JP2015519466A - Alkylhydroxylamine compounds and their use for terminating free radical polymerization - Google Patents

Abstract

The present invention uses N-isopropylhydroxylamine (IPHA) or a salt thereof in combination with either a primary or secondary alkylhydroxylamine, or at least two primary alkylhydroxylamines to terminate the free radical polymerization reaction. Provide a method. A method for producing an elastomer using the polymerization terminator is also provided. [Selection figure] None

Description

  The present invention relates to a method for terminating a free radical polymerization reaction using N-isopropylhydroxylamine (IPHA) or a salt thereof in combination with a primary or secondary alkylhydroxylamine or a salt thereof. Also provided is a method for producing an elastomer using the polymerization terminator.

  Free radical initiated emulsion polymerization reactions to make elastomers such as styrene-butadiene rubber, butadiene rubber and acrylonitrile-butadiene rubber often involve the use of a polymerization terminator to terminate the polymerization reaction. In order to produce a rubber product with the desired characteristics, the polymerization reaction is stopped when a certain degree of monomer conversion has taken place.

  US Pat. No. 3,148,225 teaches the use of N, N-dialkylhydroxylamines such as N, N-dimethylhydroxylamine as popcorn polymer inhibitors in the preparation of synthetic rubbers. However, previously and presently used polymerization terminators are known to have one or more disadvantages.

  As discussed in US Pat. No. 3,148,225 and European Patent No. 1083185, N, N′-diethylhydroxylamine (DEHA) is a widely used polymerization terminator but is relatively volatile. Be easily removed by non-reactive monomers during the steam distillation stage. This in turn can result in insufficient DEHA present in the resulting latex emulsion, preventing further free radical polymerization from occurring, and can also cause Mooney viscosity drift. There is sex. In addition, subsequent emulsion polymerization utilizing the recovered and recycled monomer stream inactivates a portion of the initiator package and ultimately requires an excessive amount of initiator that requires the use of a larger amount of initiator. DEHA may be included. The use of DEHA can also lead to the formation of regulated nitrosamine precursors. DEHA is sometimes combined with a non-volatile free radical scavenger such as sodium dimethyldithiocarbamate (SDD) or sodium tetrasulfide (ST) to reduce the Mooney viscosity drift of the resulting latex. However, SDD can lead to the formation of nitrosamine precursors, and ST can generate toxic and corrosive hydrogen sulfide.

  N-isopropylhydroxylamine (IPHA) is also widely used as a polymerization terminator and does not contribute to the formation of any regulated nitrosamines as discussed in US Pat. No. 5,384,372, but is good. It has the advantage of providing Mooney viscosity control. Although IPHA can provide control of unwanted gas phase polymer formation (popcorn polymer), its effectiveness can vary depending on equipment conditions.

  EP 1083185 describes the use of nitrosamine inhibitors in combination with secondary alkyl hydroxylamines that can otherwise generate nitrosamines in emulsion and rubber processing. The advantages and disadvantages of IPHA and DEHA are discussed in this patent document.

  IPHA or a salt thereof is, for example, but not limited to, selected from the group consisting of N-isopropylhydroxylamine, N-isopropylhydroxylamine acetate, N-isopropylhydroxylamine hydrochloride, N-isopropylhydroxylamine sulfate, and mixtures thereof Can be done.

  A mixture of IPHA and hydroxylamine (HA) is provided in WO 2002/0038617 as a nitrosamine-free polymerization terminator that better blocks popcorn polymer formation compared to IPHA alone. However, hydroxylamine degrades rapidly, especially in the presence of metal ions, which creates significant problems in storage and handling. On the other hand, US Pat. No. 5,504,168 describes a mixture of polysulfide and IPHA used as a polymerization terminator for an emulsion polymerization system.

  WO 1998/0051714 teaches the use of N-ethylhydroxylamine (EHA) or a salt thereof as a polymerization terminator for free radical polymerization. This document states that EHA is less volatile than DEHA and IPHA and can be mixed with other polymerization terminators such as IPHA, DEHA, sodium polysulfide, and sodium dimethyldithiocarbamate. Furthermore, EHA does not produce undesirable nitrosamines.

  WO 2000/0042079 discloses sterically hindered alkylhydroxylamines such as N-tert-butylhydroxylamine and N, N-isopropylmethylhydroxylamine, and their use as free radical scavengers and polymerization terminators. ing.

