DE68904651T2 - GROUP TRANSFER POLYMERIZATION CATALYST. - Google Patents

Description

Background of the invention Field of the invention

This invention relates to group transfer polymerization catalyzed by selected silanes, preferably in the presence of a suitable mercury compound and/or Lewis acid.

State of the art

U.S. Patents 4,414,372, 4,417,034, 4,508,880, 4,524,196, 4,581,428, 4,588,795, 4,598,161, 4,605,716, 4,622,372, 4,656,233, 4,659,782, 4,659,783, 4,681,918, 4,695,607, 4,711,942, 4,732,955, hereinafter referred to as "the aforesaid patents", disclose processes for polymerizing an acrylic or maleimide monomer to a "living" polymer in the presence of:

(i) an initiator comprising a tetra-coordinated organosilicon, organotin or organogermanium compound having at least one initiating site; and

(ii) a co-catalyst which is a source of fluoride, bifluoride, cyanide or azide ions or a suitable Lewis acid, Lewis base or selected oxyanion. Such polymerization processes are described in known in the professional world as group transfer polymerization (Webster et al., J. Am. Chem. Soc., 105: 5706 (1983)).

Preferred monomers for use in group transfer polymerization are acrylic and maleimide monomers of the formula CH₂=C(Y)X and

and mixtures thereof,

wherein:

X is -CN, -CH=CHC(O)X' or -C(O)X';

Y is -H, -CH₃, -CN or -CO₂R, but with the proviso that when X is -CH=CHC(O)X', Y is -H or -CH₃;

X' is -OSi(R¹)₃, -R, -OR or -NR'R'';

each R¹, independently of one another, is a hydrocarbon radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical having up to 20 carbon atoms or -H, with the proviso that at least one R¹ group is not -H;

R is:

(a) a hydrocarbon radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical having up to 20 carbon atoms;

(b) a polymer residue containing at least 20 carbon atoms;

(c) a residue of (a) or (b) containing one or more ether oxygen atoms within aliphatic portions thereof;

(d) a residue of (a), (b) or (c) containing one or more functional substituents which are not reactive under polymerization conditions; or

(e) a residue of (a), (b), (c) or (d) containing one or more reactive substituents of the formula -Z'(O)C-C(Y¹)=CH₂, wherein Y¹ is -H or -CH₃ and Z' is O or NR', wherein R' is as defined below; and

each R' and R'' is independently selected from C₁₋₄alkyl.

Preferred initiators are selected from tetra-coordinated organosilicon, organotin and organogermanium compounds of the formulas (Q')₃MZ, (Q')₂M(Z¹)₂ and [Z¹(Q')₂M)₂O, wherein:

each Q' is independently R¹, OR¹, SR¹ or N(R¹)₂;

R¹ is as defined above for the monomer;

Z is an activating substituent selected from the group consisting of

-OP[OSi(R¹)₃]₂ and mixtures thereof;

R', R'', R and R¹ are as defined above for the monomer ;

Z¹

is;

X² is -OSi(R¹)₃, -R⁶, -OR⁶ or -NR'R'';

R&sup6; is

(a) a hydrocarbon radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical having up to 20 carbon atoms;

(b) a polymer residue containing at least 20 carbon atoms;

(c) a residue of (a) or (b) containing one or more ether oxygen atoms within aliphatic portions thereof;

(d) a residue of (a), (b) or (c) containing one or more functional substituents which are non-reactive under polymerization conditions; or

(e) a residue of (a), (b), (c) or (d) having one or more initiating sites; and

each of R² and R³ is independently selected from -H and a hydrocarbon radical as defined for R⁶ in subparagraphs (a) to (e) above ;

R', R'' and R¹ are as defined above for the monomer;

Z' is as defined above for the monomer;

m is 2, 3 or 4;

n is 3, 4 or 5;

R² and R³ together are:

provided that

is;

X² and either R² or R³ taken together are

provided that Z

is;

and

M is Si, Sn or Ge, provided, however, that when Z

is,

M is Sn or Ge.

Preferred co-catalysts are selected from a source of bifluoride ions, HF₂⁻ or a source of fluoride, cyanide or azide ions or a source of oxyanions, wherein the oxyanions are capable of forming an acid conjugate having a pKa (DMSO) of from about 5 to about 24, preferably from about 6 to about 21, more preferably from 8 to 18, or a suitable Lewis acid, e.g. zinc chloride, bromide or iodide, boron trifluoride, an alkylaluminum oxide or an alkylaluminum chloride, or a selected Lewis base.

