What is the role of antioxidants in synthetic resins?
The industrial production of synthetic resins in the coatings industry is very different from scientific experiments in the laboratory and needs to be produced within a certain time frame, otherwise there is no industrial production.
The industrial production of synthetic resins for the coatings industry is very different from scientific experiments in a laboratory and needs to be completed within a certain period of time, otherwise there is no value in industrial production.
In order to speed up the reaction, it is necessary to add catalysts. In order to speed up the reaction, catalysts need to be added to achieve this.
Both synthetic and natural polymers can react with oxygen. Oxidation occurs at every stage of the polymer life cycle.
Oxidation occurs at every stage of a polymer’s life cycle, and the typical manifestation of oxidation can be summarised by the phenomenon of ageing.
Oxidation occurs at every stage of the polymer life cycle and the typical behaviour of oxidation can be summarised by the phenomenon of ageing. Theoretically, there are a number of methods that can be used to hinder thermal oxidation, with the addition of additives (antioxidants) being the most commonly used.
（The addition of additives (antioxidants) is the most common method.
What is a catalyst? What is the role of catalyst in synthetic resins?
Synthetic resins are based on a chemical reaction, and when a chemical reaction is applied to industrial production, the speed of the reaction plays an important role.
production, the reaction speed plays an important role. Many chemical reactions are slow, making it difficult to realise them in production.
Many chemical reactions are difficult to realise in production due to their slow reaction speed, and therefore have no practical application value. When adding a certain
substances, the speed of the chemical reaction will be accelerated significantly, which plays a role in promoting the reaction.
A chemical reaction changes its rate of reaction due to the participation of an external substance.
This extraneous substance is called a catalyst.
The catalyst comes into contact with the reactants and participates in the chemical reaction process, but after the reaction, it
withdraws from the reaction system and is not involved in the final products of the reaction. Catalysts can change the rate of a chemical reaction because they
rate of a chemical reaction because the catalyst changes the pathway and mechanism of the reaction.
The catalyst can be a compound or it can be a chemical compound. A catalyst can be a compound or a system of several compounds.
system of several compounds.
The catalysts involved in the synthesis of resins generally refer to substances that accelerate the rate of reaction.
substances, but catalysts that slow down the rate of reaction are also used in practice. Synthetic or natural
synthetic or natural polymers can react with oxygen, and in the case of synthetic resins, oxidation can
In the case of synthetic resins, oxidation may lead to a darkening of the resin’s colour and a decrease in its storage stability. In order to prevent or slow down this phenomenon
In order to prevent or slow down the occurrence of this phenomenon, it is common to add antioxidants.
This antioxidant actually slows down the reaction rate and is a catalyst for chemical reactions. Synthetic
The synthetic resin industry has listed this kind of substance separately and given a new definition—antioxidant.
In the production of synthetic resins, catalysts are selected with two main considerations in mind. ①Fasten the reaction rate.
Fast reaction rate. Some raw materials in synthetic resins have small reactivity, if they are introduced into the resin synthesis, the reaction rate is too slow.
If they are introduced into the resin synthesis, the reaction rate is too slow, and the reaction rate can be accelerated by adding catalyst, so that the reaction time of synthetic resin can be shortened within one hour.
By adding catalyst to speed up the reaction rate, so that the reaction time of synthetic resin can be shortened within a reasonable range. The reaction is directed. Synthesis
When synthetic resin carries out the desired chemical reaction, there are often other side reactions.
This will affect the process of the reaction and the quality of the final resin. By selecting a suitable catalyst, the selectivity of the catalyst can be utilised.
catalyst, the selectivity of the catalyst can be utilised to direct the reaction in the desired direction, thus controlling the reaction.
The purpose is to control the reaction by selecting a suitable catalyst and using its selectivity to guide the reaction in the desired direction.
‘% What is an antioxidant? What is the role of antioxidants in synthetic resins?
Antioxidants are substances that inhibit or slow down the rate of oxidation of polymer materials.