  US Pat. No. 6,723,255 describes a polymerization termination composition containing at least one hydrophilic radical scavenger and at least one hydrophobic radical scavenger. This document shows that polymerization terminators with fewer carbon atoms have greater volatility and water solubility.

  In view of the above implementation and development, there remains a need for new and improved polymerization terminators that exhibit at least two or more of the following properties: 1) excellent polymerization termination / Mooney viscosity control, 2) good Storage stability / EH & S profile, 3) does not form detectable levels of regulated nitrosamines, and 4) can provide consistent popcorn polymer regulation.

  The present invention provides an emulsion comprising at least one monomer from isopropylhydroxylamine (IPHA) or a salt thereof, and different from said IPHA or a salt thereof, and primary alkylhydroxylamine, secondary alkylhydroxylamine, and mixtures thereof. A method for terminating a free radical initiated emulsion polymerization reaction comprising adding a polymerization terminator comprising at least one alkylhydroxylamine compound selected from the group consisting of:

  In one embodiment, the alkylhydroxylamine is N-methylhydroxylamine (MHA), N-ethylhydroxylamine (EHA), N-propylhydroxylamine (PHA), N-tert-butylhydroxylamine (TBHA), and its A primary alkylhydroxylamine selected from the group consisting of mixtures.

  In some embodiments, the IPHA or salt thereof, and the primary or secondary alkylhydroxylamine are present in the polymerization terminator in a molar ratio of IPHA: alkylhydroxylamine of 40: 1 to 1: 1.

  For example, the primary alkyl hydroxylamine may be TBHA, in which case IPHA or a salt thereof and TBHA are present in the polymerization stopper in a 5: 1 molar ratio of IPHA: TBHA.

  In some embodiments, the polymerization terminator comprises 1-20% by weight IPHA, based on the total weight of hydroxylamine present, and at least two primary alkyl hydroxylamines (AHA). In these embodiments, IPHA or a salt thereof and at least two primary alkyl hydroxylamines are present in the polymerization terminator in a molar ratio of IPHA: primary AHA of 0.02: 1 to 0.1: 1. In general, the polymerization terminator may comprise 30-90% by weight solvent based on the total weight of the polymerization terminator. The solvent can include, for example, water.

The polymerization terminator may be added to the emulsion in an amount of 0.01 to 0.25 parts per hundred parts of the monomer (phm) (active basis). The present invention also provides
1) performing a free radical polymerization of a latex containing a conjugated diene;
2) Isopropylhydroxylamine (IPHA) or a salt thereof, and at least one alkylhydroxylamine selected from the group consisting of primary alkylhydroxylamine, secondary alkylhydroxylamine, and a mixture thereof, which is different from IPHA or a salt thereof. There is also provided a method for producing an elastomer comprising the steps of adding a polymerization terminator comprising a compound; and 3) processing the polymer to form the elastomer.

  In some embodiments, the elastomer can be a rubber selected from the group consisting of styrene-butadiene rubber, butadiene rubber, and acrylonitrile-butadiene rubber.

  The terms “parts” and “phm (parts per hindered monomers)”, as used in the following examples, refer to the weight of polymerization terminator per 100 parts of charged monomer. Refers to the part. The addition amount and range of the polymerization terminator are described in terms of activity of the substance, not as the concentration of product supplied.

  A method for terminating a free radical initiated emulsion polymerization reaction by adding a polymerization terminator that is a combination of isopropylhydroxylamine (IPHA) or a salt thereof and at least one primary or secondary alkylhydroxylamine is provided. Disclosed.

  The combination of the present invention provides excellent polymerization termination / Mooney viscosity control, has very good storage stability / handling issues, and provides good popcorn polymer control. Furthermore, the combination comprising primary alkylhydroxylamine does not form a nitrosamine precursor and allows the production of rubber according to German technical regulations TRGS552.

  IPHA or a salt thereof is, for example, but not limited to, selected from the group consisting of N-isopropylhydroxylamine, N-isopropylhydroxylamine acetate, N-isopropylhydroxylamine hydrochloride, N-isopropylhydroxylamine sulfate, and mixtures thereof Can be done. N-isopropylhydroxylamine is commercially available from ANGUS Chemical Company (Buffalo Grove, Ill.).

