JP7746164B2 - Epoxy resin and its manufacturing method - Google Patents

Description

The present invention relates to an epoxy resin. More specifically, it relates to a tetramethylbisphenol F-type epoxy resin that is liquid at room temperature and has excellent handleability, and a method for producing the same.

When combined with various curing agents, epoxy resins offer excellent corrosion resistance, adhesion, chemical resistance, and flexibility, making them widely used in civil engineering and construction, adhesives, casting materials, and other applications. Bisphenol A liquid epoxy resins, in particular, undergo modification and polymerization reactions with various phenols, carboxylic acids, and other compounds, making them widely used as raw materials for heavy-duty anticorrosion paints, PCM paints, powder paints, and can paints.

In civil engineering, construction, and adhesive applications, epoxy resins must be liquid at room temperature due to their product form and usage. Furthermore, when modifying and polymerizing them into raw materials for heavy-duty anticorrosion paints, PCM paints, powder paints, and can paints, it is important that the raw material epoxy resin remains liquid during operations such as raw material storage, transportation, and preparation.
Epoxy resins, when combined with various curing agents, have excellent corrosion resistance, adhesion, chemical resistance, and flexibility, and are therefore widely used in civil engineering and construction, as adhesives, as raw materials for paints, etc. Bisphenol A liquid epoxy resins and bisphenol F liquid epoxy resins have traditionally been used in these fields, and currently no other liquid epoxy resins exist.
As an epoxy resin that remains liquid at room temperature, a composition using tetramethylbisphenol F and containing at least 85% of its n=0 isomer and n=1 isomer has been proposed, but it cannot be said that this has been sufficiently verified from the viewpoints of crystallinity, viscosity, impurities, etc. (Patent Document 1).

Special table 2018-536754 publication

The present invention provides a tetramethylbisphenol F type epoxy resin that has low crystallinity and remains liquid at room temperature.

The inventors discovered that an epoxy resin derived by reacting tetramethylbisphenol F containing a certain amount of polynuclear compounds with epichlorohydrin under specific conditions remains liquid at room temperature, leading to the present invention.

That is, the present invention provides a tetramethylbisphenol F epoxy resin characterized in that it contains, as measured by high performance liquid chromatography (HPLC), 0.1 to 2.5 area % of an epoxy resin (a) represented by the following formula (1), and, as measured by gel permeation chromatography (GPC), 75 to 85 area % of an epoxy resin (b) represented by the following formula (2) in which m=0, and is liquid at room temperature:

(where k is 2 or 3.)

(where m is the number of repetitions.)

The tetramethylbisphenol F epoxy resin of the present invention is obtained by reacting a starting phenol compound represented by the following formula (3) with epichlorohydrin in the presence of an alkali metal hydroxide, wherein the starting phenol compound contains 0.5 to 2.5 area % of components with n=2 or more as measured by GPC. The resulting tetramethylbisphenol F epoxy resin contains 75 to 85 area % of the m=0 form of the epoxy resin represented by the following formula (2), and is liquid at room temperature.

(where n is the number of repetitions, the average value of which is 1.005 to 3.)

(where m is the number of repetitions.)

The above-mentioned tetramethylbisphenol F type epoxy resin preferably has an epoxy equivalent weight of 200 to 220 g/eq., a hydrolyzable chlorine content of less than 5,000 ppm, an α-diol content of 1 to 20 meq./100 g, a phenolic hydroxyl group content of 1 to 20 meq./100 g, and a viscosity at 25°C of 50,000 to 200,000 mPa·s.

The present invention also provides a method for producing the above-mentioned tetramethylbisphenol F epoxy resin, which comprises reacting a phenol compound containing, in GPC measurement, 0.5 to 2.5 area % of a component represented by the following formula (3), n=2 or more, with 2.0 to 3.0 mol of epichlorohydrin per mol of phenolic hydroxyl groups in the compound, in the presence of 0.9 to 1.1 mol of an alkali metal hydroxide per mol of phenolic hydroxyl groups:

(where n is the number of repetitions, the average value of which is 1.005 to 3.)

