WO2024199453A1

WO2024199453A1 - Reactive polyurethane hot-melt adhesive composition and article

Info

Publication number: WO2024199453A1
Application number: PCT/CN2024/084848
Authority: WO
Inventors: Eric Cao; Chengliang JIA
Original assignee: Shanghai Zhiguan Polymer Materials Co Ltd
Current assignee: Shanghai Zhiguan Polymer Materials Co Ltd
Priority date: 2023-03-31
Filing date: 2024-03-29
Publication date: 2024-10-03
Anticipated expiration: 2025-09-30
Also published as: CN121100161A

Abstract

The present invention relates to a reactive polyurethane hot-melt adhesive composition and an article comprising an adhesive layer formed therefrom. The reactive polyurethane hot-melt adhesive composition is prepared by a raw material comprising the following components: component (A) comprising at least one polyether polyol; component (B) comprising at least one crystalline polyester polyol (B1) and at least one non-crystalline polyester polyol (B2); component (C) comprising at least one acrylic resin (C1), the acrylic resin (C1) comprising an active functional group which is reactive with an isocyanate group, and having a number average D90 particle size of no greater than 350 μm; and component (D) comprising at least one polyisocyanate, wherein the equivalent ratio of the isocyanate groups to hydroxyl groups (NCO/OH) of the above components is from 1.2 to 6.

Description

REACTIVE POLYURETHANE HOT-MELT ADHESIVE COMPOSITION AND ARTICLE

TECHNICAL FIELD

The present invention relates to a reactive polyurethane hot-melt adhesive composition, with good workability, especially suitable for the field of electronic assembly. The present invention also relates to an article produced by applying the adhesive composition.

BACKGROUND

Reactive polyurethane hot-melt adhesive ( “HMPUR” , hereinafter abbreviated as “hot-melt adhesive” ) generally comprises a urethane pre-polymer terminated with an isocyanate group as a main component, is coated when being heated to a molten state, has a certain initial tack, and produces a stronger adhesion after reacting with moisture in the air or on the surface of a substrate or other active hydrogen containing substances for curing. The reactive polyurethane hot-melt adhesive has been widely used in various industries, e.g. bookbinding, shoes and clothing making, wood panel processing, automotive interiors, and electronics industry.

The reactive polyurethane hot-melt adhesive has advantages of solvent-free, good flowability, high sizing efficiency, one component without need for glue preparation, rapid curing of an adhesive layer, low hot-shrinkage rate, low density, uniform stress transfer, easy adjustment of opening time, and the like, and at the same time, exhibits good adhesive strength to metal material of stainless steel, aluminum, and the like, as well as materials of ABS plastic, polycarbonate (PC) , glass, and the like. Therefore, the reactive polyurethane hot-melt adhesive is particularly suitable for electronic assembly production line which is developing towards miniaturization, lightweight and efficient densification.

The current electronic assembly production line commonly employs jetting technology with high production efficiency, which ejects the hot-melt adhesive at a high speed and in a small amount using piezoelectric jetting dispensing valve to achieve a precise dispensing or an accurate filling. The precise piezoelectric injection dispensing valve ususally has a small glue dispensing force and a small nozzle diameter (less than 0.5 mm, and even less than 0.2 mm) . Accordingly, there are high requirements for viscosity, compatibility and flowability of the hot-melt adhesive, which needs to be ejected smoothly and maintain a certain shape. However, in practice, there are often problems that the hot-melt adhesive cannot be ejected normally from the piezoelectric injection dispensing valve, the nozzle is clogged, and the like. Further, during jetting/dispensing, the hot-melt adhesive is heated to the molten state, which easily adheres to the nozzle of the piezoelectric jetting system, resulting in frequent shutdown and cleaning, which greatly affects the production efficiency. In addition, in the assembly of a precise electronic device, the amount of an adhesive used in each site is often small, and one hot-melt adhesive (typically packaged in a syringe, with 30 ml each) often needs to be used in the molten state for a long time, so the hot melt adhesive needs to have good thermal stability.

In view of the above issues regarding jetting of the hot-melt adhesive in the current electronic assembly industry, there is need for a reactive polyurethane hot-melt adhesive with good dispensing performance and high thermal stability.

SUMMARY

The present invention provides a reactive polyurethane hot-melt adhesive composition prepared by a raw material comprising the following components:

component (A) comprising at least one polyether polyol;

component (B) comprising at least one crystalline polyester polyol (B1) and at least one non-crystalline polyester polyol (B2) ;

component (C) comprising at least one acrylic resin (C1) , the acrylic resin (C1) comprising an active functional group which is reactive with an isocyanate group, the acrylic resin (C1) having a number average D90 particle size of no greater than 350 μm; and

component (D) comprising at least one polyisocyanate,

wherein the equivalent ratio of the isocyanate groups to hydroxyl groups (NCO/OH) of the above components is from 1.2 to 6, preferably from 1.5 to 5, and more preferably from 1.7 to 3.

Preferably, the acrylic resin (C1) has a number average D90 particle size of no greater than 250 μm, more preferably no greater than 210 μm, even more preferably in a range of from 100 μm to 210 μm, most preferably in a range of from 120 μm to 200 μm.

Extremely preferably, the acrylic resin (C1) has a number average D90 particle size in a range of 160-200 μm.

Preferably, the acrylic resin (C1) has a glass transition temperature (Tg) of 30 to 110 ℃, preferably of 40 to 80 ℃, more preferably of 45 to 58 ℃.

In an embodiment, the active functional group which is reactive with an isocyanate group comprises one or two of hydroxyl group and amino group.

In an embodiment, the acrylic resin (C1) has a hydroxyl value ranging from 1 to 10 mg KOH/g, preferably from 2 to 10 mg KOH/g, and more preferably from 4 to 10 mg KOH/g.

In an embodiment, the acrylic resin (C1) has a weight average molecular weight in a range of 3,000 to 80,000 g/mol, preferably from 5,000 to 60,000 g/mol, and more preferably from 5,000 to 50,000 g/mol.

