ISOCYANATE GROUP-CONTAINING ORGANOSILICON COMPOUND AND METHOD FOR PRODUCING ISOCYANATE GROUP-CONTAINING ORGANOSILICON COMPOUND

Abstract

An isocyanate group-containing organosilicon compound shown by the following general formula (1), and having three or more R.sup.2 groups per molecule and a viscosity at 25° C. of 100 mm.sup.2/s or less. This provides an organosilicon compound which has three or more isocyanate groups per molecule, and which is suitable as a crosslinking agent, low in viscosity, and excellent in handleability. R.sup.1.sub.aR.sup.2.sub.bSiO.sub.(4−a−b)/2 (1), where each R.sup.1 is identical to or different from one another, represents a monovalent alkyl group having 1 to 10 carbon atoms, a fluorine-substituted alkyl group, a monovalent aryl group having 6 to 10 carbon atoms, or a monovalent aralkyl group having 7 to 10 carbon atoms, and has no aliphatic unsaturated group; and R.sup.2 represents an organic group shown by a formula —CH.sub.2CH.sub.2Si(CH.sub.3).sub.2OSi(CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2NCO.

Claims

1. An isocyanate group-containing organosilicon compound shown by the following general formula (1),
R.sup.1.sub.aR.sup.2.sub.bSiO.sub.(4−a−b)/2  (1) wherein each R.sup.1 is identical to or different from one another, represents a monovalent alkyl group having 1 to 10 carbon atoms, a fluorine-substituted alkyl group, a monovalent aryl group having 6 to 10 carbon atoms, or a monovalent aralkyl group having 7 to 10 carbon atoms, and has no aliphatic unsaturated group; R.sup.2 represents an organic group shown by a formula —CH.sub.2CH.sub.2Si(CH.sub.3).sub.2OSi(CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2NCO; and “a” and “b” each represent a positive number satisfying 0.9≤a≤1.9, 0.25≤b≤1.1, and 1.9≤a+b≤2.8, and the isocyanate group-containing organosilicon compound comprises three or more R.sup.2 groups per molecule and has a viscosity at 25° C. of 100 mm.sup.2/s or less.

2. The isocyanate group-containing organosilicon compound according to claim 1, wherein the isocyanate group-containing organosilicon compound is shown by the following general formula (2),
R.sup.1.sub.2R.sup.3SiO(SiR.sup.1.sub.2O).sub.c(SiR.sup.1R.sup.2O).sub.dSiR.sup.1.sub.2R.sup.3  (2) wherein R.sup.1 and R.sup.2 are as defined above, R.sup.3 represents either R.sup.1 or R.sup.2, “c” represents an integer of 0 to 20, “d” represents an integer of 1 to 10, and “c+d” is an integer of 1 to 30.

3. The isocyanate group-containing organosilicon compound according to claim 1, wherein the isocyanate group-containing organosilicon compound is shown by the following general formula (3),
R.sup.1.sub.eSi(OSiR.sup.1.sub.2R.sup.2).sub.f  (3) wherein R.sup.1 and R.sup.2 are as defined above, “e” represents 0 or 1, “f” represents 3 or 4, and “e+f” is 4.

4. The isocyanate group-containing organosilicon compound according to claim 1, wherein the isocyanate group-containing organosilicon compound is shown by the following general formula (4), ##STR00024## wherein R.sup.1 and R.sup.2 are as defined above, “g” represents an integer of 0 to 2, “h” represents an integer of 3 to 5, and “g+h” is an integer of 3 to 7.

5. A method for producing the isocyanate group-containing organosilicon compound according to claim 1, the method comprising performing an addition reaction between CH.sub.2═CHSi(CH.sub.3).sub.2OSi (CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2NCO and an organohydrogenpolysiloxane shown by the following general formula (5),
R.sup.1.sub.aH.sub.bSiO.sub.(4−a−b)/2  (5) wherein R.sup.1, “a”, and “b” are as defined above.

6. A method for producing the isocyanate group-containing organosilicon compound according to claim 2, the method comprising performing an addition reaction between CH.sub.2═CHSi(CH.sub.3).sub.2OSi(CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2NCO and an organohydrogenpolysiloxane shown by the following general formula (6),
R.sup.1.sub.2R.sup.4SiO (SiR.sup.1.sub.2O).sub.c(SiR.sup.1HO).sub.dSiR.sup.1.sub.2R.sup.4  (6) wherein R.sup.1, “c”, and “d” are as defined above, and R.sup.4 represents either R.sup.1 or H.

