HK1118799B - Esterification process of polyols with tertiary alkyl substituted acids - Google Patents

Description

Process for esterifying polyols with tertiary alkyl-substituted acids

The present invention relates to a process for the preparation of polyol esters from tertiary alkyl acids with reduced homopolymerization of the polyol. Esters of trialkyl acetic acids are known to have high hydrolysis resistance and to enhance the hydrolytic stability of adjacent esters. They are therefore well suited as end-use applications for coatings and/or construction where hydrolysis resistance is required. This property is due to the steric hindrance provided by the trialkyl group of the acid. Thus, polyols partially esterified with trialkyl acetic acids are suitable as building blocks in resin synthesis for coatings or construction applications.

Esterification of alcohols with trialkylacetic acids is difficult and thus the acid is used even as a catalyst to promote esterification of less sterically hindered acids with alcohols (WO 0144156).

It is known from journal.am.oil.chem soc., Vol45, 5-10, 1968, month 1 to promote esterification of sterically hindered acids with alcohols or polyols using conventional esterification catalysts. According to the authors, the conditions used are more severe than those of the non-sterically hindered acids or alcohols, and in the case of polyols they use an excess of acid to achieve complete esterification of the alcohol function.

It is also known to promote esterification of highly branched (sterically hindered) acids by using unconventional esterification catalysts. In the case of monohydric alcohols, the use of chlorosilanes (Bull. chem. Soc. Jpn, 54, 1267-1268) is effective because alkoxysilanes are generated as active substances. However, no technique is given for partial esterification of polyols using this process.

It is known from the cited publications that the prior art solutions suffer from the disadvantages such as the use of expensive catalysts, or that the conditions cannot be used to promote the partial esterification of polyols to produce predominantly monoesters of the polyols with only small amounts of higher molecular weight compounds resulting from etherification side reactions.

There is a strong need in the industry for a process that can use conventional esterification catalysts to produce predominantly monoesters of polyols, since these monomers have been found to be useful as valuable building blocks in further resin synthesis.

As a result of extensive research and experimentation, it has now surprisingly been found that the selection of specific process conditions in combination with specific catalysts enables the production of predominantly low viscosity hydroxy-functionalized monoesters from tertiary alkyl carboxylic acids and polyols.

It has now been surprisingly found that the use of sulfonic acid derivatives under mild thermal conditions is an effective combination to produce monoesters of polyols without significant formation of polyethers. The polyethers are considered to be undesirable homopolymer byproducts and are believed to be the reaction product between alcohol functional groups; this reaction is a competing reaction when esterification is slow or when an excess of alcohol over acid functionality is used. The present invention provides a solution to the problem faced by the improved selectivity of the preparation of monoesters from polyols and sterically hindered carboxylic acids.

The process for the above selective esterification reaction is obtained at a temperature lower than 180 ℃ in the presence of an acidic catalyst.

According to a preferred embodiment, the process of the present invention for the preparation of a hydroxy-functionalized monoester from a tertiary alkyl acid comprises reacting a polyol with said tertiary alkyl acid in the presence of an acid catalyst selected from sulfonic acid derivatives, the reaction being carried out at a temperature below 180 ℃

Suitable polyols may be selected from ethylene glycol, propylene glycol, oligomers of glycols (n ═ 2-10), glycerol, neopentyl glycol, trimethylolpropane, pentaerythritol and combinations thereof. Preferred polyols are selected from the group consisting of ethylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol. Most preferred are neopentyl glycol and trimethylolpropane.

The acid derivative is selected from acids corresponding to general formula (I):

wherein R is¹、R²Each independently an aliphatic alkyl group of 1 to 10 carbon atoms, three groups (CH)₃+R¹+R¹) The total number of carbon atoms of (a) is 3 to 20, preferably 3 to 13.

The acidic catalyst is selected from sulfonic acid derivatives such as methanesulfonic acid, ethanesulfonic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid, and preferred acidic catalysts are methanesulfonic acid or p-toluenesulfonic acid. These acids are used in the range of 0.05 to 4 wt% relative to the weight of the acid and the polyol. The most preferred range is 0.10 to 2.5 wt% of the acid and polyol. The most preferred catalyst is methanesulfonic acid.

The hydroxy ester derived from the above polyol and the alkyl acid of formula (I) can be further used as a building block for the preparation of polyester resins with improved chemical resistance.

The resins thus obtained are oligomers which can be advantageously used in coating compositions, fiber impregnating compositions and lubricating oil compositions.

The invention also relates to coating formulations containing the cured compositions with the above resins.

The invention also relates to a shaped article comprising a cured composition having the above resin.

Test description and analytical methods:

and (3) impact test: ISO 6272-93(E)

Pendulum damping test (Koenig hardness):

according to ISO 1522-73(E) or DIN 53157

Summary of methyl ethyl ketone resistance (MEK) of the present process:

a piece of cotton soaked with MEK was rubbed over the coating (using a pressure of about 2 kg). The coating is said to be fully cured if the surface of the coating is wiped back and forth 100 times without showing any damage. If, after x "MEK double rubs", the coating has been damaged to produce a complete line running from the top to the bottom of the panel, the coating is said to fail after x "MEK double rubs". The MEK resistance is measured on the cured coating.

The viscosity of newtonian systems is measured using a Brookfield viscometer: ISO 2555-89.

The invention is illustrated in more detail by the following examples, without in any way limiting the scope of the application to these specific embodiments. All percentages are by weight of material and all parts are by weight of material, unless expressly stated otherwise.

