Technical Field The present invention generally relates to a method for preparing a 2- hydroxyalkyl (meth) acrylate using an ion-exchange resin as a catalyst and, more particularly, to a method for preparing a 2-hydroxyalkyl (meth) acrylate using an anion or cation exchange resin as a catalyst, whereby the catalyst used can be easily separated and recovered for a reuse purpose.

Background Art 2-hydroxyalkyl (meth) acrylates are normally prepared by reacting an ethylene oxide/propylene oxide with an acrylic acid/methacrylic acid in the presence of a catalyst.

Examples of the catalyst include iron-, chrome-, amine-based catalysts, etc. Such catalysts form a homogeneous phase in the reaction solution and are hard to separate from the reaction product. The catalysts, which mostly contain metal components and form a mixture with an organic compound having a high boiling point, not only have an adverse effect on the products during distillation but also cause an environmental contamination when disposed together with the residuals of distillation. Those catalysts which are not recyclable are uneconomical and, if separable from the reaction products, still remains in the reaction products, in which case they may have an adversely catalytic effect on the products, i. e., they cause a thermal polymerization or decompositional reaction of the product during a distillation-based purification.

There was an attempts to overcome the problem by way of immobilization of catalyst. However this method led to a deterioration of catalyst activity, hence, reusing the catalyst was not possible.

Japanese Patent Laid-open Sho 57-42657, for example, disclosed a preparation of a 2-hydroxyalkyl (meth) acrylate using a trivalent chrome compound as a catalyst, in

which case the catalyst existing as a homogeneous phase in the reaction solution was difficult to remove from the reaction product.

Japanese Patent Laid-open Sho 52-23019 described a method for preparing a hydroxyalkyl (meth) acrylate in the presence of a chromic anhydride (Cr03) as a catalyst in water and/or alcohol. The catalyst, i. e., chromic anhydride in water and/or alcohol had the catalytic activity increased but was hard to separate from the reaction product, since it formed a homogenous phase in the reaction solution.

An alternative method for preparing a (3-hydroxyalkyl (meth) acrylate in the presence of a chrome compound as a catalyst was also disclosed in U. S. Patent No.

3,875,211. This method allowed the residual catalyst reusable after a thin film distillation of the product but required a second separation process of the catalyst from a viscous liquid mixture with the residual of the film distillation, in which case the catalyst was hard to separate in a pure state for a reuse purpose and deteriorated in the catalyst activity.

Also, the catalyst separation process performed in multiple stages was adverse to the preparing process and cost.

There is therefore a need for an approach to make the catalyst easily separable from the reaction product and also to make the catalyst reusable.

Disclosure of Invention To overcome the problems with the prior art, the inventors have made many studies on a method for preparing a 2-hydroxyalkyl (meth) acrylate with high yield as well as a catalyst easily separated from a reaction solution for a reuse purpose.

Consequently, the inventors have recognized that an ion-exchange resin is available as a catalyst in preparing a 2-hydroxyalkyl (meth) acrylate with high yield and easily separated from the reaction solution by a simple filtration.

The object of the present invention is to provide a method for preparing a 2- hydroxyalkyl (meth) acrylate using an ion-exchange resin as a catalyst.

The above object of the present invention will be understood and appreciated

evidently from the following detailed description.

Best Mode for Carrying out the Invention The present invention is directed to a method for preparing a 2-hydroxylalkyl (meth) acrylate, which comprises reacting an acrylic acid/methacrylic acid with an ethylene oxide/propylene oxide, characterized in that the reaction temperature is in the range of 65 to 95 °C and that an ion-exchange resin is used as a catalyst.

The ion-exchange resin as used herein may be either a cation exchange resin or an anion exchange resin of a gel, porous gel or macroporous type.

From the viewpoint of maintenance of the catalytic activity after iterative uses of the catalyst, the ion-exchange resin is preferably a gel type strongly alkaline anion exchange resin whose active group is a quaternary ammonium type II (ultimately, N (CH3) 2 (CH3CH2OH) C1). Examples of the anion exchange resin include Lewatit M- 600, manufactured by Bayer; Dowex SAR, manufactured by Dow; Diaion SA-20A, manufactured by MCI; Purolite A-300 ; Relit 2A, manufactured by RDI; Resin SBG-2, manufactured by Resin Tech; and Amberlite IRA-410 and Duolite A-116/A- 104, manufactured by Rohm and Hass.