By its very nature, it is a catalyst that slows down the oxidation reaction. Synthetic resins are produced, stored and used,
Storage and use of synthetic resins in the process of production, storage and use, due to changes in temperature, contact with light and air, will cause the appearance, structure and properties of the resin.
During the production, storage and use of synthetic resins, changes in temperature and contact with light and air can cause changes in the appearance, structure and properties of the resin. The external causes of these changes are air,
The external causes of these changes are air, light and heat. These three external factors cause oxidation and thermal decomposition of synthetic resins.
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These three external factors cause oxidation and thermal decomposition of synthetic resins, which degrade the polymer and cause a series of changes. In order to inhibit and slow down the oxidative degradation of synthetic resins
In order to inhibit and slow down the oxidative degradation of synthetic resins and improve their value, a small amount of substances (i.e., antioxidants) that can inhibit or slow down the
In order to inhibit and slow down the oxidative degradation of synthetic resins and to increase their value, a small amount of a substance that can inhibit or slow down the degradation of synthetic resins is added.
On the one hand, the oxidation phenomenon affects the colour, appearance and storage stability of synthetic resins.
On the one hand, oxidation affects the colour, appearance and storage stability of the composite resin, which in turn causes thickening, chalking and surface cracking of the coating, thus affecting the quality of the product.
In principle, there are a variety of methods that can be used to slow down the thermal oxidation: ① Modification of resin structure, for example, with vinyl-containing resin.
For example, copolymerisation with vinyl-containing antioxidants; ② End-group sealing of molecular chains; ③ Addition of stabilisers such as antioxidants.
(iii) Addition of stabilising agents, such as antioxidants.
An antioxidant is a chemical aid that reduces the rate of oxidation and thus slows down the ageing of the polymer.
Antioxidants are chemical additives that reduce the rate of oxidation and thus slow down the ageing of polymers. The purpose of introducing catalysts in resin synthesis is to
The introduction of catalysts into resin synthesis: (i) slows down the rate of oxidation, which can reduce the colour of the resin; (ii) improves the storage stability of the resin, which in effect also improves the
The introduction of catalysts in resin synthesis can: (1) slow down the rate of oxidation reaction, so as to reduce the colour of the resin; (2) improve the storage stability of the resin, and in fact improve the stability of the coating.
‘& What substances can be used as catalysts for the synthesis of saturated polyesters?
The production of saturated polyester resins is based on the esterification of polyols and polyacids.
The catalyst should generally meet the following requirements: ① The catalyst is neutral and has no corrosive effect on the equipment; ② After the reaction is completed, the catalyst should meet the following requirements.
②After the reaction is completed, there is no need to separate the catalyst without affecting the quality of the final product.
(iii) It can significantly shorten the esterification reaction time; (iv) The choice of catalyst is good, so that the reaction can be carried out in the direction of esterification, and reduce the dehydration between polyols.
Good choice of catalyst can make the reaction proceed in the direction of esterification and reduce the side reactions such as dehydration and oxidation among polyols; ⑤ The water generated in the process of reaction will not make the catalyst fail.
Water generated during the reaction will not make the catalyst fail.
From the level of saturated polyester production technology at home and abroad, the choice of catalyst for polyester production tends to be of the same type.
At present, most of the catalysts for esterification reaction are organotin compounds.
compounds. Organic tin is an important product of tin deep processing, is a class of metal-organic compounds with important industrial significance.
It is a class of metal-organic compounds with great industrial significance. There are thousands of organotin compounds, of which dozens have industrial production value and are widely used.
There are thousands of organic tin compounds, of which dozens have industrial production value, with a wide range of uses. In the plastics industry, it can be used as heat stabiliser, and also as
polyester resin, alkyd resin, polyurethane resin production catalyst.
At present, the organotin used as polyester catalyst is generally butyltin oxide or a derivative of butyltin oxide.
