WO2025156261A1

WO2025156261A1 - A polyurethane hot melt adhesive composition and the use thereof

Info

Publication number: WO2025156261A1
Application number: PCT/CN2024/074248
Authority: WO
Inventors: Hongye ZHU; Aifu CHE
Original assignee: Henkel China Investment Co Ltd; Henkel AG and Co KGaA
Current assignee: Henkel China Investment Co Ltd; Henkel AG and Co KGaA
Priority date: 2024-01-26
Filing date: 2024-01-26
Publication date: 2025-07-31
Anticipated expiration: 2026-07-26

Abstract

The present invention relates to a polyurethane hot melt adhesive composition and the use thereof. In particular, the present invention provides an adhesive comprising (A) at least one NCO-terminated polyurethane prepolymer comprising the reaction product of the following components: a) at least one polyester polyol, b) at least one polyether polyol, and c) at least one polyisocyanate; and (B) at least one copolyester polymer having a number average molecular weight (Mn) of more than 10, 000 g/mol and a glass temperature of less than 0℃; wherein the component (B) is present in an amount of from 3% to 26% by weight of based on the total weight of the composition.

Description

A polyurethane hot melt adhesive composition and the use thereof

Technical field

The present invention relates to a polyurethane hot melt adhesive composition and the use thereof. In particular, the present invention provides an adhesive composition exhibiting high resilience, good bonding strength and softness upon curing.

Background

Polyurethane hot melt adhesives have been widely used in bonding textile to textile, especially in garments or underwear, particularly yoga pants and women’s underwear, to replace sewing and heat-sealing tapes and provide shaping and support, which simplifies processes, saves costs, reduces lead time, and obtains more competitive products in the market.

Reactive hot melt adhesives based on isocyanate-terminated (also referred to as “NCO-terminated” ) polyurethane prepolymers are described for example by H. F. Hüber and H. Müller in “Shaping Reactive Hotmelts Using LMW Copolyesters” , Adhesives Age, November 1987, pages 32 to 35.

However, existing polyurethane hot melt adhesives cannot exhibit high resilience, good bonding strength and softness simultaneously. Therefore, there is a need in the art for polyurethane hot melt adhesives that overcome this drawback.

Summary of the invention

Disclosed herein is a polyurethane hot melt adhesive composition comprising

(A) at least one NCO-terminated polyurethane prepolymer comprising the reaction product of the following components:

a) at least one polyester polyol,

b) at least one polyether polyol, and

c) at least one polyisocyanate; and

(B) at least one copolyester polymer having a number average molecular weight (Mn) of more than 10,000 g/mol and a glass temperature of less than 0℃;

wherein the component (B) is present in an amount of from 3%to 26%by weight of based on the total weight of the composition.

Also disclosed herein is a cured product of the polyurethane hot melt adhesive composition according to the present invention.

Also disclosed herein is the use of the polyurethane hot melt adhesive composition according to the present invention for bonding two substrates, especially in a garment or underwear, wherein at least one of the two substrates is textile.

Other features and aspects of the subject matter are set forth in greater detail below.

Detailed Description

It is to be understood by one of ordinary skill in the art that the present invention is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present invention. Each aspect so described 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.

Unless specified otherwise, in the context of the present invention, the terms used are to be construed in accordance with the following definitions.

Unless specified otherwise, as used herein, the terms “a” , “an” and “the” include both singular and plural referents.

The terms “comprising” and “comprises” 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 process steps.

The term “at least one” or “one or more” used herein to define a component refers to the type of the component, and not to the absolute number of molecules. For example, “one or more polyols” means one type of polyol or a mixture of a plurality of different polyols.

The term “amorphous” used herein means having no melt transition when measured using Differential Scanning Calorimetry (DSC) .

The term “crystalline” used herein means having a melt transition when measured using Differential Scanning Calorimetry (DSC) .

The term "room temperature" as used herein refers to a temperature of 20 ℃ to 25 ℃, preferably 25 ℃.

Unless specified otherwise, the recitation of numerical end points includes all numbers and fractions subsumed within the respective ranges, as well as the recited end points.

All references cited in the present specification are hereby incorporated by reference in their entirety.

The molecular weights refer to number average molecular weights (Mn) , unless otherwise stipulated. All molecular weight data refer to values obtained by gel permeation chromatography (GPC) , unless otherwise stipulated, e.g., according to DIN 55672.

In this context, the glass transition temperature (Tg) or the melting point of a specific polymer is determined using DSC according to DIN 53 765.

The term “melting point” used herein is determined by melting curve obtained by Differential Scanning Calorimetry (DSC) method.

