BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a thermoplastic polyurethane (hereinafter abbreviated as TPU) containing a dicarboxyphenyl polyester structure or 10-(2,3-dicarboxypropyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide polyester structure, and the glass transition temperature of the TPU is between an ambient temperature and normal body temperature; besides, the invention also relates to a polyester polyol containing 10-(2,3-dicarboxypropyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide polyester structure, which is used to prepare the above TPU. The invention also relates to a solvent-free hot adhesive, nonwoven fabric and article made of the TPU.

2. Description of the Prior Arts

Thermoplastic polyurethanes are widely used in the commodity sectors, such as furniture, footwear, textiles, household goods, automobiles and outdoors equipment. They have a structure of a macromolecular backbone containing a urethane group (—NH—CO—O—), which is a typical multi-block linear polymer, and are normally prepared by the addition of a diisocyanate, a polyol and a diol (hereinafter also referred to as a chain extender). The polyol segment in the polyurethane structure, also known as the soft segment, has a soft, long chain that brings a good elongation property to the TPU, and the segment formed by the addition of diisocyanate and diol is called a hard segment. The hard segment is liable to form a hydrogen bond, which is beneficial to produce an ordered structure (a crystalline phase) to form physical crosslinks between molecules. The material structure between the soft segment and the hard segment is gradually melted in the heated environment, so that the physical crosslinking between the molecules is reduced, and the polymer will be softened and plasticized, and usually processed by injection molding, extrusion molding, melt blowing, calendering, etc., and then a molded article is obtained after cooling and solidifying.

In the prior art, aliphatic polyester polyol or aliphatic polyether polyol is commonly used as soft segment materials in the TPU. The soft segment accounts for the weight of TPU and the molecular weight of the selected polyester polyol or polyether polyol affects the glass transition temperature (hereinafter abbreviated as Tg) and the crystallization temperature (hereinafter abbreviated as Tc) of the TPU. For example, when the weight ratio of the soft segment and the molecular weight of the polyester polyol increase, the Tg of the obtained TPU tends to be lower, as well as the crystallinity, and then the TPU will be softer; on the other hand, if the hard segment is used in a high proportion, that is, using more chain extender, the crystallinity of the polymer will be increased, thereby improving hardness and modulus of the material, and the Tg will also increase. The Tg of a common commercial TPU product is usually below −10° C., even below −40° C. However, if the Tc and the Tg are low, when PTU is used as a hot melt adhesive, it usually takes a longer molding time after melt blowing or forming extrusion film, and is easy to stick to each other during rolling, and therefore requires collecting by a release paper and release cloth. The process is complicated and costly; besides, when TPU is directly used as a non-woven fabric, a film material, or as a hot-melt adhesive to a fabric, TPU is often cohesively shrunk because of a slow setting time, leading to a fabric wrinkle.

The invention aims to prepare a TPU by using a polyester polyol as soft segment material, and the soft segment contains at least a dicarboxyphenyl polyester structure or a 10-(2,3-dicarboxypropyl)-9,10-dihydro-9-oxa-10-phenanthrene-10-oxide (hereinafter referred to as a DOPO-ITA) polyester structure. The existent technology is discussed below.

For example, German Patent DE2816100C2 discloses a flame retardant, a polyester polyols obtained by adding DOPO or a derivative thereof and itaconic acid and then condensated with a polyol, which has a molecular weight of 1,000 to 20,000 g/mole and a phosphorus content of 5.3 to 8.5 wt %, which is a glassy crystal at normal temperature. The specification mentions that it can be added as a flame retardant to thermoplastic resins such as polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), and polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene copolymer (ABS), etc., to improve its flame retardancy. It is mentioned that the molar ratio of the DOPO-ITA to ethylene glycol is made 1 to 3, the excess ethylene glycol is removed by heating under reduced pressure after refluxing, then nitrogen and germanium oxide (GeO2) is added as a catalyst, and the temperature is raised to 230° C. to obtain a polyester polyol containing a DOPO-ITA structure, CAS: 68664-61-9, having a chemical formula of (C17H15O6P.C2H6O2)x, a Tg of about 60° C. and an average molecular weight (Mn) of 4500. The DOPO-containing polyester polyol has high softening temperature and high viscosity, so it is not appropriate as a soft segment raw material for the TPU of the present invention.