Derivatives of butyltin oxide. At present, the most commonly used tin dibutyl dilauroate is a kind of
The most commonly used catalyst in China is dibutyltin dilaurate, which is a kind of esterification catalyst with high catalytic activity, anti-hydrolysis, low addition amount and high catalytic activity.
It is mainly used in the esterification reaction with the reaction temperature of 210~240℃. In the production process, the general addition amount is 72% of the total reaction volume.
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In the production process, the general addition amount is 005%～025% of the total reactants, and the suitable catalyst can be selected according to the production conditions of polyester resin.
It is possible to select a suitable catalyst according to the production conditions of the polyester resin and to determine the amount of catalyst to be added.
‘’ What substances can be used as antioxidants in the synthesis of saturated polyesters?
During production, storage, processing, and use, organic polymers react readily with oxygen, affecting the polymerisation of the polyester.
During production, storage, processing and use, the organic polymers may react with oxygen, thus affecting the properties of the polymer, such as dark colour, loss of transparency, or the mechanical properties of the coating film.
or affect the mechanical properties of the coating film (impact strength, adhesion, hardness, etc.). Adding Antioxidants to Polymers
Adding an antioxidant to a polymer is the easiest way to achieve this, as the antioxidant delays or prevents the oxidative or auto-oxidative process of the polymer.
The antioxidant can delay or prevent the oxidation or auto-oxidation process of the composite material, thus prolonging the service life of the material. Currently the main
varieties are amines, hindered phenols, phosphite and acid antioxidants.
At present, the types of antioxidants commonly used in polymer organics are as follows.
(1) amines Amine antioxidants is the earliest application of a class of antioxidants. Mainly aromatic
Derivatives of aromatic secondary amines, such as p-phenylenediamine, diaryl secondary amines, etc. Although this type of antioxidant has better effect, it is easy to deteriorate.
Although this kind of antioxidant has better effect, but it is easy to deteriorate and pollute, so it is generally used in the material which does not have high requirements on the colour of the finished product.
Therefore, they are generally used in materials with low colour requirements for the finished products.
(2) Phenols Phenolic antioxidants are a class of non-discolouring, non-polluting antioxidants, mainly used in materials with high requirements for product colour.
It is mainly used in the system with high requirements for product colour, and its structure mostly contains hindered phenol structure. Currently
Currently, thiobisphenol antioxidants are commonly used in the synthetic resin industry, such as 4,4bis(6 tert-butyl
m-tolyl) thiophenol (300), nonylphenyldithiophenol oligomer, tert-pentylphenyldithiophenol oligomer, etc. The production of light-coloured pine pine is a good idea.
Polymers, etc., the production of light-coloured rosin resin to be used in this type of antioxidant.
(3) Phosphite esters commonly used are trinonylphenyl phosphite (TNPP), triphenyl phosphite, triphenyl phosphite, tertiary amylphenyl phosphite, and so on.
Phosphorous acid triphenyl ester, phosphorous acid three (2,4 di-tert-butylphenyl) ester (168), etc., they have the ability to decompose peroxide to produce structural stability.
They have the decomposition of peroxides to produce structural stability of the role of substances, usually referred to as auxiliary antioxidants.
(4) Acidic antioxidants commonly used are boric acid, phosphite, hypophosphite, etc., of which hypophosphite is more effective.
The effect of phosphoric acid is better. Acid catalysis is characterised by a wide source of raw materials and mature technology.
However, the acidic antioxidant has strong acidity, which may cause corrosion to the equipment.
If saturated polyester resin is to use antioxidant in the production, the type of antioxidant used in fatty acid alkyd resin is similar to that used in fatty acid alkyd resin.
If antioxidants are used in the production of saturated polyester resins, they are similar to those used in fatty acid alkyd resins. From the actual production situation, can be phosphite antioxidant, acid antioxidant
From the actual production situation, phosphite antioxidant and acidic antioxidant can be used alone or combined with other types of antioxidants, and the result is good.
The effect is good.
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‘( How to select and use catalysts and antioxidants?
