铝系催化剂催化合成聚酯的性能研究

以5种含铝化合物为催化剂,采用对苯二甲酸二甲酯（DMT）路线合成聚酯,对聚合产物进行特性黏度、色值和DSC分析。结果表明：5种铝系催化剂的催化活性均低于常规催化剂,其中,铝酸钠的催化活性最高;铝系催化剂所得的聚酯的色相b值高于Sb2O3催化的聚酯的b值,但低于钛酸正丁酯催化的聚酯的b值;铝酸钠和硅酸钠复合后作为催化剂,不改变PET切片的等温结晶规律,且催化所得聚酯的结晶青色力比常规Sb2O3催化的聚酯略有提高;选择溶解性好的含铝化合物和减少催化剂用量对增加催化活性和改善聚酯色相有利。     

钛系催化剂在半消光聚酯生产中的应用

在300 t/d聚酯(PET)装置上通过减少锑系催化剂添加量,逐步将钛系催化剂添加比例由15%提高至100%,最终实现钛系催化剂生产环保型PET产品,分析了钛系催化剂替代量对PET切片质量、热性能以及过滤器切换周期的影响。结果表明:随着钛系催化剂替代比例的提高,PET切片色相b值大幅上升,将酯化Ⅰ釜温度由264℃下降至256℃,酯化Ⅱ釜温度由268℃下降至259℃,增大调色剂添加量控制在30μg/g以内,可保证色相L值不低于90;将预聚釜Ⅰ温度由271℃下降至265℃,预聚釜Ⅱ温度由276℃下降至274℃,终缩聚温度由278℃下降至276℃,可将端羧基含量控制在指标要求范围;将酯化Ⅰ釜压力由65k Pa提高至79 k Pa,工艺塔釜温由175℃提高至178℃,可缓解二甘醇含量下降幅度,但对二甘醇含量提高效果不明显;全钛系PET比全锑系PET降温峰值温度低13.66℃,降温峰值温度与冷结晶温度之差低20.29℃,有利于纺丝;全钛系PET生产中过滤器切换周期比全锑系PET的长。     

纤维及薄膜级PET色相b值的影响因素分析

在1 kt/a、10 kt/a及150 kt/a的聚对苯二甲酸乙二醇酯(PET)国产化三釜工艺流程生产装置上,采用直接酯化法连续生产纤维及薄膜级PET切片,分析了原料质量、聚合反应温度、催化剂、调色剂等PET切片色相b值的影响.结果表明:为满足用户对PET切片色相b值达0±1的要求,生产中应控制原料精对苯二甲酸(PTA...     

瓶级PET切片色相b值的影响因素

从瓶级PET切片的生产实际出发,通过分析该切片色相b值的影响因素,提出了控制原材料品质、添加剂的含量、生产工艺,是得到色相b值较好的瓶级PET产品的保证。     

钛系催化剂的瓶级PET切片工程化生产

应用钛系聚酯催化剂LT181在25万t连续缩聚PET生产线工程化生产瓶级PET切片。对切片的特性黏度、端羧基值、色值、乙醛含量、二甘醇含量进行检测分析,钛系催化剂能取得和锑系催化剂相似的技术指标。     

PET切片色相b值的影响因素

从PET切片的生产实际出发,从主要原材料、辅助材料、生产工艺等方面分析聚酯切片色相b值的影响因素,提出了控制原材料品质、添加剂的含量、生产工艺,是得到色相b值较好的PET产品的保证。     

钛系催化剂在PET合成中的催化性能研究

采用2 L不锈钢反应釜,考察了自制钛系催化剂对聚酯(PET)生产过程中酯化反应和缩聚反应以及产品色度的影响。结果表明:自制钛系催化剂对PET生产过程中的酯化反应具有催化作用,同三氧化二锑催化剂相比,自制钛系催化剂可缩短酯化反应时间33%;自制钛系催化剂在缩聚过程中的催化反应活性高于三氧化二锑催化剂,可缩短缩聚反应时间45%;随着反应体系中钛含量的增加,缩聚产物达到一定黏度所需的缩聚反应时间降低,但缩聚产物的色相b值升高;合理的自制钛系催化剂的起始添加量应控制在7μg/g以下。     

新型钛系聚酯催化剂的催化性能研究

合成了一种应用型钛系聚酯(PET)催化剂TY,考察了在PET合成中催化剂TY对酯化时间、缩聚时间、产品性能等的影响;并与传统锑系催化剂三氧化二锑(Sb2O3)的性能进行了对比。结果表明:钛系催化剂TY不仅能缩短酯化时间和聚合时间,而且催化剂用量少、催化活性高;钛系催化剂TY用量为20~25μg/g时,催化活性最佳,催化剂TY 20~25μg/g的催化活性相当于Sb2O3350~400μg/g的催化活性;钛系催化剂合成的PET切片的特性黏数达0.683 d L/g,与锑系PET相比,色相L值提高达71.68,b值相差不大,端羧基含量及二甘醇含量降低,结晶行为及热性能相当;钛系催化剂TY适合无重金属聚酯的工业生产,工业应用性强。     