Unless otherwise defined, all terms used in the present invention, including technical and scientific terms, have the meaning as commonly understood by one of the ordinary skilled in the art to which this invention belongs.

In one aspect, the present disclosure is generally directed to a polyurethane hot melt adhesive composition, comprising

a) at least one polyester polyol,

b) at least one polyether polyol, and

c) at least one polyisocyanate; and

(A) NCO-terminated prepolymer

According to the present invention, the polyurethane hot melt adhesive composition comprises from at least one NCO-terminated polyurethane prepolymer.

There is no particular limitation on the specific type of the NCO-terminated polyurethane prepolymer, which can be reaction product of a reaction mixture comprising a) at least one polyester polyol, b) at least one polyether polyol, and c) at least one polyisocyanate.

By setting the NCO/OH ratio to more than 1, the NCO-terminated polyurethane prepolymer contains free isocyanate groups and is terminated by the isocyanate groups. As an intermediate on the way to crosslinked polyurethane, the NCO-terminated polyurethane prepolymer reacts with a substrate surface or ambient moisture in order to extent the backbone and thus form a polyurethane polymer. Through the diffusion of moisture from the atmosphere or the substrates into the adhesive and subsequent reaction, the polyurethane prepolymer cures under atmosphere conditions. Therefore, the polyurethane hot melt adhesive composition is reactive and moisture curable. The cured adhesive product is a crosslinked material primarily bonded through urea groups and urethane groups.

In one embodiment, the polyurethane prepolymer has an NCO/OH ratio, which is a molar ratio of the NCO group of component c) to the total OH groups of components a) and b) , of from 1.5 to 2.5. With the NCO/OH ratio falling within the aforementioned ranges, the polyurethane prepolymer crosslinks sufficiently upon exposure to moisture, and has a desirable viscosity which is easy to spray without wiredrawing or penetrating through textile.

In one embodiment, the component (A) is present in an amount of from 54%to 97%by weight, preferably from 74%to 97%by weight, based on the total weight of the composition.

a) Polyester polyol

According to the present invention, a) at least one polyester polyol is comprised in the reaction product of the NCO-terminated polyurethane prepolymer.

The component a) used in the present invention preferably is solid at room temperature. The component a) can be a crystalline polyester polyol, a semi-crystalline polyester polyol, a solid amorphous polyester polyol, or a combination thereof, preferably a crystalline polyester polyol or/and a semi-crystalline polyester polyol.

The term “semi-crystalline polyester polyol” means a polyester polyol comprising crystalline regions and amorphous regions in its structure. It preferably has a degree of crystallinity by weight of at least 20%to less than 80%, preferably of at least 30%to less than 80%, preferably at least 40%and less than 80%.

Useful amorphous polyester polyol preferably has a degree of crystallinity by weight of less than 10%, preferably of less than 5%, advantageously of less than 2%and more advantageously still of less than 1%.

Useful crystalline polyester polyol preferably has a crystalline form. It preferably has a degree of crystallinity by weight of at least 80%, preferably of at least 90%.

The degree of crystallinity, denoting the proportion of substance in the crystalline state, can be determined by X-ray diffraction analysis at different angles of incidence, by calorimetric measurements, such as DSC (Differential Scanning calorimetry) , or by any other technique which makes it possible to estimate the proportion of crystalline phase of the semicrystalline polyester polyol.

Examples of useful crystalline polyester polyols or semi-crystalline polyester polyols can be obtained by ring opening polymerization of a lactone such as ε-caprolactone and/or be derived from diols and diacids. Examples of diols useful in preparing preferred polyester polyols include ethylene glycol, diethylene glycol, 1, 3-propylene glycol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, 1, 8-octanediol, 1, 10-decanediol, and mixtures thereof. Examples of diacids useful in preparing preferred polyester polyols include succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and 1, 12-dodecanedioic acid, dimer acid, and mixtures thereof. Included within the scope of useful diacids are various diacid derivatives such as carboxylate esters (especially the methyl and ethyl esters) , acid halides (such as acid chlorides) and acid anhydrides, and a combination thereof.

Specific examples of suitable crystalline polyester polyols include poly (hexanediol adipate) polyol, poly (butanediol adipate) polyol, poly-epsilon-caprolactone polyol, poly (hexanediol dodecanedioate) polyol, poly (hexanediol adipic acid terephthalate) polyol, polycaprolactone polyol, and a combination thereof.

In preferred embodiments, the crystalline polyester polyol or semi-crystalline polyester polyol has a melting point of less than 70℃, preferably less than 60℃.

