JPH0153968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to microwave curable unsaturated polyester resin compositions.

Usually, the curing reaction of thermosetting resins such as unsaturated polyester resins involves thermosetting by heating. This method involves putting an uncured resin composition into a furnace heated to 100-150°C and curing it, and is widely used as a method for curing thermosetting resins such as unsaturated polyester resins. .

Although curing the resin by external heating is an easy method, it has the following drawbacks.
In other words, since the heating furnace must be constantly heated, there is a lot of waste in energy consumption. In other words, since it takes a considerable amount of time to raise the temperature of the furnace, the furnace must be constantly heated, and it is difficult to use the furnace in a timely manner because the power is turned off. In addition, if the resin to be cured is in contact with a metal with a large heat capacity, most of the heat will be absorbed by the metal with a large heat capacity even if it is put into the furnace, so it will have to be heated more than necessary. , which goes against energy conservation.

In order to solve the above-mentioned drawbacks, an internal heating method using microwaves based on the molecular motion of the resin is a convenient heating means. Microwave curing is an internal heating method, and it has long been known that it heats the resin part efficiently, but in order to cure it efficiently in a short time, it is necessary to have a resin composition suitable for microwave heating. be.

Unsaturated polyester resin, which is a commonly used thermosetting resin, is a resin containing a prepolymer obtained by polycondensation reaction of glycol, unsaturated polybasic acid, and saturated polybasic acid, and a polymerizable vinyl monomer. A peroxide is added to the composition as a polymerization initiator, and a polymerization reaction and a crosslinking reaction are performed by heating to form a three-dimensional structure. Conventional unsaturated polyester resin compositions mainly composed of styrene monomer and unsaturated polyester prepolymer have the disadvantage that they do not have the heating effect of microwaves, and microwave heating cannot be used to cure the resin. Ta.

This invention was made in order to eliminate the drawbacks of the conventional products as described above, and by using a polymerizable monomer containing diallyl phthalate and an unsaturated polyester prepolymer as the composition components, heating with microwaves is possible. The object of this invention is to provide a microwave-curable resin composition that can be cured in a short time.

The unsaturated polyester resin composition in the present invention contains as constituent components an unsaturated polyester prepolymer obtained by polycondensation reaction of a glycol, an unsaturated polybasic acid, and a saturated polybasic acid, and a polymerizable vinyl monomer.

Examples of unsaturated polybasic acids include maleic anhydride, fumaric acid, citraconic acid, and itaconic acid. Examples of saturated polybasic acids include tetrachlorophthalic anhydride, hedic acid, tetrabromophthalic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, endomethylenetetrahydrophthalic anhydride,
Tetrahydrophthalic anhydride, hexahydrophthalic anhydride, succinic acid, adipic acid, azelaic acid,
Examples include sebacic acid.

Examples of glycol include ethylene glycol, propylene glycol, butanediol 1,4, butanediol 1,3, butanediol 2,3, diethylene glycol, dipropylene glycol, triethylene glycol, pentanediol 1,5, hexanediol 1, , 6, neopentyl glycol, 2,2,4 trimethylpentanediol-1,3, hydrogenated bisphenol A, 2,2-di(4-hydroxypropoxyphenyl)propane, pentaerythritol diallyl ether, glycerin, trimethylene Examples include glycol, 2-ethyl-1,3-hexanediol, phenyl glycidyl ether, and allyl glycidyl ether.

These polybasic acids and glycols are appropriately combined, the amount of glycol is slightly excessive (approximately 10% more glycol), and a polycondensation reaction is performed at 150 to 200℃ to synthesize a prepolymer with an acid value of 50 or less. be done.

Styrene monomer is normally used as the polymerizable vinyl monomer, but in the present invention, diallylphthalate is added to enable polymerization reaction by microwave irradiation. As the polymerizable vinyl monomer, one containing styrene and diallyl phthalate is used. In this case, the proportion of diallyl phthalate in the total polymerizable monomers is 15 to 90%, preferably 25 to 80%.

The unsaturated polyester resin composition of the present invention contains the prepolymer and these polymerizable monomers, and the composition ratio of the polymerizable monomers is 30 to 30.
It is 80%. The amount of the polymerizable monomer added varies depending on the concentration of unsaturated groups in the prepolymer and the viscosity used. Such a resin composition is prepared by adding an organic peroxide catalyst such as benzoyl peroxide as a polymerization initiator, and heating it by irradiating it with microwaves (generally,
100-150℃). When diallylphthalate and styrene are used together as polymerizable monomers, it is desirable to use multiple types of polymerization initiators with different half-lives.

