JPS6136853B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an epoxy resin curing agent, which aims to be easily mixed into liquid epoxy resin;
The object of the present invention is to provide a new liquid acid anhydride-based flexible curing agent that provides a flexible cured resin product and does not deteriorate the mechanical and electrical properties, heat resistance, thermal shock resistance, etc. of the cured product. be. Epoxy resins have traditionally been used in paints and other materials due to their excellent mechanical, electrical, and other properties.
It is widely used in various fields such as electricity and civil engineering, and with the expansion of its use in fields such as electrical parts in recent years,
There is a growing demand for even better properties such as heat resistance, adhesiveness, electrical insulation, and thermal shock resistance. However, as the epoxy resin curing agent commonly used for such uses, liquid acid anhydride-based agents such as phthalic anhydride, hexahydrophthalic anhydride, pyromellitic anhydride, etc. have been conventionally used. In this case, the resulting cured product becomes brittle and its impact strength and thermal shock resistance are reduced, which is a fatal flaw. Although this drawback can be overcome to some extent by adding a flexibility-imparting agent, the addition of the flexibility-imparting agent has the disadvantage of degrading the excellent mechanical and electrical properties inherent to the epoxy resin. Recently, polycarboxylic anhydrides obtained by condensing adipic acid, azelaic acid, sebacic acid, etc., have been known as hardening agents that impart flexibility.
However, all of these have high melting points of 50 to 80°C and are solid at room temperature, so it is impossible to mix them with normal liquid epoxy resins such as bisphenol A type and alicyclic epoxy resins at room temperature. In order to do this, heating is required, which has the disadvantage that the pot life is shortened and workability is extremely reduced. In view of the above-mentioned current situation, the present inventors developed a flexible cured product that is liquid at room temperature, has excellent workability, and can provide a cured product that has flexibility without inhibiting the inherent properties of epoxy resin. Various studies have been conducted with the aim of providing a drug. As a result, it has been found that the specific dibasic acids shown in A to D below, either singly or as a condensate of two or more, meet the above objectives. The present invention was completed based on this new knowledge. That is, the present invention provides formula A or expression A branched dibasic acid represented by the formula B or expression A dibasic acid represented by C general formula HOOC-(CH ₂ ) ₅ -A-(CH ₂ ) ₅ -COOH [where A is