  Suitable primary alkyl hydroxylamines and their salts include, but are not limited to, N-methylhydroxylamine (MHA), N-ethylhydroxylamine (EHA), N-propylhydroxylamine (PHA), N-tert- It can be selected from the group consisting of butylhydroxylamine (BHA), and mixtures thereof. Such an IPHA / primary alkylhydroxylamine combination provides excellent polymerization termination / Mooney viscosity control, is stable, and its chemistry does not generate nitrosamine and provides good popcorn polymer control To do.

  Suitable secondary alkyl hydroxylamines can be selected, for example, from the group consisting of, but not limited to, N, N-dimethylhydroxylamine (DMHA), N, N-isopropylmethylhydroxylamine (IPMHA), and mixtures thereof. These combinations provide good polymerization termination, excellent Mooney viscosity control, and popcorn polymer control. Some secondary alkyl hydroxylamines are less desirable than primary alkyl hydroxylamines in combination with IPHA because they have the ability to form nitrosamine precursors.

  In embodiments having IPHA or a salt thereof and primary or secondary AHA, these components are incorporated into the polymerization stopper in a molar ratio of IPHA: (total primary or secondary AHA) from 40: 1 to 1: 1. Exists. For example, the molar ratio of IPHA: (total primary or secondary AHA) present in the polymerization terminator can be, but is not limited to, 20: 1 to 2: 1, and even 15: 1 to 2: 1 ( For example, 10: 1 to 1: 1).

  In some embodiments, the polymerization terminator of the present invention comprises only 1-20% by weight IPHA, based on the total weight of hydroxylamine present, and at least two primary alkyl hydroxylamines (AHA). In these embodiments, the IPHA or salt thereof and the at least two primary alkylhydroxylamines have an IPHA: primary AHA of 0.01: 1 to 0.1: 1 (eg, 0.02: 1 to 0.1: 1 ) In the polymerization terminator at a molar ratio. For example, but not limited to, the polymerization terminators described herein are 1-20 wt% IPHA, 50-70 wt% EHA, and 29-49 wt% based on the total weight of all AHA present. TBHA may be included. Specifically, the polymerization terminator is 10 wt% IPHA, 50 wt% EHA and 40 wt% TBHA, or, for example, 2 wt% IPHA, 55 wt% EHA and 43 wt% TBHA. May be included. These mixtures containing a relatively small amount of IPHA with at least two primary AHAs provide acceptable polymerization in the gas and liquid phases by providing a preferred liquid-gas phase distribution of the polymerization terminating active ingredient (ie, AHA). It should give a stop effect. Furthermore, in order to confirm that the activity of the polymerization terminator in the organic (ie, latex) phase during the radical polymerization reaction is higher, the active ingredient (eg, AHA) has higher solubility in the organic solvent. Having it facilitates its transfer from the aqueous phase to the organic phase.

  In embodiments having IPHA and at least two primary AHA, these components are present in the polymerization stopper in a molar ratio of IPHA: (total primary AHA) from 0.02: 1 to 0.1: 1. For example, the molar ratio of IPHA: AHA present in the polymerization terminator is not limited, but is 20: 1 to 2: 1, or even 15: 1 to 2: 1 (eg, 10: 1 to 1: 1). It can be.

  In this specification, the amount of polymerization terminator (active ingredient, IPHA-AHA mixture) used is about 0.01 to 0.25 part (phm) (activity basis) per 100 parts monomer, for example, limited Is not, but can be from about 0.03 to about 0.2 phm. The mode of adding the polymerization terminator to the emulsion is not particularly limited and should be suitable for the prior art used in the rubber polymerization process. For example, a mixture of IPHA and AHA can be first mixed with a solvent such as water and then added to the emulsion when the desired monomer conversion is achieved.

  The polymerization terminator of the present invention comprising IPHA and primary or secondary AHA or a mixture of at least two primary AHAs (hereinafter referred to as “IPHA: AHA polymerization terminator”) proceeds via a free radical emulsion polymerization mechanism. Can be advantageously used in any addition polymerization system. The emulsion polymerization process can be carried out batchwise or continuously. The method of the present invention can be advantageously applied to, for example, emulsion polymerization reactions that produce styrene-butadiene rubber (SBR), butadiene rubber (BR) and acrylonitrile-butadiene rubber (NBR) and polychloroprene.

