Patent Publication Number: US-2003225229-A1

Title: Dialkyl peroxide compound and process using such for initiating a chemical reaction

Description:
[0001] This application is a continuation of U.S. application Ser. No. 09/762,321, filed Mar. 12, 2001, which claims priority based on European Patent Application No. 98202663.5, filed Aug. 6, 1998, and International Application No. PCT/EP99/05578, filed Jul. 30, 1999. 
    
    
     
       [0002] The present invention relates to a compound for initiating a chemical reaction, in particular the polymerization of monomers, the crosslinking and/or degradation of polymers, the curing of polymers, the modification of polymers, and the production of polymers suitable for solvent based coating applications, to a formulation comprising such an initiator, and to a process for carrying out one or more of these chemical reactions utilizing such an initiator or initiator formulation.  
       [0003] In solution polymerization processes to make acrylic resins for example, t-alkyl peroxides such as t-butyl, t-amyl, and t-tetramethyl butyl peroxides are known as initiators. T-alkyl peroxides decompose on heating to form a t-alkyl oxy radical which acts as the polymerization initiator. This radical also undergoes a β-scission reaction to yield a ketone and an alkyl radical, whereby the relative stability of the initiating alkyl radical reduces hydrogen abstraction leading to polymers having low long chain branching, which yields a degree of control over the molecular weight and the molecular distributions of the polymers obtained.  
       [0004] According to a first aspect of the present invention, there is provided a process for carrying out one or more of the following chemical reactions:  
       [0005] polymerization of monomers, such as production of polymers suitable for solvent based coating applications and ethylene polymerization, and  
       [0006] modification of polymers, such as:  
       [0007] crosslinking and/or degradation of polymers;  
       [0008] curing of polymers,  
       [0009] and specifically a process for providing acrylic (co)polymers suitable for high solids coating applications, comprising the step of mixing an initiator, preferably tertiary-butyl-1,1,3,3-tetramethylbutyl peroxide (TBTMBP) or initiator formulation under reaction conditions with a predetermined reagent, preferably being a polymerizable acrylate monomer.  
       [0010] In the process according to the present invention, polymerization is conducted by any conventional process, except that the specified radical polymerization initiator (or initiator formulations) according to the present invention is used. The polymerization processes may be carried out in the usual manner, for example in bulk, suspension, emulsion or solution.  
       [0011] If ethylene is (co)polymerized, this is usually carried out under high pressure e.g. about 1000 to about 3500 bar and at high temperatures (up to 300° C.). The initiation of the polymerization by peroxides depends on the temperature and selected (cocktail of) peroxide(s). In such polymerizations, tert-butyl-1,1,3,3-tetramethylbutylperoxide offers unexpected advantages in comparison with a typically used peroxide like di-tert.butyl peroxide (DTBP, supplied as Trigonox® B by Akzo Nobel). More particularly, the tert-butyl-1,1,3,3-tetramethylbutylperoxide (TB-TMBP) offers the unexpected advantages of lower half-life temperatures and less aggressive alkyl radicals (less grafting), resulting in less long chain branching due to the lower processing temperature needed and/or higher polymer production (reactor output), and quicker polymerization.  
       [0012] In polymerization processes, optionally chain transfer agents are used. Suitable chain transfer agents include: butene-1, 3-methyl butene-1, 2-ethyl hexene-1, octane-1, hydrogen, carbon tetrachloride, p-xylene, propionaldehyde.  
       [0013] The amount of the initiator, which varies depending 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% by wt of initiator, based on the weight of the (co)polymer, should be employed. Preferably, from 0.001-15% by wt of initiator is employed.  
       [0014] The polymerization temperature for most reactions within the present invention is usually ambient to 350° C., preferably 40° to 300° C.  
       [0015] It is also possible to conduct polymerization using a temperature profile, e.g., to perform the initial polymerization at below 100° C. and then elevate the temperature above 100° 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 polymerization process and the specific radical polymerization initiator to be used.  
