Technology Field

The present invention relates to a polyol composition, comprising at least one polyol A, wherein the at least one polyol A has an endothermic peak in the differential scanning calorimetry (DSC) curve of the second heating located in the range from 70 to 110 °C; and at least one polyol B, wherein the at least one polyol B has an exothermic peak in the DSC curve of the first cooling located in the range from 0 to 35 °C and has an endothermic peak in the DSC curve of the second heating located in the range from 45 to 80 °C; wherein the at least one polyol A is different from the at least one polyol B; and relates to a reactive polyurethane hot melt.

Background

Hot melt adhesives (or "HMAs") are generally 100% solid materials at room temperature which do not contain or require any solvent(s). On application of heat, HMAs melt to a liquid/fluid state in which form they are applied to one or more substrates. Upon cooling, the HMA regains its prior solid form and gains its initial cohesive strength. HMAs which are applied in molten form and cool to solidify and subsequently cured by a chemical crosslinking reaction have been prepared using specific materials such as polyurethanes.

Crosslinkable thermoplastic polyurethanes for adhesive applications are also referred to as reactive polyurethane hot melts. Reactive polyurethane hot melts are a product group which is experiencing significant growth among the applications of polyurethanes in the adhesives sector.

Reactive hot melts cure through a combination of an initial physical cure and a secondary chemical crosslinking. The secondary chemical crosslinking can be initiated by heat, moisture, or both heat and moisture. Upon cooling, there is a rapid development of initial bond (or "green") strength, meaning that substrates can be rapidly affixed for further processing. Final strength is reached later after conclusion of chemical crosslinking. Systems in which moisture initiates the crosslinking consist of high molecular weight, "meltable" polyurethanes with terminal isocyanate groups that react when exposed to moisture.

In the area of reactive hot melts, on one hand, the operators prefer a relatively long open time for operation; on the other hand, operators prefer a minimum waiting time after adhesive application. Technically speaking, the operators would like to have an adhesive with fast bonding strength build up (i.e. high green strength), especially at high operation temperature for example at about 70 °C, but still with an operation time long enough.

The reactive hot melts in the prior art have insufficient green strength or insufficient open time. Therefore, there is a need for reactive hot melts which have both high green strength and relatively long open time. Summary of the Invention

It is an object of the invention to provide a polyol composition comprising special combination of polyols such that the resulted reactive polyurethane hot melt has excellent green strength and enough operation time.

Another object of the present invention is to provide a reactive polyurethane hot melt, especially formed from the polyol composition of the present invention and an isocyanate component, wherein the reactive polyurethane hot melt according to the present invention has excellent green strength and enough operation time.

A further object of the present invention is to provide use of the reactive polyurethane hot melt of the present invention as adhesive.

A further object of the present invention is to provide an article comprising an adhesive layer formed from the reactive polyurethane hot melt of the present invention.

It has been surprisingly found that the above objects can be achieved by following embodiments:

1. A polyol composition, comprising at least one polyol A, wherein the at least one polyol A has an endothermic peak in the differential scanning calorimetry (DSC) curve of the second heating located in the range from 70 to 110 °C; and at least one polyol B, wherein the at least one polyol B has an exothermic peak in the DSC curve of the first cooling located in the range from 0 to 35 °C and has an endothermic peak in the DSC curve of the second heating located in the range from 45 to 80 °C; wherein the at least one polyol A is different from the at least one polyol B; and wherein the DSC curves are obtained by DSC in which the at least one polyol A or the at least one polyol B is heated from -70 °C to 150 °C at a temperature increase rate of 10°C/min to obtain the DSC curve of the first heating; and then cooled from 150 °C to -70 °C at a temperature decrease rate of 10 °C/min to obtain the DSC curve of the first cooling; and then heated again from -70 °C to 150 °C at a temperature increase rate of 10 °C/min to obtain the DSC curve of the second heating.

2. The polyol composition according to item 1 , wherein the endothermic peak of the at least one polyol A in the DSC curve of the second heating is located in the range from 80 to 105 °C.

3. The polyol composition according to item 1 or 2, wherein the exothermic peak of the at least one polyol B in the DSC curve of the first cooling is located in the range from 8 to 33 °C.

4. The polyol composition according to any of items 1 to 3, wherein the endothermic peak of the at least one polyol B in the DSC curve of the second heating is located in the range from 48 to 5. The polyol composition according to any of items 1 to 4, wherein the area of said endothermic peak of the at least one polyol A is in the range from 15 to 100 J/g, preferably from 20 to 80 J/g.

6. The polyol composition according to any of items 1 to 5, wherein the ratio of the area of said exothermic peak of the at least one polyol B to the area of said endothermic peak of the at least one polyol B is in the range from 0.35 to 4.0, preferably from 0.8 to 1.5.

7. The polyol composition according to any of items 1 to 6, wherein the at least one polyol A is a polyester polyol, preferably the at least one polyol A is a polyester polyol formed from a linear aliphatic dicarboxylic acid having 6 to 16 carbon atoms or anhydride thereof or its ester with lower alcohol, an aromatic dicarboxylic acid having 8 to 12 carbon atoms or anhydride thereof or its ester with lower alcohol, and a linear aliphatic diols having 6 to 16 carbon atoms.

8. The polyol composition according to any of items 1 to 7, wherein the at least one polyol B is selected from polyester polyol, polyether polyol and mixture thereof, preferably the polyester polyol as the at least one polyol B is formed from a linear aliphatic dicarboxylic acid having 4 to 16 carbon atoms or anhydride thereof or its ester with lower alcohol and a linear aliphatic diol having 4 to 16 carbon atoms and wherein the linear aliphatic dicarboxylic acid and the linear aliphatic diol have different number of carbon atoms.