The tetramethylbisphenol F type epoxy resin of the present invention does not form crystals for more than 100 days at room temperature, remains liquid, and is easy to handle.

The tetramethylbisphenol F type epoxy resin of the present invention is a mixture of a polynuclear epoxy resin (a) represented by the above formula (1) and a bifunctional epoxy resin (b) represented by the above formula (2). By containing specific amounts of the m=0 isomer of epoxy resin (a) and epoxy resin (b), the resin has the property of remaining liquid for more than 100 days at room temperature without forming crystals.

Epoxy resin (a) may be a variety of polynuclear compounds depending on the bonding position, but since very small amounts of the components are difficult to detect or separate, it is presumed that the main component is a mixture of three types of epoxy resins represented by the following formulas (1a) to (1c).

The content of the epoxy resin (a) is 0.1 to 2.5 area % as measured by HPLC, preferably 0.5 to 2.3 area %. If it is less than 0.1 area %, the crystallinity will increase regardless of the content of m=0 isomer in the epoxy resin (b), which is not preferred. If it exceeds 2.5 area %, the viscosity will increase, which is not preferred.
Since it is difficult to detect such epoxy resin (a) by GPC due to the relationship with other detected peaks, it is determined by HPLC measurement. The HPLC measurement conditions are the same as those described in the Examples.

The epoxy resin (b) has an m=0 isomer content of 75 to 85 area %, preferably 76 to 82 area %, as measured by GPC. If it is less than 75 area %, the viscosity will be high and handling at room temperature will be difficult. If it exceeds 85 area %, crystallinity may be significantly high even in the presence of epoxy resin (a). While there is no particular restriction on the content of m=1 or m=2, a content of 10 to 20 area % for m=1 and a content of 1 to 4 area % for m=2 are preferred. Too much m=1 or m=2 isomer undesirably increases the viscosity of the tetramethylbisphenol F epoxy resin of the present invention.

The tetramethylbisphenol F epoxy resin of the present invention can be obtained by reacting a specific amount of tetramethylbisphenol F with a specific amount of epichlorohydrin in the presence of a specific amount of alkali metal hydroxide. In this process, it is preferable to azeotropically evaporate the epichlorohydrin and water, return the epichlorohydrin to the system, and remove the water from the system.

The phenol compound represented by formula (3), which is a raw material for the tetramethylbisphenol F epoxy resin of the present invention, has a total content of n=2 or more components measured by GPC of 0.5 to 2.5 area %, preferably 0.55 to 2.2 area %, and more preferably 0.6 to 2.0 area %. When the epoxy resin is produced, an amount of epoxy resin (a) produced is small, resulting in high crystallinity, which is undesirable. An amount of epoxy resin (a) produced of 2.5 area % or more is too large, resulting in high viscosity, which is undesirable. Furthermore, the structure of the n=2 or more components is primarily a structure in which the glycidyl groups of the epoxy resins represented by formulas (1a) to (1c) are replaced with hydrogen atoms.
The GPC measurement conditions were the same as those described in the Examples.
Here, from the viewpoint of ensuring that the content of m=0 isomers in the epoxy resin (b) falls within a predetermined range, the raw material phenol compound preferably contains 96 to 99 area % of tetramethylbisphenol F represented by the following formula (3a) as measured by GPC. While possible isomers of the n=1 isomer in formula (3) include the p-p isomer, op-p isomer, and o-o isomer, the p-p isomer represented by formula (3a) below is the majority, and even if the op-p and o-o isomers are present, they are present in very small amounts and can be ignored. Furthermore, tetramethylbisphenol F contains various trace components as impurities. For example, these include structures formed by addition polymerization of the hydroxyl group of 2,6-xylenol with the para-position of another 2,6-xylenol. Therefore, it is preferable to remove these impurities by purification, but it is important to adjust the amount so as not to remove too many components with n=2 or more in formula (3).

