JPH045043B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an epoxy resin composition containing a novel bisphenol A novolak resin as a curing agent. (Prior art) Novolac resins obtained by dehydrating and condensing a phenol compound and formaldehyde in the presence of an acidic catalyst are well known, and novolac resins obtained using bisphenol A as the phenol compound are It is known as phenol A novolak resin. This is mainly mixed with an epoxy resin as a curing agent for the epoxy resin and used for manufacturing prepregs and circuit-forming laminates. Conventionally known bisphenol A novolac resins have a number average molecular weight of 400 to 1,600 and a bisphenol A monomer content of 15 to 40% by weight. On the other hand, in the production of laminates using epoxy resins, dicyandiamide is the predominant epoxy resin curing agent. Generally, a laminate is manufactured by dissolving an epoxy resin and a curing agent in a solvent such as methyl ethyl ketone, and then adding a curing accelerator to form a resin varnish. Next, after impregnating the glass cloth with this resin varnish,
The solvent is evaporated in a dryer to form a prepreg. This prepreg is laminated in an appropriate amount, or copper foil is further laminated and heated and cured under press pressure. The thus obtained laminate is subjected to processing such as etching and drilling to form a circuit. In addition, in the field of laminates, resin hardenability,
Required items include heat resistance of the cured resin, drillability of the laminate, moisture resistance, electrical properties and hue stability, and stability of the resin varnish. (Problems to be Solved by the Invention) Epoxy resin compositions prepared using dicyandiamide as a curing agent for epoxy resins have problems such as curability of this composition (needs high temperature heating), heat resistance of the cured resin, and lamination. Since the color stability and drilling workability of the board are poor, it is expected that an epoxy resin composition prepared using bisphenol A novolak resin, which has excellent curability as a hardening agent, will improve these drawbacks. be done. Therefore, the present inventors conducted various studies on epoxy resin compositions prepared using bisphenol A novolak resin, which is conventionally known as a curing agent, and found the following. That is, the conventionally known bisphenol A
The epoxy resin composition prepared using the novolac resin had no particular problems with respect to the drillability of the laminate, hue stability, and electrical properties, but (1)
The curing properties of the resin are insufficient (it can be cured at a lower temperature than dicyandiamide, but it will not cure sufficiently unless it is relatively high temperature), (2) the heat resistance of the cured resin is poor, (3) the storage stability of the resin varnish is poor. (4) The compatibility between the epoxy resin and the bisphenol A novolak resin is poor, resulting in whitening of the prepreg and insufficient curing. (Means for solving the problems) The present invention provides (A) an epoxy resin and (B) a bisphenol A novolak resin,
The present invention relates to an epoxy resin composition comprising a bisphenol A novolak resin in which bound formaldehyde is 0.7 to 0.9 mole based on the phenol component and the phenol monomer content is 10% by weight or less. In the present invention, epoxy resin refers to a compound having two or more epoxy groups in the molecule, such as one obtained by the reaction of a polyhydric phenol such as bisphenol A and epichlorohydrin, 1,4-
Those obtained by reacting polyhydric alcohols such as butanediol with epichlorohydrin, polyglycidyl ethers of phenol novolaks, polyglycidyl ethers of cresol novolaks, polyglycidyl ethers of polybasic acids such as phthalic acid and hexahydrophthalic acid, N-polyglycidyl derivatives of amine amides or compounds with heterogeneous nitrogen bases, (3',4'-epoxycyclohexylmethyl)-
Examples include alicyclic epoxy resins such as 3,4-epoxycyclohexanecarboxylate, and halogen-substituted products thereof such as bromine and chlorine. The bisphenol A novolac resin in the present invention has a content of bound formaldehyde per mole of the phenol (bisphenol A) component in the resin.
It is 0.7-0.9 mol. If it is less than 0.7 mol, the phenol (bisphenol A) monomer content increases, but the number average molecular weight decreases, resulting in a decrease in curability and heat resistance. On the other hand, if it exceeds 0.9 mol, the molecular weight becomes too high and the compatibility with the epoxy resin decreases. Here, the number of moles of bound formaldehyde per mole of the phenol (bisphenol A) component is the 1.5 ppm peak based on the methyl group in the bisphenol A component of the nuclear magnetic resonance spectrum of the bisphenol A novolak resin and the bisphenol A component.