Examples of useful solid amorphous polyester polyols includes the reaction product of a polyacid component (e.g., polyacid, polyacid anhydride, polyacid ester and polyacid halide) , and a stoichiometric excess of polyol. At least one of the polyacid component and the polyol includes an aromatic group. Suitable polyacids include, e.g., diacids (e.g., dicarboxylic acids) , triacids (e.g., tricarboxylic acids) , and higher order acids, examples of which include aromatic dicarboxylic acids, anhydrides and esters thereof (e.g. terephthalic acid, isophthalic acid, dimethyl terephthalate, diethyl terephthalate, phthalic acid, phthalic anhydride, methyl-hexahydrophthalic acid, methylhexahydrophthalic anhydride, methyl-tetrahydrophthalic acid, methyl-tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, and tetrahydrophthalic acid) , aliphatic dicarboxylic acids and anhydrides thereof (e.g. maleic acid, maleic anhydride, succinic acid, succinic anhydride, glutaric acid, glutaric anhydride, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, chlorendic acid, 1, 2, 4-butane-tricarboxylic acid, decanedicarboxylic acid, octadecanedicarboxylic acid, dimeric acid, dimerized fatty acids, trimeric fatty acids, and fumaric acid) , and alicyclic dicarboxylic acids (e.g. 1, 3-cyclohexanedicarboxylic acid, and 1, 4-cyclohexanedicarboxylic acid) , and a mixture thereof. Examples of suitable polyols include aliphatic polyols, e.g., ethylene glycols, propane diols (e.g., 1, 2-propanediol and 1, 3-propanediol) , butanediols (e.g., 1, 3-butanediol, 1, 4-butanediol, and 1, 2-butanediol) , 1, 3-butenediol, 1, 4-butenediol, 1, 4-butynediol, pentane diols (e.g., 1, 5-pentanediol) , pentenediols, pentynediols, 1, 6-hexanediol, 1, 8-octanediol, 1, 10-decanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols, propylene glycol, polypropylene glycols (e.g., dipropylene glycol and tripropylene glycol) , 1, 4-cyclohexanedimethanol, 1, 4-cyclohexanediol, dimer diols, bisphenol A, bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, glycerol, tetramethylene glycol, polytetramethylene glycol, 3-methyl-1, 5-pentanediol, 1, 9-nonanediol, 2-methyl-1, 8-octanediol, trimethylolpropane, pentaerythritol, sorbitol, glucose, and a combination thereof.

Specific examples of useful solid amorphous polyester polyols include poly (hexanediol phthalate) polyol, poly (neopentyl glycol adipate) polyol, poly (neopentyl glycol phthalate) polyol, poly (neopentyl glycol hexanediol phthalate) polyol, poly (diethylene glycol phthalate) polyol, poly (ethylene glycol adipic acid terephthalate) polyol, polyethylene terephthalate polyols, random copolymer diols of ethylene glycol, hexane diol, neopentyl glycol, adipic acid and terephthalic acid, and a combination thereof.

In preferred embodiments, the component a) has a number average molecular weight (Mn) of from 1,000 to 10,000 g/mol, preferably from 2,000 to 10,000 g/mol, and more preferably from 2,000 to 8,000 g/mol.

The above-mentioned polyester polyol can be used singly or in combination with two or more thereof. If at least two polyester polyols are used in the adhesive composition, each one of number average molecular weight (Mn) preferably falls into the claimed range.

Suitable commercially available polyester polyols are sold under the DYNACOLL 7300 series of trade designations from Evonik including DYNACOLL 7360, 7361, 7362, 7363, 7365, 7381, etc.; and under the CAPATM series of trade designations from Ingevity including CAPATM 2201, 2205, 2209, 2302, 2304, 2402 etc.

b) Polyether polyol

According to the present invention, b) at least one polyether polyol is comprised in the reaction product of the NCO-terminated polyurethane prepolymer.

The component b) used in the present invention preferably is liquid at the ambient temperature (20℃) .

As for the main reactant, useful polyether polyols are derived from oxide monomers (e.g., ethylene oxide, propylene oxide, 1, 2-butylene oxide, 1, 4-butylene oxide, tetrahydrofuran, and a combination thereof) and a polyol initiator (e.g., ethylene glycol, propylene glycol, butanediols, hexanediols, glycerols, trimethylolethane, trimethylolpropane, and pentaerythritol, and a combination thereof) .

In some embodiments, component b) can be selected from polypropylene glycol, polypropanediol, polytetramethylene ether glycol, poly (oxypropylene) glycol, polyethylene glycol, polybutene polyol, and ethylene oxide endcapped versions of any of the foregoing, and a combination thereof, preferably polyethylene glycol, polybutene polyol, and a combination thereof.

