Crystalline polyester polyol

Abstract

The present invention relates to polyester polyols obtained by reacting at least one diol having at least one primary hydroxy group and at least one secondary hydroxy group with a saturated aliphatic dicarboxylic acid having a carbon chain of at least 12 carbon atoms. The present invention also relates to adhesive compositions, particularly polyurethane adhesive compositions, containing the polyester polyols.

Description

[Technical field]

[0001] The present invention relates to crystalline polyester polyols obtained by reacting at least one diol having at least one primary hydroxyl group and at least one secondary hydroxyl group with a saturated aliphatic dicarboxylic acid having a carbon chain of at least 12 carbon atoms. The present invention further relates to adhesive compositions, in particular polyurethane adhesive compositions, comprising the polyester polyols. [Background technology]

[0002] Hydroxyl-terminated polyesters, so-called polyester polyols, are common building blocks in chemical synthesis, especially in the production of adhesives and coatings. Polyester polyols are known to be stable and can be easily modified, making them ideal reagents for use as prepolymer components in reactive adhesive systems. In particular, crystalline polyesters are often employed in adhesives due to their favorable effect on the properties of the resulting product, especially strength and elongation.

[0003] EP1149850 describes a crystalline polyester polyol for use in hot melt adhesives, which comprises a crystalline polyester polyol having a number average molecular weight of 1500 to 15000 obtained from a polybasic carboxylic acid component and an aliphatic hydrocarbon component comprising 1,10-decanediol and / or 1,12-dodecanediol, and the degree of crystallinity of the polyester polyol is 50%.

[0004] US2017 / 0204309 discloses a method for preparing a polyester hot melt adhesive with high viscosity and locally sensitive viscosity-temperature characteristics, comprising the steps of i) esterifying terephthalic acid, isophthalic acid, dodecanedioic acid, adipic acid, butanediol, dipropylene glycol, and hexanediol in the presence of tetrabutyl titanate as a catalyst, and ii) adding an antioxidant to the product obtained in step i) and carrying out a polycondensation reaction under reduced pressure to obtain a high viscosity hot melt adhesive with a melting point of 130-135°C and locally sensitive viscosity-temperature characteristics. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] European Patent Application Publication No. 1149850 [Patent Document 2] US Patent Application Publication No. 2017 / 0204309 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional crystalline polyester polyols have the disadvantage that they have a high melting point and are only suitable for high-temperature applications such as hot melt adhesives. However, such adhesives have high operating temperatures and are not suitable for the manufacture of temperature-sensitive materials or temperature-sensitive processes, so their applications are limited. In order to take advantage of the excellent properties of crystalline polyester polyols, it is desirable to be able to use crystalline polyester polyols in other systems. Therefore, the object of the present invention is to provide a polyester polyol that can be used in liquid systems for room temperature applications such as polyurethane adhesives, particularly two-component polyurethane adhesives. [Means for solving the problem]

[0007] It has surprisingly been found that the above objectives are achieved by a polyester polyol obtained from a reaction mixture comprising a diol and a saturated aliphatic dicarboxylic acid.

[0008] A first object of the present invention is therefore a polyester polyol obtained from a reaction mixture comprising: a) at least one diol having at least one primary hydroxy group and at least one secondary hydroxy group; and b) at least one saturated aliphatic dicarboxylic acid having a carbon chain of at least 12 carbon atoms. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a DSC diagram of a comparative polyester polyol obtained from a reaction mixture comprising 1,4-pentanediol and a C10 dicarboxylic acid. [Diagram 2] FIG. 2 is a DSC diagram of a polyester polyol of the present invention obtained by reacting 1,4-pentanediol with dicarboxylic acids having carbon chains of C12 and C14, respectively. [Diagram 3] FIG. 2 is a DSC diagram of a polyester polyol of the present invention obtained by reacting 1,4-pentanediol with dicarboxylic acids having carbon chains of C12 and C14, respectively. [Figure 4] FIG. 2 is a DSC diagram of a polyester polyol of the present invention obtained by reacting 1,3-butanediol with a dicarboxylic acid having a carbon chain of C12. [Diagram 5] FIG. 2 is a DSC diagram of a polyester polyol of the present invention obtained by reacting 1,2-propylene glycol with a dicarboxylic acid having a carbon chain of C12. [Figure 6] FIG. 2 is a DSC diagram of a comparative polyester polyol obtained by reacting 1,4-butanediol with a dicarboxylic acid having a carbon chain of C12. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The expression "carbon chain" when used in reference to a dicarboxylic acid means a linear carbon chain separating two carboxylic acid groups, which chain is terminated at both ends by a carboxylic acid group, with the carbons of the carboxylic acid group being used as the starting and ending points for determining the number of carbon atoms in the carbon chain.