The epoxy equivalent of the tetramethylbisphenol F epoxy resin of the present invention is preferably 200 to 220 g/eq., and more preferably 202 to 215 g/eq. If it is less than 200 g/eq., crystallinity may become high, and if it exceeds 220 g/eq., viscosity may become high.

Hydrolyzable chlorine is preferably less than 5,000 ppm, and more preferably 1,000 ppm or less. If it exceeds 5,000 ppm, reactivity with the curing agent may be reduced, and the physical properties of the resulting cured product may be reduced.

The α-diol content is preferably 1 to 20 meq./100g, and more preferably 3 to 12 meq./100g. If it is less than 1 meq./100g, crystallinity will be high, and if it exceeds 20 meq./100g, reactivity with the curing agent will be poor, and the physical properties of the resulting cured product may be reduced.

The phenolic hydroxyl group content is preferably 1 to 20 meq./100g, and more preferably 3 to 12 meq./100g. If it is less than 1 meq./100g, crystallinity will be high, and if it exceeds 20 meq./100g, reactivity with the curing agent will be poor, and the physical properties of the resulting cured product may be reduced.

The viscosity at 25°C is preferably 50,000 to 200,000 mPa·s, and more preferably 70,000 to 150,000 mPa·s. If it is less than 50,000 mPa·s, the crystallinity will be high, and if it is 200,000 mPa·s or more, handling at room temperature will be difficult, which is not preferable.

Next, we will explain the production method of the present invention. In the present invention, a starting phenol compound containing 0.5 to 2.5 area % of components of formula (3) with n=2 or more as measured by GPC is reacted with 2.0 to 3.0 moles of epichlorohydrin per mole of phenolic hydroxyl groups in the starting phenol compound, in the presence of 0.9 to 1.1 moles of alkali metal hydroxide per mole of phenolic hydroxyl groups.

If the amount of epichlorohydrin is less than 2.0 moles per mole of phenolic hydroxyl group, the content of m=0 in formula (2) above will be less than 75 area percent, which could increase the viscosity and epoxy equivalent of the resulting tetramethylbisphenol F epoxy resin and result in poor handleability at room temperature. Furthermore, if the amount of epichlorohydrin is more than 3.0 moles, the content of m=0 will exceed 85 area percent, which could result in high crystallinity even in the presence of epoxy resin (a).

If the amount of alkali metal hydroxide is less than 0.9 moles per mole of phenolic hydroxyl group, the α-diol content, hydrolyzable chlorine, and phenolic hydroxyl group content will be high, resulting in poor reactivity with the curing agent and the risk of poor physical properties for the resulting cured product. Furthermore, if the amount exceeds 1.1 moles, the α-diol, hydrolyzable chlorine, and phenolic hydroxyl group content will be low, resulting in the risk of high crystallinity. Usable alkali metal hydroxides include potassium hydroxide, sodium hydroxide, and lithium hydroxide. These alkali metal hydroxides may be used alone or in combination of two or more. These alkali metal hydroxides are typically used in the form of a 20-50% by weight aqueous solution.

It is also preferable to azeotropically evaporate epichlorohydrin and water in the presence of alkali metal hydroxide in the above molar ratio, return the epichlorohydrin to the system, and carry out the reaction while removing the produced water and the water carried in from the system.

In this reaction, epoxy resin (c) is also produced, in which components of the raw material phenol compound where n=2 or more react with epoxy resin (b). However, because the amount is so small, it is difficult to separate from epoxy resin (b). Therefore, in this invention, this epoxy resin (c) is also considered to be epoxy resin (b).

The present invention will be explained in detail using examples and comparative examples, but the present invention is not limited to these as long as it does not deviate from the gist of the invention. Unless otherwise specified, parts represent parts by weight and % represents % by weight. Analytical and measurement methods are described below.