       [0016] Suitable (co)monomers for polymerization, e.g. high solids solvent based coating resin using the initiators 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; ethylene; ethylenically unsaturated carboxylic acids and derivatives thereof such as (meth)acrylic acids, (meth)acrylic esters, acrylic acid, methoxyethyl acrylate, dimethylamino (meth)acrylate, isobutyl methacrylate, lauryl methacrylate, stearic methacrylate, allyl methacrylate, 2-hydroxypropyl (meth)acrylate, methacrylamide, e.g. butyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate and glycidyl (meth)acrylate, methyl (meth)acrylate and ethyl (meth)acrylate; 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 and vinylester of versatic acid; 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, 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 ethylene isobutene and 4-methylpentene; allyl compounds such as (di)allyl esters, for example diallyl phthalates, (di)allyl carbonates, and triallyl (iso) cyanurate.  
       [0017] An important requirement of a high-solids solvent based coating resin, other than low molecular weight, is that it must contain chemically active groups (usually hydroxyl or carboxyl functionality) in order to undergo molecular weight build-up and network formation during the final crosslinking (curing) reaction where compounds such as melamine or isocyanates are used as the curing agents. Polymers suitable for use in high-solids coating formulations, normally have a hydroxyl content of from about 2 to about 7% by wt. To prepare a polymer which has a hydroxyl content of about 2-7% by wt, a sufficient amount of hydroxyalkyl acrylate or methacrylate is used (normally, 20-40% by wt of the monomer composition).  
       [0018] Specific examples of hydroxyalkyl acrylates and methacrylates that can be used to prepare polymers suitable for solvent based coating applications include: 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, and the like.  
       [0019] Specific examples of alkyl acrylates and methacrylates that can be used to prepare polymers suitable for solvent based coating applications include: methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and the like.  
       [0020] Other monomers, such as styrene, para-methyl styrene, acrylic acid, methacrylic acid, or vinyl acetate, can also be used in the preparation of polymers suitable for solvent based coating applications (i.e. control of monomer costs and/or to obtain a balance of film properties). Chain transfer agents can be used, for example thiols, disulphides, or CCl 4 .  
       [0021] The polymerization process of the present invention can be employed to introduce functional groups into (co)polymers. This may be accomplished by employing a peroxide which contains one or more functional groups attached thereto. These functional groups such as hydroxyl and acid groups will remain intact in the free radicals formed by the peroxides and thus are introduced into the (co)polymer. Conventional polymerization conditions and equipment may be used to achieve this object of the present invention.  
       [0022] The initiators according to the invention may be used as a curing agent for unsaturated polyesters and unsaturated polyester resins. The initiators according to the present invention usually include an unsaturated polyester and one or more ethylenically unsaturated monomers.  
       [0023] Suitable polymerizable monomers include styrene, alfa-methylstyrene, p-methylstyrene, chlorostyrenes, bromostyrenes, 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 unsaturated polyesters 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, 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, wherein the di- or polycarboxylic acids are optionally partially replaced by saturated di- or polycarboxylic acids, such as adipic acid, succinic acid, and/or by aromatic di- or polycarboxylic acids, such as phthalic acid, trimellitic acid, pyromellitic acid, isophthalic acid, and terephthalic acid, and wherein the acids used are optionally substituted by groups such as halogenated acids including tetrachlorophthalic acid and tetrabromophthalic acid.  
       [0024] The initiators of the present invention are suited for use in the modification of polymers. More particularly, these peroxides can be employed in processes for the crosslinking or degradation of polymers or the grafting of monomers onto polymers such as polyolefins and elastomers, and the functionalization of polymers in the case of functional group-containing peroxides of the present invention.  
       [0025] In general, the initiator may be brought into contact with the (co)polymer in various ways, depending upon the particular object of the modification process. The polymer material may be in the molten state, in the form of a solution, or, in the case of an elastomer, in a plastic state or in any physical form including finely divided particles (flakes), pellets, film, sheet, in the melt, in solution and the like. Polymers may also be in the liquid form, e.g. liquid rubbers.  
       [0026] In general, any (co)polymer comprising abstractable hydrogen atoms, in particular polyolefins, can be modified by the present process.  
       [0027] The amount of initiator used in the modification process of the present invention should be an amount effective to achieve significant modification of the (co)polymer when treating a (co)polymer. More particularly, from 0.001-15.0% by wt of peroxide, based on the weight of the (co)polymer, should be employed. More preferably, from 0.005-10.0% by wt is employed. Most preferably, an amount of 0.01-5.0% by wt is employed.  
