JPS6029728B2 - Method for producing cured novolac fiber reinforced epoxy resin composite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for making cured nopolac fiber reinforced epoxy resin composites.

Conventional epoxy resins do not produce water or other volatile substances as by-products during curing and have little volume shrinkage, so they have good electrical insulation and dimensional stability, so they are used for capacitors. It is widely used in electrical parts and tools such as embedded coils, printed circuit laminates, switch gears, mechanical parts such as pipes and tanks, and fixtures in chemical factories, but there is still a lack of heat resistance. It is not something that is highly durable and has long-term heat durability for practical use.
In general, materials that have a high temperature for practical use have poor moldability and low strength; conversely, materials that have good moldability and strength for practical use are
Its temperature for practical use is as low as 12,000 degrees.

In addition, as safety regulations and pollution prevention measures have been strengthened regarding reinforcing materials, natural fibers and synthetic fibers have poor noise and heat resistance, and in the case of asbestos and glass, which have traditionally been used for heat-resistant and non-combustible materials, The dust regulation is 8ibe/
CC has been changed from CC to 2i skin RS/CC, and asbestos may cause silicosis to workers, while glass may cause skin damage to workers, so it is not handled in factory production. Moreover, both types have extremely poor wetting at the interface with the resin, and although glass is usually treated with chemical surface treatments, the molded composites tend to delaminate at the interface between the resin and glass when heated. This has caused problems such as ``gas bulges.''

For this reason, such a reinforced composite of the two tends to gradually deteriorate in strength and rapidly decrease in insulation resistance value due to heat aging, which poses many practical problems. For example, in the case of high-voltage parts of color televisions in which various fiber-reinforced composites are used, epoxy resins with good moldability or fiber-reinforced epoxy resin composites are widely used because of their complex shapes.

However, in recent years, the trend in the television industry has been toward miniaturization and weight reduction, and as high-voltage current is turned on and off to smaller and more compact components, the temperature of the components increases considerably.
The surrounding temperature is even higher than the parts themselves, and in the United States, there have been fires caused by TVs catching fire, and consumers are demanding higher safety, so these parts have to be heat-resistant and heat-resistant. It is desired that it be highly durable. However, in the case of ordinary fiber-reinforced epoxy resins, although their short-term heat resistance is relatively good at 200:00, their durability against long-term high-temperature use is quite low. For example, if heat aged for 10 days at a temperature of 150°C, the weight loss rate will be approximately 10%, and in 30 days the weight loss rate will be approximately 30%.
%, it becomes about 40% in 100 days, and even after heat aging of 150 oo, it is in a state where it can no longer withstand continuous use at high temperatures for 10 days or more, and has poor thermal durability. (In this case, the test piece is 4 x 10 x 18 pieces,
The curing conditions were 140 qo x Tsumugi rs. ) Therefore, it is currently desired to further improve thermal durability. In addition, special resins such as Teflon resin and polyimides are available as resins that have a heat resistance of 250o○ or more and have good heat durability, but such resins have very poor moldability and cannot be molded into complex shapes. It cannot be used for the desired purpose. The purpose of the present invention is to
The above-mentioned defects have been improved without reducing the excellent properties of the conventional fiber-reinforced epoxy resin composite, and the thermal durability has been improved to 1.00 at 200 oo, which is the temporary heat resistance temperature of the conventional product.
To provide a cured noporac fiber-reinforced epoxy resin composite which has excellent thermal durability at high temperatures and has a unique thermal resistance.
Another object of the present invention is to provide a method for industrially easily and inexpensively producing a cured noporac fiber-reinforced epoxy resin composite having such excellent properties.

Still other objects will become apparent from the description below. That is, the present invention provides fiber diameters of 5 to 50, which are obtained by curing uncured Nopolac fibers obtained by melt-grading Nopolac resin with aldehydes.
1. Conditions (1) for using epoxy resin with cured/polac fibers having a fiber length of 1 to 2 and a weight increase rate of 5 to 20% of the uncured nopolac fiber weight due to the curing treatment, conditions (1), 15
SM Mi 90.300 Mi D. M Mi 3600...Mold after blending and kneading to satisfy (1), followed by post-curing, 20
The epoxy resin composite obtained by heat aging for 1.00 hours at a temperature of 0qo has the formula (0) 0. $o-SS
O... (b) A method for producing a cured nopolac fiber-reinforced epoxy resin composite having thermal durability.