Epoxy equivalent: Measured in accordance with JIS K 7236 standard, unit is g/eq.

Hydrolyzable chlorine: Measured in accordance with ASTM D-1726 standard, units are ppm converted to weight of chlorine atoms.

α-Diol content: After dissolving the sample in chloroform, an excess of benzyltrimethyl ammonium periodate solution was added and allowed to react. After that, 10% aqueous sulfuric acid solution and 20% aqueous potassium iodide solution were added, and the generated iodine was determined by potentiometric titration with 1/5 N sodium thiosulfate solution. The unit is meq./100g.

Phenolic hydroxyl group content: In a mixture of tetrahydrofuran and 4% methanol, tetramethylammonium hydroxide was reacted with the phenolic hydroxyl groups to develop color, and the absorbance at 305 nm was measured using a spectrophotometer. The phenolic hydroxyl group content was determined using a calibration curve previously prepared using the same procedure with tetramethylbisphenol F as the standard. The unit is meq./100g.

Viscosity: Viscosity was measured at 25°C using a Brookfield viscometer. Units are mPa·s.

The content of n=1 to n=3 units of tetramethylbisphenol F, which is the raw material phenol compound represented by the formula (3) above, and the content of m=0 unit of epoxy resin (b) represented by the formula (2) above are determined by GPC measurement, and the unit is area %. The GPC measurement conditions are as follows:
Apparatus: GPC-8220 system (manufactured by Tosoh Corporation)
Column: TSK-GEL (manufactured by Tosoh Corporation)
G2000H _XL x 2 + G1000H _XL
Temperature: 40℃
Eluent: tetrahydrofuran Flow rate: 1.0 mL/min Detector: RI
Sample concentration: 0.1 g/10 mL (tetrahydrofuran)
Sample injection volume: 25 μL

The content of the epoxy resin (a) represented by the above formula (1): determined by HPLC measurement, expressed in area %. The HPLC measurement conditions are as follows:
Equipment: HPLC 1200Series
(Agilent Technologies)
Column: Cadernza CD-C18
(Intakt, particle size 5 μm, inner diameter 4.6 mm, length 100 mm)
Temperature: 40℃
Eluent: (Solution A) distilled water, (Solution B) acetonitrile Gradient conditions: Time Solution A Solution B
0 minutes 40% 60%
5 minutes 40% 60%
20 minutes 0% 100%
30 minutes 0% 100%
Flow rate: 1.0 mL/min Detector: UV (245 nm)
Sample concentration: 0.05 g/10 mL (acetonitrile)
Sample injection volume: 10 μL

The tetramethylbisphenol F (TMBPF-1, TMBPF-2) used in the examples and comparative examples as the raw material phenol compound represented by the above formula (3) is as follows:
(TMBPF-1)
n=1 body: 97.5 area%, n=2 bodies: 0.94 area%, n=3 bodies: 1.2 area%.
(TMBPF-2)
n=1 body: 99.7 area%, n=2 bodies: 0.18 area%, n=3 bodies: 0 area%.