[0011] The molecular weights of the components in the reaction mixture are determined according to standard procedures, for example by GPC or end group titration (OH value determination).

[0012] Surprisingly, it has been found that the polyester polyol of the present invention is crystalline and has a low melting point, and therefore is particularly suitable for temperature-sensitive applications. In a preferred embodiment, the polyester polyol of the present invention has a crystalline morphology at room temperature or lower. Room temperature in the present invention refers to a temperature of 23 to 25° C. under a pressure of 1000 to 1020 hPa.

[0013] As used herein, polyester polyols exhibiting crystalline morphology refer to polyester polyols in which the majority of polymer chains are at least partially aligned. The morphology of polyester polyols can be determined, for example, by DSC, and the degree of crystallinity is usually represented by clear (defined) melting and crystallization peaks in the diagram. On the other hand, amorphous materials are characterized by the absence of clear peaks in the DSC diagram.

[0014] Surprisingly, it has been found that the polyester polyols of the present invention can be employed in systems that are liquid at ambient temperatures, particularly room temperature, and exhibit advantageous properties normally associated with polyester polyols that are solid at ambient temperatures, such as improved strength and elongation in the resulting products.

[0015] Various processes for producing crystalline polyester polyols are known to those skilled in the art. However, said crystalline polyester polyols usually have a melting point or softening point much higher than room temperature. Surprisingly, it has been found that the melting point of the polyester polyols of the present invention can be adapted by adopting a suitable diol. Polyester polyols that are liquid at room temperature and exhibit high crystallinity are obtained in particular from diols in which at least one hydroxyl group is sterically hindered with a dicarboxylic acid having a carbon chain with 12 or more carbon atoms.

[0016] In a preferred embodiment, the at least one diol is selected from the group consisting of 1,2-propanediol, 1,3-butanediol, 1,4-pentanediol, 1,5-hexanediol, 1,6-heptanediol and 1,7-octanediol.

[0017] Surprisingly, it has been found that the melting point of the polyester polyols of the present invention can be adjusted as desired by selecting the appropriate dicarboxylic acid, although care must be taken to ensure that the melting point of the polyester polyol is in a range suitable for use at ambient temperatures.

[0018] Thus, in a preferred embodiment, the at least one dicarboxylic acid comprises a carbon chain of 12 to 24 carbon atoms, preferably 12 to 22 carbon atoms, in particular 12 to 18 carbon atoms. In a particularly preferred embodiment, the at least one dicarboxylic acid is selected from the group consisting of 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, 1,16-hexadecanedioic acid and 1,18-octadecanedioic acid, and the anhydrides, esters and chlorides derived therefrom.

[0019] In particularly preferred embodiments, the diols and dicarboxylic acids from which the polyester polyols of the present invention are derived are obtained from renewable resources. Such compounds obtained from renewable resources are generally referred to as "bio-based" compounds, as opposed to the more common petroleum-based compounds.

[0020] The polyester polyol of the present invention has a low melting point and is particularly excellent in crystal form. Conventional crystalline polyester polyols usually have a high melting point of more than 80°C, whereas the polyester polyol of the present invention has a melting point in a low temperature range of less than 60°C, enabling more flexible application in many technical fields. In a preferred embodiment, the polyester polyol of the present invention has a melting point of -30 to 50°C, preferably -15 to 30°C, measured by DSC at a heating rate of 10K / min.

