Polyindanes as processing aid for engineering thermoplastics

Abstract: Thermoplastic resin compositions comprising a blend of a polyindane resin having a weight average molecular weight of less than 10,000, a melting point of at least about 150°C., an unsaturation functionality not exceeding 3 mole % (based on diisopropenylbenzene), and an indane content of at least 90%, with a thermoplastic engineering resin or a thermoplastic engineering resin that is combined with a thermoplastic block copolymer, or with a thermoplastic block copolymer, and a process for making them, are disclosed.

Description: This invention relates to thermoplastic resin compositions comprising blends of a resinous modifier with a thermoplastic block copolymer, and a process for making them. Thermoplastic tri-block copolymers that have an elastomeric block in the center and a thermoplastic block on each end, present processing difficulties that have motivated efforts to modify their properties. For instance, block copolymers such as styrene-isoprene-styrene, styrene-butadiene-styrene and styrene-ethylene-butylene-styrene block copolymers, marketed by Shell Chemical Company under the trademark Kraton R , when processed as adhesives, lose adhesion when heated to the temperature level needed for effective processing, for example, that required to achieve a melt viscosity that facilitates desirably thin coatings of the adhesive. Typical disclosures of modifiers for thermoplastic block copolymers are found in U.S. Patents 4,732,936, 4,104,323 and 4,360,568, which disclose alpha-methylstyrene-p-methylstyrene copolymers, poly(2,6 dimethyl 1,4 phenylene) ether, or poly(2,6 dimethyl 1,4 phenylene) ether in combination with poly(alpha-methylstyrene) as such modifiers in pressure sensitive adhesive applications. However, those modifiers may decrease the glass transition temperatures of the aromatic end blocks of the thermoplastic block copolymers and thereby reduce the cohesive strength of the adhesive at high temperatures, and the relatively high molecular weight of many of the modifying resins make them incompatible with the aromatic end blocks of thermoplastic block copolymers, reducing the tack properties of adhesives based on the modified blends and allowing a third dispersed phase to separate. US-A-4,098,845 to Keck discloses the use of polyindanes to improve the rate of crystallization of polyethylene terephthalates and generally the indane content of the polymers used will be 90% or less. Polymers containing units of indane, 1-pentene and 2-pentene structures are disclosed in US-A-4,205,160. These polymers are useful as lubricants and as molding aids for crystallizable polyester resins, especially polyethylene terephthalate. Thus there is a need for thermoplastic resin compositions comprising blends of a resinous modifier with thermoplastic block copolymers as indicated above, to provide thermoplastic compositions with improved processability, desirably raising the blends' ring and ball softening temperature and the Tg of the aromatic block component of the thermoplastic block copolymer, without lowering the glass transition (T g ) temperatures of the midblocks of the copolymers or causing incompatiblity problems. According to the invention, a thermoplastic resin composition comprising a blend of a resinous modifier with a thermoplastic block copolymer, is characterized in that it comprises 50-99 parts by weight of a thermoplastic block copolymer comprising an aromatic block component, and 1-50 parts by weight of a polyindane resin having a weight average molecular weight of less than 10,000, a melting point of at least 150°C, an unsaturation functionality not exceeding 3 mole % (based on diisopropenylbenzene), and an indane content of at least 90%. The polyindane resin modifiers used in this invention can be blended with thermoplastic tri-block (ABA) copolymers that have an elastomeric block in the center and a thermoplastic block on each end, for instance, styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS), and styrene-ethylene-butylene-styrene block copolymers, marketed by Shell Chemical Company under the trademark Kraton R , as well as block copolymers containing substituted vinyl aromatic and aliphatic blocks and alloys or blends of these polymers. The preferred block copolymers are those marketed under the trademark Kraton R . The preferred blends of the polyindane resin with the block copolymers according to the invention contain 1-50 wt. % of the substantially saturated polyindane resin. As demonstrated in Examples 9-11, the presence of the polyindane resin lowers the melt viscosity of the block copolymer, enhances the glass transition temperature of the end block without affecting that of the midblock and improves the tensile strength, modulus and hardness without lowering the elongation. As indicated, the polyindane resins should be substantially saturated, and preferably the unsaturation functionality should not exceed 1 mole % (based on diisopropenylbenzene), and most preferably be zero. As