WO1997003962A1 - Imido peresters as initiators of polymerization processes - Google Patents

Abstract

A new group of imido peresters is provided which are represented by general formula (I), which are highly interesting for industrial applications, such as initiation of polymerization processes, polymer modification and cross-linking. For example, the compounds show excellent properties in producing high molecular weight polystyrene (co)-polymers, the cross-linking of rubbers and elastomers, and the curing of unsaturated polyesters. Also compositions are provided comprising at least one imido perester of formula (I) as well as methods of preparing these peresters.

Description

IMIDO PERESTERS AS INITIATORS OF POLYMERIZATION PROCESSES

A wide variety of peroxy compounds is known from the literature as initiators for polymer production. A fairly great number of these are commercially used. See, for example, the product catalogue of Akzo Nobel entitled "Initiators for polymer production", 1992, in which several dozens of initiators for radical polymerization have been mentioned under the trademarks Laurox^®, Lucidol^®, Perkadox^® and Trigonox^® . Other examples of commercially available initiators are included in the Akzo Nobel range of products sold under the trademarks Butanox^® and Cyclonox^®, respectively ¹⁾.

Commercially available initiators for polymer production may be classified in different chemical groups, which include diacylperoxides, peroxydicarbonates, dialkylperoxides, peroxyesters, peroxyketals, hydroperoxides, and ketone peroxides.

The present invention relates to a new group of peroxides which have highly interesting properties making them suitable for use in industrial applications. More particularly, the invention relates to imidoperesters having the following general formula:

wherein: n is 1, 2 or 3; and, if n is 1,

Y is C(R₄,R₅,R₅)

1) Laurox^®, Lucidol^®, Perkadox^®, Trigonox^®, Butanox^® and Cyclonox^® are registered trademarks of Akzo Nobel N.V. if n is 2 ,

Y is C₇_₂₂ alkylene having a tertiary structure at both ends, C_{7- 22} alkenylene having a tertiary structure at both ends, C_8-22 alkynylene having a tertiary structure at both ends, a group of the general formula: -C(CH₃)₂-C₆H_4-q-(R₇)_q-C(CH₃)₂- wherein q is 0 or 1 and R₇ is isopropyl, isopropenyl or 2-hydroxyisopropyl; if n is 3,

Y is 1,2,4-triisopropylbenzene-α,α',α"-triyl or 1,3,5-triisopropylbenzene-α,α' , α"-triyl;

R₁ and R₂ are independently selected from H, C_1-22 alkyl, C_2-22 alkenyl, C_2-22 alkynyl, C_6-22 aryl, C_7-22 aralkyl and C_7-22 alkaryl, which groups may be linear or branched and be substituted with one or more functional groups selected from hydroxy, halogen, ester, carboxy, amido, C_1-20 alkoxy, C_3-20 aryloxy, ketone, nitrile, C_1-20 alkylcarbonate, C_1-20 alkylsulfoxide, C_1-20 alkylsulfone, di(C_1-20)alkylphosphineoxide, di(C_1-20)alkylphosphonate, tri(C_1-20)alkylsilane and tri (C_1-20)alkoxysilane;

R₃ is C_1-22 alkylene, C_2-22 alkenylene, C_2-22 alkynylene, C_6-22 arylene, C_7-22 alkarylene, C_7-22 arylalkylene, C_3-22 cycloalkylene, which groups may be branched or linear and be substituted with one or more groups selected from hydroxy, halogen, ester, amido, C_1-20 alkoxy, C_6-20 aryloxy, ketone, nitrile, C_1-20 alkylcarbonate, C_1-20 alkylsulfoxide, C_1-20 alkylsulfone, di(C_1-20)alkylphosphineoxide, di(C_1-20)alkylphosphonate, tri(C_1-20)alkylsilane and tri(C_1-20)alkoxysilane;

R₄, R₅, R₆ are independently selected from C_1-22 alkyl, C_2-22 alkenyl, C_2-22 alkynyl, C_3-22 aryl, C_7-22 aralkyl, and C_7-22 alkaryl, which groups may be linear or branched and be substituted with one or more functional groups selected from hydroxy, halogen, ester, acid, amido, C_1-20 alkoxy, C_6-20 aryloxy, ketone, nitrile, C_1-20 alkylcarbonate, C_1-20 alkylsulfoxide, C_1-20 alkylsulfone, di(C_1-20)alkylphosphineoxide, di(C_1-20)alkylphosphonate, tri(C_1-20)- alkylsilane and tri(C_1-20)alkoxysilane; or R₄/R₅ may, together with the carbon atoms to which they are attached, form a 3 to 20 atoms membered ring, optionally substituted. The imidoperesters of the above formula (I) are new. They are highly interesting for industrial applications, such as initiation of polymerization processes, polymer modification and crosslinking. For example, the compounds show excellent properties in producing high molecular weight polystyrene (co)-polymers, the crosslinking of rubbers and elastomers, and in the curing of unsaturated polyesters.