It was determined from the area intensity ratio of the peak at 3.75 ppm, which is based on the methylene group formed by addition and condensation of formaldehyde. The solvent used in this measurement is dimethyl sulfoxide (however, all hydrogens in the methyl groups are diuterium, DMSO
−d ₆ ). The bisphenol A novolak resin in the present invention has a phenol (bisphenol A) monomer content of 10% by weight or less. If this content exceeds 10% by weight, the curability and heat resistance of the cured resin will decrease. In addition, phenol (bisphenol A) component 1
If the number of moles of bound formaldehyde and the phenol (bisphenol A) monomer content are not within the above ranges, the storage stability of the resin varnish will be poor. The bisphenol A novolac resin according to the present invention preferably has a number average molecular weight of 600 to 2,000. When the number average molecular weight is less than 600, the heat resistance of the cured resin tends to decrease, and when it exceeds 2000, the compatibility with the epoxy resin tends to deteriorate. Further, the bisphenol A novolak resin in the present invention preferably has a dispersity of 2.2 or less. When the degree of dispersion is within this range, it is effective to prevent a part of the curing reaction from proceeding during drying of the prepreg and to prevent discoloration of the laminate by lowering the curing temperature. Here, the degree of dispersion is the ratio of weight average molecular weight/number average molecular weight. In the present invention, the weight average molecular weight and number average molecular weight are determined by gel permeation chromatography. The calibration curve is based on bisphenol monomer (molecular weight 228), a compound having 2 to 7 bisphenol A components in the reaction product obtained by reacting 1 mol of bisphenol A with 0.4 to 0.8 mol of formaldehyde under an acidic catalyst. Use what you have created. The eluent is tetrahydrofuran, the flow rate is 1.7 ml per minute, the temperature is 38° C., and the pressure is 48 Kg/cm ² . The bisphenol A novolac resin in the present invention can be produced as follows. 0.4 to 0.8 mol of formaldehyde is reacted with 1 mol of bisphenol A in an aromatic solvent such as benzene, xylene, toluene, etc. in the presence of an acidic catalyst (first step). Then, 25 to 400% by weight based on the obtained resin and the charged bisphenol A.
of toluene and stirred for 0.5 hours or more at a temperature of 80°C or higher and lower than the boiling point of toluene, and when left to stand at that temperature, it will separate into two layers. The viscous or slightly viscous liquid is separated and the toluene is removed from it (second step). Each step will be explained in more detail. In the first step, formaldehyde is used in an amount of 0.4 to 0.8 mol per mol of bisphenol A.
If it is less than 0.4 mol, unreacted bisphenol A will increase and it will be difficult to increase the amount of bound formaldehyde to 0.7 mol or more per mol of bisphenol A component in the final resin.
In addition, if it exceeds 0.8 mol%, there is a risk of gelation during the reaction, and the generation of molecular species with a molecular weight of more than 20,000 increases, which tends to reduce the compatibility of the final resin with the epoxy resin, and may cause This increases the number average molecular weight and dispersity. Formaldehyde can be used in the form of paraformaldehyde, formalin aqueous solution, α-polyoxymethylene, and the like. The aromatic solvent is preferably one that forms an azeotropic composition with water. The amount used is 20 to 100% by weight based on the amount of bisphenol A used.
is preferred. Furthermore, it is preferable to use toluene as the aromatic solvent since the second step can be carried out following the first step. As the acidic catalyst, those normally used in the production of phenol novolac resins, such as mineral acids such as sulfuric acid and hydrochloric acid, and organic acids such as para-toluenesulfonic acid and oxalic acid, can be used. It is preferably 0.1 to 2% by weight based on phenol A.
The reaction temperature was 70 to 90°C for 1.5 to 4 hours.
It is preferable to carry out the addition reaction of formaldehyde mainly to bisphenol A, and then raise the temperature to 100°C or higher and lower than the reflux temperature to carry out the reaction, and to carry out a dehydration condensation reaction. In this case, the process is carried out while removing condensed water,
It is preferable to carry out the reaction until no condensed water is produced. This time is usually 3 to 5 hours. Thereafter, an alkali is added to the reaction solution in an amount equivalent to the acidic catalyst in order to neutralize the acidic catalyst. Examples of the alkali include lithium hydroxide, sodium hydroxide, potassium hydroxide, triethanolamine, and morpholine. The first obtained in this way
The step reaction solution is subjected to the second step after the solvent is removed by distillation or the like (when toluene is used as the solvent, the reaction solution may be left as it is). In the second step, the amount of toluene in the first step is 25 to 400% by weight based on the charged bisphenol A.