  Furthermore, the method of the present invention depends on a free radical polymerization reaction using any specific initiator, activator, reducing agent, complexing agent, buffer, oxygen binding substance, emulsifier, dispersant, modifier, etc. do not do. In general, chain transfer agents can be used to avoid excessive gel formation and adjust the average molecular weight. The type of chain transfer agent used is not particularly limited in the present specification. Other polymerization terminators and radical scavengers may be mixed with the IPHA-AHA polymerization terminators described herein, such as, but not limited to, DEHA, sodium dimethyldithiocarbamate, sodium tetrasulfide, hydroxylamine, Examples include ethylhydroxylamine and sodium nitrite.

  The temperature of the polymerization can range from 0 ° C to 100 ° C. When a thermal polymerization method is used, the polymerization temperature is generally in the range of about 40 ° C to about 70 ° C. Thermal polymerization is generally performed for monomer conversion in the range of 80% to 90%. The temperature for cold polymerization is generally in the range of about 0 ° C to 25 ° C. Cold polymerization is generally performed for monomer conversion in the range of about 55% to 65%.

  Although IPHA has been shown to provide popcorn polymer regulation, its performance can vary depending on the design and conditions of the equipment used for rubber production. The IPHA-AHA polymerization terminator used in the method of the present invention provides more consistent and robust popcorn polymer control compared to using IPHA alone as the polymerization terminator. These polymerization terminators also provide better overall polymerization termination performance compared to DEHA based polymerization terminators. Indeed, in the present specification, when IPHA is mixed with at least one primary alkylhydroxylamine, the regulated nitrosamine contained in the resulting rubber product is emulsified which is polymerized using a DEHA polymerization terminator. Less than detectable levels compared to rubber produced by the polymerization reaction. Finally, the need for an additional free radical scavenger in the monomer recovery portion of the emulsion polymerization reaction zone of the polymerization facility is that when the IPHA-AHA polymerization terminator described herein is used according to the method of the present invention, Reduced.

  The practice of the present invention is further illustrated by reference to the following examples, which are intended to be representative rather than limiting the scope of the invention.

Preparation of Compositions of the Invention (IPHA and Primary or Secondary AHA) Various IPHA-based mixtures were prepared from commercial products, CHAINGARD I-15 hydroxylamine (15% IPHA / 85, commercially available from ANGUS Chemical Company). % Water) and the desired secondary alkylhydroxylamine were prepared by stirring together under nitrogen. Secondary alkylhydroxylamines were prepared separately by known procedures found in the published literature. By varying the relative amount of IPHA used and the desired alkylhydroxylamine added, the ratio of IPHA to the desired alkylhydroxylamine could be achieved. Furthermore, the concentration of the mixture could be adjusted to the desired level by changing the amount of deionized deoxygenated water present in the initial amount of CHAINGUARD I-15.

Polymerization Termination Performance Study The polymerization of styrene and butadiene was conducted in the laboratory using a standard formulation for SBR (styrene butadiene rubber) polymerization.

The standard inhibitor in styrene, t-butylcatechol (TBC), was removed before use. An aqueous mixture of emulsifiers was added to styrene and equilibrated to a reaction temperature of 10 ° C. After this, concentrated butadiene monomer was added and equilibrated to 10 ° C. Finally, the activator mixture was added to initiate the polymerization. The reaction was allowed to proceed until a predetermined conversion level, typically 60% for SBR, was achieved. At that time, the polymerization terminator was injected. The amount of polymerization terminator used in the injection was 0.04 part (activity basis) per 100 parts of monomer. This polymerization terminator was thoroughly mixed in the emulsion. A sample of latex was removed from the reaction vessel and the percent conversion of monomer to polymer was determined by gravimetric analysis on the sample (initial conversion X ₀ ). The remainder of the latex was aged and the conversion (%) was measured again at various time intervals (X _t ).

The increase in the conversion rate (%) was calculated as “conversion at aging time” − “initial conversion” (X _t −X ₀ ).

  Mooney viscosity is used as an important standard property of SBR in this industry. Mooney viscosity is not a measure of viscosity in the true sense of its scientific term, but a measure of shear torque averaged over a range of polymer shear rates. The Mooney viscosity of the sample depends on the average molecular weight (chain length) and polydispersity of the polymer chain. When SBR polymerization is performed, the degree of monomer conversion to polymer is an indicator of the Mooney viscosity of the resulting rubber. Even after the rubber is coagulated from the latex, the Mooney viscosity can change over time due to chain activity due to recombination of a few polymer chains. Based on this insight, conversion (%) was used as an indicator of rubber Mooney viscosity.