Preferably, R₁ is hydrogen or C_1-6 alkyl and R₂ is C_1-6 alkyl. The preferred alkyl group is methyl or ethyl. Preferably, n is 1.

More specific examples of some of the imidoperester compounds which are useful in the present invention include, but are not limited to, the following: t-butylperoxy 2-citraconimidoacetate

t-amylperoxy 2-citraconimidoacetate

t-hexylperoxy 2-citraconimidoacetate

α-cumylperoxy 2-citraconimidoacetate

pinanylperoxy 2-citraconimidoacetate

p-menthylperoxy 2-citraconimidoacetate

2,4,4-trimethylpent-2-ylperoxy 2-citraconimidoacetate

t-butylperoxy 3-citraconimidopropionate

t-amylperoxy 3-citraconimidopropionate

t-hexylperoxy 3-citraconimidopropionate

α-cumylperoxy 3-citraconimidopropionate

pinanylperoxy 3-citraconimidopropionate

p-menthylperoxy 3-citraconimidopropionate

2,4,4-trimethylpent-2-ylperoxy 3-citraconimidopropionate t-butylperoxy 4-citraconimidobutyrate

t-amylperoxy 4-citraconimidobutyrate

t-hexylperoxy 4-citraconimidobutyrate

α-cumylperoxy 4-citraconimidobutyrate

pinanylperoxy 4-citraconimidobutyrate p-menthylperoxy 4-citraconimidobutyrate

2,4,4-trimethylpent-2-ylperoxy 4-citraconimidobutyrate

t-butylperoxy 6-citraconimidocaproate (=hexanoate)

t-amylperoxy 6-citraconimidocaproate

t-hexylperoxy 6-citraconimidocaproate

α-cumylperoxy 6-citraconimidocaproate

pinanylperoxy 6-citraconimidocaproate

p-menthylperoxy 6-citraconimidocaproate

2,4,4-trimethylpent-2-ylperoxy 6-citraconimidocaproate

t-butylperoxy 2-(4-citraconimidophenyl)acetate

t-amylperoxy 2-(4-citraconimidophenyl)acetate

t-hexylperoxy 2-(4-citraconimidophenyl)acetate

α-cumylperoxy 2-(4-citraconimidophenyl)acetate

pinanylperoxy 2-(4-citraconimidophenylacetate

p-menthylperoxy 2-(4-citraconimidophenyl)acetate

2,4,4-trimethylpent-2-ylperoxy 2-(4-citraconimidophenyl)acetate t-butylperoxy 2,6-bis(citraconimido)caproate

t-amylperoxy 2,6-bis(citraconimido)caproate

t-hexylperoxy 2,6-bis(citraconimido)caproate

α-cumylperoxy 2,6-bis(citraconimido)caproate

pinanylperoxy 2,6-bis(citraconimido)caproate

p-menthylperoxy 2,6-bis(citraconimido)caproate

2,4,4-trimethylpent-2-ylperoxy 2,6-bis(citraconimido)caproate t-butylperoxy 4-citraconimidobenzoate

t-amylperoxy 4-citraconimidobenzoate

t-hexylperoxy 4-citraconimidobenzoate

α-cumylperoxy 4 -citraconimidobenzoate

pinanylperoxy 4 -citraconimidobenzoate

p-menthylperoxy 4-citraconimidobenzoate

2,4,4-trimethylpent-2-ylperoxy 4-citraconimidobenzoate

t-butylperoxy 2-citraconimidobenzoate

t-amylperoxy 2-citraconimidobenzoate

t-hexylperoxy 2-citraconimidobenzoate

α-cumylperoxy 2-citraconimidobenzoate

pinanylperoxy 2-citraconimidobenzoate

p-menthylperoxy 2-citraconimidobeznzoate

2,4,4-trimethylpent-2-ylperoxy 2-citraconimidobenzoate

t-butylperoxy 2-dimethylmaleimidoacetate t-amylperoxy 2-dimethylmaleimidoacetate

t-hexylperoxy 2-dimethylmaleimidoacetate

α-cumylperoxy 2-dimethylmaleimidoacetate

pinanylperoxy 2-dimethylmaleimidoacetate

p-menthylperoxy 2 -dimethylmaleimidoacetate

2,4,4-trimethylpent-2-ylperoxy 2-dimethylmaleimidoacetate t-butylperoxy 3-dimethylmaleimidopropionate

t-amylperoxy 3-dimethylmaleimidopropionate

t-hexylperoxy 3-dimethylmaleimidopropionate

α-cumylperoxy 3-dimethylmaleimidopropionate

pinanylperoxy 3-dimethylmaleimidopropinate

p-menthylperoxy 3-dimethylmaleimidopropionate

2,4,4-trimethylpent-2-ylperoxy 3-dimethylmaleimidopropionate t-butylperoxy 4-dimethylmaleimidobutyrate

