TECHNICAL FIELD

The present invention relates to the field of chemistry, in particular, to the chain extender for preparing the self-healing polyurethane, the process for preparing a self-healing polyurethane and polyurethane thereof.

BACKGROUND OF THE INVENTION

Carbon dioxide has been released enormously from the combustion in many industries such as coal industry, petrochemical, and power plant, etc. Therefore, carbon dioxide is the main reason in greenhouse effect, which increases earth surface temperature. However, carbon dioxide is the renewable resource. Therefore, the use of carbon dioxide as the precursor in the synthesis of other compounds is not only the alternative to the use of non-renewable resource such as petroleum, but also another way to reduce the greenhouse effect.

There have been reports that carbon dioxide has been studied for using as Ci building block in the production of valuable chemicals such as urea, salicylic acid, cyclic carbonate, and lactone, etc.

Lactone is the interesting cyclic estery group because it can be used as the precursor for the production of other derivatives that can be valuable as been disclosed in the synthesis of delta- lactone from the reaction from carbon dioxide and 1,3-butadiene in the patent document PCT/TH2017/000080.

Polyurethane is the synthetic polymer having several outstanding properties leading to its well-known applications such as elastic foam, hard foam, protection coating, adhesive, and elastomer, etc. Polyurethane can be synthesized from the reaction between polyol, isocyanate, and chain extender, wherein polyurethane to be used has both linear and cross linked chains depending on the needed properties in such works. One of the popular ways to prepare cross linked polyurethane is the selection of the chain extender having more functional group in order to crosslink between polymer chains. Therefore, it can be linkage and chain extender in the same molecule. In Macromol. Rapid. Commun. 2017, 38, 1700450, Liu et al. prepared the polyurethane with shape memory property by synthesizing polyurethane from the reaction between hexamethylene diisocyanate and polycaprolactone using trimethylolpropane mono allyl ether containing 2 hydroxyl groups and double bond as the chain extender and cross link point. The obtained polyurethane had structure that can be post crosslinked with better shape memory property.

In J. Coat. Technol. Res. 2016, 13 (4), 667-676, Liao and Sun developed the chain extender for the synthesis of polyurethane containing 2 hydroxyl groups and 2 ketone groups in the molecule. It was found that the use of said chain extender enable the preparation of polyurethane containing ketone which could be cross linked after subjected to the reaction between ketone group on the polymer chain and the amino group in the cross linkage structure at room temperature.

In Mater. Design 2017, 127, 106-114, Mi et al. added thiol into polyurethane chain via the use of the chain extender having hydroxyl and thiol as compositions, enable the obtained polyurethane to be cross linked after subjected to disulfide formulation. It was also found that the cross linking could improve the strength, elastic, and heat stability properties.

Patent document US4931487 discloses the synthesis of polyurethane having high heat stability and strength properties by using chain extender containing functional group selected from heterocyclic diamines, diaromatic disulfides, alkyl ethers of halogen-substituted aromatic diamines, polysubstituted alkyl diamines, and alkyl acid esters of halogen-substituted diamino phenols.

Patent document CN105885002A discloses the preparation process for self-healing polyurethane using the chain extender containing disulfide for dihydric alcohol and diisocyanate. However, said chain extenders had limitations in the property improvement to be the chain extender and cross linkage in the same structure which affected the ability to improve polyurethane properties.

Therefore, this invention aims to develop the chain extender to have variety of functional groups in its structure comprising double bond group, hydroxyl group, and carboxyl group suitable to be applied as the novel chain extender for the synthesis of polyurethane and can form the derivatives that effective in the preparation of the self-healing polyurethane. Moreover, the chain extender according to the invention can be easily synthesized, safe, and employing carbon dioxide as its precursor. SUMMARY OF INVENTION

The present invention relates to a chain extender for preparing a self-healing polyurethane, comprising double bond group, hydroxyl group, and carboxyl group as shown in structure (I) or derivatives thereof:

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows proton-nuclear magnetic resonance (1H NMR) of polyurethane sample 1 in chloroform-D (CDC13) solvent.

Figure 2 shows proton-nuclear magnetic resonance (1H NMR) of polyurethane sample 2 in chloroform-D (CDC13) solvent.

DESCRIPTION OF THE INVENTION

The present invention relates to the chain extender for preparing the self-healing polyurethane, wherein said chain extender comprising double bond group, hydroxyl group, and carboxyl group or derivative thereof, which can be described according to the following embodiments.

