Isophorone chemistry solutions for resins and elastomers

VESTANAT® IPDI (isophorone diisocyanate) is a cycloaliphatic diisocyanate and characterized by its two reactive isocyanate groups comprising differences in reactivity (primary and secondary NCO groups). This leads to a high selectivity in the reaction with hydroxyl groups bearing compounds.

This unique property is advantageous for the processing of low viscosity prepolymers leading to a comparably low content of residual, monomeric diisocyanate at the same time. By choice of an appropriate catalyst (i.e. dibutyl tin dilaurate, DBTDL), the rate of conversion is increased, but also the degree of selectivity is further enhanced. The low viscosity of IPDI-based prepolymers allows for the reduction of solvents (VOC). The methyl groups attached to the cyclohexane ring make VESTANAT® IPDI and the corresponding derivatives widely compatible with resins and solvents.

The cycloaliphatic ring itself gives products based on VESTANAT® IPDI more rigidity and a high glass transition temperature. VESTANAT® IPDI is a colorless, low viscosity liquid with a solidification point of – 60 °C. Semi-finished products, e.g. NCO terminated prepolymers have low tendencies to crystallize but rather stay liquid and are easy processable. As a cycloaliphatic diisocyanate, VESTANAT® IPDI meets all requirements for the manufacture of light stable and weatherable polyurethanes also comprising excellent mechanical properties and chemical resistance.

Benefits

• Differently reactive isocyanate groups
• High selectivity
• Low viscosity of prepolymers
• Low residual monomer content in prepolymers
• High glass-transition temperature
• Low tendency for crystallization
• High NCO content
• Highest toughness and flexibility at low temperature

VESTANAT® H12MDI (main component is dicyclyhexylmethane-4,4’-diisocyanate.) is a cycloaliphatic diisocyanate with two cyclohexane rings. It resembles the hydrogenated analogue to MDI (methylendiphenylisocyanate). Nevertheless, properties of VESTANAT® H12MDI differ a lot from the aromatic MDI.

VESTANAT® H12MDI comprises two reactive isocyanate groups, both of secondary nature, showing nearly no differences in reactivity or pronounced selectivity. Due to this, semi-finished products, e.g. NCO terminated prepolymers show a broader molecular weight distribution resulting in an increased content of residual monomeric diisocyanate compared to VESTANAT® IPDI. Also, the viscosity of above mentioned products is significantly higher compared to similar products based on VESTANAT® IPDI.

VESTANAT® H12MDI leads to superior properties of finished products, i.e. outstanding resistance against aqueous media. Also the mechanical properties are on a high level, as well as abrasion resistance and solvent or chemical resistance. Due to the aliphatic nature of the diisocyanate, the produced elastomers or coatings benefit from an excellent light stability and weathering resistance.

To combine the advantages of high selectivity and low viscosity of IPDIbased prepolymers with high resistance of H12MDI-based prepolymers, VESTANAT® IPDI and VESTANAT® H12MDI can also be employed as a blend. The main applications of H12MDI are PUDs as well as TPUs, where high softening temperatures can be achieved.

VESTANAT® H12MDI is a colorless, low viscosity liquid but tends to crystallize at temperatures below 25 °C. Therefore the recommended storage temperature is about 30 °C. Colder storage conditions do not harm the product, but make heating respectively a liquefying and homogenization step necessary.

Benefits 

• Crystallinity/hard segment orientation
• Good chemical resistance
• Good mechanical properties
• High glass-transition temperature

VESTANAT® TMDI (trimethyl-hexamethylene diisocyanate) is a linear, aliphatic diisocyanate, also derived from the isophorone chemistry. Structural similarities to the hexamethylene diisocyanate (HDI) are obvious but due to the three methyl groups along the chain, the products, as well as the properties of (semi-) finished products, differ signifcantly compared to HDI.

Semi-finished products, e.g. NCO terminated prepolymers based on HDI, tend to crystallize due to the pure linear structure of the diisocyanate. Using VESTANAT® TMDI instead prevents the prepolymer from crystallization. VESTANAT® TMDI also shows a good compatibility with solvents and other raw materials used in polyurethane chemistry.

VESTANAT® TMDI comprises two primary reactive isocyanate groups offering a higher reactivity compared to VESTANAT® IPDI or VESTANAT® H12MDI. The similar structural surrounding is for both NCO functions leads to a low selectivity towards hydroxyl groups, but by choice of the right catalyst, the selectivity may be increased.

The linear structure, and thus the lack of cyclic structures of the VESTANAT® TMDI leads to comparably low viscosities of semi-finished products and a pronounced flexibility to the resulting polyurethanes. These properties are especially favorable for the production of UV curing resins.

The features of low viscosity and high flexibility make the VESTANAT® TMDI also an ideal combination partner for VESTANAT® IPDI or VESTANAT® H12MDI.

Similar to other (cyclo-) aliphatic diisocyanates VESTANAT® TMDI offers high light stability and excellent weatherability.