The resin obtained in the process and toluene are mixed or toluene is added to the reaction solution. The resin solution thus obtained is then heated and stirred at 80° C. or higher and below the boiling point of toluene for 0.5 hours or more. After this, by leaving the resin solution at the same temperature, the upper and lower
Separate into layers. This lower layer consists of a viscous or slightly viscous liquid containing toluene and a toluene-containing bisphenol A novolak resin, and the upper layer has two bisphenol A monomers and a small amount of bisphenol A in the molecule. This is a toluene solution in which formaldehyde reactants are dissolved. Further, this separation can also be performed forcibly using a centrifugal separator. After separating and collecting the lower layer, the toluene is removed by distillation to obtain the bisphenol A novolac resin according to the present invention. In the second step, toluene is added to bisphenol A.
On the other hand, if the amount is less than 25% by weight, the toluene becomes a viscous substance that is absorbed into the bisphenol A novolac resin, and if it exceeds 400% by weight, the relatively low molecular weight molecular species of the bisphenol A novolac resin are absorbed into the upper layer. It dissolves in toluene, reducing the yield, and when there is a large excess, it becomes a homogeneous solution of toluene. If the second step is performed once, the bisphenol A according to the present invention is usually
A novolak resin can be obtained, which may optionally be repeated two or more times. In this case, the amount of toluene mentioned above is based on the amount of resin. In the second step, the number average molecular weight and dispersity of the resulting bisphenol A novolak resin can be adjusted by adjusting the treatment conditions. The bisphenol A novolak resin thus obtained can be used as it is without removing the neutralized salts contained therein, or after removing the neutralized salts by hot water treatment etc.
Can be put to use. The solvent used in the second step is toluene, but other solvents such as benzene and xylene cannot achieve the purpose. In addition, if only to produce a bisphenol A novolak resin with a low bisphenol A monomer content, it is possible to increase the reaction rate by blending bisphenol A and formaldehyde in approximately equal moles, but with this method, Since bisphenol A has four sites capable of reacting with formaldehyde, it gels during synthesis and cannot be used in practice. Moreover, even if the reaction is carried out with care so that gelation does not occur, the bisphenol A of the present invention
It is not possible to obtain a novolak resin that satisfies the essential conditions, and it contains a large amount of molecular species with a molecular weight exceeding 20,000, resulting in poor compatibility with epoxy resins in particular. The bisphenol A novolak resin of the present invention may contain phenols other than bisphenol A as its constituent components within a range that meets the purpose of the present invention. Examples of such phenols include cresol and phenol, which are used together with bisphenol A during the above production. In the present invention, the epoxy resin as the component (A) and the bisphenol A novolak resin as the component (B) have a ratio of hydroxyl groups in the component (B) to 1 equivalent of the epoxy group in the component (A).