In an embodiment, the content of the acrylic resin (C1) is in a range of 3 to 25 wt%, preferably from 5 to 20 wt%, and more preferably from 5 to 15 wt%, based on the total weight of the components (A) to (D) .

In an embodiment, the component (C) further comprises at least one acrylic resin (C2) , and the acrylic resin (C2) is substantially free of the active functional group which is reactive with an isocyanate group.

In an embodiment, the weight ratio of the crystalline polyester polyol (B1) to the non-crystalline polyester polyol (B2) is in a range of 1: 9 to 9: 1, preferably from 1: 9 to 5: 1, and more preferably from 1: 9 to 3: 1, most preferably from 1: 3 to 3: 1.

In an embodiment, the component (A) , the component (B) , and the component (C) are substantially free of an aromatic compound.

In an embodiment, the at least one polyisocyanate is an aromatic polyisocyanate.

In an embodiment, the component (A) , the component (B) , the component (C) , and the component (D) comprise at least one partially or fully bio-based material.

In an embodiment, the composition has a bio-based content of 10%or greater, preferably 30%or greater, and more preferably 40%or greater, the bio-based content being determined according to ASTM D6866.

In an embodiment, the composition has a viscosity at 100 ℃ in a range of from 1,500 to 10,000 mPa. s, preferably in a range of from 1,500 to 8,000 mPa. s, and more preferably in a range of from 1,500 to 5,000 mPa. s.

The present invention further provides an article, comprising a first substrate and an adhesive layer disposed on the first substrate formed by curing the reactive polyurethane hot-melt adhesive composition.

In an embodiment, the adhesive layer has a thickness in a range of from 0.01 to 2 mm, preferably in a range of from 0.05 to 1 mm, and more preferably in a range of from 0.1 to 0.5 mm.

In an embodiment, the adhesive layer is formed by coating the reactive polyurethane hot-melt adhesive composition on the first substrate through a piezoelectric injection system and curing the resultant.

The present invention further provides use of acrylic resin in reactive polyurethane hot-melt adhesive composition according to the present invention for improving dispensing performance, wherein the acrylic resin is acrylic resin (C1) according to the invention.

In an embodiment, the composition has a total time of nozzle-clog of less than 5, preferably less than 3.

DETAILED DESCRIPTION

In the present invention, a “polyester polyol” includes a polycaprolactone polyol, a polycarbonate polyol, and a product obtained by condensation reaction between a polyhydroxy compound and a polybasic acid. As for the reactants in the aforementioned condensation reaction, the polyhydroxy compound may be, for example, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptadiol, octanediol, nonanediol, decanediol, trimethylolpropane, trimethylolethane, glycerol, and the like, which can be used alone or in combination of two or more thereof; and the polybasic acid is preferably a diacid, which may be, for example, oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, 1, 12-decanedicarboxylic acid, and the like. The aforementioned polycaprolactone polyol can be obtained by reaction of a compound having a hydroxyl group with ε-caprolactone. The polyester polyol can be divided into an aliphatic polyester polyol and an aromatic polyester polyol, according to whether it contains a benzene ring structure or not.

In the present invention, a “crystalline polyester polyol” refers to a polyester polyol with a crystallinity of higher than 10%, including a semi-crystalline polyester polyol. A “non-crystalline polyester polyol” refers to a polyester polyol with a crystallinity of lower than 10%, including an amorphous polyester polyol. A “crystallinity” refers to a proportion of a crystalline region in a polymer, expressed in percentage. In the present invention, the crystallinity is determined by a wide-angle X-ray diffraction (WAXD) method. Specifically, by integration based on the WAXD diffraction spectrum, the crystallinity (%) is equal to a ratio of a crystalline diffraction peak area to the sum of the crystalline diffraction peak area and a non-crystalline diffraction peak area multiplied by 100%. The crystallinity is determined by a Bruker D8 ADVANCE DaVinci X-ray diffractometer in the present invention.

In the present invention, a “number average D90 particle size” represents a particle size corresponding to 90%in a cumulative particle size distribution number, and the number of particles whose particle size is less than D90 accounts for 90%of the total sample. The number average D90 particle size herein is determined using a laser particle size analyzer Microtrac S3500 utilizing a wet method (ethanol as carrier) .

In the present invention, a viscosity is determined at 110 ℃ using a DVT-II type Brookfield viscometer utilizing a 27 #rotor.

The reactive polyurethane hot-melt adhesive composition and the articles including an adhesive layer formed therefrom according to the embodiments will be described in detail hereinafter.

In an aspect, the present invention relates to a reactive polyurethane hot-melt adhesive composition prepared by a raw material comprising the following components: component (A) comprising at least one polyether polyol; component (B) comprising at least one crystalline polyester polyol (B1) and at least one non-crystalline polyester polyol (B2) ; component (C) comprising at least one acrylic resin (C1) , the acrylic resin (C1) comprising an active functional group which is reactive with an isocyanate group, the acrylic resin (C1) having a number average D90 particle size of no greater than 350 μm; and component (D) comprising at least one polyisocyanate, wherein the equivalent ratio of the isocyanate groups to hydroxyl groups (NCO/OH) of the above components is from 1.2 to 6, preferably from 1.5 to 5, and more preferably from 1.7 to 3.

Preferably, the present invention relates to a reactive polyurethane hot-melt adhesive composition prepared by a raw material comprising the following components: component (A) comprising at least one polyether polyol; component (B) comprising at least one crystalline polyester polyol (B1) and at least one non-crystalline polyester polyol (B2) ; component (C) comprising at least one acrylic resin (C1) , the acrylic resin (C1) comprising an active functional group which is reactive with an isocyanate group, the acrylic resin (C1) having a number average D90 particle size of no greater than 210 μm, preferably in a range of from 100 μm to 210 μm, and more preferably in a range of from 120 μm to 200 μm; and component (D) comprising at least one polyisocyanate, wherein the equivalent ratio of the isocyanate groups to hydroxyl groups (NCO/OH) of the above components is from 1.2 to 6, preferably from 1.5 to 5, and more preferably from 1.7 to 3.

