WO2020160942A1

WO2020160942A1 - Method for producing an insert-molded article

Info

Publication number: WO2020160942A1
Application number: PCT/EP2020/051849
Authority: WO
Inventors: James PEET; William Mcmaster; Randy Fleck
Original assignee: Basf Se
Priority date: 2019-02-06
Filing date: 2020-01-27
Publication date: 2020-08-13

Abstract

The present invention relates to a method for producing an insert molded article and use of the insert molded article for non-pneumatic tires, conveyor belts, casters and pulley type belts.

Description

Method for producing an insert-molded article

Description Field of invention

Background of the invention

Insert-molding is a commonly used fabrication technique. During insert-molding, a pre-molded substrate or metal part is placed into a cavity as an insert. A second material, which is a plastic material, is either injected onto one side of the insert or sometimes in a manner that it completely surrounds the insert.

The choice of the insert and the second material encapsulating the insert determine, to a large extent, the mechanical properties of the shaped product or article obtained via insert-molding. Accordingly, the final application of these shaped products or articles is also dependent on the insert and the second material encapsulating the insert. The following state of the art documents discuss the insert molding technique and the product or article obtained therefrom, for various applications.

US pat. No. 5,800,759 describes an insert molded article for use as front panels or buttons of AV (audio-visual) devices or instrument panels of automobiles and an apparatus and a method for producing the insert molded article.

Another US pat. No. 6,076,258 describes a method for insert molding comprising the steps of assembling an insert to a holder, the holder having a support for the insert; setting the assembled insert and holder inside a metal mold; and casting resin into the metal mold. In particular, the method described here is for producing electrical connectors.

Another US pat. No. 7, 189,920 B2 describes a method for producing an insert-molded article. The insert-molded article described here is an electronic control unit.

Plastic materials having acceptable mechanical properties for use as the second material encapsulating the insert are well known and described in the state of the art. Of particular preference is engineering plastics, certainly for the fact that they provide high mechanical and/or thermal properties in the final product.

Despite the above, the existing state of the art techniques and the products or articles obtained therefrom have severe limitations. One such limitation is the control over flexural properties with improvement in tensile properties. Said otherwise, the existing second material encapsulating the insert, particularly engineering plastics, is incapable of providing a final product or article having very less or no change in the flexural properties with improved tensile properties. Further, the existing techniques are incapable of maintaining the elastomeric properties in the resulting product or article, while providing for acceptable long term properties such as but not limited to creep recovery, stress relaxation and fatigue resistance, thereby rendering them unsuitable for application such as non pneumatic tires, conveyor belts, casters and pulley type belts.

It was, therefore, an object of the presently claimed invention to provide a method for producing an insert-molded article and an insert-molded article obtained therefrom which provides a control over flexural properties with improvement in tensile properties, is capable of maintaining the elastomeric properties while providing for acceptable long term properties such as creep recovery, stress relaxation and fatigue resistance, thereby rendering it suitable for application such as non-pneumatic tires, conveyor belts, casters and pulley type belts.

Summary of the invention

Surprisingly, it has been found that the above object is met by injection molding a thermoplastic polyurethane resin to fill a cavity of a mold in which an insert is provided, as described hereinbelow.

Accordingly, in one aspect, the presently claimed invention is directed to a method for producing an insert-molded article, said method comprising at least the steps of:

(A) providing an insert comprising a first surface into a mold having a cavity with a plurality of surfaces comprising at least one primary surface, wherein at least a portion of the first surface of the insert is in contact with the primary surface, and

(B) injection molding at least one thermoplastic polyurethane resin to fill the cavity in step (A) to obtain the insert molded article,

wherein the thermoplastic polyurethane resin has a shore hardness ranging from a Shore A hardness of 70 to a Shore D hardness of 80 determined according to ASTM D 2240 and a flexural modulus in between 40 MPa to 2000 MPa determined according to ASTM D790, and

wherein the insert molded article has a tensile yield strength of at least 5 MPa determined according to ASTM D412 and a flexural modulus of less than 20% of the flexural modulus of the thermoplastic polyurethane resin.

In another aspect, the presently claimed invention is directed to an insert-molded article as described herein.

In still another aspect, the presently claimed invention is directed to the use of the above insert- molded article for non-pneumatic tires, conveyor belts, casters and pulley type belts.

Detailed description of the invention Before the present compositions and formulations of the invention are described, it is to be understood that this invention is not limited to particular compositions and formulations described, since such compositions and formulation may, of course, vary. It is also to be understood that the terminology used herein is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. It will be appreciated that the terms "comprising", "comprises" and "comprised of" as used herein comprise the terms "consisting of", "consists" and "consists of".

Furthermore, the terms "first", "second", "third" or "(a)", "(b)", "(c)", "(d)" etc. and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. In case the terms "first", "second", "third" or“(A)”,“(B)” and“(C)” or "(a)", "(b)", "(c)", "(d)", "i", "ii" etc. relate to steps of a method or use or assay there is no time or time interval coherence between the steps, that is, the steps may be carried out simultaneously or there may be time intervals of seconds, minutes, hours, days, weeks, months or even years between such steps, unless otherwise indicated in the application as set forth herein above or below.

In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the appended claims, any of the claimed embodiments can be used in any combination. Furthermore, the ranges defined throughout the specification include the end values as well, i.e. a range of 1 to 10 implies that both 1 and 10 are included in the range. For the avoidance of doubt, the applicant shall be entitled to any equivalents according to applicable law.

