THERMOPLASTIC POLYURETHANE RESIN FOR MELT SPINNING

Abstract: There is disclosed a polyurethaneurea resin consisting of a polymer represented by the following chemical formula (I): [A-O-(O)C-NH-D-NH-C(O)-NH-D-NH-C(O)-O]n [I] wherein A represents an organopolyol residue having a number average molecular weight of approximately 500 to 5,000 and a weight average molecular weight/number average molecular weight (MW/MN) of 1.5 to 2.5 with the number of functional groups ranging from 1.8 to 2.2, D represents an aromatic organodiisocyanate residue ranging, in the number of functional groups, from 1.8 to 2.2, and n represents the number of repeat units. This resin is superior in thermal resistance and elastic recovery, so that it is suitable to melt spinning to make useful elastic fibers.

Description: THERMOPLASTIC POLYURETHANE RESIN FOR MELT SPINNING Technical Field The present invention relates, in general, to a poiyurethane elastomer and, more particularly, to a thermoplastic poiyurethane urea resin that is of high thermal resistance and high elastic recovery. Also, the present invention is concerned with a method for preparing such a thermoplastic poiyurethane resin. Background Art As widely known in the art, elastic fibers are typically prepared by four spinning techniques: dry spinning, wet spinning, chemical spinning, and melt spinning. Of them, the most widely used is the dry spinning technique, which also has turned out to give the best physical properties. Exemplified are those disclosed in U.S. Pat. No. 4,973,647 and 5,362,432. While spinning, the conventional dry spinning is, however, obliged to remove or evaporate the solvent which is used to produce a polyurethane-urea resin solution by solution polymerization. For this, there is needed a complicated facility. Also, the high danger of the removed or evaporated solvent producing environmental pollution such as water pollution or air pollution demands a high performance facility for recovering the solvent, giving rise to a significant increase in facility investment. Thus, the manufacturing cost of the elastic fiber is higher than that of any other fiber, restricting the application of the elastic fiber. When being applied for the manufacture of clothes to come in direct contact with skin, such as swimming suits, sports wear, lingerie, foundation garments, underclothes, stockings, socks and the like, the elastic fiber made by such dry spinning may have a harmful influence on the skin or the respiratory organ if the solvent is not completely removed. Another disadvantage of the dry spinning is shrinkage. Because the elastic fibers made by the dry spinning are based on a urethane-urea bond, they are superior in thermal resistance and elastic recovery, but continue to shrink during the finishing of woven fabric, so that it is difficult to calculate the finished width. Also, the products prepared from the fabrics show continuous shrinkage after washing, providing poorer elasticity and wearing comfort . With all of the problems occurring in the dry spinning, the wet spinning or chemical spinning has a further problem of being difficult in controlling process conditions and showing large deviations in the physical properties of the spun elastic fibers. For this reason, the wet spinning or chemical spinning is only partially employed. Hence, extensive research has been and continues to be directed to elastic fiber-making processes which can avoid the problems encountered in the conventional technologies, such as enormous facility investment, solvent recovery, environmental pollution, high manufacturing cost, the negative influence of the solvent remnant, the continuous shrinkage upon finishing and washing, the difficulties in controlling process conditions, etc. Basically, the research direction is to make elastic fibers without using any solvent. As a result, a melt spinning process was developed in which monomer materials are subjected to melt bulk polymerization and spun through an extruder. To fulfill this melt spinning process, a few premises must be met. First, since the melt spinning process, as included in its appellation, comprises a melting step by heat and a spinning step through a nozzle, the resin available in this process must be thermoplastic. Also, the resin is able to be molten to a sufficient extent because un-melts, if remaining upon heating, cause cut fibers upon spinning. Unlike the resins useful in the dry spinning, wet spinning and chemical spinning, the resins which satisfy these preconditions, however, cannot contain abundant cross linkages, so that they have a limit in increasing the thermal resistance of the resulting elastic fibers . Generally, a urethane hard segment ranges, in melting point, from 190 °C to 230 °C whereas a urea hard segment melts