9. The polyol composition according to item 8, wherein the at least one polyol B is a mixture of polyester polyol and polyether polyol, preferably the polyether polyol is at least one polytetrahydrofuran.

10. The polyol composition according to any of items 1 to 9, wherein the weight ratio of the at least one polyol A and the at least one polyol B is in the range from 5:1 to 1 :4, preferably from 3:1 to 1 :2.

11. The polyol composition according to any of items 1 to 10, wherein the amount of the at least one polyol A is in the range from 15 to 75 wt.%, preferably from 25 to 60 wt.%, based on the total weight of the polyol composition.

12. The polyol composition according to any of items 1 to 11 , wherein the amount of the at least one polyol B is in the range from 10 to 65 wt.%, preferably from 15 to 55 wt.%, based on the total weight of the polyol composition.

13. The polyol composition according to any of items 1 to 12, further comprising a component (C) selected from amorphous polyol and thermoplastic polymer, preferably the amorphous polyol and thermoplastic polymer have a glass transition temperature of at least 20 °C.

14. The polyol composition according to any of items 1 to 12 comprising

15 to 70 wt.%, preferably 25 to 55 wt.% of at least one polyol A; 10 to 60 wt.%, preferably 15 to 50 wt.% of at least one polyol B, and 5 to 45 wt.%, preferably 10 to 30 wt.% of component (C); in each case based on the total weight of the polyol composition.

15. A reactive polyurethane hot melt, which is formed from the polyol composition according to any of items 1 to 14 and an isocyanate component.

16. The reactive polyurethane hot melt according to item 15, which is formed from the reaction of the polyol composition according to any of items 1 to 14 with the isocyanate component comprising at least one polyisocyanate.

17. A reactive polyurethane hot melt which has an endothermic peak 1 in the DSC curve of the second heating located in the range from 70 to 110 °C, preferably from 80 to 100 °C, an endothermic peak 2 in the DSC curve of the second heating located in the range from 35 to 75 °C, preferably from 40 to 60 °C; and an exothermic peak 1 in the DSC curve of the first cooling located in the range from 0 to 25 °C, preferably from 5 to 20 °C; wherein the DSC curves are obtained by DSC in which the reactive polyurethane hot melt is heated from -70 °C to 150 °C at a temperature increase rate of 2°C/min; and then cooled from 150 °C to -70 °C at a temperature decrease rate of 2°C/min to obtain the DSC curve of the first cooling; and then heated again from -70 °C to 150 °C at a temperature increase rate of 2°C/min to obtain the DSC curve of the second heating.

18. The reactive polyurethane hot melt according to item 17, which is formed from at least one polyol A, at least one polyol B and optionally component (C) as defined in any of items 1 to 14 and an isocyanate component, preferably formed from the polyol composition according to any of items 1 to 14 and an isocyanate component.

19. The reactive hot melt according to any of items 15 to 18, wherein the reactive polyurethane hot melt has a green strength at 70 °C of at least 55 KPa, preferably at least 75 KPa.

20. Use of the reactive polyurethane hot melt according to any of items 15 to 19 as adhesive.

21. An article comprising an adhesive layer formed from the reactive polyurethane hot melt according to any of items 15 to 19.

22. The article according to item 21 , comprising a first surface; a second surface disposed adjacent said first surface; and the adhesive layer disposed between said first and second surfaces such that said first and second surfaces are adhesively coupled by said adhesive layer. The polyol composition according to the present invention comprises special combination of polyols A and B and the resulted reactive hot melt has excellent green strength, especially excellent green strength at high temperature and the reactive hot melt still has long open time so that the operators have enough operation time and at the same time the hot melt also has suitable setting time.

Description of the Drawing

Figure 1 shows the DSC curves of AA-co-TPA-co-HDO.

Figure 2 shows the DSC curves of AA-co-BDO.

Figure 3 shows the DSC curves of the mixture of 5 parts by weight of DDA-co-HDO and 22.5 parts by weight of PTHF 2000 (polyol B used in example 7).

Figure 4 shows the DSC curves of the mixture of 17.5 parts by weight of DDA-co-HDO and 10 parts by weight of PTHF 2000 (polyol B used in example 4).

Figure 5 shows the DSC curves of the mixture of 10 parts by weight of DDA-co-HDO and 17.5 parts by weight of PTHF 2000 (polyol B used in example 5).

Figure 6 shows the DSC curves of the mixture of 10 parts by weight of DDA-co-HDO and 17.5 parts by weight of PTHF 1000 (polyol B used in example 6).

Figure 7 shows the DSC curves of the mixture of 7 parts by weight of DDA-co-HDO and 20.5 parts by weight of PTHF 2000 (polyol B used in example 8).

Figure 8 shows the DSC curves of AA-co-HDO.

Figure 9 shows the DSC curves of Dynacoll 7150.

Figure 10 shows the DSC curves of Hoopol F-39030.

Figure 11 shows the DSC curves of reactive polyurethane hot melt prepared in example 1. Figure 12 shows the DSC curves of reactive polyurethane hot melt prepared in example 2. Figure 13 shows the DSC curves of PTHF 1000.

Figure 14 shows the DSC curves of PTHF 2000.

Embodiment of the Invention

The undefined article “a”, “an”, “the” means one or more of the species designated by the term following said article.

In the context of the present disclosure, any specific values mentioned for a feature (comprising the specific values mentioned in a range as the end point) can be recombined to form a new range.

