JPS61271338A - Styrene/butadiene random copolymer composition - Google Patents

Abstract

PURPOSE:To provide rubber for tire, which has well-balanced properties between resilience and wet skid resistance, consisting of a straight-chain component and a branched component so as to allow the styrene units in the copolymer chain to be formed by a specified styrene chain distribution. CONSTITUTION:A styrene/butadiene random copolymer is composed of 25-75wt% straight-chain component (A) and 75-25wt% branched component. Component A is a reaction product of a lithium-terminated copolymer (a) with a urea derivative of the formula, obtd. by copolymerizing styrene and butadiene in the presence of an organolithium compd. in a hydrocarbon solvent. Component B is a reaction product of said copolymer (a) with a polyfunctional coupling agent contg. at least three reactive moieties. The random copolymer has a Mooney viscosity (ML1+4, 100 deg.C) of 30-150 and a bonded styrene content of 5-45wt% wherein the styrene unit composed of a single styrene chain is at least 40wt% of the bonded styrene and styrene unit composed of a long chain of at least 8 styrene units is not more than 5wt% of the bonded styrene.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a linear component modified with a specific urea derivative and a branched component modified with a polyfunctional coupling agent having at least three reactive sites. The present invention relates to a random styrene-butadiene copolymer composition consisting of components having a specific styrene chain distribution in which the styrene units in the copolymer chain have a specific styrene chain distribution.

[Prior Art] Random styrene-butadiene copolymers from fffi have been widely used as tire rubber.

In recent years, with the demand for lower fuel consumption and improved driving safety for automobiles, tires with excellent fuel efficiency and handling stability have become required. High rebound resilience is required to improve fuel efficiency, and high wet skid resistance is required to improve handling stability.

Furthermore, workability such as roll workability and extrusion workability, which are important in tire manufacturing, is required.

However, the relationship between impact resilience and wet skid resistance is contradictory, and various methods have been proposed to balance these contradictory properties and improve processability. Method of setting rubber (JP-A-57-128807), method of blending high-molecular-weight rubber and low-molecular-weight rubber having a specific glass transition temperature (JP-A-57-18HAE1), tin and coupling excluding tin A method of introducing a specific amount of a branched component bound by an agent (Japanese Patent Application Laid-Open No. 59-45338)
, a method for highly uniformizing the styrene units in a copolymer chain with bimodal molecular weight distribution (Patent Application No. 1987-159)
No. 123) etc. In addition, as a method to improve only processability, a method of setting a branched polymer (Japanese Patent Publication No. 44-499
No. 8, Special Publication No. 1973-38957, Special Publication No. 1977-52E
iEia issue).

[Problems to be Solved by the Invention] However, although these methods show some improvement effects, they have not yet been able to highly satisfy these contradictory characteristics and sufficiently improve workability.

The present invention was made in view of the above points, and an object of the present invention is to provide a random styrene-butadiene copolymer composition that has a significantly improved balance between impact resilience and wet skid resistance, and has improved processability. .

[Means and effects for solving the problems] The present invention has been made based on intensive studies on the chain distribution of styrene units in a styrene-butadiene copolymer chain in which a functional group is bonded. Consisting of a linear component modified with a urea derivative and a branched component modified with a polyfunctional coupling agent having at least three reactive sites, the styrene units in the copolymer chain are linked to specific styrene chains. This was based on the discovery that a random styrene-butadiene copolymer composition having a distribution has an extremely excellent balance between impact resilience and wet skid resistance, and has excellent processability.

That is, the present invention relates to a lithium-terminated copolymer obtained by copolymerizing styrene and butadiene in a hydrocarbon solvent using an organolithium compound as a polymerization initiator, and a lithium-terminated copolymer obtained by copolymerizing styrene and butadiene in a hydrocarbon solvent, - C4 alkyl group or alkoxyalkyl group, Y is an oxygen atom or a sulfur atom, . is an integer of 2 to 4) A linear component formed by reacting a urea derivative represented by Mooney viscosity (ML+ -a, 1
00°C) is 30 to 150, the styrene-butadiene copolymer contains 5 to 45% by weight of bound styrene, and the single styrene chain having one styrene unit is 40% by weight of bound styrene.
% by weight or more, long styrene chains consisting of 8 or more styrene units are 5% by weight or less of the bound styrene, linear components account for 25-75% by weight of the copolymer, and branched components account for the remaining 75-25% by weight. % by weight of a random styrene-butadiene copolymer composition.