An aspect of the present invention is directed to a method for producing an insert-molded article, said method comprising at least the steps of:

Fiber material

In an embodiment, the insert comprises a fiber material. The fiber material includes both woven and non-woven fiber material. By the term “woven fiber material”, it is referred to the fiber material obtained by techniques such as weaving or knitting, for example weaving threads of fiber materials. The term “non-woven fiber material” refers to the fiber material bonded together by chemical, mechanical, heat or solvent treatment techniques. Suitable techniques for obtaining the non-woven fiber material are well known to the person skilled in the art. In one embodiment, the fiber material is non-woven fiber material.

In another embodiment, suitable fiber material is selected from metal fiber, metalized inorganic fiber, metalized synthetic fiber, glass fiber, polyester fiber, polyamide fiber, polyvinyl alcohol fiber, aramid fiber, graphite fiber, carbon fiber, ceramic fiber, mineral fiber, basalt fiber, inorganic fiber, aramid fiber, kenaf fiber, jute fiber, flax fiber, hemp fiber, cellulosic fiber, sisal fiber and coir fiber.

In one embodiment, the fiber material is selected from metal fiber, metalized inorganic fiber, metalized synthetic fiber, glass fiber, polyester fiber, polyamide fiber, polyvinyl alcohol fiber, aramid fiber, graphite fiber, carbon fiber, ceramic fiber, mineral fiber, basalt fiber, inorganic fiber, aramid fiber, kenaf fiber, jute fiber and flax fiber.

In other embodiment, the fiber material is selected from glass fiber, polyester fiber, polyamide fiber, polyvinyl alcohol fiber, aramid fiber, graphite fiber, carbon fiber, ceramic fiber, mineral fiber, basalt fiber and inorganic fiber. In still other embodiment, it is selected from polyester fiber, polyamide fiber, polyvinyl alcohol fiber, aramid fiber, graphite fiber and carbon fiber. In yet other embodiment, it is selected from polyester fiber, polyamide fiber and polyvinyl alcohol fiber. In a further embodiment, the fiber material comprises polyamide fiber.

In one embodiment, suitable polyamides for polyamide fibers are, for example, derived from lactams having 7 to 13 ring members or obtained by reaction of dicarboxylic acids with diamines. Examples of polyamides which are derived from lactams include polycaprolactam, polycaprylolactam and/or polylaurolactam.

In other embodiment, suitable polyamides further include those obtainable from w-aminoalkyl nitriles, such as but not limited to, aminocapronitrile, which leads to nylon-6. In addition, dinitriles can be reacted with diamine. For example, adiponitrile can be reacted with hexamethylenediamine to obtain nylon-6,6. The polymerization of nitriles is affected in the presence of water and is also known as direct polymerization.

When polyamides obtainable from dicarboxylic acids and diamines are used, dicarboxylalkanes (aliphatic dicarboxylic acids) having 6 to 36 carbon atoms, or 6 to 12 carbon atoms, or 6 to 10 carbon atoms can be employed. Aromatic dicarboxylic acids are also suitable. Examples of dicarboxylic acids include adipic acid, azelaic acid, sebacic acid, dodecanedioic acid and also terephthalic acid and/or isophthalic acid.

Suitable diamines include, for example, alkanediamines having 4 to 36 carbon atoms, or 6 to 12 carbon atoms, in particular having 6 to 8 carbon atoms, and aromatic diamines, for example m- xylylenediamine, di(4-aminophenyl)methane, di(4-aminocyclohexyl)methane, 2,2-di(4- aminophenyl)propane, 2,2-di(4-aminocyclohexyl)propane and 1 ,5-diamino-2-methylpentane.

In other embodiment, polyamides include polyhexamethylenedipamide, polyhexamethylenesebacamide and polycaprolactam and also nylon-6/6,6, in particular having a proportion of caprolactam units in between 5 wt.-% to 95 wt.-%.

The non-exhaustive list which follows comprises the aforementioned polyamides for polyamide fibers that are suitable as fiber material.

AB polymers:

AA/BB polymers:

In an embodiment, suitable polyamide is selected from polyamide 6 (PA 6), polyamide 66 (PA 66), polyamide 11 (PA 11), polyamide 12 (PA 12), polyamide MXD6 (PA MXD6), mixtures and copolymers thereof, as described hereinabove. In another embodiment, polyamide is selected from PA 6, PA 66 and copolymer thereof.

For the purpose of the present invention, the fiber material can be obtained in any shape and size. For instance, fiber material can be, such as but not limited to, a strand having a lateral and through- plane dimension or a spherical particle having diameter. The presently claimed invention is not limited by the shape and size of the fiber material.

In an embodiment, the fiber material, as described herein, is subjected to surface treatment using coupling agents such as urethane coupling agent and epoxy coupling agent. Any suitable techniques for surface treatment can be used for this purpose. For instance, any suitable coating process, such as but not limited to, dip coating and spray coating can be employed.

In one embodiment, the urethane coupling agent comprises at least one urethane group. Suitable urethane coupling agents for use with fiber materials, in particular polyamides, are known to the person skilled in the art, as for instance described in US pub. no. 2018/0282496 incorporated herein by reference. In one embodiment, the urethane coupling agent comprises, for example, a reaction product of an isocyanate, such as but not limited to, m-xylylene diisocyanate (XDI), 4,4'- methylenebis(cyclohexyl isocyanate) (HMDI) or isophorone diisocyanate (IPDI), and a polyester based polyol or a polyether based polyol.