       [0028] Polymers suitable for solvent based coating applications are prepared by solution polymerization in which select monomers are blended with solvent, initiator according to the present invention, and, optionally, a chain transfer agent, and heated to about 90°-200° C. for 0.1-20 hours.  
       [0029] Low solvent to monomer (s/m) ratios are used to conduct the polymerization in order to achieve the desired solvent based content required for high-solids coating applications, typically, 25 to 95% by wt solids. The solvent to monomer ratios generally used are in the range of (3/1) to (0.05/1).  
       [0030] Polymerization is generally conducted at or below about the reflux temperature of the solvent or mixture of solvents.  
       [0031] Adhesion promoting monomers can also be used in the preparation of polymers suitable for solvent based coating applications, such as methacrylic acid, diethylaminoethyl methacrylate, di-methylaminoethyl methacrylate, tertiary-butylaminoethyl methacrylate, 3-(2-methacryloxyethyl)-2,2-spirocylohexyl oxasolidene, and the like.  
       [0032] Examples of solvents which are used to prepare polymers suitable for solvent based coating applications include: toluene, xylene, ethyl acetate, n-butyl acetate, acetone, methyl ethyl ketone, methyl n-amyl ketone, ethyl alcohol, benzyl alcohol, oxo-hexyl acetate, oxo-heptyl acetate, propylene glycol methyl ether acetate, mineral spirits, and other aliphatic, cycloaliphatic and aromatic hydrocarbons, e.g. Solvesso 100®, esters such as Exxate 700®, ethers, ketones, and alcohols which are conventionally used. Commercially, the primary considerations in the selection of a suitable solvent are cost, toxicity, flammability, volatility, and chain-transfer activity.  
       [0033] According to another aspect of the present invention, there is provided a process for carrying out one or more of the chemical reactions:  
       [0034] provision of acrylic co-monomers suitable for high solids coating applications,  
       [0035] the polymerization of monomers,  
       [0036] the modification of polymers, such as crosslinking and/or degradation of polymers, and  
       [0037] the curing of polymers,  
       [0038] comprising the step of contacting under reaction conditions, an asymmetric, saturated peroxide compound having the general formula:  
       R—O—O—R1  
       [0039] wherein R and R1 are selected from the group consisting essentially of:  
       [0040] a tertiary-alkyl group having a carbon chain length of about C4 to about C22,  
       [0041] C(CH 3 ) 3 ,  
       [0042] C(CH 3 ) 2 (CH 2 ) n —C 6 H(5-m)—(R2)m, wherein n=0, 1 or 2 and m=0, 1, 2 or 3 and wherein R2=an isopropyl or 2-hydroxy-isopropyl group,  
       [0043] a tertiary cycloalkyl group having a carbon chain length of about C4 to about C22,  
       [0044] a tertiary-alkylcycloalkyl group having a carbon chain length of about C6 to about C22,  
       [0045] a tertiary-cycloalkylalkyl group having a carbon chain length of about C4 to about C22,  
       [0046] with the proviso that R1 is not equal to R when R is selected from the group consisting essentially of:  
       [0047] C(CH3)3,  
       [0048] C(CH3)2(CH2) n —C6H(5-m)—(R2) m , wherein n=0 and m=0, and;  
       [0049] excluding the initiator R—O—O—R1 when R is a C(CH3)3 group and R1 is equal to C(CH3)2(CH2) n —C6H(5-m)—(R2) m , wherein n=0 and m=0, and further excluding tertiary-butyl-peroxide when polymerizing styrene and ethylene.  
       [0050] The inventors have found on utilizing such an initiator obtained via this process, that polymers are obtained with improved properties, for example having lower molecular weights and lower molecular weight distributions than polymers obtained with known initiators.  
       [0051] The inventors theorize that during polymerization of acrylic resins, the initiators according to the present invention provide less generation of decomposition products that influence the reflux temperature and an increased generation of free radical initiating species. This may be explained by a synergistic combination of the R and R1 groups of the initiators, which leads to a decreased reflux temperature depression due to less generation of the corresponding alcohol and more generation of the free radical initiating species.  
       [0052] The initiator compound utilized in the process can have a half-life of about 1 hour at a reaction temperature of about 100-200° C., preferably of about 110-160° C.  
       [0053] According to a further aspect of the present invention, there is provided a formulation for initiating a chemical reaction, said formulation comprising TBTMBP compound and standard additives and fillers.  