【formula】

【formula】

[Formula] or ] An unsaturated branched dibasic acid or its hydrogenated product represented by the formula D C ₂₁ dicarboxylic acid represented by or formula The present invention relates to an epoxy resin curing agent characterized by containing a dehydrated condensate of one or more acids selected from the group consisting of C ₃₆ dimer acids represented by: The curing agent of the present invention has a melting point or crystallization temperature below 0°C, is liquid at room temperature, and can be easily mixed with liquid epoxy resin at room temperature without shortening its pot life. , has extremely high workability, provides good flexibility to the cured epoxy resin product, and can improve rather than reduce the inherent electrical properties, heat resistance, thermal shock resistance, etc. of the epoxy resin; In addition, it has all the characteristics required of this type of curing agent, and such a liquid acid anhydride-based flexible curing agent has not been known in the past. The dibasic acids shown in A) to D) above, which are used as monomer components in the curing agent of the present invention, are known or can be easily produced by known methods. For example A)
The branched dibasic acid having 12 carbon atoms shown in B) and the unsaturated branched dibasic acid shown in C) are formed by a ring-opening dimerization reaction of cyclohexanone with Fuenton's reagent and a subsequent hydrolysis reaction. The dibasic acid performs the ring-opening dimerization reaction of cyclohexanone,
It is obtained by adding 1 mol or 2 mol of styrene or the like to 2 mol of the above cyclohexanone in the presence of styrene, butadiene or isoprene. Further, the hydrogenated product of an unsaturated branched dibasic acid shown in C) can be obtained by subjecting the dibasic acid to a hydrogenation reaction according to a conventional method. Among the dibasic acids listed above, the dibasic acids A to C are particularly suitable for the present invention. The curing agent of the present invention is produced by subjecting one or more monomers shown in A) to D) above to a dehydration condensation reaction. This dehydration condensation reaction is carried out using a conventional dehydrating agent such as phosphorus pentoxide,
Phosphorus pentachloride, thionyl chloride, etc., sulfochloride,
This can be easily done using trichloromethyl, acetic anhydride, etc., and the desired acid anhydride can be produced by
Confirmed by infrared absorption spectrum analysis, etc.
According to the above dehydration condensation reaction, an oligomer in which several to several dozen raw material monomers are condensed is usually obtained, although it varies slightly depending on the conditions. As the curing agent of the present invention, any curing agent having one or more acid anhydride groups in its molecule, that is, a dimer or more of the raw material monomer, can be used in substantially the same manner. A particularly preferred curing agent is a mixed acid anhydride composed of two or more of the raw material monomers shown in A) to C) above. Examples thereof include oligomers of two types of branched dibasic acids shown in A), oligomers of two types of monomers shown in B), and two or more oligomers of each monomer contained in C). These oligomers also include, for example, oligomers of the corresponding linear dibasic acids that are slightly contained during the production and purification of the raw material monomers themselves, or oligomers of the linear dibasic acids and the above raw material monomers. It's okay to stay. The thus obtained curing agent of the present invention can exhibit the above-mentioned excellent properties as a liquid flexible curing agent, and these performances are superior to other acid anhydrides conventionally known as liquid curing agents. Even when used in combination with a curing agent, there is no significant decrease in flexibility, and in fact, this combination is desirable for applications that do not require much flexibility. Examples of the above-mentioned known liquid acid anhydride curing agents include dodecynylsuccinic anhydride and methylhexahydrophthalic anhydride. These amounts are usually up to 50% by weight, preferably 30% by weight of the total curing agent, within a range that does not impede the performance of the curing agent of the present invention.
It is recommended to use the following amounts. The epoxy resin to which the curing agent of the present invention can be applied is not particularly limited, and any of various resins such as the most widely used bisphenol A-based epoxy resin as well as alicyclic epoxy resins can be used.
Furthermore, the amount of the curing agent of the present invention added to the epoxy resin is not particularly limited and can be appropriately selected from a wide range. Normally, the amount of epoxy resin
It is desirable that the amount is about 80 to 300 parts by weight per 100 parts by weight. In particular, the curing agent of the present invention has the property of being easily compatible with the epoxy resin even at room temperature, and has the advantage that operations such as high-temperature heating are not required in the above-mentioned compounding. Furthermore, the epoxy resin blended with the curing agent of the present invention as described above has excellent stability that can be stored for more than one year at room temperature, which is approximately 140°C.
It hardens (gels) usually in about 3 to 5 hours by heating. Furthermore, even if it is a one-component type containing a normal curing accelerator, it can be stored stably at room temperature for about 2 months or more, which is usually about 10
It has the feature of curing (gelling) in ~50 minutes. Reference examples and examples are given below to explain the present invention in more detail. Reference Example 1 A mixture of two unsaturated branched dibasic acids represented by the following formula is used as a raw material monomer. The raw material monomers were heated and refluxed in acetic anhydride to undergo a dehydration condensation reaction to obtain a mixed acid anhydride. Infrared absorption spectrum (IR) of the obtained mixed acid anhydride
An analysis diagram is shown in Figure 1. From the figure, the product has acid anhydride groups at 1740 and 1840 cm ^-1

The characteristic absorption of [Formula] and the absorption of the terminal free acid group (-COOH) at 1705 cm ^-1 were observed, and it was identified as a mixed acid anhydride. Reference Examples 2 to 11 Using the raw material monomers shown in Table 1 below, a dehydration condensation reaction was carried out in the same manner as in Reference Example 1 to obtain acid anhydrides. As a result of IR analysis, each of the obtained acid anhydrides was identified by the fact that characteristic absorption of the acid anhydride group was observed at 1740 and 1840 cm ^-1 .