at 250-290°C. Therefore, the more urea bonds there are, the higher the thermal resistance of elastomer is. Aliphatic primary amines, which are used to form urea bonds for dry spinning, are reacted with organoisocyanates at a too high rate of speed to accomplish a homogeneous mix of these materials. Unless the materials are mixed homogeneously, the poiyurethane resins prepared from urethane and urea cannot be molten in an extruder to the extent that they are used for melt spinning, because the aliphatic primary amines enter cross linking upon melt bulk polymerization. Owing to this difficulty in reactivity control, industrially available melt spinning processes have not been developed, thus far. Recently, advanced research pertaining to this art have been introduced. For example, Korean Pat. Laid-Open No. 98-702182 discloses aliphatic organoisocyanates which are very slow in reactivity in order to control the reaction rate for urea bonds. According to this patent, prepolymers prepared from the organoisocyanates are decreased in temperature and added with melting aids, followed by the reaction with aliphatic primary amines. The polymers thus obtained are believed to be not as good in thermal resistance as the polymers of the conventional techniques owing to the absence of benzene rings. In addition, even higher prices of the organoisocyanates than the conventional aromatic organoisocyanates are certainly a barrier in commercializing the disclosed process. Most of the resins which have been used for melt spinning, thus far, are based on urethane bond: o I! jNTj-j — Q urethane bond On the other hand, the resins for wet and/or chemical spinning are based on urethane-urea bond: o o - NH — C — O — — NH — C — NH - urethane and urea bond The urethane bond-based resins are inferior in thermal resistance to the urethane-urea bond-based resins owing to the weakness of hydrogen bond. Weaker hydrogen bonds lead to poorer thermal resistance and electric recovery, debasing the value of elastic fiber. For this reason, the melt spinning process is not prevailing. Much effort has been made to overcome these problems, resulting in a remarkable advance in both polymerization and melt spinning techniques for thermoplastic poiyurethane resins. On the whole, research is now proceeded in two directions: at a polymerization stage, starting materials are modified to prepare resins with the thermal resistance and elasticity sufficient for melt spinning; and at a spinning stage, prepolymers serving as crosslinking agents are added to introduce allophanate linkages. One of the conventional polymerization techniques which are known to provide the most excellent physical properties for elastic fibers, is based on the control in the composition and molecular weight of the polyol component, that is, the soft segment of a poiyurethane resin. For example, in order to obtain high elastic recovery and thermal res istance , the compos ition and molecular weight of the polyol are de f ined as fol lows : . total number of carbon atoms number of ester bonds n n ^ number of methyl group n ~ total number of carbon atoms ~ Techniques pertaining to this polymerization are disclosed in U.S. Pat. No. 5,290,905 and 5,310,852 and Korean Pat. Laid-Open Publication No. 90-18430, 91-16808 and 93-701645, which all teach the crystallization of polyols through the increase of their molecular weight, thereby improving elastic recovery and thermal resistance. Turning to the techniques at a spinning stage, crosslinking agents are fed when thermoplastic poiyurethane elastomers prepared in specially designed reactors are melt-spun, as disclosed in U.S. Pat. No. 5,391,682 and Korean Pat. Laid-Open Publication No. 94-701414. The thermoplastic poiyurethane resins are reported to be prepared in a prepolymer process. In detail, a prepolymer is first prepared in a reacting vessel using a perforated plate and mixed with a chain coupling agent in a high-speed mixer. The mixture is then fed in a twin screw extruder and stayed for about 6 in on the average at a maximal temperature of 250-260°C. According to this technique, there are allegedly produced high molecular weight poiyurethane elastomers with few small mass particles, whose molecular weights are distributed in a narrow range. Next, the thermoplastic poiyurethane resins are crosslink- spun in a spinner connected to a static mixer equipped with a means capable of feeding the prepolymer at the end of the extruder, so as to prepare elastic fibers. However, since it takes about 2 hours for the prepolymer to be prepared, this is a disadvantage, in that it takes too long. In addition, the staying for 6 min in the twin-axis extruder at 250-260 ° C makes the thermoplastic poiyurethane resins yellowed and partially causes side- reactions, producing