Additional details concerning group transfer polymerization can be obtained from the previously mentioned patents and patent applications, the disclosures of which are expressly incorporated by reference.

Razuvaev et al., Vysokomol. Soedin. (B), 25 (2): 122-125 (1983) disclose polymerization of methyl methacrylate and/or styrene initiated by a mixture of silicon tetrachloride and mercury, tin or lead alkyls at 20-50 ºC. Sakurai et al., Tetrahedron Lett., 21: 2325-2328 (1980) disclose mercury iodide-catalyzed isomerization of (trimethylsilylmethyl)chloromethyl ketone to (1-chloromethylethenyl)oxytrimethylsilane.

Burlachenko et al., Zhur, Obshchei Khim., 43 (8): 1724-1732 (1973) disclose triethylsilyl bromide and mercury bromide-catalyzed isomerization of cis-ketene silyl acetals into the trans isomers. Litvinova et al., excerpt from Dokl. Akad. Nauk. SSSR, 173 (3): 578-580 (1967); CA 67: 32720j, disclose the mercury iodide-catalyzed rearrangement of triethylacetonylsilane to (isopropenyloxy)triethylsilane.

Baukov et al., excerpt from Dokl. Akad. Nauk. SSSR, 157 (1): 119-121 (1964); CA 61: 8333f, disclose the mercuric iodide-catalyzed rearrangement of [(1-methoxy-1-ethenyl)oxy]triethylsilane to methyl 2-triethylsilyl acetate.

Satchell et al., Qtr. Rev. Chem. Soc., 25: 171 (1971) reveal that mercury halides are very weak Lewis acids.

Weber describes in "Silicon Reagents for Organic Synthesis" New York, 1983, Chapter 3, pp. 21-39 the preparation and reactions of trimethylsilyl iodide, bromide and trifluoromethanesulfonate (triflates). These reagents are used as catalysts for the cleavage of chemical bonds in organic compounds and as silylating agents. They are often used in conjunction with organic bases such as pyridine. A more comprehensive overview of reactions catalyzed by trimethylsilyl triflates and trimethylsilyl esters of the "Nafion" perfluorosulfonic acid resin is provided by Noyori et al., Tetrahedron, 37 (23), 3899 (1981).

US 3,478,007 discloses polymerization of unsaturated cyclic hydrocarbons using aluminum chloride and a trialkylsilicon halide as catalyst; AlCl3 and trimethylsilyl chloride are examples.

Toshima et al., Kogyo Kagaku Zasshi 72 (4), 984 (1969) disclose trimethylsilyl chloride and mercuric chloride-catalyzed polymerization of styrene.

The above publications do not suggest the use of trialkylsilyl halides with or without the addition of Lewis acids or mercury compounds as catalysts for group transfer polymerization.

The above-mentioned US patent 4,732,955 discloses group transfer polymerization of one or more acrylate or acrylamide monomers in the presence of a mercury compound of the formula R⁷HgJ, wherein R⁷ is a C₁₋₁₀ hydrocarbon radical, or HgL₂, wherein L is J or ClO₄.

The present invention provides an improved process for group transfer polymerization wherein the catalyst is a selected polymerization non-initiating silane or a mixture thereof with a suitable mercury compound and/or Lewis acid.

Summary of the invention

The present invention resides in a process for group transfer polymerization (GTP) comprising contacting under polymerization conditions at least one monomer selected from acrylic and maleimide monomers with (i) a tetra-coordinated organosilicon, tin or germanium compound having at least one initiating site and (ii) a catalyst which is a suitable Lewis acid or mercury compound, the process being further characterized in that the catalyst consists essentially of:

(a) about 10 to 100 mole percent of a silane of the formula (R¹)₃Si-Z², wherein:

each R¹ independently represents a hydrocarbon radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical having up to 20 carbon atoms or -H, with the proviso that at least one R¹ group is not -H; and

Z² is selected from I, Br, Cl, CF₃SO₃, CF₃CO₂, Clo₄ and SO₄ ; and

(b) 0 to about 90 mole percent of at least one of the defined Lewis acids or mercury compound, provided, however, that when Z2 is other than J, at least 0.5 mole percent of the Lewis acid or mercury compound selected from R7HgJ, HgJ2 and Hg(ClO4)2 is present.

