Branched Polymers Made Using Multifunctional Coupling Agents

Abstract

Branched block copolymers, derived from alkenyl aromatic hydrocarbon-1,3-diene monomer system, and branched polyisoprene homopolymers, derived from isoprene, are obtained by polymerization in the presence of an anionic initiator; at a temperature from 0° C. to 100° C.; followed by coupling with a multifunctional coupling agent of formula (R.sup.1O).sub.3Si—Y—Si(OR.sup.2).sub.3, wherein R.sub.1 and R.sub.2 are independently C.sub.1-C.sub.6 alkyl groups; and Y is a C.sub.2-C.sub.8 alkylene group. The polymers thus obtained can be used in many applications, including rubber cements having high solids content and low zero shear viscosities, and for producing aqueous latices therefrom.

Claims

1. A branched polymer having a formula of (A-B).sub.m(R.sub.1O).sub.3-mSi—Y—Si(R.sub.2O).sub.3-n(B-A).sub.n, or (C).sub.m(R.sub.1O).sub.3-mSi—Y—Si(R.sub.2O).sub.3-n(C).sub.n, wherein each A block independently comprises at least 90 mole percent of an alkenyl aromatic hydrocarbon; wherein the one or more A blocks form 8-13 weight percent of the total weight of the branched block copolymer; each B block is independently a poly(1,3-diene) block comprising at least 90 mole percent of one or more 1,3-dienes; each C block is independently a polyisoprene; each A block independently has a weight average molecular weight from 9-15 kg/mol, each B block independently has a weight average molecular weight from 75-150 kg/mol; and each C block has a weight average molecular weight from 400-1000 kg/mol; R.sub.1 and R.sub.2 are independently H, or C.sub.1-C.sub.6 alkyl groups; Y is a C.sub.2-C.sub.8 alkylene group; m and n are integers independently having values from 1-3; and wherein the branched polymer has a coupling efficiency (CE) of at least 40%.

2. The branched polymer of claim 1, wherein (m+n) has a value from 3-6.

3. The branched polymer of claim 1, wherein Y is —CH.sub.2CH.sub.2—, and R.sub.1 and R.sub.2 are hydrogen, methyl groups or ethyl groups.

4. The branched polymer of claim 1, wherein the 1,3-diene is isoprene, and the alkenyl aromatic hydrocarbon is styrene.

5. The branched polymer of claim 1, wherein the branched polymer is a branched polyisoprene homopolymer having the formula (C).sub.m(R.sub.1O).sub.3-mSi—Y—Si(R.sub.2O).sub.3-n(C).sub.n.

6. The branched polymer of claim 1, wherein the branched polymer is a branched block copolymer having the formula of (A-B).sub.m(R.sub.1O).sub.3-mSi—Y—Si(R.sub.2O).sub.3-n(B-A).sub.n.

7. The branched polymer of claim 1, prepared using a multifunctional coupling agent is selected from the group consisting of 1,2-bis(trimethoxysilyl)ethane (BTMSE), 1,2-bis(triethoxysilyl)ethane (BTESE), and mixtures thereof.