In the present invention, "having heat durability" means high temperature,
This means that the composite maintains strength sufficient for practical use even after long-term heat aging.

The epoxy resin applied to the present invention has two or more epoxy groups in one molecule, such as bisphenol A
, polyhydric phenols such as Decol, resorcinol, phenol, polyhydric phenols of noporac type such as cresol, polyhydric alcohols such as glycerin, ethylene glycol, oxalic acid, succinic acid, adipic acid, dimerized or trimerized relenone. Aliphatic polycarboxylic acids such as acids, aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and aniline, toluidine, bis(4
Polyglycidyl ethers and polyglycidyl esters obtained by reacting polyvalent amines such as -aminophenyl)methane and bis(4-methylaminophenyl)methane with epichlorohydrin in the presence of a basic catalyst. and polyglycidylamine, pinylcyclohexene dioxide epoxidized by peracid method, limonene dioxide, dicyclobentadiene dioxide, 3,4-epoxy-6
-Methylcyclohexy-methyl-3,4-epoxy 6-methylcyclohexanecarboxylate, epoxidized polyolefins such as epoxidized polyptadiene, and epoxidized vegetable oils, among others, produced by the condensation reaction of bisphenol A and epichlorohydrin. Polyglycidyl ethers are preferred epoxy resins.

The uncured novolac fiber of the present invention includes phenols,
For example, a novolac resin consisting mainly of methylene bonds, which is an initial polymer obtained by reacting phenol, cresol, xylenol, resorcin, or a derivative thereof, with an aldehyde, such as formaldehyde, acetaldehyde, or furfural under an acid catalyst, is heated with an inert gas, e.g. Heating in the presence of carbon dioxide, nitrogen, etc. to give a free-flowing melt, which is then forced into an inert cooling medium, such as air, nitrogen or water, through a spinneret with a nozzle of the desired diameter; It was pulled out, cooled and solidified, and then rolled up.

Melt-spun uncured novolac fibers can be cured in an aqueous mixed solution of an acidic catalyst and aldehydes, or precured in an aqueous mixed solution of an acidic catalyst and aldehydes, and then further cured in a mixed aqueous solution of a basic catalyst and aldehydes. Do this under proper heating. Examples of the aldehydes for curing the hardened novolac fibers include formaldehyde, acetaldehyde, and furfural. The cured novolac fiber thus obtained has a fiber diameter of usually 5 to 50 mm, preferably 10 to 40 mm, more preferably 12 to 30 mm, and a fiber length of usually 1 to 20 mm, preferably 3 to 1 mm.
5 skin, more preferably 5 to 10 skin.

Furthermore, the cured novolac fibers have an increase in weight by usually 5 to 20%, preferably 7 to 17%, more preferably 10 to 15%, based on the weight of the uncured/volatile fibers. In the present invention, the content of the cured novolak fiber in the epoxy resin in the epoxy resin composite that is usually obtained is 15 to 9% by weight, preferably 30 to 85% by weight, more preferably 50 to 8% by weight. For example, blend it with a hardening agent such as various organic polyamines, organic acid anhydrides, etc. using a Henschel, kneader, mixer, or hot roll, or methyl resin such as phenolic resin, melamine resin, urea resin, etc. After thoroughly dispersing the cured novolac fibers in the epoxy resin, the cured novolak fibers are thickened with resins having a epoxy resin and a latent curing agent such as BF3-amine armor salt, DICY, etc., and then treated with light, heat, radiation, or a suitable cross-linking agent. It is cured and molded under the combined use of

The cured novolac fibers may be mixed with other organic fibers or inorganic fibers such as glass or asbestos in an amount not less than 5% by weight of the total weight of the cured novolac fibers. When the fiber length of the cured noporac fiber, which is the reinforcing material of the composite obtained by the present invention, is one-sided, when external stress is applied to the composite, the stress is sufficiently dispersed in the composite because the fibers are short. However, the effect of improving strength is poor.