One aspect of the present invention is directed to a polyol composition, comprising at least one polyol A, wherein the at least one polyol A has an endothermic peak in the differential scanning calorimetry (DSC) curve of the second heating located in the range from 70 to 110 °C; and at least one polyol B, wherein the at least one polyol B has an exothermic peak in the DSC curve of the first cooling located in the range from 0 to 35 °C and has an endothermic peak in the DSC curve of the second heating located in the range from 45 to 80 °C; wherein the at least one polyol A is different from the at least one polyol B; and wherein the DSC curves are obtained by differential scanning calorimetry in which the at least one polyol A or the at least one polyol B is heated from -70 °C to 150 °C at a temperature increase rate of 10°C/min to obtain the DSC curve of the first heating; and then cooled from 150 °C to -70 °C at a temperature decrease rate of 10°C/min to obtain the DSC curve of the first cooling; and then heated again from -70 °C to 150 °C at a temperature increase rate of 10°C/min to obtain the DSC curve of the second heating.

According to the present invention, DSC can be carried out according to ISO 11357-1 :2016 Plastics.

According to the present invention, the at least one polyol A has an endothermic peak in the differential scanning calorimetry (DSC) curve of the second heating located in the range from 70 to 110 °C, for example from 72 to 108 °C, from 74 to 106 °C, from 76 to 104 °C, from 78 to 102 °C, from 80 to 100 °C, or from 82 to 100 °C, preferably from 80 to 105 °C.

According to a preferred embodiment, the above endothermic peak of the at least one polyol A is a broad endothermic peak, for example the endothermic-peak width can be in the range from 18 to 45 °C, for example from 20 to 42 °C, from 22 to 40 °C, from 25 to 38 °C, or from 28 to 36 °C, preferably from 25 to 40 °C. The endothermic-peak width corresponds to the difference between an extrapolated onset temperature, which is the temperature corresponding to the intersection of a baseline and a tangent to the curve at a lower-temperature-side inflection point in the endothermic peak, and an extrapolated endset temperature, which is the temperature corresponding to the intersection of the baseline and a tangent to the curve at a higher-temperature-side inflection point in the endothermic peak, the baseline being a straight line obtained by approximating the portion of the DSC curve which is located on the higher-temperature side of the endothermic peak.

According to a preferred embodiment, the area of said endothermic peak of the at least one polyol A can be in the range from 15 to 100 J/g, for example 20 J/g, 25 J/g, 30 J/g, 35 J/g, 40 J/g, 45 J/g, 50 J/g, 55 J/g, 60 J/g, 65 J/g, 70 J/g, 75 J/g, 80 J/g, 85 J/g, 90 J/g, or 95 J/g, preferably in the range from 20 to 80 J/g.

In the context of the present disclosure, the area of the endothermic peak or exothermic peak can be tested by ISO 11357-1 :2016 Plastics.

According to the present invention, the at least one polyol A can also has an exothermic peak in the DSC curve of the first cooling located in the range from 50 to 80 °C, for example from 55 to 75 °C, or from 60 to 70 °C, preferably in the range from 58 to 68 °C.

According to the present invention, the polyol composition comprises at least one polyol B. The at least one polyol B has an exothermic peak in the DSC curve of the first cooling located in the range from 0 to 35 °C, for example from 2 to 34 °C, from 5 to 33 °C, from 8 to 33 °C, from 10 to 32 °C, from 11 to 32 °C, or from 20 to 32 °C, preferably in the range from 8 to 33 °C. According to the present invention, the at least one polyol B has an endothermic peak in the DSC curve of the second heating located in the range from 45 to 80 °C, for example from 47 to 78 °C, from 50 to 75 °C, from 50 to 72 °C, or from 50 to 70 °C, preferably from 48 to 73 °C.

In a preferred embodiment, the ratio of the area of said exothermic peak of the at least one polyol B to the area of said endothermic peak of the at least one polyol B is in the range from 0.35 to 4.0, for example 0.38, 0.4, 0.42, 0.45, 0.5, 0.6, 0.7, 0.8, 0.9, 1 , 1.2, 1.5, 1.8, 2, 2.5, 3, or 3.5, preferably from 0.8 to 1.5.

The area of said endothermic peak of the at least one polyol B can be in the range from 15 to 90 J/g, for example 16 J/g, 18 J/g, 20 J/g, 25 J/g, 30 J/g, 35 J/g, 40 J/g, 45 J/g, 50 J/g, 55 J/g, 60 J/g, 65 J/g, 70 J/g, 75 J/g, 80 J/g, or 85 J/g, preferably in the range from 16 to 80 J/g, for example, in the range from 35 to 80 J/g.

The area of said exothermic peak of the at least one polyol B can be in the range from15 to 90 J/g, for example 16 J/g, 18 J/g, 20 J/g, 25 J/g, 30 J/g, 35 J/g, 40 J/g, 45 J/g, 50 J/g, 55 J/g, 60 J/g, 65 J/g, 70 J/g, 75 J/g, 80 J/g, or 85 J/g, preferably in the range from 16 to 80 J/g, for example, in the range from 30 to 80 J/g.

In one embodiment, a mixture comprising two or more polyol is used as the polyol B. In this scenario, the mixture is completely homogenized, for example the mixture is heated to melt under stirring before carrying out DSC testing.

According to one embodiment, the at least one polyol A is a polyester polyol. Preferably the at least one polyol A is a polyester polyol formed from a linear aliphatic dicarboxylic acid having 6 to 16 carbon atoms or anhydride thereof or its ester with lower alcohol (such as methanol), an aromatic dicarboxylic acid having 8 to 12 carbon atoms or anhydride thereof or its ester with lower alcohol (such as methanol) and a linear aliphatic diols having 6 to 16 carbon atoms. The molar ratio of the linear aliphatic dicarboxylic acid and anhydride or ester thereof to the aromatic dicarboxylic acid and anhydride or ester thereof can be in the range from 5:1 to 1 :5, for example 4:1 , 3: 1 , 2: 1 , 1 :1 , 1 :2, 1 :3, 1 :4, preferably from 3: 1 to 1 :3.