8. The branched polymer of claim 1, wherein the C block has a weight average molecular weight from 500-700 kg/mol.

9. A process for preparing a branched polymer, the process comprising: (i) polymerizing a first monomer comprising at least 90 mole percent of an alkenyl aromatic hydrocarbon, at a temperature from 0° C. to 100° C., to form a polymer block A; and adding a second monomer comprising at least 90 mole percent of one or more 1,3-dienes and polymerizing at a temperature from 0° C. to 100° C., to form a polymer block B; or (ii) polymerizing isoprene at a temperature from 0° C. to 100° C., to form a polymer block C; (iii) adding a multifunctional coupling agent of formula (R.sub.1O).sub.3Si—Y—Si(OR.sub.2).sub.3; and forming a branched block copolymer having a formula (A-B).sub.m(R.sub.1O).sub.3-mSi—Y—Si(R.sub.2O).sub.3-n(B-A).sub.n from steps (i) and (iii), or a branched polyisoprene homopolymer having a formula (C).sub.m(R.sub.1O).sub.3-mSi—Y—Si(R.sub.2O).sub.3-n(C).sub.n from steps (ii) and (iii); wherein each A block independently comprises at least 90 mole percent of the alkenyl aromatic hydrocarbon, and the one or more A blocks form 8-13 weight percent of the total weight of the branched polymer; each B block is independently a poly(1,3-diene) block comprising at least 90 mole percent of one or more 1,3-dienes; each C block is a polyisoprene block; each A block independently has a weight average molecular weight from 9-15 kg/mol, each B block independently has a weight average molecular weight from 75-150 kg/mol, and each C block independently has a weight average molecular weight from 400-1000 kg/mol; R.sub.1 and R.sub.2 are independently H, or C.sub.1-C.sub.6 alkyl groups; Y is a C.sub.2-C.sub.8 alkylene group; m and n are integers independently having values from 1-3; and the branched polymer has a coupling efficiency (CE) of at least 40%.

10. The process of claim 9, wherein the branched polymer is formed as a rubber cement having a solids content from 5 wt. % to 35 wt. %.

11. The process of claim 10, wherein the branched block copolymer has a formula (A-B).sub.m(R.sub.1O).sub.3-mSi—Y—Si(R.sub.2O).sub.3-n(B-A).sub.n, and wherein the rubber cement has a zero shear viscosity of less than 25,000 mPas in a solids content range from 15 wt. % to 25 wt. %; a cis content from 70% to 95%; and a weight average molecular weight from 350 to 700 kg/mol.

12. (canceled)

13. (canceled)

14. The process of claim 10, wherein the branched polyisoprene homopolymer has a formula of (C).sub.m(R.sub.1O).sub.3-mSi—Y—Si(R.sub.2O).sub.3-n(C).sub.n, and wherein the rubber cement has a zero shear viscosity of less than 80,000 mPas in a solids content range from 15 wt. % to 25 wt. %; a cis content from 70% to 95%; and a weight average molecular weight from 1,000 to 3500 kg/mol.

15. The process of claim 10, wherein the process further comprises an anionic initiator.

16. (canceled)

17. An article formed from the branched polymer of claim 1.

18. A film formed from the branched polymer of claim 1.

19. The film of claim 18, wherein the film has a tensile strength of from 20 MPa to 40 MPa.

20. The film of claim 18, wherein the film has an elongation of from 500% to 1250% and a tear strength of from 15 kN/m to 35 kN/m.

Description

EXAMPLES

[0027] Polymer molecular weights (called “weight average molecular weight” or “GPC molecular weight” herein) were determined by HMW-GPC (gel permeation chromatography) using polystyrene calibration standards. Median particle size of the latices was determined by laser diffraction using a Beckman Coulter LS13320. Solids content was measured with a Sartorius MA35 moisture balance.

[0028] Coupling efficiency for the reaction with the multifunctional coupling agent was determined by GPC from the peak integration ratios of the uncoupled polymer relative to the higher molecular weight coupled polymer.

[0029] Coagulant solution/dispersion was prepared by dissolving/dispersing Ca(NO.sub.3).sub.2.4H.sub.2O (˜14%) and CaCO.sub.3 (˜5%) in water at 60° C. while stirring. All the latexes, including the reference sample, were compounded with 5 phr of a commercially available masterbatch composition (containing sulphur, accelerators and anti-oxidant) and stabilized with a commercially available surfactant. The compounds were diluted with demineralized water to obtain the required solid content of 30%. The pH was adjusted to 11-11.5 by addition of a 1M KOH solution and the compounds were stored at ambient temperature while stirring.