On the other hand, if the fiber length exceeds 2 lenghts, the fibers will become entangled with each other when mixed with the resin, resulting in a flock-like structure, and no improvement in strength can be expected. Further, if the weight increase rate of the cured nopolac fibers relative to the uncured novolac fibers is less than 5% by weight, the degree of molecular crosslinking of the cured nopolac fibers is small, and therefore, the strength of the fibers themselves is poor, so improvement in the strength of the composite cannot be expected.

On the other hand, if the weight increase rate exceeds 2% by weight, the cured novolac fibers require a very long treatment time and are not advantageous for industrial production, and the resulting cured novolac fibers are brittle and cannot be used with epoxy resin. The adhesion and reactivity with other materials are also poor, and as a result, the thermal durability of the composite is impractical, and its electrical properties and heat resistance also tend to decrease. In the present invention, the relationship between the fiber diameter of the cured novolac fiber and the fiber content is extremely important, and first of all, if we look at the fibers less than 5 peaks, the fiber surface area is large, so it is difficult to The fibers have many contact points with the resin, and are highly reactive as described below, but the fibers tend to form flocks and have poor dispersibility, which is undesirable as it becomes an obstacle during molding.

On the other hand, if it is more than 50 French, when uncured/Pollack fiber is cured, crosslinking will gradually proceed from the fiber surface, so the curing process will take a long time, which is disadvantageous in terms of industrial production. Moreover, in terms of the reinforcing effect of the composite, the fiber surface area is small and there are few interface points with the resin, so the reactivity described below is poor, and the heat resistance and heat durability are also insufficient. Regarding the content of cured novolac fibers, if the content is 15% by weight, the resin in the epoxy resin containing cured novolac fibers will flow too much, resulting in poor moldability, which is not only not advantageous in industrial production, but also makes it difficult to form composites. Its strength, heat resistance, combustibility, electrical properties, etc. are not practical. On the other hand, if it exceeds 9% by weight, the resin will not flow well during molding in the fiber blended resin, which is not advantageous in terms of industrial production. Simultaneously cured/The product (D・M) of the fiber diameter (Dr) of the borac fiber and the fiber content (M weight %) in the resulting composite is usually 300 to 3
600, preferably 500 to 3200, more preferably 900 to 2400, in order for the composite to maintain excellent heat resistance and thermal durability. DM
If the value is less than 30 degrees, the epoxy resin may flow too much during heat molding of the fiber compound resin, the curing time of the molded product will be long, and productivity will be poor, and the total interfacial adhesive strength between the cured novolac fiber and the epoxy resin will be poor. The composite is heat resistant,
It also has poor thermal durability. On the other hand, if the DM value exceeds 3600, the resin compound will be bulky and difficult to handle, and molding will require the use of a very special high-pressure molding method, and even if obtained, the composite will have poor thermal durability and electrical properties. becomes inferior. Specifically, the blending and molding method of the cured novolac fiber and the epixy resin in the present invention includes the blending and molding method of known fiber-reinforced composites, so-called F, R, P, such as hand lay-up method, spray-lay-up method, The Briform matched metal die method, the Brimix method, the filament winding method, the continuous pultrusion method, and the sheet molding compound method can be applied, and in particular, for solid type epoxy resins, the melting method [for example, the epoxy beretz method or the E-Pak method], Compression molding methods (for example, lower pressure (generally 50 to 300 k9/s)) than phenol resins, etc., or transfer molding methods (for example, pot type or plunger type) are applied.

Furthermore, the obtained composite was heated to a temperature higher than the molding temperature (20 to 3
The curing time after post-curing is 10~
30 minutes is preferred). The epoxy resin composite thus obtained has a temporary heat resistance temperature of a conventional epoxy resin composite.

A product that satisfies the following conditions for heat aging at 200° C. for 1.00 feeding hours will not have the desired heat resistance and heat durability.