gelled particles (small mass, fish eyes) inevitably. As indicated in the supra documents, the gelled particles are caught in a spinning filter to increase the pack pressure and the gelled particles escaped from a nozzle come to act as a factor of shortening fibers by inhibiting the elastic fibers' being extended upon winding around a bobbin, thereby making it impossible to produce the elastic fibers continuously. Although the supra patents suggest various reaction conditions to reduce the gelled particles, some are always produced. Upon crosslink spinning with the aid of the static mixer, a thermoplastic poiyurethane resin is first melted in an extruder and then, added with a prepolymer in the static mixer to execute a crosslinking reaction. It is written that the best result was obtained when the prepolymer was added at an amount of 15 weight %. As described above, the melt-spinning related techniques which have been developed, thus far, can be divided largely into two categories: optimal crystallization of polyol so as to induce a maximal phase separation between hard segments and soft segments and use of a crosslinking prepolymer to induce allophanate crosslinks upon spinning. The elastic fibers prepared from these methods are, however, found to be inferior in thermal resistance and elastic recovery to those prepared from conventional wet spinning or dry spinning techniques. Disclosure of Invention With this background in mind, the present inventors have developed polyurethane-based elastic fibers in consideration of their various advantages and disadvantages. For this, the research and development was proceeded in the direction of excluding the basic limits and eliminating the problems which might be produced upon the exclusion. The first consideration factor for the research and development is to use no solvents. Use of solvents in preparing elastic fibers is followed by the production of environmental pollution, such as water and air pollution, for the solution of which an additional pollution- preventive facility is required, increasing the cost of the elastic fibers. In addition, the used solvents, if remaining in the elastic fibers, always have a high possibility to harmfully affect the body. Thus, wet spinning, dry spinning and chemical spinning techniques, which all use solvents in the polymerization, are excluded. The production cost of elastic fibers was also taken into account. Price is one of the most important factors to overwhelmingly spread elastic fibers. In the future, it is thought that clothing will be developed in such a way that it provides a more comfortable feeling for the users. Elastic fiber fabrics are the most suitable for this purpose. In order for the elastic fiber fabrics to be popularized, therefore, the production cost of elastic fibers must be exceptionally reduced from the current level . The final factor of which account was taken is amount of money invested in making elastic fibers. Conventional dry spinning, wet spinning or chemical spinning techniques require large scales of investment on the account that the spinning process cannot be carried out separately in the aspect of time and space. For these three accounts, there was reached a conclusion that melt spinning techniques are most suitable for making elastic fibers. The melt spinning techniques in current use, if able to meet the above accounts, produce elastic fibers insufficient in physical properties, so that they do not prevail over previous techniques. Intensive and thorough research on elastic fibers, repeated by the present inventors, resulted in the finding that a poiyurethane urea resin is allowed to show excellent physical properties including thermal resistance and elastic recovery, depending on the chemical structure of its hard segment. Therefore, it is an object of the present invention to provide a novel thermoplastic poiyurethane resin which can be melt-spun to produce elastic fibers of high thermal resistance and elastic recovery. It is another object of the present invention to provide a method for preparing such a thermal poiyurethane resi . In accordance with an aspect of the present invention, there is provided a polyurethaneurea resin, consisting of a polymer represented by the following chemical formula I: [A-O- (0) C-NH-D-NH-C (0) -NH-D-NH-C (0) -0] n [I] wherein A represents an organopolyol residue having a number average molecular weight of approximately 500 to 5,000 and a weight average molecular weight/number average molecular weight {M W /M N ) of 1.5 to 2.5 with the number of functional groups ranging from 1.8 to 2.2, D represents an aromatic organodiisocyanate residue ranging, in the number of functional groups, from 1.8 to 2.2, and n represents the number of repeat units. In accordance with another