钛系瓶级PET切片的合成及其固相增黏工艺研究

使用自制钛催化剂在2L聚合反应釜中合成钛系聚酯(PET)基础切片,探讨了调色剂、稳定剂、助剂对反应过程及切片性能的影响;然后在50 L聚合反应釜中进行了放大试验,并将基础切片在真空转鼓中进行固相增黏,得到瓶级PET切片。结果表明:在相同的聚合反应条件下,钛催化剂用量(以钛离子计,相对于精对苯二甲酸(PTA))为7μg/g时,合成的钛系基础切片的色相、乙醛含量与乙二醇锑用量(以锑离子计,相对于PTA)为220μg/g时得到的锑系基础切片相当;在钛系基础切片合成中添加助剂,在固相增黏时合理控制升温过程,可有效解决钛系基础切片在固相缩聚反应中存在的固相增黏速率、切片色相与乙醛含量之间相互制约的矛盾,增黏后的钛系瓶级PET切片的色相、乙醛含量等指标优于锑系瓶级PET切片。     

锑钛复合催化剂半消光聚酯等温结晶性能研究

采用锑(Sb)钛(Ti)复合催化剂,在300 L反应釜中合成半消光聚对苯二甲酸乙二醇酯(PET),通过差示扫描量热仪研究了不同Sb/Ti复合比的PET在195~210℃的等温结晶性能,并对PET的常规性能和热性能进行表征。结果表明:随着复合催化剂中Ti含量的增加,PET的等温结晶速度先快后慢,Ti系催化剂质量分数为50%时,PET等温结晶速度最快,Ti系催化剂质量分数为100%时,PET等温结晶速度最慢;当Ti系催化剂质量分数大于50%时,PET切片开始变黄;随着催化剂中Ti含量的增加,PET的冷结晶温度逐渐升高,熔融结晶温度先升高后降低,Ti系催化剂质量分数为50%时出现拐点。     

Vacuum Frying of Carrot Chips

Abstract

Vacuum frying is an alternative method to produce high quality vegetable or fruit chips. The effect of frying temperature and vacuum degree on moisture content, oil content, color, and texture of fried carrot chips were investigated. During the early stage of vacuum frying, the rate of moisture removal and oil absorption increased with increasing frying oil temperature and degree of vacuum. Statistical analysis of the color data showed that there were no significant differences P > 0.05) in lightness (L), redness (a), and yellowness (b) of carrot chips as a function of vacuum degree and temperature. The breaking force of carrot chips decreased with increasing frying temperature and vacuum degree. The statistical analysis also showed that there were no significant differences P < 0.05) in the breaking force as a function of temperature, but the breaking force was significantly (P < 0.05) affected by the vacuum degree.     

Effect of Vacuum-Microwave Predrying on Quality of Vacuum-Fried Potato Chips

The effects of vacuum microwave predrying on the quality of vacuum-fried potato chips were studied. The results showed that vacuum microwave predrying had a significant effect on moisture and oil contents, as well as color parameters and structure of potato chips. Vacuum microwave predrying significantly decreased the oil and moisture contents of vacuum-fried potato chips. The rates of both mass transfer phenomena (water loss and oil uptake) that take place during the vacuum frying of potato chips decrease due to the vacuum microwave predrying. The vacuum microwave predrying had a negative effect on color of potato chips, which decreases the L value of potato chips and increases Hunter a and b values. Breaking force of fried potato chips is also significantly (P < 0.05) affected by the drying pretreatment, which decreases the breaking force at the beginning of predrying and then increases with vacuum microwave predrying time.     

高效催化剂在聚酯合成中的应用研究

选择乙二醇锑以及至少一种锰、锌、钴、铅等金属醋酸盐共同组成高效聚酯催化剂体系 ,研究其对缩聚反应的催化作用。实验证明 ,高效催化剂可明显加快缩聚反应速度 ,制得质量合格的PET切片。通过添加碱金属醋酸盐即可改善PET切片色泽 ,碱金属醋酸盐离子浓度 4.5～ 9μg/g较为合适 ,不需添加光学增白剂     