In another embodiment, the epoxy coupling agent comprises at least one epoxy group. Suitable epoxy coupling agents for use with fiber materials, in particular polyamides, are known to the person skilled in the art, as for instance described in US pub. no. 2015/0247025 incorporated herein by reference. In one embodiment, the epoxy coupling agent is selected from aliphatic epoxy coupling agent, aromatic epoxy coupling agent or mixture thereof. Non-limiting example of aliphatic coupling agent includes a polyether polyepoxy compound having two or more epoxy groups in a molecule and/or polyol polyepoxy compound having two or more epoxy groups in a molecule. As aromatic coupling agent, a bisphenol A epoxy compound or a bisphenol F epoxy compound can be used.

Suitable amounts of these coupling agents, as described herein, are well known to the person skilled in the art. However, in one embodiment, the coupling agent can be present in an amount of 0.1 parts by mass to 10.0 parts by mass relative to 100 parts by mass of the fiber material.

Commercially available fiber material provided by Trelleborg, such as but not limited to Trelleborg Circular Knit Nylon (2339C) and Trelleborg 5248 may also be employed.

Thermoplastic polyurethane resin (TPU resin)

In an embodiment, the TPU resin is obtained by reacting:

(a) a polyol,

(b) an isocyanate, and (c) optionally a chain extender.

Polyols are isocyanate reactive compounds, having a molecular weight above 500 g/mol. Suitable polyols have an average functionality in between 1.9 to 8.0, or in between 1.9 to 6.0 and an OH value in between 10 mg KOH/g to 1000 mg KOH/g, or in between 10 mg KOH/g to 500 mg KOH/g. Standard methods to determine the OH value are well known to the person skilled in the art. For instance, ASTM D4274 can be employed for determining the OH value of the polyols.

In one embodiment, the polyol is selected from a polyether polyol, a polyester polyol and a mixture thereof. In other embodiment, the polyol comprises polyether polyol.

Accordingly, in an embodiment, the TPU resin is obtained by reacting:

(a) polyether polyol,

(b) isocyanate, and

(c) optionally chain extender.

In an embodiment, suitable polyether polyols have an OH value in between 50 mg KOH/g to 500 mg KOH/g, or 50 mg KOH/g to 400 mg KOH/g, or 60 mg KOH/g to 400 mg KOH/g. In other embodiment, the OH value is in between 60 mg KOH/g to 300 mg KOH/g, or 70 mg KOH/g to 300 mg KOH/g, or 70 mg KOH/g to 200 mg KOH/g. In still other embodiment, it is in between 80 mg KOH/g to 200 mg KOH/g, or 80 mg KOH/g to 150 mg KOH/g, or 90 mg KOH/g to 150 mg KOH/g.

In another embodiment, the weight average molecular weight (M_w) of these polyether polyols is in between 500 g/mol to 10,000 g/mol, or 600 g/mol to 10,000 g/mol, or 600 g/mol to 9,000 g/mol. In one embodiment, M_w is in between 600 g/mol to 8,000 g/mol, or 600 g/mol to 7,000 g/mol, or 700 g/mol to 7,000 g/mol. In other embodiment, it is in between 700 g/mol to 6,000 g/mol, or 700 g/mol to 5,000 g/mol, or 700 g/mol to 4,000 g/mol. In still other embodiment, it is in between 800 g/mol to 4,000 g/mol, or 800 g/mol to 3,000 g/mol, or 800 g/mol to 2,000 g/mol, or 900 g/mol to 1 ,500 g/mol. Suitable techniques to determine M_w are well known to the person skilled in the art. For instance, size exclusion chromatography can be employed for determining the molecular weight here.

Suitable polyether polyols are obtainable by known methods, for example by anionic polymerization with alkali metal hydroxides, e.g., sodium hydroxide or potassium hydroxide, or alkali metal alkoxides, e.g., sodium methoxide, sodium ethoxide, potassium ethoxide or potassium isopropoxide, as catalysts and by adding at least one amine-containing starter molecule, or by cationic polymerization with Lewis acids, such as antimony pentachloride, boron fluoride etherate and so on, or fuller’s earth, as catalysts from one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene moiety.

Starter molecules are generally selected such that their average functionality is in between 2.0 to 8.0. Optionally, a mixture of suitable starter molecules is used. Starter molecules for polyether polyols include amine containing and hydroxyl-containing starter molecules. Suitable amine containing starter molecules include, for example, aliphatic and aromatic diamines such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, phenylenediamines, toluenediamine, diaminodiphenylmethane and isomers thereof.

Other suitable starter molecules further include alkanolamines, e.g. ethanolamine, N- methylethanolamine and N-ethylethanolamine, dialkanolamines, e.g., diethanolamine, N- methyldiethanolamine and N-ethyldiethanolamine, and trialkanolamines, e.g., triethanolamine, and ammonia.

Hydroxyl-containing starter molecules comprise of sugars, sugar alcohols, for e.g. glucose, mannitol, sucrose, pentaerythritol, sorbitol; polyhydric phenols, resols, e.g., oligomeric condensation products formed from phenol and formaldehyde, trimethylolpropane, glycerol, glycols such as ethylene glycol, propylene glycol and their condensation products such as polyethylene glycols and polypropylene glycols, e.g., diethylene glycol, triethylene glycol, dipropylene glycol, and water or a combination thereof.

Suitable alkylene oxides having 2 to 4 carbon atoms are, for example, ethylene oxide, propylene oxide, 1 ,2-butylene oxide, 2,3-butylene oxide and styrene oxide can also be used to obtain the polyether polyol. Alkylene oxides can be used singly, alternatingly in succession or as mixtures. In one embodiment, alkylene oxides are propylene oxide and/or ethylene oxide.

