A modified conjugated diene polymer and a method for preparing the same, a rubber composition

Abstract

Disclosed are a modified conjugated diene polymer, a method for preparing the same, and a rubber composition. The conjugated diene polymer has a modified group of a nitrogen atom-containing group and an alkoxysilane at a terminal end, and a nitrogen element content of 20-200 ppm in the polymer. The zero shear viscosity η0 and the weight average molecular weight Mw of the polymer measured using a rotational rheometer satisfy the following conditions: 1.2 lgMW ≤lgη0(395K)≤2.5 lgMW By controlling the relationship between the zero shear viscosity and the weight average molecular weight within a certain range, the present application can ensure that when the values are large, the viscosity can be inhibited from rising greatly in a mixing process, the processing performance is more excellent, the adhesion is reduced, and the drying performance is improved; and when the values are low, excessive molecular chain entanglement and friction resistance can be avoided, so that heat generation can be reduced, and wear can be reduced.

Description

Technical Field

[0001] This invention relates to the field of polymers, and more particularly to conjugated diene polymers and rubber compositions. Background Technology

[0002] With the popularization of new energy vehicles, the requirements for green tires, such as low fuel consumption, lightweight, and low rolling resistance, are constantly increasing. Therefore, it is necessary to improve the rubber materials used in automobile tires, especially the tire treads that come into contact with the road surface.

[0003] Rubber compositions used in tire treads typically contain a large amount of silica to improve the composition's strength, rolling resistance, and wet skid performance. Improving the affinity between rubber and silica, and enhancing the dispersibility of silica in the composition, are currently the focus of research.

[0004] CN119462990A discloses a conjugated diene polymer with specific Mooney viscosity, stress relaxation rate, and branching degree. By combining polymerization and branching processes, the problems of poor silica dispersibility and processability degradation are solved, and the excellent properties of sulfides are achieved.

[0005] CN114929765A discloses a modified conjugated diene polymer and a rubber composition comprising the thereof. The first polymer chain of the polymer includes a derivative unit from an aminoalkoxysilane modifier at at least one end, and the second polymer chain includes a derivative unit from an aminoepoxy modifier at at least one end. The aminoalkoxysilane modifier includes more than 6 alkoxy groups in the molecule, and the interaction between the polar groups and silica is enhanced, thereby improving the dispersibility of silica.

[0006] KR1020220051607A discloses a modified conjugated diene polymer with excellent filler affinity and its preparation method. This polymer is derived from repeating units of conjugated diene monomers; it is a modified conjugated diene polymer containing functional groups derived from modifiers represented by formulas 1 and 1a. A represents a substituent of formula 1a. Modification enhances its affinity and reactivity with fillers.

[0007]

[0008] All of the above-mentioned existing technologies involve modification and branching steps. Introducing polar groups enhances the interaction with silica, thereby strengthening the bond between the rubber and the powder, thus improving the overall performance of the vulcanized rubber. Branching or coupling broadens the molecular weight distribution, reduces the zero-shear viscosity and Mooney viscosity of the rubber, and prevents deterioration in flowability during processing such as mixing, extrusion, and calendering, thus improving processing performance. However, existing inventions do not clearly specify the degree or range of branching or coupling. In fact, excessive branching or uneven distribution of branching points may lead to an uneven vulcanization network, which can reduce tensile strength and elongation at break; it may also lead to excessive molecular chain entanglement and frictional resistance, resulting in stronger heat generation. Therefore, precise control of the degree and structure of branching is crucial. Summary of the Invention

[0009] This invention addresses the shortcomings of existing technologies by comparing the relationship between the zero-shear viscosity and weight-average molecular weight of conjugated diene polymers, which directly reflects the degree of polymer branching, thereby achieving further optimization of rubber products in terms of processing performance, frictional heat generation, rolling resistance, and wet skid resistance.

[0010] The technical solution of the present invention is as follows:

[0011] A modified conjugated diene polymer is a copolymer of a conjugated diene and a monovinyl aromatic monomer, said polymer satisfying the following requirements (a)-(d):

[0012] (a) The Mooney viscosity measured at 100°C is 45 to 150;

[0013] (b) The polymer ends with modified groups containing nitrogen atoms and alkoxysilanes, and the nitrogen content in the polymer is 20-200 ppm.