U.S. Pat. No. 4,529,744 discloses an aromatic polyester polyol, which is a dicarboxyphenyl polyester polyol. The specification also discloses its compositions, preparing methods and applications for PU foaming. At present, the dicarboxyphenyl polyester polyol has been commercialized, which contributes to foaming and solidifying when applied to solvent polyurethane (hereinafter abbreviated as PU).

U.S. Pat. No. 5,128,197 discloses a fabric of shape memory polymer in which fibers are made of a polyurethane elastomer having a shape memory function. The specification mentions that an elastomer would undergo an elastic modulus change near the glass transition point of about 40° C., which becomes rubbery at a temperature above Tg, and becomes glass at a temperature below Tg. The elastomer is memorized into a basic shape after the fabric is deformed at a temperature below Tg, so the shape of the fabric can be changed and recovered by heating to a specific temperature. The specification suggests aromatic glycol used as a chain extender, such as bis(2-hydroxyethyl)hydroquinone, has a significant effect on improving Tg, and also suggests the use of aromatic polyglycols, for example, bisphenol A and propylene oxide copolymers are used as soft segments, besides, aromatic glycol, for example, bisphenol A and propylene oxide copolymers can be used as soft segments, but the specification also mentions that fabrics of high Tg are not preferred to contact the skin due to their rigidity.

Taiwan Patent No. 200413459 provides a method for preparing a water-reducible phosphorus-containing polymer precursor, which uses a raw material for a polyacrylic acid-urethane prepolymer to produce the water-reducible phosphorus-containing polymer precursor and coating formula applied in resisting corrosion and retarding flame. The specification refers to a polyester glycol containing DOPO-ITA structure, including CAS 455333-14-9, the chemical formula is (C17H15O6P.C6H14O2)x, and CAS 455333-15-0, and the chemical formula is (C17H15O6H10O4.C6H14O2)x. The preparing method provided by the specification is that 2-methylidenebutanedioic acid (hereinafter also referred to as itaconic acid), 1,6-hexanedioic acid, DOPO, antioxidant 1,4-dihydroxybenzene and tin catalyst at different ratios were heated at 110° C. for 4 hours under nitrogen, then heated to 180° C. until no water was distilled, removing residual water by heating for 8 hours under vacuum, until all DOPO was traced by31P-NMR (nuclear magnetic resonance) to add the unsaturated bond of itaconic acid. According to the embodiments, its acid value is more than 5 mg of potassium hydroxide per gram (mg KOH/g). The acid value of the polyester polyol containing the DOPO-ITA structure obtained by this method is too high to be a soft segment raw material of the TPU.

China patent CN101743266A provides a polyester polyol with an average molecular weight of more than 20,000 made from DOPO, which is a glassy polymer at normal temperature. It can be applied to polyamide fibers (such as PA6, PA12 and PA66) for melt spinning and polyester fiber (PET), which can improve the flame retardancy due to its good solubility, but it cannot be used in polyurethane (PU). It is mentioned in the specification that after DOPO-ITA and excess ethylene glycol are refluxed to remove water, the excess ethylene glycol is removed by heating and decompression, and then inject nitrogen and add a trace amount of germanium oxide (GeO2) and trimethylolpropane dissolved in ethylene glycol, a polyester polyol containing DOPO-ITA structure is obtained after the temperature is increased to 260° C., whose softening point is about 100° C. to 130° C. and the Tg is higher than 60° C., and therefore it is not suitable as a soft segment raw material for the TPU

Further, China Patent CN101914854 provides a solvent-type waterproof and moisture permeable polyurethane (PU), which is composed of 18.5% to 19.5% aliphatic polyester polyol, 34.0% to 35% polyether polyol, 7.0% to 8.0% butylene glycol, 26.5% to 29.0% 4,4′-diisocyanate diphenylmethane and various additives, and the ambient temperature higher than the Tg of the polyurethane contributes to improving moisture permeability, which helps the wearer feel comfortable with perspiration. When the cold ambient temperature is lower than the Tg of the polyurethane, it has a warmth-preservation function under low temperature.