Detailed description of the invention

The Lewis acids defined for use in the preparation of the invention are zinc iodide, zinc chloride, bromide, boron trifluoride, an alkylaluminum oxide, an alkylaluminum chloride, cadmium iodide, ferric chloride and tin(II) chloride.

The defined mercury compounds are those of the formula R⁷HgJ and HgL⁷, where

R7 is a hydrocarbon radical having 1 to 10 carbon atoms; and

L is I, Br, Cl, CF₃CO₂, ClO₄, SO₄, trifluoromethanesulfonate (triflate) or O.

Preferably L is iodide or bromide, most preferably iodide.

When the Lewis acid or mercury compound is present in the catalyst composition of the invention, it may be supported on an inert, insoluble support, such as carbon.

The process of the invention can be carried out with or without a solvent. Suitable solvents are generally those disclosed in the aforementioned patents and patent applications, non-coordinating liquids such as hydrocarbons or chlorinated hydrocarbons, which are preferred when mercury compounds are present in the catalyst compositions. Preferred acrylic monomers and initiators disclosed in the aforementioned patents are also preferred in the process; see especially U.S. Patents 4,508,880 and 4,732,955. Acrylates and N,N-dialkylacrylamides are most preferred monomers for the process of this invention.

Process conditions such as temperature, pressure, concentrations of starting materials, monomer to initiator ratio, catalyst to initiator ratio, and precautions against moisture and other hydroxylated impurities are as described in the previously described patents and patent applications. Additional details are provided below.

The amount of catalyst composition used in the process of the invention should be at least about 0.01 moles per mole of starting initiator, preferably about 0.05 to about 10 moles per mole of starting initiator, although amounts as high as about 100 moles per mole of initiator can be tolerated.

Preferred catalyst compositions are those containing from about 0.5 mole percent to about 80 mole percent of a mercury compound or Lewis acid as previously defined. Catalyst compositions in which at least one component is an iodide are most preferred.

It is expressly stated that some, but not all, of the components of the catalyst composition of the invention are themselves catalysts for GTP. Components which catalyze GTP include the aforementioned silane, the Lewis acids mentioned above except cadmium iodide, ferric chloride and stannous chloride, and mercury compounds of the formula R7HgJ and HgL2, where R7 is as defined above and LJ or ClO4. However, it can be seen from the following experiments and examples that catalyst compositions containing both silane and the mercury compound or Lewis acid are surprisingly more active than the individual components, especially at low temperatures. Example 21 shows that a composition of the invention is an active catalyst for the polymerization of ethyl acrylate using GTP at -78°C, although the catalyst components are individually ineffective. This unexpected catalytic synergism found in the present catalyst mixtures is particularly useful when it is desired to minimize the amount of mercury or Lewis acid used in the polymerization process. The present preferred compositions are also more effective catalysts for the polymerization of (meth)acrylates than the individual components, especially mercury compounds, which alone are essentially inactive for the polymerization of these monomers.

In the following examples of the invention, the weight and number average molecular weights of the polymer products (Mw, Mn) were measured by gel permeation chromatography (GPC). The polydispersity of the polymer is defined by D=Mw/Mn. Unless otherwise indicated, the "living" polymer products were quenched by exposure to moist air or methanol prior to molecular weight determinations. Parts and percentages are by weight and temperatures are in degrees Celsius unless otherwise indicated.

In some cases, catalyst activity is measured by the time elapsed before exothermic polymerization begins, with shorter induction times indicating higher activity. If catalyst activity is low, the polymer can be formed without a detectable increase in temperature.

Preferred embodiments of the present invention are shown in Examples 3, 5, 6, 8 and 21.

example 1

In a dry 100 mL round bottom flask (RB) were added 20 mL of toluene, 0.40 mL of [(1-methoxy-2-methyl-1-propenyl)oxy]trimethylsilane (MTS) (2.0 mmol) and 40 μL of iodotrimethylsilane (TMSI, 0.28 mmol). To the mixture stirred under argon was added 5 mL of ethyl acrylate (46 mmol). No exothermic reaction was observed. After about two hours, 0.66 mL of a 0.003 M mercuric iodide solution in benzene (d6) (0.002 mmol) was added. The temperature increased, indicating polymerization. An aliquot (A) was removed. An additional 3 mL of ethyl acrylate was added and after polymerization an aliquot (B) was removed. This procedure was repeated twice, yielding aliquots C and D. Poly(ethyl acrylate) was recovered from each aliquot: Aliquot Mn (Theory)

Example 2

A. Example 1 was repeated using 0.009 mmol mercuric iodide and initially without TMSI. A temperature rise indicating polymerization occurred after about 45 minutes.