The random styrene-butadiene copolymer composition of the present invention exhibits excellent vulcanizate properties and processability, and is used for various rubber applications, and is useful for tire applications such as treads and sidewalls.

The present invention will be explained in detail below.

The linear component of the random styrene-butadiene copolymer composition of the present invention has a lithium-terminated copolymer and a general formula (wherein R1 and R2 each independently represent an alkyl group of 01 to C4, or an alkoxyalkyl group, Y represents an oxygen atom or a sulfur atom, and n represents an integer from 2 to 4. If the composition consists of a reaction between a polymer and a urea derivative having an acyclic structure, or a substance such as water, alcohol, or acid, the impact resilience of the composition will be poor.

In addition, 25 to 75 parts by weight in the copolymer composition are linear components modified with a specific urea derivative, and the remaining 75 to 2 parts by weight are linear components modified with a specific urea derivative.
5% by weight is a branched component modified with a polyfunctional coupling agent having at least three reactive sites. If the linear component is less than 25% by weight, or if the branched component is more than 75% by weight, the impact resilience will drop, and if the linear component is more than 75% by weight, or if the branched component is 25% by weight. If it is less than this, the processability will deteriorate, which is not preferable.

The bound styrene content of the copolymers of the present invention is from 5 to 45% by weight, preferably from 10 to 40% by weight. If the bound styrene content is less than 5% by weight, the wet skid resistance will deteriorate, which is undesirable. On the other hand, if the bound styrene content exceeds 45% by weight, impact resilience and abrasion resistance decrease, which is not preferable.

In the copolymer of the present invention, the styrene single chain having one styrene unit (hereinafter referred to as S1) accounts for 40% by weight or more, preferably 55% by weight or more of the combined styrene, and the styrene long chain having 8 or more styrene units (hereinafter referred to as S1) contains 40% by weight or more, preferably 55% by weight or more of the combined styrene. (hereinafter referred to as S8~) is 5.0% by weight or less, preferably 2.5% by weight of the bound styrene.
Even if Sl is less than 40% by weight of the bound styrene, or if it exceeds 5% by weight, impact resilience, abrasion resistance, and wet skid resistance are unfavorable.

Mooney viscosity CMLr, a of the copolymer of the present invention.

100℃) is 30-150. Preferably tt 50-1
20 Thea)ru. If the Mooney viscosity is less than 30, the blowing effect of impact resilience and abrasion resistance will not be sufficient, and if the Mooney viscosity exceeds 150, problems will remain in the calendering processability and extrusion processability of the compound.

The physical properties of the copolymer of the present invention change significantly by changing the microstructure of the butadiene moiety.

The physical properties also change depending on the styrene composition distribution in the copolymer chain.

Regarding the relationship between the microstructure of the butadiene moiety and physical properties, the relationship between the 1.2 vinyl content and the physical properties is known. For example, as the 1,2 vinyl content increases, the wet skid resistance of the polymer improves; Abrasion resistance decreases (Rubb
er Age, VoR104, 55 (1972))
.

In addition, as the 1,2-vinyl content increases, heat resistance and reversion are improved. H. Nordsiek (P
aper Presented to the Int.
, Rubber C0nt.

(1979).

The relationship between the 1,2 vinyl content and physical properties is already known, and in the present invention, the 1.2 vinyl content is not particularly limited, but from the viewpoint of impact resilience and abrasion resistance, the 1.2 vinyl content is 10 On the other hand, from the viewpoint of wet skid resistance, the 1.2 vinyl content is preferably 30 to 90%. In any case, the 1.2 vinyl content should be determined depending on the purpose of use.

Furthermore, regarding the distribution of 1 and 2 vinyl in the polymer chain, even if it is uniform in one polymer chain,
As shown in No. 75, it may change gradually along the polymer chain, or it may be distributed in blocks (USP-3301840), and it is best to decide on the purpose of use. .

Regarding the styrene composition distribution in the styrene-butadiene copolymer chain, it may be uniformly distributed in the copolymer chain, or it may be unevenly distributed in the copolymer chain (Japanese Patent Application No.
4108), and should be determined depending on the purpose of use.

