JPH05222158A - Epoxy resin and its production - Google Patents

Abstract

PURPOSE:To provide a bisphenol A epoxy resin which satisfies specific requirements and is useful for preparing a powder coating material giving a coating film excellent in toughness, flexibility, and impact strength. CONSTITUTION:100 pts.wt. liq. bisphenol A epoxy resin having a hydrolyzable Cl content of 0.1% or lower and an a-diol group content of 6 milliequivalents/100 g or lower is reacted with 30-50 pts.wt. bisphenol A to give a solid bisphenol A epoxy resin which has an epoxy equivalent of 500-1,300 and satisfies the relation of the expression [wherein w is an epoxy group content (equivalent/100g); is an alpha-diol group content (equivalent/100 g); y is a hydrolyzable Cl content (equivalent/100g) and z is a phenolic OH group content (equivalent/100 g)].

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an epoxy resin and a method for producing the same. More specifically, it relates to an epoxy resin effectively used for preparing an epoxy resin powder coating and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Powder coatings using a solid bisphenol A type epoxy resin are generally excellent in chemical resistance, adhesion, surface hardness, etc., but have the drawbacks of poor flexibility and impact resistance. Have In search of the cause of these defects,
As a result of various studies, the solid type bisphenol A type epoxy resin used for conventional powder coatings does not have epoxy groups at all of its terminal groups, and for example, α-diol group, hydrolyzable chlorine, phenol. It was found that the functional hydroxyl groups accounted for about 12 to 20% of the terminal functional groups.

That is, commercially available solid bisphenol A type epoxy resins are usually produced by a one-step method and a two-step method.

In the one-step method, a predetermined amount of bisphenol A and epichlorohydrin are reacted at once in the presence of an alkali such as sodium hydroxide to produce a high molecular weight product, in which the alkali is added to an aqueous solution. Since it is added in the form of, it is considered to have the following reaction mechanism, Therefore, epichlorohydrin is changed to glycidol,
It is considered that it reacts with the phenolic hydroxyl group (ph · OH) to form a diol.

On the other hand, in the two-step method, an excess amount of epichlorohydrin is used with respect to bisphenol A, which is reacted in the presence of an alkali to once produce a low molecular weight epoxy resin, which is further reacted with bisphenol A. To increase the molecular weight. In this case, since excess epichlorohydrin is present in the production of a low molecular weight epoxy resin, the proportion of glycidol is reduced, and the amount of terminal diol produced is reduced accordingly. A large amount of hydrolyzable chlorine remains, and even if bisphenol A is further reacted with such a product, hydrolyzable chlorine still remains in the following form in the high molecular weight product obtained. Further, the phenolic hydroxyl group remains unreacted, but its amount is smaller than that of hydrolyzable chlorine or diol.

Thus, the conventionally used solid bisphenol A type epoxy resin, whether it is a one-step process or a two-step process, is end-functionalized in any case. In addition to epoxy groups, it contains α-diol groups, hydrolyzable chlorine and phenolic hydroxyl groups.

[0007]

An object of the present invention is to provide a solid bisphenol A type epoxy resin having a small content of terminal functional groups other than epoxy groups, which is used for preparing a powder coating, An object of the present invention is to provide an epoxy resin capable of significantly improving the flexibility and impact resistance, which are the drawbacks found in conventional powder coatings, and a method for producing the same.

[0008]

The object of the present invention is as follows.
A solid type bisphenol A type epoxy resin having an epoxy equivalent of about 500 to 1300, which is achieved by an epoxy resin satisfying the following formula. [Other end functional group content] w: Epoxy group content (equivalent / 100g) x: α-diol group content (equivalent / 100g) y: Hydrolyzable chlorine content (equivalent / 100g) z: Phenolic Hydroxyl content (equivalent / 100g)

Such an epoxy resin contains 30 to 50 parts by weight of 100 parts by weight of a liquid bisphenol A type epoxy resin having a hydrolyzable chlorine content of less than 0.1% and an α-diol group content of not more than 6 meq / 100 g. Produced by reacting 1 part of bisphenol A.