B. The experiment in Part A was repeated except that 2.0 mmol of TMSI was also added. Exothermic polymerization occurred within 1 minute, indicating more efficient catalysis.

Example 3

In a dry 100 mL RB flask were added 20 mL of toluene, 1 mL of a 0.003 M mercuric iodide solution in benzene (0.003 mmol), 2.0 mL of [(1-[2-trimethylsiloxyethoxy-2-methyl-1-propenyl)oxy]trimethylsilane (TTEB), and 44 μL of TMSI (0.31 mmol). To this solution was added 10 mL of ethyl acrylate (92 mmol). Exothermic polymerization occurred. After polymerization appeared to be complete, 0.52 mL of 1,3-dioxolane was added to quench the "living" polymer. A quantitative yield of the poly(ethyl acrylate) (PEA) was obtained. GPC: Mn 1910; Mn (theory) 1700; D 1.16. Hydrolysis of the end groups at reflux with THF/water/HCl gave the PEA-diol with 100% difunctionality by NMR.

Example 4

A. In a dry 100 mL RB flask were added 0.2 g of zinc iodide (0.6 mmol), 20 mL of toluene, 1.97 mL of TTEB (6.2 mmol) and 44 μL of TMSI (0.31 mmol). To this mixture was added 10 mL of ethyl acrylate over 11 minutes. The temperature of the mixture rose rapidly during the monomer addition and an ice bath was used to keep the temperature below 31 ºC. The polymer was quenched with 1,3-dioxolane and stripped to give a quantitative yield of PEA. GPC: Mn 1800; Mn (theory) 1700; D 1.19.

B. The experiment from Part A was repeated except that no TMSI was added. Polymerization occurred after an induction time of 17 min. The recovered polymer had a bimodal molecular weight distribution, indicating little molecular weight control. GPC: Mn 1120; Mn (theory) 1700; D 1.49.

Example 5

In a 100 mL RB flask, 0.05 g of zinc iodide (0.16 mmol), 20 mL of toluene, 0.32 mL of TTEB (1.0 mmol), and 15 mL of ethyl acrylate were added. No polymerization was observed. After 1.25 h, 10 μL of TMSI was added. Exothermic polymerization occurred, requiring external cooling. A quantitative yield of PEA was obtained. GPC: Mn 20,200; Mn (theory) 19,000; D 1.25.

Example 6

In a 100 mL RB flask were added 0.035 g of zinc bromide (0.16 mmol), 20 mL of toluene, 0.32 mL of TTEB (1.0 mmol) and 11 mL of ethyl acrylate. No exothermic reaction was observed. To the mixture was then added 0.26 mL of bromotrimethylsilane. A rapid rise in temperature was observed and a quantitative yield of PEA was obtained. GPC: Mn 15,000; Mn (theory) 10,300; D 1.24.

Example 7

To a 100 mL flask containing 0.1 g mercuric iodide (0.22 mmol), 20 mL toluene, 0.64 mL TTEB (2.0 mmol), and 0.1 mL TMSI (0.7 mmol) was added 10 mL of methyl methacrylate (MMA). No exothermic reaction was observed. An additional 0.3 mL of TMSI was added (total 2.8 mmol). Exothermic polymerization occurred. A 91% yield of PMMA was obtained. GPC: Mn 3310; Mn (theory) 4800; D 1.07.

Examples 8-20

General procedure: Into a 50 mL bottle with a septum were added 3 mL of toluene, 0.4 mL of MTS (2.0 mmol), 3 mL of ethyl acrylate (0.028 mol), and 2.0 mmol of silane under argon; after 15 min, during which no polymerization was detected, 0.20 mmol of a selected Lewis acid was added, except in Examples 8 and 13. The bottle was shaken by hand and checked periodically for exothermic polymerization. The results are summarized in Table 1.