The linear aliphatic dicarboxylic acid for forming the polyol A can have 6 to 16 carbon atoms, preferably 6 to 14 carbon atoms, for example 6, 7, 8, 9, 10, 11 , 12 or 14 carbon atoms, preferably 6 to 12 carbon atoms. The specific example of linear aliphatic dicarboxylic acid can include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid or dodecanedioic acid, preferably adipic acid. The anhydrides or esters with lower alcohol (such as methanol) of these acids are also suitable.

The aromatic dicarboxylic acid for forming polyol A can have 8 to 12 carbon atoms, for example 8, 10, 12 carbon atoms. The specific examples of aromatic dicarboxylic acid can include terephthalic acid, naphthalene dicarboxylic acid. The anhydrides or esters with lower alcohol (such as methanol) of these acids are also suitable. The linear aliphatic diols for forming polyol A can have 6 to 16 carbon atoms, for example 6, 7, 8, 9, 10, 12 or 14 carbon atoms, preferably 6 to 12 carbon atoms. The specific examples of the linear aliphatic diols can include 1 ,6-hexanediol, 1 ,7-heptanediol, 1 ,8-octanediol, 1 ,9-nonanediol, 1 ,10- decanediol, 1 ,12-dodecanediol, preferably 1 ,6-hexanediol.

According to a preferred embodiment, the linear aliphatic dicarboxylic acid and the linear aliphatic diols for forming the polyol A can have the same number of carbon atoms.

The weight average molecular weight (Mw) of the polyol A can be in the range from 1000 to 6000 g/mol, preferably 1500 to 5000 g/mol, for example 2000 g/mol, 2500 g/mol, 3000 g/mol, 3500 g/mol, 4000 g/mol or 4500 g/mol. The polyol A can have a hydroxyl number in the range from 15 to 80 mg KOH/g, for example 25 mg KOH/g, 30 mg KOH/g, 35 mg KOH/g, 40 mg KOH/g, 45 mg KOH/g, 50 mg KOH/g, 55 mg KOH/g, 60 mg KOH/g, 65 mg KOH/g, 70 mg KOH/g or 75 mg KOH/g, preferably 20 to 50 mg KOH/g.

The amount of the at least one polyol A can be in the range from 15 to 75 wt.%, for example 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, preferably from 25 to 60 wt.%, based on the total weight of the polyol composition.

According to the present invention, the at least one polyol B in the polyol composition can be selected from polyester polyol, polyether polyol and mixture thereof.

In one embodiment, the at least one polyol B is a polyester polyol. The polyester polyol as the at least one polyol B can be formed from a linear aliphatic dicarboxylic acid having 4 to 16 carbon atoms or anhydride thereof or its ester with lower alcohol (such as methanol) and a linear aliphatic diol having 4 to 16 carbon atoms and wherein the linear aliphatic dicarboxylic acid and the linear aliphatic diol have different number of carbon atoms.

The linear aliphatic dicarboxylic acid can have 4 to 16 carbon atoms, for example, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15 or 16 carbon atoms, preferably 4 to 12 carbon atoms. The specific example of these acids can include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid or dodecanedioic acid, preferably adipic acid and dodecanedioic acid. The anhydrides and esters with lower alcohol (such as methanol) of these acids are also suitable.

The linear aliphatic diols can have 4 to 16 carbon atoms, for example 4, 5, 6, 7, 8, 9, 10, 11 , 12 or 14 carbon atoms, and preferably 4 to 12 carbon atoms. The specific examples of the linear aliphatic diols can include 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, 1 ,7-heptanediol, 1 ,8- octanediol, 1 ,9-nonanediol, 1 ,10-decanediol, 1 ,12-dodecanediol, preferably 1 ,4-butanediol and 1 ,6-hexanediol.

The polyether polyol used as the at least one polyol B can comprise, for example poly(oxypropyl- ene) polyol and polytetrahydrofuran. In one embodiment, the at least one polyol B comprises a mixture of a polyester polyol and a polyether polyol (such as polytetrahydrofuran). The weight ratio of the polyester polyol and the polyether polyol in the mixture can be in the range from 10:1 to 1 :10, for example, 8:1 , 5:1 , 3:1 , 1 : 1 , 1 :3, 1 :5, 1 : 8, preferably 5: 1 to 1 :5.

The weight average molecular weight (Mw) of the polyol B can be in the range from 800 to 6000 g/mol, preferably 1000 to 5000 g/mol or 1500 to 5000 g/mol, for example 1000 g/mol, 2000 g/mol, 2500 g/mol, 3000 g/mol, 3500 g/mol, 4000 g/mol or 4500 g/mol. The polyol B can have a hydroxyl number in the range from 15 to 95 mg KOH/g, 25 mg KOH/g, 30 mg KOH/g, 35 mg KOH/g, 40 mg KOH/g, 45 mg KOH/g, 50 mg KOH/g, 55 mg KOH/g, 60 mg KOH/g, 65 mg KOH/g, 70 mg KOH/g or 75 mg KOH/g or 80 mg KOH/g or 85 mg KOH/g or 90 mg KOH/g, preferably 20 to 85 mg KOH/g.

The amount of the at least one polyol B can be in the range from 10 to 65 wt.%, for example 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.% or 55 wt.%, 60 wt.%, preferably from 15 to 55 wt.%, based on the total weight of the polyol composition.

According to the present invention, the weight ratio of the at least one polyol A and the at least one polyol B can be in the range from 5: 1 to 1 :4, for example 4: 1 , 3: 1 , 2: 1 , 1 : 1 , 1 :2 or 1 :3, preferably from 3:1 to 1 :2.

