With the progress of technology, PU synthetic leather has more excellent properties and wider application range than natural leather. It has also been applied in cutting-edge high-tech fields such as national defense, military industry, aerospace and so on. At present, the global market scale of PU synthetic leather is US $50 ~ 70 billion, mainly distributed in China, South Korea, Japan, South America, South Asia, Europe and other regions. China has nearly 2000 PU synthetic leather manufacturers, large and small (about 500 included in the statistics), ranking first in the world. It can be predicted that the research and development of PU synthetic leather will continue to progress due to the more updated needs of mankind. The future of PU synthetic leather will be colorful and brilliant.

So, how does PU synthetic leather develop and progress? In addition to the continuous innovation of production processes, equipment and substrates, perhaps more important is the development and innovation of additives.

The additives described in this paper include not only the additives and functional materials we often say, but also the surface treatment agents and special resins made by compounding or synthesizing additives and functional materials with ordinary PU resin. Its application scope includes additives for PU resin and PU synthetic leather.

Generally speaking, the innovation of PU synthetic leather is realized according to the following procedures:

Innovative additives are added to the Pu synthesis process: PU resin → + innovative additives + innovative base cloth and other substrates + filler + toner → manufactured by various innovative processes = PU synthetic leather.

It can be seen that the research and development of additives plays a vital role in the development of PU synthetic leather.

Classification of additives

Additives are generally divided into the following five categories:

1、 Solve the fault class. Such as defoamer, wetting agent, anti pinhole agent, leveling agent, wet fixing agent, DMF removal agent, uniform foaming agent, anti adhesion agent, interface fusion agent, tackifier, dispersant, etc. These materials play an important role in the manufacturing process of PU resin and PU synthetic leather. Without them, PU resin and PU synthetic leather cannot be produced normally;

2、 Improve processing performance. Such as: high peeling assistant, tear resistance assistant, anion (cation) ion penetrant, cell regulator, resin modifier, filler addition accelerator, liniment aid, modulus increasing agent, modulus reducing agent, special embossing assistant, assistant for sticking gold foil, rubbing assistant, etc. These materials are important components of PU resin and PU synthetic leather, which greatly change their physical properties and hand feel, so as to meet people's requirements;

3、 Add functional classes that PU material itself does not have. Such as: water splashing agent, antiseptic and anti mildew agent, flame retardant, wear-resistant and scratch resistant agent, waterproofing agent, high temperature anti-aging agent, leather assistant, yellowing resistant agent, cold resistant agent, water soluble agent, breathable absorbent material, radiation protection material, thermal insulation material, far infrared material, aromatic material, light emitting material, etc. With the addition of such materials, synthetic leather has the functions that Pu itself does not have, resulting in functional PU resin and functional PU synthetic leather to meet the needs of more fields of human beings;

4、 Adjust the surface effect and hand feel of PU synthetic leather. Such as: smooth agent, wax feel agent, special color developing feel agent, powder feel material, fog black material, coke feel material, sag feel material, soft material, special shrinkage material for leather, fog wax material, discoloration material, wet wax feel material and velvet feel material. These materials mainly provide special effects on the surface of PU synthetic leather to meet people's personalized needs and demand for fashion The pursuit of beauty.

5、 Surface treatment agent, special resin, etc. Traditionally, such materials are not in the category of additives. They are new materials made by compounding or synthetic process of additives and ordinary PU resin. It is generally used for PU synthetic leather surface or finishing layer, so that the synthetic leather has special surface effect and hand feel. According to the latest statistical standards of China Plastics Processing Association, in order to unify and standardize, we include surface treatment agents and special resins into the scope of additives. Such as all kinds of surface treatment agents such as fog surface, bright surface, velvet feeling, wax feeling, powder feeling and astringent feeling, and all kinds of special resins such as discoloration, cracking, Crazy Horse ventilation, water absorption, polishing, rubbing color, scorching and so on. With the development of PU synthetic leather like medium and high grade, personalization and functionalization, the use of surface treatment agents and special resins is increasing, and there are more and more varieties. It also accounts for an increasing proportion in the manufacturing cost of PU synthetic leather

一般来说，PU合成革的创新按如下程序实现：

创新的助剂加入PU合成过程中：PU树脂→+创新的助剂+创新的基布等基材+填料+**→经各种创新的工艺制造=PU合成革。

由此可见，助剂的研发在PU合成革的发展中起到至关重要的作用。 

助剂一般分以下五大类： 

一、解决故障类。如：消泡剂、润湿剂、防**剂、流平助剂、湿法用固色剂、脱DMF助剂、匀泡助剂、防粘剂、界面融合剂、增粘剂、分散剂等等。

二、改善加工性能类。如：高剥离助剂、抗撕裂助剂、阴(阳)离子渗透剂、泡孔调整剂、树脂改性剂、填料添加促进剂、助擦剂、增模量剂、降模量剂、特殊压花助剂、贴金箔用助剂、揉纹助剂等。

三、增加PU材料本身不具有的功能类。如：泼水剂、抗菌防霉剂、阻燃剂、耐磨耐刮剂、防水剂、高温抗老化剂、真皮味助剂、耐黄变助剂、耐寒剂、耐水解剂、透气吸水材料、防辐射材料、保温材料、防远红外材料、芳香材料、发光材料等等。

四、调节PU合成革表面效果及手感类。如：滑爽剂、滑蜡手感剂、特种展色手感剂、粉感材料、雾黑材料、焦感材料、垂感材料、柔软材料、真皮用特种收缩材料、雾蜡材料、变色材料、湿蜡感材料、绒感材这类材料主要是提供给PU合成革表面特殊的效果，以满足人们个性化的需求与与对时尚的、美的追求。 

五、表处剂、特殊树脂等。习惯上，这类材料本来并不在助剂范畴，它们是由助剂与普通PU树脂经过复配或合成工艺，制造出的新材料。一般用于PU合成革面层或涂饰层，使合成革具有特殊的表面效果及手感。