[0014] (c) Using tetrahydrofuran as the eluent, the weight-average molecular weight of the polymer determined by gel permeation chromatography was 40 × 10⁻⁶. 4 ~150×10 4 g / mol, molecular weight distribution PDI 1.7~4.5,

[0015] (d) The zero-shear viscosity η0 and weight-average molecular weight Mw of the polymer, measured using a rotational rheometer, satisfy the following conditions:

[0016] 1.2 lgMW ≤lgη0(395K)≤2.5 lgMW .

[0017] The conjugated diene polymer has a 1,2-vinyl content of 20-70% (molar ratio), preferably 25-55%; and a content of 10-50% (mass ratio) of the aromatic vinyl compound structural unit, i.e., bound styrene, preferably 10-30%. The vinyl content and bound styrene content are obtained according to the standard method in GB / T40722.2-2021, specifically using the ATR total reflectance infrared spectroscopy method. The bound styrene content is a mass fraction relative to the entire polymer; the 1,2-vinyl content is a molar fraction relative to the butadiene portion.

[0018] A method for preparing a modified conjugated diene polymer includes the following steps:

[0019] (1) Polymerization: Under an inert gas atmosphere, solvent, conjugated diene and monovinyl aromatic monomer and structure modifier are added to the reactor and mixed evenly. At the initiation temperature, an organolithium initiator is added to initiate polymerization.

[0020] (2) Branching: When the monomer conversion rate reaches more than 75% in the polymerization, a branching agent is added to react and branched conjugated diene polymers are obtained.

[0021] (3) End capping: The branched conjugated diene polymer is reacted with an end capping agent to obtain the modified conjugated diene polymer;

[0022] (4) Desolventization.

[0023] In step (1) of the present invention, the inert gas is nitrogen and / or argon, preferably argon.

[0024] In step (1) of the present invention, the solvent is selected from one or more of butane, cyclohexane, n-hexane, isoalkanes, heptane, octane, toluene, pentane, etc., preferably n-hexane.

[0025] In step (1) of the present invention, the mass of the solvent is 200-1500% of the total mass of the monomers, preferably 400-1000%.

[0026] The conjugated diene monomers of the present invention include one or more of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-heptadiene, preferably 1,3-butadiene.

[0027] In step (1) of the present invention, the conjugated diene is 50-90% of the total mass of the monomers, preferably 70-90%, calculated based on a total monomer content of 100%.

[0028] In step (1) of the present invention, the monovinyl aromatic monomer includes one or more of styrene, p-methylstyrene, α-methylstyrene, vinyl ethylbenzene, vinyl xylene, vinyl naphthalene, diphenylethylene, etc., preferably styrene.

[0029] In step (1) of the present invention, the monovinyl aromatic monomer is 10-50% of the total mass of the monomer, preferably 10-30%, based on a total monomer content of 100%.

[0030] In step (1) of this invention, the structure modifier can adjust the distribution of vinyl structures and the amount of aromatic blocks, including ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, and 2,2-bis(2-tetrahydrofuranyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinyl ethane, and triethylamine; and one or more alkali metal alkoxide compounds such as potassium tert-pentoxide and potassium tert-butoxide.

[0031] In step (1) of the present invention, the molar ratio of the structure modifier to the organolithium initiator is 1~10:1, preferably 3~8:1.

[0032] The organolithium initiator of the present invention is an amino organolithium, including one or more of lithium dimethylamino, lithium diethylamino, lithium dipropylamino, lithium dibutylamino, lithium diheptylamino, lithium diisopropylamino, lithium dioctylamino, lithium didecylamino, lithium 3-bistrimethylsilylaminopropyl, lithium hexamethyleneimino, lithium pyrrolidine, lithium piperidine, lithium heptamethyleneimino, lithium morpholine, etc., preferably lithium piperidine.

