Process for curing thermoset resins

Abstract

Process for curing a thermoset resin comprising the step of contacting said resin with (i) an imine of the structure C(R.sup.2)(R.sup.3)═N—R.sup.1 wherein R.sup.1 is selected from hydrogen, hydroxyl, linear or branched alkyl having 1-22 carbon atoms, cycloalkyl having 3-22 carbon atoms, aryl having 6 to 15 carbon atoms, and aralkyl having 7 to 22 carbon atoms, which alkyl, cycloalkyl, aryl, and aralkyl groups may be optionally substituted with one or more groups containing heteroatoms selected from S, O, P, and/or Si. R.sup.2 is selected from C(R.sup.6)(R.sup.5)—C(═O)—R.sup.4, —C(R.sup.6)(R.sup.5)—C(═S)—R.sup.4, and —C(R.sup.6)(R.sup.5)—C(═N)—R.sup.4, wherein R.sup.4, R.sup.5, and R.sup.6 are selected from hydrogen, linear or branched alkyl having 1-6 carbon atoms, cycloalkyl having 3-12 carbon atoms, aryl, aralkyl, alkoxy having 1-6 carbon atoms, and aryloxy. R.sup.3 is selected from linear or branched alkyl having 1-22 carbon atoms, 1 cycloalkyl having 3-22 carbon atoms, aryl having 6 to 15 carbon atoms, and aralkyl having 7 to 22 carbon atoms, and (ii) methyl isopropyl ketone peroxide.

Claims

1. A process for curing a thermoset resin comprising the step of contacting said resin with (i) an imine of the structure C(R.sup.2)(R.sup.3)═N—R.sup.1 wherein R.sup.1 is selected from the group consisting of hydrogen, hydroxyl, linear or branched alkyl having 1-22 carbon atoms, cycloalkyl having 3-22 carbon atoms, aryl having 6 to 15 carbon atoms, and aralkyl having 7 to 22 carbon atoms, said alkyl, cycloalkyl, aryl, and aralkyl groups may be optionally substituted with one or more groups containing heteroatoms selected from the group consisting of S, O, P, and Si, R.sup.2 is selected from C(R.sup.6)(R.sup.5)—C(═O)—R.sup.4, —C(R.sup.6)(R.sup.5)—C(═S)—R.sup.4, and —C(R.sup.6)(R.sup.5)—C(═N)—R4, wherein R.sup.4, R.sup.5, and R.sup.6 are selected from the group consisting of hydrogen, linear or branched alkyl having 1-6 carbon atoms, cycloalkyl having 3-12 carbon atoms, aryl, aralkyl, alkoxy having 1-6 carbon atoms, and aryloxy, R.sup.3 is selected from the group consisting of linear or branched alkyl having 1-22 carbon atoms, cycloalkyl having 3-22 carbon atoms, aryl having 6 to 15 carbon atoms, and aralkyl having 7 to 22 carbon atoms, and (ii) methyl isopropyl ketone peroxide.

2. The process according to claim 1 wherein R.sup.2 has the formula —C(H)(R.sup.5)—C(═O)—R.sup.4.

3. The process according to claim 1 wherein R.sup.5 is hydrogen.

4. The process according to claim 1 wherein R.sup.4 is an alkoxy group and R.sup.3 is an alkyl group.

5. The process according to claim 4 wherein R.sup.4 is an ethoxy group.

6. The process according to claim 4 wherein and R.sup.3 is a methyl group.

7. The process according to claim 1 wherein R.sup.1 is selected from the group consisting of n-propyl, isopropyl, n-butyl, t-butyl, t-amyl, and cyclohexyl, and hydroxyethyl.

8. The process according to claim 1 wherein said resin is contacted with said imine in an amount of 0.5 to 2 parts by weight of imine per 100 parts by weight of resin.

9. The process according to claim 1 wherein said resin is contacted with said methyl isopropyl ketone peroxide in an amount of 1 to 2 parts by weight of imine per 100 parts by weight of resin.

Description

EXAMPLES

(1) The following materials were used in the examples below: Palatal P6—an ortho phthalic acid-based unsaturated polyester resin (ex-DSM resins) Butanox® P50—methyl isopropyl ketone peroxide (50 wt % in dimethylphthalate; ex-AkzoNobel) Butanox® M50—methyl ethyl ketone peroxide with an active oxygen content of 8.9 wt % (50 wt % in dimethylphthalate; ex-AkzoNobel) Trigonox® 233—methyl isobutyl ketone peroxide (50 wt % in isododecane; ex-AkzoNobel) Imine 1—4-(n-butylamino)-3-pentene-2-one Imine 2—ethyl-3-(n-butylamino)-2-butenoate Imine 3—3-(n-butylamino)-N,N-diethyl-2-butenamide

(2) ##STR00005##

(3) Curable compositions were prepared by mixing 100 phr resin, 1 phr accelerator, and 2 phr peroxide as listed in Tables 1-3. The accelerator was one of the imines listed above.

(4) The compositions were allowed to cure at 20° C.

(5) The cure of the compositions was analyzed by the method of the Society of Plastic Institure (analysis method F/77.1; available from Akzo Nobel Polymer Chemicals).

(6) This method involves measuring of the peak exotherm, the time to peak, and the gel time.

(7) According to this method, 20 g of a mixture comprising resin, peroxide, and accelerator were poured into a test tube and a thermocouple was placed through the enclosure at the centre of the tube. The glass tube was then placed in climate controlled room maintained at 20° C. and the time-temperature curve was measured. From the curve the following parameters were calculated:

(8) Gel time (GT)=time in minutes elapsed between the start of the experiment and 5.5° C. above the bath temperature.

(9) Time to peak exotherm (TTP)=time elapsed between the start of the experiment and the moment the peak exotherm was reached.

(10) Peak Exotherm (PE)=the maximum temperature that was reached.

(11) Shore D hardness was determined by standard method ASTM D2240.

(12) Also the colour the final cured resin was evaluated.

(13) The results are listed in Tables 1-3.

(14) TABLE-US-00001 TABLE 1 Accelerator: Imine 1 Imine 1 Imine 1 Peroxide Butanox M50 Butanox P-50 Trigonox 233 Gt [min .Math. sec] 11.27 9.28 18.50 TTP [min .Math. sec] 35.12 25.05 38.34 PE [° C.] 44 114 35 Shore D [48 h] 65-70 70-75 35-40 colour: str. yellowish str. yellowish str. yellowish

(15) TABLE-US-00002 TABLE 2 Accelerator: Imine 2 Imine 2 Imine 2 Peroxide Butanox M50 Butanox P-50 Trigonox 233 Gt [min .Math. sec] 5.56 5.16 7.23 TTP [min .Math. sec] 29.54 18.07 32.22 PE [° C.] 45 134 58 Shore D [48 h] 70-75 80-85 70-75 colour: blanco yellowish sl. yellowish

(16) TABLE-US-00003 TABLE 3 Accelerator: Imine 3 Imine 3 Imine 3 Peroxide Butanox M50 Butanox P-50 Trigonox 233 Gt [min .Math. sec] ca. 40 18.48 ca. 30 TTP [min .Math. sec] ca. 60 21.11 ca. 53 PE [° C.] 24 46 27 Shore D [48 h] 40-45 55-60 60-65 colour: blanco blanco blanco

(17) These data show that the best curing behavior of these systems is obtained by using methyl isopropyl ketone peroxide compared to other ketone peroxides.