Any aspect that being described here is meant to include the application to the other aspects of this invention, unless stated otherwise.

Technical terms or scientific terms used here have definitions as by person skilled in the art unless stated otherwise.

Any tools, equipment, methods, or chemicals named here mean tools, equipment, methods, or chemicals being used commonly by person skilled in the art unless stated otherwise that they are tools, equipment, methods, or chemicals specific only in this invention.

Use of singular noun or singular pronoun with“comprising” in claims or specification means “one” and including“one or more”,“at least one”, and“one or more than one” too.

All compositions and/or methods disclosed and claims in this application aim to cover embodiments from any action, performance, modification, or adjustment without any experiment that significantly different from this invention, and obtain with object with utility and resulted as same as the present embodiment according to person ordinary skilled in the art although without specifically stated in claims. Therefore, substitutable or similar object to the present embodiment, including any little modification or adjustment that clearly seen by person skilled in the art should be construed as remains in spirit, scope, and concept of invention as appeared in appended claims.

Throughout this application, term“about” means any number that appeared or showed here that could be varied or deviated from any error of equipment, method, or personal using said equipment or method.

Hereafter, invention embodiments are shown without any purpose to limit any scope of the invention.

This invention relates to the chain extender for preparing a self-healing polyurethane, wherein said chain extender comprising double bond group, hydroxyl group, and carboxyl group as shown in structure (I) or derivatives thereof:

In one embodiment, the chain extender according to the invention has structure as shown in structure (II):

wherein, R1 and R2 represents independent group selected from hydrogen, halogen, alkyl, alkyl halide, alkoxy, ether, amine, alternatively are alkenyl, alkynyl, phenyl, benzyl, or cyclic hydrocarbon comprising hetero atom; and

n is integer from 1 to 30.

Preferable, the chain extender as in structure (II) has n from 2 to 15, wherein R1 and R2 is alkyl group that may be selected from octyl, -(CH2)8-) or (hexyl, -(CH2)6-).

In one embodiment, the chain extender as in structure (I) can be synthesized from delta- lactone using base that may be selected from sodium hydroxide or potassium hydroxide in solvent. The reaction may be performed from 20 - 150 °C for about 1 - 70 hours, and the mole ratio of delta-lactone to base is from 1 to 0.1 to 1 to 5. In one aspect, the preparation of said chain extender may further comprising the drying step if necessary. The said step may be selected from but not limited to stir drying and vacuum drying.

In one embodiment, the chain extender as in structure (II) may be prepared by the following method.

- thiol-ene reaction of the chain extender as in structure (I) and dithiol using photoinitiator in solvent at the temperature from 0 to 100 °C for about 1 to 50 hours under light source with wavelength 10 - 600 nm.

- oxidation by adding oxidant at the temperature from 0 to 100 °C for about 0.1 to 10 hours.

In one aspect, dithiol is alkyl dithiol, ether dithiol, phenyl dithiol, or said compounds that further comprising hetero atom or mixture thereof.

In one aspect, the photoinitiator may be selected from hydrogen peroxide, acetophenone, benzyl, and benzoin, benzophenone, cationic, thioxanthones, or mixture thereof.

In one aspect, antioxidant may be selected from fluorine, chlorine, bromine, iodine, hydrogen peroxide, chloride compound, bromide compound, iodine compound, oxygen, ozone, chromium compound, manganese compound, or mixture thereof.

In one aspect, the preparation process of the chain extender as in structure (II) may further comprising the drying step if necessary. The said step may be selected from but not limited to stir drying and vacuum drying.

In another embodiment, this invention relates to the process for preparing the self-healing polyurethane, comprising:

a) preparing of polyurethane by reaction between isocyanate and polyol at the temperature from 50 to 100 °C; and

b) adding of the chain extender comprising double bond group, hydroxyl group, and carboxyl group as shown in structure (I) or derivatives thereof into mixture in a) and subjecting the obtained mixture to reaction at the temperature of 50 - 100 °C:

In one embodiment, the chain extender in b) may be selected from the chain extender according to the invention as shown in structure (II) having Rl, R2, and n as described above.

In one embodiment, isocyanate and polyol in a) has mole ratio of isocyanate to polyol in from 0.1 to 1.