[0033] In step (1) of the present invention, the amount of organolithium initiator needs to be determined according to the molecular weight of the conjugated diene polymer. The amount of organolithium initiator added is 0.2~20 mmol / 100g monomer (monovinyl aromatic hydrocarbon and conjugated diene), preferably 0.5~3 mmol / 100g.

[0034] In step (1) of the present invention, the initiation temperature is 10~100℃, preferably 20~50℃.

[0035] In step (2) of this invention, the branching agent is preferably a vinyl monomer containing an alkoxysilyl group, with a branching point of 2 or more, preferably 3 or more, and more preferably 4 or more. The branching agent is selected from the monomers represented by the following formula 2, where R1 is an alkyl group with 1 to 20 carbon atoms or an aryl group with 6 to 20 carbon atoms, R2 is an alkyl group with 1 to 20 carbon atoms or an aryl group with 6 to 20 carbon atoms or an alkoxy group with 1 to 5 carbon atoms, and R3 is an alkyl group with 1 to 10 carbon atoms or a halogen atom. The molar ratio of the branching agent to the initiator is (0.05-2.0):1, preferably (0.5-1.5):1.

[0036] (Equation 2)

[0037] In step (2) of the present invention, the branching reaction temperature is 50~100℃, preferably 60~80℃; the reaction time is 10~80min, preferably 20~40min.

[0038] In step (3) of this invention, the capping agent includes one or more of the following: a carbonyl compound containing a nitrogen atom group, such as 1,3-dimethyl-2-imidazolinone, 1-methyl-3-(2-methoxyethyl)-2-imidazolinone, N-methyl-2-pyrrolidone, N-methyl-2-piperidinone, 4,4'-bis(dimethylamino)benzophenone, methyl-2-pyridyl ketone, methyl-4-pyridyl ketone, propyl-2-pyridyl ketone, di-4-pyridyl ketone, methyl 2-benzoylpyridine N,N-diethylcarbamate, N,N-diethylacetamide, N,N-dimethyl-N',N'-dimethylaminoacetamide, and N,N-dimethylpyridinecarboxamide; or one or more of the following: a nitrogen atom group: an isocyanate compound containing a nitrogen atom group, such as diphenylmethane diisocyanate, phenyl isocyanate, butyl isocyanate, and 1,3,5-phenyltriisocyanate.

[0039] In step (3) of the present invention, the molar ratio of the capping agent to the initiator is (0.05-2.5):1, preferably (0.5-1.0):1.

[0040] In step (3) of the present invention, the end-capping reaction temperature is 50~150℃, preferably 65~90℃; the reaction time is 10~120min, preferably 20~50min.

[0041] In step (4) of the present invention, the solvent removal step includes one or more of the following methods: separating the solvent by stripping, filtering out the polymer, further drying in an oven, and then dehydrating it by passing it through a rolling mill; flash concentration followed by de-volatilization using a de-venting extruder; direct de-volatilization using a rotary dryer, etc.; preferably, the method of stripping followed by drying in an oven and a rolling mill.

[0042] A rubber composition comprising, by weight and 100 parts by weight, more than 80 parts by weight of the modified conjugated diene polymer of the present invention, and one or more selected from natural rubber, butadiene rubber, emulsion polymerized styrene-butadiene rubber, and isoprene rubber.

[0043] As a preferred embodiment, the rubber composition further includes a filler selected from silica and / or carbon black, wherein the filler is used in an amount of 10-200 parts by weight, preferably 50-180 parts by weight.

[0044] The beneficial effects of this invention are as follows:

[0045] (1) Control the type and amount of branching agent to control the polymer's zero-shear viscosity and weight-average molecular weight within 1.2. lgMW ≤lgη0(395K)≤2.5 lgMW Within the range, a higher value indicates a higher degree of branching, which tends to result in a significant reduction in viscosity in the high shear domain and easy mixing (good processability); a lower value can effectively avoid the chain entanglement and uneven vulcanization problems caused by excessive branching, thereby reducing heat generation and improving mechanical properties.

