Of course, one of the key issues is the question of quality products. The high interest is a modified polyurethane foam fillers or additives. One of the most successful, popular and sealed modifiers polyurethane systems around the world are the polymer-polyol additive. They have become an integral part for the polyurethane foam.

In this article we want to know more about you, the polymer-polyol, their species, chemistry of receipt and functionality. So let’s begin.

Polymer-polyol – a viscous homogeneous suspension of white. When adding a polymer polyol in component A in the amount of 10-20% (by weight) increased carrying capacity in multiple strains and elasticity of the foam. In addition, increased longevity of the products of polyurethane foam, as well as decreasing the number of surface defects. Adding a polymer polyol in various proportions can control the physical and mechanical properties of polyurethane foams.

Achieving a set of properties is partly due to the fact that the polymer-modified polyol polyesters by chemical interaction with poliizotsionates form chemical skeleton (a grid of chemical bonds) with a rigid polymer fragments.

The main types of polymer polyols:

There are three classes of industrial modified polyols:

A) Polymer-polyols – dispersion poliakrilnitril, polystyrene (SAN).
B) with a dispersion of polyurethane polyols (PHD).
B) poly-isocyanate with polyols polidadditons (PIPA) – the dispersion of polyurethane.
D) Other-polymer polyols.

Now let a little more detail on each type of polymer polyols.

A) Polymer-polyols – dispersion polyacryl-nitrile, polystyrene (SAN).

This type of polymer polyol obtained by chain polymerization of styrene, acrylonitrile and polyester. Consider the basic chemical reactions that occur during free radical polymerization:

Description of the reactions:

1) First, free radicals are the result of rupture of the molecule of initiator, typically aliphatic azobis-nitrile compounds.
2) The radicals quickly react with monomer molecules with the formation of high molecular polymer. This stage is known as polymerization chain growth. This reaction differs significantly from the slow speed of polymerization of isocyanates and polyols.
3) The chain growth terminates the interaction of two different radical chain ends.
4) chain transfer agents react with the growing ends of the chains and terminate their growth. New radical terminal groups can initiate further chain growth polymers. Agents break the chain will stop the growth of the chain and not allow re-initiate the polymerization. These types of agents, eventually, slow down and stop the polymerization.

We can say that these types of chemical reactions is the basis for polymer-polyol. Depending on the type of polyester used in the synthesis of this type of polymer polyol has a viscosity in the range from 3000 to 7000 (to 9000) MPa • s. The resulting dispersion is used in the production of highly elastic foams by cold molding to improve the elasticity and strength products, as well as increasing their lifetime.

The first industrial polymer polyols were obtained using acrylonitrile as the sole monomer.

Background of acrylonitril:

1) Acrylic acts like hydrogen cyanide, causing tissue hypoxia, irritates skin and mucous membranes;
2) Refers to substances probably carcinogenic to humans (GN 1.1.725-98 “List of substances, products, production processes, household and environmental factors, carcinogenic to humans”);
3) A serious danger is the possibility of fire and explosion, low temperature ignition of acrylonitril indicates that the evaporation at room temperature is sufficient to form a combustible mixture with air;
4) Acrylonitril is capable of spontaneous polymerization under the influence of light and heat, which can lead to an explosion, even when it is stored in sealed containers;
5) The risk of fire and explosion increases deadly products of combustion such as ammonia and hydrogen cyanide.

Until now, virtually all imports of polymer polyols contain in the structure described above monomer. The question arises, why would you use in the production of polymer polyol is a substance? And because it is involved in the synthesis of the second monomer – styrene, which after synthesis is in the reaction mixture and it is very difficult to bring to the end. Acrylonitril in the amount of 10% helps to remove the residual styrene and get rid of the smell.

Our company took a different path, developing a new technology for polymer polyol, which is not used acrylonitril, and in the final product is no residual styrene.

B) with a dispersion of polyurea polyols (PDM).

Produced by stepwise polymerization. The first of these products was a polyol based on PDM (polyurea dispersion). DPM-polyols are dispersions of particles in the standard polyurea polyols. Such polyols are prepared in the reaction of diamine with diisocyanate in the presence of polyester with terminal hydroxyl groups. Mechanisms of instilling and polymerization are significantly different from those used for the polymer-polyol styrene and acrylonitril. The reaction of the base polyol to diisocyanate is slower than the reaction of diamine with diisocyanat, and their tendency to form small “seed” particles much smaller than that of polyols, styrene and acrylonitril. This leads to a weak implementation grafted polyols and to a deterioration in control of the formation of nuclei (active centers). The result is the larger particles and a wider distribution on polymer polyols, styrene and acrylonitril.

The viscosity of PDM-polyols higher than that of copolymer polyols, styrene and acrylonitrile. The first generation of PDM-polyols containing 20% of solid particles with a viscosity of 3000 to 3500 santiplaz. Newer products contain 28% solids.

B) Polizotsianatnye polyols with polidobavkami (PPPITS-polyol) – the dispersion of polyurethane.

PPPITS-polyols are similar to the PDM-polyol, but, unlike them, contain dispersed particles of polyurethane, formed in the reaction of isocyanate and alkanolamines such as triethanolamine. In general, amines are added to the standard polyols and the mixture quickly into contact, for example, toluene diisocyanate with rapid stirring. If you accelerate the reaction of organotin catalyst, it may be over in five minutes.

PPPITS-polyols are usually made and used by producers of foam.

D) Other-copolymer polyols

Polyols based on epoxy dispersions

There is information about the filled polyols based on the variances of cured epoxy resins. Stabilization of the particles occurs by using a specific polyol, which reacts with epoxy resin. It is reported that epoxy particles are more high-modulus fillers with improved ability to form hydrogen bonds.

Polyols based on the variance poliizotsianurata

This dispersion of particles in the standard poliizotsianuratov polyols. The particles prepared in the solvent, is dispersed in the polyols and the resulting solvent gives the finished product. Stabilization of the particles is achieved by the reaction of particles with monofunctional poliizotsianurata halogenated alcohol.

Polyols based on the dispersion of melamine

There is evidence to reduce the flammability of using copolymer-polyol-based melamine. However, the influence of particle size melamine on the physical properties of the finished foam has not been studied.

In Russia the most popular found the first type of polymer polyol (dispersion polyacryl-nitrile, polystyrene (SAN)) and is used mainly producing foam rubber and automobile seats. It is worth noting that many manufacturers still do not use the polymer-polyol additive, producing low quality products. The reluctance to apply the additive in their production due to several factors:

1) An import expensive additive that increases the value of the final product
2) Lack of awareness about the additive and its benefits
3) Do not want to make unnecessary movements and change the production process

Try to refute the above arguments:

1) address the issue with the appreciation of the final product will be the use of polymer-polyol supplements domestic production.
The scientific team developed and patented a new technology for polymer-polyol (trademark Laps 48-40). The market value of supplements is almost equal to the value Laprols 3603.

2) Summary of the benefits of supplements. Polymer polyol increases the carrying capacity in multiple strains, elasticity and durability of foam products. In addition, the reduced number of surface defects and, in total, increasing product quality. When added to component A in various proportions can control the physical and mechanical properties of polyurethane foam, for example, increase the hardness and elasticity at constant water content in the recipe and equal density foam.

3) Contrary to fears of producers to change anything in the manufacturing process, we simply give way to introduce additives: Polymer-polyol is added to the amount of 10-20% in the total mass is used instead of polyester, while the composition of other ingredients in the recipe does not change.

Author: Eganov Ruslan, Artyom Sevastyanov
Source: “Himtrast” CJSC