[0030] For the coagulant dipping exercise, metal plates were used and the standard dipping procedure was applied. Films were dipped after 1, 3 and 6 days of maturation. Mechanical properties of the dipped films were determined according to ASTM D412/ISO37 (Die C) using an Instron 3365 tensile bench equipped with a 500N load cell and a long-range travelling extensometer. The tensile properties are shown in Table 5.

Examples 1-5. Preparation of Branched Polyisoprene Homopolymers

[0031] Polymerizations were conducted under a nitrogen atmosphere in a 10 L stainless steel reactor equipped with agitator, cooling, temperature probe, pressure probe and auxiliaries for addition/withdrawal of solvent, monomers and other reagents. Solvents and monomers were purified over alcoa prior to use. As a general procedure, the reactor was charged with 5 L of dry solvent and 450 g of isoprene and heated to 60° C. A dilute s-BuLi solution (0.04 M) was added to the mixture to initiate the polymerization. After conversion of the required amount of monomer to the required molecular weight, the reaction was terminated by addition of the coupling agent (BTMSE or BTESE) in a molar ratio of living chains/coupling agent of 4/1. In some cases, this procedure was repeated once or twice until full conversion of monomer.

[0032] BTMSE and BTESE were evaluated in isoprene polymerizations at different living chain concentrations. The results are summarized in Table 1. The data shows that BTMSE and BTSE have comparable coupling performance.

TABLE-US-00001 TABLE 1 Coupling reactions of BTMSE and BTESE with different concentrations of living polyisoprene chains. Living chains Uncoupled Uncoupled Example Coupling agent (mmol) after 1 h (%) final (%) 1 BTMSE 0.8 23 22 2 BTMSE 1 20 17 3 BTMSE 2 14 14 4 BTESE 0.55 33 29 5 BTESE 0.8 27 23

Examples 6-8: Preparation of Branched Polyisoprene Homopolymers

[0033] These were prepared as rubber cements using the procedure described above. Results are shown in Table 2. The control sample was a linear (unbranched) polyisoprene made without using a coupling agent.

TABLE-US-00002 TABLE 2 Branched Polyisoprenes prepared. cis Number Coupling GPC Mw content Example of runs agent (kg/mol) (%) Control-1 1 Not used 3000 88 6 1 BTMSE 1660 78 7 2 BTESE 1083 75 8 2 BTMSE 1260 82

Examples 9-11: Preparation of Branched Polyisoprene Rubber Latex

[0034] The rubber cement sample was transferred to a bench scale latex production facility equipped with an in-line high shear mixing device with dosing pumps for polymer and soap solutions Emulsions were produced under standardized emulsification conditions from a fixed ratio of cement and aqueous solution of a potassium salt of disproportionated rosin acid. The emulsion was subsequently solvent stripped to obtain a dilute latex, which was concentrated by creaming after addition of sodium alginate. The results are shown in Table 3. Control-2 is a reference polyisoprene rubber latex prepared from the Control-1 rubber cement described above.

TABLE-US-00003 TABLE 3 Branched polyisoprene latices prepared. Cement Dilute latex Concentrated latex solids Soap R/S Solids Solvent PSmed Solids Viscosity PSmed Example (wt %) (wt %) ratio pH (wt %) (ppmr) (μ) pH (wt %) (cPs) (μ) Control-2  9 1 12.3 11.5 12 250 1.1 11.3 64 80 1.3  9 20 1.2 11.5 11.8 15.3 495 1.8 11.4 53 46 2 10 15 0.8 12.1 11.6 8.7 255 1 11.5 61 106 1.2 11 16 0.6 12.8 11.4 8 300 0.7 11.7 71 208 0.9 R/S ratio: Rubber/Soap ratio. PSmed: Median particle size

TABLE-US-00004 TABLE 4 Tensile Properties of Cured Films. Tensile Tear Film strength Elonga- Young's strength Example (MPa) tion modulus (MPa) (kN/m) Control-3 28 780 0.13 28 12 (latex ex. 10) 24 663 0.22 27 13 (latex ex. 11) 23 780 0.25 21

[0035] Table 4 shows that the tensile properties of the dipped films made from the branched polyisoprenes (Examples 12 and 13) made using the multifunctional coupling agents are very good and comparable to those seen with the control sample film (Control-3).