[0046] (2) Introducing nitrogen-containing atomic groups to modify the polymer improves the bonding force between the polymer and silica and improves the dispersibility of silica in the rubber composition, thereby ensuring the comprehensive properties of vulcanized rubber such as low rolling resistance and anti-slip properties. Detailed Implementation

[0047] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0048] Test method:

[0049] Zero-shear viscosity: Cut the raw rubber into 25mm diameter discs, fix them with 25mm parallel plate clamps, and use a rotational viscometer to perform a frequency scan of 0.01~100rad / s at 160℃ under nitrogen protection with a fixed strain of 5%.

[0050] Mooney viscosity: tested using GB / T1232.1 method. In this invention, Mooney viscosity (MV; ML(1+4) 100℃) is measured using MV2000 (high-speed rail testing instrument).

[0051] Molecular weight and molecular weight distribution: Gel permeation chromatography (GPC) was used with THF as the mobile phase. The GPC setup consisted of two KF-805 columns and one KF-G guard column (Showa Denko, Japan). Polystyrene was used as a standard to calculate the molecular weight. The conditions used were: sample concentration 1‰ (diluted with THF), flow rate 1 mL / min, injection volume 100 μL, and column temperature 40 °C.

[0052] The tanδ value of the compound was tested using a dynamic viscoelastic spectrometer (NETZSCH instrument, DMA-303), at a frequency of 10 Hz, a heating rate of 5 K / min, and a temperature range of -80 to 80 °C.

[0053] Physical and mechanical properties: tested according to GB / T8656-1998 method.

[0054] Example 1

[0055] In a 2L stainless steel polymerization reactor, under a nitrogen atmosphere, 15g of styrene, 85g of 1,3-butadiene, 900g of n-hexane, and 2.57mmol of ethylene glycol dibutyl ether were added sequentially. After heating the system to 50℃, 3.43ml of lithium piperidinium (0.15mol / L cyclohexane solution) was added using a syringe to initiate the copolymerization reaction. After 75 minutes of polymerization, the monomer conversion rate reached over 99%. Then, 0.77mmol of a three-branching agent (Shanghai Mairui Biotechnology Co., Ltd.) was added to the reactor. The reaction ended after 15 minutes. Then, 1.03mmol of a capping agent, 1,3-dimethyl-2-imidazolinone, was added to the system. After another 15 minutes, the reaction was stopped, the gel was removed, and the polymer sample, named A-1, was obtained after stripping and drying. The basic and performance data of the copolymer are shown in Table 1.

[0056] Formula 3

[0057] Comparative Example 1

[0058] Without using a branching agent, the polymer was prepared according to Example 1 and named B-1.

[0059] Example 2

[0060] In a 2L stainless steel polymerization reactor, 20g of styrene, 113g of 1,3-butadiene, 1197g of cyclohexane, and 4.45mmol of tetrahydrofuran were added sequentially under a nitrogen atmosphere. After heating the system to 40℃, 3.71ml of lithium hexamethyleneimine (a 0.15mol / L cyclohexane solution) was added using a syringe to initiate the copolymerization reaction. After 65 minutes, the monomer conversion rate reached over 99%. 0.83mmol of a type 4 branching agent (Shanghai Mairui Biotechnology Co., Ltd.) was added to the reactor. The reaction ended after 20 minutes. Then, 0.57mmol of a 4,4'-bis(dimethylamino)benzophenone end-capping agent was added to the system. The reaction was stopped after 15 minutes. The polymer solution was removed, stripped, and dried to obtain the polymer sample, named A-2. The basic and performance data of the copolymer are shown in Table 1.

[0061] Formula 4

[0062] Comparative Example 2

[0063] The polymer was prepared according to Example 2 and named B-2, except that an excess of the branching agent shown in Formula 4 was added, with a content of 2.66 mmol in the system.

[0064] Example 3

[0065] In a 2L stainless steel polymerization reactor, 18g of styrene, 102g of 1,3-butadiene, 1213g of toluene, and 4.45mmol of tetramethylethylenediamine were added sequentially under a nitrogen atmosphere. After heating the system to 30℃, 4.66ml of lithium morpholine (0.15mol / L cyclohexane solution) was added using a syringe to initiate the copolymerization reaction. After 70 minutes, the monomer conversion rate reached over 99%. 1.25mmol of a tri-branching agent was then added to the reactor, and the reaction ended after 15 minutes. Finally, 1.05mmol of a capping agent, di-4-pyridyl ketone, was added, and the reaction was stopped after 20 minutes. The resulting polymer solution was removed, stripped, and dried to obtain a polymer sample named A-3. The basic and performance data of the copolymer are shown in Table 1.

