JPS621607B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides ε-
The present invention relates to a method for producing a modified epoxy resin having excellent flexibility obtained by ring-opening polymerization of caprolactone and having a primary hydroxyl group having excellent reactivity with a crosslinking agent. Epoxy resins, particularly glycidyl ether type epoxy resins produced from bisphenol A and epichlorohydrin, are available in various varieties ranging from liquid to high molecular weight solid resins, and are used for a variety of purposes. Low-molecular-weight liquids can be cured with polyamines and polyamide resins at room temperature by utilizing the reactivity of their epoxy groups, and used in adhesives, FRP, flooring materials, etc., and can be heated and cured with polybasic acid anhydrides. It is mainly used for electrical-related applications such as cast products. On the other hand, those with high molecular weight have a melting point of 60~
It is a brittle solid resin at 150°C, and has a secondary hydroxyl group in addition to a terminal epoxy group, so it is used in various coating fields that utilize the reaction of the hydroxyl group. For example, epoxy esters esterified with unsaturated fatty acids are used as air-drying or room-temperature-drying paints, as baking paints using melamine resin as a crosslinking agent, and in combination with phenolic resins for can coatings. It is also used in epoxy powder paints by turning it into powder and mixing it with blocked isocyanate. It is also used in cationic electrodeposition paints, etc. Despite being used for many purposes, it is hard, brittle, and has secondary hydroxyl groups.
Because of the grade, it has various disadvantages such as poor reactivity with crosslinking agents that react with hydroxyl groups, high temperature required for baking crosslinking, and poor weather resistance. The present inventors conducted extensive research to improve the drawbacks of epoxy resins and further expand the possibilities of epoxy resins. As a result, by ring-opening polymerization of ε-caprolactone to the secondary hydroxyl groups of epoxy resins, Appropriate flexibility is imparted to the hard and brittle epoxy resin, and at the same time, the less reactive secondary hydroxyl groups become the highly reactive primary hydroxyl groups of polycaprolactone, and moreover, the epoxy resin is bonded away from the rigid epoxy resin skeleton. The present invention was completed based on the discovery that the presence of primary hydroxyl groups facilitates the reaction with crosslinking agents. That is, the present invention relates to epoxy resins having hydroxyl groups.
Production of a lactone-modified epoxy resin characterized by reacting 97 to 5 parts by weight with 3 to 95 parts by weight of ε-caprolactone at 100 to 240°C to cause ring-opening polymerization of ε-caprolactone to the secondary hydroxyl group of the epoxy resin. Concerning the law. Conventionally, long-chain fatty acids have been esterified as a means of imparting flexibility to epoxy resins, but the hydroxyl groups that react with the crosslinking agent remain secondary, and , the number of hydroxyl groups decreases. In addition, the terminal epoxy groups of epoxy resins have been used to modify them with flexible polyester polyols, polycaprolactone polyols, and polyamide resins, but the hydroxyl groups used in the crosslinking reaction still have poor reactivity. It is a secondary hydroxyl group. Compared to those, the resin of the present invention not only further expands the uses of epoxy resin in that it simultaneously imparts flexibility and primary hydroxyl groups to the epoxy resin, but also has a faster curing reaction with a crosslinking agent than before. It is also useful for energy saving as it proceeds at low temperatures. The epoxy resin having a hydroxyl group used in the present invention is a diglycidyl ether manufactured from epichlorohydrin and bisphenol A and having the following structure. Or a diglycidyl ether prepared from epichlorohydrin and bisphenol F with the following structure: Alternatively, a diglycidyl ester synthesized from a polybasic acid and epichlorohydrin, etc. can be used. ε-caprolactone is produced industrially by oxidizing cyclohexanone with a peracid via the Bayer-Billiker reaction. In the present invention, ε
- Lactones or lactams other than caprolactone can also be copolymerized. The proportion of the epoxy resin in the lactone-modified epoxy resin of the present invention is 97 to 5 parts by weight, preferably 95 to 30 parts by weight out of a total of 100 parts by weight. The reason for this is that if the amount is too large, the desired sufficient flexibility cannot be obtained, and on the other hand, if the amount is too small, the resin becomes too soft. The ring-opening polymerization of ε-caprolactone to the secondary hydroxyl group of the epoxy resin is carried out at 100 to 240°C, preferably at 120°C.
Perform at ~200°C. If the temperature is lower than 100℃, the reaction rate will be low;
This is because if the temperature is higher than 240°C, ε-caprolactone will boil and escape out of the reaction system. It is preferable to use a catalyst for this reaction. Examples of catalysts include titanium compounds such as tetrabutyl titanate, tetrapropyl titanate, and tetraethyl titanate, organic tin compounds such as tin octylate, dibutyltin oxide, and dibutyltin laurate, and stannous chloride, stannous bromide, and stannous iodide. 1 tin or the like can be used. In particular, when it is desired to obtain a product with a narrow molecular weight distribution, it is preferable to use stannous chloride. The amount used varies depending on the reaction temperature, but generally starts from 1000ppm.
Use 0.01 ppm, preferably 500 ppm to 0.2 ppm. The reaction may be carried out without a solvent, or with toluene,
The reaction may be carried out in a solvent without active hydrogen such as xylene. However, solvents having ester bonds are generally not preferred. This is because, during the reaction, a transesterification reaction may occur with the ester group of polycaprolactone, resulting in the production of polycaprolactone that is not bonded to the epoxy resin. When tin chloride is used as a catalyst, it is also possible to use an ester solvent since it hardly promotes the transesterification reaction. However, when using a titanium-based catalyst, it is particularly desirable to avoid ester-based solvents because they also promote the transesterification reaction. The lactone-modified epoxy resin obtained in this way has a highly reactive primary hydroxyl group, so
It can be used as a crosslinked coating agent containing a crosslinking agent that reacts with hydroxyl groups, such as isocyanates, amino resins such as melamine, and phenolic resins. It can also be applied to powder coatings containing blocking isocyanates and the like. Furthermore, it can be added in part to applications where conventional epoxy resins are used to improve their flexibility and reactivity. Furthermore, by reacting the epoxy groups remaining at both ends of this resin with amines and further neutralizing with acid, it can also be applied to aqueous resins. By blending a melamine resin or blocking isocyanate as a water-soluble curing agent with such a water-based resin, it can be applied as a water-based baking paint or an electrodeposition paint. Furthermore, an epoxy acrylate resin is synthesized by reacting the epoxy groups at both ends of the resin of the present invention with acrylic acid or methacrylic acid, and by adding a radical initiator or a photosensitizer to this, a photocurable resin or a radical As a curable resin, it can be applied to FRP, photocurable paints, inks, adhesives, etc. The lactone-modified epoxy resin of the present invention will be explained below with reference to examples, but the present invention is not limited to these. In the examples, parts mean parts by weight. Example 1 Araldite 6097 (manufactured by Ciba, trade name of epoxy resin, melting point 130°C), 111 parts of ε-caprolactone, and tetrabutyl titanate were placed in a four-necked flask equipped with a nitrogen introduction tube, thermometer, cooling tube, and stirring device.
By charging 0.011 parts and reacting at 180℃ for 5 hours, a melting point of 81-85℃ and a hydroxyl value of 179KOHmg/
A solid resin having an epoxy equivalent of 3,070 g was obtained. Examples 2 to 5 Using the same apparatus as in Example 1, various epoxy resins were reacted with ε-caprolactone in various proportions to obtain lactone-modified epoxy resins. The results are shown in Table 1.

