NL8903136A - POLYMER COMPOSITIONS AND METHOD FOR PREPARING THE SAME - Google Patents

Description

Polymer compositions and method for their preparation.

The Applicants mention as inventors:

Sergio Custro in Ravenna, Italy, and Alessandro Zazzetta in Cesena, Italy.

The present invention relates to block copolymer type compositions obtained by block copolymerization of conjugated diene monomers and vinyl aromatic monomers.

In recent years, the block copolymers obtained by block copolymerization of conjugated diene monomers with vinyl aromatic monomers, such as, for example, the block copolymers of polybutadiene and polystyrene, and the block copolymers of polyisoprene with polystyrene, have shown particular development. Such copolymers can be used as such, i.e. in the same form as they are formed by the living anionic copolymerization, as well as after their partial or complete hydrogenation.

This is the case with the linear block copolymers, which are composed of alternating blocks of poly-dienes and polyvinylarenes, with a special structure and distribution of the individual blocks, and which have a (I) or (II) -type structural formula, which have a exhibit an extremely favorable balance between physical and mechanical properties. Such block copolymers, as well as their derivatives, have been described by the present applicant in Dutch patent application no. 87 02674 and in a also filed patent application.

Mixing block copolymers with each other, and with impact-resistant and non-impact-resistant polystyrene to obtain resins endowed with improved properties is also known in the art.

Compositions and / or block copolymers characterized by the use of polymer structures suitable for all of these applications for which transparent, impact resistant polystyrene was previously used, or is still used today, are disclosed, for example, in British Patent Nos. 1,130,770; and 1,335,077; and U.S. Patent No. 4,086,298.

However, the copolymers for which exclusive rights have been claimed in these publications do not exhibit an optimal balance between rheological properties, impact strength and transparency.

Such a balance of properties is further influenced by the possible use of polystyrene, which on the one hand improves the optical properties, but on the other hand decreases the impact strength of the compositions thus obtained.

The drawbacks of the prior art are overcome by the polymer compositions of the present invention, which are composed of blends of the two block copolymers, comprising: (a) 40 to 90% by weight of a four-block linear linear copolymer , which can be represented by the formula

Bi-t-Ai-b2-a2 (I) or B1-A1-B2-T-A2 (II) in which: A 1 and A 2 are polyvinyl aromatic blocks; and B2 are polydiene blocks; T is a copolymer chain portion formed by randomly bonded diene and vinyl aromatic monomer units; b) 10 to 60 parts by weight of a linear two-block copolymer, which may be either represented by the formula: B3-T-A3 (III), wherein: A- is a dovolvlavomatis block, which is either is similar to, or differs from, table A, wick or block; a polydiene block which is either equal to or different from the B1 block or the B2 block; T has the above-mentioned meaning; or, otherwise, by the formula: b3-a3 (IV).

Accordingly, and according to a first aspect thereof, the present invention relates to new polymer compositions comprising: (a) 40 to 90% by weight of a block copolymer of general formula (I) or (II); (b) 10 to 60% by weight of a block copolymer of general formula (III) or (IV), in which the symbols A,, A2, A3, B ^, B2, B3 and T have the meanings shown above.

The polymer compositions are endowed with very good impact strength and processability properties, combined with high transparency, making them suitable for all existing applications for the clear impact resistant materials.

Also, methods of simultaneously obtaining both of the above ingredients of the mixture and during the same synthesis process are within the scope of the present invention.

The polymer compositions of the present invention are characterized in that the weight-average molecular weight of the four-block copolymer of formula (I) or (II) is in the range of 50,000 to 300,000, while the weight-average molecular weight of the two-block copolymer is in the range of 20,000 to 150,000.

In the same compositions, the weight percent of the random block T is in the range of 5 to 50%, preferably 10 to 25%, based on the total of the two copolymers making up the mixture.

In said compositions, the total amount of vinyl aromatic monomer units is in the range of 60 to 90% by weight, the remainder being up to 100% by the diene monomer units.

In the above definitions, blocks A.

