JPS58176211A - Curing of epoxy resin composition - Google Patents

Abstract

PURPOSE:To obtain a cured epoxy resin of good cracking resistance, by heating a composition containing an epoxy resin, a specified aliphatic diamine and a specified phenylenediamine in two stages under specified conditions. CONSTITUTION:1eq. of a liquid epoxy resin, MW<=1,000, is mixed with 0.2- 1.0eq. of an aliphatic diamine of the formula, wherein n>=4, and in which the distance between the primary amino groups is at least 1.25 times longer than the maximum molecular diameter of phenylenediamine, and 1.0-0.2 eq. of phenylenediamine so that the total amount of the both diamines added is 0.7-1.2 eq. and the resulting mixture is dried by heating at 60-120 deg.C for 20-100min and then heating at 120-160 deg.C for 60-250min.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical field to which the invention pertains The present invention relates to a method for curing an epoxy resin composition for obtaining a cured epoxy resin product with good crack resistance.

(2) Prior art and its problems Epoxy resins have excellent electrical properties, mechanical properties, and adhesive strength, so they are widely used as casting, molding, potting, sealing, and adhesive materials for electrical equipment and mechanical parts. ing. However, shrinkage caused by curing and exposure to a low-temperature environment generates internal stress, which tends to cause cracks in the cured resin itself and separation of the resin from the object to be embedded or adhered.

Conventional methods have been used to improve the crack resistance of epoxy resin compositions.

This is a method in which a flexibility imparting agent is added to the No. 1 K epoxy resin and cured to disperse internal stress. This method can lower the temperature at which cracks occur, but it is
There is a problem in that the glass transition point is lowered and the heat resistance of the cured product is deteriorated.

Second, by blending inorganic photonic agent powder with a small coefficient of thermal expansion such as silica and alumina into epoxy resin in a range of 50 to 90% by volume, it can be applied to objects to be embedded or bonded such as metals, ceramics, and glass. This method reduces internal stress and prevents cracks by reducing the difference in coefficient of thermal expansion between the resin composition and the resin composition. However, the fluidity of a resin composition containing 50 volumes or more of an inorganic photonic agent is significantly impaired, and as a result, casting, molding, and botting are difficult.
There are condyle points that make work such as sealing adhesive difficult.

(3) Purpose of the Invention The present invention provides crack resistance without lowering the glass transition point by adding the various flexibility-imparting agents mentioned above, or without reducing workability due to the addition of a large amount of inorganic brightening agents. The object of the present invention is to provide a method for producing a cured product using an excellent epoxy resin composition.

(4) Summary of the invention The present invention relates to an epoxy resin and an aliphatic diamine represented by the following formula. H, N-(-CH, 姶NH.

(However, n is an integer of 4 or more) and an epoxy resin composition consisting of phenylenediamine is heated at 60 to 120°C, and then heated to 120 to 160°C.
411FJ/C aliphatic diamine has a distance between primary amine groups that is 1.25 times or more the molecular diameter of phenylene diamine. It is characterized by

In addition, for 1 equivalent of epoxy resin, aliphatic diamine is added in an equivalent amount of 0.2 to 1.0 equivalent, and phenylene diamine is added in an equivalent amount of 1.0 to 0.2 in equivalent ratio of aliphatic diamine and phenylene diamine. The sum of the amounts added is equivalent ratio 0.7
This invention relates to a method of curing an epoxy resin composition added in an amount equivalent to 1.2.

In the present invention, since aliphatic diamine has a higher crosslinking reaction rate than phenylenediamine, the crosslinking reaction with the epoxy resin starts from aliphatic diamine at a curing temperature of 60 to 120°C. Participates in the crosslinking reaction of nine aliphatic diamines2
Since the distance between the two functional groups is larger than the longest molecular diameter of phenylenediamine, it is possible that the molecular movement necessary for the crosslinking reaction of the present phenylenediamine is possible after the crosslinking reaction of the aliphatic diamine is completed, and the phenylenediamine also continues. The crosslinking reaction can be completed. Here, the crosslinking reaction between phenylenediamine and epoxy resin is performed at a curing temperature of 120°C.
By controlling the temperature to 160 DEG C., a cured product with no uncrosslinked functional groups remaining, a uniform distribution of crosslinks, and excellent mechanical strength, particularly crack resistance, can be obtained. However, in the curing reaction of aliphatic diamine or phenylene diamine alone, as the crosslinking reaction progresses, the molecular movement of the curing agent necessary for the crosslinking reaction is restricted, leaving unreacted curing agent. It is difficult to obtain a uniform distribution of density, and there is a limit to mechanical strength.

Next, the present invention will be explained in detail.

The present invention provides an epoxy resin composition consisting of an epoxy resin, an aliphatic diamine, and a phenylene diamine with a concentration of 60 to 1
The first heating is performed at 20℃, and the curing temperature is 60℃.
In the following, the crosslinking reaction rate between the aliphatic diamine and the epoxy resin will be slow, and it will take time to complete the crosslinking reaction, which is unfavorable in terms of the manufacturing process. This is not preferable because it becomes impossible to obtain a uniform density distribution.