7. A method for producing the isocyanate group-containing organosilicon compound according to claim 3, the method comprising performing an addition reaction between CH.sub.2═CHSi(CH.sub.3).sub.2OSi(CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2NCO and an organohydrogenpolysiloxane shown by the following general formula (7),
R.sup.1.sub.eSi (OSiR.sup.1.sub.2H).sub.f  (7) wherein R.sup.1, “e”, and “f” are as defined above.

8. A method for producing the isocyanate group-containing organosilicon compound according to claim 4, the method comprising performing an addition reaction between CH.sub.2═CHSi(CH.sub.3).sub.2OSi(CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2NCO and an organohydrogenpolysiloxane shown by the following general formula (8), ##STR00025## wherein, R.sup.1, “g” and “h” are as defined above.

Description

DESCRIPTION OF EMBODIMENTS

[0036] As noted above, there have been demands for the development of an organosilicon compound which has three or more isocyanate groups per molecule, and which is suitable as a crosslinking agent, low in viscosity, and excellent in handleability.

[0037] The present inventor and colleagues have earnestly studied to achieve the above object and consequently found an isocyanate group-containing organosilicon compound having the following particular structure. This finding has led to the present invention.

[0038] Specifically, the present invention is an isocyanate group-containing organosilicon compound shown by the following general formula (1),

R.sup.1.sub.aR.sup.2.sub.bSiO.sub.(4−a−b)/2  (1)

wherein each R.sup.1 is identical to or different from one another, represents a monovalent alkyl group having 1 to 10 carbon atoms, a fluorine-substituted alkyl group, a monovalent aryl group having 6 to 10 carbon atoms, or a monovalent aralkyl group having 7 to 10 carbon atoms, and has no aliphatic unsaturated group; R.sup.2 represents an organic group shown by a formula —CH.sub.2CH.sub.2Si(CH.sub.3).sub.2OSi(CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2NCO; and “a” and “b” each represent a positive number satisfying 0.9≤a≤1.9, 0.25≤b≤1.1, and 1.9≤a+b≤2.8, and

[0039] the isocyanate group-containing organosilicon compound comprises three or more R.sup.2 groups per molecule and has a viscosity at 25° C. of 100 mm.sup.2/s or less.

[0040] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0041] The inventive isocyanate group-containing organosilicon compound is represented by the following general formula (1).

R.sup.1.sub.aR.sup.2.sub.bSiO.sub.(4−a−b)/2  (1)

[0042] In the formula (1), R.sup.1's are identical to or different from one another, and are each a monovalent alkyl group having 1 to 10 carbon atoms, a fluorine-substituted alkyl group, a monovalent aryl group having 6 to 10 carbon atoms, or a monovalent aralkyl group having 7 to 10 carbon atoms. R.sup.1 has no aliphatic unsaturated group. R.sup.2 is an organic group shown by a formula —CH.sub.2CH.sub.2Si(CH.sub.3).sub.2OSi(CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2NCO. “a” and “b” are each a positive number satisfying 0.9≤a≤1.9, 0.25≤b≤1.1, and 1.9≤a+b≤2.8.

[0043] The isocyanate group-containing organosilicon compound has three or more. R.sup.2 groups per molecule, and the viscosity at 25° C. thereof is 100 mm.sup.2/s or less.

[0044] Note that the viscosity is measured at 25° C. by using a modified Ostwald capillary viscometer.

[0045] R.sup.1 may be linear, branched, or cyclic. Specific examples thereof can include: alkyl groups, such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group; saturated alicyclic hydrocarbon groups, such as a cyclopentyl group and a cyclohexyl group; aryl groups, such as a phenyl group and a tolyl group; aralkyl groups, such as a benzyl group and a phenylethyl group; fluorine-substituted alkyl groups, such as a trifluoropropyl group and a nonafluorohexyl group; etc. R.sup.1 is preferably a methyl group or a phenyl group.