The copolymer of the present invention has a well-known relationship between the molecular weight distribution and the processability, in which the processability changes significantly by changing the molecular weight distribution. The molecular weight distribution (Few/PaN) expressed as the ratio to (MN) is not particularly limited, but considering the balance between physical properties and processability, it is 1.2 ~
3.5 is preferable, and the ratio of the weight average molecular weight (Mw') to the number average molecular weight CFIN' of the linear component and the branched component of the copolymer of the present invention (Mw'/M) is preferably 3.5.
N') is not particularly limited, but
A value of 1.1 to 2.5 is sufficient.

The copolymer of the present invention is produced by the method described below. One method is to copolymerize styrene and 1,3-butadiene in a hydrocarbon solvent using an organolithium compound as an initiator, as described in British Patent No. 88472B and Japanese Patent Application Laid-open No. 59-140.
As described in No. 211 and JP-A-58-143208, etc., the styrene monomer content in the 7-mer composition ratio of styrene and 1,3-butadiene in the polymerization system is 1.3 so that it falls within a specific concentration range. -butadiene or 1.
A lithium-terminated copolymer obtained by carrying out copolymerization by continuously or intermittently supplying a mixture of 3-butadiene and styrene, and a lithium-terminated copolymer obtained by the general formula (wherein R1 and R2 each independently represent 01 to C4). a urea derivative represented by an alkyl group or an alkoxyalkyl group, Y represents an oxygen atom or a sulfur atom, and n represents an integer of 2 to 4) and a polyfunctional coupling agent having at least 3 reactive sites. It is obtained by adding at a predetermined ratio.

Another method is to copolymerize styrene and 1,3-butadiene in a hydrocarbon solvent using an organolithium compound as an initiator, and styrene is copolymerized at a rate slower than the copolymerization rate, as described in Japanese Patent Publication No. 38-2394. Copolymerization is carried out by adding a mixture of an alkyl group, Y represents an oxygen atom or a sulfur atom, . represents an integer from 2 to 4) and a polyfunctional coupling agent having at least 3 reactive sites in a predetermined ratio ↑ Obtained by adding

When the urea derivative and polyfunctional coupling agent used in the present invention come into contact with the thiium-terminated copolymer, they react almost instantaneously and quantitatively. Therefore, in order to obtain the copolymer of the present invention, the amounts of the urea derivative and the polyfunctional coupling agent to be added are 0.00000000000000000000000000000000000000000000000000,000. 25-0.75
．． After a small amount of copolymerization, the urea derivative and the polyfunctional coupling agent are added to the polymerization system simultaneously or separately. Alternatively, after the copolymerization is completed, 1,3-butadiene may be added, and then the urea derivative and the polyfunctional coupling agent may be added. Alternatively, a polyfunctional coupling agent may be added during the copolymerization, and the urea derivative may be added after the copolymerization is completed.

The copolymer composition of the present invention also comprises a linear component obtained by reacting a lithium-terminated copolymer with a specific urea derivative, a lithium-terminated copolymer, and a polyfunctional component having at least three reactive sites. The branched components obtained by reacting the reactive coupling agent are prepared separately, and the copolymers are mixed so that the linear component accounts for 25 to 75% by weight and the branched component accounts for 75 to 25% by weight. It can also be obtained by mixing in a blend ratio.

In the copolymer composition of the present invention, the balance between physical properties and processability is changed by changing the intrinsic viscosity ratio between the branched component and the linear component in the copolymer. The relationship between the intrinsic viscosity and processability of these branched components and linear components is already known (Japanese Patent Publication No. 59-52884).1 In the present invention, the above-mentioned intrinsic viscosity ratio is not particularly limited, but Considering the balance of physical properties, 1.5 to 5.5 is preferable.

In the present invention, in order to adjust the microstructure of the butadiene moiety in the copolymer chain or the randomness in the copolymer chain of styrene and butadiene, alkali metal alkoxides such as ethers and tertiary amines are used. For example, diethyl ether, ethylene glycol dimethyl ether, ethylene glycol dimethyl ether, etc.
Di-n-butyl ether, ethylene glycol/n-butyl-tert-butyl ether, ethylene glycol di-tert-butyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetrahydrofuran, α-methoxymethyltetrahydrofuran, dioxane, 1,2-dimethoxy Benzene, triethylamine, N, N, N', N'
-tetramethylethylenediamine, potassium-tart
-amyl oxide, potassium-tart-butyl thin oxide, etc. These compounds may be used alone or as a mixture of two or more.