[0021] In the course of the present invention, it was further surprisingly found that polyester polyols obtained by reacting a diol having primary and secondary hydroxyl groups with a dicarboxylic acid having 12 carbon atoms recrystallize on melting. This crystallization behavior can be observed by DSC as an exothermic crystallization peak that overlaps with an endothermic melting peak before reaching the liquid state. The polyester polyols of the present invention show good melting properties, which are believed to be related to the recrystallization behavior. In a preferred embodiment, the polyester polyols of the present invention are thus obtained from the reaction of a saturated aliphatic dicarboxylic acid having a carbon chain of 12 carbon atoms with a diol having at least one primary hydroxyl group and at least one secondary hydroxyl group. In this connection, it was surprisingly found that the polyester polyols of the present invention are particularly suitable for the production of flexible films, in particular flexible films based on polyurethane adhesive compositions.

[0022] In order to adjust the properties of the polyester polyols of the present invention, in addition to the at least one diol and the at least one dicarboxylic acid, other components may be included in the reaction mixture. It has been found to be particularly advantageous if the reaction mixture includes further diols in addition to the at least one diol. In a preferred embodiment, the reaction mixture therefore includes an additional diol, preferably selected from the group consisting of 1,3-propanediol, diethylene glycol, NPG, ethylene glycol, 1,4-butanediol and 1,6-hexanediol.

[0023] The reaction mixture from which the polyester polyols of the invention are obtained may also contain an additional acid, preferably in an amount of 0-20 mol-%, preferably 0-10 mol-%. The additional acid is preferably selected from the group consisting of succinic acid, adipic acid, sebacic acid, azelaic acid, isophthalic acid, orthophthalic acid, terephthalic acid, furandicarboxylic acid, itaconic acid, and the anhydrides, chlorides and esters derived from these acids. Surprisingly, it has been found that the presence of an additional acid leads to an improvement in the mechanical strength of the final adhesive film composition comprising the polyester polyols of the invention.

[0024] The reactivity of the polyester polyol of the present invention may be adjusted as necessary according to the subsequent use. In a more preferred embodiment, therefore, the polyester polyol of the present invention has a hydroxyl value (OH value) of 5 to 150 mgKOH / g, 10 to 100 mgKOH / g. The hydroxyl value is an index showing the content of free hydroxyl groups contained in a chemical substance, and is usually expressed in milligrams as the mass of potassium hydroxide (KOH) corresponding to the hydroxyl group content of 1 g of the chemical substance. Conventionally, the hydroxyl value has been measured by an analytical method in which the free hydroxyl groups of a substance are acetylated using acetic anhydride in a pyridine solvent. The hydroxyl value can be determined based on DIN 53240.

[0025] The hydroxyl value of the polyester polyol of the present invention can be adjusted, for example, by the ratio of diol to dicarboxylic acid in the reaction mixture. In a preferred embodiment, the molar ratio of at least one diol to at least one dicarboxylic acid in the reaction mixture is 1.5:1 to 1:1, preferably 1.2:1 to 1:1.

[0026] Surprisingly, it has been found that, despite the high crystallinity of the polyester polyol of the present invention, the molecular weight of the polyester polyol of the present invention can be achieved within a range suitable for adhesive applications. In a preferred embodiment, the polyester polyol of the present invention has an average molecular weight Mn measured by GPC of 1000 to 25000 g / mol, preferably 2000 to 10000 g / mol. The molecular weight of the polyester polyol of the present invention can be measured, in particular, by GPC using THF as an eluent.

[0027] The polyester polyol of the present invention is particularly suitable for adhesive applications, especially for liquid systems.The presence of the polyester polyol of the present invention in the adhesive allows the advantageous properties of crystalline polyester polyol to be enjoyed without the need to melt the adhesive.Instead, an adhesive is obtained that can be used and applied at room temperature.A further object of the present invention is therefore an adhesive that comprises the polyester polyol of the present invention.