       [0054] The peroxide formulations can be prepared, transported, stored, and applied in the form of powders, granules, pellets, pastilles, flakes, slabs, pastes, solid masterbatches, and liquids. These formulations may have the form of a dispersion, such as a suspension or an emulsion. These formulations may be phlegmatized, if necessary, depending on the particular peroxide and its concentration in the formulation. Which of these forms is to be preferred depends partly on the application for which it will be used and partly on the manner in which it will be mixed. Also, considerations of safety may play a role to the extent that phlegmatizers may have to be incorporated into certain compositions to ensure their safe handling.  
       [0055] The formulations of the present invention are transportable, storage stable, and contain 1.0-90% by weight of one or more peroxides according to the present invention. Transportable means that the formulations of the present invention have passed the pressure vessel test (PVT). Storage stable means that the formulations of the present invention are both chemically and physically stable during a reasonable storage period under standard conditions.  
       [0056] The formulations of the present invention can be liquids, solids or pastes depending on the melting point of the peroxide and the diluent employed. Liquid formulations can be made using liquid phlegmatizers, liquid plasticizers, organic peroxides, and mixtures thereof as the diluent. The liquid component is generally present in an amount of 1-99% by wt of the composition, preferably 10-90% by wt, more preferably 30-90% by wt, and most preferably 40-80% by wt of the liquid formulation consists of liquid diluents.  
       [0057] In liquid formulations a liquid carrier or diluent is used. Preferably this carrier or diluent is a solvent.  
       [0058] The formulations of the present invention may also contain optional other additives as long as these do not have a significant negative effect on the transportability and/or storage stability of the formulations. As examples of such additives may be mentioned: anti-caking agents, free-flowing agents, sequestering agents, anti-ozonants, anti-oxidants, anti-degradants, U.V. stabilizers, coagents, fungicides, antistats, pigments, dyes, coupling agents, dispersing aids, blowing agents, lubricants, process oils, and mould-release agents. These additives may be employed in their usual amounts.  
       [0059] In the solid and/or paste formulations of the present invention solid carrier materials are employed. Examples of such solid carriers are low-melting solids, such as dicyclohexylphthalate, dimethyl fumarate, dimethylisophthalate, triphenylphoshphate, glyceryltribenzoate, trimethylolethane tribenzoate, dicyclohexylterephtalate, paraffinic waxes, dicyclohexylisophthalate, polymers, and inorganic supports. Inorganic supports include materials such as fumed silica, precipitated silica, hydrophobic silica, chalk, whiting, surface-treated clays such as silane-treated clays, calcined clays, and talc.  
       [0060] Examples of additives include: 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 to control the molecular weight of the polymer, accelerators and other types of peroxides. These additives may be employed in the usual amounts.  
       [0061] Suitable solvents comprise alcohols, cycloalkanols, ethers, anhydrides, carbonates, alkylene glycols, amides, aldehydes, ketones, epoxides, esters, halogenated hydrocarbons such as chlorinated hydrocarbons, and mixtures thereof.  
       [0062] Suitable solvents generally preferred are hydrocarbon solvents, aromatic hydrocarbon solvents, aralkyl solvents, paraffinic oils, white oils, and silicone oils, as well as their mixtures. Useful hydrocarbon solvents include, but are not limited to, benzene, xylene, toluene, mesitylene, hexane, hydrogenated oligomers of alkanes such as Isopar® products (ex. Exxon), Shellsol® products (ex Shell), pentane, heptane, decane, isododecane, decalin, and the like. Paraffinic oils useful as apolar solvents include, but are not limited to, halogenated paraffinic oils and paraffinic diesel oil. Other oils, including white oils, epoxidized soybean oils, and silicone oils are also useful in the present invention.  
       [0063] According to a further aspect of the present invention, there is provided a composition suitable for one or more of the following chemical reactions:  
       [0064] polymerization of monomers, such as production of polymers suitable for solvent based coating applications and ethylene polymerization, and  
       [0065] modification of polymers, such as:  
       [0066] crosslinking and/or degradation of polymers;  
       [0067] curing of polymers,  
       [0068] said composition comprising an initiator, preferably TBTMBP, according to the present invention or an initiator formulation according to the present invention and one or more of the monomers referred to above.  
       [0069] According to another aspect of the present invention, there is provided a polymer obtainable according to the process of the present invention.  
       [0070] According to yet another aspect of the present invention, there is provided the use of an initiator, preferably TBTMBP, according to the present invention in the above processes.  
       [0071] The invention will now be further illustrated by way of the following examples and tables. 
     