Preferably, a strongly acidic cation exchange resin is one whose active group is a sulfonic acid. Examples of the cation exchange resin include Lewatit S-1OOBG, manufactured by Bayer; Dowex HCR-W2, manufactured by Dow; Diaion SK-1B (L), manufactured by MCI; Resin CG-8NaC, manufactured by Resin Tech; Purolit (DTm NRW-150; Relit C-240SPL, manufactured by RDI; and Amberlite IR-130C and Duolite C-225, manufactured by Rohm and Hass.

Alternatively, the ion-exchange resin as used herein may be of a gel, porous gel or macroporous type with an active group being a quaternary ammonium type I (ultimately, N (CH3) 3C1).

In particular, examples of the gel type ion-exchange resin include Lewatit M- 500, manufactured by Bayer; Dowex SBR, manufactured by Dow; Diaion SA-1OA,

manufactured by MCI; PuroliteT" A-600 ; Relite 3A, manufactured by RDI; Resin SBG-1, manufactured by Resin Tech; and Amberlite IRA-400 and Duolite A-109, manufactured by Rohm and Hass.

It is desirable to use the ion-exchange resin without drying, and in case it needs drying,, vacuum drying is preferred at 75 to 95 °C for 12 to 18 hours so as to remove 39 to 64 wt. % of moisture before use.

35.5 to 60 ml of an ion-exchange resin, 1 mol of an acrylic acid or methacrylic acid and 1 g of MEHQ as a polymerization inhibitor are added to a batch reactor under the nitrogen atmosphere with the initial pressure of 0 to 5 kg/cm2-G and in the temperature range of 65 to 95 °C, after which an ethylene oxide or propylene oxide is added to the batch reactor to yield a 2-hydroxyalkyl (meth) acrylate within 30 minutes to 7 hours.

It should be noted that the reaction temperature below 65 °C lowers the reaction rate to retard the reaction, whereas the reaction temperature above 95 ° causes a thermal polymerization of the product.

An inert gas is used to pressurize the ethylene oxide or propylene oxide and thereby participate in the reaction under a stable condition, i. e., with the initial pressure of 0 to 5 kg/cm2-G. The ethylene oxide or propylene oxide has to be added more than the theoretical reaction amount in order to raise the reaction rate, because it reacts with the acrylic acid or methacrylic acid at the mole ratio of 1: 1. However, an excess of the ethylene oxide or propylene oxide more than a predetermined amount causes a side reaction and thereby deteriorates the selectivity of the reaction.

Although the catalyst must be used in a large amount because the less catalyst causes an increase in the reaction time, an excess of the catalyst makes the volume of the catalyst greater than that of the reaction solution so that the catalyst is hard to disperse in the reaction solution.

According to the invention, the catalyst used in the reaction can be separated by a

simple filtration method, since the ion-exchange resin used as the catalyst does not form a homogeneous system with the reaction product unlike sulfuric acid or a chrome compound added as a catalyst in the prior art. The catalyst thus separated can be reused without a deterioration of the catalytic activity.

The abbreviations as used herein are defined as follows: EO: ethylene oxide; PO: propylene oxide; AA: acrylic acid; MAA: methacrylic acid; 2-HEA: 2-hydroxyethyl acrylate; 2-HEMA: 2-hydroxyethyl methacrylate ; 2-HPA: 2-hydroxypropyl acrylate; and 2-HPMA: 2-hydroxypropyl methacrylate.

The present invention will be described below in further detail with reference to the following examples, which are not intended to limit the present invention.

The reaction product in the examples was quantitatively analyzed with a gas chromatographic mass analyzer (GC-MASS) and a nuclear magnetic resonance (NMR) spectrometer.

Example 1: Preparation of 2-HEA The catalyst used in this example was a strongly alkaline gel type anion exchange resin whose active group is a quaternary ammonium type II, commercially available under the brand name of Amberlite IRA-410 C1 type manufactured by Rohm and Hass.

To use as a catalyst, 35.5 ml of the anion exchange resin was weighed and dried in a vacuum dryer at 75 °C for 16 hours.