Preferably, the said polyether polyol has a number average molecular weight (Mn) of from 100 g/mol to 8000 g/mol, more preferably from 200 g/mol to 4000 g/mol, and even more preferably from 200 g/mol to 2000 g/mol.

The above-mentioned polyether polyols can be used singly or in combination with two or more thereof. If at least two polyether polyols are used in the adhesive composition, each one of number average molecular weight (Mn) preferably falls into the claimed range.

Suitable commercially available polyether polyols include Voranol^TM 2104, 2110, 2120, 2140, 4701 from Dow, Wanol c2020 and Wanol C2010D from Wanhu, DP 3070E and DP 2000E from Kukdo, Krasol HLBH P 2000 from Cray Valley, Polyvest HT from Enovik.

c) Polyisocyanate

According to the present invention, c) at least one polyisocyanate is comprised in the reaction product of the NCO-terminated polyurethane prepolymer.

Useful polyisocyanate include any suitable isocyanate having at least two isocyanate groups in one molecule including, e.g., aliphatic, cyclopaliphatic, araliphatic, arylalkyl, and aromatic isocyanates, and mixtures thereof.

Preferable polyisocyanate can be selected from 4, 4-diphenylmethane diisocyanate (MDI) , hydrogenated MDI (H12MDI) , partly hydrogenated MDI (H6MDI) , xylylene diisocyanate (XDI) , tetramethylxylylene diisocyanate (TMXDI) , 4, 4-diphenyldimethylmethane diisocyanate, dialkylenediphenylmethane diisocyanate, tetraalkylenediphenylmethane diisocyanate, 4, 4-dibenzyl diisocyanate, 1, 3-phenylene diisocyanate, 1, 4-phenylene diisocyanate, the isomers of toluylene diisocyanate (TDI) , 1-methyl-2, 4-diisocyanatocyclohexane, 1, 6-diisocyanato-2, 2, 4-trimethylhexane, 1, 6-diisocyanato-2, 4, 4-trimethylhexane, 1-isocyanatomethyl-3-isocyanato-1, 5, 5-trimethylcyclohexane (IPDI) , tetramethoxybutane-1, 4-diisocyanate, naphthalene-1, 5-diisocyanate (NDI) , butane-1, 4-diisocyanate, hexane-1, 6-diisocyanate (HDI) , dicyclohexylmethane diisocyanate, 2, 2, 4-trimethylhexane-2, 3, 3-trimethylhexamethylene diisocyanate, cyclohexane-1, 4-diisocyanate, ethylene diisocyanate, methylenetriphenyltriisocyanate (MIT) , phthalic acid bisisocyanatoethyl ester, trimethylhexamethylene diisocyanate, 1, 4-diisocyanatobutane, 1, 12-diisocyanatododecane, and dimer fatty acid diisocyanate, lysine ester diisocyanate, 4, 4-dicyclohexylmethane diisocyanate, 1, 3-cyclohexane or 1, 4-cyclohexane diisocyanate, and mixtures thereof. The most preferred polyisocyanate is 2, 2-dimorpholinodiethyl ether (MDI) and its isomers, chain-extended MDI, and a combination thereof.

Useful commercially available component c) are available under Wannate 100F from Wanhua Chemistry.

In one embodiment, the NCO-terminated polyurethane prepolymer in the polyurethane hot melt adhesive composition comprises:

a) from 1%%to 20%, preferably from 2%to 15%by weight of at least one polyester polyol,

b) from 20%to 70%, preferably from 25%to 68%by weight of at least one polyether polyol, and

c) from 7%to 40%, preferably 10%to 35%by weight of at least one polyisocyanate, all based on the total weight of the polyurethane hot melt adhesive composition.

(B) Copolyester polymer

According to the present invention, the polyurethane hot melt adhesive composition comprises from 3%to 26%by weight of at least one copolyester polymer having a number average molecular weight (Mn) of more than 10,000 g/mol and a glass temperature of less than 0℃, based on the total weight of the composition.

Useful copolyester polymers can be synthesized by diacids selected from succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid and diols selected from ethylene glycol, butanediol, 2, 2-dimethyl-1, 3-propanediol, hexanediol, 2-methyl-1, 3-propanediol, trimethylolpropane.

According to the present invention, the component (B) has a number average molecular weight (Mn) of more than 10,000 g/mol, preferably more than 15,000 g/mol to 50,000 g/mol, and more preferably from 18,000 g/mol to 50,000 g/mol. The component (B) falling within the number average molecular weight (Mn) range provides the cured product with a satisfactory tensile strength.