Surprisingly, the inventors found that when preparing the reactive polyurethane hot melt adhesive composition, use of the polyether polyol, the crystalline polyester polyol, the non-crystalline polyester polyol, the acrylic resin comprising the active functional group within the specific particle size range, and the polyisocyanate in combination enables a reactive polyurethane hot-melt adhesive with excellent initial tack, bonding strength, and thermal stability, and more importantly, with excellent dispensing performance, for example, when using a piezoelectric injection system for jetting/dispensing, the dispensing is smooth, and the nozzle is not prone to be clogged by the adhesive, making it suitable for application in the electronic industry assembly line.

In the present invention, the component (A) comprises at least one polyether polyol. The polyether polyol includes any polyether polyol available in the art. In an embodiment, the polyether polyol includes a polymer or oligomer formed from one or more monomers selected from ethylene oxide, propylene oxide, 1, 2-epoxybutane, 1, 4- epoxybutane, and mixtures thereof, or a polymer or oligomer formed from an alkylene glycol. The alkylene glycol generally has 3 or more carbon atoms, such as propylene glycol or butanediol. From the perspective of the initial tack and bonding strength of the desired hot-melt adhesive, the number average molecular weight of the polyether polyol is preferably in a range of 200-8,000 g/mol, more preferably in a range of 500-5,000 g/mol, even more preferably in a range of 700-3,000 g/mol, more advantageously in a range of 1,500-2,500 g/mol, and especially 2,000 g/mol. Preferably, the polyether polyol comprises a homopolymer of propylene oxide with a number average molecular weight ranging from 500 to 5,000 g/mol. The polyether polyol can be commercially available, such as Voranol series from Dow Chemical Company, and Wanol series from Wanhua.

The component (A) may comprise one or two or more polyether polyols, such as two polyether polyols with different number average molecular weights.

The content of the component (A) is preferably in a range of 15-35 wt%, more preferably in a range of 18-30 wt%, even more preferably in a range of 20-29 wt%, and more advantageously in a range of 23-29 wt%, based on the total weight of the components (A) to (D) .

In the present invention, the component (B) comprises at least one crystalline polyester polyol (B1) and at least one non-crystalline polyester polyol (B2) .

The crystalline polyester polyol (B1) includes any crystalline polyester polyol available in the art. In an embodiment, the polyester polyol (B1) generally has a melting point in a range of 40 ℃ to 120 ℃, preferably 45 ℃ to 100 ℃, and more preferably 48 ℃ to 80 ℃. In an embodiment, the polyester polyol (B1) is prepared by condensation reaction between at least one diol selected from butanediol, hexanediol, octanediol, and decanediol, and at least one diacid selected from adipic acid, sebacic acid, dodecanedioic acid, and terephthalic acid. The number average molecular weight of the polyester polyol (B1) is preferably in a range of 1,500 to 10,000 g/mol, more preferably in a range of 1,500 to 8,000 g/mol, even more preferably in a range of 1,500 to 6,000 g/mol, more advantageously in a range of 1,500 to 4,000 g/mol, and especially in a range of 1,500 to 3,500 g/mol.

The component (B) may comprise one or two or more crystalline polyester polyols (B1) . Commercially available crystalline polyester polyols (B1) include7360, 7361, 7380, 7750, and the like from Evonik, Wanthanol series from Yantai Wanhua Corporation, NL2000D from Mitsubishi, Capa series from Perstorp, and the like.

The polyester polyol (B2) is a non-crystalline polyester polyol. The non-crystalline polyester polyol has a crystallinity of less than 10%and has no melting point, including but not limited to an amorphous polyester polyol. The non-crystalline polyester polyol includes any non-crystalline polyester polyol available in the art. In one embodiment, the non-crystalline polyester polyol is obtained by reacting a carboxylic acid (an aromatic carboxylic acid and/or an aliphatic carboxylic acid) with an aliphatic polyol, preferably by reacting an aliphatic diol with an aromatic dicarboxylic acid. In another embodiment, the non-crystalline polyester polyol includes an amorphous polycarbonate polyol. The number average molecular weight of the polyester polyol (B2) is preferably in a range of 1,000 to 8,000 g/mol, more preferably in a range of 1,500 to 7,000 g/mol, even more preferably in a range of 1,600 to 6,000 g/mol, more advantageously in a range of 1,800 to 4,000 g/mol, particularly in a range of 1,900 to 3,000 g/mol, and especially 2,000 g/mol.

The component (B) may comprise one or two or more non-crystalline polyester polyols (B2) . Commercially available non-crystalline polyester polyol (B2) includes 7110, 7130, 7140, and the like from Evonik, Priplast series from Cargill/Croda, amorphous polyester polyols in Desmophen series from Covestro, Stepapol series from Stepan, and the like.

Preferably, the component (B) is composed of the at least one crystalline polyester polyol (B1) and the at least one non-crystalline polyester polyol (B2) .

The content of the component (B) is preferably in a range of 15-60 wt%, more preferably in a range of 25-55 wt%, and more advantageously in a range of 35-52 wt%, based on the total weight of the components (A) to (D) .

In the component (B) , a weight ratio of the crystalline polyester polyol (B1) to the non-crystalline polyester polyol (B2) is not particularly limited. Preferably, the weight ratio of the crystalline polyester polyol (B1) to the non-crystalline polyester polyol (B2) is in a range of 1: 9 to 9: 1, more preferably in a range of 1: 9 to 5: 1, and even more preferably 1: 9 to 3: 1, most preferably from in a range of 1: 3 to 3: 1, for example, 1: 4 to 4: 1, 1: 3 to 3: 1, 1: 2 to 2: 1.