Moreover, when the first heating is 120° C. or higher, the crosslinking reaction rate between the aliphatic diamine and the epoxy resin increases, but the crosslinking reaction between the phenylene diamine and the epoxy resin is also promoted. Therefore, before the crosslinking reaction between the aliphatic diamine and the epoxy resin is completed, the crosslinking reaction between the phenylene diamine and the epoxy resin progresses, and since the aliphatic diamine has a large molecular diameter, its molecular movement is restricted and it remains as an unreacted curing agent. In other words, it becomes impossible to obtain a uniform distribution of crosslinking density, which is not preferable. Furthermore, the crosslinking reaction between aliphatic diamine and epoxy resin is completed within 100 minutes at a curing temperature of 60'0, and within 20 minutes at 120°C.
It is preferable to appropriately select the curing time within this range.

On the other hand, following the step of the first curing reaction,
Secondary heating is carried out at 60°C, but if the curing temperature is below 120°C, crosslinking of the aliphatic diamine and epoxy resin will cause
Since the molecular motion of phenylenediamine and the molecular motion of the epoxy resin are restricted, the rate of crosslinking reaction between phenylenediamine and ≠ boxy resin is slowed down, and it takes time for the crosslinking reaction to complete, which is unfavorable in the manufacturing process. Otherwise, unreacted phenylenediamine will remain, which is undesirable. Furthermore, if the secondary heating is set to 160"0 or more, the curing calorific value of the phenylenediamine and epoxy resin will increase, which will leave a large internal strain in the cured product, making it more likely to cause cracks, which is undesirable. , the crosslinking reaction between phenylenediamine and epoxy resin was completed within 250 minutes at a curing temperature of 120°C, and 16
Since curing is completed within 60 minutes at 0''O, it is preferable in terms of the manufacturing process to appropriately select the curing time within this range.

Next, materials that can be used in the present invention will be explained.

The epoxy resin used in the present invention is not particularly limited as long as it is a compound having two or more epoxy groups in one molecule. For example, glycidyl co-tyl type, glycidyl ester type, linear aliphatic epoxide type, alicyclic epoxide type,
Novolac type, heterocyclic epoxide type, etc. may be used alone or as a mixture. The molecular weight of the epoxy resin is not particularly limited, but it is preferably 1000 or less, which is liquid at working temperatures.

Further, the aliphatic diamine used in the present invention is expressed by the following formula.

H2N+CH8+-NH! (However, n is an integer of 4 or more) Diamine, for example 1
．． 4-diaminobutane (n = 4. Distance between functional groups = 6.2
5k), 1,5-diaminopentane (n = 5. Distance between functional groups = 7.52^), 1,6-diamithexane (n
=6. Distance between functional groups = 8.79^).

1.7-Diaminohebutane (n=7. Distance between functional groups=1
0.06A), 1.8-diaminooctay (n=9°, distance between functional groups=11.33^), 1.9-diaminooctay (n=9.distance between functional groups=12.60゜).

1.10-diaminodecane (n=to, distance between functional groups=
13.87&), 1,12-diaminododecane (n=1
2, distance between functional groups=16.41A), etc. It may also be a mixture of these.

Further, the phenylene diamine used in the present invention may be any of the isomers of orne-phenylene diamine, meta-phenylene diamine, and para-phenylene diamine, or may be a mixture thereof. The molecular diameters of orthophenylenediamine, metaphenylenediamine, and paraphenylenediamine are approximately 411 and 6.5, respectively.
& and 7.5 people.

The reason why the distance between the primary amine groups of aliphatic diamine is set to be 1.25 times larger than the maximum molecular diameter of phenylene diamine is because the distance between the primary amine groups of aliphatic diamine is 1.25 times larger than the maximum molecular diameter of phenylene diamine. This is because molecular movement is possible, and therefore, even after the crosslinking reaction by the primary amine group of the aliphatic diamine is completed, phenylenediamine can continue to proceed with the crosslinking reaction to complete it. If the distance between the primary amino groups of aliphatic diamine is within 1.25 times that of phenylene diamine, the curing reaction of aliphatic diamine will be completed, making it difficult for the molecular movement necessary for the curing reaction of phenylene diamine to occur, and This is because the crosslinking reaction of the diamine is not completed and unreacted phenylenediamine remains, and the presence of uncrosslinked portions of the epoxy resin does not improve mechanical strength, particularly crack resistance.

Therefore, if orthophenylenediamine is used as the second curing agent! may be combined with any aliphatic diamine where n is 4 or more, and when metaphenylenediamine is used as a second curing agent, it may be combined with any aliphatic diamine where n is 6 or more. , When paraphenylenediamine is used as the second curing agent, it may be combined with any aliphatic diamine in which n is 7 or more.

The equivalent ratio of aliphatic diamine to epoxy resin is 0.
．． It is desirable to blend the compound in an amount equivalent to 2 to 1.0, and if the equivalent ratio is less than 0.2, the crack resistance will be poor, and if the equivalent ratio is more than 1.0, the heat resistance will be poor.