That is, the epoxy resin composite according to the present invention is 200o01.
The bending strength after heat aging for 000 hours (Sk9/Side 2: hereinafter S represents the bending strength after heat processing for 200oo and 1.00 hours) is the initial strength before aging (Sok9/Side 2). : Hereinafter, So indicates the initial bending strength). The above relationship is given by the following equation 0'. 0. $o-Smi○...(0) If the degree of decrease in S exceeds 10% of So, the physical properties of the composite will change significantly over time when used at high temperatures, so molded products should be prepared in anticipation of changes in physical properties over time. This makes the design difficult and is not practical.

Moreover, even if it were possible to design with this temporal change in mind, the content M of cured noporac fibers and the wall thickness of the molded product would have to be extremely increased, which would affect all aspects of the manufacturing process, product application, and manufacturing cost. However, it cannot be said to be desirable due to the limitations imposed by the If S is less than 11.5, the structural material is likely to break and cannot be used as a reinforcing material, so it is necessary to improve the strength by using other auxiliary materials or increasing the wall thickness.
It is undesirable because its uses are limited, such as being unsuitable for precision and sophisticated parts.

Therefore, it is desired that S is usually 11.5 or more, preferably 12.3 or more, and more preferably 13.5 or more.
The cured novolac fiber in the present invention has a three-dimensional crosslinked structure due to the generation of methylene groups, methylol groups, and dimethylene ether groups through the curing process, and its molecules have a high carbon content, so they are put into the flame. However, there is no melting, only carbonization, and no decomposition and combustion.

Therefore, when cured noporac fibers are used as a reinforcing material for an epoxy resin composite as in the present invention, not only is the composite itself oxidized, but the cured noporac fibers are BAE
It has a chemical structure very similar to that of epoxy, and also has some active groups, so it is very compatible with epoxy. Furthermore, since the methylol groups and dimethylene ether groups contained in the cured noporac fibers chemically bond with the epoxy resin during combustion molding, a composite with extremely good adhesion at the boundary between the fiber and the resin can be obtained. Therefore, since the epoxy resin composite according to the present invention has a strong chemical bond between the matrix resin and the reinforcing material, it has surprisingly high heat resistance and heat durability, and has an excellent secondary effect of insulation. In addition to exhibiting resistance, the specific gravity of the cured novolak fibers is low, making it possible to reduce the weight of the composite, and thus also achieving high specific strength. Thus, the cured/borac fiber-reinforced epoxy resin composite according to the present invention has excellent thermal durability of more than 1.00 feeding hours even at high temperatures of 200 qC, where conventional epoxy resin composites could not be used for long periods of time. This has made it possible to manufacture epoxy resin composite molded products that have the long-awaited complex shapes and thermal durability at high temperatures.

The present invention will be specifically explained below using Examples.

Incidentally, bending strength, volume resistance, combustibility, heat resistance, and Rockwell hardness were measured according to JIS-K-6911. Furthermore, in the examples, "parts" and "%" mean "parts by weight" and "% by weight," respectively. Example 1 Number average molecular weight is 8
00 novolac resin with 252 holes and 0.2 holes? The yarn was spun using a spinneret at a speed of 15,000 mm and wound at a speed of 35 mm/kg.

Next, this material was soaked at 20 qo in a mixture of 17.5% by weight of hydrochloric acid and 17.5% by weight of formaldehyde for 3 hours.

The temperature was raised to C and maintained for 5 hours, followed by washing with water for 1 hour. Further, this product was added to a methanol bath containing 4% by weight at a temperature of 6%.
After treatment at 5° C. for 1.5 hours, it was washed with water and dried. The obtained cured novolac fibers had an average fiber diameter of 14.6r and a degree of curing of 10% in weight increase compared to uncured novolak fibers.
．． % by weight of turtle.

Next, the cured novolak fibers thus obtained were cut into the respective fiber lengths shown in Table 1, and then each was treated using the method shown below.

First, powdered epoxy resin [Mitsui Epoxy ■, R301]
1.000 parts of methyl ethyl ketone (MEK) and 40 parts of methyl ethyl ketone (MEK) were mixed together for 3 hours to prepare a mixed solution A.