The amount of the polar compound used in the present invention is 0 to 200 mol per mol of the organic lithium compound.

The organolithium compound used in the present invention is; n-
Monoorganolithium compounds such as propyllithium, isopropyllithium, n-butyllithium, 5ec-butyllithium, tert-butyllithium, dilithiomethane, 1,4-dilithiobutane.

1.4-dilithio-2-ethylcyclohexane, 1.2
-dilithio-1,2-diphenylmethane, 1,3.5
-) Polyfunctional organolithium compounds such as lithiobenzene. These may be used alone or in a mixture of two or more. Furthermore, as the polyfunctional organolithium compound used in the present invention, compounds that can be substantially converted into a polyfunctional organolithium compound by reacting the above-mentioned monoorganolithium compound with another compound are also used. For example, a reaction product of a monoorganolithium compound and a polyvinyl aromatic compound [Japanese Patent Publication No. 55-8852], a reaction product of a monoorganolithium compound and a conjugated diene, and/or a monovinyl aromatic compound, and then a polyvinyl aromatic compound or a reaction product obtained by simultaneously reacting a monoorganolithium compound, a conjugated diene, and/or a monovinyl aromatic compound, and the king of polyvinyl compounds (West German Patent No. 2003384, etc.).

The amount of these organic lithium compounds used is usually 0.1 to 10 mmol per 100 g of conjugated diene monomer.

As hydrocarbon solvents used in the present invention, aliphatic, cycloaliphatic and aromatic hydrocarbons can be used. For example, hydrocarbon solvents include propane, isobutane, n
-Hexane, isooctane.

Examples include cyclopentane, cyclohexane, benzene, toluene, etc., and particularly preferred solvents are n-hexane, cyclohexane, and benzene. These may be used alone or as a mixture of two or more.

The urea derivative used in the present invention has the general formula (wherein R1 and R2 each independently represent an alkyl group of 01 to C4 or an alkoxyalkyl group, Y represents an oxygen atom or a sulfur atom, and n represents 2 to 4 (represents an integer of ) Compounds represented by
-imidazolidinone, 1,3-dipropyl-2-imidazolidinone, l-methyl-3-ethyl-2-imidazolidinone, 1-methyl-3-propyl-2-imidazolidinone, l-methyl-3 -Butyl-2-imidazolidinone, l-methyl-3-(2-methoxyethyl)-2-imidazolidinone, 1-methyl-3-(2-ethoxyethyl)-2-imidazolidinone, 1.3 -di(2-nitoxyethyl)-2-imidazolidinone, 1,3-dimethylethylenethiourea, 1,3-dimethyl-3,4,5,
Examples include 8-tetrahydro-2(IH)-pyrimidinone, and 1,3-dimethyl-2-imidazolidinone is preferred.

The reaction temperature and reaction time between these urea derivatives and the lithium-terminated copolymer can be adjusted over a wide range, but usually the reaction temperature is in the range of 15 to 115°C and the reaction time is in the range of 1 second to 3 hours.

The polyfunctional coupling agent used in the present invention includes:
Epoxidized soybean oil, epoxidized linseed oil, epoxidized liquid polybutadiene, dimethyl terephthalate, diethyl terephthalate, dimethyl phthalate, dimethyl inphthalate, diethyl adipate 1 terephthalic acid dichloride, phthalic acid dichloride, inphthalic dichloride, adipic acid dichloride , silicon tetrachloride, methyltrichlorosilane, hexachlorosilane, tetramethoxysilane,
Carbon tetrachloride, stannic chloride, methyltrichlorotin, stannic bromide, dodecyltrichlorotin,
methyl-1-aziridinyl) triphosphatriazine,
Examples include pyromellitic dianhydride and polyaryl polyisocyanate. Among these, silicon tetrachloride, phthalic acid dichloride, and stannic chloride are preferred. When a copolymer with a branched component coupled with stannic chloride is kneaded with carbon black and process oil, its vulcanizate exhibits excellent impact resilience; Copolymers with branched components exhibit good processability, especially good extrusion properties. Therefore, when trying to obtain copolymers with better processability, silicon tetrachloride is used as a coupling agent. It is preferable to use it as

The polymerization method in the present invention may be either a batch polymerization method or a continuous polymerization method. The polymerization temperature ranges from 20 to 130°C, and in the batch polymerization method, polymerization starts at 30 to 87°C, and the maximum temperature is It is recommended to operate at elevated temperatures to reach 80-125°C.