Benefits

• Linear structure
• High flexibility
• Low tendency to crystallization
• Good compatibility
• Low glass-transition temperature

VESTANAT® EP-DC 1241 is a heterofunctional monomer, comprising both, an isocyanate group and an acrylic function. It is based on isophorone diisocyanate (IPDI) and a hydroxyfunctional acrylate. VESTANAT® EP-DC 1241 is characterized by a very low content of di-adduct and monomeric IPDI. This allows for a very selective synthesis of the resin with low viscosities and low risk of gelation in case of highly branched polyols used as starting component.

VESTANAT® EP-DC 1241 is used to incorporate acrylic functions into PUR resins or NCO functions into acrylates to form lightfast and weatherable UV cure coatings or adhesives. Another option is to attach acrylate functionality to components/additives/activators to fix them to a cured coating/adhesive to avoid migration.

Benefits

• Very selective UV-resin manufacture
• Low content of diadduct
• Low content of residual diisocyanates

VESTANAT® EP-IPMS is a heterofunctional monomer, comprising both an isocyanate group and a trimethoxysilane group. With the isocyanate group, VESTANAT® EP-IPMS can be incorporated in classical polyurethane backbones. The methoxysilane groups add inorganic properties to these polymers and enhance compatibility with inorganic surfaces. Also, via hydrolysis condenstation reaction, the methoxysilane groups can be crosslinked to polysiloxane networks introducing very high crosslink density and chemical resistance to the polymer.

VESTANAT® EP-IPMS is mainly used for the synthesis of highly resistant coatings. The polysiloxane networks incorporate glass-like substructures into the polymer matrix and induce very high hardness as well as scratch resistance while the classical PUR backbone adds the needed flexibility to the coating. The siloxane curing reaction is induced by air humidity, thus storage stable 1K formulations are possible.

Benefits

• Links organic and inorganic substructures
• Allows moisture curing via hydrolysis condensation
• Polysiloxane networks offer superior hardness and chemical resistance

VESTAMIN® A 95 is a specialty building block for polyurethane dispersions (PUD) manufacturing. It combines the properties of an internal emulsifier and a chain extender.

VESTAMIN® A 95 is a ca. 50% aqueous solution of a sodium salt of an amino functional sulfonic acid. It comprises a primary and a secondary amino group. Because of the strong emulsifying power of the sulfonic group, lower amounts of VESTAMIN® A 95, e.g. compared to dimethylolpropionic acid (DMPA), are necessary to achieve a storage stable dispersion. Similar to DMPA, VESTAMIN® A 95 is an anionic emulsifier but in contrast to DMPA, dispersions or coating formulations may also be stable at slightly acidic conditions, offering more formulation freedom.

Being a sodium salt, VESTAMIN® A 95 does not release any neutralization amines that often come along with the DMPA process. Thus, the hydrophilicity is permanent. However, due to the low content of emulsifier, chemical or hydrolytically resistance of the coating is not affected too much. As the VESTAMIN® A 95 functions as an emulsifier and chain extender at the same time, the chain extension has to be done before the actual dispersing step; the complete build-up of the molecular weight of the resin has to be done in the organic phase. Usually this requires a high amount of organic solvent. In order to avoid large quantities of co-solvent, VESTAMIN® A 95 is typically incorporated into the backbone of PUDs manufactured via the acetone process. Since high content of co-solvent is unwanted in an environmentally friendly, water-borne coating, the solvent has to be removed. Acetone can be used as an easy-to-remove solvent.

Benefits

• Internal emulsifier and chain extender
• Strong hydrophylizing power
• Stabilizing power even in neutral or slightly acidic pH range
• No release of amines

As a second component for the reaction with di-/polyisocyanates mainly, OH functional components are most often used, or polyfunctional acrylates. Crosslinking of these acrylates with high Tg polyisocyanates, e.g. VESTANAT® T 1890 leads to very hard and brittle coatings. The brittleness can be easily reduced by combining the acrylate with some parts of OXYESTER® T 1136.

OXYESTER® T 1136 is polyester-based on only linear raw materials displaying a low viscosity without any solvents. Due to its linear structure OXYESTER® T 1336 acts as a flexibilizing agent in PUR coatings or elastomers.

The low viscosity of OXYESTER® T 1136 is also of advantage in the production of NCO terminated prepolymers that are used for moisture curing coatings in the construction area.

Benefits

• Liquid
• Low viscosity
• Flexibilizing
• No VOC
• Low color
• Good compatibility

VESTAMIN® A 139 is a cycloaliphatic bisaldimine. VESTAMIN® A 139 decomposes under air humidity to an amine, which may react with isocyanates very fast. It is therefore used as an accelerator for moisture curing systems. Curing times can be reduced significantly. However, due to a side reaction (by en/imine tautomerism) taking place over several days to a few weeks, viscosity increases during storage. So, the solution should be used as 2K approach and then has a very long pot life.

As VESTAMIN® A 139 reacts with water very fast, there is also an option to use it as a water scavenger in 2K PUR coatings to prevent the formation of gas bubbles by release of CO₂. The reaction of VESTAMIN® A 139 with water may also be beneficial when used in a 2K PUR coating. VESTAMIN® A 139 decomposes under the influence of air humidity and splits back a highly reactive diamine. This diamine subsequently reacts with NCO functions left in the coating very quickly and thus leads to a very fast curing

Benefits

• High reactivity with water
• Accelerator for moisture curing systems
• Water scavenger
• Fast curing 2K PUR