1 '& 2 and B] y b2 and B3 virtually pure blocks; i.e., they are composed almost entirely of vinyl arene and diene units.

In a practical preferred embodiment, the blocks Β ^, B2 and B ^ are polystyrene blocks and T is any styrene-butadiene copolymer.

Also, in a practically preferred embodiment, the total content of diene units in the polymer composition is in the range of 20 to 30% by weight, and the weight average molecular weight of the four-block copolymer is in the range of 100,000 to 200,000; and the weight average molecular weight of the two-block copolymer is in the range of 40,000 to 100,000. To the compositions, another polystyrene resin, such as e.g. polystyrene or impact resistant polystyrene, can be added in such an amount so as not to compromise the combination of properties of the binary composition.

Polymer compositions of the present invention are an advancement in terms of properties compared to the block copolymers of formula (I) or (II) when considered on a separate basis.

The linear block copolymer composed of four alternating blocks and meeting the general formula (I) or (II) of the present invention can be obtained by polymerization, by working in an organic solvent, optionally with suitable amounts of an aliphatic or cyclo- aliphatic polar compound selected from ethers or amines at temperatures ranging from 30 ° C to 150 ° C, and at pressures equal to or greater than atmospheric pressure in the presence of the alkyl metal or aryl metal initiators, such as commonly used in the synthesis of polymers by the living anionic polymerization process.

Such a synthesis route is described in Dutch patent application No. 87 02674 which relates to the description of such copolymers and to the method of synthesizing them. On the other hand, the two-block polymers satisfying the above formulas (III) or (IV) can be synthesized by methods known in the art, as well as by the same synthesis method as described in the above-mentioned patent application, wherein the reaction is limited to the first step. More specifically, for the synthesis of the copolymers of formula (III), metered amounts of butadiene and styrene are fed together as a mixture to a reactor, and the solution polymerization is carried out in a hydrocarbon, with a suitable initiator for the living anionic polymerization, until the monomer conversion is complete or substantially complete; in this way, a living two-block copolymer b3-T-A3 is formed, which is composed of non-pure blocks, ie, blocks bonded together by a copolymer portion of a chain, composed of randomly bonded monomer units of butadiene and styrene.

The polymer formed is recovered from the living active centers after the previous quenching by adding a compound which has an acidic character.

The recovery of the polymer material is carried out according to the usual methods, such as, for example, by steam evaporation of the solvent and drying of the polymer.

The copolymer of formula (IV) is obtained by anionic polymerization, with the sequential addition of the monomers of the prior art.

The components of the polymeric compositions of the present invention can be mixed and formulated according to the modalities and routes as are well known in the art. For example, the ingredients can be mixed in the molten state and extruded or mixed in Banbury type mixers, or they can be mixed as solutions. The present applicant has also developed new and original methods - and these are a further object of the present invention that allow the two components to be formed to be formed simultaneously and by a single synthesis method.

According to one of such methods, the synthesis is carried out according to the following steps: (a) a first step, during which a mixture is copolymerized in. presence of initiators, until the conversion of the monomers is almost complete, which mixture is composed of an aromatic vinyl monomer and a conjugated diene monomer in an α-polar solvent selected from the solvents in which polystyrene, which is a weight-average molecule has weight ranging from 30,000 to 120,000 and is soluble at concentrations of 5 to 20% by weight. The initiators are alkyl-lithium compounds to produce a living polymer system. The solvent system can contain polar compounds (such as ethers, amines, etc.) at a maximum concentration of 0.1% by weight based on the solvent. The weight percent of the monomers added as a mixture to the first reaction step of the process of the present invention is in the range of 30 to 60% by weight, based on all monomers added to the reaction. During the reaction described above, a living copolymer of the

Bl-T-Ai type formed.

(2) A second step, in which a percentage of the living active centers formed during the first reaction step, are quenched by the addition to the reaction system of compounds, which are characterized by these acid hydrogen atoms (H 2 O, alkali) burrows, etc.) in their chemical structure.

