吡啶回流法，分别对相对分子质量为１１００－１２０００的聚酯进行了羟值的测定，并用气压渗透法和析出物溶解重滴法进行了核对。结果表明醋酐／高氯酸／乙酸乙酯法对于Ｍ〈５０００的聚酯是适用的，而高分子量的聚酯则必须用醋酐／吡啶回流法，才能获得满意的结果。     

Synthesis and characterization of copolymers obtained from 1,3,5-trioxane and octamethylcyclotetrasiloxane by triflic acid initiator

Summary A series of poly(oxymethylene-co-dimethylsiloxane) copolymers were synthesized in the molten state by cationic ring opening copolymerization of trioxane and octamethylcyclotetrasiloxane by using trifluoromethanesulfonic acid (triflic acid; CF₃SO₃H) as initiator. When the concentration of the oxymethylene comonomer units (-OCH₂-) in the copolymers are very high, crystalline copolymers are obtained. If the concentration of the dimethylsiloxane co-units (-OSi(CH₃)z-) increases, rubberlike materials are obtained. Reaction mechanisms are proposed to explain the growth of the copolymer chains. FTIR and NMR studies suggest the existence of block copolymers and block copolymers with random segments. Thermomechanical characterization of the copolymers was also carried out. This new synthetic method allows us to obtain linear copolymers containing both oxymethylene and dimethylsiloxane comonomer units in the main chain. The copolymerization of these cyclic monomers was demonstrated.     

Poly(amide-imide-esters) derived from asymmetric diacids and diphenols containing silicon or carbon as central atom. Synthesis,characterization and thermal studies

Poly(amide-imide-esters) (PAIEs) were obtained from a series of unsymmetrical diacids containing an amide and an imide group in the structure and diphenols containing Si or C as central atoms. The unsymmetrical diacids were obtained from trimellitic anhydride chloride which reacted with p-aminobenzoic acid, followed by the reaction of the resulting amide–imide acid with an amino acid such as glycine, L-alanine, L-valine, and p-aminobenzoic acid. The obtained monomeric diacids were polymerized with bisphenol-A and with the analogous bisphenol containing silicon as central atom to give PAIEs. These polymers were characterized by spectroscopic methods and their main properties such as solubility, molecular weight, glass transition, and thermal stability were studied in correlation with the presence of C or Si atoms in the bisphenol segment and with the amount of aromatic units in the diacid segment.     

Modified cellulose acetate prepared from acetic anhydride reacted with cellulose dissolved in a chloral–dimethylformamide mixture

A bleached sulfite pulp (85.0% α-cellulose) was dissolved in dimethylformamide containing anhydrous chloral and pyridine as catalyst. The clear cellulose solution was then reacted with acetic anhydride under various conditions. The reaction products contained both acetyl groups and chlorine in amounts varying from 20% to 38%. Curves of reaction rates with respect to chlorine and acetyl groups under various conditions of temperature and reactant ratios were similar in appearance, and all the products contained approximately 2 moles of acetyl groups per mole of chloral. Yields varied from 180% after treatment at room temperature (25°C) for 1 hr to 250% after 4 hr. The products could be hydrolyzed in acid with some difficulty but very easily in dilute alkali. The products had low flammability and hygroscopicity. Films cast form acetone solutions had higher permittivity and lower a.c. conductivity than similar films made from cellulose diacetate.     

Preparation and electrodeformation of silicone dielectric elastomers containing poly(propylene glycol diacetate) with different molecular weights

In this study, poly(propylene glycol diacetate)s (PPGDAs) with different molecular weights were obtained by the esterification reaction of poly(propylene glycol) and acetic anhydride. We effectively reduced the residual moisture and hydrophilicity of PPGDA. Then, poly(dimethyl siloxane) (PDMS) was modified by the addition of only 5 wt % PPGDA, which possessed a high dielectric constant (k) and a large actuated strain at a low electric field. PPGDA was used to enhance the molecular polarity because of the more polar oxygen atoms and the greater number of ester groups. The great increase in k and the low elastic modulus of the PPGDA–PDMS composites lead to a great increase in the electromechanical sensitivity. When the molecular weight of PPGDA was about 4000, the PPGDA–PDMS composites had the largest actuated strain. As a result, compared to the pure silicone elastomer (8.94%), it exhibited a greater strain of 17.31% at a low electric field of 10.5 V/μm (an increase of ca. 1.94 times). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45329.     

