NL1041959B1 - Catalyticaliy active radical scavenger based on benzylic functionalities - Google Patents

Abstract

An inhibitor to prevent oxidative radical degradation via a benzylic hydrogen abstraction mechanism, effective in an amount of less than 1% (w/w) based on the solid weight of substrate or substrate composition. The inhibitor comprises a conjugated benzyl moiety. The aromatic moiety can be selected from benzene, naphthalene, anthracene or phenanthrene. X H Qtz y

Description

Patent center

The Netherlands

(21) Application number: 1041959 © Application submitted: 29/06/2016

1041959

BI PATENT (51) Int. Cl .:

C09K 15/08 (2017.01) C08K 5/13 (2017.01)

(/ A Application registered: (73) Patent holder (s): 05/01/2018 Holland Novochem Technical Coatings B.V. in Houten. (43) Application published: (72) Inventor (s): (w) Patent granted: Alexander Maslow in Deventer. 05/01/2018 Erik Alexander Bijpost in Nieuwegein. (45) Patent issued: 25/01/2018 (74) Agent: O. Griebling in Tilburg.

© Catalytically active radical scavenger based on benzylic functionalities (57) An inhibitor to prevent oxidative radical degradation via a benzylic hydrogen abstraction mechanism, effective in an amount or less than 1% (w / w) based on the solid weight of substrate or substrate composition . The inhibitor comprises a conjugated benzyl moiety. The aromatic moiety can be selected from benzene, naphthalene, anthracene or phenanthrene.

NL BI 1041959

This patent has been granted regardless of the attached result of the research into the state of the art and written opinion. The patent corresponds to the documents originally submitted.

ref .: P 2016 NL 013

TITLE: Catalytically active radical scavenger based on benzylic functionalities

Introduction

It is generally known that many polymers are prone to degradation. Especially for durable outdoor products and rubber tires, the life time is limited due to influence of daylight, UV and ozone, initiating random radical reactions (metastable singlet oxygen as main initiator). Many attempts to prevent degradation, ranging from addition of metal deactivators, UV absorbers, peroxide decomposers, free radical chain stoppers to inhibitor regenerators etc. All these solutions have in common that it is a temporary inhibition, because they will lose activity in time as quenching / trapping occurs radically stoichiometrically.

Separate from polymers, a large group or monomers are prone to oxidation and / or radical-induced reactions. Known examples are styrene, divinylbenzene, acrylates, methacrylates, fatty acids etc. All these compounds have been stabilized to prevent any reaction upon storage. Usually hydroquinones, 2,6-di-tert-butyl-p-cresol (BHT) and the like are applied to stabilize the systems by quenching radicals. These compounds will oxidize to a thermodynamically stable compound. Hence, they act as stoichiometric radical scavengers.

Next to polymers and reactive monomers, many molecules, containing an active abstractable C-H donor, e.g. toluene, xylene, benzyl alcohol, natural oils and corresponding fatty acids will oxidize on aging. These raw materials are not always stabilized.

Proposed mechanism or radical-induced degradation

For polyalkylene radical-induced degradation one can distinguish two major pathways.

A. For linear polyalkylenes an oxygen radical will abstract a hydrogen radical from the polymer chain, forming a secondary reactive carbon radical. This species as such is very reactive, following mainly two pathways, viz. dimerization (cross-linking) and / or hydrogen abstraction from the matrix. Hardly any disproportionation or decomposition will occur. Owing to the dimerization the average molecular weight will increase in time, while the physical properties will change, such as brittleness.

B. For branched polyalkylenes, an oxygen radical will also include a hydrogen radical from the polymer backbone, forming a tertiary stabilized carbon radical. Predominantly an intramolecular disproportionation will take place, such as dezipping. The resulting degradation products will have a lower average molecular weight in time. Change, the physical properties of the polymer will change as well.

Invention

Surprisingly, Applicant found that radical-initiated degradation of polymers, monomers and reactive solvents can be prevented / inhibited catalytically. The inhibitor of choice comprises a conjugated benzylic moiety. Experiments have demonstrated that even under extreme conditions, eg storage under continuous air flow at 200 ° C for 30 minutes or under ozone treatment by gas high voltage UV lamp, the polymers or polymer compositions maintain its original properties, proven by viscosity, MEK rubbing or thin layers and minimal change in melting peak temperature T _peak (DSC).