indicated, the indane content of the resin should be at least 90%, preferably 95% and most preferably 100%. The weight average molecular weight of the resin should be less than 10,000 and the resin should have a melting point of 150°C. or higher, preferably higher than 200°C. The preparation of polyindane resins with varied indane content, molecular weight, and glass transition temperatures is well known to those skilled in the art, for instance by cationic polymerization of diisopropenylbenzene, as described by H. Brunner, et al., J. Polymer Science - Polymer Letters edition, 1958, Volume 28 , p. 629, or, as disclosed in U.S. Patent No. 4,205,160, by the polymerization of m- or p-diisopropenylbenzene diol or m- or p-diisopropenylbenzene. The prior art teaches that such cationic polymerizations yield resins containing indane, 1-pentene and 2-pentene units as shown in I, II and III, seen below, respectively. The relative content of these polymers in a composition may be readily determined by 13 C NMR analysis, in order to ensure that the proportion of the indane units I is at least 90%. In the preparation of polyindane resins for use in the compositions according to the invention by the polymerization of m- or p-diisopropenylbenzene diol or m- or p-diisopropenylbenzene, the m-diisopropenylbenzene isomer is the preferred monomer. If the para isomer is present, the meta isomer content should be at least 95 wt. %, and preferably 98 wt. % or higher. The monomer's concentration in the polymerization medium can be varied in a wide range, although a 25 to 50 wt. % content is preferred for reasons of economy. The aromatic solvent that can be used in this invention include all of the substituted aromatic compounds that are typically used as solvents. These include common solvents such as toluene, xylenes, and ethyl benzene. The halogenated aromatic solvents, such as chlorobenzene, and 1,2-dichlorobenzene, are preferred for their ability to increase the percentage of saturated indane units in the polymer. Halogenated aliphatic solvents can also be used. The catalysts useful in preparing the polyindanes of the present invention include acidic clay catalyst such as those marketed by Harshaw Filtrol Corporation of Los Angeles, California. These clays are acid-activated crystalline clays composed essentially of silica and alumina. A particularly suitable grade is Filtrol 22. Other acid treated clays can also be used such as Filtrol 113 and Filtrol 13. The acidified clay catalyst should be present in a sufficient quantity to yield the desired polyindane. Based on the monomer content, the catalyst level should be 1 to 20 wt.%, and preferably from 5 to 10 wt. %. Other effective catalysts include Bronsted acids and Lewis acids such as boron trifluoride, aluminum trichloride, ethyl aluminum dichloride, titanium tetra chloride, etc.. The polymerization temperature should be above 80°C. and preferably at least 100°C. or higher up to a maximum of 180°C. Lower polymerization temperatures result in increased levels of unsaturation or yield crosslinked products. Typically, the polymerization is conducted by dropwise addition of the m-diisopropenylbenzene monomer to a mixture of the solvent and the catalyst maintained at the desired polymerization temperature. The length of the monomer addition period is not critical, but should be completed as soon as possible. After monomer addition is completed, the monomer is present in a concentration greater than 25 wt. % of the mixture. The polymerization is typically carried out for 1 to 5 hours, and preferably for 1 to 2 hours, after the completion of the monomer addition. Shorter polymerization times have been found to yield polymers containing undesirable unsaturation functionalities, while longer polymerization times yield materials having broader molecular weight distributions. According to the invention, a process for making a thermoplastic resin composition, comprising preparing a resinous modifier and blending it with a thermoplastic block copolymer, is characterized in that the resinous modifier is prepared by the steps of forming a mixture comprising diisopropenylbenzene, an aromatic solvent selected from the group consisting of toluene, xylene, ethyl benzene, halogenated aromatic solvents and halogenated aliphatic solvents and an acidic clay catalyst selected from the group consisting of Bronsted acids, Lewis bases and acid clay catalysts, wherein said diisopropenylbenzene comprises 25 to 50 wt.