Next, 4 parts of dicyandiamide (DICY), 2 parts of penzyldimethylamine (BDMA), 40 parts of methylcellosolve
A solution B was obtained by mixing and dissolving these parts. Furthermore, 70 parts of A liquid, B
5 parts for the epoxy resin composite to obtain a cured/borac fiber content of 221 parts of liquid.
The solvent was removed after mixing to give a weight percent of . Next, this material was treated in a dryer at 150o for 7 minutes to make a prepreg, and then transfer molded using a 17p mold at a maximum pressure of 20k9/base with a curing time of 5 sides/rib to form a prepreg of 200o. After curing for 30 minutes, the product was manufactured.

Table 1 shows the results of the thus obtained samples regarding the cut length of the cured/Polac fiber, the formability during molding, and the bending strength after heat aging.

Table 1 Example 2 The uncured novolac fiber of Example 1 was soaked in a mixture of 17.5% by weight hydrochloric acid and 17.5% by weight formaldehyde at a temperature of 2500°C, and the temperature was raised to 98°C over 3 hours. After heating and holding for 3 hours, washing with water was performed for 2 hours.

Further, this product was treated in a 25% by weight formaldehyde bath at a temperature of 8,000 for 3 hours, and then washed with water for 1 hour. Next, add this material to 1.5% by weight of ammonia at a temperature of 65%.
00 for 3 hours, followed by washing with water and drying. The obtained cured novolac fibers had an average fiber diameter of 32.6 mm and a degree of cure of 14% by weight compared to the uncured novolac fibers.
It belonged to Separately, according to Example 1, fused paper yarn was prepared by changing the diameter and winding speed, and the curing treatment was performed using the method described above. Novolac fibers were prepared and molded according to Example 1 so that the fiber content was 6% by weight to obtain a product. Table 2 shows the relationship between the diameter of the cured novolac fiber, moldability, bending strength, and volume resistance for the samples thus obtained. Table 2 Fiber diameters of 3.2 mm and 56.3 mm show bending strengths of 14.9 and 15.0 kg/side 2 after aging, but could not reach 90% of the initial bending strength So, and Due to severe deterioration, it cannot be put to practical use.

Example 3 The uncured novolak fiber obtained by the method of Example 1 was immersed in the same treatment solution at 20 oz, heated to 98 qo in 3 hours, and then 0.0 qo. Duration, 1 hour, 2. The holding time was changed to 5 hours, 1 feeding time, and 4 feeding hours, and this product was further treated according to Example 2.

The degree of hardening of the cured noporac fibers thus barreled is 3. Tow weight %, 5.2 weight %, 10. Tortoise weight %, 14.7 weight %, 19. Turtle weight%, 23.2% by weight
Also, the fiber length was 1 x 1, and the fiber diameter was 23.7 x 1. A product was molded according to Example 1 so that the content of these cured nopolac fibers was 4% by weight.
Table 3 shows the relationship between the degree of hardening, strength, burning rate, and Rockwell hardness of the cured noporac fibers. Table 3 Example 4 The uncured novolac fiber obtained in Example 2 was cured according to Example 2, and the degree of curing was 19.5% in weight increase rate relative to the novolac fiber. Kame weight %, fiber length 15 skin, average fiber diameter 5.1 mm, 10.3 french, 14.6 french, 23.7r, 32.6 french,
Example 1.48.6. The same epoxy resin as in Example 1 was blended with various fiber contents in the resulting resin composite. It was molded into a product according to the following.

However, if the content exceeded 9% by weight, a satisfactory molded article could not be obtained. DM value at this time and 200oo, 1.0
Bending strength after heat aging with 0 feeding time (Sk9/rib2
) are shown in Table 4.

In addition, at this time, the relationship between the DM value, initial bending strength (So), bending strength after aging (S), and (0.$o-S) value was determined based on the fiber content of 2% by weight, 4% by weight, and 70% by weight. , 9 cloud cover%, fiber diameter 5.1 mountains, 146 Buddhas, 32.6 Buddhas, 48.6
Table 5 shows the relationship between Buddha and Buddha.