In the present invention, the component (C) comprises at least one acrylic resin (C1) . The acrylic resin (C1) comprises an active functional group which is reactive with an isocyanate group, and its number average D90 particle size is no greater than 350 μm.Preferably, its number average D90 particle size is no greater than 250 μm, preferably no greater than 210 μm, more preferably in a range of 100-210 μm, most preferably in a range of 120-200 μm, extremely preferably in a range of 160-200 μm. For example, the acrylic resin (C1) has a number average D90 particle size of 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210 μm.

The active functional group which is reactive with an isocyanate group includes hydroxyl group, amino group, and the other functional groups having active hydrogen. Preferably, the active functional group which is reactive with an isocyanate group comprises one or two of hydroxyl group and amino group, and more preferably comprises the hydroxyl group, that is, the acrylic resin (C1) contains the hydroxyl functional group. When preparing the adhesive composition of the invention, the active functional group contained in the acrylic resin (C1) may react with the polyisocyanate in the component (D) to form a pre-polymer with a urethane structure, but it cannot be ensured that all the acrylic resin (C1) will form the pre-polymer with the urethane structure.

The acrylic resin (C1) is present in the form of extremely small particle or powder. The shape of the particle is not particularly limited, and can include, for example, spherical shape, ellipsoidal shape, and the like.

The inventors found that by adding the acrylic resin containing the active functional group and having the number average D90 particle size within the specific range when preparing the reactive polyurethane hot melt adhesive composition, the dispensing/jetting performance of the composition can be significantly improved, for example, the dispensing is smooth, the nozzle is not prone to be clogged, and the phenomenon of nozzle-clog is not prone to occur. Without being bounded by theory, the inventors believe that the acrylic resin that meets the above two requirements is well compatible with the other components in the system, and thus the adhesive composition prepared has excellent flowability and workability.

Preferably, the acrylic resin (C1) has a hydroxyl value ranging from 1 to 10 mg KOH/g, more preferably from 2 to 10 mg KOH/g, and even more preferably from 4 to 10 mg KOH/g, e.g., 5, 6, 7, 8, 9, 10 mg KOH/g.

The acrylic resin (C1) can be obtained by polymerizing a hydroxyl-containing (meth) acrylic compound as a constituent monomer and optionally the other (meth) acrylic compound. In the present invention, “ (meth) acrylic compound” represents one or both of methacrylic compound and acrylic compound. Examples of the hydroxyl-containing (meth) acrylic compounds include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and the like. Examples of the other (meth) acrylic compound include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylic acid, and the like.

The acrylic resin (C1) has preferably a weight average molecular weight in a range of 3,000 to 80,000 g/mol, more preferably from 5,000 to 60,000 g/mol, and even more preferably from 5,000 to 50,000 g/mol, e.g., 15,000, 25,000, 30,000, 35,000, 40,000, 45,000 g/mol.

The content of the acrylic resin (C1) is preferably in a range of from 3 to 25 wt%, more preferably from 5 to 20 wt%, and even more preferably from 5 wt%to 15 wt%, based on the total weight of the components (A) to (D) .

The acrylic resin (C1) has preferably a glass transition temperature (Tg) of 30 to 110 ℃, preferably 40 to 80 ℃, more preferably 45 to 58 ℃, e.g., 45, 50, 53, 55, 56, 57, 58, 59, 60, 62, 65, 68, 70, 72, 75, 78, 80 ℃. The acrylic resin (C1) with a preferable Tg is beneficial for the composition with a favorable compatibility. The glass transition temperature could be tested in a way conventionally in the art, e.g., the differential scanning calorimetry (DSC) method with heating rate of about 10 ℃/min.

In some embodiment, the acrylic resin has a number average D90 particle size of no greater than 350 μm, with Tg of 30 to 110 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size of no greater than 250 μm, with Tg of 30 to 110 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size of no greater than 210 μm, with Tg of 30 to 110 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size in a range of from 100 μm to 210 μm, with Tg of 30 to 110 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size in a range of from 120 μm to 210 μm, with Tg of 30 to 110 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size in a range of from 160 μm to 210 μm, with Tg of 30 to 110 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size of no greater than 350 μm, with Tg of 40 to 80 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size of no greater than 250 μm, with Tg of 40 to 80 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size of no greater than 210 μm, with Tg of 40 to 80 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size of from 100 μm to 210 μm, with Tg of 40 to 80 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size of from 120 μm to 200 μm, with Tg of 40 to 80 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size in a range of from 160 μm to 210 μm, with Tg of 40 to 80 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size of no greater than 350 μm, with Tg of 45 to 58 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size of no greater than 250 μm, with Tg of 45 to 58 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size of no greater than 210 μm, with Tg of 45 to 58 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size of from 100 μm to 210 μm, with Tg of 45 to 58 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size of from 120 μm to 200 μm, with Tg of 45 to 58 ℃.

In some embodiment, the acrylic resin has a number average D90 particle size in a range of from 160 μm to 210 μm, with Tg of 45 to 58 ℃.

The component (C) may further comprise at least one acrylic resin (C2) which is substantially free of the active functional group which is reactive with an isocyanate group. The expression “substantially free of” means that the acrylic resin (C2) contains less than 5 wt%, preferably less than 3 wt%, and more preferably less than 1 wt%of the active functional group which is reactive with an isocyanate group. The difference between the acrylic resins (C1) and (C2) lies in whether it contains the active functional group which is reactive with an isocyanate group. When preparing the adhesive composition of the present invention, the acrylic resin (C2) does not react with the polyisocyanate in the component (D) , and thus the acrylic resin (C2) will exist in the resulting composition. The weight average molecular weight of the acrylic resin (C2) is not particularly limited, and the acrylic resin (C2) with an appropriate molecular weight can be generally selected in order to obtain a desired viscosity from the prepared composition.

Preferably, the component (C) may be composed of the acrylic resin (C1) or be composed of the acrylic resin (C1) and the acrylic resin (C2) .