The amount of active center quenching agents added to the second step of such a process is in the range of from 10 to 50 mole percent based on the number of moles of the initiator added to the first step.

(3) A third step, in which a conjugated diene is added to the living system from the second step and undergoes complete conversion.

(4) A fourth step in which an aromatic vinyl monomer is added and almost completely converted.

(5) A fifth step in which the living active centers are completely extinguished by adding a compound with an acidic activity.

In such a manner, the mixture of the two copolymers b1-T-Ai-b2-A2 + VT-Aj is obtained.

This process is carried out under the above-mentioned general conditions of temperature and pressure, i.e. at temperature values ranging from 30 ° C to 150 ° C and below atmospheric or above atmospheric pressure.

One of the variants, which form alternative routes to the above process, comprises, at the end of the first polymerization step of the monomer mixture, a second step in which a second part initiator is added.

Such a pathway leads to the formation of an additional number of active centers on which pure block copolymers previously described by the formula b3-t-a3 are formed.

In that case, the various subsequent steps are: (1) the synthesis of a pure diene block; (2) the synthesis of a pure aromatic vinyl block following the diene block; (3) adding an additional part initiator; (4) adding a mixture composed of a diene monomer and an aromatic vinyl monomer. The amount of monomers added to each other ranges from 30 to 60% based on all monomers added to the reaction.

(5) quenching the living active centers by means of compounds containing acidic hydrogen atoms.

Two polymer mixtures can be obtained by methods analogous to those described above B1-A1 "B2_T-A2 + B1-Al or B1" T-A1-B2-A2 + B2-A2 ·

The preferred initiators for the intended purpose are those belonging to the group consisting of both linear and branched alkyl-lithium compounds, and including n-butyl lithium and sec-butyl lithium.

These initiators are commonly used in the various steps of the process in amounts ranging from 0.025 to 0.2 parts by weight for every 100 parts by weight of the polymerized monomer.

The solvents suitable for the intended purpose are the non-polar solvents, including those in which the polyvinyl aromatic blocks having a weight average molecular weight in the range of 50,000 to 200,000 are soluble; among the most suitable of these are listed cyclohexane and benzene.

These solvents can resist polar compounds (such as ethers, amines, etc.) whose presence in addition to and an increase in the rate of the polymerization reaction taking place in the various steps, also an increase in the weight of the random copolymeric moiety; e T causes; among these, tetrahydrofuran has the precursor.

The following experimental examples are appropriate and not limiting to the scope of the present invention.

Example 1 60 g of water-free chexane, 55 g of 99% pure styrene and 13 g (99.85% pure) butadiene were fed to a 1000 cm stirred reactor; the temperature of the mass was raised to 50 ° C, and 0.055 g of sec-butyl-lithium (in solution in n-hexane) was added.

25 minutes later, the reaction mass reaches the temperature of 75 ° C and the conversion of the monomers was almost complete. Then 0.009 g of pure methanol and 7 g of butadiene were added successively to the system. After 10 minutes, the reaction mass reached the temperature of 85 ° C and the conversion of butadiene was almost complete.

Finally, 25 g of styrene was added, and 15 min later the conversion was almost complete, with the temperature of the mass having reached 90 ° C.

Quenching of the live active centers was performed by adding 0.5 cm 2 to the polymer solution.

1.0 g of triphenyl-nonyl-phosphite and 0.2 g of pentaerythrityl-tetraalkyl- (3,5-di-tert-butyl-4-hydroxyphenyl-propionate) were added to the polymer solution.

The recovery of the polymer mixture was carried out by means of the steam distillate of the reaction solvent and subsequent drying in a vacuum oven at 60 ° C for 2-4 hours.

The physical properties of the two components of the polymer blend are listed in Table 1. The mechanical and optical properties of samples formed by pressing at 180 ° C are summarized in Table 2.