Compounds, such as alkylated phenols, condensed phenol resins and triphenylmethane and derivatives can stabilize the radical-induced degradation reactions as follows (for clarity only a benzyl compound, eg alkylated phenol, is applied, but it is obvious for those skilled-in the-art that the mechanism is valid for most aromatic, including bi- and polycyclic aromatic, compounds, and bi- and polyphenols as well):

A. For linear polyalkylenes, upon oxidation highly reactive secondary alkyl radicals are formed. They abstract rapidly a benzylic hydrogen from the alkylated phenol. The linear polyalkylene polymer chain is re-manufactured and remains unaffected. The formed stable conjugated benzylic radical will distract in time a hydrogen radical from the matrix, reestablishing the thermodynamically stable catalyst. Moreover, the oxygen radical is deactivated by the alkylated phenol inhibitor, protecting the polyalkylene polymer to be attacked.

B. For branched polyalkylenes, upon oxidation more stable tertiary alkyl radicals are formed. Due to the structural properties, polyalkylenes will predominantly give in-cage (intramolecular) disproportionation / degradation. This is independent of the matrix. Cause, preventing this process the oxygen radical has been trapped before it attacks the polymer backbone via the highly reactive conjugated benzylic type or inhibitor via donation or a hydrogen radical. The formed stable conjugated benzyl radical will absorb in time a hydrogen radical from the matrix, usually another neutral benzyl type molecule or termination via benzyl dimer formation, reestablishing the catalyst property. It must be noted that intramolecular disproportionation strongly depends on temperature. Upon severe heating (> 200 ° C) for a longer period of time, this thermal degradation process will dominate and the effect of catalytic inhibition will be negligible. Lowering the temperature will strongly diminish this thermally induced degradation process.

The efficiency of the catalytic action to prevent radical-induced degradation is based on conjugated benzylic hydrogen abstraction, reactivity and stability as well as regeneration or the thermodynamically-favored benzylic hydrogen bond. All molecules with a benzylic hydrogen are in principle able to inhibit radical-initiated decomposition or polymers. It is obvious for those skilled-in-the-art that polycyclic aromatic compounds, such as naphthalenes, anthracenes and phenanthrenes, as well as bi- and polyphenols, will show similar reactivity and stability. Moreover, bisand tris benzyl substituted moieties can be applied as well as monodid and tribenzyl-substituted phenols and corresponding dimers, oligomers and resins. The higher the degree of conjugation the better the stabilization. Aromaticity is the best driving force for catalytic activity or inhibitors and maintenance / stability of the polymers. The inhibitors of choice contain the following functional moiety:

X H

Y

X and Y can be independently selected from hydrogen, alkyl, aryl, substituted alkyls, substituted aryls, polar functional groups, such as alcohol, mercapto, amines, ketones, aldehydes and carboxylic acid. The substitution on the aromatic ring can be ortho, meta or para. Higher-substituted benzene molecules are also available and can also meet the criteria for conjugated benzylic activity.

W and Z can be independently selected from hydrogen, alkyl, aryl, substituted alkyls, substituted aryls, polycylic aromatics, substituted polycyclic aromatics, polar functional groups, such as alcohol, amines, ketones, aldehydes and carboxylic acids.

Typical candidates meeting these criteria are alkylated phenols, phenol formaldehyde resins and triphenylmethane. They all comprise conjugated stabilized benzyl hydrogens, making them highly suitable for the catalytic inhibition or the oxidative radical-induced degradation.

It is clear for those skilled-in-the-art that the capacity of the catalytic inhibitor is concentration depend. To prevent alkyl radical formation side reaction the concentration of the catalyst should be equal or higher to the amount of the present oxygen radicals. The relative concentration is also dependent on reaction kinetics equilibria or the speed of deactivating the oxygen radical and the rate of reestablishing the catalyst property. The higher the amount of stabilizer the higher the stability and resistance of the polymer or other substrates under extreme oxygen radical attack induced conditions: sunlight, UV, temperature, oxygen, ozone, peroxide, metals and corresponding oxides.

Parallel to this invention, Applicant observed also excellent catalytic activity in radical scavenging or the conjugated allylic molecules. A typical example is itaconic acid. These compounds are capable of reestablishing their original form as well as due to the thermodynamically favored molecule structure. The conjugated allylic inhibitors can be combined with the benzylic compounds according to this invention. It is evident for those skilled-in-the-art molecules, including both an allylic moiety and a benzylic moiety, can show catalytic activity in radical scavenging as well.

Those skilled-in-the-art know that catalytic inhibition or radical-induced reactions can be applied to many processes. All polymers in general are susceptible to oxy radical-induced attack / decomposition, e.g., polyethylene, polypropylene, homo, co and terpolymers as well as functionalized polymers. With the new invention these polymers can be catalytically stabilized instead of using traditional scavengers. In line with this invention, also monomers and reactive solvents, susceptible to oxidation in time upon storage, can be stabilized.

