Calcium-zinc Stabilizer

Calcium Zinc Stabilizers

Calcium – zinc stabilizers

:Calcium – zinc stabilizers

.Metal soaps are a type of heat stabilizers for PVC that are composed of a mixture of at least two metals, with one metal responsible for color preservation in the initial processing stages and the other metal responsible for long-term heat stability, such as calcium-zinc (Zn) stabilizers, which have been widely used in PVC applications for over 25 years. These materials are generally based on metal carboxylates and sometimes incorporate other elements such as aluminum or magnesium to enhance their performance when combined. In some PVC applications that require high heat stability, organic materials such as soybean oil epoxies or antioxidants can be used as co-stabilizers or auxiliary stabilizers to reinforce the heat stability of the material

.Due to its properties such as high transparency, good mechanical and electrical properties, and environmental compatibility, this heat stabilizer can be widely used in many flexible and rigid PVC applications

.This calcium-zinc stabilizer is a potential technical substitute for most other stabilizer systems, including lead and barium-zinc. Calcium-zinc stabilizers are more expensive than other metal soap stabilizers mainly due to the specialized stabilizers required to meet the specific needs of these applications. One important reason for replacing lead stabilizers with this stabilizer is that it is non-toxic and has been approved for use in contact with food according to the European Union’s food contact regulations

:Calcium-zinc heat stabilizers are used in the industry in three forms

powdered calcium-zinc:

. powdered calcium-zinc stabilizers, which are widely used as non-toxic and sanitary stabilizers, and are commonly used in food packaging, medical equipment, wires and cables, flooring, pipes and fittings, profiles, synthetic leather, and more. The thermal stability of powdered calcium-zinc stabilizers is not as good as lead salts and they have a specific oily property with poor transparency. In order to improve thermal stability and transparency, some additives are usually incorporated to enhance performance, including phenols, polyols, phosphates, beta-diketones, and other antioxidants

Liquid calcium-zinc:

.Liquid calcium-zinc stabilizers have an oily appearance and are light yellow in color. Generally, liquid calcium-zinc stabilizers have lower thermal stability compared to powdered stabilizers, but they have better transparency. These stabilizers require the addition of organic phosphates, antioxidants, and auxiliary stabilizers for optimal performance. Various solvents such as hydrocarbons and plasticizers are added to adjust viscosity. Liquid stabilizers are used in PVC products where the amount of plasticizer used is higher, typically above 10-20 phr (parts per hundred resin). In fact, the use of these stabilizers is common in soft and semi-rigid PVC applications. Liquid metal-mixed stabilizers are a suitable replacement for cadmium stabilizers in these applications. These stabilizers are formulated to achieve specific conditions such as proper initial color, long-term stability, good transparency, resistance to oxidation and degradation, and compatibility with all types of PVC, fillers, and pigments

Calcium-zinc paste:

.Calcium-zinc paste stabilizer is suitable for hygienic and odorless products that do not require transparency, and it is also approved for health. It is commonly used in medical accessories and hospital supplies such as oxygen masks, droppers, blood bags, medical injection equipment, as well as refrigerator gaskets, gloves, toys, hoses, and more. This stabilizer can be used as an alternative to Tin-based stabilizers in transparent food packaging or as a substitute for Tin carboxylates in PVC films. It is suitable for extrusion and injection applications, and adding epoxy-based soybean oil can enhance its properties

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Tin base stabilizer

استبلایزر قلعTin Base Stabilizer

PVC compounds usually have limited heat resistance. To bolster this resistance, tin base stabilizers are employed to counteract PVC degradation caused by heat during processing. Among the most effective stabilizers for enhancing PVC’s heat resistance are those based on tin.

Tin-based compounds can be classified into two categories

:Mercaptides and Carboxylates

. Mercaptide-type stabilizers of tin are suitable for rigid PVC packaging with a PVC coating:  These include

    • MTM (Methyl Tin Mercaptide)
    • BTM (Butyl Tin Mercaptide)
    • OTM (Octyl Tin Mercaptide)

.Carboxylate-type stabilizers :These include

      • MT (Methyl Tin Carboxylate)
      • BTC (Butyl Tin Carboxylate)
      • OTC (Octyl Tin Carboxylate)

Tin-based heat stabilizers not only provide excellent heat stability but also enhance the initial color. Moreover, due to the direct bonding of tin with methyl groups, they contribute to high transparency in PVC component production.