[0046] “a” is 0.9 to 1.9, preferably 1.0 to 1.8. “b” is 0.25 to 1.1, preferably 0.4 to 1.0. “a+b” is 1.9 to 2.8, preferably 2.0 to 2.6. This is because if “a” is smaller than 0.9, the silicon unit forming the present compound is expensive and not economically preferable. If “a” is larger than 1.9, it is difficult to prepare three or more R.sup.2 groups per molecule and make the viscosity at 25° C. 100 mm.sup.2/s or less. If “b” is smaller than 0.25, it is difficult to prepare three or more R.sup.2 groups per molecule and make the viscosity at 25° C. 100 mm.sup.2/s or less. If “b” is larger than 1.1, the silicon unit forming the present compound is not economically preferable. If a+b is smaller than 1.9, the silicon unit forming the present compound is not economically preferable. If a+b is larger than 2.8, it is difficult to prepare three or more R.sup.2 groups per molecule and make the viscosity at 25° C. 100 mm.sup.2/s or less.

[0047] The inventive isocyanate group-containing organosilicon compound is preferably shown by any of the following general formulae (2) to (4).

[0048] The inventive isocyanate group-containing organosilicon compound is preferably an isocyanate group-containing organosilicon compound with a linear structure shown by the following general formula (2).

R.sup.1.sub.2R.sup.3SiO(SiR.sup.1.sub.2O).sub.c(SiR.sup.1R.sup.2O).sub.dSiR.sup.1.sub.2R.sup.3  (2)

In the formula (2), R.sup.1 and R.sup.2 are as defined above. R.sup.3 is either R.sup.1 or R.sup.2, and the number of R.sup.2 groups is three or more per molecule. “c” represents an integer of 0 to 20, “d” represents an integer of 1 to 10, and “c+d” is an integer of 1 to 30.

[0049] The viscosity at 25° C. thereof is 100 mm.sup.2/s or less.

[0050] “c” is 0 to 20, preferably 0 to 10. “d” is 1 to 10, preferably 1 to 5. c+d is 1 to 30, preferably 1 to 10. When “c” is 20 or less, it is easy to prepare three or more R.sup.2 groups per molecule and make the viscosity at 25° C. 100 mm.sup.2/s or less. When “d” is 10 or less and “c+d” is 30 or less, it is similarly easy to make the viscosity at 25° C. 100 mm.sup.2/s or less. Additionally, as necessary, an R.sup.1SiO.sub.1.5 unit or an SiO.sub.2 unit may be incorporated as a siloxane-constituting unit.

[0051] Moreover, the inventive isocyanate group-containing organosilicon compound is preferably an isocyanate group-containing organosilicon compound with a branched structure shown by the following general formula (3).

R.sup.1.sub.eSi(OSiR.sup.1.sub.2R.sup.2).sub.f  (3)

In the formula (3), R.sup.1 and R.sup.2 are as defined above. “e” represents 0 or 1, “f” represents 3 or 4, and “e+f” is 4.

[0052] This isocyanate group-containing organosilicon compound shown by the general formula (3) has three to four R.sup.2 groups per molecule and a viscosity at 25° C. of 100 mm.sup.2/s or less.

[0053] Furthermore, the inventive isocyanate group-containing organosilicon compound is preferably an isocyanate group-containing organosilicon compound with a cyclic structure shown by the following general formula (4).

##STR00003##

In the formula (4), R.sup.1 and R.sup.2 are as defined above, “g” represents an integer of 0 to 2, “h” represents an integer of 3 to 5, and “g+h” is an integer of 3 to 7.

[0054] This isocyanate group-containing organosilicon compound shown by the general formula (4) has three or more R.sup.2 groups per molecule and a viscosity at 25° C. of 100 mm.sup.2/s or less.

[0055] According to the present invention, it is possible to provide isocyanate group-containing organosilicon compounds shown by the general formulae (2) to (4) having desired linear, branched, or cyclic structure.

[0056] Hereinbelow, methods for producing the compounds shown by the general formulae (1) to (4) will be described.

[0057] The inventive isocyanate group-containing organosilicon compounds can be obtained by a hydrosilylation reaction between an organohydrogenpolysiloxane corresponding to one of compounds shown by the following general formulae (5) to (8) and an alkenyl group-containing isocyanate compound CH.sub.2═CHSi(CH.sub.3).sub.2OSi(CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2NCO .