Microwaves are electromagnetic waves that occupy a range between radio waves and infrared waves, and have a frequency of 300MHz to 300GHz.
The wavelength is 1 to ^{10 -3} m, but the frequency band that can be used industrially is regulated by the Radio Law, and is 2453 to 10 -3 m.
A frequency of 2454MHz can be used. When a resin composition containing a polymerization initiator is placed in such a microwave heating curing furnace and heated, the resin composition is efficiently heated and cured in a short time (several minutes).
Since diallylphthalate-based unsaturated polyester is rapidly heated by microwave irradiation, bumping or foaming may occur, in which case,
Intermittent microwave irradiation is required.

Figure 1 shows diallylphthalate monomer, styrene monomer, unsaturated polyester prepolymer (from Example 2 described below), and water.
This is a curve diagram showing the relationship between microwave irradiation time and temperature rise, showing the experimental results of heating in a 2453MHz household microwave oven.From this result, styrene hardly rises in temperature, but diallylphthalate irradiates with microwaves for 10 seconds. The temperature rises to 110-120°C just by heating, and a significant microwave irradiation effect is observed. Therefore, when the unsaturated polyester composition contains diallyl phthalate, the temperature of the unsaturated polyester rapidly rises due to the remarkable heating effect of microwave irradiation, and the polymerization reaction due to heating proceeds. As described above, since the unsaturated polyester composition is heated in a short time by adding the diallyl phthalate monomer, it can be effectively cured by microwave heating.

However, since diallyl phthalate has a slower polymerization rate than styrene, it is necessary to raise the curing temperature to achieve the same curing conditions as styrene, which reduces the advantage of the fast temperature rise speed that can be achieved by adding diallyl phthalate. You end up doing it. On the other hand, the curing rate of unsaturated polyesters can be adjusted by increasing or decreasing the amount of peroxide, which is a polymerization initiator. Since diallyl phthalate is polymerized at a relatively high temperature, those with a long half-life are used, and dicumyl peroxide is generally used. For reference, benzoyl peroxide has a half-life of 100 hours at 53°C, while dicumyl peroxide has a half-life of 100 hours at 100°C. Unsaturated polyester using diallyl phthalate has excellent storage stability because of its long gelation time, but its curing time is longer than that of styrene, and it cannot be rapidly cured in a short period of time. For this reason, systems containing diallyl phthalate alone cannot take full advantage of the characteristics of microwave heat curing.

Therefore, by mixing appropriate amounts of diallyl phthalate and styrene and using two types of initiators with different half-lives, the product becomes optimal for microwave heating curing. When only diallyl phthalate is used, the gelation time is long, but when 20% or more of styrene is added, the gelation time is not much different from the case of styrene alone. In an unsaturated polyester composition, if the proportion of diallyl phthalate is high, the heating effect due to microwave irradiation will be greater, but the gelation time will be longer, so it is necessary to find an appropriate amount. Second
The figure shows the addition of diallylphthalate and styrene in various proportions to an unsaturated polyester prepolymer.
FIG. 2 is a relationship diagram showing the results of measurements for each gelation time and heating temperature. The results show that when the proportion of diallyl phthalate is high, the temperature rises in a short time, but the gelation time becomes longer. The composition is 15-90% diallyl phthalate;
It turns out that preferably a proportion of 25 to 80% is suitable.

The glass transition temperature of the cured product obtained by adding diallyl phthalate increases by about 20°C compared to the case of only styrene. Although the cost of diallyl phthalate is somewhat higher than that of styrene, the properties of the resulting cured product are quite excellent in thermal and mechanical properties, so it is sufficiently practical.

In the above description, any combination of prepolymers can be used by selecting the respective constituent units. Furthermore, the polymerization initiator is not limited to those mentioned above.