[Table] The properties of the acid anhydrides obtained in each of the above reference examples are shown in Table 2 below.

[Table] In terms of compatibility with epoxy resin, ◎ indicates a homogeneous solution form, 〇 indicates almost no turbidity, and △ indicates turbidity but 90~
Each shows that it becomes transparent at 100℃. The epoxy resins used above are as follows. "Epicote 828"...manufactured by Ciel Chemical Co., Ltd., bisphenol A-based liquid epoxy resin with an average molecular weight of 380 and an epoxy equivalent of 190. (formula

[Formula]) Example 1 Using the acid anhydride obtained in Reference Example 1 as a curing agent,
Add 150 parts of this to 100 parts by weight of "Epicote 828".
Parts by weight were added, and 1 part by weight of benzyldimethylamine was added as a curing accelerator. This product appeared as a homogeneous solution and was stable for 3 months at room temperature (25°C). The above formulation was then pre-cured at 140°C for 1 hour and then post-cured at 150°C for 20 hours to obtain a cured epoxy resin. The obtained cured product
Figure 2 shows an IR analysis diagram of the KBr tablet. The second
The figure shows that in the cured product, the absorption of acid anhydride groups (1840 and 1740 cm ^-1 ) of the acid anhydride used as a curing agent has disappeared, and the absorption of epoxy groups at 910 cm ^-1 (not shown) has also disappeared. On the other hand, the ester group (−COOR)
The absorption of OH appeared at 1740 cm ^-1 and the absorption of hydroxyl group (OH) appeared at 3420 cm ^-1 , and it is clear that the material was cured by reaction with the curing agent. Examples 2 to 18 Instead of the curing agent used in Example 1 above, each of the following curing agents (acid anhydride obtained in each reference example alone or a mixture of two or more, or this and a known liquid acid anhydride-based curing agent) The epoxy resin curing agent was obtained by curing the epoxy resin curing agent under the same conditions.

【table】

[Table] Examples 19 to 36 Using "Titsosox 221" as an epoxy resin, a predetermined amount of the curing agent of the present invention shown in Table 4 below was added to 100 parts by weight of the epoxy resin, and benzyldimethylamine was added as a curing accelerator. 1 part by weight of the above was gelled under the pre-curing conditions listed in Table 4 and post-curing at 150° C. for 20 hours to obtain a cured epoxy resin.

[Table] The results of measuring the physical properties (all at 20°C) of the cured epoxy resins obtained in each of the above Examples are shown in Table 5 below.

【table】

[Table] According to Table 5 above, according to the use of the curing agent of the present invention,
It is clear that a cured epoxy resin can be obtained which has excellent flexibility and mechanical properties as expressed by tensile strength and elongation, and also has good electrical properties.

[Brief explanation of the drawing]

FIG. 1 shows an IR analysis diagram of the curing agent of the present invention obtained in Reference Example 1, and FIG. 2 shows an IR analysis diagram of an epoxy resin cured using the curing agent.

Claims (1)

[Claims] 1 A formula or expression A branched dibasic acid represented by the formula B or expression A dibasic acid represented by C general formula HOOC-(CH ₂ ) ₅ -A-(CH ₂ ) ₅ -COOH [where A is [formula] [formula] [formula] or ] An unsaturated branched dibasic acid or its hydrogenated product represented by the formula D C ₂₁ dicarboxylic acid represented by or formula An epoxy resin curing agent characterized by containing a dehydrated condensate of one or more acids selected from the group consisting of C ₃₆ dimer acids represented by: 2. The curing agent according to claim 1, wherein the dehydration condensate is an anhydride or mixed acid anhydride of an acid selected from A to C above. 3. The curing agent according to claim 2, wherein the dehydrated condensate is a mixed acid anhydride of two or more acids selected from A to C above. 4. The curing agent according to claim 1, which contains dodecynylsuccinic anhydride and/or methylhexahydrophthalic anhydride together with the dehydration condensate. 5. The curing agent according to claim 1, which is used in an amount of 80 to 300 parts by weight per 100 parts by weight of the epoxy resin.