aspect of the present invention, there is provided a method for preparing a polyurethaneurea resin having the chemical formula I, comprising the steps of: reacting an organopolyol with an excess of an aromatic organodiisocyanate to give a prepolymer, said organopolyol having a number average molecular weight of approximately 500 to 5,000 and a weight average molecular weight/number average molecular weight {M W /M N ) of 1.5 to 2.5 with the number of functional groups ranging from 1.8 to 2.2, said aromatic organodiisocyanate ranging, in the number of functional groups, from 1.8 to 2.2; subjecting a part of diisocyanate groups of the prepolymer to aminization; reacting two molecules between the residual isocyanate group and newly-obtained amine group to produce a urea functional group via which the two molecules of the prepolymer are linearly joined; and polymerizing the urea containing bi-prepolymers . Now, the invention will be described more detail. The present invention pertains to a polyurethane-urea resin having the repeat unit of the following chemical formula I : [A-O- (0) C-NH-D-NH-C (0) -NH-D-NH-C (0) -0] N [I] wherein A represents an organopolyol residue and D represents an aromatic organodiisocyanate residue. As seen in the formula, the repeat unit is characterized in that two aromatic organodiisocyanate groups are connected to each other via a urea linkage with a urethane bridge between an aromatic organodiisocyanate group and an organopolyol group. The aromatic organodiisocyanate residue D ranges, in the number of functional groups, from 1.8 to 2.2. Preferably, the aromatic organoisocyanate has a number average molecular weight of 500 or less. Illustrative, but not limitative, examples of the aromatic organodiisocyanate include methane diphenyl-4 , 4' -isocyanate (MDI) and p- phenylenediisocyanate . The organopolyol residue A has a number average molecular weight of about 500 to 5,000 and preferably 1,000 to 2,000. With the number of functional groups of 1.8 to 2.2, the organopolyol residue A has a weight average molecular weight/number average molecular weight ratio (M w /M w ) of 1.5 to 2.5 and preferably 1.8 to 2.2 and is selected from aliphatic polyester polyols, aliphatic polyetherpolyols, aliphatic polycaprolactone polyols, aliphatic carbonate polyols and aliphatic siloxane polyols. Illustrative, but not limitative, examples of the organopolyol include polyether polyols, such as polytetramethylene ether glycol, polypropylene glycol and polyethylene propylene glycol; polyester polyols, such as polyethylene adipate, polyethylene butylene adipate, polyhexylene adipate, polybutylene hexylene adipate and poly-3-methyl-pentylene adipate; polycaprolactone polyols; hexamethylene carbonate polyols; and dimethyl siloxane polyols . In the resin consisting of the repeat unit of the chemical formula I, the organopolyol A is a soft segment while the remaining, that is, -0- (0) C-NH-D-NH-C (0) -NH-D-NH- C(0)-0-, acts as a hard segment. On the other hand, a conventional elastic resin for dry and wet spinning has a hard segment represented by the following chemical formula II: -0- (0) C-NH-D-NH-C (0) -NH-Ri-NH-C (0) -NH-D-NH-C (0) -0 [II] wherein, D is an organodiisocyanate and R x is an aliphatic chain. For a conventional elastic resin for melt spinning, its hard segment is represented by the following chemical formula III: -0- (0) C-NH-D-NH-C (0) -0-R 2 -0-C (0) -NH-D-NH-C (0) -0 [III] wherein, D is an organodiisocyanate and R 2 is an aliphatic chain. Between two isocyanate groups, as seen in the formulas, are two urea linkages in the hard segment of the conventional elastic resin for dry spinning and wet spinning and two urethane linkages in the hard segment of the conventional elastic resin for melt spinning. This is attributed to the fact that the elastic resin for dry spinning or wet spinning is synthesized by using aliphatic diamines as a chain coupling agent and the elastic resin for melt spinning is synthesized by using aliphatic diols or aromatic diols. When comparing the chemical formulas I, II and III, the hard segment in the elastic resin of the present invention is revealed to be quite different from those in the conventional elastic resins. Only one urea linkage resides between two aromatic organoisocyanate groups. Because an aromatic benzene ring is linked directly to the urea group in the hard segment of the elastic resin of the present invention, this structural property allows the hard segment of the chemical formula I to be far superior in a packing aspect to the conventional hard segments of the chemical formulas II and III, bringing a great improvement in thermal resistance and elastic recovery. Also, the present invention pertains to a method for preparing such an elastic resin for melt spinning. The