Table No. 1

Mg x 10-3 Mg x 10-3 Total Block MFI (4) Example (B- ^ TABjAj) (B. TA ·.) Styrene styrene (g / 10

No. (17 tl)% (2)% (3) minutes) 1 140 80 80 68 4.5

Analysis GPC (1) I.R. analysis (2)

Breakdown with OsO. (3) 200 ° Cf 5 kg "(4)

Table No. 2 - Transparency 4 2 ^ 2 - Tensile strength kg / cm 230 - Elongation at break% 5 35 - Modulus kg / cm 8000 - IZOD with notch at 23 ° C kg x cm / cm 2.5

Example 2 850 g anhydrous cyclohexane, 37.5 g styrene and 3 12.5 g butadiene were fed to a 2000 cm stirred reactor; the temperature of the system was raised to 55 ° C and 0.040 g of n-butyl lithium (in solution in n-hexane) was added.

45 minutes later, the reaction mass reached the temperature of 68 ° C and the conversion of the monomers was almost complete.

0.032 g of n-butyl lithium and 37.5 g of butadiene were then added successively to the reaction solution; after 20 min, the reaction mass reached the temperature of 78 ° C and the conversion was almost complete.

112.5 g of styrene was then added to the polymer solution and 60 min later the conversion of the monomer was complete.

The reaction was then quenched by adding 2 g of methanol to the solution containing the polymer mixture. The addition of the anti-oxidant, and the recovery and drying of the polymer were performed in the same manner as in Example 1.

The physical properties of the two components of the polymer blend are listed in Table 3.

The mechanical and optical properties of samples molded at 180 ° C are summarized in Table 4.

Table No. 3

Total Block MPI

Example Mg x 10 Mg x 10 styrene styrene (g / 10

No. ^ B1TA1®2 ^ 2 ^ {B2A2)%% minutes} 2 170 85. 75 65 3.5

Table No. 4 - Transparency% „86 - Tensile strength kg / cnn 165 - Elongation at break% - 100 - Modulus kg / cin 7,000 - IZOD with notch at 23 ° C kg x cm / cm 3.2

Example 3 1.2 g of cyclohexane, 0.3 g of tetrahydrofuran, 100 g of styrene and 45 g of butadiene were fed to a 1.5 liter reactor; the temperature of the mass was raised to 50 ° C, and 0.12 g of n-butyl lithium (in solution in n-hexane) was added.

30 minutes later, the reaction mass reached the temperature of 80 ° C and the conversion of the monomers was almost complete.

Subsequently, 0.012 g of O 2 O and 15 g of butadiene were added successively to the system.

10 minutes later, the reaction mass reached the temperature of 90 ° C and the conversion of butadiene was complete.

Finally, 40 g of styrene was added and after 15 minutes of reaction, the conversion was complete.

Before recovery of the solid polymer, the live active centers were quenched by adding 2 g of isopropyl alcohol to the system.

After the addition of antioxidant as in Example 1, recovery of the solid polymer was performed by steam distillation of the solvent, and subsequent drying of the solid residue at 65 ° C for 24 hours.

The physicochemical properties are listed in Table 5.

Table No. 5

,,. Block _-5, MFI

Example styrene styrene Hg x 10 J Mg x 10 J (g / 10 * * (BjTAjB2A2) (B ^ TA2> minutes) 3 70 50 130 80 8.5

Example 4 5 kg of the mixture described in Example 3 was mixed with 5 kg of commercially available crystalline polystyrene ~ Mg (Gpc) = 250 x 10. The mass was fed to a twin screw extruder equipped with a heated jacket. This operation was repeated twice to allow for optimal mixing; the material was then converted into 0.5 cm long granules.

The properties of the compound thus prepared were determined for samples molded at 180 ° C and are listed in Table No. 6.

Table No. 6 g / 10 minutes 8.2 - Transparency% 90 - Tensile strength kg / cm2 185 - Elongation at break% 10o

Modulus kg / cm2 12,000 “IZOD with notch kg χ cm / cm 3.5

Example 5 600 g anhydrous cyclohexane and 30 g (99.84% pure) butadiene were fed to a 1 liter reactor; the mass was heated to 60 ° C and 0.09 g of sec.-butyl-lithium was added.

