Chinese Journal of Tissue Engineering Research ›› 2016, Vol. 20 ›› Issue (38): 5758-5763.doi: 10.3969/j.issn.2095-4344.2016.38.020
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Received:
2016-07-05
Online:
2016-09-16
Published:
2016-09-16
Contact:
Chen Xiao-nong, Professor, Doctoral supervisor, Beijing Laboratory of Biomedical Materials, Beijing University of Chemical Technology, Beijing 100029, China
About author:
Zheng Meng, Studying for master’s degree, Beijing Laboratory of Biomedical Materials, Beijing University of Chemical Technology, Beijing 100029, China
Supported by:
CLC Number:
Zheng Meng, Luo Xin, Chen Jing-ling, Shi Shu-xian, Liu Jian-dong, Chen Xiao-nong.
2.1 医用热熔胶分类及应用 热熔胶的成分中,基体聚合物用于提供内聚强度和弹性。通常使用高分子量的聚合物来提高热熔胶的内聚强度和黏合力,如聚烯烃(乙烯或丙烯基聚合物),功能化聚烯烃(乙烯或丙烯与含氧单体的共聚物),或苯乙烯嵌段共聚物(苯乙烯-异戊二烯-苯乙烯或苯乙烯-丁二烯-苯乙烯聚合物)等[4-5]。 医疗上使用的热熔胶可按其基体树脂的不同分为无定型聚烯烃热熔胶[6-9]、热塑性弹性体热熔胶[10-12]、丙烯酸酯类热熔胶[13-16]、聚氨酯类热熔胶及其他种类[17-18]。一般应用于外科手术、伤口的覆盖、探测仪器的固定、药物传送系统与皮肤的粘接等[6]。一次性医疗卫生用品,如卫生护垫、纸尿裤等也大规模使用热熔胶[3]。 2.2 无定型聚烯烃热熔胶 聚烯烃材料由于原料丰富,价格低廉,容易加工成型,综合性能优良,因此是一类产量最大、应用十分广泛的高分子材料,也促使聚烯烃热熔胶成为热熔胶产品的主流发展趋势。聚烯烃热熔胶是通过将聚乙烯、聚丙烯或无规共聚聚丙烯等聚烯烃树脂为基料进行共混,并在共混过程中加入改性组分得到的。在某些配方中还通过添加活性单体、催化剂(引发剂)在组分中形成化学接枝或嵌段,或在聚烯烃分子中引入极性功能基团,从而改善粘接性能。以烯烃聚合物为主体的热熔胶已被广泛应用于一次性医疗卫生用品。 Hu等[19]采用无定形聚-α-烯烃共聚物为基体树脂,与乙烯、丙烯、己烯或辛烯共聚单体共聚合,并选用C5树脂、松香树脂、聚萜烯类树脂等中的一种或其混合物为增黏剂,制备了一种低温应用的热熔胶,该无定形聚-α-烯烃共聚物主要是无规立构聚(1-丁烯),其软化点范围为70-105 ℃,可应用于一次性医疗卫生制品,如尿布、女性卫生制品、成人用失禁衬垫、护理垫等。与传统的热熔胶相比,聚烯烃类热熔胶粘接性能更好,成本更低,但是其基体聚合物聚-α-烯烃软化点较低,难以达到医学上常用的水蒸汽灭菌温度所要求的耐热性,使其在医药领域的应用受到一定限制。Czaplewski等[20]采用抗冲聚丙烯共聚物为主体,添加增黏树脂、增塑剂、稳定剂和抗氧剂得到一种可用于薄膜、非织造布等粘接的热熔胶。其中,按重量份数计,聚丙烯抗冲共聚物占2.5%-30%,软化点为80-140 ℃的增黏树脂约占60%,增塑剂占0.1%-5%。抗冲聚丙烯共聚物是由半结晶的丙烯均聚物和乙丙橡胶共混得到,其结晶相提供强度和刚度,橡胶相提供良好的耐冲击性和粘接性。 Jones等[21]采用丙烯聚合物(熔融指数MI> 150 g/10 min),和乙烯共聚物(熔融指数MI> 200 g/10 min)及无定形聚-α-烯烃为基体,制备了一种具有良好粘接性能的热熔胶。