In one embodiment, suitable polyether polyols are derived from tetrahydrofuran. Tetrahydrofuran is a cyclic ether and is converted into a linear polymer called poly(tetramethylene ether)glycol (PTMEG) before obtaining the TPU resin. Commercially available polytetrahydrofuran, under the tradename PolyTHF^® from BASF, can also be used.

Suitable polyester polyols are based on the reaction product of carboxylic acids or anhydrides with hydroxy group containing compounds. Suitable carboxylic acids or anhydrides have preferably from 2 to 20 carbon atoms, or from 4 to 18 carbon atoms, for example succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, oleic acid, phthalic anhydride.

Suitable hydroxy group containing compounds comprise of ethanol, ethylene glycol, propyl-ene-1 ,2- glycol, propylene-1 , 3-glycol, butyl-ene-1 , 4-glycol, butylene-2, 3-glycol, hexane-1 , 6-diol, octane-1 , 8- diol, neopentyl glycol, cyclohexane dimethanol (1 ,4-bis-hydroxy-methylcyclohexane), 2-methyl- propane-1 ,3-diol, glycerol, trimethylolpropane, hex-ane-1 ,2,6-triol, butane -1 ,2,4-triol, trimethylolethane, pentaerythritol, quinitol, mannitol, sorbitol, methyl glycoside, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, polyethylene-propylene glycol, dibutylene glycol and polybutylene glycol. Suitable isocyanate comprises an aromatic isocyanate or an aliphatic isocyanate. By the term “aromatic isocyanate”, it is referred to molecules having two or more isocyanate groups attached directly and/or indirectly to the aromatic ring. Further, it is to be understood that the isocyanate includes both monomeric and polymeric forms of the aliphatic and aromatic isocyanate. By the term “polymeric”, it is referred to the polymeric grade of the aliphatic and/or aromatic isocyanate comprising, independently of each other, different oligomers and homologues.

In one embodiment, the isocyanate comprises aromatic isocyanate. Suitable aromatic isocyanate is selected from toluene diisocyanate; polymeric toluene diisocyanate, methylene diphenyl diisocyanate and/or polymeric methylene diphenyl diisocyanate; m-phenylene diisocyanate; 1 ,5-naphthalene diisocyanate; 4-chloro-1 ; 3-phenylene diisocyanate; 2,4,6-toluylene triisocyanate, 1 ,3- diisopropylphenylene-2, 4-diisocyanate; 1 -methyl-3, 5-diethylphenylene-2, 4-diisocyanate; 1 ,3,5- triethylphenylene-2, 4-diisocyanate; 1 , 3, 5-triisoproply-phenylene-2, 4-diisocyanate; 3,3'-diethyl- bisphenyl-4,4'-diisocyanate; 3,5,3',5'-tetraethyl-diphenylmethane-4,4'-diisocyanate; 3, 5,3', 5'- tetraisopropyldiphenylmethane-4,4'-diisocyanate; 1-ethyl-4-ethoxy-phenyl-2, 5-diisocyanate; 1 ,3,5- triethyl benzene-2, 4, 6-triisocyanate; 1 -ethyl-3, 5-diisopropyl ben-zene-2, 4, 6-triisocyanate, tolidine diisocyanate and 1 ,3,5-triisopropyl benzene-2, 4, 6-triisocyanate.

In an embodiment, the aromatic isocyanate is selected from toluene diisocyanate; polymeric toluene diisocyanate, methylene diphenyl diisocyanate and/or polymeric methylene diphenyl diisocyanate; m-phenylene diisocyanate; 1 ,5-naphthalene diisocyanate; 4-chloro-1 ; 3-phenylene diisocyanate; 2,4,6-toluylene triisocyanate, 1 ,3-diisopropylphenylene-2, 4-diisocyanate; 1-methyl-3,5- diethylphenylene-2, 4-diisocyanate; 1 , 3, 5-triethylphenylene-2, 4-diisocyanate; 1 ,3,5-triisoproply- phenylene-2, 4-diisocyanate; 3,3'-diethyl-bisphenyl-4,4'-diisocyanate; 3,5,3',5'-tetraethyl- diphenylmethane-4,4'-diisocyanate and 3,5,3',5'-tetraisopropyldiphenylmethane-4,4'-diisocyanate.

In other embodiment, the aromatic isocyanate is selected from toluene diisocyanate; polymeric toluene diisocyanate, methylene diphenyl diisocyanate and/or polymeric methylene diphenyl diisocyanate; m-phenylene diisocyanate; 1 ,5-naphthalene diisocyanate; 4-chloro-1 ; 3-phenylene diisocyanate; 2,4,6-toluylene triisocyanate, 1 ,3-diisopropylphenylene-2, 4-diisocyanate. In still other embodiment, it is selected from methylene diphenyl diisocyanate and/or polymeric methylene diphenyl diisocyanate.

Accordingly, in another embodiment, the TPU resin is obtained by reacting:

(a) polyether polyol, and

(b) methylene diphenyl diisocyanate and/or polymeric methylene diphenyl diisocyanate.