[0028] Due to their low melting points, the polyester polyols of the present invention are very energy efficient and can be applied in temperature sensitive applications. However, in a preferred embodiment, the adhesives of the present invention are preferably liquid at a temperature of 25° C., which eliminates the need to heat the adhesive to melt it before application. It also avoids problems caused by recrystallization of the adhesive after application and solidification during storage.

[0029] The polyester polyols of the present invention can be applied to many adhesive systems. Preferably, the adhesives of the present invention are polyurethane adhesives, in particular two-component polyurethane adhesives (2K systems) and one-component polyurethane adhesives (1K systems).

[0030] A further object of the present invention is the use of the polyester polyols according to the invention in adhesives and coatings. In a preferred embodiment, the polyester polyols according to the invention are used in polyurethane adhesives.

[0031] The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the scope or spirit of the invention in any way. EXAMPLES

[0032] Working Example: The polyester polyol of the present invention is obtained by mixing at least one diol and at least one dicarboxylic acid, and heating the reaction mixture to a temperature of 140 to 240° C. After the reaction was completed, the mixture was cooled to room temperature under an argon atmosphere, and the obtained polyester polyol was analyzed by DSC at a heating rate of 10 K / min.

[0033] 1 shows a DSC diagram of a comparative polyester polyol obtained from a reaction mixture comprising 1,4-pentanediol and a dicarboxylic acid having a carbon chain length of C10. The amorphous nature of the polyester polyol can be clearly seen in the DSC.

[0034] 2 and 3 are DSC diagrams of the polyester polyols of the present invention obtained by reacting 1,4-pentanediol with dicarboxylic acids having carbon chains of C12 and C14, respectively. The unexpected crystalline morphology of each polyester polyol can be clearly depicted by the distinct melting peaks in the DSC diagrams.

[0035] Figure 4 shows the DSC diagram of the polyester polyol of the present invention obtained by reacting 1,3-butanediol with a dicarboxylic acid having a carbon chain length of C12. The unexpected polymorphous properties of this polyester polyol are evident in the clear crystallization peaks upon melting.

[0036] 5 is a DSC diagram of the polyester polyol of the present invention obtained by reacting 1,2-propylene glycol with a dicarboxylic acid having a carbon chain of C12. The polymorphism of the polyester polyol is clearly shown by a clear crystallization peak when melted.

[0037] 6 shows a DSC diagram of a comparative polyester polyol obtained by reacting 1,4-butanediol with a dicarboxylic acid having a carbon chain length of C12, which does not exhibit the polymorphism observed in association with similar polyester polyols of the invention obtained by reacting the same dicarboxylic acid with 1,3-butanediol, 1,4-pentanediol, and 1,2-propylene glycol, respectively. Preferred aspects of the invention include the following. [1] A crystalline polyester polyol, the polyester polyol being a reaction mixture comprising: a) at least one diol having at least one primary hydroxy group and at least one secondary hydroxy group; and b) at least one saturated aliphatic dicarboxylic acid having a carbon chain of at least 12 carbon atoms; A crystalline polyester polyol obtained from [2] The polyester polyol according to [1], wherein the at least one diol is selected from the group consisting of 1,2-propanediol, 1,3-butanediol, 1,4-pentanediol, 1,5-hexanediol, 1,6-heptanediol, and 1,7-octanediol. [3] The polyester polyol according to any one of the preceding paragraphs, wherein the at least one dicarboxylic acid has a carbon chain length of 12 to 24 carbon atoms, preferably 12 to 22 carbon atoms, and particularly preferably 12 to 18 carbon atoms. [4] The polyester polyol according to any one of the preceding paragraphs, characterized in that the at least one dicarboxylic acid is selected from the group consisting of 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, 1,16-hexadecanedioic acid, and 1,18-octadecanedioic acid, and the anhydrides, esters, and chlorides derived from these acids. [5] The polyester polyol according to any one of the above items, characterized in that the polyester polyol has a melting point of −30 to 50° C., preferably −15 to 30° C., as measured by DSC at a heating rate of 10 K / min. [6] The polyester polyol according to any one of the preceding paragraphs, characterized in that the reaction mixture contains an additional diol, preferably selected from the group consisting of 1,3-propanediol, diethylene glycol, NPG, ethylene glycol, 1,4-butanediol and 1,6-hexanediol. [7] The polyester polyol according to any one of the preceding paragraphs, characterized in that the polyester polyol has a hydroxyl value (OH value), measured according to DIN 53240, of 5 to 150 mg KOH / g, preferably 10 to 100 mg KOH / g. [8] The polyester polyol according to any one of the preceding paragraphs, characterized in that the reaction mixture further comprises an additional dicarboxylic acid, preferably selected from the group consisting of succinic acid, adipic acid, sebacic acid, azelaic acid, isophthalic acid, orthophthalic acid, terephthalic acid, furandicarboxylic acid, itaconic acid, and the anhydrides, chlorides and esters derived therefrom. [9] The polyester polyol according to any one of the preceding paragraphs, characterized in that the at least diol and the at least one dicarboxylic acid are present in the reaction mixture in a molar ratio of 1.5:1 to 1:1, preferably 1.2:1 to 1:1.