It is preferable to mix it in an amount of 0.8 to 1 equivalent. The epoxy resin composition according to the present invention comprises component (A) and
Component (B) may be mixed and used, or dissolved in an organic solvent and used in the form of a varnish. Examples of organic solvents include toluene, methyl ethyl ketone,
Methyl cellosolve, ethyl cellosolve, butyl cellosolve, methanol, etc. are used. In the epoxy resin composition according to the present invention, curing agents for epoxy resins other than the above-mentioned component (B) can be used in combination within a range that meets the purpose of the present invention. A curing accelerator can be added to the epoxy resin composition according to the present invention. As a curing accelerator, 2-ethyl-4-methylimidazole, 1-
Cyanoethyl-2-phenylimidazole, 1-
Benzyl 2-methylimidazole, 1-methylimidazole, 1,2-dimethylimidazole, 2
-Phenyl-4-methyl-5-hydroxymethylimidazole, benzyldimethylamine, N,N
- Tertiary amines such as dimethylaniline, tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo(5,4,0)undecene-7,
2-ethylhexanoate of such tertiary amine,
Examples include tertiary amine salts such as phenol salts, oleate salts, formate salts, and acetate salts, and quaternary ammonium salts such as tetramethylammonium chloride, benzylmethylammonium chloride, and benzyltriethylammonium chloride. The curing accelerator is 0.1~
It is preferable to use 5% by weight, particularly preferably 0.3 to 3% by weight. The epoxy resin composition according to the present invention may further contain a reactive diluent, a plasticizer, a filler, a dye, a flame retardant, etc. as appropriate. (Example) Next, an example of the present invention will be shown. Synthesis Example 1 228 g (1.0 mol) of bisphenol A, 22.5 g (0.6 mol in formaldehyde equivalent) of 80% paraformaldehyde, and 171 g of toluene were placed in a 1-glass four-necked flask equipped with a Dean Stark oil-water separator, a thermometer, and a stirrer. was charged, and the temperature was raised while stirring. When the temperature inside the flask reached 80℃, add 1.5g of oxalic acid dihydrate as a catalyst.
Stirring was continued for 3 hours at 80°C. Thereafter, the temperature inside the flask was raised to 105°C, toluene was refluxed, and the water that azeotropically flowed out was removed from the system. Toluene reflux was continued until there was no more water flowing out. The temperature inside the flask at this time was 113°C, and the total amount of water removed was 15.7ml. This amount corresponds to the total amount of water contained in 80% paraformaldehyde, the amount of water in oxalic acid dihydrate, and the amount of condensation water to be generated. The reaction solution at this time was a homogeneous solution. Then, after neutralizing by adding triethanolamine, 228 g of toluene was added, and the temperature was raised to a temperature at which toluene refluxed. At this time, when stirring is stopped, the liquid separates into two layers: a light liquid (upper layer) and a heavy liquid (lower layer).
After raising the temperature and stirring for 30 minutes, stirring was stopped and the reaction solution was separated into two layers, a light liquid and a heavy liquid. The light liquid was removed by decantation to obtain a heavy liquid. Add 400g of toluene to this heavy liquid, and add 30g of toluene under reflux.
After stirring for a minute, stop stirring and separate into two layers again.
The heavy liquid (lower layer) was separated and collected. This was a slightly viscous liquid. Toluene was removed from this using an evaporator to obtain 132 g of pale yellow resin [A]. The softening point of the obtained resin was determined using the ring and ball equation. The residual bisphenol A monomer and molecular weight contained in the resin were measured using gel permeation chromatography (GPC). The separation columns used at this time were GELPACK-R420,
R430 and R440 (both are Hitachi Chemical Co., Ltd. product names,
Porous styrene-divinylbenzene copolymer particles were used as the column packing material) were connected in series one by one, tetrahydrofuran was used as the eluent, a differential refractometer was used as the detector, and the flow rate was 1.75ml/
It was a minute. The chromatogram obtained at this time is shown in FIG. Further, the calibration curve used for calculating the molecular weight is shown below. The number f of formaldehyde bound to 1 mole of bisphenol A component in the resin was determined from the nuclear magnetic resonance (NMR) spectrum of the resin. This spectrum is shown in FIG. That is, from the integrated intensity A of the peak based on the methyl group of the bisphenol A component appearing at 1.5 ppm and the integrated intensity F of the peak based on the methylene group of bound formaldehyde appearing at 3.75 ppm, the formula f = (F / 2) / (A/6). The above results are shown in Table 1. Synthesis Example 2 In Synthesis Example 1, the amount of 80% paraformaldehyde used was 30g (0.8 mol in terms of formaldehyde).
The reaction was carried out in the same manner as in Example 1, except that the amount of toluene used was 115 g, and the light liquid was removed to obtain a heavy liquid. 200 g of toluene was added to this heavy liquid, and after stirring for 30 minutes under toluene reflux, stirring was stopped and the mixture was separated into a light liquid and a heavy liquid, and the light liquid was removed by decantation to obtain a heavy liquid. This operation was then repeated once more. Toluene is removed from the heavy liquid obtained in this way using an evaporator to produce a pale yellow resin [B].