t-amylperoxy 4-dimethylmaleimidobutyrate

t-hexylperoxy 4-dimethylmaleimidobutyrate

α-cumylperoxy 4-dimethylmaleimidobutyrate

pinanylperoxy 4-dimethylmaleimidobutyrate

p-menthylperoxy 4-dimethylmaleimidobutyrate

2 ,4,4-trimethylpent-2-ylperoxy 4-dimethylmaleimidobutyrate t-butylperoxy 6-dimethylmaleimidocaproate (=hexanoate) t-amylperoxy 6-dimethylmaleimidocaproate

t-hexylperoxy 6-dimethylmaleimidocaproate

α-cumylperoxy 6-dimethylmaleimidocaproate

pinanylperoxy 6-dimethylmaleimidocaproate

p-menthylperoxy 6-dimethylmaleimidocaproate

2,4,4-trimethylpent-2-ylperoxy 6-dimethylmaleimidocaproate t-butylperoxy 2-(4-dimethylmaleimidophenyl)acetate

t-amylperoxy 2-(4-dimethylmaleimidophenyl)acetate

t-hexylperoxy 2-(4-dimethylmaleimidophenyl)acetate

α-cumylperoxy 2-(4-dimethylmaleimidophenylacetate

pinanylperoxy 2-(4-dimethylmaleimidophenylacetate

p-menthylperoxy 2-(4-dimethylmaleimidophenyl)acetate

2,4,4-trimethylpent-2-ylperoxy 2-(4-dimethylmaleimidophenyl)acetate

t-butylperoxy 2,6-bis(dimethylmaleimido)caproate

t-amylperoxy 2,6-bis(dimethylmaleimido)caproate

t-hexylperoxy 2,6-bis(dimethylmaleimido)caproate α-cumylperoxy 2,6-bis(dimethylmaleimido)caproate

pinanylperoxy 2,6-bis(dimethylmaleimido)caproate

p-menthylperoxy 2,6-bis(dimethylmaleimido)caproate

2,4,4-trimethylpent-2-ylperoxy 2,6-bis(dimethylmaleimido)-caproate

t-butylperoxy 4-dimethylmaleimidobenzoate

t-amylperoxy 4-dimethylmaleimidobenzoate

t-hexylperoxy 4-dimethylmaleimidobenzoate

α-cumylperoxy 4-dimethylmaleimidobenzoate

pinanylperoxy 4-dimethylmaleimidobenzoate

p-menthylperoxy 4-dimethylmaleimidobenzoate

2,4,4-trimethylpent-2-ylperoxy 4-dimethylmaleimidobenzoate t-butylperoxy 2-dimethylmaleimidobenzoate

t-amylperoxy 2-dimethylmaleimidobenzoate

t-hexylperoxy 2-dimethylmaleimidobenzoate

α-cumylperoxy 2-dimethylmaleimidobenzoate

pinanylperoxy 2-dimethylmaleimidobenzoate

p-menthylperoxy 2-dimethylmaleimidobenzoate

2,4,4-trimethylpent-2-ylperoxy 2-dimethylmaleimidobenzoate

The imidoperesters of the formula I can be made in conventional manner, for example by methods which are known in the art for the preparation of analogous compounds. Thus, in a typical procedure the compounds of formula (I) are prepared by reacting an acid halide containing maleimido derivative of formula (II), wherein R₁ to R₃ are as defined above and Z is a halogen, preferably chlorine, with a hydroperoxide Y-(OOH)_n, wherein Y and n are as defined above, preferably in a suitable solvent under alkaline conditions, essentially according to the following reaction scheme:

A suitable solvent is, for example, dichloromethane . Suitable bases include pyridine, triethylamine, LiOH, NaOH or KOH, etc. Preferably, the reaction is carried out under phase transfer conditions. The reaction conditions (e.g. temperature, reaction time) depend on the reactivity of the agents used and can be determined individually without inventive skill.

The starting materials for the preparation of the imidoperesters according to the present invention are either commercially available or they can be prepared in a manner known per se, e.g. for the preparation of analogous compounds.

The peresters can be prepared, transported, stored and applied as such or in the form of, e.g., powders, granules, pellets, pastilles, flakes, slabs, solid masterbatches, solutions, suspensions, emulsions and pastes. These formulations may optionally be phlegmatized, as necessary, depending on the particular perester and its concentration in the formulation. Which of these forms is to be preferred partly depends on the application for which it will be used and partly on the manner that it will be mixed.