影响转鼓增黏切片质量因素的分析

转鼓增黏聚酯切片存在很多问题,如增黏切片的结晶度不一致,黏度有波动,反应速度难控制,切片粉尘含量高,存在异色切片,批与批之间质量有差异等。通过对转鼓生产的总结,寻找影响转鼓增黏切片质量的因素。结果表明:通过对增黏工艺和设备的改进,并筛选优化增黏工艺参数,加强管理制度建设,有针对性地解决切片增黏过程中存在的相关问题,就能很好地控制转鼓增黏切片的质量。     

Effect of low temperature on the microwave-assisted vacuum frying of potato chips

The objective of this study was to investigate the effect of low temperature on the microwave-assisted vacuum frying of potato chips. A newly built, in-house, microwave-assisted frying machine was developed and used in this study. The effect of low temperature on the microwave-assisted vacuum frying of potato chips was investigated via comparing sample properties prepared with frying temperatures of 90°C, 95°C, and 100°C. The experience was taken at the same vacuum degree in every frying process. Parameters of included moisture content, oil content, color parameters (lightness, redness, and yellowness), and textures (hardness, crispness) were used to evaluate the effect of different frying temperatures on the microwave-assisted vacuum frying of potato chips. Results showed that with lower temperature in microwave-assisted frying, the rate of moisture evaporation of potato chips was slowed down and the time of the ending of frying was prolonged from 10 min with a frying temperature of 100°C to 14 min with 90°C and 12 min with 95°C. Meanwhile, the oil content in fried potato chips was increased with lower temperature in microwave-assisted vacuum frying. The breaking force of final products are not significantly (p > 0.05) affected in different frying temperatures of microwave-assisted vacuum frying. Also, the frying temperature of 100°C in microwave-assisted vacuum frying had better preservation of natural color than the lower frying temperature with prolonged frying time. Results showed that the temperature is one of the main factors that affect the quality of microwave-assisted vacuum frying of potato chips and the producer could find suitable temperature conditions according to experience.     

纤维级聚酯切片色度的影响因素

通过分析纤维级聚酯切片色度的影响因素,确认PTA品质、催化剂与添加剂的种类和含量、生产负荷、温度、压力及外观为主要影响因素。通过对它们进行调控,可生产出色度均一、晶亮的聚酯切片,从而改善聚酯产品的可纺性及其纤维的色度。     

瓶级PET切片品质对后续加工的影响

讨论了瓶级PET切片的品质,如黏度、色相、结晶度、乙醛含量、百粒质量、水分、粉尘含量、熔点、灰分等这些指标对后续加工工艺的一些要求和影响,以及控制这些指标的一些影响因素和方法。     

半连续PET生产影响因素的分析

分析了半连续PET生产的影响因素 ,指出原料质量、催化剂种类、反应时间、温度、压力等因素与切片中羧基含量的关系 ,只有把这些因素控制好 ,才能生产出符合国家优级品标准的质量稳定的聚酯切片     

Effect of Various Pretreatments on the Quality of Vacuum-Fried Carrot Chips

Carrot slices were subjected to the following four different pretreatments prior to vacuum frying: (1) blanching, (2) blanching and air drying, (3) blanching and osmotic dehydration, (4) blanching, osmotic dehydration, followed by freezing. The effects of these pretreatments on the physicochemical properties and fat distribution in vacuum-fried carrot chips were also investigated. There were significant differences in the total yield, amounts of carotenes, vitamin C, and the color values of carrot chips following different pretreatments (P < 0.05). Pretreatment significantly affected the water content, fat content, and water activity of carrot chips (P < 0.05), while there were no significant differences in the breaking force of carrot chips treated with different pretreatments (P > 0.05). Spearman correlation analysis showed a high positive correlation between the fat content of carrot chips and the initial water content of carrot slices. The fat distribution pattern depended on the initial water content and the structure of the material left by water evaporation.     

Low oil content potato chips produced by infrared vacuum pre-drying and microwave-assisted vacuum frying

The effects of vacuum infrared radiation (VIR) pre-drying on the microwave-assisted vacuum frying (MVF) potato chips were investigated to study its possibility of decreasing the oil content of fried potato chips. The moisture evaporation, oil content, texture, color, surface temperature, shrinkage, and sensory analysis of fried products were evaluated. Results showed that the VIR pre-drying significantly reduced the oil content in MVF products, a decrease from 22.38 to 13.49?g oil/100?g dry solid. The application of VIR pre-drying accelerated the dehydration rate, and increased the mechanical breaking force measured with a texture analyzer with 20–30?min pre-drying. The VIR pre-drying resulted in an increase in the total color change and the shrinkage of MVF potato chips. The sensory analysis showed that the proper duration of VIR pre-drying would achieve a higher consumers’ acceptance. Comparing with the current industrial applications, vacuum frying, and atmospheric deep-fat frying, the combined VIR and MVF technology would be an alternative frying method for producing healthier fried products with less oil content and high quality.