The solid bisphenol A type epoxy resin according to the present invention is represented by the following general formula: It has an epoxy equivalent weight of about 500-1300, preferably about 600-1100. If the epoxy equivalent is smaller than this, it may no longer be a solid type, or even if it is a solid type, the blocking property is remarkable and it is not suitable for powder coating.
On the other hand, if an epoxy equivalent larger than this is used,
The melt viscosity becomes high, and the workability at the time of preparing the paint deteriorates.

The content of the other terminal functional group represented by the above formula must be within the range of 10% or less, preferably 5% or less. If the content of these other non-reactive terminal functional groups is higher than this, the crosslinking reaction at the terminal groups does not sufficiently occur and only a network structure similar to the uncured state grows, so increase the crosslinking density. Cannot be achieved, and eventually the desired modification effect cannot be obtained.

The production of such an epoxy resin having a low content of other terminal functional groups is carried out, for example, by having a hydrolyzable chlorine content of about 0.1 to 0.6% by weight and an epoxy equivalent of 180 to 25%.
Hydrolysis obtained by adding an alkali of less than 1 equivalent to 1 equivalent of the hydrolyzable chlorine to 0 liquid bisphenol A type epoxy resin and contacting them under a temperature condition of about 100 to 130 ° C. Liquid bisphenol A type epoxy resin having a chlorine content of less than 0.1% (Japanese Patent Laid-Open No. 59-43014)
(See Japanese Laid-Open Patent Publication No. 10), about 30 to 50 parts by weight of bisphenol A is added to 100 parts by weight of a phosphorus-based compound such as triphenylphosphine,
It is carried out by reacting in the presence of an alkali such as sodium hydroxide, potassium hydroxide and sodium carbonate, and an amine-based catalyst such as trialkylamine and tetraalkylammonium halide.

The liquid bisphenol A type epoxy resin having a hydrolyzable chlorine content of less than 0.1% used in this reaction has an α-diol group content (sample by the method described in JP-A-54-3900). After immersing the chloroform solution in 1 ° C in a water bath at 0 ° C, add ammonium benzyltrimethylperiodate solution, keep it in a 0 ° C water bath, and add 10% sulfuric acid.
(After adding 20% potassium iodide aqueous solution, titrate with 0.1N sodium thiosulfate standard solution and calculate from the difference from the blank)
However, as shown in Example 1 below, 6 meq or less / 100 g
Must be That is, even if the hydrolyzable chlorine content is less than 0.1%, as shown in Comparative Example 1 below, a solid bisphenol obtained from a liquid bisphenol A type epoxy resin having a higher α-diol group content than this. The A-type epoxy resin forms only a coating film inferior in flexibility and impact resistance when a powder coating material is prepared using it.

The solid type bisphenol A type epoxy resin produced in this manner has a small content of terminal functional groups other than the epoxy group of 10% or less, and should be effectively used for the preparation of epoxy resin powder coatings. You can

Preparation of a powder coating material using such an epoxy resin is carried out according to a usual method. That is, a curing agent, a filler, and other additives are mixed with a solid epoxy resin, and the mixture is sufficiently crushed and mixed with a mixer or the like,
Kneading is performed using a twin-screw extruder at about 80 to 120 ° C, a kneader such as two rolls, and then a particle size suitable for powder coating, for example, in the case of electrostatic coating, by a fine pulverizer. Grind to about 30-70μ.

As the curing agent, for example, dihydrazides of dicarboxylic acids such as dicyandiamide, adipic acid and sebacic acid, aromatic amines, acid anhydride adducts, crosslinkable resins such as polyester, polyacryl and polyphenol are generally used. The existing one is used as it is.
In addition, tris (dimethylaminomethyl) phenol, imidazoles, organic carboxylic acids and the like can be used to accelerate the curing. Further, as the additive, pigments such as talc, titanium oxide, silicon oxide and red iron oxide, and aerial, acrylic resin and butyral resin for improving the flowability and pinhole property of the paint are used.

The coating is carried out by dipping, fluidized dipping, for applications such as large-diameter, medium-diameter or small-diameter steel pipes, containers, automobiles, bicycles, other vehicles, and undercoating of household appliances.
It can be performed by a generally used method such as electrostatic coating.

[0018]

INDUSTRIAL APPLICABILITY The epoxy resin according to the present invention can be effectively used for the preparation of a powder coating, and the coating film formed from the powder coating prepared using this epoxy resin should be tough. It is flexible and has excellent impact resistance. That is, the flexibility and impact resistance, which are the drawbacks of the conventional powder coatings, are significantly improved.