The saturated polyester resin synthesised by polyol and polyacid needs to be completed within a certain period of time.
If the esterification reaction time is too long, it is not cost-effective from the technical and economic point of view, especially for some special properties and small reactivity.
If the catalyst cannot be used to accelerate the reaction speed of raw materials with special properties and small reactivity, it is practically impossible to be used in industrial production.
In particular, some raw materials with special properties and small reactivity, if catalysts cannot be used to speed up the reaction, they cannot be used in industrial production. At present, the production of saturated polyester resins for coatings generally uses catalysts to speed up the reaction.
At present, the production of saturated polyester resin for coating generally uses catalyst to speed up the reaction.
The saturated polyester resin produced in the coating industry is mainly used in coil coating,
Wood paint and so on, these applications have high requirements for the colour of polyester resin, generally require the resin to achieve a colour ≤ ≤ ≤ ≤ ≤ ≤ ≤ ≤.
The colour of the resin is generally required to reach ≤ 1 (iron and cobalt colorimetry), close to water white. In order to ensure
To ensure that the colour is achieved, the addition of an antioxidant ensures that the polyester resin is protected by an inert gas in addition to inert gas protection during production.
That is to ensure the colour of polyester resin, but also to improve the stability of the resin in storage.
It is favourable to the improvement of the storage stability of the resin.
Care should be taken in selecting the catalyst for polyester resin synthesis:
① If the selected catalyst is added, is the acceleration of polyester resin esterification reaction rate (shortening of working time) under control?
① Whether the speed up of polyester resin esterification reaction (shortening of working time) is within the controllable range when adding the selected catalyst.
If the viscosity rises too fast, it can be controlled by adjusting the addition ratio or adjusting the catalyst type.
Although the catalyst is not involved in the final product of the reaction, it will remain in the system at the end.
Therefore, the compatibility with polyester resin should be taken into consideration, i.e. it should not affect the final resin properties.
(iii) If the use of a catalyst is finally confirmed, the catalyst should be used.
If the use of a catalyst is finally confirmed, it is not advisable to change the supplier easily. (iii) If the use of a certain catalyst is finally confirmed, generally do not change suppliers easily.
The same type of catalyst produced by different units may sometimes have big differences.
Without testing, do not use the same type of catalyst in the production of resin after direct substitution, so as not to cause difficulties in production control.
This may cause difficulties in production control.
Note on the selection of antioxidants for polyester resin synthesis:
① If adding the selected antioxidant, whether the reduction of the colour of polyester resin can reach the requirement, whether the effect of colour reduction can reach the requirement, whether the effect of colour reduction can reach the requirement, whether the effect of colour reduction can reach the requirement.
① If adding the selected antioxidant, whether the colour reduction of polyester resin can meet the requirements, in terms of the effect of colour reduction, there will be a deviation between the small test and the large-scale production, need to be carefully
② The antioxidant will leave residues at the end.
The antioxidant will be left in the system, so the compatibility with polyester resin should be considered, i.e. it should not affect the final resin.
Therefore, the compatibility with polyester resin needs to be considered, i.e., it should not affect the performance of the final resin. For example, the alkyd resin used for the production of self-drying alkyd enamels.
For example, if an acidic antioxidant is added to the alkyd resin used in the production of self-drying alkyd magnetic paints, the drying properties of the paint will eventually be affected to a certain extent.
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(iii) If a catalyst is used together with an
If catalyst and antioxidant are used at the same time, the properties of catalyst and antioxidant should be considered.
If catalyst and antioxidant are used at the same time, it is necessary to consider whether the properties of catalyst and antioxidant are in conflict with each other, and the situation and effect when they are used together. Some organotin catalysts and some acidic antioxidants are used together.
Some organotin catalysts and some acidic antioxidants may affect the transparency of polyester resins, resulting in a decrease in transparency.
The transparency of polyester resin will be affected when some organotin catalysts are used together with some acidic antioxidants, resulting in a decrease in transparency.