In another embodiment, the TPU resin is obtained by reacting:

(a) polyether polyol,

(b) methylene diphenyl diisocyanate and/or polymeric methylene diphenyl diisocyanate, and

(c) optionally chain extender. Methylene diphenyl diisocyanate is available in three different isomeric forms, namely 2,2'-methylene diphenyl diisocyanate (2,2'-MDI), 2,4'-methylene diphenyl diisocyanate (2,4'-MDI) and 4,4'-methylene diphenyl diisocyanate (4,4'-MDI). Methylene diphenyl diisocyanate can be classified into monomeric methylene diphenyl diisocyanate and polymeric methylene di-phenyl diisocyanate referred to as technical methylene diphenyl diisocyanate. Polymeric methylene di-phenyl diisocyanate includes oligomeric species and methylene diphenyl diisocyanate isomers. Thus, polymeric methylene diphenyl diisocyanate may contain a single methylene diphenyl diisocyanate isomer or isomer mixtures of two or three methylene diphenyl diisocyanate isomers, the balance being oligomeric species. Polymeric methylene diphenyl diisocyanate tends to have isocyanate functionalities of higher than 2. The isomeric ratio as well as the amount of oligomeric species can vary in wide ranges in these products. For instance, polymeric methylene diphenyl diisocyanate may typically contain 30 wt.-% to 80 wt.-% of methylene diphenyl diisocyanate isomers, the balance being said oligomeric species. The methylene diphenyl diisocyanate isomers are often a mixture of 4,4'-methylene diphenyl diisocyanate, 2,4'-methylene diphenyl diisocyanate and very low levels of 2,2'-methylene di-phenyl diisocyanate.

Optionally, isocyanate reactive compounds having molecular weight in between ³ 49 g/mol to £ 499 g/mol may also be employed as reactants for obtaining the TPU resin. In the present context, these compounds are referred to as chain extenders.

In one embodiment, the chain extender is selected from ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, 1 ,4- butylene glycol, 1 ,5-pentylene glycol, methylpentanediol, 1 ,6-hexylene glycol, neopentyl glycol, trimethylolpropane, glycerol, pentaerythritol, diglycerol, dextrose, 1 ,4:3, 6 dianhydrohexitol, hydroquinone bis 2-hydroxyethyl ether and bis-2(hydroxy ethyl)-terephthalate.

In other embodiment, the chain extender is selected from ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, 1 ,4-butylene glycol, 1 ,5-pentylene glycol, methylpentanediol, 1 ,6-hexylene glycol, neopentyl glycol, trimethylolpropane, glycerol, pentaerythritol, diglycerol and dextrose.

In yet other embodiment, the chain extender is selected from ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, 1 ,4-butylene glycol, 1 ,5-pentylene glycol and methylpentanediol.

In still other embodiment, the chain extender is selected from triethylene glycol, propylene glycol, 1 ,3- propanediol and 1 ,4-butanediol. In a further embodiment, the chain extender comprises 1 ,4- butanediol.

Suitable conditions for reacting the polyol, isocyanate and optionally chain extender, as described herein, to obtain the TPU resin are well known to the person skilled in the art. Suitable amounts of the polyol, isocyanate and optionally chain extender are reacted at an isocyanate index between ³ 70 to £ 150 to obtain the TPU resin.

Accordingly, in an embodiment, the TPU resin is obtained by reacting:

(a) polyol,

(b) isocyanate, and

(c) optionally chain extender, at an isocyanate index between ³ 70 to £ 150.

In another embodiment, the TPU resin is obtained by reacting:

(a) polyether polyol,

(c) optionally chain extender, at an isocyanate index between ³ 70 to £ 150.

In another embodiment, the TPU resin is obtained by reacting:

(a) polyether polyol, and

(b) methylene diphenyl diisocyanate and/or polymeric methylene diphenyl diisocyanate, at an isocyanate index between ³ 70 to £ 150.

In one embodiment, the isocyanate index is in between ³ 80 to £ 150, or ³ 80 to £ 140, or ³ 90 to £ 140. In another embodiment, it is in between ³ 90 to £ 130, or ³ 90 to £ 120, or ³ 90 to £ 110. In still other embodiment, it is in between ³ 95 to £ 105. The isocyanate index describes the molar ratio of NCO groups to isocyanate reactive groups (polyol and chain extender). An index of 100 relates to a ratio of 1 : 1.

The TPU resin, as described herein, further comprises reinforcing agents and additives. For the purpose of the present invention, reinforcing agent is selected from metal fiber, metalized inorganic fiber, metalized synthetic fiber, glass fiber, polyester fiber, polyamide fiber, polyvinyl alcohol fiber, aramid fiber, graphite fiber, carbon fiber, ceramic fiber, mineral fiber, basalt fiber, inorganic fiber, aramid fiber, kenaf fiber, jute fiber, flax fiber, hemp fiber, cellulosic fiber, sisal fiber and coir fiber.

In an embodiment, the reinforcing agent may be obtained in any shape and size. In another embodiment, the reinforcing agent is subjected to a surface treatment agent. The surface treatment agent is also referred to as sizing. The reinforcing agent when subjected to the surface treatment agent further improve the mechanical properties of the TPU resin. T ypically, sizing provides adhesion between the reinforcing agent and the TPU resin.

In another embodiment, the surface treatment agent is a coupling agent and is selected from silane coupling agent, titanium coupling agent and aluminium coupling agent. In one embodiment, the coupling agent comprises silane coupling agent. Suitable silane coupling agent are selected from aminosilane, epoxysilane, methyltrimethoxysilane, methyltriethoxysilane, y- glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane and vinyltrimethoxysilane.

Suitable amounts of the reinforcing agent in the TPU resin are well known to the person skilled in the art. In one embodiment, the amount of the reinforcing agent, as described herein, is such that the weight ratio between the reinforcing agent and the TPU resin is in between ³ 0.01 : 1.0 to £ 1.0: 10.