method according to the present invention comprises (a) a prepolymer production process, (b) an aminization process, (c) a urea functional group production process, and (d) a polymer production process. The prepolymer production process may be carried out in a continuous type or a batch type. In a batch type process, for example, a selected equivalent ratio of an organopolyol to an aromatic organodiisocyanate is fed in a reactor equipped with a stirrer and a temperature controller and then, subjected to reaction for 2-3 hours at a temperature of 80-120°C and preferably 90-100°C. In an example of a continuous type process, an organopolyol and an aromatic organodiisocyanate are homogeneously mixed by use of a pin-type mixing head while being continuously fed at a constant ratio with the aid of a facility equipped with a gauging means and the resulting mixture is passed through a high-speed pin mixer type reactor to yield prepolymer continuously. The mixture stays at the high-speed pin mixer for 2 to 30 min and preferably 3 to 10 min. In the prepolymer production process, the organopolyol and the aromatic organodiisocyanate are preferably fed at the equivalent ratio represented by the following equation 1: , _ equivalents of aromatic organodiisocyanates n [1. 1.5 ≤ < 2.5 equivalent of organio polyols The range of the equivalent ratio of aromatic organodiisocyanates to organopolyols, is suitable to provide the physical properties elastic fibers must have. In this range, the elastic fibers range, in Shore hardness, from 65A to 85A and, in elongation ratio, from 550% to 900%. For example, if the equivalent ratio is below 1.5, there is obtained a polymer which is good in elongation ratio, but poor in thermal resistance. On the other hand, if the equivalent ratio exceeds 2.5, the polymer obtained shows good thermal resistance, but insufficient elongation ratio. An optimal equivalent ratio may be a little modulated depending on the molecular weight of the aromatic organodiisocyanate and organopolyol used. The prepolymer thus obtained, when adding H 2 0, undergoes a series of an amine functional grup forming reaction and a urea linkage reaction to yield a polymer. It is preferred that pure water or distilled water, free of impurities, is used in the amine functional group forming reaction. However, if particularly controlled physical properties are needed, an additional chain coupling agent may be added, in combination with H 2 0. Available chain coupling agents are those which have a molecular weight of 400 or less with the number of hydroxy functional groups being 1.8-2.2. Poorer thermal resistance and elastic recovery are provided when the chain coupling agent is used, in combination, than when H 2 0 is used alone. Representative examples of the diol-type chain coupling agents include ethylene glycol, 1, -butanediol, propylene glycol, 1,6-hexane diol, 3-methyl-l, 5-pentane diol. Preferably, the prepolymer and H 2 0 are added at an equivalent ratio represented by the following equation 2: i σ NCO Equivalent of Prepolymers _ 0 i 2 ' - 1. o ≤ ≤ 2.2 Equivalent of H 2 O For example, if the equivalent ratio of the prepolymer to H 2 0 is below 1.8, the equivalent of the amine produced is more than that of the NCO remaining, so that polymers of high molecular weights cannot be obtained. On the other hand, if the equivalent ration is over 2.2, the equivalent of the NCO remaining is more than that of the amine produced, so that many crosslinks attributable to allophanate or biuret linkages are produced, losing the thermoplastic properties. Experiment data showed that, when the equivalent ratio of the NCO equivalent to H 2 0 equivalent is 2.0, the longest linear chains of high molecular weights can be produced. The polymer production process may be carried out in a continuous or a batch type. In a batch type process, the prepolymer is added with a predetermined amount of H 2 0 with stirring. The stirring is not ceased until C0 2 does not break. When the reaction increases in viscosity as the bubbles are removed, the reaction is aged on a tray in a hot air oven. The hot air oven is preferably heated at 120-170°C. It is preferred that the oven uses heated nitrogen rather than oxygen-containing air. Oxygen is apt to cause the polymer to yellow during the aging. The aged polymer is broken down into flakes which are then pelletized by an extruder. In a continuous type process, the prepolymer and H 2 0 are mixed instantaneously at a high-speed mixing head and reacted at a screw-mounted multi-axial reactive extruder to produce carbon dioxide and a product containing urea-bonds. Continuously, the carbon dioxide is removed through a vacuum vent and the product is extruded and pelletized. In order to better understand the method according to the present