EP2486075A1

EP2486075A1 - Reducing impurities in solid epoxy resin

Info

Publication number: EP2486075A1
Application number: EP10766140A
Authority: EP
Inventors: Jane Neyer; Leming Gu; Bruce D. Hook; Philip J. Carlberg; Charles L. Menefee; Eric B. Ripplinger; David L. Burow; David R. Brooks; Thomas C. Young
Original assignee: Dow Global Technologies LLC
Current assignee: Dow Global Technologies LLC
Priority date: 2009-10-07
Filing date: 2010-10-05
Publication date: 2012-08-15
Also published as: KR20120093204A; BR112012007769A2; WO2011043803A1; CN102574981A; JP2013507482A; TW201134844A

Abstract

Methods of reducing impurities from a solid epoxy resin in a discrete particulate form. The methods include heating a heterogeneous mixture of the solid epoxy resin, while maintaining the solid epoxy resin in discrete particulate form, and a solution to a predetermined temperature below the solid epoxy resin's softening point temperature. Agitating the heterogeneous mixture at the predetermined temperature for a predetermined time to extract ionic species from the solid epoxy resin into the solution and separating the solid epoxy resin in discrete particulate form from the ionic species in solution. The separated solid epoxy resin having a reduced impurity content relative to the heterogeneous mixture prior to heating.

Description

REDUCING IMPURITIES IN SOLID EPOXY RESIN

[001] The present disclosure relates to methods for reducing impurities in a solid epoxy resin (SER), and in particular for reducing ionic species in SER in discrete particulate form.

[002] Epoxy is a thermosetting polymer formed from the reaction of an epoxy "resin" with a polyamine "hardener." Epoxy has a wide range of applications, including coatings, adhesives, fiber-reinforced plastic materials, composite materials, and electrical laminates. In general, epoxies are known for their adhesion, chemical and heat resistance, mechanical properties and electrical insulating properties.

[003] Commercially produced SER's have been prepared in a variety of ways, including the condensation of a bisphenol and epichlorohydrin in a water medium. Some drawbacks include additional steps needed to reduce impurities that were formed during the formation of the epoxy resin and to recover the epoxy resin after the impurity reduction. One previous method to reduce impurities includes repeating a high temperature water/steam wash. Another method involves completely dissolving the epoxy resin in an organic solvent, followed by a liquid-liquid extraction of impurities and further followed by solvent removal to separate the resin. The required high temperatures required to remove the solvent to sufficiently low levels, e.g. , 2500 parts per million (ppm), and the additional steps can be time-consuming and increase usage of energy and materials, which increases the cost of production.

[004] "Solid epoxy resin (SER)" refers to an epoxy resin whose physical form is in a solid state at ambient temperature within a range of from 23 degrees Celsius (°C) to 25 °C.

[005] "Discrete particulate form" refers to SER composed of distinct epoxy resin particulates, e.g. , a powder.

[006] "Softening point temperature" refers to the temperature at which a material is softened, such that the material yields under a definite stress, to flow or move a definite amount.

[007] The present disclosure provides methods for reducing impurities in

SER in discrete particulate form. Commonly assigned, co-pending PCT Application No.: PCT US09/547431 (PCT US09/547431), filed August 24, 2009, the entire content of which is incorporated herein by reference, provides methods of forming SER in discrete particulate form. PCT/US09/547431 reacts a bisphenol with a compound such as epichlorohydrin in the presence of aqueous caustic alkali and a dispersion promoting agent, e.g., cellulose ethers, to form the SER in discrete particulate form.

[008] The methods include heating a heterogeneous mixture including the

SER, while maintaining the SER in discrete particulate form, and a solution to a predetermined temperature below the SER's softemng point temperature, agitating the heterogeneous mixture at the predetermined temperature for a predetermined time to extract ionic species, e.g. , chloride ions (Cf), from the SER into the solution, and separating the SER in discrete particulate form from the ionic species in solution. The separated SER having a reduced impurity content relative to the heterogeneous mixture prior to heating.

[009] The discrete particulate form of the SER increases the interfacial surface area between the SER and the solution as compared to SER that is not in discrete particulate form. This allows ionic species to be extracted from the SER into the solution thereby reducing the overall ionic species concentration in the SER in discrete particulate form.