20 minutes later, the polymerization of butadiene was complete and the reaction temperature was about 60 ° C.

70 g (99.9% pure) styrene was then added to the system, and the reaction was complete within 20 min; during this time, the reaction mass reached the temperature of 82 ° C.

0.058 g of initiator (n-butyl-lithium) and a reaction mixture composed of 70 g of styrene and 30 g of butadiene were added successively to the reaction mass.

The reaction took place within a 25 minute period and the final reaction temperature was 102 ° C.

At the end of the procedure, 3 g of methyl alcohol was added to the system to quench the active centers.

To the polymer solution, 0.8 g of TNFF (triphenylnonyl-phosphite) and 0.15 g of pentaerythrityl-tetraalkyl- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate were added to the polymer solution.

The polymer was recovered by steam distillation of the solvent and the recovered polymer was then dried in a vacuum oven at 60 ° C for 36 hours.

The physicochemical properties and mechanical properties of the polymer blend are listed in Tables 7 and 8.

Table No. 7

Total Block MFI

Example styrene styrene Mg x 10, Mg x 10. (g / 10

No%% (B ^ Aj ^ T ^) (B ^ TA2) minutes 5 70 56 125 75 10

Table No. 8 - Transparency% 85 - Elongation at break% 125 - Tensile strength kg / ciru 1.10 - Modulus kg / cni 6,800 - IZOD with notch at 23 ° C kg x cm / cm 5.0

Claims (14)