In one embodiment, the chain extender in b) has mole ratio of hydroxyl group in the chain extender to isocyanate in from 0.1 to 1. In one embodiment, polyol is selected from polyether polyol, polyester polyol, polyester- ether polyol, polyethylene glycol, polycarprolactone, polycarbonate, or mixture thereof.

In one embodiment, isocyanate is selected from isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), 4,4'-methylenebis(phenyl isocyanate) (MDI), 4,4’ -methylene dicyclohexyl diisocyanate (HMDI), toluene diisocyanate (TDI), or mixture thereof.

In one embodiment, the mixture in step b) further comprising the aprotic solvent selected from dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, or dimethylacetamide, or mixture thereof.

In one aspect, the preparation process of polyurethane according to this invention may further comprising the dehydration step from the polyol prior to the reaction if necessary. The said step may be selected from but not limited to vacuum drying.

In one aspect, the preparation process of polyurethane according to this invention may further comprising the purification step for the synthesized polyurethane if necessary. The said step may be selected from but not limited to precipitation.

In one aspect, the preparation process of polyurethane according to this invention may further comprising the drying step for the synthesized polyurethane if necessary. The said step may be selected from but not limited to oven drying or vacuum drying.

In another embodiment, this invention relates to the self-healing polyurethane comprising pre-polyurethane obtained from isocyanate and polyol and the chain extender comprising double bond group, hydroxyl group, and carboxyl group as shown in structure (I) or derivative thereof.

In one embodiment, isocyanate, polyol, and chain extender may be selected from compounds as described above.

The following example is only for demonstrating the embodiment of this invention, not for limiting the scope of this invention in any way.

The Preparation of the chain extender as shown in structure (I)

Sodium hydroxide solution (0.2 mol/L) was added into about 0.5 g of delta-lactone and subjected to heat at about 60 - 80 °C for about 8 - 10 hours. Then, the pH was adjusted to about 1. Product was separated by diethylether. Sodium sulfate was added for dehydration, followed by vacuum drying. The obtained product was the chain extender according to structure (I). The percentage yield was about 77 %.

The Preparation of the chain extender as shown in structure (II) About 0.15 g of the mixture solution from the chain extender according to structure (I), about 0.31 g of 1,8-octanedithiol, and 0.02 g of acetone phenone compound in ethanol solvent were prepared. The mixture was stirred and subjected to light source at the wavelength about 300 - 400 nm for about 10 - 12 hours. At the end of the reaction, the product was dried by vacuum drying.

Then, 1.30 mg of sodium iodide and 0.0968 mg of hydrogen peroxide in solvent were added into substance obtained from the above reaction and stirred at room temperature for about 20 - 30 minutes. At the end of the reaction, the product was dried by vacuum drying, obtaining the chain extender according to structure (II) with high purity. The percentage yield was more than 90 %. R1 and R2 were oxtyl, and n was 15.

The preparation of self-healing polyurethane

One objective of the invention is to show that the chain extender according to this invention can be used to prepare variety of self-healing polyurethanes, wherein isocyanate and polyol used in the preparation of these polyurethanes were aimed to be selected samples and not for limitation of this scope of the invention.

The self-healing polyurethane according to the invention could be prepared by the following methods.

Example 1

Pre-polyurethane was prepared by the reaction from about 1.5 mmole of hexamethylene diisocyanate and about 0.75 mmole of polyethylene glycol at the temperature about 70 °C for about 3 hours under nitrogen atmosphere. Then, about 0.75 mmole of the chain extender having structure (II) obtained from the method described above in anhydrous tetrahydrofuran solvent was added. Then, the mixture was stirred for the reaction at the temperature about 70 °C for at least 3 hours under nitrogen atmosphere. At the end of the reaction, the product was purified by precipitation in distilled water and vacuum drying.

The obtained polyurethane was analyzed for proton-nuclear magnetic resonance (1H NMR) signal in order to confirm the formation of polyurethane. The result was shown in figure 1.

Example 2

The self-healing polyurethane was prepared as method described in example 1 using 4,4- methylenebis(phenylisocyanate) and polyethyleneglycol. The obtained polyurethane was analyzed for proton-nuclear magnetic resonance (1H NMR) signal in order to confirm the formation of polyurethane. The result was shown in figure

2.

BEST MODE OR PREFERRED EMBODIMENT OF THE INVENTION

Best mode or preferred embodiment of the invention is as provided in the description of the invention.