When the component (C) comprises the acrylic resin (C1) and the acrylic resin (C2) , a ratio of the acrylic resin (C1) to the acrylic resin (C2) is not particularly limited, and may be, for example, in a range of 1: 9 to 9: 1, 2: 8 to 8: 2, 3: 7 to 7: 3, or 4: 6 to 6: 4, by weight.

In the present invention, the component (D) comprises at least one polyisocyanate. The polyisocyanate includes an isocyanate compound having two or more isocyanate groups (-NCO) , as well as oligomers or polymers formed therefrom, such as trimers. The polyisocyanate may be aliphatic, aromatic, or mixtures thereof. The polyisocyanate may also comprise other substituents which do not significantly and adversely affect the performance of the composition of the present invention such as viscosity or adhesion. Examples of the polyisocyanate include: diphenylmethane diisocyanate compounds (MDI) and their isomers, diphenylmethane 4, 4’-diisocyanate, diphenylmethane-2, 2’-diisocyanate, diphenylmethane-2, 4’-diisocyanate, and other oligomeric methylene isocyanates; toluene diisocyanate compounds (TDI) including their isomers, isophorone diisocyanates, and hydrogenated aromatic diisocyanates. The at least one polyisocyanate in the component (D) is preferably an aromatic polyisocyanate, more preferably a linear aromatic isocyanate compound. Without being bounded by theory, the inventors believe that use of the aromatic polyisocyanate in the component (D) can make the adhesive composition of the present invention have good bonding strength and heat resistance.

The content of the component (D) is preferably in a range of 12-30 wt%, more preferably 15-25 wt%, even more preferably 16-23 wt%, and more advantageously 17-20 wt%, based on the total weight of the components (A) to (D) .

In the process of preparing the composition of the invention using the components (A) to (D) , the hydroxyl group and/or the other active functional group in the components (A) to (C) will react with the isocyanate group in component (D) to generate a pre-polymer with a urethane structure. In the components (A) to (D) of the present invention, the equivalent ratio of the isocyanate groups to the hydroxyl groups (NCO/OH) is from 1.2 to 6, preferably from 1.5 to 5, and more preferably from 1.7 to 3, to provide an adhesive composition containing the isocyanate group. In some embodiments of the present invention, the adhesive composition has a free NCO content of 3%to 4%, and preferably 3.1%to 3.6%. The free NCO refers to the remaining isocyanate group after the components (A) to (D) are mixed and the isocyanate groups react with the hydroxyl groups at the equivalent ratio of 1: 1. The “free NCO content” is a weight percentage of the isocyanate groups present in the adhesive composition based on 100 wt%of the total weight of the composition, and can be used to characterize the effectiveness of the reactive polyurethane hot-melt adhesive. A higher free NCO content means that the adhesive composition of the present invention has a higher degree of crosslinking after curing, and thus has better heat resistance and creep resistance.

According to an embodiment of the present invention, the component (A) , the component (B) , and the component (C) for preparing the reactive polyurethane hot-melt adhesive composition of the present invention are substantially free of an aromatic compound. The expression “substantially free of an aromatic compound” means that the content of the aromatic compound in the component (A) , the component (B) , and the component (C) is less than 5 wt%, preferably less than 3 wt%, more preferably less than 1 wt%, and especially 0 wt%. The component (A) , the component (B) , and the component (C) preferably use an aliphatic or alicyclic compound, that is, completely free of an aromatic compound. Without being bounded by theory, the inventors believe that absence of the aromatic compound in the component (A) , the component (B) , and the component (C) enable the adhesive composition of the present invention to have good flexibility and wettability.

According to an embodiment of the present invention, the component (A) , the component (B) , and the component (C) for preparing the reactive polyurethane hot-melt adhesive composition of the present invention are substantially free of the aromatic compound, and the component (D) comprises at least one aromatic polyisocyanate.

In addition to the product obtained by mixing the components (A) to (D) , the reactive polyurethane hot melt adhesive composition of the present invention may comprise the following optional components, provided that presence of these components does not adversely affect the physical performance of the adhesive composition of the present invention such as initial tak, thermal stability, and the like: catalysts, antioxidants, tackifiers, plasticizers, stabilizers, UV absorbers, fillers, dyes, pigments, fluorescent agents, deodorants, adhesion promoters (such as silane coupling agents) , surfactants, defoamers, waxes, thermoplastic resins, and the like. Examples of the catalysts include, but are not limited to, nitrogen-containing compounds such as triethylamine, triethylenediamine, and N-methylmorpholine; metal salts such as potassium acetate, zinc stearate, and tin octanoate; and organometallic compounds such as dibutyltin dilaurate. Preferably, the catalysts comprise ether and morpholine functional groups, such as 2, 2-dimorpholinyl ethyl ether, di (2, 6-dimethylmorpholinyl ethyl) ether, and 4, 4’- (oxy-di-2, 1-ethanediyl) bis-morpholine (DMDEE) . The amount of the catalysts added is in a range of 0.01-2 wt%, based on the total weight of the adhesive composition. The addition of the antioxidants can protect the adhesive composition from degradation induced by, for example, heat, light or residual catalysts in the raw material. The antioxidants may be hindered phenolic antioxidants, phosphite antioxidants, thioether antioxidants, and the like. Examples of commercially available antioxidants include Irganox 565, 1010, and 1076 from Ciba Corporation. The fillers include talc, clay, silica and their treated forms, carbon black, and mica.

According to an embodiment of the present invention, the component (A) , the component (B) , the component (C) , and the component (D) for preparing the reactive polyurethane hot-melt adhesive composition of the present invention comprise at least one partially or fully bio-based material. The partially or fully bio-based material refers to a material having a bio-based content of 0.1%or greater, the bio-based content of each component being determined according to ASTM D6866. At present, there are more and more bio-based raw materials available on the market. For example, bio-based polyether polyols include ECOPROL H500, H1000, and H2000 from SK Corporation; bio-based crystalline polyester polyols include Dynacoll Terra from Evonik Corporation and Benebiol series from Mitshubishi Chem; bio-based non-crystalline polyester polyols include Priplast 3238 and Priplast 1838 from Cargill Corporation; and bio-based polyisocyanates includeeco N7300 from Covestro Corporation. For example, the bio-based crystalline polyester polyol (s) used in the present invention has a bio-based content of 80%, preferably 90%or even higher. The bio-based amorphous polyester polyol (s) used in the present invention has a bio-based content of 80%, preferably 90%or even higher.