Block copolymer type polymer composition obtained by block copolymerization of conjugated diene monomers and vinyl aromatic monomers, characterized in that it comprises: (a) 40 to 90% by weight of a linear copolymer of four alternating blocks, which may be represented by the formula b1-t-a1-b2-a2 (I) or B1-A1-B2-T-A2 (II) wherein: A-1 and A2 are polyvinyl aromatic blocks; and B2 are polydiene blocks; T is a copolymer chain portion formed by randomly bonded diene and vinyl aromatic monomer units; (b) 10 to 60 parts by weight of a linear two-block copolymer, which may be either represented by the formula: b3-t-a3 (III) wherein: A3 is a polyvinyl aromatic block, which is either equal to or different of, the A ^ block or the A2 block; B3 is a polydiene block, which is either equal to or different from the B1 block or the B2 block; T has the above-mentioned meaning; or, otherwise, by the formula: b3-a3 (IV). Polymer composition according to claim 1, characterized in that the linear 4-block polymer (I) or (II) has a weight average molecular weight in the range of 50,000 to 300,000. Polymer composition according to claims 1 and 2, characterized in that the average molecular weight of the polymers indicated by formulas (III) or (IV) is in the range from 20,000 to 150,000. Polymer composition according to one or more of the preceding claims, characterized in that in the composition the total amount of vinyl aromatic monomer units is in the range from 60 to 90% by weight, the remainder being up to 100% by diene monomer units. Polymer composition according to the preceding claims, characterized in that the diene blocks are polybutadiene blocks and the polyvinyl aromatic blocks are polystyrene blocks. Polymer composition according to the preceding claims, characterized in that the individual components are mixed to form said composition. Process for preparing a polymer composition according to the preceding claims, characterized in that: - in a first step, measured amounts of a diene and a vinyl aromatic monomer, mixed together, are polymerized by live anionic polymerization, until complete, or almost complete monomer conversion; - in a second step, a percentage which is in the range of 10 to 60% of the active living centers formed by the first reaction step is partially quenched by the addition of compounds containing acidic hydrogen atoms; - a measured amount of diene is added to the mass coming out of the second reaction step, and polymerized in a third step by means of the living anionic polymerization route, until the conversion of supplied diene is complete or substantially complete; a metered amount of vinyl aromatic monomer is added to the product from the third step, and is polymerized in a fourth step, until the conversion of the added vinyl aromatic monomer is complete or substantially complete; the polymer mixture is recovered from the polymerization products of the fourth step after the prior complete quenching of the living active centers by means of a compound containing an acidic hydrogen atom, thus the polymer mixture composed of the two polymers BrT- WA2 + ΒΓΤ “Α1 is obtained. Process for the preparation of a polymer composition according to claims 1 to 5, characterized in that: - in a first step, polymerized amounts of a conjugated diene are polymerized by living anionic polymerization, to complete or almost complete monomer conversion; - in a second step, a metered amount of a vinyl aromatic monomer is added to the reaction mass from the first step and polymerized until the conversion of the added vinyl aromatic monomer is complete or substantially complete; - in a third step, partially quenching a percentage, which is in the range of 10 to 60% of the active centers formed in the previous steps, by adding compounds containing acidic hydrogen atoms executed; in a fourth step, a mixture composed of metered amounts of a diene and a vinyl aromatic monomer is added, and the polymerization is continued until the conversion of the monomers is complete, or nearly complete; - the polymer mixture formed from the fourth step is recovered after the previous quenching of the living active centers, by means of a compound containing acidic hydrogen atoms, in this way the polymer mixture composed of the polymers B1 ~ A1 "B2" T-A2 + B1 ~ A1 is obtained. Process for preparing a polymer composition according to claims 1 to 5, characterized in that: - in a first step, measured amounts of a conjugated diene are polymerized by existing anionic polymerization, to complete, or almost complete, monomer conversion. ; - in a second step, a metered amount of a vinyl aromatic monomer is added to the reaction mass from the first step and polymerized / until the conversion of the added vinyl aromatic monomer is complete or substantially complete; - in a third step, an additional amount of an anionic polymerization reaction conductor is added; - in a fourth step, measured amounts of a diene and a vinyl aromatic monomer, mixed together, and in amounts ranging from 30 to 60%, based on the monomers fed to the process, are added and the polymerization is continue until complete, or almost complete, conversion of the monomers is obtained; - the copolymer is recovered from the polymerization products from the fourth step, after the prior quenching of the living active centers by the addition of a compound containing acidic hydrogen atoms, thus the polymer mixture which is composed from the two polymers B - ^ - A ^ -B2 ~ T-A2 + B2_T-A2 is obtained. Process for the preparation of a polymer composition according to claims 1 to 5, characterized in that: - in a first step, polymerized polymerized amounts of a conjugated diene and a vinyl aromatic monomer are mixed together by living anionic polymerization. , to complete or nearly complete monomer conversion; - in a second step, an additional amount of a initiator for the living anionic polymerization reaction is added; in a third step, a metered amount of a conjugated diene is added and the polymerization is continued until the conversion of the monomer is complete or substantially complete; - in a fourth step, a metered amount of a vinyl aromatic monomer is added and the polymerization is continued until the complete conversion of the monomer is obtained; - the mixture of polymers formed and coming from the fourth step is recovered, after complete extinction of the living active centers by means of a compound containing acidic hydrogen atoms, in this way a polymer mixture composed of the two polymers B1 “T-A1_B2_A2 + B2_A2 is obtained. Process according to claims 7, 8, 9 and 10, characterized in that the polymerization is carried out by applying in an organic, aliphatic or cycloaliphatic solvent at temperatures in the range from 30 to 150 ° C and at a pressure equal to, or higher than, atmospheric pressure, in the presence of an alkyl metal or an aryl metal compound. The process according to claim 11, characterized in that the polymerization can be carried out in the presence of at least one linear or cyclic polar compound selected from ethers or amines in amounts ranging from 0.01 to 0.1 parts by weight, based on the solvent. Process according to claims 7, 8, 9 and 10, characterized in that the solvent is cyclohexane and the reaction temperature is in the range of 50 to 100 ° C, the initiator is an alkyl lithium containing 3 to 7 carbon atoms the alkyl group, and the initiator is used in amounts ranging from 0.025 to 0.20 parts by weight per 100 parts by weight of vinyl aromatic monomers. Process according to claims 7, 8, 9, 10, characterized in that the diene is butadiene and the vinyl aromatic compound is styrene.