Japan Patent JPS53118497A discloses a solvent-type polyurethane, the examples in the specification provide a method for preparing a polyester polyol containing a DOPO-ITA structure, wherein DOPO, itaconic acid and ethylene glycol are mixed and heated from 120° C. to 180° C. (heating rate: 20° C. per hour), water is distilled by vacuum at 200° C., excess ethylene glycol is added to adjust the OH value to 106.7 mg KOH/g, Acid value to 2.5 mg KOH/g, and then polymerized with diphenylmethane isocyanate (also referred to as MDI) in dimethylforamide (DMF) to obtain a polyurethane with flame retardant function (CAS 69068-45-7). The polyester polyol obtained by adjusting the hydroxyl value by excess ethylene glycol by this method is difficult to control the ratio of soft segments to hard segments of the polyurethane.

Taiwan Patent No. I614306B discloses an adhesive composition of a solvent-type polyurethane and an epoxy resin, which is applied to the printed circuit board industry. The specification discloses a polyester polyol composition prepared by two or more polycarboxylic acids such as DOPO-ITA, phthalic acid and two or more kinds of polyols with lower molecular weight, which has a number average molecular weight (Mn) of 8,000 to 16,000 and a Tg higher than room temperature, and is further reacted with a chain extender and an isocyanate dissolved in one or more solvents to form a polyurethane having a specific high acid value range whose Tg is between −20° C. to 100° C. The specification further reveals the lower limit of the Tg is preferably −10° C., more preferably 0° C., while the upper limit is preferably 80° C., more preferably 60° C. The polyester polyol containing the DOPO-ITA structure mentioned above has high molecular weight, high viscosity and high acid value, so it is not suitable for the soft segment raw material of the TPU.

China patent CN104927038A provides a solvent-free one-pot method, in which DOPO and small molecule polyhydric alcohol are put in a reactor; the air is first purged by nitrogen, heated to 90° C. until the DOPO is completely dissolved, and then cooled to 70 to 80° C. Add an unsaturated dibasic acid (such as itaconic acid) or anhydride to react for 4 to 6 hours, add dibasic acid and antioxidant (triphenylphosphorus) at 100 to 140° C. and carry out the reaction for 3 to 12 hours, and then the temperature is gradually increased to 180° C. for 2 to 6 hours, the temperature is further increased to 200° C. for 3 to 4 hours, and finally an organometallic catalyst (for example, titanate) is added and the water is removed by vacuum for 3 to 4 hours. A polyester polyol containing DOPO-ITA having an acid value of less than 5 mg KOH/g is obtained, but the acid value is too high to be a soft segment raw material of the TPU.

Viewing the current public literature and commercial products, a TPU and article thereof whose Tg is between an ambient temperature and normal body temperature have not been seen, we are attracted to develop and realize one as fabrics, shoes, accessories, toys, sporting goods and daily necessities.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a thermoplastic polyurethane (TPU) and article thereof, which becomes rigid and stiff at ambient temperature and soft and elastic at normal body temperature, endowing some new tactility, fun and functions when applied to the textiles contacted with the human body (such as underwear, hats, label clothes, curtains, etc.), shoes, decorations (such as watchbands, wrist straps), toys, sporting goods and daily necessities.

The inventors have deliberately studied to achieve the aforementioned objective, and provide a TPU having a Tg between ambient temperature and normal body temperature, wherein the TPU contains a dicarboxyphenyl polyester structure represented by Formula 1 or a DOPO-ITA polyester structure represented by Formula 2; the dicarboxyphenyl polyester represented by Formula 1 and the DOPO-ITA polyester structure represented by Formula 2 each have an average molecular weight ranging from 700 to 2500 g/mole, more preferably, 1000 to 2000 g/mole;



in Formula 1, R is C2 to C8 alkylene group or CH2CH2OCH2CH2;



in Formula 2, R is C2 to C8 alkylene group or CH2CH2OCH2CH2.

The thermoplastic polyurethane contains a molar percentage of the dicarboxyphenyl polyester structure in the thermoplastic polyurethane ranging from 6% to 25%.

The thermoplastic polyurethane contains a molar percentage of the DOPO-ITA polyester structure in the thermoplastic polyurethane ranging from 5% to 20%.

Further, a weight percentage of a soft segment in the thermoplastic polyurethane ranges from 60% to 80%.

In the present invention, the ambient temperature refers to the temperature most suitable for human life, which is between 10° C. and 30° C.; and the normal body temperature refers to the surface temperature and core temperature of humans and higher mammals, which is between 30° C. and 40° C.