Obtained 178g. Table 1 shows the physical properties of this resin [B] measured in the same manner as in Synthesis Example 1. Synthesis Example 3 The reaction proceeded according to Synthesis Example 1 to obtain a heavy liquid. Next, 200 g of toluene is added to the heavy liquid, and after stirring for 30 minutes under toluene reflux, the stirring is stopped, the light liquid and the heavy liquid are separated, and the light liquid is removed by decantation to obtain the heavy liquid. was repeated four times. Toluene is removed from the heavy liquid obtained in this way using an evaporator to produce a pale yellow resin [C]
Obtained 74g. Table 1 shows the physical properties of this resin [C] measured in the same manner as in Synthesis Example 1. Synthesis Example 4 In Synthesis Example 1, toluene was removed from the toluene solution neutralized by adding triethanolamine using an evaporator to obtain pale yellow resin [D] 231
I got g. Table 1 shows the physical properties of this resin [D] measured in the same manner as in Synthesis Example 1. Also, resin [D]
The GPC chromatogram is shown in Figure 3. Synthesis Example 5 The reaction proceeded in the same manner as in Example 1, except that 33.8 g (0.90 mol of formaldehyde equivalent) of 80% paraformaldehyde was used in Synthesis Example 1, and triethanolamine was added to neutralize. . Toluene was removed from this reaction solution using an evaporator to obtain 235 g of pale yellow resin [E]. Table 1 shows the physical properties of this resin [E] measured in the same manner as in Synthesis Example 1. [Preparation of calibration curve] A calibration curve for determining molecular weight by GPC was prepared as follows. That is, the resin [C] obtained in Synthesis Example 3
GPC measurement was performed and a chromatogram was obtained.
This chromatogram is shown as graph 1 in FIG. In this chromatogram, peaks 2 to 8
are, respectively, in the following general formula [], where n is 0 to
6, and when n is 0, it is a bisphenol A monomer. (However, in the formula, B represents two hydrogens at the ortho position to one hydroxyl group of the bisphenol A monomer, or one hydrogen at the ortho position to both hydroxyl groups, and a total of two hydrogens. (n is 0 or an integer of 1 to 6) Here, the molecular weight of each compound where n corresponds to 0 to 6 is as follows. When n is 0, 228, when n is 1, 469, when n is 2, 709, when n is 3, 949, when n is 4, 1190, when n is 5, 1430, when n is 5 When it is 6, it is 1670. Next, the elution time (minutes) of each compound is plotted on the horizontal axis.
The molecular weight was plotted on a logarithmic scale on the vertical axis, and based on this, a calibration curve 9 was determined as shown in FIG. As is clear from FIG. 4, the calibration curve 9 shows clear linearity.

[Table] Examples 1 to 3 and Comparative Examples 1 to 2 Epicote 828 (trade name of Ciel Chemical Co., Ltd., bisphenol A type epoxy resin, epoxy equivalent 190)
100 parts by weight, and 61 parts by weight of the curing agent obtained in the synthesis example.
After thorough mixing at 130°C, 0.5 parts by weight of 2-ethyl-4methylimidazole was added to prepare an epoxy resin composition. Immediately after creation, it was cured by heating at 170°C for 2 hours. A heat resistance test was conducted on the obtained cured product. The results are shown in Table 2. Heat resistance tests include glass transition temperature and JIS
The heat distortion temperature was measured based on K 7207 (1983). The glass transition point was defined as the temperature that indicates the inflection point of the thermal expansion coefficient when measured using a thermomechanical testing machine.

[Table] Example 4 and Comparative Example 3 100 parts by weight of epoxy resin (epoxy equivalent: 410) obtained by reacting 100 parts by weight of Epicote 828 and 63 parts by weight of tetrabromobisphenol A in the presence of 0.1 part by weight of tetramethylammonium chloride 31 parts by weight of resin [A] or resin [D] as a curing agent and 0.7 parts by weight of 1-cyanoethyl-2-phenylimidazole were dissolved in 120 parts by weight of methyl ethyl ketone to prepare an epoxy resin composition varnish. The gel time of this varnish was measured. Gel time was measured by measuring the time (seconds) until the varnish gelled on a hot plate at 150°C, either immediately after the varnish was prepared or after being stored for one month at 23°C. In addition, after creating the above varnish, a glass cloth (glass cloth of glass fiber whose surface was treated with epoxy silane, thickness 0.18 mm, manufactured by Nitto Boseki Co., Ltd. G-9020-
A prepreg was prepared by impregnating 100 parts by weight of BZG) with 52 parts by weight of varnish as a solid content. This prepreg was dried for 10 minutes in a drying oven at 70-110°C. The appearance of this dried prepreg was visually observed. Further, the dried prepreg was cured by heating at 170° C. for 2 hours, and the change in hue of the prepreg at this time was visually examined. Further, when the dried prepreg was heated to a temperature of 150° C. using a differential scanning calorimeter, the time from the start to the end of heat generation of the dried prepreg was measured. Furthermore, 15 sheets of the above dried prepreg and 6 sheets of 35 μm copper foil were laminated, one sheet of copper foil (however, two sheets were on the front and back sides) for every three sheets of prepreg.