According to an embodiment of the present invention, the polyol composition further comprises a component (C) selected from amorphous polyol and thermoplastic polymer. In a preferred embodiment, the amorphous polyol and thermoplastic polymer have a glass transition temperature of at least 20 °C, for example at least 25 °C, at least 30 °C or at least 40 °C. Usually, the glass transition temperature of the amorphous polyol and thermoplastic polymer do not exceed 90 °C. In the context of the present disclosure, glass transition temperature is tested according to ISO 11357-1 :2016 Plastics at a temperature increase rate of 10°C/min.

Suitable amorphous polyol as component (C) includes amorphous polyester polyols and amorphous polyether polyol and mixture thereof.

The amorphous polyester polyols can be formed from at least one dicarboxylic acid and at least one diol.

The dicarboxylic acid can include aromatic dicarboxylic acid, in particular terephthalic acid and isophthalic acid and aliphatic dicarboxylic acid having 3 to 10, preferably 4 to 8 carbon atoms, or anhydride thereof or its ester with lower alcohol (such as methanol).

In a preferred embodiment, a mixture of terephthalic acid and isophthalic acid is used for forming the amorphous polyol. Examples of diols for forming the amorphous polyol can include aliphatic diols having 2 to 16 carbon atoms, for example 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12 or 14 carbon atoms, preferably 2 to 12 carbon atoms, cycloaliphatic diol having 6 to 10 carbon atoms, or diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol, and polybutylene glycols or the ester of these diols with an acid having hydroxyl (such as 3-hydroxy-2,2-dimethylpropyl 3-hydroxy-2,2-dimethylpropanoate). The specific example of aliphatic diols having 2 to 16 carbon atoms can include for example ethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, 1 ,3-butanediol, 1 ,4-butenediol, 1 ,4-butynediol, 1 ,5-pentanediol, neopentyl glycol, 2-methyl-1 ,3-propanediol, methylpentanediols. Specific example of cycloaliphatic diol can include for example bis(hydroxymethyl)cyclohexanes, such as 1 ,4-bis(hydroxymethyl)cyclohexane.

It is preferable to use a mixture comprising two or more diols such as a mixture comprising two or more aliphatic diols having 2 to 16 carbon atoms, or a mixture comprising one aliphatic diol having 2 to 16 carbon atoms (especially ethylene glycol) and a ester of said aliphatic diol with an acid having hydroxyl, or a mixture comprising diethylene glycol and an aliphatic diol having 2 to 16 carbon atoms (especially neopentyl glycol).

Examples of amorphous polyether polyol can include for example copolymers of tetra hydrofuran (THF) and 3-methyl-THF, polypropylenglycol (PPG) or copolymers of propylenglycol and polyeth- ylenglycol.

The weight average molecular weight (Mw) of the amorphous polyol as component (C) can be in the range from 1000 to 6000 g/mol, preferably 1000 to 5000 g/mol or 1500 to 5000 g/mol, for example 1000 g/mol, 2000 g/mol, 2500 g/mol, 3000 g/mol, 3500 g/mol, 4000 g/mol or 4500 g/mol. The amorphous polyol can have a hydroxyl number in the range from 15 to 80 mg KOH/g, preferably 20 to 60 mg KOH/g, for example 25 mg KOH/g, 30 mg KOH/g, 35 mg KOH/g, 40 mg KOH/g, 45 mg KOH/g, 50 mg KOH/g or 55 mg KOH/g.

The thermoplastic polymer as component (C) can include for example thermoplastic polyester, thermoplastic polyurethane, thermoplastic polyolefin.

The thermoplastic polyester can include an aliphatic polyester and aromatic polyester. The aliphatic polyester can be selected from the group consisting of polybutylene succinates, polycaprolactones, polyhydroxyalkanoates, polyglycolic acids and polylactic acids. The aromatic polyester can include a polyethylene terephthalate, polybutylene adipate/terephthalate or a polymethylene adipate/terephthalate. The polyolefin can be a polyethylene, polypropylene, or polybutylene.

The amount of component (C) can be in the range from 5 to 45 wt.%, for example 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, preferably from 10 to 30 wt.%, based on the total weight of the polyol composition.

Usually, polyol A, polyol B and amorphous polyol used as component (C), have a functionality of 2. In a preferred embodiment, the polyol composition of the present invention comprising

15 to 70 wt.%, preferably 25 to 55 wt.% of at least one polyol A;

10 to 60 wt.%, preferably 15 to 50 wt.% of at least one polyol B, and

5 to 45 wt.%, preferably 10 to 30 wt.% of component (C); in each case based on the total weight of the polyol composition.

One aspect of the present invention is directed to a reactive polyurethane hot melt formed from the polyol composition of the present invention and the isocyanate component.

The reactive polyurethane hot melt can be formed from the reaction of the polyol composition of the present invention with an isocyanate component comprising at least one polyisocyanate.

Preferred polyisocyanates in the context of the present invention are diisocyanates, especially aliphatic, aromatic and cycloaliphatic diisocyanates.

Examples of aromatic diisocyanates are 2,4-tolylene diisocyanate (2,4-TDI), and MDI such as 4,4’-diphenylmethane diisocyanate (4,4’-MDI), 2,2’-diphenylmethane diisocyanate (2,2’-MDI), 2,4’-diphenylmethane diisocyanate (2,4’-MDI) and so-called TDI mixtures (mixtures of 2,4-tol- ylene diisocyanate and 2,6-tolylene diisocyanate).