  Table 1 below shows experimental data of the SBR polymerization reaction that was terminated with the composition of the present invention.

  As shown in the above data, the polymerization terminator of the present invention comprising IPHA and at least one primary or secondary alkylhydroxylamine is an effective polymerization terminator. Compared to DEHA, mixtures containing IPHA and MHA or PHA are better in adjusting the conversion rate and thus in the Mooney viscosity drift as the sample ages.

Stability Study The various mixtures claimed can be analyzed for their thermal stability in the presence of metal shavings of stainless steel 316 (SS316) or carbon steel 1010 (CS1010) by a dynamic scanning calorimeter. , DSC). These metals are a typical environment that current product offerings (CHAINGUARD I-15) typically face and may contact the new IPHA-based mixtures described in this disclosure. Selected to be an environment that would be reasonably expected. Testing was performed on an aqueous solution of IPHA to mixed alkylhydroxylamine (eg, MHA, PHA, TBHA, DMHA, IPMHA, and DEHA) at 15.8: 3.2 wt% (5: 1 ratio). The results are summarized in Table 2 below.

  Obviously, the comparative IPHA / HA mixture decomposes at a much lower temperature than any of the IPHA-based mixtures as described in WO 02/38617, so that commercial IPHA products are encountered. Incompatible with typical construction materials. In light of this, it is clear that IPHA / HA mixtures are not suitable for long-term transport or storage in SS316 or CS1010.

A 1% active solution of total alkylhydroxylamine under partition ratio study evaluation was prepared. A constant weight was added to a test flask placed in a water bath. The flask was equipped with a vaporizer arm and was further connected to a cooler arm. A water bath was provided to heat the solution to 85-90 ° C. The assembly was maintained under a vacuum of 20.5 inches Hg. Special care was taken to prevent concentration in the upper region of the assembly. The system was equilibrated. When equilibrium was reached, the two-way cock on the top cooler was activated so that the concentrate could be collected. After collecting the desired amount, the vacuum was slowly released and the weight of the solution in the original and concentration flasks was recorded. In addition, the amount of active alkylhydroxylamine contained therein was determined as described in Table 3.

Popcorn Inhibition Research Popcorn polymers are highly cross-linked materials that can be formed in the monomer recovery area of processes containing dienes such as butadiene, which process produces SBR, NBR, BR, and polychloroprene. Including. Popcorn polymers are insoluble in organic solvents and can cause loss of maintenance outages. Popcorn inhibition studies were conducted in the laboratory using an active popcorn seed obtained from styrene-butadiene emulsion polymerization. This seed was exposed to uninhibited monomer under the conditions relevant in the industrial emulsion polymerization process. The inhibitory effect with alkylhydroxylamine was observed over several days and the number of days of protection conferred by each alkylhydroxylamine was recorded.

  In a laboratory popcorn polymer inhibition study conducted on several alkyl hydroxylamines, the following results shown in Table 4 were obtained.

Modeling the properties of the composition of the present invention (low IPHA mixed with at least two primary AHAs) Proper partitioning of the polymerization terminator into the organic phase is believed to be necessary to stabilize the organic phase. Using a smaller amount of IPHA in the polymerization termination mixture, along with larger amounts of other primary AHA having beneficial characteristics related to these desired properties, should produce a higher performance polymerization stopper. It is believed that. In order to evaluate these properties of such low IPHA containing mixtures, as described in the examples below, a computer model was used to determine the low IPHA containing mixtures containing at least two primary AHA in various relative amounts. The partition ratio and partition coefficient to the organic phase were predicted.

  The specific computer modeling software and inputs used are as follows:

Software name : Gaussian

Company / Manufacturer : Gaussian Inc.

Version : Gaussian 09

Application : Calculation of reactivity of AHA Electron energy, vibration frequency and rotation constant were calculated at theoretical CBS-QB3 level.
Rate constants were calculated using standard transition state theory.
The tunnel effect was calculated using the Skodje-Truhlar method.
The rate constant of H atom abstraction reaction was calculated using ethyl radical derived from AHA.

Software name :
Turbomole
COSMOtherm

Company / Manufacturer: COSMOlogic

version:
TURBOMOLE V5-5
COSMOtherm X11 C — 21 — 0111 — a, parameterization file: BP — TZVP — C21 — 0111. ctd

Application : Distribution ratio (DR) calculation and distribution coefficient calculation.
Turbomole was used for quantum chemistry calculations.
COSMOtherm was used to predict DR and partition coefficients using COSMO files created with Turbomole.
DR was calculated at 70 ^* C, 1 wt% AHA in water.

