JPS6215216A - Bisphenol a novolak resin - Google Patents

Abstract

PURPOSE:A bisphenol A novolak resin, having a specific value of ratio of com bined formaldehyde, low content of phenol monomer and improved compatibility with epoxy resin and suitable for a curing agent for the epoxy resins. CONSTITUTION:A bisphenol A novolak resin, contaiing 0.7-0.9mol, based on 1mol phenolic component, combined formaldehyde, <=10wt% phenolic monomer content and preferably 600-2,000 number-average molecular weight and <=2.2 dispersity. The above-mentioned resin is obtained by reacting 1mol bisphenol A with preferably 0.4-0.8mol formaldehyde in the presence of an acidic catalyst, heating the resultant product in the presence of 25-400wt%, based on the bisphenol A, toluene, separating the heated product into two layers at >=80 deg.C and removing the toluene from the lower layer. EFFECT:Capable of improving heat resistance of epoxy resins, shelf stability of resin varnishes, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a novel bisphenol A novolak resin.

(Prior Art) Conventionally, novolak resins obtained by dehydrating and condensing a phenol compound and formaldehyde in the presence of an acidic catalyst are well known. Known as novolac resin. This is mainly used as a curing agent for epoxy resins in the manufacture of laminates such as circuit forming boards via prepregs.

Conventionally known bisphenol A novolac resins have a number average molecular weight of 400 to 1,600 and a bisphenol 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 phenol. Next, after impregnating the glass cloth with this resin pheno.

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 one circuit.

In addition, in the field of laminates, the hardening properties of resins are important.

Required items include heat resistance of the cured resin, drill workability of the laminate, moisture resistance, electrical properties and hue stability, and stability of the resin surface.

(Problems to be Solved by the Invention) When dicyandiamide is used as a curing agent for epoxy resin, the curing property of the resin (high temperature heating is required).

Since the cured resin has poor heat resistance, color stability of the laminate, and drill workability, it is expected that the use of bisphenol A novolak resin, which has excellent curability, will improve these drawbacks.

Therefore, the inventors of the present invention conducted various studies on conventionally known bisphenol A novolac resins and found the following.

That is, when using the conventionally known bisphenol A novolac resin, the drilling processability of the laminate, especially regarding the hue stability and electrical properties.

There were no problems, but (1) the curing properties of the resin were insufficient (dicyandiamide can be cured at low temperatures, but it does not cure sufficiently unless it is at a relatively high temperature); and (2) the heat resistance of the cured resin is poor. (3) Poor storage stability of the resin face (short pot life); and (4) poor compatibility with epoxy resins, resulting in whitening of the prepreg and insufficient curing.

(Means for Solving the Problems) The present invention provides a novel bisphenol A novolac resin to solve the above problems.

That is, 1 the present invention provides a bisphenol A novolac resin in which bound formaldehyde is 0.7 to 0.9 mol per 1 mol of the phenol component and the phenol monomer content is 10% by weight or less. Regarding.

The bisphenol A novolac resin according to the present invention is! The amount of bound formaldehyde is 0.7 to 0.9 mol per mol of the phenol (bisphenol A) component in the resin. At less than 0.7 mole, phenol (bisphenol A
) Curability and heat resistance decrease because the monomer content increases or the number average molecular weight decreases. 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 phenol (bisphenol A) component is.

Based on the methyl group in the bisphenol A component of the nuclear magnetic resonance spectrum of bisphenol A novolak resin <1.5
Based on the ppm peak and the methylene group formed by addition condensation of formaldehyde to bisphenols (3,75
It was determined from the area intensity ratio of ppm peaks. In this measurement, dimethyl sulfoxide (
However, all hydrogens in the methyl group are diuterium.

DMSO-d6) is used.

The bisphenol A novolac resin according to the present invention has a phenol (bisphenol) monomer content of 10% by weight.
It is as follows. If this content exceeds 10% by weight, the curability and heat resistance of the cured resin will decrease.

In addition, the number of moles of formaldehyde bound per mole of phenol (bisphenol A) component (including the phenol monomer contained in the resin) and the number of moles of formaldehyde bound to 1 mole of phenol (bisphenol A) component (including the phenol monomer contained in the resin)
If the bisphenol A) monomer content is not within the above range, the storage stability of the resin face will be poor.

The bisphenol A novolac resin according to the present invention is! Ta. Those having a number average molecular weight of 600 to 2,000 are preferred.