invention, a synthesis reaction mechanism of a poiyurethane urea will be represented in chemical reaction formulas using a bifunctional aromatic organodiisocyanate and a bifunctional polyol. (A) Prepolymer Production Reaction 20CN-D-NCO + HO-A-OH → OCN-D-NH-C (0) -0-A-O- (0) C-NH-D-NCO diisocyanate polyol prepolymer (B) Aminization OCN-D-NH-C (0) -0-A-O- (0) C-NH-D-NCO + H 2 0 → OCN-D-NH-C (0) -0-A-O- (0) C-NH-D-NHC00H → OCN-D-NH-C (0) -0-A-O- (0)C-NH-D-NH 2 + C0 2 ( t ) (C) Urea functional group formation 20CN-D-NH-C (0) -0-A-O- (0) C-NH-D-NH 2 → OCN-D-NH-C (0) -0-A-O- (0) C-NH-D-NH-C (0) -NH-D-NH-C (0) -0-A- 0- (0)C-NH-D-NH 2 (D) Polymerization n/20CN-D-NH-C (0) -0-A-O- (0) C-NH-D-NH-C (0) -NH-D-NH-C (0) -0-A- 0- (0)C-NH-D-NH 2 → [A-O- (0) C-NH-D-NH-C (0) -NH-D-NH-C (0)-0] n First, a mixture of a bifunctional aromatic organoisocyanate and a bifunctional organopolyol (molar ratio 2:1) is reacted to give a prepolymer having an NCO group at each of the opposite ends. An equivalent of water is added per two equivalents of NCO of the prepolymer to convert either of the two terminal NCO groups of the prepolymer into an amine group. Two molecules of the prepolymer which have an amine group at one end and an NCO group at the other end, are reacted with each other to give an adduct which is joined via a urea linkage. That is, the amine group of one prepolymer is reacted to the NCO group of the other prepolymer to form a urea linkage which comes to connect two aromatic organoisocyanates, linearly. In consequence, there are synthesized straight urethaneurea resins of high molecular weight, which are of high thermal resistance and elastic recovery. The polyurethaneurea resins prepared according to the method of the present invention have a melt index (MI) of 5-30 g/10 min, a softening point of 140-160°C, a tensile strength of 280-400 kg/cm 2 , an elongation rate of 600- 800 %, a 300% immediate elastic recovery of 92-94 %, and a 500% immediate elastic recovery of 91-93 %. These physical properties were measured as follows: • Melt Index (MI) : After being dried in a vacuum oven at 120°C for 5 hours, a sample was measured for MI at 260°C under a load of 5,000 g. • Softening Point : Two specimens, whose preparation will be described below, were cut in a dimension of 10mm x 10 mm and piled up before they were put in a softening point measuring machine. The temperature at which a needle with a load of 1,000 g penetrated the samples to a depth of 1 mm, was determined as a softening point for the sample . • Tensile Strength, Elongation Rate, 300% Immediate Elastic Recovery, and 500% Immediate Elastic Recovery : The same samples as those used for the softening point were cut with an ASTM D412 die and measured for the physical properties by a universal test machine (UTM) . The specimens used for the measurement of physical properties were prepared using a hot press. In the past, the preparation technique employing a hot press was very poor, so that the specimens obtained were not qualified for the physical property test. Now, a Teflon-coated woven fabric technique enables the hot press to be useful to prepare qualified specimens. The hot press is very convenient m that specimens can be prepared in a short time and from a small quantity of materials. A commonly available hot press is designed to be capable of heating and cooling. Pre-works for specimen preparation include the adjustment of the temperature of heating plates into a range of 220-240 ° C and the weighing of materials at 180 g. A three-story iron plate structure is provided. On the bottom is placed a plate which is covered with a Teflon sheet, followed by putting a specimen frame with a dimension of 250mm x 250mm x 2mm on the Teflon sheet. Next, the weighed material is poured the frame and evenly spread thereover, after which, like a lid, a plate covered with a Teflon sheet is overlaid on the frame. The resulting structure is inserted between the heating plates which are, then, pressurized for 1 mm at a pressure of 10 tons and for 2 mm at a pressure of 30 tons. The structure is moved onto a cooling plate and pressurized for 2 mm at a pressure of 30 tons with cooling. After opening the lid, the structure is disassembled to obtain a specimen with a weight of around 160 g, 2.1 mm thick. The obtained specimen is aged for 12 hours at 120°C order to prepare itself for the physical property test. Because the polymers prepared according to the present invention are of thermoplasticity, they can be molded by an extruder. One of the factors which determine the compression moldability of a material is the ability of the material to be constantly fed upon extruding. A smooth operation constantly feeding a material means that the material has a thermoplasticity sufficient to guarantee a uniform