JPS6136774B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a flexible curable epoxy resin composition containing a novel liquid chloroprene polymer. Due to its excellent properties, epoxy resin is used in a wide range of fields such as cast products, impregnated materials, adhesives, sealants, and paints. There is a strong desire to improve, for example, impact resistance, adhesion to soft materials, and heat shock resistance. Furthermore, when a conventionally known liquid chloroprene polymer having carboxyl groups and epoxy groups is used as a flexibility imparting agent for epoxy resins, the flexibility is improved, but the curing reactivity, especially at temperatures below room temperature, is This has been considered a practical problem because the curing speed is delayed compared to the epoxy resin alone system. In view of these problems, the present inventor has developed a curing agent that can be mixed with ordinary epoxy resins in a wide range of blending ratios and that can be used as a curing agent for epoxy resins.
As a result of extensive research into a completely new flexibility agent that can be cured under curing conditions, it was discovered that the flexibility of epoxy resins can be significantly improved by using a specific liquid chloroprene polymer, and the present invention has been made. I was able to complete it. That is, one object of the present invention is to improve impact resistance, flexibility,
An object of the present invention is to provide a novel curable epoxy resin composition with improved heat shock resistance, peel adhesion, etc. Another object of the present invention is to provide a novel flexibility-imparting agent capable of accelerating the curing speed of epoxy resins. The object of the present invention is achieved by using the following liquid chloroprene polymer which has excellent compatibility with epoxy resins and can be easily co-cured with epoxy resins in the presence of a conventional curing agent for epoxy resins. The liquid chloroprene polymer used in the present invention has at least two hydroxyl groups in the molecule and has a number average molecular weight in the range of 500 to 10,000, and can be obtained according to the following manufacturing method. be. The hydroxyl group in the liquid chloroprene polymer is 2
If it is less than 1, the compatibility with the epoxy resin and co-curing properties tend to decrease, which is not preferable.
In addition, if the number average molecular weight of the liquid chloroprene polymer deviates from the above range, the curing reaction of the liquid chloroprene polymer by the epoxy resin curing agent may be slow, or the viscosity of the liquid chloroprene polymer may be too high. Blending with epoxy resins tends to be difficult. Next, the liquid chloroprene polymer used in the present invention has the general formula: (However, n=1 or 2, R has 2 or 3 carbon atoms
is a hydrocarbon group. ) in a solution system in the presence of an aliphatic mercapto alcohol. Aliphatic mercapto alcohols used here include, for example, 2-mercaptoethyl alcohol, 2-mercaptopropyl alcohol, 3-mercapto-1-propanol, and 3-mercapto-1,2-propanediol. Monomers that can be copolymerized with chloroprene include styrene, acrylonitrile,
Vinyl compounds such as acrylic acid, methacrylic acid, acrylic esters, methacrylic esters,
Examples include conjugated diene compounds such as 1,3-butadiene, isoprene, and 2,3-dichlorobutadiene-1,3. Organic solvents for producing the liquid polymer using a solution polymerization system include, but are not limited to, benzene, toluene, chloroform, carbon tetrachloride, tetrahydrofuran, dioxane, and methanol. Further, the epoxy resin used in the present invention is not particularly limited, but it is preferably one having an epoxy equivalent of about 100 to 1000 and being liquid at room temperature, and representative examples include bisphenol A type, alicyclic ester type, There are novolac types, all of which can be used. Further, as the epoxy resin curing agent used in the present invention, known ones may be appropriately selected. Diamine, 4,4'-diaminodiphenylmethane, m-
Aliphatic or aromatic polyamines such as phenylene diamine, 2,4,6-tris(dimethylaminomethyl)phenol, N-aminoethylpiperazine, polyamides such as condensation products of dimer acids and polyamines, and polymercaptans. , hexahydrophthalic anhydride, polycarboxylic acid anhydrides such as methylnadic anhydride, and BF ₃ -monoethylamine complex compounds. Further, in order to accelerate curing, it is also possible to use a known curing accelerator such as triethylenediamine, benzylmethylamine, and 2-ethyl-4-methylimidazole. The amount of the liquid chloroprene polymer used in preparing the curable epoxy resin composition with improved flexibility according to the present invention is limited to a range of 5 to 200 parts by weight per 100 parts by weight of the epoxy resin. If the cured product is outside this range, the flexibility of the cured product may not be substantially improved, or the flexibility may be excellent but the mechanical strength may be significantly reduced, resulting in practical problems. The composition of the present invention can be cured under the curing conditions of ordinary epoxy resins, and is generally treated at a temperature of room temperature to 200°C. Due to the effect of the hydroxyl group, the curing speed of the epoxy resin composition in which it is blended is greatly accelerated, so it is an epoxy composition that can be preferably used not only in high-temperature curing systems but also in low-temperature curing systems at room temperature or lower. can get. Of course, desired curing conditions and curing speed can be provided by selecting a combination of the type and amount of the curing agent and the type of the liquid chloroprene polymer. The composition according to the present invention can be used in a wide range of applications, from those that can be easily cured at room temperature to thermosetting compositions, depending on the selection of the curing agent, and can be used in adhesives, coating materials, lining materials, sealing materials, potting materials, and paints. It can be effectively used in the fields of coating film waterproofing materials, prepregs, cast products, etc. in the form of solvent-free compositions, solvent-type compositions, or aqueous emulsion compositions. Examples and comparative examples are shown below to further specifically explain the present invention. All amounts used herein are by weight. The liquid chloroprene polymer used in Examples and Comparative Examples was manufactured according to the following polymerization recipe example. Polymerization recipe example Monomer 100 parts 2-mercaptoethyl alcohol 2-7 parts Toluene 25-50 parts α・α′-Azobis-2・4-dimethylvalerontrile 0.25-0.75 parts Polymerization temperature 40-55°C Polymerization time 3-50 parts 20 hours Various polymers obtained using the above formulation are summarized in Table 1.