Also, considerations of safety may play a role to the extent that phlegmatizers may have to be incorporated in certain compositions to ensure their safety. As examples of suitable phlegmatizers may be mentioned solid carrier materials such as inert plasticizers, solvents and inert diluents such as silicone oils, white oils, high boiling hydrocarbons such as isododecane, and water. The present peresters are well suited for use as initiators for polymer production, in particular the preparation of acrylic

(co)polymers, styrene (co)polymers, ethylene (co)polymers and vinylchloride (co)polymers, for use in the modification of polymers, in particular the degradation of polyolefins such as polypropylene and copolymers thereof, the crosslinking of polyolefins such as ethylene/propylene/diene polymers, polyethylene and copolymers thereof, the crosslinking of rubbers and elastomers, such as EPDM rubber, the dynamic crosslinking of blends of elastomers and thermoplastic polymers, the grafting of monomers onto polymers such as polyethers, polyolefins and elastomers, and the functionalization of polyolefins, as well as in the curing of unsaturated polyester resins (by processes such as SMC, BMC, pulltrusion, RTM and continuous laminating, etc).

In styrene bulk (co)polymerization, when using the peresters of the present invention, high molecular weight polymers can be produced at high polymerization rate. Accordingly, in one aspect the present invention comprises a process for the preparation of acrylic (co)polymers, ethylenic (co)polymers, styrenic (co)polymers and the curing of unsaturated polyesters, using the peresters represented in formula I .

In the present invention, polymerization is conducted by any conventional process, except that a specified radical polymerization initiator (or composition) is used. The polymerization processes may be carried out in the usual manner, for example in bulk, suspension, emulsion or solution. In the case of production of ethylene (co)polymers the reaction is usually carried out under high pressure, e.g. about 1000 to about 3500 bar. For the application of the peresters of the present invention in the modification of polymers, the perester may be brought into contact with the (co) polymer in various ways, depending upon the particular object of the modification process. The perester is generally mixed with the material to be modified, which material may be in any physical form including finely divided particles (flake), pellets, sheet, in the melt, in solution, or, in the case of an elastomer, in a plastic state, and the like. The amount of the initiator, which may vary depending on the application and, more in particular, on the polymerization temperature, the capacity for removing the heat of polymerization, and, when applicable, the kind of monomer to be used and the applied pressure, should be an amount effective to achieve polymerization. Usually, from 0.001-25% weight of perester, based on the weight of the (co) polymer, should be employed. Preferably, from 0.001-10% weight and most preferably from 0.001-5% weight of perester is employed.

The temperature for most reactions within the present invention is usually from about 0°C to about 450°C, preferably from about ambient temperature (20°C) and more preferably from about 50°C to about 350°C. When the temperature exceeds 450°C, the perester is spent in the initial stage of the reaction, making it difficult to attain a high conversion. For curing of unsaturated polyester resins at a temperature between ambient and 50°C the perester is preferably used in combination with an accelerator. Often a combination of two or more peroxides

(peresters) with different properties is used, for example peroxides with a higher and lower decomposition temperature

(dual cure system) . In order to reduce the amount of unreacted monomer, it is also .possible to conduct polymerization using a temperature profile, e.g. to perform the initial polymerization at about 90°C and then elevate the temperature above 115°C to complete the polymerization.

These variations are all known to the man skilled in the art, who will have no difficulty in selecting the reaction conditions of choice, depending on the particular process and the specific perester according to the invention to be used. An important criterion in selecting a suitable perester in accordance with the present invention is the half-life of the perester under application conditions.

During (co)polymerization, crosslinking or modification, the formulations may also contain the usual additives and fillers. As examples of such additives may be mentioned: stabilizers such as inhibitors of oxidative, thermal or ultraviolet degradation, lubricants, extender oils, pH controlling substances such as calcium carbonate, release agents, colorants, reinforcing or non-reinforcing fillers such as silica, clay, chalk, carbon black and fibrous materials such as glass fibers, plasticizers, diluents, chain transfer agents, accelerators and other types of peroxides. These additives may be employed in the usual amounts.

Suitable monomers for polymerization using the peresters according to the present invention are olefinic or ethylenically unsaturated monomers, for example substituted or unsubstituted vinyl aromatic monomers, including styrene, α-methylstyrene, p-methylstyrene and halogenated styrenes, divinylbenzene, ß-pinene, ethylvinylbenzene and vinylnaphthalene; ethylene; ethylenically unsaturated carboxylic acids and derivatives thereof such as (meth)acrylic acids,

(meth)acrylic esters, for example 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate and hydroxyethyl methacrylate; di, tri and tetra (meth)acrylates; ethylenically unsaturated nitriles and amides such as acrylonitrile, methacrylonitrile and acrylamide; substituted or unsubstituted ethylenically unsaturated monomers such as butadiene, isoprene and chloroprene; vinyl esters such as vinyl acetate and vinyl propionate; ethylenically unsaturated dicarboxylic acids and their derivatives including mono- and diesters, anhydrides and imides, such as maleic anhydride, citraconic (= methylmaleic) anhydride, citraconic acid, itaconic acid, nadic anhydride, maleic acid, fumaric acid, aryl, alkyl and aralkyl citraconimides and maleimides; vinyl halides such as vinyl chloride and vinylidene chloride; vinylethers such as methylvinylether and n-butylvinylether; olefins such as isobutene and 4-methylpentene; allyl compounds such as (di)allyl esters, for example diallyl phthalates, (di)allyl carbonates, and triallyl (iso)cyanurate.