其中,乙烯共聚物选自乙烯与乙酸乙烯酯、丙烯酸烷基酯或甲基丙烯酸烷基酯的共聚物。该热熔胶可应用于装订、制鞋、一次性医疗卫生制品等领域。 Davis等[22]采用丙烯均聚物和聚-α-烯烃共聚物为基体,添加聚乙烯蜡或石蜡,制备了一种具有良好粘接性能的热熔胶。此类热熔胶可应用于金属聚合物薄膜粘接及皮革、箱包、装订、制鞋、一次性医疗卫生制品等行业。 Dehua等[23]采用聚乙烯为主体树脂获得热熔胶,具体配方是聚乙烯80-100重量份,抗氧化剂5-15份,环烷油50-70份,碳酸钙10-30份,增黏剂40-60份,按所述配方比例通过熔融共混制备了医用热熔压敏胶,该热熔压敏胶黏度高、工艺简单易操作、对环境无污染。 Moeller等采用至少一种乙烯基共聚物和至少一种C3-20的α烯烃聚合物为主体树脂,添加增黏树脂、增塑剂、稳定剂、填料或颜料,制备了一种用于包装材料、医疗标签或个人卫生用品的热熔胶[24]。Kanderski等[25]研制了一种热熔胶,包含4%-50%重量份丙烯无规共聚物,10%-60%重量份聚-α-烯烃共聚物,20%-65%增黏剂,5%-40%增塑剂,以及少量稳定剂和蜡。该热熔胶可用于一次性卫生用品、软包装、标签等。 2.3 热塑性弹性体热熔胶 热塑性弹性体热熔胶主要是指苯乙烯及其嵌段共聚物类热熔胶,主要成分是热塑性高分子弹性体,如苯乙烯-丁二烯-苯乙烯、苯乙烯-异戊二烯-苯乙烯等芳族乙烯-共轭二烯-芳族乙烯三嵌段共聚物,并添加少量增塑剂、增黏剂、填料及抗氧剂等[26]。 以芳族乙烯-共轭二烯-芳族乙烯三嵌段共聚物为基体聚合物的热熔胶由于可适应高速连续生产,并具有优异的初粘力而被广泛使用。研究表明,以特定的比例在芳族乙烯-共轭二烯-芳族乙烯共聚物中添加增粘剂、稀释剂和稳定剂,可得到在低温下粘接性能优异、适用于纸尿布等一次性医疗卫生产品的热熔胶。 Odar等[27]报道了一种适用于食品、药品及医疗包装标签的热熔胶的制备方法,基体聚合物由嵌段共聚物A和嵌段共聚物B组成,并添加一定量脂族-芳香共聚烃类树脂作为增黏树脂,以及一定量的石蜡类或环烷烃作为软化剂。其中,嵌段共聚物A的芳族乙烯单体单元含量为30%-50%,嵌段共聚物B的芳族乙烯单体单元含量为15%-25%。以硬质聚乙烯作为被粘接物, 23 ℃下测得其180°剥离强度大于380 N/m,可见该热熔胶对硬质聚乙烯材料具有良好的粘接力。 王宏[28]报道了一种医用黏性弹力绷带,采用热熔胶替代常规黏性弹力绷带上涂布的天然乳胶,该热熔胶基体聚合物选用苯乙烯-异戊二烯-苯乙烯、苯乙烯-丁二烯—苯乙烯、丙烯酸树脂、乙烯-乙酸乙烯共聚物中的一种,并配合少量的环保添加剂、食品级着色剂、填充剂等。使用该热熔胶的弹力绷带克服了传统天然乳胶产品容易霉变、对伤口有刺性、致敏性等缺陷,透气性好、感觉舒适、使用方便。 2.3.1 环氧化苯乙烯-丁二烯-苯乙烯/苯乙烯-异戊二烯-苯乙烯热熔压敏胶 利用苯乙烯-丁二烯-苯乙烯或苯乙烯-异戊二烯-苯乙烯中的双键进行环氧化反应,不仅能够提高分子的极性和内聚强度,改善与压敏胶其他组分的相容性,而且以此制备的热熔压敏胶在初黏力、剥离强度等性能上也会得到提高。 张军营等[29]采用40-60重量份的环氧化改性苯乙烯-二烯烃-苯乙烯嵌段共聚物热塑性弹性体为主体,使共聚物的部分双键转化为环氧基团,并配以增黏剂、增塑剂及抗氧剂,制备了一种医用热熔压敏胶,该热熔压敏胶是透明的,极性较强,还能负载药物,透湿性好,粘接皮肤时改善了舒适性。 热熔压敏胶经常作为药物的载体材料应用于经皮给药系统中,通过热熔胶配方可调节药物的释放速度。这种热熔胶应具有良好的生物相容性,对皮肤无刺激性,不引起过敏反应,具有够强的黏附力和内聚强度,化学性质稳定,对温度与湿气稳定,且有能粘接不同类型皮肤的适应性,能容纳一定量的药物和透皮吸收促进剂而不影响化学稳定性和黏附力[6]。Wang等[30]将苯乙烯-异戊二烯-苯乙烯,环氧化苯乙烯-异戊二烯-苯乙烯,C5树脂,矿物油和抗氧化剂熔融混合制备了苯乙烯-异戊二烯-苯乙烯/环氧化苯乙烯-异戊二烯-苯乙烯热熔压敏胶。