Example 1
A separable glass flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, a reflux condenser with an oil-water separator, and a pressure reducing device was charged with 128.0 parts of TMBPF-1 and 231.3 parts of epichlorohydrin (2.5 moles of epichlorohydrin per mole of phenolic hydroxyl groups in TMBPF-1), and the mixture was heated to 60°C with stirring under a nitrogen atmosphere. Next, while maintaining the temperature in the reaction system at 60°C, the pressure was gradually reduced to reflux the epichlorohydrin. 77.6 parts of a 49% aqueous sodium hydroxide solution (0.95 moles of sodium hydroxide per mole of phenolic hydroxyl groups in TMBPF-1) was continuously added dropwise over 150 minutes. During this time, the temperature was 60 to 65°C and the vacuum level was 100 to 140 mmHg, and the azeotrope of water and epichlorohydrin was separated into two layers using an oil-water separation tube. The lower epichlorohydrin layer was returned to the system, and the upper water layer was removed from the system. After the reaction, the vacuum level and temperature were gradually increased, and epichlorohydrin was distilled and removed until the final pressure reached 150°C and 5 mmHg. Thereafter, the reaction system was returned to atmospheric pressure, and 300 parts of toluene was added and dissolved, and 500 parts of water was added to separate and remove the by-product sodium chloride. Subsequently, washing was repeated with 300 parts of water until the wash water became neutral. This solution was heated to 150°C under a reduced pressure of 5 mmHg to remove the toluene, yielding a tetramethylbisphenol-type liquid epoxy resin. The resulting tetramethylbisphenol F liquid resin had an epoxy resin (a) content of 2.3 area %, an epoxy resin (b) content of m=0 of 78.2 area %, an epoxy equivalent of 208 g/eq., a viscosity of 98,000 mPa s, a hydrolyzable chlorine content of 210 ppm, an α-diol content of 9 meq./100 g, and a phenolic hydroxyl group content of 8 meq./100 g. This resin was allowed to stand at 25°C for 100 days, but no crystals were formed and it remained liquid.

Example 2
A tetramethylbisphenol F liquid resin was obtained using the same equipment as in Example 1, except that the raw materials were a mixture of 25.6 parts TMBPF-1 and 102.4 parts TMBPF-2. This raw material mixture had an n=1 unit: 99.23 area %, n=2 unit: 0.33 area %, and n=3 unit: 0.24 area %. The resulting tetramethylbisphenol F liquid resin had an epoxy resin (a) content of 0.60 area %, an epoxy resin (b) content of m=0: 78.0 area %, an epoxy equivalent of 205 g/eq., a viscosity of 98,000 mPa s, a hydrolyzable chlorine content of 300 ppm, an α-diol content of 9 meq./100 g, and a phenolic hydroxyl group content of 7 meq./100 g. This resin was allowed to stand at 25°C for 100 days, but no crystals formed and it remained liquid.

Example 3
The same operation as in Example 1 was carried out using the same apparatus as in Example 1, except that the charged amounts were 128.0 parts TMBPF-1 and 268.3 parts epichlorohydrin (2.9 moles of epichlorohydrin per mole of phenolic hydroxyl groups in TMBPF-1). The resulting tetramethylbisphenol F liquid resin had an epoxy resin (a) content of 2.3 area %, an epoxy resin (b) content of m=0 of 84.2 area %, an epoxy equivalent of 202 g/eq., a viscosity of 79,000 mPa s, a hydrolyzable chlorine content of 200 ppm, an α-diol content of 7 meq./100 g, and a phenolic hydroxyl group content of 7 meq./100 g. This resin was allowed to stand at 25°C for 100 days, but no crystals were formed and it remained liquid.

Comparative Example 1
A tetramethylbisphenol F liquid resin was obtained using the same apparatus as in Example 1, except that the raw material was TMBPF-2. The resulting tetramethylbisphenol F liquid resin had an m=0 form of epoxy resin (b) of 77.5 area %, an epoxy equivalent of 207 g/eq., a viscosity of 95,000 mPa s, a hydrolyzable chlorine content of 220 ppm, an α-diol content of 8 meq./100 g, and a phenolic hydroxyl group content of 8 meq./100 g. No epoxy resin (a) was detected. When this resin was allowed to stand at 25°C, crystals formed on the 23rd day.

Comparative Example 2
The same operation as in Example 1 was carried out using the same apparatus as in Example 1, except that the charged amounts were 128.0 parts of TMBPF-1 and 555.0 parts of epichlorohydrin (6.0 moles of epichlorohydrin per mole of phenolic hydroxyl groups in TMBPF-1). The resulting tetramethylbisphenol F liquid resin had an epoxy resin (a) content of 2.3 area %, an epoxy resin (b) with m=0 content of 88.8 area %, an epoxy equivalent of 200 g/eq., a viscosity of 72,000 mPa s, a hydrolyzable chlorine content of 200 ppm, an α-diol content of 6 meq./100 g, and a phenolic hydroxyl group content of 7 meq./100 g. When this resin was allowed to stand at 25°C, crystals formed on the 15th day.