[10] An adhesive comprising the polyester polyol according to any one of [1] to [9].

[11] The adhesive according to

[10] , characterized in that the adhesive is liquid at a temperature of 25°C.

[12] The adhesive according to any one of [9] to

[11] , characterized in that the adhesive is a polyurethane adhesive.

[13] Use of the polyester polyol according to any one of [1] to [9] in an adhesive.

[14] Use of the composition according to

[13] in a polyurethane adhesive.

Claims

1. A crystalline polyester polyol that is liquid at room temperature, said polyester polyol being obtained by subjecting a reaction mixture comprising: a) at least one diol having at least one primary hydroxy group and at least one secondary hydroxy group; and b) at least one saturated aliphatic dicarboxylic acid having a carbon chain of at least 12 carbon atoms; A crystalline polyester polyol obtained from

2. 2. The polyester polyol of claim 1, wherein the at least one diol is selected from the group consisting of 1,2-propanediol, 1,3-butanediol, 1,4-pentanediol, 1,5-hexanediol, 1,6-heptanediol and 1,7-octanediol.

3. 3. The polyester polyol according to claim 1, wherein said at least one dicarboxylic acid comprises a carbon chain of from 12 to 24 carbon atoms.

4. 3. The polyester polyol according to claim 1, wherein said at least one dicarboxylic acid comprises a carbon chain of from 12 to 22 carbon atoms.

5. 5. The polyester polyol according to claim 1, wherein the at least one dicarboxylic acid is selected from the group consisting of 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, 1,16-hexadecanedioic acid and 1,18-octadecanedioic acid, and the anhydrides, esters and chlorides derived from these acids.

6. 6. The polyester polyol of claim 1, wherein the reaction mixture comprises an additional diol selected from the group consisting of 1,3-propanediol, diethylene glycol, NPG, ethylene glycol, 1,4-butanediol and 1,6-hexanediol.

7. 7. The polyester polyol according to claim 1, wherein the polyester polyol has a hydroxyl value (OH value), measured according to DIN 53240, of 5 to 150 mg KOH / g.

8. 8. The polyester polyol of claim 1, wherein the reaction mixture further comprises an additional dicarboxylic acid selected from the group consisting of succinic acid, adipic acid, sebacic acid, azelaic acid, isophthalic acid, orthophthalic acid, terephthalic acid, furandicarboxylic acid, itaconic acid, and the anhydrides, chlorides and esters derived therefrom.

9. 9. The polyester polyol of claim 1, wherein the at least one diol and the at least one dicarboxylic acid are present in the reaction mixture in a molar ratio of from 1.5:1 to 1:

1.

10. An adhesive comprising the polyester polyol according to any one of claims 1 to 9.

11. 11. The adhesive of claim 10, characterized in that the adhesive is liquid at a temperature of 25°C.

12. The adhesive according to any one of claims 10 to 11, characterized in that the adhesive is a polyurethane adhesive.

13. Use of the polyester polyol according to any one of claims 1 to 9 in an adhesive.

14. 14. The use according to claim 13 in a polyurethane adhesive.

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