Unsaturated polyester resins that can be cured by the imidoperesters according to the present invention usually include an unsaturated polyester and one or more ethylenically unsaturated monomers. Suitable polymerizable monomers include styrene, α-methylstyrene, p-methylstyrene, chlorostyrenes, bromostyrenes, β-pinene, vinylbenzyl chloride, divinylbenzene, diallyl maleate, dibutyl fumarate, triallyl phosphate, triallyl cyanurate, diallylphthalate, diallyl fumarate, methyl (meth)acrylate, n-butyl (meth)acrylate, ethyl acrylate, and mixtures thereof, which are copolymerizable with the unsaturated polyesters. The unsaturated polyesters are, for example, polyesters as they are obtained by esterifying at least one ethylenically unsaturated di- or polycarboxylic acid, anhydride or acid halide, such as maleic acid, fumaric acid, glutaconic acid, itaconic acid, mesaconic acid, citraconic acid, allylmalonic acid, tetrahydrophthalic acid, and others, with saturated and unsaturated di- or polyols, such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2- and 1,3-propanediols, 1,2-, 1,3- and 1,4-butanediols, 2,2-dimethyl-1,3-propanediols, 2-hydroxymethyl-2-methyl-1,3-propanediol, 2-buten-1,4-diol, 2-butyn-1,4-diol, 2,4,4-trimethyl-1,3-pentanediol, glycerol, pentaerythritol, mannitol, and others. The di- or polycarboxylic acids may be partially replaced by saturated di- or polycarboxylic acids, such as adipic acid, succinic acid and others, and/or by aromatic di- or polycarboxylic acids, such as phthalic acid, trimellitic acid, pyromellitic acid, 'isophthalic acid and terephthalic acid. The acids used may be substituted by groups such as halogen. Suitable halogenated acids include, for example, tetrachlorophthalic acid and tetrabromophthalic acid.

In the case of unsaturated polyester ("UP") resins, the application of the peresters according to the invention is confined to temperatures >0°C. Usually, a temperature of about 20-250°C and more preferably about 50-200°C, is employed. The heating time is generally between 0.1 and 30 minutes and, more preferably, between 0.5 and 5 minutes. The reaction is most preferably carried out in a moulding press or pulltrusion die.

Due to the crosslinkable imido group the use of imidoperesters according to the present invention in UP applications will result in reduced amounts of volatiles and the absence of benzene . In general, any (co)polymer comprising abstractable hydrogen atoms can be modified by the present process. For instance, polymers which tend to degrade include isotactic polypropylene, atactic polypropylene, syndiotactic polypropylene, alkylene/propylene copolymers such as ethylene/propylene random and block copolymers; propylene/diene monomer copolymers, propylene/styrene copolymers, poly(butene-1), poly(butene-2), polyisobutene, isoprene/isobutylene copolymers, chlorinated isoprene/isobutylene copolymers, poly(methylpentene), polyvinyl alcohol, polystyrene, poly(α-methyl) styrene, 2,6-dimethyl polyphenylene oxide and mixtures or blends of these polymers with one another and/or with other non-degradable polymers.

The imidoperesters according to the present invention may also be employed in the crosslinking of polymers such as low, medium and high density polyethylene, ethylene/alkene copolymers, ethylene/propylene/diene monomer terpolymers, chlorosulphonated polyethylene, chlorinated polyethylene, ethylene/ vinyl acetate copolymers, ethylene/propylene copolymers, propylene/diene monomer copolymers, brominated isoprene/isobutylene copolymers, partially hydrogenated butadiene/acrylonitrile copolymers, polyisoprene, polychloroprene, poly(cyclopentadiene), poly¬

(methylcyclopentadiene), polynorbornene, isoprene/styrene copolymers, butadiene/styrene copolymers, butadiene/acrylonitrile copolymers, acrylonitrile/butadiene/styrene terpolymers, polyacrylamides, polymethacrylamides, polyurethanes, polysulfides, polyethylene terephthalate, polybutylene terephthalate, copolyether esters, polyamides, silicone rubbers, fluor rubbers such as polyfluoralkoxyphosphazenes; allylglycidylether/epichlorohydrin copolymers and mixtures or blends thereof.

