Petroleum Resin                                                                     

1. What is petroleum resin

Petroleum resin is a low molecular polymer obtained from cationic polymerization of C5 and C9 fractions, by-products of ethylene plant.

According to the different raw materials of petroleum resin can be roughly divided into C5 aliphatic petroleum resin with C5 distillate as raw material, C9 aromatic petroleum resin with C9 distillate as raw material, C5-C9 copolymer petroleum resin with C5 and C9 distillate as raw material, as well as dicyclopentadiene (DCPD) aliphatic petroleum resin and hydromodified petroleum resin 5 categories.

2.Properties of petroleum resin

The softening point of petroleum resin is generally 80-140℃, and the relative density is 0.970 ~ 0.975. The relative molecular weight is less than 3×10^3, insoluble in water, easily soluble in organic solvents, with low acid value, good adhesion, water and chemical resistance. And it has the characteristics of adjusting viscosity and good thermal stability. Therefore, petroleum resin can completely replace rosin resin and terpene resin for hot melt adhesive and pressure sensitive adhesive tackifier, play a role in improving wettability and improving adhesion.

The emergence of petroleum resins also solved the problems of limited sources of natural rosin and terpene resins, poor thermal stability, high price and easy aging. Moreover, the performance of rosin resin modified hot melt adhesive can be achieved by using petroleum resin with mass fraction of 60%.

3. Hot melt adhesive with petroleum resin performance indicators. 

In the preparation of hot melt adhesive, pressure sensitive adhesive. Only the matrix resin has a bonding force only when it is melted at a certain temperature, and once the temperature drops, the bonding will decline or even lose the bonding ability.

The addition of petroleum resin to the elastomer can not only improve the viscosity and wettability of the hot melt adhesive, but also improve the surface contact effect and the characteristic bonding performance. Obtain an ideal balance between viscosity, cohesion strength and interface strength.

The glass transition temperature of the mixture can also be increased by adjusting the rheology of the adhesive. Adjust the heat resistance temperature of hot melt adhesive to expand the use environment of hot melt adhesive.

As the amorphous petroleum resin produced by polymerization of complex monolefin and diolefin has no fixed melting point, the global softening point of the resin becomes an important factor in determining the properties of the resin.

Other physical properties of petroleum resin such as chroma, compatibility, melt viscosity, acid value and iodine value are also important factors in determining the application field of petroleum resin.

In addition to the above basic requirements, hot melt adhesive and pressure sensitive adhesive petroleum resin should also have good thermal stability, high shear strength, fast curing speed, uniform and stable filler dispersion and strong wettability.

There are many methods of preparing petroleum resin for hot melt adhesive and pressure sensitive adhesive abroad. A variety of modifiers are used, including styrene and its derivatives, terpenes, pinene, maleic anhydride and C9 fractions with complex composition, for the preparation of viscosifying resins.

4, The impact of compatibility

The compatibility between petroleum resin and elastomer is an important factor affecting the bonding strength of hot melt adhesive.

Good compatibility of viscosifying resin and elastomer can reduce the amount of energy storage film of colloid. Under certain stress, the colloid and the adhesive are fully bonded; If the two are incompatible, the amount of the energy storage film of the colloid will increase, and the bonding effect of the glue and the adhesive will be reduced.

The compatibility between tackifying resin and polymer matrix is a physical quantity related to the polarity of the two and the relative molecular weight of the resin.

The polarity is the same, the relative molecular weight is similar, the compatibility is good, such as aromatic polystyrene (PS) and natural rubber is incompatible, but with aromatic styrene butadiene rubber is compatible; Polyvinyl cyclohexane (PVCH) with an average molecular weight of 650 is very compatible with natural rubber, but PVCH with a molecular weight of 800 is not compatible with natural rubber.

In the preparation of hot melt adhesive, if the petroleum resin and the elastomer are incompatible or poorly compatible, the addition of petroleum resin in the system will easily cause the initial adhesion strength, adhesion strength and 180° peel strength of the pressure sensitive adhesive to decrease simultaneously.