According to the present invention, the component (B) has a glass temperature of less than 0℃, preferably from less than 0℃ to -50℃. If the Tg of component (B) equals to or above 0℃, the component (B) may be incompatible with the formulation or the modulus of cured adhesive may be too high. This could lead to the cured adhesive being more brittle, prone to fracture, and may also increase processing difficulties.

In some embodiments, the component (B) has a linear or branched aliphatic structure, preferably a linear aliphatic structure.

In preferred embodiments, the component (B) has a functionality of at least 2, ensuring an appropriate degree of cross-linking, which results in sufficient strength and resilience in the cured product. The Functionality means the average number of hydroxy groups per molecule.

The above-mentioned copolyester polymer can be used singly or in combination with two or more thereof. If at least two copolyester polymers are used in the adhesive composition, each one of number average molecular weight (Mn) and Tg shall fall into the claimed range.

According to the present invention, the component (B) is present in an amount of from 3%to 26%, preferably from 3%to 23%by weight, based on the total weight of the composition. In case the content of the component (B) is less than 3%, the bonding strength and the resilience of the cured adhesive may be insufficient for application, while the content of the component (B) exceeds 26%, the viscosity of the adhesive composition may be too high for dispensing; in addition, the resilience may decrease with the increase of component (B) after it exceeds 26%.

(C) Additive

In addition to component (A) and (B) , the polyurethane hot melt adhesive composition according to the present invention may optionally comprise an additive that are conventionally used in the art and are compatible with the adhesive composition, for example, a moisture curing catalyst, a plasticizer, a filler, a pigment, an antioxidant, a rheological modifier, a flame retardant, an inhibitor, an adhesion promoter, a stabilizer, a tackifier, a wax, or a combination thereof.

Conventional additives that are compatible with a composition according to this invention may simply be determined by combining a potential additive with the composition and determining if they are compatible. An additive is compatible if it is homogenous within the product.

Examples of useful moisture curing catalysts include compound having ether and morpholine functional groups, include but not limited to, 2, 2’-dimorpholinoethylether, di (2, 6-dimethyl morpholinoethyl) ether, and 4, 4’- (oxydi-2, 1-ethanediyl) bis-morpholine; metal catalysts including, e.g., catalysts based on tin (e.g. dibutyltin dilaurate and dibutyltin acetate) , bismuth, zinc, potassium and combination thereof. Commercially available moisture curing catalysts are available under the following trade designations, Jeffcat DMDEE, Catalyst CC, T9, BiCAT 8 and mixture thereof.

Examples of useful antioxidants include but are not limited to hindered phenolic antioxidants, phosphite antioxidants, and thioether antioxidants.

Examples of useful fillers can be in a variety of forms including, e.g., particles (spherical particles, beads, and elongated particles) , fibers, and combinations thereof. Examples of the fillers include but are not limited to talcs, clays, silicas and treated versions thereof, carbon blacks and micas, and the like.

With particular embodiment, the additive may be present in an amount of from 0 to 20%based on the total weight of the adhesive composition.

Notably, the polyurethane hot melt adhesive composition according to the present invention does not comprise any solvent.

Notably, the polyurethane hot melt adhesive composition according to the present invention does not comprises other thermoplastic polymer different from component (B) , particularly ethylene vinyl acetate copolymers, acrylic polymer and thermoplastic polyurethane polymers.

The polyurethane hot melt adhesive composition according to the present invention has a Brookfield viscosity of from 8000 to 50,000 cps at 130℃, determined according to ASTM 1084-1997.

The polyurethane hot melt adhesive composition according to the present invention has an open time of more than 15 minutes at 22℃±2℃. "Open time" refers to the minimum required time from when adhesive is applied to when installation can begin.

The cured product of the polyurethane hot melt adhesive composition according to the present invention has an initial peel strength at 180° to polyethylene terephthalate (PET) film of more than 1 N/inch with 100%Cohesive Failure mode, preferably more than 2 N/inch with 100%Cohesive Failure mode. The test method is as follows. 50 gsm of the polyurethane hot melt adhesive composition is coated onto a PET film, covered with a release film. The laminated sample is cooled to room temperature for 24 hours. Then the release film is removed, and the polyurethane hot melt adhesive composition is adhered to a PET plate, laminated with a 2 kg roller back and forth with a speed of 100 mm/min. The laminated sample is dwelled for 15 minutes and then the 180° peel strength is tested on an Instron 3365 tensile strength tester with a speed of 100 mm/min. As referred herein, “Cohesive Failure mode” refers to that the adhesive splits and portions of the adhesive remain adhered to each of the bonded surfaces. A failure mode wherein an adhesive is removed cleanly from the substrate is referred to as “Adhesive Failure mode” . An adhesive having Cohesive Failure mode is considered to be more robust than those having Adhesive Failure mode.