[0066] Comparative Example 3

[0067] The polymer was prepared according to Example 3 and named B-3, except that the amount of branching agent used was insufficient, with a content of 0.07 mmol in the system.

[0068] Example 4

[0069] In a 2L stainless steel polymerization reactor, 15g of styrene, 85g of 1,3-butadiene, 1150g of n-hexane, and 2.96mmol of tetrahydrofuran were added sequentially under a nitrogen atmosphere. After heating the system to 30℃, 3.93ml of lithium piperidinium (0.15mol / L cyclohexane solution) was added using a syringe to initiate the copolymerization reaction. After 90 minutes of polymerization, the monomer conversion rate reached over 99%. 0.65mmol of a tetrabranching agent was then added to the reactor, and the reaction ended after 15 minutes. Finally, 0.50mmol of a capping agent, di-4-pyridyl ketone, was added to the system, and the reaction was stopped after 20 minutes. The resulting polymer solution was removed, stripped, and dried to obtain a polymer sample named A-4. The basic and performance data of the copolymer are shown in Table 1.

[0070] Comparative Example 4

[0071] The polymer was prepared according to Example 4 and named B-4, the only difference being that the branching agent was different, which was vinyltrimethoxysilane, and the amount added to the system was 0.65 mmol.

[0072] Application examples

[0073] Modified conjugated diene polymer: 80 phr, natural rubber: 20 phr, sulfur: 1.5 phr, antioxidant (antioxidant 4020, i.e., N-(1,3-dimethylbutyl)-N'-phenylhydroquinone): 1 phr, stearic acid: 2 phr, vulcanization accelerator (tetramethylthiuram disulfide): 1 phr, silica: 50 phr, aromatic oil (TDAE, environmentally friendly aromatic oil): 5 phr. The polymer samples obtained in Examples 1-4 and Comparative Examples 1-4 were vulcanized to prepare their respective corresponding vulcanized rubbers. The vulcanization conditions were: roller temperature 50°C; vulcanization temperature 145°C; pressure maintained at 10-15 MPa; vulcanization time 35 min. Elastomer product test data are shown in Table 1.

[0074] Table 1. Test Data for Elastomer Products

[0075] Testing items A-1 A-2 A-3 A-4 B-1 B-2 B-3 B-4 Molecular weight Mw (×10⁴) 112 75 82.5 80 115 73 85.5 80 PDI 2.8 2.5 3.0 2.5 2.8 2.6 3.0 2.6 Mooney viscosity of raw rubber ML(1+4) at 100℃ 88 62 72 71 85 60 75 72 Styrene content / % 15.6 15.5 15.2 15.9 15.5 15.8 15.3 15.5 Zero-shear viscosity η0 (395K) 3.8×104 1.0×103 5.9×103 5.5×103 1.73 5×107 4.46 2.99 Tanδ (60℃) 0.071 0.078 0.077 0.079 0.096 0.098 0.103 0.113 Tanδ (0℃) 1.049 1.058 1.055 1.023 1.019 1.022 Tensile strength (MPa) 17.5 18.0 17.9 18.2 15.6 17.6 15.5 14.8 Mooney viscosity of compounded rubber ML(1+4) at 100℃ 119 105 110 115 150 102 123 140 DIN wear (cm3) 0.043 0.045 0.050 0.049 0.052 0.072 0.061 0.054

[0076] Note 1: Mw (ten thousand) is the weight-average molecular weight; PDI is the ratio of Mw to Mn, representing the polymer dispersion; Mooney viscosity test conditions are ML(1+4) at 100℃; Tanδ (60℃) is the loss factor at 60℃, the smaller the value, the lower the rolling resistance; Tanδ (0℃) is the loss factor at 0℃, the larger the value, the stronger the anti-slip ability.