【table】

[Table] Application Examples 1 to 8 and Comparative Examples 1 to 2 After dissolving the lactone-modified epoxy resin obtained in Examples 1 to 5 and the epoxy resin not modified with ε-caprolactone in ethyl monoglycol acetate, various crosslinking agents were added. Mixed in a solid weight ratio of epoxy resin/crosslinking agent = 90/10, thickness 0.3mm
After applying it to a polished mild steel plate, it was dried and hardened. As a crosslinking agent (1) HMDI (hexamethylene diisocyanate)
Adduct Dyuranate 24A-100 (trade name) manufactured by Asahi Kasei Industries, Ltd. (2) XDI (xylene diisocyanate) Adduct Takenate D-110N (trade name) manufactured by Takeda Pharmaceutical Company Limited (3) IPDI (isophorone diisocyanate) trimer IPDI-T1890 (trade name) manufactured by Huls Chem (4) Isobutylated melamine Yuban 62 (trade name) manufactured by Mitsui Toatsu Chemical Co., Ltd. was used. The results are shown in Table 2. As is clear from Comparative Examples 1 and 2, only inflexible and brittle coating films were obtained from epoxy resins that were not modified with ε-caprolactone. However, as is clear from Application Examples 1 to 8, the resin modified with ε-caprolactone of the present invention provided a cured coating film with excellent flexibility, adhesion, and solvent resistance.

[Table] Example 6 100 parts of Araldite 6097 (trade name of epoxy resin manufactured by Ciba, melting point 130°C), ε was placed in a four-necked flask equipped with a nitrogen introduction tube, a thermometer, a cooling tube, and a stirring device.
- By charging 900 parts of caprolactone and 0.01 part of tetrabutyl titanate and reacting at 180°C for 5 hours, the melting point is 55-60°C and the hydroxyl value is 20.0KOH.
A lactone-modified epoxy resin with mg/g and epoxy equivalent of 18,000 was obtained. Application example 9 22.2 parts of this lactone-modified epoxy resin and 77.8 parts of Araldite 6097 were mixed and dissolved in ethylene glycol monoethyl ether acetate (EGA), and then a hexamethylene diisocyanate adduct (trade name of Asahi Kasei Corporation) was added as a crosslinking agent. Duranate 24A-100) was mixed at a ratio of NCO/OH = 1/1, applied to a polished mild steel plate with a thickness of 0.3 mm, and then dried and hardened at 120°C for 2 hours. The table below shows the results of coating film evaluation conducted in the same manner as in Application Example 1.
Shown in 3. Comparative Example 3 Coating was performed in the same manner as in Application Example 9 except that 100 parts of Araldite 6097 was used without using the lactone-modified epoxy resin, and the coating film was then evaluated and the results are shown in Table 1.
Shown in 3.

【table】

【table】

Claims (1)

[Claims] 1. 97 to 5 parts by weight of an epoxy resin having a hydroxyl group is reacted with 3 to 95 parts by weight of ε-caprolactone at 100 to 240°C to cause ring-opening polymerization of ε-caprolactone to the secondary hydroxyl group of the epoxy resin. A method for producing lactone-modified epoxy resin.