[Table] Example 1 (1) Compatibility test Using the epoxy resin "Epicote 828" manufactured by Ciel Co., Ltd., prepare a mixture of equal amounts of this and various liquid chloroprene polymers, and place this in a test tube at a temperature of 50°C. Table 2 shows the mixed state after being left for 7 days. As is clear from the results, when the liquid chloroprene polymer of the present invention was used, excellent compatibility was exhibited in all cases, but when Comparative Example Polymer D was used, clear phase separation was observed.

[Table] (2) Curing test A mixture of epoxy resin/liquid chloroprene polymer = 3/1 was made using polymers A, B, and C and the above epoxy resin, and the following curing agent for epoxy resin was mixed in varying amounts. Table 3 shows the results of examining the curing status after 1 day at 20°C. As a result, transparent to translucent cured products with improved flexibility were obtained in all cases.

[Table] Example 2 A compound obtained according to the following formulation was heated at 70℃ for 1 day.
Next, a cured product was prepared by curing at 150° C. for 2 hours, and the bending strength and flexibility were measured according to the test method of JISK6911. The results are shown in Table 4. Test Nos. 1 and 7 are comparative examples in which the liquid chloroprene polymer referred to in the present invention was not used. From these results, it is clear that the composition according to the present invention has a remarkable effect as a flexibility imparting agent for epoxy resins. Mixing prescription Epicote 828 100 parts Liquid polymer See Table 4 Tomide 235A 66 parts

【table】

[Table] Example 3 Table 5 shows the results of a DuPont falling ball test conducted to evaluate the impact resistance of the cured product according to the present invention. Test No. 11 is a comparative example in which the chloroprene liquid polymer was not included. From this result, it is clear that the cured product according to the present invention has excellent impact resistance.

【table】

[Table] Example 4 The aluminum/aluminum peel adhesion strength and the steel plate/steel plate shear adhesive strength were measured for a composition obtained using Polymer C according to the following formulation.
Test No. 12 here shows a comparative example using only epoxy resin. From these results, it is clear that the peel strength of the composition according to the present invention is greatly improved due to the flexibility improvement effect, and the shear strength does not decrease at all. Compounding recipe Epicote 828 100 parts Polymer C See Table 6 Tomide 235A 60 parts Curing conditions: 20℃ x 1 day, 150℃ x 1 hour cure

[Table] Example 5 A formulation obtained using Polymer C according to the following formulation.
A test piece for measuring heat distortion temperature was prepared by curing at 20℃ for 1 day and then at 150℃ for 1 hour.
The effect of adding the liquid chloroprene polymer was comparatively tested according to the method of ASTMD-648-72. As is clear from the results in Table 7, the addition of Polymer C significantly improved the heat distortion temperature. Exam here
No. 16 shows a comparative example in which Polymer C was not used. Mixing recipe Epicote 828 100 parts Polymer C See Table 7 Tetraethylenepentamine 11 parts

[Table] Example 6 A stainless steel washer ring (inner diameter 17 mmφ, outer diameter
27mmφ), and poured the mixture obtained from the following recipe into it and cured it at 70℃ x 2 hours, then at 150℃ x 2 hours, so that the embedded thickness of the wax shear ring was about 12
A plate-shaped cured product of mm was obtained. Regarding these,
After heating at +80°C for 30 minutes, a repeated heat cycle test was immediately conducted at -30°C for 30 minutes to evaluate the heat shot resistance. The results are shown in Table 8. Test No. 20 is a comparative example in which Polymer B was not used.

[Table] 〓○ mark: No clutch occurs〓
〓X: Clutch occurrence Example 7 In order to evaluate the curing speed of the composition according to the present invention, 5.
Table 9 shows the results of qualitatively determining the gelation time in thermostats at 20°C, 20°C, and 70°C. Test No. 23 is a comparative example using only epoxy resin.

【table】

【table】

Claims (1)

[Claims] 1. A chloroprene monomer alone or together with a monomer copolymerizable therewith and a hydroxyl group-containing polymerizable monomer represented by the following formula in the presence of an aliphatic mercapto alcohol in a solution system. The essential components are a liquid chloroprene polymer obtained by radical copolymerization in which the molecule has at least two hydroxyl groups and a number average molecular weight of 500 to 10,000, an epoxy resin, and an epoxy resin curing agent. A flexible epoxy resin composition comprising 5 to 200 parts by weight of the liquid chloroprene polymer per 100 parts by weight of the epoxy resin. formula (However, n is an integer of 1 or 2, and R is a hydrocarbon group having 2 or 3 carbon atoms.)