[0058] The invention isocyanate group-containing organosilicon compound shown by the general formula (1) can be obtained by hydrosilylation between the alkenyl group-containing isocyanate compound and an organohydrogenpolysiloxane shown by the following general formula (5) in the presence of a platinum-based catalyst, for example.

R.sup.1.sub.aH.sub.bSiO.sub.(4−a−b)/2  (5)

[0059] In the formula (5), R.sup.1, “a”, and “b” are as defined above.

[0060] Similarly, when a target product is a compound with a linear structure shown by the general formula (2), it can be obtained by an addition reaction between the alkenyl group-containing isocyanate compound and an organohydrogenpolysiloxane shown by the following general formula (6).

R.sup.1.sub.2R.sup.4SiO(SiR.sup.1.sub.2O).sub.c(SiR.sup.1HO).sub.dSiR.sup.1.sub.2R.sup.4  (6)

In the formula (6), R.sup.1, “c”, and “d” are as defined above, and R.sup.4 is either R.sup.1 or H.

[0061] When a target product is a compound with a branched structure shown by the general formula (3), it can be obtained by an addition reaction between the alkenyl group-containing isocyanate compound and an organohydrogenpolysiloxane shown by the following general formula (7).

R.sup.1.sub.eSi (OSiR.sup.1.sub.2H).sub.f  (7)

In the formula (7), R.sup.1, “e”, and “f” are as defined above.

[0062] Further, when a target product is a compound with a cyclic structure shown by the general formula (4), it can be obtained by an addition reaction between the alkenyl group-containing isocyanate compound and an organohydrogenpolysiloxane shown by the following general formula (8).

##STR00004##

[0063] In the formula (8), R.sup.1, R.sup.2, “g” and “h” are as defined above.

[0064] The addition reactions between the organohydrogenpolysiloxanes and the alkenyl group-containing isocyanate compound can be performed according to a conventionally known method. For example, relative to 1 mol of hydrogen atoms directly bonded to silicon atoms in the organohydrogenpolysiloxanes shown by the general formulae (5) to (8), the alkenyl group-containing isocyanate compound may be added in an amount of 1 molar equivalent or more for the reaction. The reaction temperature is not particularly limited. The temperature preferably does not exceed the boiling point of a solvent to be used. For example, the reaction is preferably performed at a temperature of approximately 0° C. to approximately 120° C. The reaction may be carried out in the presence of a solvent, hydrosilylation catalyst, or stabilizer. The solvent, hydrosilylation catalyst, and stabilizer may be conventionally known materials and are not particularly limited.

[0065] In the reaction, the alkenyl group-containing isocyanate compound is preferably added in an amount of 1 molar equivalent or more relative to 1 mol of hydrogen atoms directly bonded to silicon atoms in the organohydrogenpolysiloxane. The amount is more preferably 1.0 to 3.0 molar equivalents, further preferably 1.1 to 2.0 molar equivalents, and particularly preferably 1.2 to 1.5 molar equivalents.

[0066] The hydrosilylation catalyst is, for example, a noble metal catalyst, particularly preferably a platinum catalyst derived from chloroplatinic acid. Especially, chloride ions of chloroplatinic acid may be completely neutralized with sodium bicarbonate to improve the stability of the platinum catalyst. For example, a complex (Karstedt catalyst) of 1,1,3,3-tetramethyl-1,3-divinyldisiloxane and a neutralized product of chloroplatinic acid with sodium bicarbonate is more preferable.

[0067] The hydrosilylation catalyst may be added in a catalytic amount to advance the reaction. For example, a complex of 1,1,3,3-tetramethyl-1,3-divinyldisiloxane and a neutralized product of chloroplatinic acid with sodium bicarbonate may be used in an amount of 1 ppm to 80 ppm in terms of platinum relative to the mass of the hydrogensiloxane compound shown by one of the formulae (5) to (8).

[0068] The addition reaction performed in the presence of a platinum-based catalyst does not necessarily require a solvent, or may employ a hydrocarbon solvent, such as isooctane, toluene, and xylene; an ether solvent, such as tetrahydrofuran, dibutyl ether, monoglyme, and diglyme; or an aprotic solvent, such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, and dimethylimidazolidinone.