Moreover, the Tg of the thermoplastic polyurethane is between the ambient temperature and normal body temperature, that is, between 10° C. and 40° C., preferably between 15° C. and 28° C.

Moreover, the thermoplastic polyurethane of the present invention has a function of hot melt adhesive, and the softening point of TPU is between 50° C. and 100° C., preferably between 60° C. and 85° C.

The present invention further provides a solvent-free hot melt adhesive prepared by using the above TPU.

The present invention further provides a nonwoven fabric prepared by using the above TPU.

The present invention further provides an article produced by using the above TPU. The article can be textile, shoe material, decoration, toy, sporting goods and daily necessity.

In addition, the present invention provides a polyester polyol for producing the above TPU, wherein the TPU contains DOPO-ITA polyester structure represented by Formula 2, a molar percentage of the DOPO-ITA polyester structure contained in the polyester polyol in the polyester polyol ranges from 30% to 70%, and the average molecular weight (Mn) of the polyester structure ranges from 700 to 2500 g/mole.



The polyester polyol containing DOPO-ITA polyester structure represented by the Formula 2 has an OH value between 160.3 and 44.8 mg of potassium hydroxide per gram (hereinafter expressed in mg KOH/g).

The dicarboxylic acid in the above DOPO-ITA polyester structure is an addition of itaconic acid and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), or an addition of itaconic acid, one selected from succinic acid or 1,6-adipic acid and DOPO.

The above polyol contained in the above polyester polyol containing DOPO-ITA polyester structure was selected from C2-C8 aliphatic polyol.

The above C2-C8 aliphatic polyol may be ethylene glycol, propylene glycol such as 1,2-propanediol and 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, diethylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,4-cyclohexanediol, 2-ethylhexanediol, 1,8-octane diol or a combination thereof.

The above polyol contained in the above polyester polyol containing DOPO-ITA polyester structure is preferred to be selected from the polyester polyol of DOPO/itaconic acid/1,6-hexanediol (the chemical formula is (C17H15O6P.C6H14O2)x), the polyester polyol of DOPO/itaconic acid/diethylene polyol (the chemical formula is (C17H15O6P.C4H10O3)x), the polyester polyol of DOPO/itaconic acid/adipic acid/hexamethylene glycol (the chemical formula is (C17H15O6P.C6H10O4.C6H14O2)x), the polyester polyol of DOPO/itaconic acid/succinic acid/diethylene glycol (the chemical formula is (C17H15O6P.C4H6O4.C4H10O3)x) represented by the following Formula 3 or a combination thereof;


wherein n ranges from 1 to 10, x ranges from 1 to 10, b ranges from 1 to 6.

The polyester polyol selected from any one or a combination of the polyester polyol represented by the Formula 3 has an acid value less than 1.8 mg KOH/g.

According to the present invention, the TPU of the present invention can be obtained by a method: mixing the polyol composition including a dicarboxyphenyl polyester structure or a DOPO-ITA polyester structure (hereinafter referred to as polyol composition), chain extender and organic diisocyanate and heating them at the molar ratio of 0.95≤organic diisocyanate/(polyol composition+chain extender)≤1.10.

According to the present invention, the TPU having a function of the hot melt adhesive can be obtained by a method: mixing the polyol composition, chain extender and organic diisocyanate at a preferred ratio, that is, the weight ratio of the polyol composition is 60%≤polyol composition/(polyol composition+chain extender+organic diisocyanate)≤80%, and the molar ratio is 0.98≤the organic diisocyanate/(polyol composition+chain extender)≤1.05.

According to the present invention, the polyol composition not only has polyester polyol containing a dicarboxyphenyl polyester structure or DOPO-ITA polyester structure, but also an aliphatic polyol may be optionally combined.

The polyester polyol containing a dicarboxyphenyl polyester structure of the present invention, wherein a dicarboxylic acid phenyl monomer of the polyester polyol is preferably selected from the group of 1,2-phthalic acid, 1,3-phthalic acid, 1, 4-phthalic acid, phthalic anhydride, or the like, a polyol monomer of the polyester polyol is preferably selected from the group consisting of C2-C8 aliphatic diols, including ethylene glycol and propylene glycol such as 1,2-propanediol and 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, diethylene glycol, 1,5-pentanediol and neopentyl glycol, 1,6-hexanediol, 1,4-cyclohexanediol, 2-ethylhexanediol, 1,8-octane diol or a combination thereof.