The epoxy resin is preferably used not only for powder coatings but also as a resin component for solvent-based coatings, emulsion-based coatings, glass epoxy laminates, epoxy molding materials and the like.

[0020]

EXAMPLES The present invention will now be described with reference to examples.

Example 1 Low-hydrolyzable chlorine-containing liquid bisphenol A type epoxy resin produced by the method described in JP-A-59-43014 (epoxy equivalent 189 = 529 meq / 100 g, α-diol 6)
Milli-equivalent / 100 g, hydrolyzable chlorine 0.014 wt% = 0.4 meq / 100 g, phenolic hydroxyl group not detected) 100 parts (weight, the same below) and bisphenol A 33 parts were charged into a separable flask with a capacity of 500 ml, and the catalyst was further added. 0.02 part of triphenylphosphine was added.

These mixtures were heated with stirring under nitrogen and reacted at 150 ° C. for 7 hours. As a result, an epoxy resin having an epoxy equivalent of 600 and a viscosity (Gardner) of JK was obtained.

Example 2 In Example 1, 39.4 parts of bisphenol A was used.
As a result, an epoxy resin having an epoxy equivalent of 810 and a viscosity (Gardner) T was obtained.

Comparative Example 1 Bisphenol A type epoxy resin (epoxy equivalent 475 = 21
1 meq / 100 g, α-diol 20 meq / 100 g, hydrolyzable chlorine 0.005 wt% = 0.14 meq / 100 g, phenolic hydroxyl group not detected) 100 parts and bisphenol A 4.2 parts, separable with a capacity of 500 ml The flask was charged, and 0.02 part of triphenylphosphine was further added.

These mixtures were heated with stirring under nitrogen and reacted at 150 ° C. for 7 hours. As a result, an epoxy resin having an epoxy equivalent of 620 and a viscosity (Gardner) J was obtained.

Comparative Example 2 Shell Co. product Epicoat 1004 (epoxy equivalent 920, viscosity S), which is a typical bisphenol A type epoxy resin for powder coating, was used.

Reference Example A 100 parts of the epoxy resin prepared in Example 1 was mixed with 4 parts of a curing agent dicyandiamide, 50 parts of a filler rutile type titanium oxide and 1.2 parts of a flow control acrylic resin, and the mixture was ground. After crushing and mixing with a machine, the mixture was kneaded for 10 minutes with an 8-inch twin roll heated to 95 ° C. After cooling the kneaded product, it was ground with a hammer mill to prepare a powder having a particle size of 150 to 250 mesh as a main component with a standard sieve.

This powder coating was previously prepared using an electrostatic coating machine.
By coating on a 9 mm thick iron plate (SS-41, # 120 sander polishing) heated to 180 to 200 ° C, and further post-curing at 200 ° C for 10 minutes, a coating film with a thickness of about 300 to 350μ is obtained. Obtained.

With respect to the same kind of coating film, the following items were evaluated. Tensile strength: Electrostatic coating was applied to a plated iron plate for forming, baked, and then the film peeled from it was punched out from a tensile test dumbbell (JIS No. 2), and the tensile strength was measured according to JIS K-6911. Bending strength : A test piece (JIS K-6911; size 12.5 x 4mm) was prepared by compression molding method, and the bending strength was measured. Impact resistance: Using a DuPont impactor, a 2kg weight was shot at a 5 / 8-inch shot. Dropped

The obtained results are shown in Table 1 below,
The tensile strength, the bending strength and the impact resistance at low temperature are obviously higher than those of Reference Example C in which the epoxy resin having the content of other terminal functional groups calculated from the above formula of more than 10% is used. Excellent in points.

Reference Example B In Reference Example A, 9.7 parts of adipic dihydrazide was used as the curing agent instead of dicyandiamide, and the kneading temperature was changed to 100 ° C. and the post cure temperature was changed to 210 ° C.

The evaluation results of the obtained coating film are shown in Table 1 below, and are clearly superior to those of Reference Example D in the points of tensile strength, bending strength and impact resistance at low temperature. There is.