[0069] The isocyanate compound CH.sub.2═CHSi(CH.sub.3).sub.2OSi(CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2NCO used in the addition reaction can be synthesized by the following known methods (A) to (C).

(A) isocyanate formation through reaction of CH.sub.2=CHSi (CH.sub.3).sub.2OSi(CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2NH.sub.2 with phosgene;
(B) isocyanate formation through reaction of CH.sub.2=CHSi (CH.sub.3).sub.2OSi(CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2I with potassium cyanate; and
(C) isocyanate formation through reaction of CH.sub.2=CHSi (CH.sub.3).sub.2OSi (CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2NH.sub.2 with phenyl chloroformate or diphenyl carbonate to obtain phenyl carbamate ester shown by CH.sub.2═CHSi(CH.sub.3).sub.2OSi(CH.sub.3).sub.2CH.sub.2CH.sub.2CH.sub.2NHCOOPh, followed by thermal decomposition reaction.

[0070] Among these, preferable is the synthesis method (C) in which phenyl carbamate ester is thermally decomposed in the presence of a trialkylchlorosilane and an acid scavenger as disclosed in Patent Document 1 mentioned above.

[0071] As described above, an organohydrogenpolysiloxane with a desired structure can be used as a raw material to produce the inventive isocyanate group-containing organosilicon compound, so that linear, branched, or cyclic structure can be prepared at will easily, too.

EXAMPLE

[0072] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited thereto.

[0073] Additionally, each viscosity was measured at a temperature of 25° C. with a modified Ostwald capillary viscometer.

Synthesis Example

[0074] Into a flask, 331.2 g of potassium carbonate was introduced together with 300.0 g of water and uniformly dissolved. Then, 180.0 g of ethyl acetate and 150.0 g of toluene were added. After the flask was ice-cooled, 217.0 g of the following aminovinyldisiloxane was added.

##STR00005##

[0075] Subsequently, 156.5 g of phenyl chloroformate was added dropwise at such a speed that the inner temperature did not exceed 10° C. The inner temperature was maintained at 10° C. or less, and the reaction was allowed to proceed for another 2 hours. Thereafter, 800 g of water was added to dissolve the resulting salt. After the aqueous layer was separated, the organic layer was washed with water and dried with anhydrous sodium sulfate. After the filtration, the resulting solution was concentrated under reduced pressure. Thus, 336.1 g of the following phenyl carbamate derivative was obtained.

##STR00006##

[0076] Next, 336.1 g of the phenyl carbamate derivative synthesized above and 300.0 g of xylene were introduced into a flask. 131.0 g of triethylamine was added thereto and heated such that the inner temperature reached 80° C. Then, 129.9 g of trimethylchlorosilane was added dropwise. After the completion of the dropwise addition, the mixture was heated and stirred at 100° C. for 1 hour and subsequently at 120° C. for 6 hours. After cooling to room temperature, the resulting salt was filtered. The filtrate was washed with 300 g of water, and then dried with anhydrous sodium sulfate. After the filtration, distillation was performed under reduced pressure. Thus, 155.3 g of the following target product was obtained: 1-(3-isocyanatopropyl)-1,1,3,3-tetramethyl-3-vinyldisiloxane [A].

##STR00007##

[0077] The boiling point was 64.0 to 65.0° C./300 Pa, and the purity was 99.9% according to gas chromatography.

Example 1

[0078] Into a flask, 121.5 g of the isocyanate-vinyldisiloxane [A] obtained in Synthesis Example was introduced. The flask was purged with argon atmosphere and then heated such that the inner temperature reached 70° C. After 0.04 g of a Karstedt catalyst (platinum concentration: 3%) was added, 27.3 g of an organohydrogenpolysiloxane shown by the following formula [H-1] was added dropwise. After the completion of the dropwise addition, the reaction was allowed to proceed at 110° C. for 5 hours.

##STR00008##

[0079] After the reaction, the unreacted materials were distilled off by heating under reduced pressure. Thus, 126.1 g of an isocyanate siloxane of the following formula [I-1] was obtained.

##STR00009##

[0080] In the general formula (1), a=1 and b=1. In the general formula (4), g=0, h=4, and R.sup.1—a methyl group. This liquid had colorless transparent appearance, the viscosity at 25° C. was 41.6 mm.sup.2/s, and the isocyanate equivalent weight was 318 g/mol.