  In order to improve the accuracy of the DR calculation, COSMOtherm needs experimental vapor pressure data. The vapor pressure data given to COSMOtherm as input is shown below:

  Predicted ranking of AHA reactivity: EHA ≧ IPHA> TBHA

Solubility of various AHA at 25 ° C (measured experimentally)
EHA about 50%
IPHA about 20%
TBHA about 12%

  Ethylbenzene was used in place of the organic phase for modeling. The degree of partitioning in the organic phase (ethylbenzene), ie the partition coefficient, amount:

を予測することにより算出し、これは、水中のＡＨＡの全モル分率に対するエチルベンゼン中のＡＨＡの全モル分率の比である。Ｘ_{ＡＨＡ（ＥＢ）}／Ｘ_{ＡＨＡ（Ｈ２Ｏ）}が１以上であることが望ましい。

, Which is the ratio of the total mole fraction of AHA in ethylbenzene to the total mole fraction of AHA in water. It is desirable that X _{AHA (EB)} / X _{AHA (H 2 O)} is 1 or more.

  As shown in Table 5 below, the distribution ratio and the distribution coefficient were calculated and predicted by the software model.

  Modeling results are known to deviate from experimental findings. Due to this uncertainty, the prediction should be based on a comparison.

Claims (12)

  A method of terminating a free radical initiated emulsion polymerization reaction, wherein an emulsion comprising at least one monomer is added to N-isopropylhydroxylamine (IPHA) or a salt thereof, as well as the IPHA or a salt thereof and Adding a polymerization terminator comprising at least one alkylhydroxylamine compound selected from the group consisting of primary alkylhydroxylamine, secondary alkylhydroxylamine, and mixtures thereof.   The at least one alkylhydroxylamine is N-methylhydroxylamine (MHA), N-ethylhydroxylamine (EHA), N-propylhydroxylamine (PHA), N-tert-butylhydroxylamine (TBHA), and mixtures thereof The process of claim 1, wherein the process is a primary alkylhydroxylamine selected from the group consisting of   The method of claim 1, wherein the primary alkylhydroxylamine is TBHA.   The method of claim 1, wherein the IPHA or salt thereof and the at least one alkylhydroxylamine are present in the polymerization stopper in a molar ratio of IPHA: alkylhydroxylamine of 40: 1 to 1: 1.   4. The method of claim 3, wherein IPHA or a salt thereof and TBHA are present in the polymerization terminator in a molar ratio where IPHA: TBHA is 5: 1.   The at least one alkylhydroxylamine is N-methylhydroxylamine (MHA), N-ethylhydroxylamine (EHA), N-propylhydroxylamine (PHA), N-tert-butylhydroxylamine (TBHA), and mixtures thereof The method of claim 1, comprising at least two primary alkyl hydroxylamines selected from the group consisting of:   7. The method of claim 6, wherein the at least two primary alkyl hydroxylamines are N-ethylhydroxylamine (EHA) and N-tert-butylhydroxylamine (TBHA).   The IPHA or salt thereof and the at least two primary alkyl hydroxylamines are present in the polymerization stopper in a molar ratio of IPHA: (at least two alkyl hydroxylamines) of 0.02: 1 to 0.1: 1. The method of claim 1.   The method of claim 1, wherein the polymerization terminator comprises 30-90 wt% solvent based on the total weight of the polymerization terminator.   The method of claim 1, wherein the polymerization terminator is added to the emulsion in an amount of 0.01 to 0.1 parts per hundred parts of the monomer (phm). A method for producing an elastomer comprising:
1) performing a free radical polymerization of a latex containing a conjugated diene;
2) N-isopropylhydroxylamine (IPHA) or a salt thereof, and at least one alkyl selected from the group consisting of primary alkylhydroxylamine, secondary alkylhydroxylamine, and a mixture thereof, which is different from IPHA or a salt thereof. Adding a polymerization terminator comprising a hydroxylamine compound; and 3) processing the polymer to form the elastomer,
The above method.   The method of claim 11, wherein the elastomer is a rubber selected from the group consisting of styrene-butadiene rubber, butadiene rubber, and acrylonitrile-butadiene rubber.