As described above, according to the present invention, since the composition is composed of a polymerizable monomer and a prepolymer containing styrene and diallyl phthalate, the rate of heating by microwave heating is considerably faster than that of conventional unsaturated polyester resin. heated with
Therefore, the curing reaction can be completed in a short time. As a result, even if the resin part is in contact with a metal etc. with a large heat capacity, the resin part is heated quite efficiently. It is not consumed in parts.
Additionally, in the case of microwave heating, in order to harden the resin, just turn on the microwave heating power each time, and the temperature of the resin will rise in a short time, so there is no need to constantly heat it like in a conventional heating oven. There are effects such as

Next, examples of the present invention will be described.

Example 1 While stirring 441 g of maleic anhydride, 75 g of succinic anhydride, 111 g of phthalic anhydride, 251 g of propylene glycol, 102 g of ethylene glycol, and 175 g of diethylene glycol in a four-necked flask,
React at around 120°C, reflux until a large amount of water is produced, continue the reaction at 150°C to 180°C for 2 to 3 hours while removing the water produced from the reaction system, and further until around the specified amount of dehydration. The reaction was carried out to obtain an unsaturated polyester prepolymer with an acid value of 35. At the end of the reaction, add 0.1% hydroquinone, and when the temperature of the reactant falls below 80℃, the styrene monomer
130 g of diallyl phthalate monomer and 500 g of diallyl phthalate monomer were added and stirred thoroughly to obtain an unsaturated polyester resin composition with a solid content of 60%.

As a polymerization initiator, 0.5 parts of benzoyl peroxide per 100 parts of unsaturated polyester prepolymer.
1 part and 0.5 part of dicumyl peroxide were added, the resulting unsaturated polyester resin composition was applied to a glass plate, and this was placed in a 5 kW, 2450 MHz microwave heating furnace and treated for about 15 minutes. Thus, a cured product of unsaturated polyester prepolymer was obtained. The general properties of the obtained cured product are a volume resistivity of 8.7×10 ¹⁵ Ω-cm and a dielectric breakdown strength of 4.5 kV/0.1.
mm, and the tensile strength was 6.8 Kg/ ^mm2 . These values are
It was found that the value almost coincided with that obtained by heating at 135°C for 3 hours.

Example 2 Trimellitic anhydride in a 4-necked flask
Add 192g, monoethanolamine 122g, neopentyl glycol 416g, and ethylene glycol 248g, heat to 160-170℃ with stirring, further add 760g of tetrahydrophthalic anhydride, raise the temperature to 190℃ while dehydrating, and then Continue the reaction by adding 392g of maleic anhydride to bring the acid value to 110-120.
And so. Next, cool to 120℃ and add hydroquinone.
Add 0.6g and 1500g of bisphenol type epoxy resin (Epon828) and proceed with the reaction at 120℃.
When the acid value reaches a value of 25, hydroquinone
By adding 0.3 g, 1200 g of diallyl phthalate, and 600 g of styrene, an unsaturated polyester resin assembly with a solid content of 65% was obtained.

To 100 parts of the unsaturated polyester prepolymer of the obtained composition, 0.3 parts of benzoyl peroxide and 0.7 parts of dicumyl peroxide were added as initiators, and this was applied to a glass plate, and the mixture was heated at 5 kW.
A cured product was obtained by putting it into a 2450MHz microwave heating furnace and treating it for about 20 minutes. The general characteristics of the obtained cured product are a volume resistivity of 7.1×10 ¹⁵ Ω.
−cm, dielectric breakdown strength 9.9kV/0.1mm, tensile strength
It was found that the value was 7.3 Kg/mm ² , which was almost the same value as that obtained by heating at 155° C. for 6 hours.

[Brief explanation of drawings]

Figure 1 is a relationship diagram showing the relationship between the microwave irradiation time and temperature of the resin component, and Figure 2 is a relationship diagram showing the relationship between the composition ratio of the monomer added to the unsaturated polyester, gelation time, and temperature rise (microwave heating for 3 minutes). It is a relationship diagram showing a relationship.

Claims (1)

[Claims] 1. Contains as composition components an unsaturated polyester prepolymer consisting of a condensate of an unsaturated polybasic acid, a saturated polybasic acid and a glycol, and a polymerizable vinyl monomer containing styrene and diallyl phthalate, and polymerizes it. A microwave-curable resin composition characterized in that the proportion of diallyl phthalate in the vinyl monomer is 15 to 90%. 2. Claim 1, characterized in that the resin composition contains multiple types of polymerization initiators with different half-lives.
The microwave curable resin composition described in 2.