The cured product of the polyurethane hot melt adhesive composition according to the present invention has a tensile strength to PET film of more than 1.5 MPa, preferably more than 2 MPa determined according to ASTM D882-02.

The polyurethane hot melt adhesive composition according to the present invention features an excellent resilient property, i.e., a shape recovery ratio of more than 96%, wherein the shape recovery ratio is calculated by dividing the recovery length of the cured product after repeating stretching and recovery for 3 times by the elongation length of the cured product before repeating.

The polyurethane hot melt adhesive composition according to the present invention features a good softness, i.e., a relatively low modulus, such as less than 30 MPa determined by ASTM D882-02.

Generally, the polyurethane hot melt adhesive composition according to the present invention are useful for bonding two substrates, especially in a garment or underwear, wherein at least one of the two substrates is textile. The other substrate may be textile or foam. Specifically, the polyurethane hot melt adhesive composition according to the present invention may be used in bonding textile to textile, or bonding textile to foam in a garment or underwear.

The polyurethane hot melt adhesive according to the present invention is heated to melt and the melted adhesive is applied onto one or both of the substrates to be bonded.

Final curing may be carried out using various conditions. In particular, curing is achieved through action of airborne moisture where the relative humidity is no less than 10%, preferably no less than 25%, more preferably no less than 50%.

The composition is typically distributed and stored in its solid form in the absence of moisture. When the composition is ready for use, the solid is heated and melted before application. Thus, this invention includes a polyurethane hot melt adhesive composition in both its solid form, as it is typically to be stored and distributed, and its liquid form, after it has been melted, just before its application.

Examples

The following examples illustrate the invention and are not intended to limit the same.

Raw materials

DYNACOLL^TM 7360 is a crystalline polyester polyol having a melting point of 55 ℃ and a number average molecular weight (Mn) of 3500 g/mol, available from Evonik.

Voranol 2120 is a polypropylene glycol having a number average molecular weight (Mn) of 2000 g/mol, available from Dow.

Voranol 2110 is a polypropylene glycol having a number average molecular weight (Mn) of 1000 g/mol, available from Dow.

Wannate 100F is MDI available from Wanhua Chemistry.

Jeffcat DMDEE is 2, 2-dimorpholinodiethyl ether, available from Huntsman.

Pearlbond 521 is a thermoplastic polyurethane available from Lubrizol.

Elvacite 4014 is an acrylic polymer available from Lucite.

Levemelt 456 is an ethylene vinyl acetate copolymer available from ARLANXEO.

Dynapol L323 is a linear copolyester polymer has a Tg of 30℃, a hydroxy functionality of 2 and a number average molecular weight (Mn) of 15,000 g/mol, available from Enovik.

S1402 is a linear copolyester polymer has a Tg of 90℃, a hydroxy functionality of 2 and a number average molecular weight (Mn) of 22,000 g/mol, available from Enovik.

MAENEX^TM AL147 is a branched copolyester polymer having a Tg of 7℃, a hydroxy functionality of 4 and a number average molecular weight (Mn) of 15,000 g/mol, available from Macroocean.

MAENEX^TM AL090M is a linear copolyester polymer having a Tg of -8℃, a hydroxy functionality of 2.25 and a number average molecular weight (Mn) of 42,000 g/mol, available from Macroocean.

BX-1001 is a linear copolyester polymer having a Tg of -18℃, a hydroxy functionality of 2 and a number average molecular weight (Mn) of 28,000 g/mol, available from Toyobo.

Sample Preparation for Comparative Examples 1 to 10 (CE1 to CE10) and Inventive Examples 1 to 5 (EX1 to EX 5)

Each adhesive composition of the comparative example and inventive example was prepared according to the formulations listed in Table 1 and 2. All components except for MDI were added in a three-neck round flask to be melted and mixed under vacuum until homogeneous and dehydrated at 130 ℃ for 2 hours. Then MDI was added to the mixture at 110 ℃, and polymerization was allowed to proceed with mixing under vacuum at 130 ℃ until the reaction was completed after 1.5 hours.

Testing method and evaluation:

Compatibility

The composition, observed as homogeneous after mixing, can be considered "compatible, " recorded as "O" ; otherwise, it is deemed "incompatible, " recorded as "X. "

Viscosity

The viscosity of each adhesive composition in the comparative example and inventive example at 130℃ was measured according to ASTM 1084-1997 using a Brookfield viscometer RVDVII equipped with a Thermosel heating unit and spindle 27, set at speeds ranging from 2.5 to 10 rpm. An adhesive composition with a Brookfield viscosity ranging from 8000 to 50000 cps at 130℃ can be deemed acceptable.