Experiments 1-5

The procedure of Examples 8-20 was followed except that the silane was omitted and the Lewis acid was added to the initiator and solvent prior to monomer addition; these non-inventive experiments serve as controls for Examples 9, 14, 17, 18 and 20, respectively. The results are presented in Table 1. Table 1 Example Silane Lewis acid Exo(min) * none Experiment no polymer TMS = Trimethylsilyl; Tf = Triflate; NA = not available;* exo (min) is the time (minutes) before an exothermic temperature rise was observed. (a) = no exothermic reaction was observed; the polymer formed slowly overnight; "none" means no exothermic reaction and no polymerization.

Example 21

Separate experiments have shown that acrylates are not polymerized by GTP at -78 ºC in the presence of a mercury compound or a silane alone.

To a 100 mL round-bottom flask were added 20 mL of toluene, 0.40 mL of MTS (2.0 mmol), 0.66 mL of a 0.003 M mercuric iodide solution in benzene, and 10 mL of ethyl acrylate. The solution was cooled to -78 ºC, and 40 μL of TMSI (0.28 mmol) was added. After 69 min, an aliquot (A) was removed for GPC analysis. At this time, an additional 40 μL of TMSI (0.28 mmol) was added. A slight exotherm was observed; the mixture was allowed to stir for 33 min, then quenched with 1 mL of methanol. After warming to room temperature, a quantitative yield of PEA was obtained (B).

GPC: (A) Mn 2510; D 1.21;

(B) Mn 4190; D 1,08.

The molecular weight of sample A indicates that about 60% of the monomer was consumed before the second addition of TMSI.

Example 22

In a dry 50 ml bottle equipped with a septum, 3 ml of toluene, ethyl acrylate (0.019 mol), MTS (2.0 mmol) and mercuric chloride (0.022 mmol) supported on carbon (12% HgCl₂) were added under argon. no polymerization occurred. TMSI (0.14 mmol) was then added, whereupon an exothermic temperature rise occurred within seconds, accompanied by a rapid increase in viscosity, thus proving polymerization.

Claims (10)

1. A process for group transfer polymerization (GTP) comprising contacting under polymerization conditions at least one monomer selected from acrylic and maleimide monomers with (i) a four-coordinate organosilicon, tin or germanium compound having at least one binding site for initiation and (ii) a catalyst which is a suitable Lewis acid or a mercury compound, the process further characterized in that the catalyst consists essentially of: (a) about 10 to 100 mole percent of a silane of the formula (R¹)₃Si-Z², wherein: each R¹ is, independently, a hydrocarbon radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical containing up to 20 carbon, or hydrogen atoms, provided that at least one R¹ group is not -H; and Z² is selected from I, Br, Cl, CF₃SO₃, CF₃CO₂, ClO₄ and SO₄ and (b) 0 to about 90 mole percent of at least one Lewis acid selected from zinc, iodide, zinc chloride, zinc bromide, boron trifluoride, an alkylaluminum oxide, a Alkyl aluminum chloride, cadmium iodide, ferric chloride, tin (II) chloride or a mercury compound selected from R7HgI and HgL2, wherein R7 is a hydrocarbon radical having 1 to 10 carbon atoms and is LJ, Br, Cl, CF3CO2, ClO4, SO4, trifluoromethanesulfonate or O, provided, however, that when Z2 is other than J, at least 0.5 mole percent of the Lewis acid or mercury compound selected from R7HgI, HgI2 and Hg(ClO4)2 is present. 2. The process of claim 1 wherein the amount of catalyst is at least about 0.01 mole per mole of initiator. 3. The process of claim 1 wherein the amount of catalyst is at least about 0.05 to 10 moles per mole of initiator. 4. The process of claim 1, wherein the catalyst consists of about 10-99.5 mole % of (a) and about 0.5-90 mole % of (b), the mixture of (a) and (b) totaling 100%. 5. The method of claim 4, wherein at least one component of the mixture is an iodide. 6. The process of claim 4, wherein the catalyst components are iodotrimethylsilane and mercuric iodide. 7. The process of claim 4, wherein the catalyst components are iodotrimethylsilane and zinc iodide. 8. The process of claim 4, wherein the catalyst components are bromotrimethylsilane and zinc iodide. 9. The process of claim 4, wherein the catalyst components are chlorotrimethylsilane and zinc iodide. 10. The process of claim 1, wherein the catalyst components are iodotrimethylsilane.