[010] The solution is selected from a water miscible solvent, water and combinations thereof. The water miscible solvent is selected from water miscible alcohols and water miscible ethers that maintain the SER in discrete particulate form when in the solution. The water miscible solvent can be employed within a range of from zero (0) volume percent (vol%) to 100 vol%, preferably within a range of from 0 vol% to 60 vol%, more preferably within a range of from 10 vol% to 50 vol% and still more preferably within a range of from 20 vol% to 40 vol%, the volume percent based on the total volume of the solution. The total volume of the solution can be expressed in a weight ratio of the SER in discrete particulate form to the solution and is within a range of from 1 : 1 to 1 :30, preferably within a range of from 1 :3 to 1 : 10 and more preferably within a range of from 1 :3 to 1 :5.

[01 1] Examples of water miscible alcohols include C_\ to C₆ alcohols and isomers. For example, methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2- butanol, t-butanol, 2-methyl-2-butuanol, 1-pentanol, 2-pentanoL 3-pentanol, 2- methyl-l-pentanol. 2-methyl-2-pentanol, 4-methyl-2-pentanol and mixtures thereof. Examples of water miscible ethers include 1 -methoxy-2-ethanol, l-ethoxy-2-ethanol, l-butoxy-2-ethanol, l-methoxy-2-propanol,. l-ethoxy-2-propanol, l-isobutoxy-2- propanol, 1 -phenoxy-2-propanol, l-methoxy-2-butanol, 3-methoxy-l-butanol, 2- methoxy-2-methylbutanol, ethylene glycol monoisopropyl ether, ethylene glycol monoisobutyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-tert- butyl ether and mixtures thereof. Examples of additional solvents that may be used are glycerin, propylene glycols, ethylene glycols, butylene glycols, polyethylene glycols, monomethoxypolyethylene glycols, ethylene oxides, propylene oxides, and combinations thereof. Additionally, the water miscible solvents can be mixed together in combinations that allow for the extraction of the ionic species, e.g., CI^", while maintaining the discrete particulate form of the SER.

[012] The solution may contain one or more additional substances that differ from water and the water miscible solvent. Examples of such substances include toluene, xylene, methylethyl ketone and methylisobutyl ketone. These substances can be employed within a range of from 0 vol% to 15 vol%, preferably within a range of from 0 vol°/o to 10 vol% and more preferably within a range of from 2 vol% to 8 vol%, the volume percent based on the total volume of the solution.

[013] The methods include adding the SER in discrete particulate form to the solution to form the heterogeneous mixture. During the agitating, the heterogeneous mixture is maintained at the predetermined temperature for a predetermined time. The predetermined time is within a range of from 5 minutes (min.) to 60 min., more preferably within a range of from 5 min. to 20 min. The predetermined temperature is within a range of from 20 °C to a temperature of 5 °C below the SER's softening point temperature. Maintaining the predetermined temperature maintains the integrity of the discrete particulate form of the SER. The methods are conducted at a pressure within a range of from 1 standard atmosphere (atm) (101.3 kilopascal) to 10 atm, preferably within a range of from 1 atm to 5 atm and more preferably within a range of from 1 atm to 2 atm. The agitating reduces the ionic species, e.g. , CI^", in the SER in discrete particulate form such that the concentration of CI^" in the SER is less than the concentration of CI^" in the solution.

[014] The mixer for agitating is selected from the type that gives sufficient mixing and heat transfer to extract the ionic species, e.g., CI^". Such mixers include reactors equipped with an overhung agitator, roto-stator mixers, high speed dispersers, colloid mills, static in-line mixers, and high shear in-line mixers. The range of agitation is within a range of from 10 revolutions per minute (rpm) to 20000 rpm, preferably within a range of from 500 rpm to 20000 rpm, more preferably within a range of from 1000 rpm to 10000 rpm and still more preferably within a range of from 1000 rpm to 6000 rpm.

[015] Separating the SER in discrete particulate form from the ionic species, e.g., CI^", in solution occurs by standard separation techniques such as centrifugation or filtration. The separated SER is in discrete particulate form and if desired undergoes drying. For example, the separated SER is dried in a vacuum at 20°C.

[016] The operating mode of the mixer can be either a batch process or a continuous process. For example, extracting the ionic species, e.g., CY, may be conducted in a continuous process where the heterogeneous mixture is continuously fed to the mixer for heating and agitating, recovered continuously from an exit stream of the mixer and dried continuously by suitable techniques, if desired. Likewise, the separation of the extracted SER particles and the drying of the extracted SER particles may be conducted in either a batch or continuous manner.