After completion of the specified reaction, 2,6-tert-butyl-p-
After adding an antioxidant such as cresol, the resulting polymer is subjected to conventional post-treatments such as separation, washing, and drying to obtain the desired copolymer.

The copolymer of the present invention is mixed with a process oil in a solution state,
After mixing, the solvent may be removed and used as an oil-extended rubber.

The copolymers of the present invention can be used alone or in blends with natural rubber or other synthetic rubbers such as polybutadiene, polyimprene, emulsion-polymerized styrene-butadiene copolymers, and the like. When used in a blend with natural rubber or other synthetic rubber, the copolymer of the present invention must account for at least 30% by weight of the raw rubber in order to exhibit the excellent properties of the present invention.

Further, the copolymer of the present invention is blended with known compounding agents 1 such as carbon black, process oil, etc., mixed and vulcanized, and then
As a product, it can be used for tire applications such as tire treads, carcass, and sidewalls, or extruded products, automobile window frames, industrial products, anti-vibration rubber, etc., and has excellent rebound resilience and wet skid properties. Since it has a balanced resistance and excellent workability, it can be used particularly as a red for fuel-efficient tires.

[Example 1] Hereinafter, the present invention will be explained with reference to Examples, but these Examples are not intended to limit the present invention.

Note that measurements of various characteristics were carried out using the following methods.

The styrene chain distribution of random styrene-butadiene copolymers is analyzed with a method recently developed by Naka et al. Specifically, the styrene chain distribution is analyzed by gel permeation chromatogram (GPC) of the decomposed product obtained by ozone cleavage of all the double bonds of the butadiene unit (Proceedings of the Society of Polymer Science, Vol. 28). No. 9, page 2055)
The proportion of branched components in the copolymer is calculated by peak surface measurement on the high molecular weight side by GPC. Further, the proportion of linear components in the copolymer is calculated from the difference between the total peak area of the copolymer and the peak area on the high molecular weight side by GPG.

Mooney viscosity is 1 using the L rotor in the usual way.
Measured at 00°C. The bound styrene was calculated from the absorption based on phenyl groups at 282 nm using ultraviolet absorption spectroscopy. The microstructure of the butadiene moiety was determined using an infrared spectrophotometer, and the impact resilience was calculated using the Hampton method using a Dunlop trypsometer at a test temperature of 70°C.
Measured at

Abrasion resistance was measured using a Pico abrasion tester.

Wet skid resistance was measured using a device manufactured by the British Road Research Institute. Processability was judged based on the Mooney viscosity of the compound or the roll windability of the compound. The roll windability of the carbon blend was evaluated using a 6-inch roll based on the windability of the carbon blend, operability, etc.

Examples 1 to 3, Comparative Examples 1 to 3 Under a nitrogen atmosphere, 1.2 kg of cyclohexane E, 24 g of tetrahydrofuran, 0.28 kg of styrene, 1.3-
After charging 0.42 kg of butadiene and adjusting the temperature of the mixture to about 70°C while stirring the mixture in the polymerization vessel vigorously, a predetermined amount of n-butyllithium was added as shown in Table 1. The temperature inside the polymerization vessel is t when polymerization is started.
When the polymerization conversion rate of the copolymer finally obtained reaches about 20% by weight, the remaining 1,3-butadiene 0.
30 kg was continuously fed into the polymerization system at a constant rate for 10 minutes using a metering pump.The maximum polymerization temperature was 0 (approximately 98°C).
After the copolymerization is completed, a predetermined amount of silicon tetrachloride is added as shown in Table 1, and then a predetermined amount of 1.3-
Diethyl-2-imidazolidinone was added and reacted for about 10 minutes. To the thus obtained copolymer solution, 5 g of 2,6-tert-butyl-p-cresol was added as a stabilizer, and the solvent was removed by heating to obtain a copolymer.