The reactive polyurethane hot-melt adhesive composition of the present invention may be bio-based. Preferably, its bio-based content is 10%or greater, preferably 30%or greater, and more preferably 40%or greater, e.g., 30%, 35%, 40%, 45%, 50%, the bio-based content being determined according to ASTM D6866. More specifically, the bio-based content of each component being determined according to ASTM D6866, the bio-based content of the composition is the sum of (bio-based content of every component× the weight percentages of the component in the composition) .

The reactive polyurethane hot-melt adhesive composition of the invention has typically a viscosity suitable for coating. Specifically, its viscosity at 110 ℃ is in a range of 1,500-10,000 mPa. s, preferably in a range of 1,500-8,000 mPa. s, and more preferably in a range of 1,500-5,000 mPa. s, wherein the viscosity is determined using a DVT-II type Brookfield viscometer utilizing a 27 #rotor.

Preferably, the reactive polyurethane hot melt adhesive composition is prepared by a raw material comprising the following components:

- from 15 to 35 %by weight of component (A) as defined above,

- from 15%to 60%by weight of component (B) as defined above,

- from 3%to 25 %by weight of component (C1) as defined above,

- from 12 %to 30%by weight of component (D) as defined above,

wherein the equivalent ratio of the isocyanate groups to hydroxyl groups (NCO/OH) of the above components is from 1.2 to 6.

More preferably, the reactive polyurethane hot melt adhesive composition is prepared by a raw material comprising the following components:

- from 18%to 30 %by weight of component (A) as defined above,

- from 25%to 55%by weight of component (B) as defined above,

- from 5%to 20 %by weight of component (C1) as defined above,

- from 15 %to 25%by weight of component (D) as defined above,

Even more preferably, the reactive polyurethane hot melt adhesive composition is prepared by a raw material comprising the following components:

- from 20%to 29 %by weight of component (A) as defined above,

- from 35%to 52%by weight of component (B) as defined above,

- from 5%to 15 %by weight of component (C1) as defined above,

- from 16 %to 23%by weight of component (D) as defined above,

With regard to the preparation of the reactive polyurethane hot-melt adhesive composition of the invention, in an embodiment, it may be carried out in the following way: pre-mixing the components (A) , (B) , and (C) , dehydrating, adding the component (D) while heating for reaction, and then adding the optional additives, fillers, and the like, to prepare the adhesive composition. The adhesive composition may be packaged in a moisture-proof container, such as a high-temperature resistant plastic needle tube. The above reaction process is usually carried out under a solvent-free condition, but it can also be carried out in an organic solvent (such as ethyl acetate, toluene, and the like) . In the case of using the organic solvent, the preparation method further comprises a step of removing the organic solvent, so that the prepared pre-polymer with the urethane structure does not contain the organic solvent.

An application method of the reactive polyurethane hot-melt adhesive composition of the invention includes: firstly, heating and melting the reactive polyurethane hot-melt adhesive composition of the invention in a temperature range of 50-130 ℃, coating it on a first substrate; attaching a second substrate to the composition; and selecting to apply a pressure to bonding the first substrate and the second substrate or not according to need. Coating the adhesive composition of the present invention on the first substrate may be carried out on a flat surface or in a narrow groove. The above coating may be performed, for example, using a roller coater, a spray coater, a T-shaped die coater, a blade coater, a comma coater, or the like, or may also be performed by means of distribution, inkjet printing, screen printing, offset printing, or the like. The composition of the present invention is particularly suitable for coating using a piezoelectric injection system. When coating, the moisture curable polyurethane hot-melt resin composition of the present invention may be continuously or discontinuously formed on a component in various shapes such as dot, line, triangle, quadrangle, circle, curve, or the like.

The reactive polyurethane hot-melt adhesive composition of the present invention can achieve excellent application performance, while having good initial tack (Green Strength, bonding strength before curing) , bonding strength after curing, aging resistance, heat resistance and excellent opening time. In particular, because the reactive polyurethane hot-melt adhesive composition of the invention dispenses smoothly during jetting coating, and is not prone to clog the nozzle and is not prone to occur nozzle-clog, it is particularly suitable for use in a precise assembly line of the electronic industry and contributes to improve production efficiency.

Another aspect of the present invention provides an article, comprising a first substrate and an adhesive layer on the first substrate formed by curing the reactive polyurethane hot-melt adhesive composition of the present invention. In an embodiment, the article comprises the first substrate, a second substrate, and the adhesive layer between the first substrate and the second substrate formed by curing the reactive polyurethane hot-melt adhesive composition of the present invention. The first substrate and the second substrate are each respectively selected from various materials such as metal, glass, inorganic building material, plastic, fiber, composite material, and the like. The substrate may be subjected to corona treatment, plasma treatment, primer treatment, or the like, as desired. The thickness of the adhesive layer can be set according to specific application needs. In an embodiment, the adhesive layer is coated onto the first substrate by dispensing the reactive polyurethane hot-melt adhesive composition of the present invention via jetting/dispensing. The adhesive layer has preferably the thickness in a range of from 0.01 to 2 mm, more preferably in a range of from 0.05 to 1 mm, and even more preferably in a range of from 0.1 to 0.5 mm. In an embodiment, the adhesive layer is formed by coating the reactive polyurethane hot-melt adhesive composition of the present invention on the first substrate through a piezoelectric injection system and then curing. The article of the present invention includes, but is not limited to, various electronic devices, such as mobile phone, computer, headphone, television, camera, automotive electronic component, and the like.