In another embodiment, additive is selected from flame retardants, surfactants, dyes, pigments, IR absorbing materials, UV stabilizers, plasticizers, antistats, fungicides, bacteriostats, hydrolysis controlling agents, curing agents, antioxidants and cell regulators. Further details regarding additives can be found, for example, in the Kunststoffhandbuch, Volume 7,“Polyurethane” Carl-Hanser-Verlag Munich, 1 st edition, 19662nd edition, 1983 and 3rd edition, 1993. Suitable amounts of these additives are well known to the person skilled in the art. However, for instance, the additives can be present in amounts up to 20 wt.-% based on the total weight of the TPU resin.

The TPU resin, as obtained herein, has the shore hardness ranging from a Shore A hardness of 70 to a Shore D hardness of 80 determined according to ASTM D 2240 and the flexural modulus in between 40 MPa to 2000 MPa determined according to ASTM D790.

In another embodiment, the shore hardness ranges between Shore A hardness of 80 to Shore D hardness of 80, or in between Shore A hardness of 80 to Shore D hardness of 70. In yet another embodiment, it ranges between Shore A hardness of 90 to Shore D hardness of 70, or in between Shore A hardness of 90 to Shore D hardness of 60.

Method

The insert adds to the strength in high stress areas. Accordingly, the insert can be of any suitable geometry depending on the application of the insert-molded article. For instance, the insert can have a fabric geometry. The term“fabric geometry” here refers to the geometry obtained by weaving the fiber material together to form a fabric.

In an embodiment, suitable mold having cavity is chosen, depending on the application of the insert- molded article obtained herein. The cavity is defined by plurality of surfaces which comprise of at least one primary surface. By the term“surface”, it is referred to any plane surface, irregular surface, or even curved surface. The person skilled in the art is well aware of the fact that the desired geometry of the insert-molded article determines the shape of the mold, which in turn determines the shape of the surface of the cavity.

In one embodiment, the primary surface is selected from a horizontal surface, a vertical surface or a curved surface. In another embodiment, the insert comprising the first surface is provided in the mold, wherein at least a portion of the first surface of the insert is in contact with the primary surface. The insert also defines a second surface opposite to the first surface. The first surface and the second surface are separated by a thickness. The thickness here depends on the application of the insert-molded article and therefore, varies based on the same.

In another embodiment, the insert is provided in the mold and held tightly or fixed with at least a portion of the first surface of the insert being in contact with the primary surface of the cavity. Suitable means to hold or fix the insert are well known to the person skilled in the art. For instance, stoppers having an array of external threads may be used to hold the insert. In that case, an array of internal threads are created in the insert so that the internal threads of the insert are engageable with the external threads of the stopper. This is also described in US pat. No. 7,189,920 B2, incorporated herein by reference. Also, movable pins in the mold can be used to rigidly hold the insert. Alternatively, suitable adhesives may be employed for this purpose.

In another embodiment, the insert is equidistantly placed from the plurality of surfaces, as described herein. That is, to say, that the insert is placed at the center of the cavity.

In step (B), the TPU resin, as described herein, is injection molded to fill the cavity. In an embodiment, the TPU resin completely encapsulates the second surface of the insert. In one embodiment, at least a portion of the first surface of the insert is visible in the insert-molded article. In another embodiment, the entire of the first surface of the insert is visible. In other words, overmolding takes place, i.e. when at least a portion or the entire of the first surface is visible. This is also referred to as overmolding.

In another embodiment, the first surface and the second surface of the insert are completely encapsulated by the TPU resin. This implies that the insert is completely encapsulated by the TPU resin. Said otherwise, the insert will not be visible in the insert-molded article obtained herein. This situation is interchangeably also referred as complete molding.

It is to be understood that both overmolding and complete molding impart advantageous properties to the article obtained. Commonly, both provide a control over the flexural properties with improvement in tensile properties and are capable of maintaining the elastomeric properties while providing for acceptable long term properties such as creep recovery, stress relaxation and fatigue resistance.

Advantageously, the insert-molded article, as obtained herein, has the tensile yield strength of at least 5 MPa determined according to ASTM D412 and the flexural modulus of less than 20% of the flexural modulus of the TPU resin. In one embodiment, the flexural modulus is less than 10% of the flexural modulus of the TPU resin. In other embodiment, it is in between 0% to 10%, or in between 0% to 5% of the flexural modulus of the TPU resin. In yet other embodiment, the insert molded article has improved creep recovery. In order to determine the creep recovery, the insert molded article is clamped in a tensile creep station and is subjected to a vertical load. The tensile chamber is then heated upto 40°C and the article is removed after 48 h. The length of the article is measured and the time is recorded for several times upto 48 h.

Thus, the presently claimed method provides a good control over the flexural modulus as it retains the flexural modulus of the elastomeric TPU resin, while providing for acceptable tensile yield strength values.

Another aspect of the present invention describes an insert-molded article, as obtained herein.

The insert molded article has improved mechanical properties which render it suitable for applications such as non-pneumatic tires, conveyor belts, casters and pulley type belts.

Yet another aspect of the present invention is directed to the use of the above insert-molded article for non-pneumatic tires, conveyor belts, casters and pulley type belts.

The present invention is illustrated in more detail by the following embodiments and combinations of embodiments which result from the corresponding dependency references and links:

1. A method for producing an insert-molded article, said method comprising at least the steps of:

(B) injection molding at least one thermoplastic polyurethane resin to fill the cavity in step (A) to obtain the insert-molded article,

wherein the insert-molded article has a tensile yield strength of at least 5 MPa determined according to ASTM D412 and a flexural modulus of less than 20% of the flexural modulus of the thermoplastic polyurethane resin.