In Tables 4 and 5, the portions surrounded by chain lines are examples of the present invention.

4 Table 5 In the example of [Content 20 - Diameter 5.1] in Table 5, the epoxy resin has high fluidity during heat molding of the fiber blended resin, making molding very time-consuming and the resulting product also poor. It had poor heat durability.

Further, in the case of [content 90/diameter 48.6], the mixture before molding was very bulky and molding was quite difficult. Furthermore [content 20
- When aging was continued at 20,000 for both the example with diameter 48.6 and the example with content 20 and diameter 32.6 (example of the present invention), the former showed cracks on the composite surface when checked at 1.100 hours. On the other hand, the latter had no defects such as cracks even when checked after 1.50 field hours. Example 5 Among the cured Nopobok fibers obtained in Example 2, those with a fiber diameter of 10.3 mounds were cut into fiber lengths, and the fibers and epoxy resin were mixed in a ratio of 30/70 and 50/50.
, 90/10 and molded according to Example 1 to obtain a product.

In this case, the heating aging time is changed, **DM
value, initial strength (So), aging strength (St) at each aging time, and [0. Table 6 shows the $o-St] values.

Table 6 Example 6 The cured novolac fiber (5 fiber length) obtained in Example 1, asbestos (R-7) and glass fiber (10 side) were mixed and thickened in an epoxy resin in a ratio of 40/60. A product was prepared according to Example 1.

In this case, the bending strength (St) of those without heat aging and those treated for 1 feeding time, 10 mouse hours, and 1.000 hours
Table 7 shows this. Seventh Example 7 The cured novolac fiber obtained in Example 1 was mixed with epoxy resin (the epoxy resin used in Example 1, R301), xylene resin (Lignite Co., Ltd., Lignol), and diallylphthalate resin (Sumitomo Chemical Co., Ltd., Dapon). ) were blended in a proportion of 35% by weight according to Example 1 to obtain a molded product.

Separately, asbestos (R-7) was mixed, mixed, and molded using the same process to produce a product. Table 8 shows the temporary heat resistance and specific bending strength of the cured novolac fiber and asbestos-reinforced thermosetting resin composite thus obtained. No. 8 Asbestos-reinforced composites have lower specific strength than cured noporac fiber-reinforced composites, and have similar difficulties in reducing the weight of the composites.

Claims (1)

[Scope of Claims] 1. Fiber diameter 5-50 obtained by curing uncured noporac fibers obtained by melt-spinning a noporac resin with aldehydes.
Condition (I) 15: cured noporac fibers having a fiber length of 1 to 20 mm and a weight increase rate of 5 to 20% of the weight of the uncured noporac fibers due to the curing treatment are used as an epoxy resin.
≦M≦90・300≦D・M≦3600…(1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ After mixing and kneading, it is molded, and then it is post-cured. The epoxy resin composite obtained by heat aging for 1.000 hours at a temperature of 200°C has the formula (II) 0.9So-
S≦...(II) ▲Mathematical formulas, chemical formulas, tables, etc.▼ A method for producing a cured noporac fiber-reinforced epoxy resin composite having thermal durability properties. 2.Cured noporac fibers are cured in a mixed aqueous solution of an acidic catalyst and an aldehyde, or those precured in the mixed aqueous solution are further cured in a mixed aqueous solution of a basic catalyst and an aldehyde. manufacturing method. 3. The manufacturing method according to claim 1, wherein the cured noporak fiber has a fiber diameter of 10 to 40 μm. 4. The manufacturing method according to claim 1, wherein the cured noporak fiber has a fiber length of 3 to 15 mm. 5. The manufacturing method according to claim 1, wherein the weight increase rate of the cured noporac fibers due to the curing treatment is 7 to 17% of the weight of the uncured noporac fibers. 6. The manufacturing method according to claim 1, wherein the epoxy resin is a polyglycidyl ether produced by a condensation reaction of bisphenol A and epichlorohydrin. 7. The manufacturing method according to claim 1, wherein in condition (1), M is 30≦M≦85. 8 Under condition (1), D・M is 500≦D・M≦32
00. The manufacturing method according to claim 1 or 6.