% of said mixture; maintaining said mixture at a temperature in the range from 80°C. to 180°C. for a period of 1 to 5 hours and then isolating from said mixture a polyindane polymer that has an indane content of 98-100%. and an unsaturation content of less than 3%. The polyindane resin is miscible with block copolymers to varied degrees. The melt viscosity of the blends with block copolymers defined in accordance with the present invention is lowered (and the ring and ball softening temperature and the Tg of the aromatic block component of the thermoplastic block copolymer unchanged or raised), without lowering the critical glass transition (T g ) temperature of the end blocks of the copolymers. The thermoplastic block copolymers include the conventional variety of diene rubbers, AB, and ABA block copolymer rubbers; for instance, the ABA block copolymers having end blocks A formed of vinyl aromatic hydrocarbon monomer such as styrene, methyl styrene or mixtures thereof and a center block B formed of a 1,3-diene such as butadiene or isoprene. The ABA block copolymers may also be hydrogenated to reduce the ethylenic unsaturation content. The ratio of A and B units and the molecular weights of the ABA block copolymers may be varied widely; the A blocks should preferably comprise 2-31 weight percent of the block copolymer. Such block copolymers are widely available commercially both in hydrogenated and unhydrogenated versions. Most preferred are the styrene-isoprene-styrene, styrene-butadiene-styrene, and styrene-ethylene-butadiene-styrene block copolymers marketed under the tradename Kraton. Other thermoplastic block copolymers include styrene-1,3-diene copolymers and graft copolymers, and polyolefin copolymers such as ethylenepropylene copolymers. As indicated, the compositions of this invention can be varied in a range of 1 to 5C weight percent polyindane resin, depending on the miscibility of the resins and the physical properties desired. Compositions containing 1-20 weight percent are preferred. The compositions of this invention can be prepared by either blending in solution or by melt blending. Thus, the resins can be blended in a common solvent such as chlorobenzene or chloroform and the resin blend collected after precipitation in excess methanol. The resin blend is then dried. More conveniently, the compositions are prepared by premixing the components and passing the blend through an extruder maintained at a temperature from 290-310°C. at 150 rpm. The compositions are characterized for melt viscosity, glass transition temperature (Tg) and heat distortion temperature. Compositions of the present invention can be molded or extruded into useful articles of manufacture by means known to those skilled in the art. Conventional additives, such as reinforcing and nonreinforcing fillers, pigments, stabilizers and lubricants, can be employed in the practice of the present invention. EXAMPLE 1 Preparation of Polyindane Resin Chlorobenzene (50 g) and Filtrol 22 acidified clay (5 g) were charged into a 3-neck flask and maintained under stirring at 100°C. m-Diisopropenylbenzene (50 g) was added dropwise while maintaining the temperature at 100°C. The polymerization was carried out for 1 hour at 100°C. after which the clay was filtered off and the polymer was precipitated in excess methanol. The polymer was filtered off and dried in a vacuum oven. The polymer had the following properties: melting point 215°C., Tg 173°C. and weight average molecular weight (SEC) 4370, indane content 100%. Other polyindane resins having different indane contents and exhibiting varied Tgs were prepared in a similar fashion by varying polymerization conditions, including polymerization temperature and the reaction medium. EXAMPLES 2-5 Table 1 summarizes the melt viscosity, Tg and HDT of impact polyphenylene ether compositions comprising a poly(2,6-dimethyl 1,4-phenylene) ether, an ABA type block copolymer and the polyindane resin of Example 1. Examples 2 and 3 are controls that do not contain the block copolymer. This data shows that the inclusion of the polyindane substantially lowers the melt viscosity with only marginal lowering in Tg or HDT. EXAMPLES 6-8 In Table 2 is shown the physical properties of an impact polyphenylene ether composition comprising 85/15/5 parts by weight of poly(2,6-dimethyl-1,4-phenylene) ether, polyindane resin and Kraton G 1652 (Example 8). Examples 6 and 7 are for reference purposes only. The results show that the PPE composition of Example 8 has good impact strength with other physical properties being almost comparable to that of the control PPE. The composition's melt viscosity is half of the control and yet the HDT is only marginally lowered. EXAMPLES 9-11 Table 3 compares the properties of a styrene-ethylene-butadiene-styrene (SEBS) linear block copolymer which is unmodified by polyindane resin (Example 9) with 80/20 and 70/30 blends (Examples 10 and 11, respectively) of the block copolymer to polyindane. The SEBS block copolymer used was Kraton G 1650 sold by Shell Chemical Company, Oak Brook, Illinois. The presence of the polyindane resin results in enhanced glass transition temperature of the end block without affecting that of the midblock and improves tensile strength, modulus and hardness without lowering the elongation. EXAMPLES 12-23 Table 4 compares the properties of the modified SEBS block copolymer Kraton G 1650 with the properties of other block copolymers commercially available from Shell Chemical Company, Oak Brook, Illinois when modified according to the invention by the indicated proportions of polyindane resins.