Example 2

[0081] Into a flask, 126.0 g of the isocyanate-vinyldisiloxane [A] obtained in Synthesis Example was introduced. The flask was purged with argon atmosphere and then heated such that the inner temperature reached 70° C. After 0.06 g of a Karstedt catalyst (platinum concentration: 3%) was added, 40.3 g of an organohydrogenpolysiloxane shown by the following formula [H-2] was added dropwise. After the completion of the dropwise addition, the reaction was allowed to proceed at 110° C. for 5 hours.

##STR00010##

[0082] After the reaction, the unreacted materials were distilled off by heating under reduced pressure. Thus, 140.4 g of an isocyanate siloxane of the following formula [I-2] was obtained.

##STR00011##

[0083] In the general formula (1), a=1.75 and b=0.75. In the general formula (3), e=1, f=3, and R.sup.1=a methyl group. This liquid had colorless transparent appearance, the viscosity at 25° C. was 20.7 mm.sup.2/s, and the isocyanate equivalent weight was 359 g/mol.

Example 3

[0084] Into a flask, 91.9 g of the isocyanate-vinyldisiloxane [A] obtained in Synthesis Example was introduced. The flask was purged with argon atmosphere and then heated such that the inner temperature reached 70° C. After 0.04 g of a Karstedt catalyst (platinum concentration: 3%) was added, 38.2 g of an organohydrogenpolysiloxane shown by the following formula [H-3] was added dropwise. After the completion of the dropwise addition, the reaction was allowed to proceed at 110° C. for 5 hours.

##STR00012##

[0085] After the reaction, the unreacted materials were distilled off by heating under reduced pressure. Thus, 103.4 g of an isocyanate siloxane of the following formula [I-3] was obtained.

##STR00013##

[0086] In the general formula (1), a=1.75 and b=0.75. In the general formula (3), e=1, f=3, and R.sup.1=a methyl group and a decyl group. This liquid had colorless transparent appearance, the viscosity at 25° C. was 29.6 mm.sup.2/s, and the isocyanate equivalent weight was 382 g/mol.

Example 4

[0087] Into a flask, 78.4 g of the isocyanate-vinyldisiloxane [A] obtained in Synthesis Example was introduced. The flask was purged with argon atmosphere and then heated such that the inner temperature reached 70° C. After 0.04 g of a Karstedt catalyst (platinum concentration: 3%) was added, 27.3 g of an organohydrogenpolysiloxane shown by the following formula [H-4] was added dropwise. After the completion of the dropwise addition, the reaction was allowed to proceed at 110° C. for 5 hours.

##STR00014##

[0088] After the reaction, the unreacted materials were distilled off by heating under reduced pressure. Thus, 83.0 g of an isocyanate siloxane of the following formula [I-4] was obtained.

##STR00015##

[0089] In the general formula (1), a=1.75 and b=0.75. In the general formula (3), e=1, f=3, and R.sup.1=a methyl group and a phenyl group. This liquid had colorless transparent appearance, the viscosity at 25° C. was 28.6 mm.sup.2/s, and the isocyanate equivalent weight was 374 g/mol.

Example 5

[0090] Into a flask, 79.7 g of the isocyanate-vinyldisiloxane [A] obtained in Synthesis Example was introduced. The flask was purged with argon atmosphere. Then, 20 ml of toluene was added therein and the resultant was heated such that the inner temperature reached 70° C. After 0.06 g of a Karstedt catalyst (platinum concentration: 3%) was added, 16.4 g of an organohydrogenpolysiloxane shown by the following formula [H-5] was added dropwise. After the completion of the dropwise addition, the reaction was allowed to proceed at 110° C. for 5 hours.

##STR00016##

[0091] After the reaction, the solvent and the unreacted materials were distilled off by heating under reduced pressure. Thus, 77.8 g of an isocyanate siloxane of the following formula [I-5] was obtained.

##STR00017##

[0092] In the general formula (1), a=1 and b=1. In the general formula (4), g=0, h=5, and R.sup.1=a methyl group. This liquid had pale yellow transparent appearance, the viscosity at 25° C. was 70.6 mm.sup.2/s, and the isocyanate equivalent weight was 369 g/mol.