Example 14. Preparation of Branched Styrene-Isoprene Block Copolymers

[0036] The polymerization was conducted under a nitrogen atmosphere in a 10 L stainless steel reactor equipped with agitator, cooling, temperature probe, pressure probe and auxiliaries for addition/withdrawal of solvent, monomers and other reagents. Solvent and monomers were purified over alcoa prior to use. The reactor was charged with 5 L of dry solvent and 400 g of styrene and heated to 60° C. A dilute s-BuLi solution (0.04 M) was added to the mixture to initiate the polymerization. After conversion of the styrene, 3 kg of isoprene monomer was charged. After conversion of the second monomer to the required molecular weight, the reaction was terminated by addition of the BTMSE coupling agent in a molar ratio of living chains/coupling agent of 4/1. The results are shown in Table 5. Control-4 is a commercial lot sample of polyisoprene made using GPTS (glycidylpropyl trimethoxysilane) as the coupling agent.

TABLE-US-00005 TABLE 5 CE means coupling efficiency. DoB means degree of branching. PS block SI diblock Coupling CE DoB Example GPC MW (kg/mol) GPC MW (kg/mol) agent Control-4 10.8 159 GPTS 95 2.8 14 10.9 157 BTMSE 89 4.1

Example 15. Preparation of Branched Styrene-Isoprene Block Copolymer Latex

[0037] The rubber cement sample from Example 14 was transferred to a bench scale latex production facility equipped with an in-line high-shear mixing device with dosing pumps for polymer and soap solutions. The emulsion was produced under standardized emulsification conditions from a fixed ratio of cement and aqueous solution of a potassium salt of disproportionated rosin acid. The emulsion was subsequently solvent-stripped to obtain a dilute latex, which after addition of sodium alginate was concentrated by creaming. The results are shown in Table 6.

TABLE-US-00006 TABLE 6 Cement Dilute latex Concentrated latex solids Soap Solids Solids Viscosity Example (wt %) (wt %) R/S ratio (wt %) Psmed (μ) pH (wt %) (cPs) Psmed (μ) 15 15.3 0.9 17.0 14.4 1.22 11.2 60.6 62 1.20 R/S ratio: Rubber/Soap ratio. PSmed: Median particle size.

[0038] Example 16 represents a dipped film made from the branched styrene-isoprene block copolymer latex of Example 15. Control 5 represents a dipped film made from the branched styrene-isoprene block copolymer latex derived from the block copolymer of Control 4. Table 7 shows that the tensile properties of the dipped films made from the branched styrene-isoprene block copolymer made using the multifunctional coupling agent (Example 16) are very good and comparable to those seen with the control sample film (Control-5).

TABLE-US-00007 TABLE 7 Tensile Modulus Tear Example strength 500% Elongation strength Control 5 21.4 1.62 1089 24.7 16 20.4 1.43 1113 27.3

[0039] For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained. It is noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the,” include plural references unless expressly and unequivocally limited to one referent. As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.

[0040] As used herein, the term “comprising” means including elements or steps that are identified following that term, but any such elements or steps are not exhaustive, and an embodiment can include other elements or steps. Although the terms “comprising” and “including” have been used herein to describe various aspects, the terms “consisting essentially of” and “consisting of” can be used in place of “comprising” and “including” to provide for more specific aspects of the disclosure and are also disclosed.

[0041] Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by one of skill in the art to which the disclosed disclosure belongs. the recitation of a genus of elements, materials or other components, from which an individual component or mixture of components can be selected, is intended to include all possible sub-generic combinations of the listed components and mixtures thereof.

[0042] The patentable scope is defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. To an extent not inconsistent herewith, all citations referred to herein are hereby incorporated by reference.