Claims: A thermoplastic resin composition comprising a blend of a resinous modifier with a thermoplastic block copolymer, characterized in that it comprises 50-99 parts by weight of a thermoplastic block copolymer comprising an aromatic block component, and 1-50 parts by weight of a polyindane resin having a weight average molecular weight of less than 10,000, a melting point of at least 150°C, an unsaturation functionality not exceeding 3 mole % (based on diisopropenylbenzene), and an indane content of at least 90%. A thermoplastic resin composition as claimed in claim 1, further characterized in that the unsaturation functionality of the polyindane resins does not exceed 1 mole % (based on diisopropenylbenzene). A thermoplastic resin composition as claimed in claim 2, further characterized in that the indane content of the resin is at least 95%. A thermoplastic resin composition as claimed in claim 3, further characterized in that the indane content of the resin is 100%. A thermoplastic resin composition as claimed in any one of the preceding claims, further characterized in that the melting point of the indane resin is above 200°C. A thermoplastic resin composition as claimed in any one of the preceding claims, further characterized in that it comprises 50 to 99 wt. % of a thermoplastic tri-block (ABA) copolymer that has an elastomeric block in the center and a thermoplastic block on each end. A thermoplastic resin composition as claimed in claim 6, further characterized in that the ABA copolymer is a styrene-isoprene-styrene (SIS), a styrene-butadiene-styrene (SBS), or a styrene-ethylene-butylene-styrene block copolymer. A process for making a thermoplastic resin composition comprising preparing a resinous modifier and blending it with a thermoplastic block copolymer comprising an aromatic block component, characterized in that the resinous modifier is prepared by the steps of forming a mixture comprising diisopropenylbenzene, an aromatic solvent selected from the group consisting of toluene, xylene, ethyl benzene, halogenated aromatic solvents and halogenated aliphatic solvents and an acidic clay catalyst selected from the group consisting of Bronsted acids, Lewis bases and acid clay catalysts, wherein said diisopropenylbenzene comprises 25 to 50 wt.% of said mixture; maintaining said mixture at a temperature in the range from 80°C to 180°C. for a period of about 1 to 5 hours and then isolating from said mixture a polyindane polymer that has an indane content of 98-100% and an unsaturation content of less than 3%. A process for making a thermoplastic resin composition as claimed in claim 8, further characterized in that the polyindane polymer is blended with the thermoplastic block copolymer by blending the components in solution and then precipitating the blend, by melt blending, or by extruding a mixture of the components. The process of claim 8 wherein the thermoplastic block copolymer is selected from the group consisting of styrene-butadiene-styrene block copolymers, hydrogenated styrene-butadiene-styrene block copolymers, styrene-1,3 diene copolymers and graft copolymers and polyolefin.

Inventors: CHU SUNG G, PATNAIK BIRENDRA KUMAR, SHIH KEITH SHANN, CHU, SUNG G., PATNAIK, BIRENDRA KUMAR, SHIH, KEITH SHANN
Applicants: HERCULES INC, HERCULES INCORPORATED
Application year: 1990
Main classification: C08L71
IPC codes: C08L65, C08L53, C08L81, C08L101, C08L45, C08L87, C08L71