    
    
     EXAMPLE ON ACRYLICS POLYMERIZATIONS  
     Example 1  
     [0072] High-Solids Acrylic Resin Synthesis  
     [0073] High-solids acrylic resins were produced by the polymerization of mixtures of acrylic monomers and other monomers by radical initiators in a solvent. In order to achieve low viscosity resins, the molecular weights of the polymer produced are to be low. To achieve this, a higher concentration of initiator, more efficient initiators, or a higher temperature can be applied. Below the results obtained with dialkylperoxides are described.  
                              Recipe                         parts by weight       Monomers   (total monomers = 100%)               n-Butylacrylate (BA)   40       Styrene (STY)   20       2-Hydroxyethylmethacrylate (HEMA)   28       Methylmethacrylate (MMA)   10       Methacrylic acid (MA)    2       Solvesso 100 ® (S-100)   40 (solvent)                  
 
     [0074] Initiator concentration: 30 meq/100 g monomers  
     [0075] Temperature: 140° C. and 165° C.  
     [0076] Procedure  
     [0077] Polymerizations were conducted under nitrogen in a jacketed glass reactor equipped with a turbine stirrer, thermocouple, reflux condenser, and injection inlet. The initiator was added to the monomers. This mixture was dosed to the solvent in a stirred vessel via the laboratory pump at the prescribed temperature in approx. 4 hours. The reaction was continued for an additional hour to reduce residual monomer/initiator. From the resins obtained the molecular weights, the colour, and the percentage of solids were determined.  
                               Raw materials                                        Monomers + solvent   Supplier               n-Butylacrylate (BA)   Acros       2-Hydroxyethylmethacrylate (HEMA)   Acros       Methylmethacrylate (MMA)   Acros       Styrene (STY)   Merck       Methacrylic acid (MA)   Janssen       Solvesso 100 ®   Exxon               Initiators (ex Akzo Nobel)   Appearance               tert-butyl-1,1,3,3-tetramethylbutyl   colorless liquid       peroxide (TBTMBP)       tert-amyl-t-butyl peroxide (TATBP)   colorless liquid       Trigonox ® B (Di-tertiary-butylperoxide (TxB))   colorless liquid                  
 
     [0078] The amount of initiator used (30 meq/100 g monomers) was corrected for the assay of the peroxides as supplied.  
     [0079] Analysis  
     [0080] Molecular weights were determined by gel permeation chromatography using polystyrene standards, according to method AR/94.14-1/HPLC. Solids contents were determined by percent non-volatile matter (0.5 hour at 150° C).  
     [0081] Results  
               TABLE 1                          Temp. 165° C.                                                 Reflux   Solids                       [Initiator]   temp.   content   Mw   Mn       Initiator   meq/100 gM   (° C.)   (%)   (g/mol)   (g/mol)   Disp.                                                 TBTMBP   30   165   71.0   3300   2000   1.7       TATBP   30   164   72.2   3700   2000   1.8       Tx B   30   157   74.3   5500   2900   1.9       TBTMBP   15       71.1   4400   2100   2.1       TBTMBP   60       72.0   1600   800   2.0                  
 