Reference Example C In Reference Example A, the epoxy resin prepared in Comparative Example 1 was used. The evaluation results of the obtained coating film are shown in Table 1 below.

Reference Example D In Reference Example B, the epoxy resin prepared in Comparative Example 1 was used. The evaluation results of the obtained coating film are shown in Table 1 below. (Below margin) Table 1 Reference example A Reference example B Reference example C Reference example D [Epoxy resin] Epoxy group (w) 167 167 161 161 161 α-diol group (x) 4.5 4.5 19.2 19.2 Hydrolyzable chlorine (y) 0.3 0.3 0.1 0.1 Phenolic hydroxyl group (z) 0.1 0.1 0.1 0.1 Content of other end functional group (%) 3 3 11 11 [Measurement item] Gel time (210 ℃) (sec) 140 95 148 119 Film tensile strength (kg / mm ² ) 5.4 4.8 4.0 3.5 Film elongation (%) 4.0 6.8 2.8 4.3 Bending strength of molded products (kg / mm ² ) 12.7 10.0 10.8 8.0 Bending modulus of molded products (kg / mm ² ) 548 430 460 410 Impact resistance (normal temperature) ) (cm)>50> 50 40> 50 Impact resistance (-40 ° C) (cm) 45 to 50 35 15 10

Reference Example E In Reference Example A, the epoxy resin produced in Example 2 was used, and the kneading conditions were changed to 115 ° C. for 8 minutes.

The evaluation results of the obtained coating film are shown in Table 2 below, and are more than those of Reference Example G using an epoxy resin having a content of other terminal functional groups of more than 10%. It is clearly superior in tensile strength, bending strength and impact resistance at low temperature.

Reference Example F In Reference Example B, the epoxy resin prepared in Example 2 was used, and the amount of adipic dihydrazide used was 7%.
Parts and kneading conditions were changed to 120 ° C and 8 minutes.

The evaluation results of the obtained coating film are shown in Table 2 below, and are clearly superior to those of Reference Example H in terms of tensile strength, bending strength and impact resistance at low temperature. There is.

Reference Example G In Reference Example E, the epoxy resin of Comparative Example 2 was used. The evaluation results of the obtained coating film are shown in Table 2 below.

Reference Example H In Reference Example F, the epoxy resin of Comparative Example 2 was used. The evaluation results of the obtained coating film are shown in Table 2 below. Table 2 Reference example E Reference example F Reference example G Reference example H [Epoxy resin] Epoxy group (w) 123 123 109 109 α-diol group (x) 4.3 4.3 18.5 18.5 Hydrolyzable chlorine (y) 0.3 0.3 0.1 0.1 Phenol Hydroxyl group (z) 0.1 0.1 0.5 0.5 Content of other end functional groups (%) 4 4 15 15 [Measurement item] Gel time (210 ℃) (sec) 115 90 125 100 Film tensile strength (kg / mm ² ) 5.3 4.5 4.7 3.8 Film elongation (%) 4.0 7.6 3.2 6.0 Bending strength (kg / mm ² ) 13.1 11.2 11.4 9.2 Bending modulus (kg / mm ² ) 632 535 508 452 Impact resistance (room temperature) (cm) >50>50>50> 50 Impact resistance (-40 ℃) (cm) 50 25 25 10

Claims (2)

[Claims] 1. A solid type bisphenol A type epoxy resin having an epoxy equivalent of about 500 to 1300, which satisfies the following formula. w: Epoxy group content (equivalent / 100g) x: α-diol group content (equivalent / 100g) y: Hydrolyzable chlorine content (equivalent / 100g) z: Phenolic hydroxyl group content (equivalent / 100g) 2. Hydrolyzable chlorine content of less than 0.1%, α-
Solid bisphenol A having an epoxy equivalent of 500 to 1300 characterized by reacting 30 to 50 parts by weight of bisphenol A with 100 parts by weight of a liquid bisphenol A type epoxy resin having a diol group content of 6 meq or less / 100 g. Type epoxy resin, the method for producing an epoxy resin satisfying the following formula. w: Epoxy group content (equivalent / 100g) x: α-diol group content (equivalent / 100g) y: Hydrolyzable chlorine content (equivalent / 100g) z: Phenolic hydroxyl group content (equivalent / 100g)