The (co)polymer modification process of the present invention is also useful for the grafting of monomers onto polymers or for the production of graft-copolymers . Examples of suitable (co)polymers which according to the present invention can be grafted by means of the imidoperesters are copolymers and block copolymers of conjugated 1,3-dienes, and one or more copoly- merizable monoethylenically unsaturated monomers such as aromatic monovinylidene hydrocarbons, halogenated aromatic monovinylidene hydrocarbons, (meth) acrylonitrile, alkyl (meth)-acrylates, acrylamides, unsaturated ketones, vinyl esters, vinylidenes and vinyl halides; ethylene/propylene copolymers and ethylene/propylene copolymers with other (poly) unsaturated compounds such as hexadiene-1,4, dicyclopentadiene and 5-ethylidenenorbornene; polyolefins such as polyethylene, polypropylene and copolymers thereof; and polyols including polyols which are essentially free of ethylenic unsaturation. Such polyols include polyalkylene polyether polyols having from 2-6 carbon atoms per monomeric unit and an Mn of 400-2000, polyhydroxyl containing polyesters, hydroxy-terminated polyesters and aliphatic polyols.

Suitable monomers for grafting onto the above-mentioned polymers using the imidoperesters of the present invention are olefinic or ethylenically unsaturated monomers such as: substituted or unsubstituted vinyl aromatic monomers including styrene and α-methylstyrene; ethylenically unsaturated carboxylic acids and derivatives thereof such as (meth) acrylic acids, (meth) acrylic esters and glycidyl methacrylate; ethylenically unsaturated nitriles and amides such as acrylonitrile, methacrylonitrile and acrylamide; substituted or unsubstituted ethylenically unsaturated monomers such as butadiene; vinyl esters such as vinyl acetate and vinyl propionate; ethylenically unsaturated dicarboxylic acids and their derivatives including mono- and diesters, anhydrides and imides, such as maleic anhydride, citraconic anhydride, citraconic acid, itaconic acid, nadic anhydride, maleic acid, aryl, alkyl and aralkyl citraconimides and maleimides; vinyl halogenides such as vinyl chloride and vinylidene chloride; olefins such as isobutene and 4-methylpentene; and epoxides. Finally, in another aspect, the present invention provides a polymerization process which can be employed to introduce functional groups into (co)polymers. This may be accomplished by employing an imidoperester of the formula I which contains one or more functional "R" groups attached thereto. These functional groups will remain intact in the free radicals formed by the peresters and thus are introduced into the (co)polymer. Conventional polymerization conditions and equipment may be used to achieve this object of the invention.

The invention is further illustrated by the following examples which are not to be construed as limiting the invention in any way. The scope of the invention is to be determined from the claims appended hereto.

Experimental

Synthesis examples Preparation of carboxylic acid containing citraconimides and dimethylmaleimides

General procedures A. A suspension of 0.5 mole of aminoacid and 0.51 mole of anhydride in 500 ml acetic acid is refluxed for 2 hrs . The water/acetic acid azeotrope is distilled off. The crude product is either used as such or recrystallized from a suitable solvent .

B. A mixture of 0.5 mole aminoacid, 0.51 mole anhydride and 1.5 g CF₃COOH in 500 ml. Q 5911 (bp. 140-165°C, ex. Shell) is refluxed using a Dean Stark trap until the theoretical amount of water is distilled off. The solvent is evaporated, and the crude product is either used as such or recrystallized from a suitable solvent .

Preparation of acid chloride containing- citraconimides and dimethylmaleimides

The carboxylic containing imide (0.2 mole) is suspended in 60 ml thionyl chloride. A catalytic amount of DMF (1-2 drops) is added to this suspension as a catalyst. The mixture is stirred overnight. The excess of thionyl chloride is distilled off under reduced pressure. The crude acid chloride is used as such for the next step.

Preparation of perester containing citraconimides and dimethylmaleimides

General Procedure

A. To a cooled solution (< 5°C) of 0.1 mole t-butylhydro- peroxide (TBHP) in 60 ml of a mixture of pyridine and dichloromethane (1:1), 0.1 mole of acid chloride dissolved in 20 ml dichloromethane is slowly added. During addition the temperature is kept below 5°C. The pyridine. HCl salt is filtered off and the solution is extracted twice with 20 ml water, twice with 30 ml 1.5% sulfuric acid and once with 30 ml of saturated sodium bicarbonate. The solution is dried over magnesium sulfate. The magnesium sulfate is filtered off and the solvent evaporated under reduced pressure. The perester is used as such.