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| Sinanox® TNPP | CAS 26523-78-4 | Antioxidant TNPP |
| Sinanox® TBHQ | CAS 1948-33-0 | Antioxidant TBHQ |
| Sinanox® SEED | CAS 42774-15-2 | Antioxidant SEED |
| Sinanox® PEPQ | CAS 119345-01-6 | Antioxidant PEPQ |
| Sinanox® PEP-36 | CAS 80693-00-1 | Antioxidant PEP-36 |
| Sinanox® MTBHQ | CAS 1948-33-0 | Antioxidant MTBHQ |
| Sinanox® DSTP | CAS 693-36-7 | Antioxidant DSTP |
| Sinanox® DSTDP | CAS 693-36-7 | Distearyl thiodipropionate |
| Sinanox® DLTDP | CAS 123-28-4 | Dilauryl thiodipropionate |
| Sinanox® DBHQ | CAS 88-58-4 | Antioxidant DBHQ |
| Sinanox® 9228 | CAS 154862-43-8 | Irganox 9228 / Antioxidant 9228 |
| Sinanox® 80 | CAS 90498-90-1 | Irganox 80 / Antioxidant 80 |
| Sinanox® 702 | CAS 118-82-1 | Irganox 702 / Antioxidant 702 / Ethanox 702 |
| Sinanox® 697 | CAS 70331-94-1 | Antioxidant 697 / Irganox 697 / Naugard XL-1 / Antioxidant 697 |
| Sinanox® 626 | CAS 26741-53-7 | Ultranox 626 / Irgafos 126 |
| Sinanox® 5057 | CAS 68411-46-1 | Irganox 5057 / Antioxidant 5057 / Omnistab AN 5057 |
| Sinanox® 330 | CAS 1709-70-2 | Irganox 330 / Antioxidant 330 |
| Sinanox® 3114 | CAS 27676-62-6 | Irganox 3114 / Antioxidant 3114 |
| Sinanox® 3052 | CAS 61167-58-6 | IRGANOX 3052 / 4-methylphenyl Acrylate / Antioxidant 3052 |
| Sinanox® 300 | CAS 96-69-5 | Irganox 300 / Antioxidant 300 |
| Sinanox® 245 | CAS 36443-68-2 | Irganox 245 / Antioxidant 245 |
| Sinanox® 2246 | CAS 119-47-1 | Irganox 2246 / BNX 2246 |
| Sinanox® 1790 | CAS 40601-76-1 | Antioxidant 1790/ Cyanox 1790 / Irganox 1790 |
| Sinanox® 1726 | CAS 110675-26-8 | Antioxidant 1726 / Irganox 1726 / Omnistab AN 1726 |
| Sinanox® 168 | CAS 31570-04-4 | Irganox 168 / Antioxidant 168 |
| Sinanox® 1520 | CAS 110553-27-0 | Irganox 1520 / Antioxidant 1520 |
| Sinanox® 1425 | CAS 65140-91-2 | Irganox 1425 / Dragonox 1425 / Antioxidant 1425 / BNX 1425 |
| Sinanox® 1330 | CAS 1709-70-2 | Irganox 1330 / Ethanox 330 |
| Sinanox® 1222 | CAS 976-56-7 | Antioxidant 1222 / Irganox 1222 |
| Sinanox® 1135 | CAS 125643-61-0 | Irganox 1135 / Antioxidant 1135 |
| Sinanox® 1098 | CAS 23128-74-7 | Irganox 1098 / Antioxidant 1098 |
| Sinanox® 1076 | CAS 2082-79-3 | Irganox 1076 / Antioxidant 1076 |
| Sinanox® 1035 | CAS 41484-35-9 | Irganox 1035 / Antioxidant 1035 |
| Sinanox® 1024 | CAS 32687-78-8 | Irganox 1024 / Antioxidant 1024 |
| Sinanox® 1010 | CAS 6683-19-8 | Irganox 1010 / Antioxidant 1010 |