Comparative Example 3
The same operation as in Example 1 was carried out using the same apparatus as in Example 1, except that the charged amounts were 128.0 parts of TMBPF-2 and 180.0 parts of epichlorohydrin (1.94 moles of epichlorohydrin per mole of phenolic hydroxyl groups in TMBPF-1). The resulting tetramethylbisphenol F liquid resin had an epoxy resin (a) content of 0 area %, an epoxy resin (b) content of m=0 of 73.2 area %, an epoxy equivalent of 219 g/eq., a viscosity of 187,000 mPa s, a hydrolyzable chlorine content of 50 ppm, an α-diol content of 8 meq./100 g, and a phenolic hydroxyl group content of 4 meq./100 g. When this resin was allowed to stand at 25°C, crystals formed on the 96th day.

The tetramethylbisphenol F epoxy resin of the present invention is useful for applications such as flooring materials and adhesives, particularly those used in outdoor environments. It is also useful as an industrial raw material, such as a raw material for paints.

Claims (4)

A tetramethylbisphenol F epoxy resin characterized in that it contains, as measured by high performance liquid chromatography, 0.1 to 2.5 area % of a mixture containing epoxy resins represented by the following formulas (1a) to (1c) as an epoxy resin represented by the following formula (1), and contains, as measured by gel permeation chromatography, 75 to 85 area % of an epoxy resin represented by the following formula (2) in which m=0, and has a viscosity at 25°C of 50,000 to 150,000 mPa s, is liquid at room temperature, and does not form crystals at 25°C for 100 days or more.
(where k is 2 or 3.)
(where m is the number of repetitions.)
A tetramethylbisphenol F epoxy resin obtained by reacting a phenolic compound represented by the following formula (3) with epichlorohydrin in the presence of an alkali metal hydroxide, the epoxy resin containing 0.1 to 2.5 area % of a mixture containing epoxy resins represented by the following formulas (1a) to (1c) as the epoxy resin represented by the following formula (1) as measured by high performance liquid chromatography, and containing 75 to 85 area % of an epoxy resin represented by the following formula (2) in which m=0 as measured by gel permeation chromatography, the epoxy resin having a viscosity of 50,000 to 150,000 mPa s at 25°C, being liquid at room temperature, and not forming crystals for 100 days or more at 25°C.
(Here, n is the number of repetitions, and its average value is 1.005 to 3. In gel permeation chromatography measurement, components with n=2 or more are contained in an amount of 0.5 to 2.5 area %.)
(where k is 2 or 3.)
(where m is the number of repetitions.)
The tetramethylbisphenol F epoxy resin according to claim 1 or 2, having an epoxy equivalent of 200 to 220 g/eq., a hydrolyzable chlorine content of less than 5,000 ppm, an α-diol content of 1 to 20 meq./100 g, a phenolic hydroxyl group content of 1 to 20 meq./100 g, and a viscosity at 25°C of 50,000 to 150,000 mPa·s. A method for producing the tetramethylbisphenol F type epoxy resin according to any one of claims 1 to 3 , comprising the steps of:
A method for producing a tetramethylbisphenol F epoxy resin, comprising reacting a phenolic compound containing, as measured by gel permeation chromatography, 0.5 to 2.5 area % of a component represented by the following formula (3), n=2 or more, with 2.0 to 3.0 moles of epichlorohydrin per mole of phenolic hydroxyl groups of the phenolic compound, in the presence of 0.9 to 1.1 moles of an alkali metal hydroxide per mole of phenolic hydroxyl groups of the phenolic compound:
(where n is the number of repetitions, the average value of which is 1.005 to 3.)