Examples of aliphatic diisocyanates are 1 ,4-butylene diisocyanate, 1 ,12-dodecamethylene diisocyanate, 1 ,10-decamethylene diisocyanate, 2-butyl-2-ethylpentamethylene diisocyanate, 2,4,4- trimethylhexamethylene diisocyanate or 2,2,4-trimethylhexamethylene diisocyanate and in particular hexamethylene diisocyanate (HDI).

Examples of cycloaliphatic diisocyanates are isophorone diisocyanate (IPDI), 2-isocyanatopropyl- cyclohexyl isocyanate, 2,4’-methylenebis(cyclohexyl) diisocyanate and 4-methylcyclohexane 1 ,3- diisocyanate (H-TDI).

Further examples of isocyanates having groups of differing reactivity are 1 ,3-phenylene diisocyanate, 1 ,4-phenylene diisocyanate, 1 ,5-naphthylene diisocyanate, diphenyl diisocyanate, toldine diisocyanate and 2,6-tolylene diisocyanate.

According to the present invention, the preferred polyisocyanates are aromatic diisocyanates, especially MDI, especially 4,4’-diphenylmethane diisocyanate (4,4’-MDI).

Regarding the method for preparing the reactive polyurethane hot melt, the method can comprise the steps of providing the isocyanate component and the polyol composition of the present invention. Each of the components can be provided in various manners. The components can be combined in any order.

In one embodiment, the method further comprises the step of heating the polyol composition of the present invention and/or isocyanate component until molten prior to the step of combining. This is especially useful when the components are in solid (or semi-solid) form. In one preferred embodiment, the polyol component can be heated to melt all polyols. Then, isocyanate component is added to carry out the reaction. The reaction temperature can be in the range from 100 to 140 °C, preferably from 110 to 130 °C.

In one embodiment, an inert atmosphere is established in the reactor, e.g. a nitrogen and/or argon blanket, to prevent premature moisture cure of the reactive polyurethane hot melt during formation. A similar blanket can also be used for storage and/shipment of the reactive polyurethane hot melt, e.g. while transported/stored in drums.

The reactive polyurethane hot melt typically has a NCO group content of from about 1 to about 5 wt.%, for example about 1.2 wt.%, 1.4 wt.%, 1.6 wt.%, 1.8 wt.%, 1.85 wt.%, 1.9 wt.%, 1.95 wt.%, 2 wt.%, 2.05 wt.%, 2.1 wt.%, 2.2 wt.%, 2.3 wt.%, 2.5 wt.%, 2.8 wt.%, 3 wt.%, 3.5 wt.%, 4 wt.%, 4.5 wt.%, preferably from about 1.5 to about 2.5 wt.%, based on the total weight of the reactive polyurethane hot melt. The NCO group content is useful for eventual moisture cure of the hot melt after application, as understood in the art.

The reactive polyurethane hot melt of the present invention has a high green strength, especially a high green strength at 70 °C, for example of at least 55 KPa, preferably at least 75 KPa, for example at least 80 KPa, at least 100 KPa, at least 120 KPa, at least 140 KPa, at least 150 KPa, at least 180 KPa, or at least 200 KPa. The sample for testing the green strength can be prepared according to DIN EN 1465 (Adhesives - Determination of tensile lap-shear strength of bonded assemblies).

In an embodiment, a reactive polyurethane hot melt is provided, which has an endothermic peak 1 in the DSC curve of the second heating located in the range from 70 to 110 °C, preferably from 80 to 100 °C, an endothermic peak 2 in the DSC curve of the second heating located in the range from 35 to 75 °C, preferably from 40 to 60 °C; and an exothermic peak 1 in the DSC curve of the first cooling located in the range from 0 to 25 °C, preferably from 5 to 20 °C; wherein the DSC curves are obtained by DSC in which the reactive polyurethane hot melt is heated from -70 °C to 150 °C at a temperature increase rate of 2°C/min to obtain the DSC curve of the first heating; and then cooled from 150 °C to -70 °C at a temperature decrease rate of 2°C/min to obtain the DSC curve of the first cooling; and then heated again from -70 °C to 150 °C at a temperature increase rate of 2°C/min to obtain the DSC curve of the second heating.

In one embodiment, the area of said endothermic peak 2 is in the range from 10 to 60 J/g, for example 15 J/g, 20 J/g, 25 J/g, 30 J/g, 40 J/g, 50 J/g, or 55 J/g, preferably from 15 to 50 J/g.

In one embodiment, the area of said exothermic peak 1 is in the range from 8 to 60 J/g, for example 10 J/g, 15 J/g, 20 J/g, 25 J/g, 30 J/g, 40 J/g, 50 J/g, or 55 J/g, preferably from 10 to 50 J/g. The ratio of the area of said exothermic peak 1 to the area of said endothermic peak 2 can be in the range from 0.1 to 4.0, for example 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.5, 1.8, 2, 2.5, 3, 3.5, or 4, preferably from 0.2 to 2.

Here, DSC can also be carried out according to ISO 11357-1 :2016 Plastics.

This reactive polyurethane hot melt can be formed from at least one polyol A, at least one polyol B and optionally component (C) as described in the context of this disclosure and an isocyanate component, preferably formed from the polyol composition of the present invention and an isocyanate component.

A further aspect of the present invention relates to use of the reactive polyurethane hot melt of the present invention as adhesive.

While the reactive polyurethane hot melt may be used directly as described above, if desired, the hot melt may also be formulated with conventional additives such as tackifiers, stabilizers, fillers, flow control agents, thickeners, wetting agents, defoamers, crosslinkers, plasticizers, ageing inhibitors, fungicides, pigments, dyes, matting agents, and neutralizing agents, anti-oxidants, anti-UV agents, mercapto/silane adhesion promoters, catalysts and the like. This disclosure is not limited to any particular type or amount of additive.