In addition, the equivalent ratio of phenylenediamine to the epoxy resin is 0.7 to the sum of the equivalent ratio of the aliphatic diamine.
It is desirable to mix 1.0 to 0.2 equivalent to the 1.2 equivalent amount. If the stripe amount ratio is less than 02 equivalent, the heat resistance will be poor, and if the equivalent ratio is 1.0 or more, the crack resistance will be poor. become scarce.

(5) Effects of the Invention According to the present invention, it is possible to significantly improve the crack resistance of a cured epoxy resin product without reducing its heat resistance.

(6) Examples of the Invention The present invention will be explained below with reference to Examples. The heat distortion temperature of the cured resin product was measured by the method of A8TM D648-56. Furthermore, the fracture strength (P) of the cured resin product was measured using a high-slag autograph using the sample shown in the figure, and the fracture resistance value (K) was determined using the following formula. Here, t is the thickness of the sample, and tm is the thickness obtained by subtracting the depth of the groove that leads to fracture from the sample thickness + 1). ν is Poisson's ratio, W indicates the width of the sample, and K indicates the length of the moment of fracture stress. k is a constant. That is, in the sample measured this time, B t
n=2m+, t-4mm, W=60w, Wm
There are six values: =10m+, ν=0.35, and k=173.

Example 1 1.2-diaminoethane (functional intermetal distance = 3.7λ), 1,4-diaminobutane (functional intergroup distance = 6.3k), and 1,6-diamithexane (functional intermetal distance = 8) ,79k
) and 1,8-diaminooctane (distance between functional groups=11.
3k) and 1,12-diaminododecane (distance between functional groups =
ls, 4i) and orthophenylenediamine (molecular diameter = 4.8X) and metaphenylenediamine (molecular diameter =
6.5 people) and paraphenylenediamine (molecular size = 7.
51) is mixed with bisphenol diglycidyl ether type epoxy resin (Ebicor) 828. Table 1 shows the equivalent ratio to 1 equivalent of Shell epoxy equivalent (190). After each curing agent was dissolved in an epoxy resin with the composition shown in Table IK, a test piece having the shape shown in FIG. 1 was obtained under each curing condition. Comparing Examples A-D and Comparative Example A%C in Table 1, the distance between the amine functional groups of the aliphatic diamine is
Unless the molecular diameter of phenylenediamine is 1.25M or more, a good fracture resistance value is not exhibited. Moreover, Comparative Examples d-j are cases in which each curing agent is used alone, and are inferior to Examples A to D in both the fracture resistance value and the heat distortion temperature. Example 2 Bitzenol diglycidyl ether type epoxy resin (Epicote 828, manufactured by Shell Co., Ltd., epoxy equivalent: 19
Table 2 shows the equivalent ratio of 1,12-diaminododeca/ and metaphenylenediamine to 1 equivalent of 0). Polyethylene glycol as a flexibility imparting agent is expressed in parts by weight based on 100 parts by weight of the epoxy resin. Comparing Examples E-F and Comparative fi3 k-t in Table 2, the first heat curing temperature is 60 to 120°C, showing good fracture toughness values and heat distortion temperatures. Comparing Example G-H and Comparative Example m-”-n, the second heat curing temperature is 12
It is clear that it shows good fracture toughness values and heat distortion temperatures between 0 and 160°C. Comparing Examples I-J and Comparative Examples 0 to r, the amount of 1.12-cyamidodecantomephenylenediamine added was 0.2 to 1.0 in equivalent ratio.
It is clear that a good fracture toughness value and heat distortion temperature are exhibited when the amount of curing agent is equivalent to 1.0 to 0.2, and the sum of the amounts of curing agent added is 0.7 to 1.2 equivalent. be. Comparative Example S#i Although a flexibility imparting agent was added, it is clear that the heat resistance is lower than that of Examples E-J.

[Brief explanation of drawings]

Tip I shows the shape of the sample whose fracture strength value is to be measured according to the invention. 1 to 4...Stress 5...Sample l Kuteka mortar

Claims (5)

[Claims] (1) Epoxy resin and aliphatic diamine 1N4CH,iNH represented by the following formula. (However, n is an integer of 4 or more) and phenylenediamine.
After the first heating at 0 to 120℃, the second heating at 120 to 160℃
A method for curing an epoxy resin composition, which comprises heating as follows. (2) The method according to claim 1, which includes the addition of an aliphatic diamine characterized in that the distance between primary amino groups is 1.25 times or more the molecular diameter of phenylene diamine. A method of curing an epoxy resin composition. (3) A method for curing an epoxy resin composition according to claim 1, which comprises adding an aliphatic diamine at an equivalent ratio of 0.2 to 1.0 to one weight of epoxy resin. (4) A method for curing an epoxy resin composition according to claim 1, which comprises adding phenylenediamine in an equivalent amount of 1.0 to 0.2 equivalent to 1 equivalent of epoxy resin. (5) The sum of the amounts of aliphatic diamine and phenylene diamine added to 1 equivalent of epoxy resin has an equivalent ratio of 0°7 to 1.
．． 2. A method for curing an epoxy resin composition according to claim 1, wherein the amount is equivalent to 2.