35.5 ml of the ion-exchange resin, 1 mol of an acrylic acid and 1 g of MEHQ as a polymerization inhibitor were added to a batch reactor under the nitrogen atmosphere with the initial pressure of 3.5 kg/cm2-G and in the temperature range of 65 to 95 °C,

followed by adding 1.15 mol of an ethylene oxide to the reactor at 85 °C. After 5 hours of reaction, the resulting material was separated into the reaction product and the catalyst by a filtration.

An analysis of the product revealed that the conversion of the acrylic acid was 98. 0 mol%, the selectivity of the 2-hydroxyethyl acrylate 87.63 mol%, the yield of the 2- hydroxyethyl acrylate 85.87 mol%.

Example 2: Preparation of 2-HEA The catalyst used in this example was a strongly acidic gel type cation exchange resin commercially available under the brand name of Amberlite IR-120 Na type, manufactured by Rohm and Hass. To use as a catalyst, 35.5 ml of the anion exchange resin was weighed and dried in a vacuum dryer at 75 °C for 16 hours.

35.5 ml of the ion-exchange resin, 1 mol of an acrylic acid and 1 g of MEHQ as a polymerization inhibitor were added to a batch reactor under the nitrogen atmosphere with the initial pressure of 3.5 kg/cm2-G, followed by adding 1.15 mol of an ethylene oxide to the reactor at 85 °C. After 4 hours of reaction, the resulting material was separated into the reaction product and the catalyst by a filtration.

An analysis of the product revealed that the yield of the 2-hydroxyethyl acrylate was 26.84 mol%.

Example 3: Preparation of 2-HEA The catalyst used in this example was a strongly alkaline gel type anion exchange resin whose active group is a quaternary ammonium type I, commercially available under the brand name of Amberlite IRA-400 C1 type manufactured by Rohm and Hass. To use as a catalyst, 35.5 ml of the anion exchange resin was weighed and dried in a vacuum dryer at 75 °C for 16 hours.

35.5 ml of the ion-exchange resin, 1 mol of an acrylic acid and 1 g of MEHQ as a polymerization inhibitor were added to a batch reactor under the nitrogen atmosphere with the initial pressure of 3.5 kg/cm2-G, followed by adding 1.15 mol of an ethylene

oxide to the reactor at 85 °C. After 4 hours of reaction, the resulting material was separated into the reaction product and the catalyst by a filtration.

An analysis of the product revealed that the conversion of the acrylic acid was 99.0 mol%, the selectivity of the 2-hydroxyethyl acrylate 86.28 mol%, the yield of the 2- hydroxyethyl acrylate 85.42 mol%.

Experimental Example 1 The catalyst used in this example was an anion exchange resin commercially available under the brand name AmberliteTM IRA-410 Cl type, manufactured by Rohm and Hass.

To use as a catalyst, 35.5 ml of the anion exchange resin was weighed and dried in a vacuum dryer at 75 °C for 16 hours.

35.5 ml of the ion-exchange resin, 1 mol of an acrylic acid and 1 g of MEHQ as a polymerization inhibitor were added to a batch reactor under the nitrogen atmosphere with the initial pressure of 3.5 kg/cm2-G, followed by adding 1.15 mol of an ethylene oxide to the reactor at 65 °C. After 5 hours of reaction, the resulting material was separated into the reaction product and the catalyst by a filtration.

An analysis of the product revealed that the conversion of the acrylic acid was 71.38 mol%, the selectivity of the 2-hydroxyethyl acrylate 87.51 mol%, the yield of the 2-hydroxyethyl acrylate 62.46 mol%.

The reaction temperature below 65 °C lowered the reaction rate to increase the reaction time, whereas the reaction temperature above 95 ° caused a thermal polymerization.

Experimental Example 2 The catalyst used in this example was an anion exchange resin commercially available under the brand name Amberlite IRA-410 C1 type, manufactured by Rohm and Hass.

To use as a catalyst, 35.5 ml of the anion exchange resin was weighed and dried in a vacuum dryer at 75 °C for 16 hours.

35.5 ml of the ion-exchange resin, 1 mol of an acrylic acid and 1 g of MEHQ as a

polymerization inhibitor were added to a batch reactor under the nitrogen atmosphere with the initial pressure of 3.5 kg/cm2-G, followed by adding 1.0 mol of an ethylene oxide to the reactor at 75 °C. After 5 hours of reaction, the resulting material was separated into the reaction product and the catalyst by a filtration.