5. Compatibility

Different kinds of petroleum resins, due to their large differences in molecular structure, only with the corresponding elastomers have good viscosity. In general, C9 petroleum resin prepared by cationic catalytic polymerization or thermal polymerization has high softening point, strong polarity and poor compatibility with natural rubber and styrene isoprene styrene block copolymer (SIS) containing conjugated diolefin structure elastomers.

It is not suitable for the viscosifier of these rubber adhesives, but it has good compatibility with styrene butadiene styrene block copolymer (SBS) and styrene butadiene rubber (SBR), and can be used as the viscosifier of this type of elastomer.

From the general compatibility range of elastomer and petroleum resin, SBS and SBR as elastomers, the best choice of C9 petroleum resin, C5-C9 copolymer petroleum resin as viscosifier; With SIS as elastomer, it is best to use C5 petroleum resin and C5-C9 copolymer resin as viscosifier.

6, Softening point impact

The softening point of petroleum resin is generally determined by the size of the relative molecular weight of the resin and the structure of the resin, which is about 40 ~ 50℃ higher than the glass transition temperature Tg.

The higher the relative molecular weight, the higher the proportion of ring structure and the higher the softening point of petroleum resin. The softening point of petroleum resin has great influence on the adhesion strength of hot melt adhesive.

The higher the softening point of the resin, the stronger the cohesion strength of the resin, the higher the adhesion strength of the adhesive, the higher the use temperature of the hot melt adhesive, and the wider the application range.

Therefore, the softening point of the viscosifying resin is required to be as high as possible when used, but too high softening point may improve the melt viscosity of the resin and reduce the infiltration ability of the hot melt adhesive, which is not conducive to the bonding of the hot melt adhesive.

If the melt viscosity is reduced by increasing the sizing temperature of the hot melt adhesive, it is easy to cause thermal degradation of the matrix resin due to high sizing temperature, which reduces the service life of the hot melt adhesive, and the softening point of the petroleum resin is generally between 80 and 130℃.

In addition, the softening point of petroleum resin also has a great influence on the curing speed and sizing speed of hot melt adhesive. Too high softening point is also easy to cause hardening and crust of hot melt adhesive.

Seven, melting viscosity, thermal stability of the melt viscosity of petroleum resin is often determined by the relative molecular mass, relative molecular mass distribution and structural characteristics of the resin.

The viscosity of polymers with monodisperse or narrow relative molecular mass distribution is higher than that of the same polymers with wide distribution under high shear velocity. Under the same injection and extrusion processing conditions. The fluidity of the sample with a wide relative molecular mass distribution is better than that with a narrow distribution.

The hot melt adhesive with low melt viscosity can be spread on the substrate better, increase the contact area between the hot melt adhesive and the substrate, improve the degree of infiltration of the hot melt adhesive to the bonded material, and help to improve the interface strength between the hot melt adhesive and the bonded material. But the melting viscosity is too low.

On the one hand, it may cause the settlement of the filler in the hot melt adhesive system, resulting in uneven distribution of the material composition, and on the other hand, it may cause the reduction of the cohesion strength of the hot melt adhesive, which is not conducive to bonding. The melting viscosity of petroleum resin should be 150 ~ 250mPas.

Outlook

At present, the world's petroleum resins are developing in the direction of bleaching, specialization, multipurpose and electron beam curing. Due to historical conditions and other reasons, China's viscosifying resins have been mainly rosin resins and terpene resins for a long time, while petroleum resins have developed slowly, and there is a big gap between the compatibility, softening point and other main quality indicators and similar foreign products.

In the modification of C5 petroleum resin, efforts should be made to develop new modifiers to prepare C5 petroleum resin with lower excellence, higher softening point and wider application range.

To increase the degree of rectification of C9 fraction and improve the chroma of C9 petroleum resin, we can obtain high quality and low price C9 and C5-C9 petroleum resin to meet the growing demand of petroleum resin for hot melt adhesive and pressure sensitive adhesive in our country.