Open time

A 10cm*1 cm paper was coated with each prepolymer prepared as above by a gravure roller (X-TH13, available from Xinxin Corporation in Dongguan) at 100 to 140 ℃ with a thickness of 20 μm. A paper stripe (1.5 cm*5.0 cm) was attached to the coated paper by finger pressure every 30 seconds. The open time was defined as the time until fiber tear of the paper stripe was observed. An adhesive composition exhibiting an open time of more than 20 minutes can be deemed acceptable.

Initial Peel Strength

50 gsm of each adhesive composition of the comparative example and inventive example was coated onto PET film to form a smooth hot melt film, covered with a release film. Each sample was cooled to room temperature for 24 hours. Then the release film was removed, and the hot melt adhesive layer was adhered to a clean PET plate, laminated with a 2 kg roller back and forth with a speed of 300 mm/min. The laminated sample was dwelled for 15 mins and then the peel strength at 180° was tested on an Instron 3365 tensile strength tester with a speed of 50 mm/min. A cured adhesive exhibiting an initial peel strength of more than 1 N/inch with 100%Cohesive Failure mode (CF) can be deemed acceptable, preferably more than 2 N/inch.

Tensile Strength

The tensile strength of each adhesive composition of the comparative example and inventive example was measured according to ASTM D882-02. A cured adhesive exhibiting a tensile strength of more than 1.5 MPa can be deemed acceptable, preferably more than 2 MPa.

Modulus

The modulus of each adhesive composition of the comparative example and inventive example was measured by ASTM D882-02. Specifically, each sample was coated onto PET film to form a smooth hot melt film having a thickness of 50μm, covered with a release film. The adhesive film was cured for 7 days at 23℃ with a relative humidity of 50%. Then it was cut into adhesive strips of 10cm*1 cm. The modulus of each sample was measured by a Instron tensile machine at a speed of 100mm/min. A cured adhesive exhibiting a modulus of less than 30 MPa can be deemed an acceptable softness.

Shape recovery ratio

The shape recovery ratio was measured according to FZT70006-2021. Specifically, after each adhesive sample was cured for 7 days at 23℃ with a relative humidity of 50%, it was cut into adhesive strips of 10cm*1cm. The actual length of each strip was recorded as L0. The tensile machine was set with a pre-tension force of 0.1 N, stretched to L1 (20cm) at a speed of 100mm/min, held for 1 minute, then retracted to the original position at a speed of 100mm/min. This stretching and recovery process was repeated 3 times. After restoring the pre-tension force to 0.1 N for 30 seconds, the actual length of the adhesive strip was recorded as L2. The elongation length was calculated as (L1-L0) , the recovery length as (L1-L2) , and the shape recovery rate as (L1-L2) / (L1-L0) *100%. A cured adhesive exhibiting a shape recovery rate of more than 96%can be deemed an excellent resilience.

All the above testing results were recorded in Table 1 and 2.

As shown by the results in Table 1 and 2, the adhesive compositions prepared in Comparative Examples 1 to 4, without adding a thermoplastic polymer (CE1) or using a different type of thermoplastic polymer than the copolyester polymer (CE2 to CE4) , failed to exhibit the required shape recovery ratio or sufficient initial peel strength. Comparative Examples 5 to 7, using a copolyester polymer with a Tg outside the claimed range, either resulted in incompatibility with the adhesive or did not exhibit good softness. Comparative Example 8, with 2.35%by weight of component (B) , did not show satisfactory initial peel strength and shape recovery ratio. Comparative Examples 9 and 10, with a higher content of component (B) than the claimed range (26.5%in CE9 and 32.5%in CE10) , also did not show a good shape recovery ratio or had excessively high viscosity. In contrast, the adhesive compositions prepared in Examples 1 to 5 exhibited proper open time and viscosity, high shape recovery ratio, excellent bonding strength, as well as good modulus (softness) upon curing.

These and other modifications and variations of the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention. In addition, it should be understood that aspects of the various embodiments may be interchanged in whole or in reactant. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.