When the number average molecular weight is less than 600, the heat resistance of the cured resin tends to decrease, and when it exceeds 2,000, the compatibility with the epoxy resin tends to be poor.

Further, the bisphenol A novolak resin according to the present invention preferably has a degree of dispersion 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 one charge 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 for bisphenol monomer (molecular weight 228), bisphenol A
Bisphenol A in the reaction product obtained by reacting 1 mole with 0.4 to 0.8 mole formaldehyde under an acidic catalyst.
A compound prepared using a compound having 2 to 7 components is used. Eluent is tetrahydrofuran, flow rate is 1.7
ml! 1 minute, temperature is 38℃ and pressure is 48 kg/cm
'.

The bisphenol A novolac resin according to the present invention can be produced in the following manner.

0.0% formaldehyde per mole of bisphenol A.
4 to 0.8 mol is reacted in an aromatic solvent such as benzene, xylene, toluene, etc. in the presence of an acidic catalyst (first step
process). Next, 25 to 400% by weight of toluene was mixed with the resulting resin charged with bisphenol A.
After stirring for 0.5 hours or more at a temperature above 0°C and below the boiling point of toluene.

When left to stand at this temperature, it separates into two layers, and the lower layer (a selectively viscous or slightly viscous liquid containing toluene and bisphenol A novolak resin) is separated.

Toluene is removed from this (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. 0.4
If the amount is less than 1 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 1 mol of bisphenol A component in the final resin. In addition, if it exceeds 0.8 molty, there is a risk of gelation during the reaction and the molecular weight will be less than 20,000 molar.
If a large number of molecular species are produced, the compatibility of the final resin with the epoxy resin tends to decrease.

In some cases, the number average molecular weight and degree of dispersion are increased.

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 preferably 20 to 100% by weight based on the bisphenol A charged. Also, as an aromatic solvent.

Toluene is used in the second step following the first step.
This is preferable because it allows the process to be carried out.

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. 0 for
．． 1 to 2% by weight is preferred. Reaction temperature is 70-90℃
It is preferable to react for 1.5 to 4 hours to mainly perform an addition reaction of formaldehyde to bisphenol A, and then raise the temperature to 100°C or higher and lower than the reflux temperature to perform a dehydration condensation reaction. In this case, it is preferable to carry out the reaction while removing condensed water 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 that of the acidic catalyst in order to neutralize the acidic catalyst. Examples of the alkali include lithium hydroxide, sodium hydroxide, potassium hydroxide, triethanolamine, and morpholine. In this way,
The obtained first reaction solution is subjected to the second step after removing the solvent by distillation or the like (when toluene is used as a solvent, the reaction solution may be left as it is).゛In the second step,
Toluene is 25-40% of the prepared bisphenol AK.
So that it is 0% by weight.

The resin obtained in the first step is mixed with toluene, or toluene is added to the reaction solution. The resin solution obtained in this way is then heated at 80°C or higher and below the boiling point of toluene by 0.5°C.
Heat and stir for more than an hour. After this, the resin solution is allowed to stand at the same temperature.

Separate into upper and lower layers. This lower layer consists of a viscous or slightly viscous liquid containing toluene and a toluene-containing tr bisphenol A novolac resin, and the upper layer consists of a bisphenol A monomer and a small amount of a formaldehyde reactant having two bisphenol A molecules in the molecule. This is a toluene solution in which is dissolved. Further, this separation can also be performed forcibly using a centrifugal separator. After separating and collecting the lower layer, toluene is distilled off to obtain the bisphenol A novolak 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, toluene becomes a viscous substance absorbed by the bisphenol A novolak resin,
If it exceeds 400 weights, the relatively low molecular weight molecular weight of the bisphenol A novolac resin will be dissolved in the toluene in the upper layer, resulting in a decrease in yield.

When there is a large excess, it becomes a homogeneous solution of toluene. The second step is 2
If the process is carried out once, usually two bisphenol A novolac resins according to the present invention can be obtained.

Depending on the case, the process may be repeated 92 times or more. 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 obtained bisphenol A novolak can be adjusted by adjusting the treatment conditions.

The bisphenol A novolac resin thus obtained can be used as it is without removing the neutralized salt contained therein, or after the neutralized salt is removed by hot water treatment or the like.

The solvent used in the second step is toluene, but 2
Other solvents such as benzene, xylene, etc. cannot achieve the objective.