2. The method according to embodiment 1 , wherein the insert comprises a fiber material.

3. The method according to embodiment 2, wherein the fiber material is selected from metal fiber, metalized inorganic fiber, metalized synthetic fiber, glass fiber, polyester fiber, polyamide fiber, polyvinyl alcohol fiber, aramid fiber, graphite fiber, carbon fiber, ceramic fiber, mineral fiber, basalt fiber, inorganic fiber, aramid fiber, kenaf fiber, jute fiber, flax fiber, hemp fiber, cellulosic fiber, sisal fiber and coir fiber. 4. The method according to embodiment 2 or 3, wherein the fiber material comprises polyamide fiber.

5. The method according to embodiment 4, wherein the polyamide fiber comprises polyamide.

6. The method according to embodiment 5, wherein polyamide is selected from polyamide 6 (PA 6), polyamide 66 (PA 66), polyamide 1 1 (PA 11), polyamide 12 (PA 12), polyamide MXD6 (PA MXD6), mixtures and copolymers thereof.

7. The method according to embodiment 5 or 6, wherein polyamide is selected from polyamide 6 (PA 6), polyamide 66 (PA 66) and copolymer thereof.

8. The method according to one or more of embodiments 1 to 7, wherein the thermoplastic polyurethane resin is obtained by reacting:

(a) a polyol,

(b) an isocyanate, and

(c) optionally a chain extender.

9. The method according to embodiment 8, wherein the polyol is selected from a polyether polyol, a polyester polyol and a mixture thereof.

10. The method according to embodiment 8 or 9, wherein the polyol comprises polyether polyol.

11. The method according to embodiment 10, wherein the polyether polyol has a functionality in between ³ 1.9 to £ 2.1 and an OH value in the range of ³ 10 mgKOH/g to £ 500 mgKOH/g.

12. The method according to one or more of embodiments 8 to 1 1 , wherein the isocyanate comprises an aliphatic isocyanate or an aromatic isocyanate.

13. The method according to one or more of embodiments 8 to 12, wherein the isocyanate comprises aromatic isocyanate.

14. The method according to embodiment 13, wherein the aromatic isocyanate is selected from toluene diisocyanate; polymeric toluene diisocyanate, methylene diphenyl diisocyanate and/or polymeric methylene diphenyl diisocyanate; m-phenylene diisocyanate; 1 ,5-naphthalene diisocyanate; 4-chloro-1 ; 3-phenylene diisocyanate; 2,4,6-toluylene triisocyanate, 1 ,3- diisopropylphenylene-2, 4-diisocyanate; 1-methyl-3,5-diethylphenylene-2, 4-diisocyanate; 1 ,3,5- triethylphenylene-2, 4-diisocyanate; 1 , 3, 5-triisoproply-phenylene-2, 4-diisocyanate; 3,3'-diethyl- bisphenyl-4,4'-diisocyanate; 3,5,3',5'-tetraethyl-diphenylmethane-4,4'-diisocyanate; 3, 5,3', 5'- tetraisopropyldiphenylmethane-4,4'-diisocyanate; 1-ethyl-4-ethoxy-phenyl-2, 5-diisocyanate; 1 ,3,5- triethyl benzene-2, 4, 6-triisocyanate; 1 -ethyl-3, 5-diisopropyl ben-zene-2, 4, 6-triisocyanate, tolidine diisocyanate and 1 ,3,5-triisopropyl benzene-2, 4, 6-triisocyanate.

15. The method according to one or more of embodiments 12 to 14, wherein the aromatic isocyanate comprises methylene diphenyl diisocyanate and/or polymeric methylene diphenyl diisocyanate.

16. The method according to one or more of embodiments 8 to 15, wherein the chain extender has a molecular weight in between ³ 49 g/mol to £ 499 g/mol.

17. The method according to one or more of embodiments 8 to 16, wherein the chain extender is selected from ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, 1 ,4-butylene glycol, 1 ,5-pentylene glycol, methylpentanediol, 1 ,6-hexylene glycol, neopentyl glycol, trimethylolpropane, glycerol, pentaerythritol, diglycerol, dextrose, 1 ,4:3, 6 dianhydrohexitol, hydroquinone bis 2-hydroxyethyl ether and bis-2(hydroxy ethyl)-terephthalate.

18. The method according to one or more of embodiments 8 to 17, wherein the thermoplastic polyurethane further comprises reinforcing agents and additives.

19. The method according to embodiment 18, wherein the reinforcing agent is selected from metal fiber, metalized inorganic fiber, metalized synthetic fiber, glass fiber, polyester fiber, polyamide fiber, polyvinyl alcohol fiber, aramid fiber, graphite fiber, carbon fiber, ceramic fiber, mineral fiber, basalt fiber, inorganic fiber, aramid fiber, kenaf fiber, jute fiber, flax fiber, hemp fiber, cellulosic fiber, sisal fiber and coir fiber.

20. The method according to embodiment 19, wherein the reinforcing agent is subjected to a surface treatment agent.

21. The method according to embodiment 20, wherein the surface treatment agent comprises a coupling agent.

22. The method according to embodiment 21 , wherein the coupling agent is selected from silane coupling agent, titanium coupling agent and aluminium coupling agent.

23. The method according to one or more of embodiments 18 to 22, wherein the additive is selected from flame retardants, surfactants, dyes, pigments, IR absorbing materials, UV stabilizers, plasticizers, antistats, fungicides, bacteriostats, hydrolysis controlling agents, curing agents, antioxidants and cell regulators. 24. The method according to one or more of embodiments 1 to 23, wherein the thermoplastic polyurethane resin has the shore hardness ranging from a Shore A hardness of 70 to a Shore D hardness of 60 determined according to ASTM D 2240.