An analysis of the product revealed that the conversion of the acrylic acid was 77.04 mol%, the selectivity of the 2-hydroxyethyl acrylate 83.92 mol%, the yield of the 2-hydroxyethyl acrylate 64.65 mol%.

Experimental Example 3 The catalyst used in this example was an anion exchange resin commercially available under the brand name Amberlite IRA-410 Cl type, manufactured by Rohm and Hass.

To use as a catalyst, 35.5 ml of the anion exchange resin was weighed and dried in a vacuum dryer at 75 °C for 16 hours.

1 mol of an acrylic acid and 1 g of MEHQ as a polymerization inhibitor as well as the catalyst of a different amount were added to a batch reactor under the nitrogen atmosphere with the initial pressure of 3.5 kg/cm2-G, followed by adding 1.15 mol of an ethylene oxide to the reactor at 75 °C. After 5 hours of reaction, the resulting material was separated into the reaction product and the catalyst by a filtration.

An analysis of the product revealed that the conversion of the acrylic acid was 85.54 mol%, the selectivity of the 2-hydroxyethyl acrylate 87.32 mol%, the yield of the 2-hydroxyethyl acrylate 74.69 mol%.

Example 4: Preparation of 2-HEMA The catalyst used in this example was a strongly alkaline gel type anion exchange resin whose active group is a quaternary ammonium type II, commercially available under the brand name of Amberlite IRA-410 C1 type manufactured by Rohm and Hass.

To use as a catalyst, 35.5 ml of the anion exchange resin was weighed and dried in a vacuum dryer at 75 °C for 16 hours.

35.5 ml of the pre-treated ion-exchange resin, 1 mol of a methacrylic acid and 1 g

of MEHQ as a polymerization inhibitor were added to a batch reactor under the nitrogen atmosphere and 1.15 mol of an ethylene oxide was then added to the reactor at 85 °C.

After 6 hours of reaction, the resulting material was separated into the reaction product and the catalyst by a filtration.

An analysis of the product revealed that the conversion of the methacrylic acid was 96.20 mol%, the selectivity of the 2-hydroxyethyl methacrylate 93.21 mol%, the yield of the 2-hydroxyethyl methacrylate 89.66 mol%.

Example 5: Preparation of 2-HEMA The catalyst used in this example was a strongly alkaline macroporous type anion exchange resin whose active group is a quaternary ammonium type II, commercially available under the brand name of IRA-910 Cl type manufactured by Rohm and Hass.

The same procedures as described in Example 1 were performed under the same conditions, excepting that a different catalyst was used.

An analysis of the product revealed that the conversion of the methacrylic acid was 92.62 mol%, the selectivity of the 2-hydroxyethyl methacrylate 88.82 mol%, the yield of the 2-hydroxyethyl methacrylate 82.27 mol%.

Example 6: Preparation of 2-HEMA The catalyst used in this example was a strongly alkaline macroporous type anion exchange resin whose active group is a quaternary ammonium type I, commercially available under the brand name of AmberliteT" IRA-900 Cl type manufactured by Rohm and Hass.

The same procedures as described in Example 4 were performed under the same conditions, excepting that a different catalyst was used.

An analysis of the product revealed that the conversion of the methacrylic acid was 98.33 mol%, the selectivity of the 2-hydroxyethyl methacrylate 91.05 mol%, the yield of the 2-hydroxyethyl methacrylate 89.52 mol%.

Example 7: Preparation of 2-HEMA The catalyst used in this example was a strongly acidic gel type cation exchange resin commercially available under the brand name of Amberlite IR-120 Na type, manufactured by Rohm and Hass. To use as a catalyst, 35.5 ml of the anion exchange resin was weighed and dried in a vacuum dryer at 75 °C for 16 hours.

The same procedures as described in Example 4 were performed under the same conditions, excepting that a different catalyst was used.

An analysis of the product revealed that the yield of the 2-hydroxyethyl methacrylate was 40.9 mol%.

Example 8: Preparation of 2-HEMA The same procedures as described in Example 4 were performed under the same conditions, excepting that the temperature of the reactor was 60 °C.

An analysis of the product revealed that the yield of the 2-hydroxyethyl methacrylate was 50.0 mol%.

Example 9: Preparation of 2-HEMA The same procedures as described in Example 4 were performed under the same conditions, excepting that 0.9 mol of the ethylene oxide was added and the reaction occurred at 95 °C for 4 hours.