     [0082]               TABLE 2                          Temp. 140° C.                                             Solids                       [Initiator]   content   Mw   Mn       Initiator   meq/100 gM   (%)   (g/mol)   (g/mol)   Disp.                                             TBTMBP   15   72.8   10750   4000   2.7       TBTMBP   30   71.0   7400   3400   2.2       TBTMBP   60   73.2   4900   2200   2.2       TBHDMBP   30   70.8   7130   3170   2.3       TATBP   30   68.4   11900   4400   2.7       Tx B   30   72.4   18500   6100   3.0                            
     [0083] Conclusion  
     [0084] The mixed dialkylperoxides TBTMBP and TATBP gave lower Mw and Mn as compared to the symmetrical dialkylperoxides Tx B, indicating a more efficient initiation of the polymerization. In addition, a synergistic effect can be explained from the combination of the higher reflux temperature due to less generation of t-butanol (as compared to Tx B), and the generation of more efficient alkyl-radicals from the amyl and 1,1,3,3-tetramethylbutyl moieties. The higher reflux temperature promoted the formation of lower molecular weights by affecting the polymerization kinetics, as well as the formation of more efficient alkyl radicals.  
     Example 2  
     [0085] The comparison of DTBP and TB-TMBP was illustrated by the half-life temperatures for decomposition. As the residence times in the LDPE reactors are very short, the half-life times were in the range of 0.1-100 sec.  
                                                               TB-TMBP           half-life time at 2000 bar   DTBP peroxide   peroxide                           0.1 sec   284° C.   270° C.            1.0 sec   250° C.   235° C.            10 secs   220° C.   203° C.           100 secs   193° C.   175° C.                      
 
     [0086] The following halflife temperatures of the described dialkylperoxides were determined by thermal analysis of 0.1 molar solution of the dialkylperoxide in monochlorobenzene on a Mettler DSC 820.  
                                       T at which       Dialkylperoxide   t½ = 1 hr (° C.)                  (CH 3 ) 3 COOC(CH 3 ) 2 C 2 H 5  (TATBP)   142       (CH 3 ) 3 COOC(CH 3 ) 2 CH 2 C(CH 3 ) 3  (TBTMBP)   123       (CH 3 ) 3 COOC(CH 3 ) 2 CH 2 CH(CH 3 )OH (TBHDMBP)   125                  
 
     [0087] The lower half-life temperature offers the possibility of a lower processing temperature resulting in less long chain branching for TB-TMBP compared with DTBP.  
     [0088] The formation of less aggressive alkyl radicals is supported by the analyzed decomposition products indication a higher level of beta scisson compared with DTBP.  
     [0089] The halflife temperature was determined by thermal analysis of 0.1 molar solution of the dialkylperoxide in monochlorobenzene on a Mettler DSC 820.  
     [0090] Temperature program used: 10 C-3C/min-220C.  
     [0091] The heatflow was plotted versus the temperature by a computer.  
     [0092] The halflife temperature was calculated by the use of the Mettler Star software.  
     Example 3  
     [0093] Curing of Unsaturated Polyester  
     [0094] Objective: To check the cure performance of TBTMBP as curing agent for unsaturated polyester and compare it with Trigonox C (tertiary butyl perbenzoate).  
     [0095] Test procedure: The Time-Temperature curve was measured at 100° C. and 120° C. on compounds containing 100 parts of polyester resin, 150 parts of sand as filler, and 1 part of peroxide. This was carried out according to the method outlined by the Society of Plastic Institute. 25 g of compound were poured into a test tube and a thermocouple was placed through the enclosure cork at the center of the tube. The glass tube was then placed in the oil bath maintained at a specific test temperature and the time-temperature curve was measured. From the curve the following parameters were calculated:  
                                                               Test temp.                           ° C.   GT, min.   TTP, min.   PE, ° C.   RS, %                                                            Trig. C   100   7.2   14   131   1.8           120   1.48   4.4   212   0.01       TBTMBP   100   6.1   13   134   1.6           120   1.4   4.4   210   0.01                                                                  
 
     [0096] The invention is not limited to the above description; rather, the requested rights are determined by the following claims.