B. To a cooled solution (≤ 5°C) of 0.1 mole TBHP in 50 ml dichloromethane, is added 0.1 mole NaOH as 33% solution in brine. To this two phase system is added 0.1 mole acid chloride in 30 ml dichloromethane, with vigorous stirring and keeping the temperature below 5°C. After addition the temperature is slowly rised to room temperature. The pH is kept at 9-10 during the reaction by dosing an aqueous solution of 25% NaOH. The mixture is stirred for another two hours. To this mixture is then added 50 ml dichloromethane and the layers are separated. The organic layer is extracted twice with 50 ml water and dried over magnesium sulfate, filtered and the solvent evaporated under reduced pressure. The perester is used as such. Materials Employed

Monomers :

Styrene (distilled) Initiators: - t-butylperoxy 2-citraconimidoacetate

- t-butylperoxy 3-citraconimidopropionate

- t-butylperoxy 4-citraconimidobenzoate

- t-butylperoxy n-butylfumarate

[Theoretical active oxygen content 6.55 %]

- 1,1-bis(t-butylperoxy)cyclohexane, 75 % in high viscous

mineral oil (Trigonox^® 22-E75, ex Akzo Nobel) . [Theoretical active oxygen content 12 . 29 %]

2 , 2 -bis (4 , 4 -bis [tert -butylperoxy] cyclohexyl ) propane ,

20 % in ethylbenzene , Perkadox 12 -AE20 ex Akzo Nobel

[Theoretical active oxygen content 11 . 41 %]

Methods used in the examples

Molecular weight and dispersity of the resins

Molecular weights and dispersity of the resins were determined by Gel Permeation Chromatography using polystyrene standards.

Conversion

Conversion was calculated from residual monomer content. Residual monomer concentrations were determined by gas chromatography on a solution of the polymer in dichloromethane using n-butylbenzene or t-butylbenzene as an internal standard.

Testing of imidoperesters as polymerization initiators A. Styrene mass polymerization

Example 1

0.375 meq t-butylperoxy 2-citraconimidoacetate was added to 100 g of styrene monomer. Mass polymerization of styrene was carried out in 3 ml brown glass ampoules in a thermostatted oil bath at 110 °C. Ampoules were removed from the oil bath after 2, 4, 6, and 8 hours. The samples were quenched in a 20 ml solution of dichloromethane containing Topanol^® OC (butylated hydroxytoluene) and n-butyl benzene as an internal standard. Styrene conversions as a function of time and molecular weight distibution after 8 hrs of polymerization are given in Table 1.

Example 2

As Example 1, but using 0.375 meq t-butylperoxy 3-citraconimidopropionate.

Example 3

As Example 1, but using 0.375 meq t-butylperoxy 4citracon- imidobenzoate.

Example 4

As Example 1, but using 0.750 meq t-butylperoxy 2-citraconimidoacetate.

Comparative example A

A thermal polymerization of styrene monomer (no initiator added) was carried out at 110°C using the procedure described in Example 1.

Comparative example B

As Example 1, but using a concentration of 0.375 meq 1,1-bis- (t-butylperoxy)cyclohexane in 100 g of styrene monomer.

Comparative example C

As Example 1, but using 0.375 meq t-butylperoxy n-butylfumarate in 100 g of styrene monomer. Comparative example D

As Example 1, but using a concentration of 0.375 meq 2,2-bis(4,4-bis[t-butylperoxy]cyclohexyl)propane in 100 g of styrene monomer. Comparative example E

As Example 4, but using 0.750 meq t-butylperoxy n-butyl fumarate in 100 g of styrene monomer.

The application of the imidoperesters in the curing of unsaturated polyesters was evaluated for temperatures >100°C. Due to the polymerizable imido group the imidoperoxide will result in reduced amounts of volatiles .

B. Curing of Unsaturated Polyesters

The curing of Unsaturated Polyester (UP) resins at elevated or high temperatures comprises Hot Press Moulding (HPM) such as SMC, BMC, ZMC and TMC, pulltrusion, continuous laminating and sometimes RTM. These techniques are described in "Unsaturated Polyester and Vinyl Ester Resins", Chapter 4 of the Handbook of Thermoset Plastics, ed. S. H. Goodman. Example 5

A BMC formulation was prepared by mixing the ingredients by means of a Z-blade Mixer during 5 minutes. After a thickening period of 7 days, the BMC was pressed at 150°C/75 bar pressure during 150 sec on a SMC-Reactomer (SMC Technologie Aachen) .

The BMC formulation consisted of :

- 100 parts of resin (e.g. Palatal^® P18 ex BASF)

- 200 parts of filler Durcal^® 5

75 parts of 6 mm chopped glass fibers

- 5 parts zinc stearate

5 parts of styrene

1.5 parts Luvatix^® MK35 (thickening agent)

1.5 parts of t-butylperoxy 4-citraconimidobenzoate The curing performance was measured by changes in displacement, temperature and pressure, measured by sensors in the mould cavity. The residual styrene was determined by extraction in dichloromethane followed by GC-analysis. The Maximum Flow Time (MFT) in sec, Minimum Moulding Time (MMT) in sec and Residual Styrene (RS) in % are mentioned in Table 2.