Claims

A polyurethane hot melt adhesive composition, comprising

(A) at least one NCO-terminated polyurethane prepolymer comprising the reaction product of the following components:

a) at least one polyester polyol,

b) at least one polyether polyol, and

c) at least one polyisocyanate; and

(B) at least one copolyester polymer having a number average molecular weight (Mn) of more than 10,000 g/mol and a glass temperature of less than 0℃;

wherein the component (B) is present in an amount of from 3%to 26%by weight of based on the total weight of the composition.
The polyurethane hot melt adhesive composition according to claim 1, wherein the component a) is selected from a crystalline polyester polyol, a semi-crystalline polyester polyol, a solid amorphous polyester polyol, and a combination thereof, preferably a crystalline polyester polyol or/and a semi-crystalline polyester polyol.
The polyurethane hot melt adhesive composition according to claim 2, wherein the crystalline polyester polyol or semi-crystalline polyester polyol have a melting point of less than 70℃, preferably less than 60℃.
The polyurethane hot melt adhesive composition according to any of the preceding claims, wherein the component b) is selected from polypropylene glycol, polypropanediol, polytetramethylene ether glycol, poly (oxypropylene) glycol, polyethylene glycol, polybutene polyol, and ethylene oxide endcapped versions of any of the foregoing, and a combination thereof, preferably polyethylene glycol, polybutene polyol, and a combination thereof.
The polyurethane hot melt adhesive composition according to any of the preceding claims, wherein the component c) is selected from 4, 4-diphenylmethane diisocyanate (MDI) , hydrogenated MDI (H12MDI) , partly hydrogenated MDI (H6MDI) , xylylene diisocyanate (XDI) , tetramethylxylylene diisocyanate (TMXDI) , 4, 4-diphenyldimethylmethane diisocyanate, dialkylenediphenylmethane diisocyanate, tetraalkylenediphenylmethane diisocyanate, 4, 4-dibenzyl diisocyanate, 1, 3-phenylene diisocyanate, 1, 4-phenylene diisocyanate, the isomers of toluylene diisocyanate (TDI) , 1-methyl-2, 4-diisocyanatocyclohexane, 1, 6-diisocyanato-2, 2, 4-trimethylhexane, 1, 6-diisocyanato-2, 4, 4-trimethylhexane, 1-isocyanatomethyl-3-isocyanato-1, 5, 5-trimethylcyclohexane (IPDI) , tetramethoxybutane-1, 4-diisocyanate, naphthalene-1, 5-diisocyanate (NDI) , butane-1, 4-diisocyanate, hexane-1, 6-diisocyanate (HDI) , dicyclohexylmethane diisocyanate, 2, 2, 4-trimethylhexane-2, 3, 3-trimethylhexamethylene diisocyanate, cyclohexane-1, 4-diisocyanate, ethylene diisocyanate, methylenetriphenyltriisocyanate (MIT) , phthalic acid bisisocyanatoethyl ester, trimethylhexamethylene diisocyanate, 1, 4-diisocyanatobutane, 1, 12-diisocyanatododecane, and dimer fatty acid diisocyanate, lysine ester diisocyanate, 4, 4-dicyclohexylmethane diisocyanate, 1, 3-cyclohexane or 1, 4-cyclohexane diisocyanate, and mixtures thereof, preferably 2, 2-dimorpholinodiethyl ether (MDI) and its isomers, chain-extended MDI, and a combination thereof.
The polyurethane hot melt adhesive composition according to any of the preceding claims, the composition has an NCO/OH ratio, which is a molar ratio of the NCO group of component c) to the total OH groups of components a) and b) , is more than 1, preferably from 1.5 to 2.5.
The polyurethane hot melt adhesive composition according to any of the preceding claims, wherein the component (B) has a number average molecular weight (Mn) of more than 15,000 g/mol to 50,000 g/mol, more preferably from 18,000 g/mol to 50,000 g/mol.
The polyurethane hot melt adhesive composition according to any of the preceding claims, wherein the component (B) has a functionality of at least 2.
The polyurethane hot melt adhesive composition according to any of the preceding claims, wherein the component (A) is present in an amount of from 54%to 97%by weight, preferably from 74%to 97%by weight, based on the total weight of the adhesive composition.
The polyurethane hot melt adhesive composition according to any of the preceding claims, wherein the adhesive composition further comprises from 0 to 20%by weight of (C) an additive selected from a moisture curing catalyst, a plasticizer, a filler, a pigment, an antioxidant, a rheological modifier, a flame retardant, an inhibitor, an adhesion promoter, a stabilizer, a tackifier, a wax, and a combination thereof.
Cured product of the polyurethane hot melt adhesive composition according to any one of the claims 1 to 10.
The cured product according to claim 11, having a shape recovery ratio of more than 96%, wherein the shape recovery ratio is calculated by dividing the recovery length of the cured product after repeating stretching and recovery for 3 times by the elongation length of the cured product before repeating.
Use of the polyurethane hot melt adhesive composition according to any of claims 1 to 10 for bonding two substrates, especially in a garment or underwear, wherein at least one of the two substrates is textile.