Preferably, the polyester polyol containing a dicarboxyphenyl polyester structure is a polyester polyol of 1,2-phthalic acid/diethylene glycol (CAS No. 25916-41-0, the chemical formula is (C8H6O4.C4H10O3)x), a polyester polyol of 1,2-phthalic acid/hexanediol (CAS No. 27516-71-8, the chemical formula is (C8H6O4.C6H14O2)x), a polyester polyol of 1,4-phthalic acid/1,6-hexanedioic acid/diethylene glycol (the chemical formula is (C8H6O4.C6H10O4.C6H14O2)x). More preferably, the polyester polyol has an OH value between 160.3 and 56.1 mg KOH/g, a molar average molecular weight ranging from 700 to 2000 g/mol, and an acid value of <1 mg KOH/g.

Further, for the polyester polyol containing DOPO-ITA polyester structure, the dicarboxylic acid thereof is preferably a combination of an addition of itaconic acid and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), succinic acid or 1,6-hexanedioic acid, etc., wherein the ratio of the DOPO-ITA polyester structure relative to the whole of the polyester polyol, in terms of mole percentage, ranges from 30% to 70%, and the glycol monomer is selected from the C2-C8 aliphatic diols, including ethylene glycol, propylene glycol such as 1,2-propylene glycol and 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, diethylene glycol, 1,5-pentanediol and neopentyl glycol, 1,6-hexanediol, 1,4-cyclohexanediol, 2-ethylhexanediol, 1,8-octane diol or a combination thereof.

In the present invention, the aliphatic polyol includes, but is not limited to, polyethylene glycol, modified polyethylene glycol, polypropylene glycol, polytrimethylene ether glycol, polytetramethylene ether glycol (PTMEG), polyhexylene succinate (PHS), polybutylene adipate (PBA), polyethylene butylene adipate (PEBA), polybutylene hexylene adipate (PBHA), polycaprolactone diol, and a combination thereof.

Among them, the PBA having an OH value of 160.3 to 56.1 mg KOH/g, a molecular weight (Mn) of 700 to 2000 g/mol and an acid value of <0.5 mg KOH/g is preferred.

In the present invention, the organic diisocyanate includes, but is not limited to, 4,4′-diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HDI) and a combination thereof. Among them, MDI is preferred.

In the present invention, the chain extender used refers to an aliphatic polyol, including but not limited to a monomer selected from C2 to C8 aliphatic polyol, including ethylene glycol, propylene glycol such as 1, 2-propanediol and 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, diethylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,4-cyclohexanediol, 2-ethylhexanediol, 1,8-octane diol and a combination thereof. Among them, 1,4-butanediol is preferred.

In the present invention, an auxiliary agent may be added in preparation of the TPU, including but not limited to an antioxidant, an UV absorber, a heat-resistant agent, a slip agent, a catalyst, a colorant, and a combination thereof.

The TPU containing the dicarboxyphenyl polyester structure provided can be used as a solvent-free hot melt adhesive, which has good adhesion to the polyester fabric, and more particularly, has excellent hydrolysis resistance. It can be used to develop products that are used for a long time and are often washed.

Further, the TPU containing 10-(2,3-dicarboxypropyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-ITA) can also be used as a solvent-free hot melt adhesive. The phosphorus atom contained in DOPO in its structure makes it intrinsically flame retardant and not migratable, and easily hydrolyze, so it is suitable for flame retardant textiles or easily-handled disposable items.

According to the present invention, a thermoplastic polyurethane having a Tg between the ambient temperature and normal body temperature and a molded article thereof can be provided, and since the Tg is higher than the ambient temperature, the articles thereof are easily-molded, less likely to wrinkle, and visually stiff when displayed or placed. On the other hand, because the Tg is lower than the normal body temperature, the article gives soft and comfortable feel when in contact with the human body. With the above characteristics, it is especially suitable for textiles (such as underwear, hats, label cloths, curtains, etc.), shoes, decorations (such as straps, wristbands, etc.), toys, sporting goods, daily necessities and so on, and thereby providing consumers with a new touch, fun and function.

Further, according to the present invention, a polyester polyol for producing the above TPU may also be provided.