Example 6

[0093] Into a flask, 90.4 g of the isocyanate-vinyldisiloxane [A] obtained in Synthesis Example was introduced. The flask was purged with argon atmosphere. Then, 15 ml of toluene was added therein and the resultant was heated such that the inner temperature reached 70° C. After 0.04 g of a Karstedt catalyst (platinum concentration: 3%) was added, 25.4 g of an organohydrogenpolysiloxane shown by the following formula [H-6] was added dropwise. After the completion of the dropwise addition, the reaction was allowed to proceed at 110° C. for 5 hours.

##STR00018##

[0094] After the reaction, the solvent and the unreacted materials were distilled off by heating under reduced pressure. Thus, 94.7 g of an isocyanate siloxane of the following formula [I-6] was obtained.

##STR00019##

[0095] In the general formula (1), a=1.6 and b=0.8. In the general formula (3), e=0, f=4, and R.sup.1=a methyl group. This liquid had colorless transparent appearance, the viscosity at 25° C. was 29.2 mm.sup.2/s, and the isocyanate equivalent weight was 375 g/mol.

Example 7

[0096] Into a flask, 25.0 g of an organohydrogenpolysiloxane shown by the following formula [H-7] was introduced. The flask was purged with argon atmosphere. Then, 15 ml of toluene was added therein and the resultant was heated such that the inner temperature reached 70° C. After 0.06 g of a Karstedt catalyst (platinum concentration: 3%) was added, 34.8 g of the isocyanate-vinyldisiloxane [A] obtained in Synthesis Example was added dropwise. After the completion of the dropwise addition, the reaction was allowed to proceed at 110° C. for 5 hours.

##STR00020##

[0097] After the reaction, the solvent and the unreacted materials were distilled off by heating under reduced pressure, 47.9 g of an isocyanate siloxane of the following formula [1-7] was obtained.

##STR00021##

[0098] In the general formula (1), a=1.82 and b=0.29. In the general formula (2), c=10, d=5, and R.sup.1=R.sup.3=a methyl group. This liquid had yellow transparent appearance, the viscosity at 25° C. was 84.1 mm.sup.2/s, and the isocyanate equivalent weight was 553 g/mol.

Example 8

[0099] Into a flask, 51.2 g of the isocyanate-vinyldisiloxane [A] obtained in Synthesis Example was introduced. The flask was purged with argon atmosphere and then heated such that the inner temperature reached 70° C. After 0.06 g of a Karstedt catalyst (platinum concentration: 3%) was added, 15.0 g of an organohydrogenpolysiloxane shown by the following formula [H-8] was added dropwise. After the completion of the dropwise addition, the reaction was allowed to proceed at 110° C. for 5 hours.

##STR00022##

[0100] After the reaction, the unreacted materials were distilled off by heating under reduced pressure. Thus, 51.1 g of an isocyanate siloxane of the following formula [I-8] was obtained.

##STR00023##

[0101] In the general formula (1), a=1.25 and b=0.75. In the general formula (4), g=1, h=3, and R.sup.1=a methyl group and a propyl group. This liquid had pale yellow transparent appearance, the viscosity at 25° C. was 34.0 mm.sup.2/s, and the isocyanate equivalent weight was 383 g/mol.

[0102] From the foregoing, the present invention makes it possible to obtain organosilicon compounds having three or more isocyanate groups per molecule, and being suitable as a crosslinking agent, low in viscosity, and excellent in handleability. Examples of crosslinking agents can include an isocyanurate-type hexamethylene diisocyanate derivative product name Duranate TKA-100. If its density is 1 g/cm.sup.3, the viscosity is 2600 mm.sup.2/s. In contrast, according to the present invention, the viscosity is 100 mm.sup.2/s or less, so that low viscosity is achieved. In addition, since the inventive organosilicon compounds have low viscosity, this facilitates uniform mixing with polymeric polyol compounds or polymeric polyamine compounds, and also facilitates defoaming after the mixing. Thus, the inventive organosilicon compounds are useful as curing agents for obtaining cured mold products.

[0103] It should be noted that the present invention is not limited to the above-described embodiments. The embodiments are just examples, and any embodiments that substantially have the same feature and demonstrate the same functions and effects as those in the technical concept disclosed in claims of the present invention are included in the technical scope of the present invention.