[0077] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A modified conjugated diene polymer, which is a copolymer of a conjugated diene and a monovinyl aromatic monomer, said polymer satisfying the following requirements (a)-(d): (a) The Mooney viscosity measured at 100°C is 45 to 150; (b) The polymer ends with modified groups containing nitrogen atoms and alkoxysilanes, and the nitrogen content in the polymer is 20-200 ppm. (c) Using tetrahydrofuran as the eluent, the weight-average molecular weight of the polymer determined by gel permeation chromatography was 40 × 10⁻⁶. 4 ~150×10 4 g / mol, molecular weight distribution PDI 1.7~4.5, (d) The zero-shear viscosity η0 and weight-average molecular weight Mw of the polymer, measured using a rotational rheometer, satisfy the following conditions: 1.2 lgMW ≤lgη0(395K)≤2.5 lgMW 。 2. The modified conjugated diene polymer according to claim 1, characterized in that, The conjugated diene polymer has a 1,2 vinyl content of 20-70% mol, preferably 25-55% mol; and the content of the aromatic vinyl compound structural unit, i.e., the styrene, is 10-50% wt, preferably 10-30% wt.

3. A method for preparing the modified conjugated diene polymer according to claim 1 or 2, comprising the following steps: (1) Polymerization: Under an inert gas atmosphere, solvent, conjugated diene and monovinyl aromatic monomer and structure modifier are added to the reactor and mixed evenly. At the initiation temperature, an organolithium initiator is added to initiate polymerization. (2) Branching: When the monomer conversion rate reaches more than 75% in the polymerization, a branching agent is added to react and branched conjugated diene polymers are obtained. (3) End capping: The branched conjugated diene polymer is reacted with an end capping agent to obtain the modified conjugated diene polymer; (4) Desolventization.

4. The method according to claim 3, characterized in that, The conjugated diene includes one or more of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-heptadiene.

5. The method according to claim 3, characterized in that, The monovinyl aromatic monomers include one or more of styrene, p-methylstyrene, α-methylstyrene, vinyl ethylbenzene, vinyl xylene, vinyl naphthalene, and diphenylethylene.

6. The method according to claim 3, characterized in that, Based on a total monomer mass of 100%, the conjugated diene is 50-90% of the total monomer mass, preferably 70-90%.

7. The method according to claim 3, characterized in that, The branching agent is selected from the monomers of the compound represented by Formula 2 below, where R1 is an alkyl group with 1 to 20 carbon atoms or an aryl group with 6 to 20 carbon atoms, R2 is an alkyl group with 1 to 20 carbon atoms or an aryl group with 6 to 20 carbon atoms or an alkoxy group with 1 to 5 carbon atoms, and R3 is an alkyl group with 1 to 10 carbon atoms or a halogen atom. Equation 2.

8. The method according to claim 7, characterized in that, The molar ratio of branching agent to initiator is (0.05-2.0):1, preferably (0.5-1.5):

1.

9. The method according to claim 3, characterized in that, The end-capping agent includes one or more of the following: 1,3-dimethyl-2-imidazolinone, 1-methyl-3-(2-methoxyethyl)-2-imidazolinone, N-methyl-2-pyrrolidone, N-methyl-2-piperidinone, 4,4'-bis(dimethylamino)benzophenone, methyl-2-pyridyl ketone, methyl-4-pyridyl ketone, propyl-2-pyridyl ketone, di-4-pyridyl ketone, methyl 2-benzoylpyridine N,N-diethylcarbamate, N,N-diethylacetamide, N,N-dimethyl-N',N'-dimethylaminoacetamide, N,N-dimethylpyridinecarboxamide, diphenylmethane diisocyanate, phenyl isocyanate, butyl isocyanate, and 1,3,5-phenyltriisocyanate.

10. A rubber composition comprising, by weight and 100 parts by weight, 80-90 parts by weight of a modified conjugated diene polymer or a modified conjugated diene polymer prepared by the method of any one of claims 3-9, and one or more selected from natural rubber, cis-butadiene rubber, emulsion-polymerized styrene-butadiene rubber, and isoprene rubber.

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