:Advantages and Disadvantages of Tin-Based Stabilizers

“Tin-based stabilizers” exhibit very high efficiency. They are suitable for various PVC processes, including size-reduced and rigid PVC, as well as injection and extrusion systems. However, one of the disadvantages of tin-based stabilizers is the odor resulting from the presence of sulfur in mercaptides, which leads to a stronger odor in soft PVC due to plasticizer migration. Additionally, the high cost of tin metal in these stabilizers is a concern.


One available solution to reduce the cost of tin-based stabilizers is to combine them with compatible materials. For example, tin and lead do not have compatibility, leading to material discoloration. Therefore, a heat stabilizer should be used that does not have undesirable interactions with tin-based heat stabilizers.

One of these compatible options is “Calcium Zinc Stabilizer,” which not only avoids undesirable interactions with tin-based stabilizers but also synergizes with them. This type of stabilizer is in the form of a paste-like metallic soap. It is suitable for medical and sanitary (clear) grades. Calcium Zinc paste provides long-term heat stability, excellent initial color, and transparency. This stabilizer can act as a co-stabilizer for tin-based mercaptides in transparent food packaging and PVC films. Its impact can be further enhanced by adding epoxy soybean oil.

For cost reduction in PVC compound production, cost-effective materials are used, in addition to the desired properties. Tin-based stabilizers are costly. To reduce costs, the dosage of tin stabilizer can be decreased, and it can be combined with a stabilizer like calcium zinc. Because calcium zinc is less expensive than tin, it can be a feasible option. However, the issue with tin stabilizers is not solely their high cost; tin-based mercaptide stabilizers also emit an undesirable odor due to the presence of sulfur in their structure. To address this issue, calcium zinc stabilizer can be added to tin stabilizers.

:Recommended Formulation

For PVC formulation, the ratio of adding tin-based stabilizers and calcium zinc paste (Payastab CZ 2370P, Payastab CZ 20) is variable. In other words, the lower the Shore A hardness of the material, the less tin-based stabilizer and more calcium zinc paste are added, and vice versa. For example, for materials with a Shore A hardness above 90, more tin-based stabilizer should be added, and calcium zinc paste can be used as a plasticizer and co-stabilizer in the compound.

For materials with a Shore A hardness of around 60-70, which are among the most common granules, approximately 100-150 grams of tin-based stabilizer and 1 to 1.2 kg of calcium zinc paste per 100 kg of PVC powder are needed. Therefore, the amount of tin-based stabilizer depends on the amount of plasticizer present in the PVC formulation. The more plasticizer is used, the less tin-based stabilizer is required.

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Epoxy soybean oil

Epoxy soybean oil ( Payaflex ESO 60 )  is a yellow liquid, and the less yellowish it is, the higher the quality of the oil. Soybean oil is converted to epoxy through oxidation. The higher the conversion of double bonds to epoxy, the higher the compatibility of this oil with PVC, and the iodine value of the oil decreases while the oxirene number increases. The suitable iodine value for epoxy soybean oil for 95% compatibility with PVC should be less than 6. If this value is less than 3, the compatibility is 100%.

Examples of applications for this oil include wall coatings, floor coverings, packaging for food and pharmaceuticals, wire and cable coatings, irrigation hoses, etc. This plasticizer is used in the formulation of both rigid and flexible PVC. Usually, in rigid PVC formulation, it is used Between 1-3 phr ,But in flexible PVC, it is used Between of 1-5 phr.

On the other hand, the amount of plasticizer needed can be measured based on the relative softening power of each plasticizer compared to Dioctyl phthalate (DOP), which is called the Substitute factor  ( SF ) . The value of this ratio for DOP is 1. If the value is greater than 1, it means that a higher amount of plasticizer is needed to achieve the same level of hardness as DOP. The replacement ratio of epoxy soybean oil is 1.1, which means that 10% more of this oil is needed to replace DOP.

:The role of epoxy soybean oil in the formulation

In PVC, in addition to its plasticizing role, it also acts as a stabilizer. Barium-Cadmium-Zinc ( Payastab  BCZ 2121  and Payastab BCZ 4141 ) exhibit good properties and performance as stabilizers. This oil has a synergistic effect alongside metallic stabilizers such as calcium-zinc ( Payastab CZ 2370P ) and Tin compounds (Payastab  MT19 ) .

This epoxy soybean oil is an inexpensive, non-toxic, environmentally friendly compound. So This plasticizer has resistance to heat, light, permeability, brittleness, decomposition rate, and migration.  as result It is considered a suitable substitute for plasticizers such as DOP (dioctyl phthalate) because DOP cannot be used in the packaging of food and pharmaceuticals due to its toxicity.

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