实验表明,180°剥离强度会随环氧化程度的增加而提高,基于苯乙 烯-异戊二烯-苯乙烯的热熔胶剥离强度为0.9 kN/m,基于苯乙烯-异戊二烯-苯乙烯/环氧化苯乙烯-异戊二烯-苯乙烯-10(环氧化程度为10%)的热熔胶剥离强度为0.12 kN/m,基于苯乙烯-异戊二烯-苯乙烯/环氧化苯乙烯-异戊二烯-苯乙烯-30的热熔胶剥离强度为0.16 kN/m,基于苯乙烯-异戊二烯-苯乙烯/ ESIS-50的热熔胶剥离强度提高到了0.18 kN/m。此外,亲水性药物的释放特性也明显改善。因此,这种热熔压敏胶可作为亲水性药物载体应用于经皮给药系统中。 2.3.2 苯乙烯-乙烯/丁烯-苯乙烯/苯乙烯-(乙烯-丙烯)-苯乙烯热熔压敏胶 为提高压敏胶的耐氧化、耐紫外线和耐热性能,可对苯乙烯-共轭二烯嵌段共聚物进行适度加氢,使二烯链段氢化成聚乙烯和聚丁烯链段而成为苯乙烯-乙烯/丁烯-苯乙烯,或加入适量的丁苯橡胶。丁苯橡胶有利于分子间的交联,形成稳定的网络结构。苯乙烯-异戊二烯-苯乙烯三嵌段共聚物经氢化改性,获得苯乙烯-(乙烯-丙烯)-苯乙烯,其性能与苯乙烯-乙烯/丁烯-苯乙烯类似。 王峰等[31]将热塑性弹性体苯乙烯-异戊二烯-苯乙烯、热塑性弹性体苯乙烯-丁二烯-苯乙烯、热塑性弹性体苯乙烯-(乙烯-丙烯)-苯乙烯、环烷油KNH4010加入反应釜搅拌熔融,再加入C5/C9共聚石油树脂、C5石油树脂、松香树脂,最后加入抗氧剂BHT264搅拌混合,制备了一种热熔压敏型膏药基质胶。该膏药基质胶初黏力≥8#钢球,初黏性好,剥离强度大于10 N/ 25 mm,环球软化点≥65 ℃,耐老化性能好,内聚强度大,与非极性材料具有较好的黏合性能,有利于涂布。使用时膏药基质胶不对皮肤过敏而且载药量大,剥离后基质无残留。 总体而言,热塑性弹性体热熔胶主要应用于同皮肤接触的热熔压敏胶,对医用材料如导管等的粘接鲜见报道。 2.4 丙烯酸酯类热熔胶 Webster[32]报道了在热熔胶基体中引入氢键,可提高医用热熔胶的内聚能。例如用丙烯酸酯与甲基丙烯酸酯共聚物作为热熔胶的基体,由于在分子链间形成氢键提高了热熔胶的内聚能,从而提高粘接性能。据报道,目前临床上采用丙烯酸酯热熔胶即为含有丙烯酸正丁酯和甲基丙烯酸异丁酯的热熔压敏胶,对皮肤具有很高的粘接强度[32]。 在外科手术中,骶前出血的管理一直是具有挑战性的。Zhang等[33]采用氰基丙烯酸酯研制了一种可吸收止血纱布-氰基丙烯酸酯医用止血胶。该医用胶会于7-10 d内在身体表面降解,1个月左右在体内溶解成可溶性聚氰基丙烯酸正丁酯、甲酸,并随尿液排出体外。这是一种简便、易用的止血用胶,可有效防止骶前静脉大出血。 2.5 聚氨酯类热熔胶 医用热熔压敏胶由于需要接触生物基质如皮肤,因此除了要满足良好的胶黏性能和胶黏稳定性,还需要具有良好的透气性能,即能够透过由皮肤呼出的水汽进而防止水汽在皮肤与压敏胶间的界面累积,影响压敏胶的使用寿命。据此,可以通过提高压敏胶的水汽透过率来提高其使用寿命。Singh等[34]考察了不同交联剂对聚氨酯基压敏胶水蒸汽透过率的影响。研究结果表明,使用反应活性高的交联剂(如三聚氰尿酸三丙烯酸酯)得到的压敏胶的水汽透过率更低,这是有由于高活性的交联剂能提高交联产物的交联度,而高交联度使得胶黏剂的可流动性和表面浸润性降低,进而降低胶黏剂的黏性。 洪英等[35]提到了一种单组分湿固化反应性聚氨酯热熔胶,其研制的可反复洗涤、烘干、消毒的医用手术服和手术用布的面料,是由该聚氨酯热熔胶将外层、内层、中间保护层PU膜3层材料黏合制备而成。该热熔胶施胶温度为 90-120 ℃,黏度为4 000- 9 000 mPa·s,这种单组分湿固化反应性聚氨酯热熔胶,可耐受80 ℃的洗涤和pH值为10-11的消毒洗涤环境,80 ℃的烘干和及134 ℃的高温高压灭菌,且循环使用80次,粘接层仍然维持良好的粘结性,显示出优异耐洗性、耐高温灭菌性能和长使用寿命。 聚氨酯极性较大,因此聚氨酯类热熔胶对木材、皮革、金属等具有良好的粘接强度,但对非极性聚烯烃材料的粘接性较差,所以不适用于医用聚烯烃材料的粘接。"
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