Tackifiers are known per se to the skilled person. They are additives for adhesives or elastomers that improve the auto adhesion (tack, intrinsic stickiness, self-adhesion) of these systems. They generally have a relatively low molar mass (Mn about 200-2000 g/mol), a glass transition temperature which lies above that of the elastomers. The amount by weight of the tackifiers is preferably 5 to 100 parts by weight, more preferably 10 to 50 parts by weight, per 100 parts by weight of the polyurethane. Suitable tackifiers are, for example, those based on natural resins, such as rosins, for example. Tackifiers based on natural resins include the natural resins themselves and also their derivatives formed, for example, by disproportionation or isomerization, polymerization, dimerization or hydrogenation. They may be present in their salt form (with, for example, monovalent or polyvalent counterions (cations)), or, preferably, in their esterified form. Alcohols used for the esterification may be monohydric or polyhydric. Examples are methanol, ethanediol, diethylene glycol, triethylene glycol, 1 ,2,3-propanetriol, and pentaerythritol. Also finding use as tackifiers, furthermore, are phenolic resins, hydrocarbon resins, e.g., coumarone-indene resins, polyterpene resins, terpene oligomers, hydrocarbon resins based on unsaturated CH compounds, such as butadiene, pentene, methylbutene, isoprene, piperylene, divinylmethane, pentadiene, cyclopentene, cyclopentadiene, cyclohexadiene, styrene, alpha-methylstyrene, vinyltoluene. Also being used increasingly as tackifiers are polyacrylates which have a low molar weight. These polyacrylates preferably have a weight-average molecular weight (Mw) of below 30000. The polyacrylates are composed preferably to an extent of 10 to 30%, more particularly 15 to 25%, by weight of Ci- Cs alkyl (meth)acrylates. Preferred tackifiers are natural or chemically modified rosins. Rosins are composed predominantly of abietic acid or derivatives thereof. For improved surface wetting, the hot melt may comprise wetting assistants, examples being fatty alcohol ethoxylates, alkylphenol ethoxylates, sulfosuccinic esters, nonyl- phenol ethoxylates, pol- yoxyethylenes/propylenes or sodium dodecylsulfonates.

Suitable stabilizers are e.g. selected from the group encompassing wetting agents, cellulose, polyvinyl alcohol, polyvinylpyrrolidone, and mixtures thereof.

The reactive polyurethane hot melt of the present invention can be applied by various means understood in the art, such as by extruding, rolling, pouring, spraying, brushing, daubing, smearing, dipping, sheeting, etc. After application, the hot melt develops green strength while cooling (i.e. , while resolidifying), then the hot melt moisture cures over time based on the residual NCO content, thereby forming internal crosslinks and setting the hot melt into a final cure state over time.

The reactive polyurethane hot melt according to the present invention is suitable for bonding of a wide variety of different materials, for example of metal, textiles, wood, ceramic or plastics. The reactive polyurethane hot melt of the invention can especially be used for bonding or fixing of shaped bodies in the automotive industry, of furniture, for example doors, or of consumer goods, sports articles or footwear, for example footwear soles.

A further aspect of the present invention relates to an article comprising an adhesive layer formed from the reactive hot melt according to the present invention.

In one embodiment, the article comprising a first surface; a second surface disposed adjacent said first surface; and the adhesive layer disposed between said first and second surfaces such that said first and second surfaces are adhesively coupled by said adhesive layer.

Specifically, the adhesive layer comprises the reaction product of the reactive polyurethane hot melt and water. Prior to application of the hot melt, the surfaces may be clean or dirty (e.g. oily), and can comprise various materials. Each of the first and second surfaces can individually comprise metal, wood (i.e., a lignocellulosic material), plastic, composites, or combinations thereof. The reactive polyurethane hot melt can be applied to one or both of the surfaces. The articles can involve wood-based panels, furniture (such as doors) or furniture components, i.e. constituents of furniture, or can involve automobile-interior components.

Examples

The present invention is further illustrated by the following examples, which are set forth to illustrate the present invention and is not to be construed as limiting thereof. Unless otherwise noted, all parts and percentages are by weight. Materials and Abbreviations

Tm: melting temperature, determined by DSC

Tg: glass transition temperature, determined by DSC

TPA: terephthalic acid

I PA: isophthalic acid

EG: ethylene glycol

Fn: functional number

OHv: OH value

DEG: diethylene glycol

NPG: neopentyl glycol

AA: adipic acid

BDO: 1 ,4-butanediol

HDO: 1 ,6-hexanediol

HDHP: 3-hydroxy-2,2-dimethylpropyl 3-hydroxy-2,2-dimethylpropanoate

NCOv: NCO value

DDA: Dodecanedioic acid

AA-co-TPA-co-HDO: copolymer of adipic acid, terephthalic acid and hexanediol in a molar ratio of 1 :1.6:2.6; Active amount: 100%, functionality 2; hydroxyl number: 27-34 mg KOH/g; molecular weight (Mw): 3750 g/mol; its DSC curves are shown in Figure 1.

AA-co-BDO: copolymer of adipic acid and 1 ,4-butane diol in a molar ratio of 1 :1 ; Active amount: 100%; functionality 2; hydroxyl number: 28 ± 1.5 mg KOH/g; molecular weight (Mw): 4000 g/mol; its DSC curves are shown in Figure 2.

DDA-co-HDO: Copolymer of DDA and HDO with molar ratio of about 1 :1 ; functionality 2; hydroxyl number: 27-34 mg KOH/g; molecular weight (Mw): 3500 g/mol.

PTHF 1000: homopolymer of tetrahydrofuran, functionality 2; hydroxyl number: about 112 mg KOH/g; molecular weight (Mw): 1000 g/mol; its DSC curves are shown in Figure 13.