Example (Ex) 1

[017] The starting material for Ex 1 is the SER in discrete particulate form formed from the methods of PCT/US09/547431. The starting material has an initial CI^" concentration of 7400 ppm, a mean particulate size of 420 micrometers (um), and a softening point temperature of 102 °C.

[018] Combine 200 milliliters (ml) deionized water and 200 ml 2-propanol

(Cas# 67-63-0) in solution. Add 255 ml of the solution to a 3 neck round bottom flask equipped with Omni high shear rotor-stator type mixer (Model 17105, with a 35 mm diameter mixer head), a thermocouple and a heating mantle. Heat the solution to 60 °C while agitating at 500 rpm. Weigh 20 grams (g) of the SER in discrete particulate form in a beaker and add 45 ml of the solution to disperse the SER in a heterogeneous mixture. Pour the heterogeneous mixture into the flask. Wash the beaker with the 100 ml of the solution and add to the flask. Maintain the temperature of the heterogeneous mixture in the flask at 60 °C +/- 5 °C while agitating the heterogeneous mixture at 6000 rpm for 10 min. to extract the ionic species from the SER that remains in discrete particulate form. Empty the heterogeneous mixture into a beaker and separate the SER from the liquid by centrifugation. Dry the SER in a vacuum at 20°C. The dried SER. still in discrete particulate form, has a CI^" concentration of 508 ppm and a mean particulate size of 226 μηι.

Ex 2

[019] Repeat Ex 1, except use the dried SER in discrete particulate form from Ex 1 as the starting material. The dried SER in discrete particulate form resulting from the repeat of Ex 1 has a Ci^" concentration of 222 ppm and a mean particle^' size of 225 μπι.

Ex 3

[020] Repeat Ex 1 , except agitate the heterogeneous mixture at 600 rpm.

The dried SER in discrete particulate form resulting from the repeat of Ex 1 has a CI^" concentration of 1410 ppm and a mean particle size of 427 μηι.

Ex 4

[021] Repeat Ex 1, except use a starting material that is a SER in discrete particulate form having a CI^" concentration of 2400 ppm and a mean particulate size of 175 μηι. The dried SER in discrete particulate form resulting from the repeat of Ex 1 has a CI^" concentration of 63 ppm and a mean particle size of 306 μπι.

Test Methods

[022] Measure CI^" concentration according to ASTM D512-04 with a modification of dissolving the SER in toluene and performing a silver nitrate titration with methanol. Measure particulate size distribution with a Beckman Coulter dynamic image analyzer with RapidVue 2.006 software. Measure the softening point temperature according to ASTM D3104.

Claims

Claims What is claimed:

1. A method of reducing impurities in a solid epoxy resin in a discrete particulate form comprising, heating a heterogeneous mixture including the solid epoxy resin, while maintaining the solid epoxy resin in discrete particulate form, and a solution to a predetermined temperature below the solid epoxy resin's softening point

temperature, agitating the heterogeneous mixture at the predetermined temperature for a predetermined time to extract ionic species from the solid epoxy resin into the solution, and separating the solid epoxy resin in discrete particulate form from the ionic species in solution, the separated solid epoxy resin having a reduced impurity content relative to the heterogeneous mixture prior to heating.

2. The method of claim 1, including selecting the solution from a water miscible solvent, water and a combination thereof.

3. The method of any one of the preceding claims, including selecting the water miscible solvent from the group consisting of water miscible alcohols, water miscible ethers, and combinations thereof.

4. The method of any one of the preceding claims, where separating the solid epoxy resin in the discrete particulate form from the ionic species in solution includes filtering the solid epoxy resin from the ionic species in solution.

5. The method of any one of the preceding claims, where heating the

heterogeneous mixture of the solid epoxy resin in the discrete particulate form and the solution includes heating the heterogeneous mixture to the predetermined temperature within a range of from 20 °C to a temperature of 5 °C below the softening point temperature of the solid epoxy resin.

6. The method of any one of the preceding claims, including continuously feeding the heterogeneous mixture to a mixer for heating and agitating; and

continuously separating the solid epoxy resin in the discrete particulate form from the ionic species in solution.

7. The method of any one of the preceding claims, including maintaining the heterogeneous mixture at a pressure of one standard atmosphere to ten standard atmospheres during agitating.

8. The method of any one of the preceding claims, including maintaining a weight ratio of the solid epoxy resin to the solution within a range of from 1 :1 to 1 :30.