However, in Comparative Example 3, 1,3-diethyl-2-imidazolidinone was changed to 1 g of methanol and copolymerization was carried out.

The basic properties of the copolymers thus obtained are shown in Table 1. These copolymers were mixed according to the formulation shown in Table 2.
The unvulcanized rubber composition obtained by kneading and mixing in a Banbury mixer was vulcanized at 145°C, and the physical properties were evaluated. The measurement results are shown in Table-1.

Table 2 1) n-Cyclobekyl-2-benzothiazylsulfenamide 2) High-temperature reaction product of diphenylamine and acetone Examples 4 to 7, Comparative Examples 6 and 7 Polymerization similar to that used in Example 1 under nitrogen atmosphere Table on the container
As shown in step 3, predetermined amounts of cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene (hereinafter referred to as primary butadiene) were charged, and while stirring the mixture in the polymerization vessel vigorously, the temperature of this mixture was brought to a predetermined temperature. After adjustment, a predetermined amount of n-butyllithium was added as shown in Table 1 to start copolymerization. Next, as shown in Table 1, the remaining 1,3-butadiene (hereinafter referred to as secondary butadiene) was started to be continuously supplied to the polymerization system at a constant rate using a metering pump. After the supply of secondary butadiene was finished and the polymerization temperature reached the maximum temperature and the copolymerization was completed, a predetermined amount of stannic chloride was added as shown in Table 3, and then a predetermined amount of 1,3 -Dimethyl-2-imidazolidinone was added and reacted for about 10 minutes.

In the thus obtained copolymer solution, as a stabilizer,
5 g of 2,8-di-tert-p-cresol was added and the solvent was removed by heating to obtain a copolymer. The basic properties of the copolymer thus obtained are shown in Table 3.

These copolymers were kneaded and mixed in a Banbury mixer according to the formulation shown in Table 2, and the obtained unvulcanized rubber composition was vulcanized at 145° C. and the physical properties were evaluated. The measurement results are shown in Table-4.

Comparative Examples 4 and 5 Table 1 was placed in a polymerization vessel similar to that used in Example 1 under a nitrogen atmosphere.
As shown in step 3, predetermined amounts of cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged, the temperature inside the polymerization vessel was brought to a predetermined temperature, and stannic acid was added, and then a predetermined amount of 1,3-dimethyl was added. -2-imidazolidinone was added and reacted for about 10 minutes. However, in Comparative Example 5, potassium-tart-butyl oxide (K'rB
) 0.065g was added to the polymerization system. 2,6-sheet te was added as a stabilizer to the copolymer solution thus obtained.
5 g of rt-p-cresol was added and the solvent was removed by heating to obtain a copolymer. The basic properties of the copolymer thus obtained and the properties of the vulcanizate are shown in Tables 3 and 4.

[Effects of the Invention] The random styrene-butadiene copolymer composition according to the present invention has an excellent balance of impact resilience, wet skid resistance, and abrasion resistance, and is suitable for tire applications such as tire treads, carcass, sidewalls, etc. It can be used for extruded products, automobile window frames, anti-vibration rubber, industrial products, etc., and has great industrial significance.

Claims (1)

[Claims] A lithium-terminated copolymer obtained by copolymerizing styrene and butadiene in a hydrocarbon solvent using an organolithium compound as a polymerization initiator, and a general formula ▲ mathematical formula, chemical formula, table, etc. ▼ ( In the formula, R_1 and R_2 each independently represent a C_1 to C_4 alkyl group or an alkoxyalkyl group, Y represents an oxygen atom or a sulfur atom, and n represents an integer of 2 to 4. Mooney viscosity (ML_1_+_4, 1
A styrene-butadiene copolymer having a temperature of 30 to 150 (00°C), in which the bonded styrene is 5 to 45% by weight, and the styrene single chain having one styrene unit is the bonded styrene copolymer.
% by weight or more, long styrene chains consisting of 8 or more styrene units are 5% by weight or less of the bound styrene, linear components account for 25-75% by weight of the copolymer, and branched components account for the remaining 75-25% by weight. % by weight of a random styrene-butadiene copolymer composition.