A further aspect of the present invention provides use of acrylic resin (C1) according to the present invention in reactive polyurethane hot-melt adhesive composition according to the invention for improving dispensing performance.

The dispensing performance could be evaluated by Nozzle-clog test. Nozzle-clog test could be performed as follows: A VERMES MDC3200 glue dispenser was used for continuous glue dispensing, and a nozzle with a diameter of 0.1 mm was selected. The glue dispensing was performed for 5 s. After that, there was an interval of 5 s, and then the glue dispensing was performed for 5 s again. Such cycle was repeated until a 30 ml glue was dispensed off in about 3 h. The nozzle-clog at the nozzle was observed every 10 min, and the times of nozzle-clog within 3 hours was recorded. 5 glues were used for glue dispensing for each kind of the sample and the total times of nozzle-clog were recorded. The reactive polyurethane hot-melt adhesive composition in the present invention has a total time of nozzle-clog of less than 5, preferably less than 3.

The present invention would be further illustrated in detail below through examples and comparative examples. The following examples are not to limit the scope of the present invention.

Test methods

Viscosity (mPa. s) : Determination was carried out at 110 ℃ using a DVT-II type Brookfield viscometer utilizing a 27 #rotor.

Initial tack (MPa) (it could also be called as green strength) : Two polycarbonate sheets of 100 mm × 25 mm × 6 mm were prepared as substrates. In the center of one of the polycarbonate sheets, two adhesive lines with an interval of 11 mm parallel to the length of the substrates were coated, and limit steel wires with a diameter of 0.2 mm were placed on both sides of the two adhesive lines. Then, the other polycarbonate sheet was pressed in a 90-degree direction onto the first polycarbonate sheet to form a cross-shaped laminated body and pressed together, so that each adhesive strip after pressing was 25 mm in length and 1 mm in width. The laminated body was placed in an environment of 23 ℃ and 50%relative humidity for 20 minutes and then a cross tensile test was performed. Each sample was tested five times to take the average value.

Bonding strength (Mpa) : A cross-shaped laminated body was prepared according to the same method for testing the initial tack and was placed in an environment of 23 ℃ and 50%relative humidity for 24 hours, and then the cross tensile test was performed. Each sample was tested five times to take the average value.

Thermal stability (%) : At 110 ℃, a sample was placed into a DVT-II type Brookfield viscometer (27 #rotor) . The first occurrence of the plateau value was recorded. Then, the viscosity value after 6 hours was recorded. Growth rate of viscosity was calculated and expressed in percentage.

Shape: A VERMES MDC3200 glue dispenser was used for continuous glue dispensing, and a nozzle with a diameter of 0.1 mm was selected for glue dispensing. The shape of the ejected glue line was observed. If the shape was stable and maintained non-scattering, it was recorded as “qualified” ; if collapsed, it was recorded as “unqualified” .

Nozzle-clog test: A VERMES MDC3200 glue dispenser was used for continuous glue dispensing, and a nozzle with a diameter of 0.1 mm was selected. The glue dispensing was performed for 5 s. After that, there was an interval of 5 s, and then the glue dispensing was performed for 5 s again. Such cycle was repeated until a 30 ml glue was dispensed off in about 3 h. The nozzle-clog at the nozzle was observed every 10 min, and the times of nozzle-clog within 3 hours was recorded. 5 glues were used for glue dispensing for each kind of the sample and the total times of nozzle-clog were recorded.

Width of bead: A VERMES MDC3200 glue dispenser was used for continuous glue dispensing, and a nozzle with a diameter of 0.1 mm was selected. The width of bead was tested.

The bio-based content of the composition: the sum of (bio-based content of every component× the weight percentages of the component in the composition) .

Raw materials

Dow Voranol 2120P, a polyether polyol.

Evonik Dynacoll 7360, an aliphatic crystalline polyester polyol, a crystallinity of 50.1%.

Evonik D7750, an aliphatic polyester polyol, with a bio-based content of 96%, a crystallinity of 55.7%.

PE2000: a self-made bio-based polyester polyol. A linear aliphatic crystalline polyester polyol B1-3 with a number average molecular weight of 2,000 g/mol, a bio- based content of 100%, a crystallinity of 56.2%a hydroxyl value of 55 mgKOH/g, and an acid value of less than 1, was prepared by using sebacic acid and bio-based 1, 4-butanediol as raw materials through condensation reaction in the presence of a titanium-based catalyst.

Cargill/Croda Priplast 3238, an aliphatic amorphous polyester polyol, 100%bio-based.

Dianal MB3068, a hydroxyl functionalized acrylic resin with a hydroxyl value of 8 mg KOH/g, a number average D90 particle size of 190 μm, Tg of 51℃, and a weight average molecular weight of 4, 1000 g/mol.

Dianal BR113, an acrylic resin without an active functional group, having a number average D90 particle size of 270 μm.

Covestro DESMODUR 44C, an aromatic diisocyanate MDI.

BASF Irganox 1010: an antioxidant.

Huntsman DMDEE: a catalyst.

Adhesive Composition

A sample of the adhesive composition was prepared by the following method. According to the weight percentages of each component in Table 1, the polyether polyol, the crystalline polyester polyol, the non-crystalline polyester polyol, and the acrylic resin components were firstly added to a reactor, heated in nitrogen atmosphere to 150 ℃, and vacuumized for 2-3 hours to remove water. Then, the temperature was lowered to 110 ℃. Dry nitrogen gas was introduced, and the polyisocyanate and the antioxidant were added. The reaction was performed by stirring in a nitrogen atmosphere at 120 ℃ for 2 hours. The catalyst was added, and the reaction was further performed by stirring in the nitrogen atmosphere for 30 minutes. Then, the resultant was discharged into a 30 ml high-temperature resistant plastic needle tube, defoamed under vacuum for 30 minutes at 120 ℃, and then sealed and cooled down.