The foregoing examples were presented for the purpose of illustration and description only and are not to be construed as limiting the invention in any way. The scope of the invention is to be determined from the claims appended hereto.

Claims

Claims

A compound of the general formula I

wherein: n is 1, 2 or 3; and, if n is 1,

Y is C(R₄,R₅,R₆) if n is 2,

Y is C₇_₂₂ alkylene having a tertiary structure at both ends, C₇_₂₂ alkenylene having a tertiary structure at both ends, C_7-22 alkynylene having a tertiary structure at both ends, a group of the general formula: -C(CH₃)₂-C₆H_4-q-(R₇)_q-C(CH₃)₂- wherein q is 0 or 1 and R₇ is isopropyl, isopropenyl or 2-hydroxyisopropyl; if n is 3,

Y is 1, 2, 4-triisopropylbenzene-α,α',α"-triyl or 1,3,5-triisopropylbenzene-α,α',α"-triyl;

R₁ and R₂ are independently selected from H, C_1-22 alkyl, C_2-22 alkenyl, C_2-22 alkynyl, C_6-22 aryl, C_7-22 aralkyl and C_7-22 alkaryl, which groups may be linear or branched and be substituted with one or more functional groups selected from hydroxy, halogen, ester, carboxy, amido, C_1-20 alkoxy, C_6-20 aryloxy, ketone, nitrile, C_1-20 alkylcarbonate, C_1-20 alkylsulfoxide, C _1-20 alkylsulfone , di (C_1-20) alkylphosphineoxide , di ( C_1-20) alkylphosphonate , tri (C_1-20) alkylsilane and tri (C_1-20) alkoxysilane ; is C_1-22 alkylene, C_2-22 alkenylene, C_2-22 alkynylene, C_6-22 arylene, C_7-22 alkarylene, C_7-22 arylalkylene, C_3-22 cycloalkylene, which groups may be branched or linear and be substituted with one or more groups selected from hydroxy, halogen, ester, amido, C_1-20 alkoxy, C_6-20 aryloxy, ketone, nitrile, C_1-20 alkylcarbonate, C_1-20 alkylsulfoxide, C_1-20 alkylsulfone, di(C_1-20)alkylphosphineoxide, di(C_1-20)alkylphosphonate, tri(C_1-20)alkylsilane and tri(C_1-20)alkoxysilane,* R₄, R₅, R₅ are independently selected from C_1-22 alkyl, C_2-22 alkenyl, C_2-22 alkynyl, C_6-22 aryl, C_7-22 aralkyl, and C_7-22 alkaryl, which groups may be linear or branched and be substituted with one or more functional groups selected from hydroxy, halogen, ester, acid, amido, C_1-20 alkoxy, C_6-20 aryloxy, ketone, nitrile, C_1-20 alkylcarbonate, C^o alkylsulfoxide, C_1-20 alkylsulfone, di(C_1-20)alkylphosphineoxide, di(C_1-20)alkylphosphonate, tri(C_1-20)-alkylsilane and tri(C_1-20)alkoxysilane; or R₄/R₅ may, together with the carbon atoms to which they are attached, form a 3 to 20 atoms membered ring, optionally substituted.

2. The compound of Claim 1, wherein R₁ is hydrogen or C_1-6 alkyl, R₂ is C_1-6 alkyl and n is 1.

3. A stable peroxide composition comprising at least one organic perester selected from the compounds represented by formula I as defined in claim 1; and 10-99% by weight of one or more diluents selected from the group consisting of liquid phlegmatizers for the imido peroxides, plasticizers, solid polymeric carriers, inorganic supports, organic peroxides and mixtures thereof.

4. A process for the preparation of a compound of the formula I :

wherein Y, n and R_1-3 are as defined in Claim 1, which comprises reacting an acid halide containing maleimido derivative of formula II:

wherein n and R_1-3 are as defined in Claim 1, and Z is a halogen, with a hydroperoxide of the formula Y-(OOH)_n, wherein Y and n are as defined as in Claim 1.

5. A process according to Claim 4, wherein the halogen is chlorine.

6. A process according to Claim 4 or 5 , wherein the reaction is carried out in a suitable solvent .

7. A process according to any of Claims 4 to 6, wherein the reaction is carried out under alkaline conditions.

8. A process according to any of Claims 4 to 7, wherein the reaction is carried out under phase transfer conditions.

9. Use of an imidoperester of formula I :

wherein Y, n and R_1-3 are as defined in Claim 1, as an initiator of polymerization processes, in polymer modification processes, in the crosslinking of rubbers and elastomers, or in the curing of unsaturated polyesters.