An analysis of the product revealed that the yield of the 2-hydroxyethyl methacrylate was 77.6 mol%.

Example 10: Preparation of 2-HEMA The same procedures as described in Example 4 were performed under the same conditions, excepting that the reaction occurred at 95 °C for 4 hours. And, the catalyst separated under the same reaction conditions was reused without a pre-treatment. The results are presented in Table 1.

Table 1 Number of Uses of Catalyst Yield of 2-HEMA (mol%) 1 82. 23 2 91. 91 3 93. 58 493.51 5 94. 04 6 93. 70 7 94. 03 8 93. 41 9 94. 32 10 93. 26 11 93. 87 12 92. 56 13 92. 78 14 93. 60 15 94. 21 16 94. 52

Example 11: Preparation of 2-HEMA The catalyst used in this example was a strongly alkaline gel type anion exchange resin whose active group is a quaternary ammonium type II, commercially available under the brand name of Amberlite IRA-410 OH type manufactured by Rohm and Hass. To use as a catalyst, 35.5 ml of the anion exchange resin was weighed and dried in a vacuum dryer at 75 °C for 16 hours.

35.5 ml of the pre-treated ion-exchange resin, 1 mol of a methacrylic acid and 1 g of MEHQ as a polymerization inhibitor were added to a batch reactor under the nitrogen atmosphere and 1.15 mol of an ethylene oxide was then added to the reactor at 85 °C.

After 6 hours of reaction, the resulting material was separated into the reaction product and the catalyst by a filtration.

An analysis of the product revealed that the conversion of the methacrylic acid was 94.83 mol%, the selectivity of the 2-hydroxyethyl methacrylate 95.40 mol%, the yield of the 2-hydroxyethyl methacrylate 90.47 mol%.

Example 12: Preparation of 2-HPA The catalyst used in this example was a strongly alkaline gel type anion exchange resin whose active group is a quaternary ammonium type II, commercially available under the brand name of IRA-410 Cl type manufactured by Rohm and Hass.

To use as a catalyst, 35.5 ml of the anion exchange resin was weighed and dried in a vacuum dryer at 75 °C for 16 hours.

35.5 ml of the pre-treated ion-exchange resin, 1 mol of an acrylic acid and 1 g of MEHQ as a polymerization inhibitor were added to a batch reactor under the nitrogen atmosphere and 1.15 mol of a propylene oxide was then added to the reactor at 85 °C.

After 6 hours of reaction, the resulting material was separated into the reaction product and the catalyst by a filtration.

An analysis of the product revealed that the conversion of the acrylic acid was 97.0 mol%, the selectivity of the 2-hydroxypropyl acrylate 91.1 mol%, the yield of the 2- hydroxypropyl acrylate 88.4 mol%.

Example 13: Preparation of 2-HPMA The catalyst used in this example was a strongly alkaline gel type anion exchange resin whose active group is a quaternary ammonium type II, commercially available under the brand name of IRA-410 Cl type manufactured by Rohm and Hass.

To use as a catalyst, 35.5 ml of the anion exchange resin was weighed and dried in a vacuum dryer at 75 °C for 16 hours.

35.5 ml of the pre-treated ion-exchange resin, 1 mol of a methacrylic acid and 1 g of MEHQ as a polymerization inhibitor were added to a batch reactor under the nitrogen

atmosphere and 1.15 mol of a propylene oxide was then added to the reactor at 85 °C.

After 6 hours of reaction, the resulting material was separated into the reaction product and the catalyst by a filtration.

An analysis of the product revealed that the conversion of the methacrylic acid was 98.40 mol%, the selectivity of the 2-hydroxypropyl methacrylate 92.2 mol%, the yield of the 2-hydroxypropyl methacrylate 90.7 mol%.

The present invention involves reacting an ethylene oxide or propylene oxide with an acrylic acid or methacrylic acid in the presence of an ion-exchange resin as a non-homogenous catalyst to produce a 2-hydroxyalkyl (meth) acrylate with a high yield and make the catalyst easily separable from the reaction solution.

Industrial Applicability So, the invention provides an environment-friendly method for preparing a 2- hydroxyalkyl (meth) acrylate without degradation of the product due to a decompositional reaction caused by the residual catalyst in the reaction solution during a distillation and thereby allowing separation and reuse of the catalyst.