In Examples 1-4 and Comparative Examples 1-2, the samples of the adhesive compositions were prepared by using the raw materials according to corresponding weight percentages listed in the upper part of Table 1. Among them, the hydroxyl-containing acrylic resin with the number average D90 particle size within the scope of the present invention was used in Examples 1-4, while no acrylic resin was used in Comparative Example 1, and the acrylic resin with a larger particle size was used in Comparative Example 2. According to the performance test results shown in Table 1, when the sample in Comparative Example 1 was jetted/dispensed through a piezoelectric jetting system, an adhesive scattering phenomenon occurred, the adhesive bead collapsed, which was unable to maintain a certain aspect ratio, and the adhesive force and bonding strength were poorer. Frequent nozzle-clog occurred in Comparative Example 2. In contrast, all the performance indexes of Examples 1-4 were qualified. The experimental results demonstrated that the use of the acrylic resin containing the active functional group with the number average D90 particle size within the scope of the present invention could effectively solve the problem that frequently occurred during jetting/dispensing.

Table 1.

Claims

A reactive polyurethane hot-melt adhesive composition prepared by a raw material comprising the following components:

component (A) comprising at least one polyether polyol;

component (B) comprising at least one crystalline polyester polyol (B1) and at least one non-crystalline polyester polyol (B2) ;

component (C) comprising at least one acrylic resin (C1) , the acrylic resin (C1) comprising an active functional group which is reactive with an isocyanate group, the acrylic resin (C1) having a number average D90 particle size of no greater than 350 μm;

and

component (D) comprising at least one polyisocyanate,

wherein the equivalent ratio of the isocyanate groups to hydroxyl groups (NCO/OH) of the above components is from 1.2 to 6, preferably from 1.5 to 5, and more preferably from 1.7 to 3.
The reactive polyurethane hot-melt adhesive composition according to claim 1, wherein, the acrylic resin (C1) has a number average D90 particle size of no greater than 250 μm, preferably no greater than 210 μm, more preferably in a range of from 100 μm to 210 μm, most preferably in a range of from 120 μm to 200 μm, extremely preferably in a range of 160 to 200 μm.
The reactive polyurethane hot-melt adhesive composition according to claim 1 or 2, wherein the active functional group which is reactive with an isocyanate group comprises one or two of hydroxyl group and amino group.
The reactive polyurethane hot-melt adhesive composition according to any of claims 1 to 3, wherein the acrylic resin (C1) has a hydroxyl value ranging from 1 to 10 mg KOH/g, preferably from 2 to 10 mg KOH/g, and more preferably from 4 to 10 mg KOH/g.
The reactive polyurethane hot-melt adhesive composition according to any of claims 1 to 4, wherein the acrylic resin (C1) has a glass transition temperature (Tg) of 30 to 110 ℃, preferably of 40 to 80 ℃, more preferably of 45 to 58 ℃.
The reactive polyurethane hot-melt adhesive composition according to any of claims 1 to 5, wherein the acrylic resin (C1) has a weight average molecular weight in a range of 3,000 to 80,000 g/mol, preferably from 5,000 to 60,000 g/mol, and more preferably from 5,000 to 50,000 g/mol.
The reactive polyurethane hot-melt adhesive composition according to any of claims 1 to 6, wherein the content of the acrylic resin (C1) is in a range of 3 to 25 wt%, preferably from 5 to 20 wt%, and more preferably from 5 wt%to 15 wt%, based on the total weight of the components (A) to (D) .
The reactive polyurethane hot-melt adhesive composition according to any of claims 1 to 7, wherein the component (C) further comprises at least one acrylic resin (C2) , and the acrylic resin (C2) is substantially free of the active functional group which is reactive with an isocyanate group.
The reactive polyurethane hot-melt adhesive composition according to any of claims 1 to 8, wherein the weight ratio of the crystalline polyester polyol (B1) to the non-crystalline polyester polyol (B2) is in a range of 1: 9 to 9: 1, preferably from 1: 9 to 5: 1, and more preferably from 1: 9 to 3: 1, most preferably from 1: 3 to 3: 1.
The reactive polyurethane hot-melt adhesive composition according to any of claims 1 to 9, wherein the component (A) , the component (B) , and the component (C) are substantially free of an aromatic compound.
The reactive polyurethane hot-melt adhesive composition according to any of claims 1 to 10, wherein the at least one polyisocyanate is an aromatic polyisocyanate.
The reactive polyurethane hot-melt adhesive composition according to any of claims 1 to 11, wherein the component (A) , the component (B) , the component (C) , and the component (D) comprise at least one partially or fully bio-based material.
The reactive polyurethane hot-melt adhesive composition according to any of claims 1 to 12 having a bio-based content of 10%or greater, preferably 30%or greater, and more preferably 40%or greater, the bio-based content being determined according to ASTM D6866.
The reactive polyurethane hot-melt adhesive composition according to any of claims 1 to 13 having a viscosity at 100 ℃ in a range of from 1,500 to 10,000 mPa. s, preferably in a range of from 1,500 to 8,000 mPa. s, and more preferably in a range of from 1,500 to 5,000 mPa. s.
An article, comprising a first substrate and an adhesive layer disposed on the first substrate formed by curing the reactive polyurethane hot-melt adhesive composition according to any one of claims 1 to 14.
The article according to claim 15, wherein the adhesive layer has a thickness in a range of from 0.01 to 2 mm, preferably in a range of from 0.05 to 1 mm, and more preferably in a range of from 0.1 to 0.5 mm.
The article according to claim 15 or 16, wherein the adhesive layer is formed by coating the reactive polyurethane hot-melt adhesive composition according to any one of claims 1 to 14 on the first substrate through a piezoelectric injection system and curing the resultant.
Use of acrylic resin in reactive polyurethane hot-melt adhesive composition according to any of claims 1 to 14 for improving dispensing performance, wherein the acrylic resin is the acrylic resin (C1) according to any of claims 1 to 14.
Use according to claim 18, wherein

the reactive polyurethane hot-melt adhesive composition has a total time of nozzle-clog of less than 5, preferably less than 3.