molten state and a constant output rate. The compression moldability can be determined by plotting the Tq change of an extruder with time. Evaluation for the compression moldability of the thermoplastic polyurethaneurea resins prepared according to the present invention, was done by use of an extruder, such as that sold by Brabender, identified as "Plasticoder", showing that the Tq was maintained at 35-40 under the condition of an RPM of 50 and Barrel temperatures of 230-250-260-240 ° C . The resins were constantly extruded. Observation on the appearance of the rod-shaped product extruded through a die allowed the knowledge of the product's having a clear surface free of gel. A better understanding of the present invention may be obtained in light of the following examples which are set forth to illustrate, but are not to be construed to limit the present invention. Modes for Carrying Out the Invention EXAMPLE I Polybutylene hexylene adipate (PBHA, Mw=l,000), a kind of polyol, was dried at 120°C for 5 hours in a vacuum oven to an extent of a water content of 150 ppm or less to give a starting material for a prepolymer. Methanediphenyl- , ' -diisocyanate (MDI) was molten at 45°C in an oven. To a round-bottomed cylindrical reactor equipped with a controlable stirrer, which was set in an oil bath maintained at 90 ° C, was fed a mixture of the diisocyanate and the polyol (equivalent ratio, diisocyanate :polyol=l .80 : 1.00) . They were reacted for 5 min or more in the presence of 10-100 ppm of an organotin catalyst, such as T-10, while stirring at 1,000 rpm, to produce a prepolymer. The reaction progress for the prepolymer could be detected by monitoring the change of the current loaded on the stirrer motor and was found to reach the maximal point at 2 mm after the stirring. To provide an amine functional group to the prepolymer, H 2 0 was added at an equivalent of 0.80 with stirring. This reaction was exothermic with C0 2 occurring. As the stirring continued, the bubbles were removed and an exceptional increase of viscosity resulted. When a polymer synthesized was wound around the stirrer, the polymer was spread flat on a tray covered with a releasable sheet. It was aged for 5 hours at 120 ° C in an hot air oven. Specimens for the physical property test were made from the aged polymer using the hot press, as described above. The physical properties tested are given m Table 1, below. EXAMPLE II The procedure of Example I was repeated using an equivalent ratio of 1.80:1.0:0.80 of MDI : PBHA-1500 : H 2 0. The physical properties of the polymer thus obtained are given in Table 1, below. EXAMPLE III The same procedure as that of Example I was repeated, except that polytetramethylene ether glycol (PTMG, Mw=l,000) was used as a polyol and an equivalent ratio of 1.80:1.0:0.80 of MDI : PTMG-1000 : H 2 0 was used. The physical properties of the polymer obtained are given m Table 1, below . EXAMPLE IV The same procedure as that of Example I was repeated, except that polytetramethylene ether glycol (PTMG, Mw=l,500) was used as a polyol and an equivalent ratio of 2.00:1.00:1.00 of MDI : PTMG-1500 : H 2 0 was used. The physical properties of the polymer obtained are given in Table i, below. COMPARATIVE EXAMPLE I To the prepolymer prepared in the same manner as in Example I, butanediol (BD) was added as a chain coupling agent at an amount of 0.80 equivalent with stirring. When a polymer synthesized was wound around the high speed stirrer, the polymer was spread flat on a tray covered with a releasable sheet. It was aged for 5 hours at 120°C in a hot air oven. Specimens for the physical property test were made from the aged polymer using the hot press, as described above. The physical properties of the polymer are given in Table 1, below. COMPARATIVE EXAMPLE II The procedure of Comparative Example I was repeated using an equivalent ratio of 2.00:1.00:1.00 of MDI : PBHA- 1500 :BD. The physical properties of the polymer thus obtained are given in Table 1, below. COMPARATIVE EXAMPLE III The same procedure as that of Comparative Example I was repeated, except that polytetramethylene ether glycol (PTMG, Mw=l,000) was used as a polyol and an equivalent ratio of 1.80:1.0:0.80 of MDI : PTMG-1000 : BD was used. The physical properties of the polymer obtained are given in Table 1, below. EXAMPLE IV The same procedure as that of Example I was repeated, except that polytetramethylene ether glycol (PTMG, Mw=l,500) was used as a polyol and an equivalent ratio of 2.00:1.00:1.00 of MDI : PTMG-1500 : H 2 0 was used. The physical properties of the polymer obtained are given in Table 1, belo . TABLE 1 300% 500% Tensile Elong. Elastic Elastic Hardness Strength Rate Recovery Recovery Softening Examp. (Shore A) (Kg/cm 2 ) (%) (%) (%) Point ( ° C ) I 80 340 750 93.5 91.5 