Preparation and characterization of wood polyalcohol‐based isocyanate adhesives

Sugi (Criptmeria Japonica) wood meal was liquefied at 150°C with a mixture of poly(ethylene glycol) 400 and glycerin in the presence of a sulfuric acid catalyst. The resulting liquefaction products were used directly to prepare isocyanate adhesives via mixing with polymeric diphenylmethane diisocyanate without the removal of the residue. The properties of the liquefaction products and the performances of bonded plywood were tested. The results showed that the residue content decreased and the hydroxyl value increased as the reaction time increased. The viscosity and weight‐average molecular weight significantly changed with the reaction time. All the dry test results of the shear strength met the Japanese Agricultural Standard (JAS) criteria for plywood. After a cyclic steaming treatment, however, only the plywood bonding with adhesives from the liquefied wood with a reaction time of 1.5 h satisfied the JAS criteria. The wood failure was very low. The emissions of formaldehyde and acetaldehyde were extremely low. Liquefied‐wood‐based isocyanate adhesives have the potential to become ideal wood adhesives because of their bond durability, safety, and recyclability.     

细菌纤维素乙酰化改性研究

以细菌纤维素为原料,浓硫酸为催化剂,与醋酸酐进行乙酰化反应,制得醋酸细菌纤维素(BCA),讨论了反应温度、反应时间、固液比、催化剂的用量对合成BCA的影响。结果表明:细菌纤维素的羟基被乙酰基取代。适宜的反应条件为反应温度70℃,反应时间2.5 h,细菌纤维素为1.0 g时,醋酸酐用量为20mL,催化剂浓硫酸用量为0.1 mL,BCA产率可达98%以上,取代度达2.9以上。     

乙酰水杨酸微型化合成实验研究

探讨乙酰水杨酸微型化合成的最佳实验条件。以浓硫酸作催化剂,用乙酸酐与水杨酸进行酰化反应制备乙酰水杨酸,改变反应条件进行实验,重点考察了反应物摩尔数比、反应温度、反应时间及催化剂等条件对反应的影响。乙酰水杨酸微型化合成的最佳实验条件是:乙酸酐和水杨酸的摩尔数比为3∶1,反应温度60~80℃,以浓硫酸作催化剂,反应时间3~5 min。     

马来酸酐改性端羟基乳酸预聚体的合成及性能研究

采用聚乙二醇（PEG）与乳酸反应,合成了端羟基乳酸预聚体（PLEG）。然后将PLEG与马来酸酐进行直接熔融缩聚得到改性聚乳酸（MPLA）。采用正交分析法探讨了原料比、反应温度、反应时间等工艺条件对MPLA相对分子质量的影响,并研究了MPLA的亲水性能、力学性能和在体外模拟生物环境中的降解特性。结果表明：马来酸酐与PLEG的质量比为1:15,在130 ℃反应15 h,MPLA的黏均相对分子质量最大为61564。相较于PLEG,MPLA的拉伸强度、弹性模量和断裂伸长率明显提高,亲水性得到改善。MPLA在体外模拟生物环境中的降解性能较好,其降解速率与马来酸酐含量有关。     

A consecutive microreactor system for the synthesis of caprolactam with high selectivity

A microreactor system containing two consecutive microreactors and a stirred vessel was developed for the improvement of selectivity of caprolactam (CPL) synthesis. The first microreactor was used to conduct the reaction of cyclohexanecarboxylic acid and oleum, and 97% selectivity for the intermediate product, named mixed anhydride, was obtained. The mixed anhydride then quickly reacted with nitroso‐sulfuric acid in the second microreactor, and the reaction was completed in the vessel, where CPL selectivity reached 93.9%, a much higher value than that achieved either in a control experiment with a batch reactor or in industrial process. The advantage of microreactors is that they can provide high‐quality mixed anhydride and can mix it quickly with the nitroso‐sulfuric acid prior to reaction in the vessel reactor, which, from an engineering standpoint, gives better performance than the traditional syringe‐fed method that is common in chemical synthesis. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1959–1967, 2015