Examples

The manufacturing procedure is as follows:

a1 liter round bottom glass reactor equipped with a stainless steel anchor stirrer, thermocouple, reflux condenser with Dean Stark and N₂An inlet. The reactor was charged with a tertiary alkyl acid and a polyol (see compositions in tables 1 and 2) in a 1: 1 acid/alcohol molar ratio. Reaction in N₂Under constant stirring and with gradual heating. At 130 ℃, the solvent (xylene) and the catalyst are added. Increasing the temperature until

150 ℃ when pivalic acid (V5) was used

170 ℃ when neodecanoic acid (V10) is used

(Versatic 10 acid available from Resolution Performance Products).

The temperature was kept constant until the acid value reached a constant value. At that time, the reaction was stopped and cooled.

For the example with Trimethylolpropane (TMP) as polyol, the following scheme indicates the structure of the product, which has been identified by GC-MS analysis (with ionization detection, mode POS-Cl). No polyether was found in the samples analyzed.

The catalyst used was:

p-toluenesulfonic acid (pTSA)

Methanesulfonic acid (70% aqueous solution of MSA)

The wt% reported for MSA in the table below is the weight of the solution provided.

pSTA is provided in solid form, 97.5%, from Acros

MSA is provided as a solution (70% in water) from Atofina

The polyols are used in the form provided:

trimethylolpropane (TMP) 97%, Aldrich

Neopentyl glycol (NPG) 99%, Aldrich

Pentaerythritol 98%, Aldrich

Examples of pivalic acid (V5)

TABLE 1

Nd is not done; yield based on converted acid

(amount of catalyst introduced: all are expressed in parts by weight based on the total weight of the acid and the polyol)

Example of Versatic10 acid (V10)

TABLE 2

Addition of 4 portions in the reaction

Example 12: preparation of polyester resin from ester-polyol prepared from example 6

A1 liter round bottom glass reactor equipped with a stainless steel anchor stirrer, thermocouple, reflux condenser and N was used₂An inlet. The product of example 6 (177.8 g) and succinic anhydride (153.6 g) were charged to the reactor in a 1: 1 molar ratio (taking into accountTo the desired monoester structure of the addition product). The mixture was heated to 105 ℃ with stirring, around which an exotherm occurred and the temperature rose up to 160 ℃. The reaction conditions were maintained until an acid value was reached. The reaction mixture was then cooled to about 140 ℃ and then Cardura E10(401 g) was added, the temperature being kept constant for 1 hour.

Properties of polyester resin:

color (Pt/Co): 130

Viscosity: 12690mPa.s

Coating formulation

A crosslinking agent: cymel 301 from CYTEC.

Curing catalyst: 40% butanol solution of pTSA, total viscosity of 1 wt% was used

The proportion is as follows: polyester 12/Cymel 80/20.

Curing conditions of the coated Q panel: 30 minutes at 140 ℃.

Applied layer: 60-65 microns.

Coating properties:

front/back impact strength > 160 inch pound

Slowly penetrate 9mm

MEK resistance > 100 double rubs

(MEK methyl ethyl ketone)

Examples 13 and 14: polyesters prepared from pivalic acid, polyols and other acids or anhydrides

Polyesters of the composition shown in table 3 were prepared in a glass reactor equipped with a stirrer, heater/cooler and Dean Stark. All components were heated to 160-200 ℃ until the desired acid number was obtained. The water of reaction was removed by azeotropic distillation with xylene.

Component (A)	13	14
			Pentaerythritol (mol)	2	2
Methylhexahydrophthalic anhydride (mol)	1	1
			V5(mol)	3	4
Catalyst and process for preparing same	MSA	MSA
			Amount of catalyst	0.02wt％	0.02wt％
OH value%	6.8	5.1
			Mw	892	909
Mn	722	745

(V5): new valeric acid

Example 15: polyester 14-based coating

Polyester 14 was then evaluated as a reactive diluent for isocyanate cured coatings. It was first blended with an acrylic polyol at 40 wt%. An aliphatic isocyanate Desmodur N3600 from Bayer was used as curing agent, the catalyst was a mixture of dibutyltin dilaurate and 1, 4-diazabicyclo [2, 2, 2] octane, and the system was diluted to 100mPas with butyl acetate.

This system is compared to a similar coating formulation prepared using the acrylic polyol without the polyester. The 40% content of the mixture has a much lower VOC (400 vs 458 g/l) than the control material, but still exhibits excellent setting speed and appearance. After less than 30 minutes at 60 ℃, the system is tack free.

Claims (5)

1. A process for preparing a hydroxy-functionalized monoester from a tertiary alkyl acid comprising reacting a polyol with the tertiary alkyl acid in the presence of an acid catalyst selected from the group consisting of sulfonic acid derivatives, the reaction being carried out at a temperature below 180 ℃, wherein the acid catalyst is selected from the group consisting of methanesulfonic acid, ethanesulfonic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid.

2. The process of claim 1 wherein the acid catalyst is methanesulfonic acid or p-toluenesulfonic acid.

3. The process of claim 1, wherein the acid catalyst is used in the range of 0.05 to 4 wt% relative to the weight of the acid and the polyol.

4. The process according to claim 1, characterized in that the tertiary alkyl acid is selected from acids corresponding to the general formula (I):

wherein R is¹、R²Each independently an aliphatic alkyl group of 1 to 10 carbon atoms, three groups CH₃+R¹+R²The total number of carbon atoms of (2) is 3 to 20.

5. The process of claim 1, characterized in that the polyol is selected from the group consisting of ethylene glycol, propylene glycol, oligomers of 2-10 n-of a diol, glycerol, neopentyl glycol, trimethylolpropane, pentaerythritol, and combinations thereof.