25. The method according to one or more of embodiments 1 to 24, wherein the primary surface is selected from a horizontal surface, a vertical surface or a curved surface.

26. The method according to one or more of embodiments 1 to 25, wherein in step (A) the insert is equidistantly placed from the plurality of surfaces.

27. The method according to one or more of embodiments 1 to 26, wherein the insert has a second surface opposite to the first surface, said second surface being completely encapsulated by the thermoplastic polyurethane resin in step (B).

28. The method according to one or more of embodiments 1 to 27, wherein both the first surface and the second surface of the insert are completely encapsulated by the thermoplastic polyurethane resin in step (B).

29. An insert-molded article obtained by the process according to one or more of embodiments 1 to 28.

30. Use of the insert-molded article according to embodiment 29 or as obtained by the process according to one or more of embodiments 1 to 28 for non-pneumatic tires, conveyor belts, casters and pulley type belts.

Examples

The presently claimed invention is illustrated by the non-restrictive examples which are as follows: Compounds

Standard methods

TPU flex bars having dimensions of 5 inch ^c 0.5 inch ^c 1/8 inch were obtained from standard ASTM D790 technique.

Samples with the fiber materials insert molded at the center of the TPU flex bar were tested for their mechanical properties. 0.01 inch thick tape of the fiber materials were insert molded at the center of the TPU flex bar obtained in accordance with ASTM D790. For the sake of comparison, a TPU flex bar without any fiber material was used. The results obtained are summarized in Table 1 below:

Table 1 : Samples with and without fiber material

Flexural modulus of the flex bar was determined by hand. A simple flexing of the bars by hand showed there was virtually no difference in flexural modulus. Further, the tensile yield increased considerably upon insert molding with the fiber material, as shown in Table 1. Particularly, the tensile yield almost doubled for FM1 , while it increased by -23% for FM2.

Further, the TPU Flex bars were injection molded in two configurations i.e. one with only TPU flex bar and the other with FM1 of 0.01 inch thickness inserted in the center of the bar and then overmolded with the TPU. Lengths of each bar was measured, and this was used as the baseline length. The bars were clamped in the tensile creep station and a vertical load of 300 psi was placed on the bars. Then the chamber was heated up to 40°C and the bars were removed after 48 h. The length of each bar was measured and recorded at time zero, and then lengths were measured at various times up to 48 h to determined how much of the stretched length recovered with time. The results are summarized in Table 2 below:

Table 2: Creep recovery results

As observed in table 2, the TPU flex bar with FM1 fully recovered, while the TPU flex bar without the fiber material recovered partially i.e. it measured 7% longer than the original length. Accordingly, adding the fiber material as insert in the TPU flex bar improved the creep resistance significantly. This renders the present invention suitable for non-pneumatic tires, conveyor belts, casters and pulley type belts.

Claims

wherein the thermoplastic polyurethane resin has a shore hardness ranging from a Shore A hardness of 70 to a Shore D hardness of 80 determined according to ASTM D 2240 and a flexural modulus in between 40 MPa to 2000 MPa determined according to ASTM D790, and wherein the insert-molded article has a tensile yield strength of at least 5 MPa determined according to ASTM D412 and a flexural modulus of less than 20% of the flexural modulus of the thermoplastic polyurethane resin.

2. The method according to claim 1 , wherein the insert comprises a fiber material.

3. The method according to claim 2, wherein the fiber material is selected from metal fiber, metalized inorganic fiber, metalized synthetic fiber, glass fiber, polyester fiber, polyamide fiber, polyvinyl alcohol fiber, aramid fiber, graphite fiber, carbon fiber, ceramic fiber, mineral fiber, basalt fiber, inorganic fiber, aramid fiber, kenaf fiber, jute fiber, flax fiber, hemp fiber, cellulosic fiber, sisal fiber and coir fiber.

4. The method according to claim 2 or 3, wherein the fiber material comprises polyamide fiber.

5. The method according to claim 4, wherein polyamide is selected from polyamide 6, polyamide

66 and copolymer thereof.

6. The method according to one or more of claims 1 to 5, wherein the thermoplastic polyurethane resin is obtained by reacting:

(a) a polyol,

(b) an isocyanate, and

(c) optionally a chain extender.

7. The method according to claim 6, wherein the polyol comprises polyether polyol.

8. The method according to claim 7, wherein the polyether polyol has a functionality in between ³

1.9 to £ 2.1 and an OH value in the range of ³ 10 mgKOH/g to £ 500 mgKOH/g.

9. The method according to one or more of claims 1 to 8, wherein the primary surface is selected from a horizontal surface, a vertical surface or a curved surface.

10. The method according to one or more of claims 1 to 9, wherein in step (A) the insert is equidistantly placed from the plurality of surfaces.

11. The method according to one or more of claims 1 to 10, wherein the insert has a second surface opposite to the first surface, said second surface being completely encapsulated by the thermoplastic polyurethane resin in step (B).

12. The method according to one or more of claims 1 to 11 , wherein both the first surface and the second surface of the insert are completely encapsulated by the thermoplastic polyurethane resin in step (B).

13. An insert-molded article obtained by the method according to one or more of claims 1 to 12.

14. Use of the insert-molded article according to claim 13 or as obtained by the process according to one or more of claims 1 to 12 for non-pneumatic tires, conveyor belts, casters and pulley type belts.