Then, press molding was performed at 150° C. for 15 minutes at a pressure of 40 kg/cm ² to obtain a laminate. This laminate was left standing in a steam atmosphere at 121° C. and a pressure of 2 kg/cm ² for 6 hours, and the weight increase was measured to examine the hygroscopicity of the laminate. On the other hand, 10,000 holes were drilled in the laminate plate obtained above using a 1 mmφ drill, and 200 holes were selected to examine the smear occurrence rate and determine the drillability. The above results are shown in Table 3. Comparative Example 4 A dried prepreg was prepared in the same manner as in Example 4 using resin [D] as a curing agent, and its appearance was visually observed. The results are shown in Table 3.

【table】

[Table] From the results in Table 3, it is clear that the gel time immediately after the varnish was created and after it had existed for one month was the same when resin [A] was used as the curing agent (Example 4) and when resin [D] was used as the curing agent. Compared to the case where it was used as an agent (comparative example 3),
Changes are small and storage stability is excellent. The fact that the prepreg has a semi-transparent appearance and no whitening parts means that
This shows that the epoxy resin and curing agent have excellent compatibility. In addition, a short time until the end of heat generation means that curing is completed in a short time, and in this respect, when resin [A] was used as a curing agent (Example 4)
It can be seen that this is superior to the case where resin [D] is used as a curing agent (Comparative Example 3). Further, from the volume resistivity values, it can be seen that the laminate obtained using resin [A] as a curing agent has better electrical insulation than the laminate obtained using resin [D] as a curing agent. When resin [E] was used as a curing agent (Comparative Example 4), the prepreg turned white. This is resin [E]
As can be seen from the fact that although it contains 18.2% by weight of residual bisphenol A monomer, its weight average molecular weight is comparable to that of resin [B].
This is because there are relatively many molecular species with a molecular weight of over 20,000, which results in poor compatibility with the epoxy resin. (Effects of the Invention) The epoxy resin composition according to the present invention has excellent heat resistance in its cured product, excellent storage stability in a varnish state, excellent curability and hue stability in prepregs, and excellent curability and color stability in laminates. Good volume resistance,
Shows moisture absorption resistance and drill workability. Furthermore, in the composition, the epoxy resin and the bisphenol A novolak resin have excellent compatibility.

[Brief explanation of drawings]

Figure 1 shows the resin [A] obtained in Synthesis Example 1.
GPC chromatogram, Figure 2 is the nuclear magnetic resonance spectrum of resin [A], Figure 3 is the GPC chromatogram of resin [D] obtained in Synthesis Example 4, and Figure 4 is the nuclear magnetic resonance spectrum of resin [A].
The figure shows the GPC chromatogram and calibration curve of resin [C] obtained in Synthesis Example 3. Explanation of symbols, 1 ... GPC chromatogram of resin [C], 9 ... Calibration curve.

Claims (1)

[Claims] 1 (A) epoxy resin and (B) bisphenol A novolak resin,
An epoxy resin composition comprising a bisphenol A novolak resin in which bound formaldehyde is 0.7 to 0.9 mol based on the phenol component and the phenol monomer content is 10% by weight or less. 2. The epoxy resin composition according to claim 1, wherein the bisphenol A novolak resin has a number average molecular weight of 600 to 2,000. 3 The degree of dispersion of bisphenol A novolak resin is
2.2 or less, the epoxy resin composition according to claim 1 or 2.