145 II 79 330 780 94.1 92.1 143 III 79 300 740 93.6 91.6 141 IV 78 290 750 94.0 92.3 140 C. I 82 320 710 85.2 72.5 72 C. II 80 310 750 84.6 73.2 75 C. Ill 78 280 720 84.5 74.3 68 C. IV 77 260 740 83.7 73.5 70 Taken together, the data shown in Table 1 demonstrate that the polyurethaneurea resins prepared according to the method of the present invention are far superior in thermal resistance and elastic recovery to those prepared according to conventional methods. These polyurethaneurea resins of the present invention are able to be melt-spun to make useful elastic fibers. The present invention has been described in an illustrative manner, and it is to be understood the terminology used is intended to be in the nature of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Claims: Claims : 1. A polyurethaneurea resin, consisting of a polymer represented by the following chemical formula I: [A-O- (0) C-NH-D-NH-C (0) -NH-D-NH-C (0) -0] n [I] wherein A represents an organopolyol residue having a number average molecular weight of approximately 500 to 5,000 and a weight average molecular weight/number average molecular weight {M W /M N ) of 1.5 to 2.5 with the number of functional groups ranging from 1.8 to 2.2, D represents an aromatic organodiisocyanate residue ranging, in the number of functional groups, from 1.8 to 2.2, and n represents the number of repeat units. 2. A polyurethaneurea resin as set forth in claim 1, wherein the aromatic organodiisocyanate residue D has a number average molecular weight of 500 or less of aromatic diisocyanate . 3. A polyurethaneurea resin as set forth in claim 1, wherein the aromatic organodiisocyanate residue D is methanediphenyle-4 , 4 ' -diisocyanate residue . 4. A polyurethaneurea resin as set forth in claim 1, wherein the organopolyol residue A is selected from the group consisting of aliphatic polyester polyols, aliphatic polyether polyols, aliphatic polycaprolactone polyols, aliphatic carbonate polyols, and aliphatic siloxane polyols . 5. A polyurethaneurea resin as set forth in claim 4, wherein the organopolyol A has a number average molecular weight of approximately 1,000 to 2,000 and a weight average molecular weight/number average molecular weight {M W /M N ) of 1.8 to 2.2. 6. A method for preparing a polyurethaneurea resin having the following chemical formula I: [A-O- (0) C-NH-D-NH-C (0) -NH-D-NH-C (O) -0] n [I] wherein A represents an organopolyol residue having a number average molecular weight of approximately 500 to 5,000 and a weight average molecular weight/number average molecular weight (M W /M N ) of 1.5 to 2.5 with the number of functional groups ranging from 1.8 to 2.2, D represents an aromatic organodiisocyanate residue ranging, in the number of functional groups, from 1.8 to 2.2, and n represents the number of repeat units, comprising the steps of: (A) reacting an organopolyol with an excess of an organodiisocyanate to give a prepolymer, said organopolyol having a number average molecular weight of approximately 500 to 5,000 and a weight average molecular weight/number average molecular weight {M W /M N ) of 1.5 to 2.5 with the number of functional groups ranging from 1.8 to 2.2, said aromatic organodiisocyanate ranging, in the number of functional groups, from 1.8 to 2.2; (B) subjecting a part of diisocyanate groups of the prepolymer to aminization; (C) reacting two molecules between the residual isocyanate group and newly-obtained amine group to produce a urea functional group via which the two molecules of the prepolymer are linearly joined; and (D) polymerizing the urea containing bi-prepolymers . 7. A method as set forth in claim 6, wherein the step (A) is carried out with an equivalent ratio of the aromatic organodiisocyanate to the organopolyol ranging from 1.5 to 2.5. 8. A method as set forth in claim 6, wherein the step (B) is carried out with an equivalent ratio of the NCO group of the prepolymer to H 2 0 ranging from 1.8 to 2.2. 9. A method as set forth in claim 6, wherein the aromatic organodiisocyanate has a number average molecular weight of 500 or less of aromatic diisocyanates . 10. A method as set forth in claim 6, wherein the organopolyol is selected from the group consisting of aliphatic polyester polyols, aliphatic polyether polyols, aliphatic polycaprolactone polyols, aliphatic carbonate polyols, and aliphatic siloxane polyols. 11. A method as set forth in claim 10, wherein the organopolyol has a number average molecular weight of approximately 1,000 to 2,000 and a weight average molecular weight/number average molecular weight {M W /M N ) of 1.8 to 2.2.

Inventors: AHN PYEONNO, LEE DONGKYUN, AHN, PYEONNO, LEE, DONGKYUN
Applicants: SK CHEMICALS CO LTD, SK CHEMICALS CO., LTD.
Application year: 1999
Main classification: D01F6
IPC codes: C08G18, D01F6