It is evident that also oxygen-containing radicals can be stabilized analogously. Typical examples of such radicals are oxygen, peroxy, aryloxy, alkoxy, alkyl peroxy, arylcarbonate and alkylcarbonate radicals and ozone.

The shelf life of natural oils, fatty acids, food stuff, wine and other beverages can be increased gently by compounds according to this invention as well.

Examples

A 100 ml open glass vessel is charged with 10 grams of polymer. A defined amount or inhibitor is added and thoroughly stirred. The mixture is heated up to 200 ° C in a Gallenkamp box oven. When the polymer has reached the softening point, the mixture is thoroughly stirred again. Then a continuous air flow is passed through the oven, allowing the mixture to come into contact with oxygen. The physical properties are monitored in time. T _pea k values have been determined by DSC (Mettler DSC 12E, 80 ° C-250 ° C, rate: 10 ° C / min).

Polymer Inhibitor (% w / w) Observations 30 min @ 200 ° C Tpeak (° C) PP No heating after. 163 PP 0 Clear liquid, yellowing on top 153 PP 0.5% Substituted phenol formaldehyde resin Clear yellow liquid 164 PP 0.05% Substituted phenol formaldehyde resin Clear yellow liquid 164 PP 0.05% Itaconic acid + 0.05% Substituted phenol formaldehyde resin Clear yellow liquid 163 LLDPE No heating after. 124 LLDPE 0 Clear liquid slightly yellow 121 LLDPE 0.10% Substituted phenol formaldehyde resin Clear liquid slightly yellow 124 LLDPE 0.05% Itaconic acid + 0.05% Substituted phenol formaldehyde resin Clear liquid slightly yellow 124

It can be concluded from the examples that radical-induced degradation reactions can be inhibited by benzylic fragments containing compounds, such as substituted phenol formaldehyde resin. Even catalytic amounts or inhibitor added show the same activity. Upon mixing and / or combining these compounds with a functionalized allylic compound, such as itaconic acid, the catalytic radical scavenging effect is maintained as well.

Claims (15)

CONCLUSIONS An inhibitor to prevent oxidative radical degradation via a benzyl hydrogen withdrawal mechanism effective in an amount of less than 1% (w / w) based on the solid weight of substrate or substrate composition. A compound according to claim 1, wherein the inhibitor comprises a conjugated benzyl group X H Y X and Y can be independently selected from hydrogen, alkyl, aryl, substituted alkyl groups, substituted aryl groups, polar functional groups such as alcohol, mercapto, amines, ketones, aldehydes and carboxylic acid. The substitution on the aromatic ring can be ortho, meta or para. Higher substituted benzene molecules are also available and may also meet the criteria for conjugated benzyl activity. W and Z can be independently selected from hydrogen, alkyl, aryl, substituted alkyl groups, substituted aryl groups, polycyclic aromatic groups, substituted polycyclic aromatic groups, polar functional groups such as alcohol, amines, ketones, aldehydes and carboxylic acids. A compound according to claims 1 and 2, wherein the inhibitor comprises at least one hydroxyl substitution for X or Y. A compound according to any one of claims 1-3, wherein the inhibitor comprises one aryl functionality for substituent W or Z. A compound according to any one of claims 1-4, wherein the inhibitor is a condensed phenolic resin or a mono-, bis- or tri-substituted phenol. A compound according to any one of claims 1-5, wherein the benzene is replaced by a polycyclic aromatic compound, preferably naphthalene, anthracene or phenanthrene. A compound or mixtures according to any of claims 1-6, wherein the inhibitor further comprises a conjugated allylically-stabilized group. 5 The composition of claim 7, wherein the conjugated allylically stabilized molecule is selected from itaconic acid and citraconic acid. The composition of any one of claims 1-8, wherein the inhibitor is a mixture of at least two or more of the inhibitors. The composition of any one of claims 1-9, wherein the substrate is a polymer, oligomer, monomer or reactive solvent. The composition of any one of claims 1-10, wherein the Polymeric olefin groups. The composition of any one of claims 1 to 11, wherein the substrate is polyethylene, polypropylene, polybutadiene, polyisoprene, polyhexene or copolymers thereof or grafted polymers. The composition of any one of claims 1 to 12, wherein the substrate is selected from acrylate, methacrylate, styrene, divinylbenzene, natural oils or corresponding fatty acids, food, wine, and beverages. 25 A composition according to any one of claims 1-13, wherein the substrate contains a reactive C-H bond, preferably aromatic, selected from toluene, xylene, cumene, benzyl alcohol and benzaldehyde. The composition of any one of claims 1-14, wherein the The inhibitor is effective in less than 0.5% (w / w), preferably less than 0.2% (w / w), and even more preferably less than 0.05% (w / w) based on the total amount of solids.