PTHF 2000: homopolymer of tetrahydrofuran, functionality 2; hydroxyl number: about 56 mg KOH/g; molecular weight (Mw): 2000 g/mol; its DSC curves are shown in Figure 14.

Mixture of 5 parts by weight of DDA-co-HDO and 22.5 parts by weight of PTHF 2000; functionality 2; hydroxyl number: 51 mg KOH/g; its DSC curves are shown in Figure 3 (polyol B used in example 7).

Mixture of 17.5 parts by weight of DDA-co-HDO and 10 parts by weight of PTHF 2000; functionality 2; hydroxyl number: 44 mg KOH/g; its DSC curves are shown in Figure 4 (polyol B used in example 4).

Mixture of 10 parts by weight of DDA-co-HDO and 17.5 parts by weight of PTHF 2000; functionality 2; hydroxyl number: 46 mg KOH/g; its DSC curves are shown in Figure 5 (polyol B used in example 5).

Mixture of 10 parts by weight of DDA-co-HDO and 17.5 parts by weight of PTHF 1000; functionality 2; hydroxyl number: 83 mg KOH/g; its DSC curves are shown in Figure 6 (polyol B used in example 6).

Mixture of 7 parts by weight of DDA-co-HDO and 20.5 parts by weight of PTHF 2000; functionality 2; hydroxyl number: 50 mg KOH/g; its DSC curves are shown in Figure 7 (polyol B used in example 8). Dynacoll 7150: copolymer of 1 ,3-Benzenedicarboxylic acid, 1 ,4-benzenedicarboxylic acid, 2,2- dimethyl-1 ,3-propanediol, and 2,2’-oxybis[ethanol]; Active amount: 100%; functionality 2; hydroxyl number: 38-46 mg KOH/g; molecular weight (Mw): 2600 g/mol; Manufacturer: Evo- nik Industries AG; its DSC curves are shown in Figure 9. Tg of Dynacoll 7150 is 48.2 °C.

Hoopol F-39030: copolymer of terephthalic acid, isophthalic acid, neopentyl glycol, ethylene glycol and HDHP; functionality 2; hydroxyl number: 31-39 mg KOH/g; molecular weight (Mw): 3000 g/mol; Manufacturer: Synthesia Technology Europe, S.L.U.; its DSC curves are shown in Figure 10. Tg of Hoopol F-39030 is 26.2 °C.

AA-co-HDO: copolymer of adipic acid and 1 ,6-hexanediol; functionality 2; hydroxyl number: 27 - 34 mg KOH/g; molecular weight (Mw): 3500 g/mol; its DSC curves are shown in Figure 8.

Lupranate MES: Dipheylmethane-4,4’-diisocynate (4,4’-MDI); Active amount: 100%; Manufacturer: BASF.

B) Test methods

B1) DSC

The DSC test was based on ISO 11357-1 :2016 Plastics and carried out by utilizing the Discovery DSC from TA instruments, under 25 mL/min atmosphere.

B2) Green strength

The preparation of specimens for tensile shear test was based on DIN EN 1465 (“Adhesives - Determination of tensile lap-shear strength of bonded assemblies”). The reactive hot melt samples were melted in a 120 °C pre-heated oven for at least 0.5 hours, then applied onto the first wood substrate with an application area of 12.5 x 25 mm. The second wood substrate was put onto the first wood substrate as soon as possible. A 500 g metal bar was put on the two wood substrates to squeeze out the excess hot melt and the extra hot melt was removed by knife. The substrates were kept under pressure for 15 mins, then placed in an oven at 70 °C for 5 mins, thereafter the tensile strength was tested under an extension rate of 50 mm/min as soon as possible.

B3) Open time and Setting time

The reactive hot melt samples were firstly melted in the pre-heated oven at 120 °C for at least 0.5 hour, and then casted in a 500 pm film on a Teflon sheet at 120 °C using a drawdown bar. Then, the film including the Teflon sheet was put into a fume hood under 23 °C and 50% R.H. Paper strips were used to touch the film at regular intervals. The duration time from casting film to film sticky but no hot melt brought down by paper strip was recorded as setting time; the duration time from casting film to paper no longer sticking to film was recorded as the open time.

Preparing examples

Example 1 - Preparing the reactive polyurethane hot melt

Polyols 43% AA-co-TPA-co-HDO (polyol A), 28% AA-co-BDO (polyol B), 17% Dynacoll 7150 (as component (C)) were added in the reactor at room temperature. The reactor was sealed and heated to 120 °C under stirring and vacuumed to remove moisture. After the mixture was melted and no physical foaming was observed, the vacuuming was stopped and inert N2 was injected. Then, 12% Lupranat MES (4,4’-MDI) was added into the reactor in one shot (not dropwise) under moderate stirring. Upon charging isocyanate, the reactor was sealed, and stirrer speed was increased under vacuum. The reaction was carried out at 120 °C for 1.5 hours, then the reaction mixture (the reactive polyurethane hot melt) was cool down to 80 °C and poured out into an aluminum bags, sealed and vacuumed the bag thereafter.

The setting time, open time and green strength at 70 °C and NCO content of the resulted reactive polyurethane hot melt were shown in table 2 below. DSC curves of reactive polyurethane hot melt prepared in example 1 were shown in Figure 11.

Examples 2-8 and comparative examples 1 to 3

All procedures in example 1 were repeated except that the components as shown in following table 1 were used. The setting time, open time and green strength at 70 °C of the resulted hot melts were shown in table 2 below. DSC curves of reactive polyurethane hot melt prepared in example 2 were shown in Figure 12.

Table 1 : polyols and isocyanate and amount thereof

based on the total weight of all components for preparing the hot melt