In addition, if you only want to produce bisphenol A novolac 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, bisphenol A Since there are four sites capable of reacting with formaldehyde, it gels during synthesis and cannot be used in practice. In addition, even if the reaction is carried out with care to prevent gelation, it is not possible to obtain a product that satisfies the essential requirements of the bisphenol A novolac resin of the present invention, and 2 a large amount of molecular species with a molecular weight exceeding 20,000 is produced. In particular, the compatibility with epoxy resins becomes poor.

Note that the bisphenol A novolak resin according to the present invention may contain phenols other than bisphenol A as its phenol component within a range that meets the object of the present invention. Examples of such phenols include cresol and phenol, which are used together with bisphenol A during the production.

The bisphenol A novolac resin according to the present invention is useful as a curing agent for epoxy resins, and is used for manufacturing laminates and the like.

(Example) Next, two examples of the present invention will be shown.

Example 1 1I fitted with Dean Stark oil/water separator, thermometer and stirrer! Bisphenol A 2289 (1.0 mol), 80-thiparaformaldehyde 22.59 (0.6 mol in terms of formaldehyde) and toluene 171 g were placed in a glass four-bottle flask, and the temperature was raised while stirring. When the temperature inside the flask reached 80°C, 1.5 g of oxalic acid dihydrate as a catalyst was added, and stirring was continued at 89°C for 3 hours. After this, the temperature inside the flask was set to 105℃,
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 1 s and 7 mJ. This amount is
It corresponds to the total amount of water contained in W paraformaldehyde, water content in oxalic acid dihydrate, and 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, the stirring was stopped and the two reaction solutions were separated into two layers, a light liquid and a heavy liquid. The light liquid was removed by decantation to obtain a single heavy liquid. Toluene 4 to this heavy liquid
After adding 009 and stirring for 30 minutes under toluene reflux, stirring was stopped and the mixture was separated into two layers again, and the 9 heavy liquid (lower layer) was separated and collected. This was a slightly viscous liquid. From this, toluene was removed using an evaporator, and the pale yellow resin [:A
) 1329 was obtained.

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 column used at this time was GE
LPACK-R420゜R430 and R440 (both trade names of Hitachi Chemical Co., Ltd., using porous styrene-divinylbenzene copolymer particles as column packing material) were connected in series one by one, and tetrahydrofuran was used as the eluent, and detection was performed using tetrahydrofuran as the eluent. A differential refractometer was used as the instrument, and the flow rate was 1.75.
mJ/min. 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, the integrated intensity A of the peak based on the methyl group of the bisphenol A component appearing at 1.5 ppm and 3.75
It is determined from the integrated intensity F of the peak based on the methylene group of bound formaldehyde appearing in ppm by 2 formula % formula %).

The above results are shown in Table 1.

Example 2 In Example 1, the amount of 80-chiparaformaldehyde used was 30 g (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.

Toluene 2009 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 again.

Toluene was removed from the thus obtained heavy liquid using an evaporator to obtain 178 g of a pale yellow resin CB).

Table 1 shows the physical properties of this resin [B] measured in the same manner as in Example 1.

Example 3 The reaction proceeded according to Example 1 to obtain a double liquid. Next, toluene 2009 was processed into a double heavy liquid, and after stirring for 30 minutes under toluene reflux, the stirring was stopped, the light liquid and the heavy liquid were separated, and the light liquid was removed by decantation to obtain the heavy liquid.
I returned 9 times.

Toluene was removed from the thus obtained heavy liquid using an evaporator to obtain pale yellow resin [C]749.

Table 1 shows the physical properties of this resin [C] measured in the same manner as in Example 1.

Comparative Example 1 In Example 1, toluene was removed using an evaporator from the toluene solution neutralized by adding triethanolamine to obtain pale yellow resin [D:] 23.19.

Table 1 shows the physical properties of this resin CD), which were measured in the same manner as in Example 1. Moreover, the GPC chromatogram of resin [D] is shown in FIG.

Comparative Example 2 In Example 1, the stool amount of 80 tiparaformaldehyde was 33.8 g (0.90 mol in terms of formaldehyde).
The reaction proceeded in the same manner as in Example 1, except that triethanolamine was used for neutralization. Toluene was removed from this reaction solution using an evaporator to obtain pale yellow resin (E) 2359.

Table 1 shows the physical properties of this resin [E] measured in the same manner as in Example 1.

[Creating a calibration curve]

A calibration curve for molecular weight determination by GPC was created as follows.

That is, the resin [C] obtained in Example 3 was subjected to GPC measurement to obtain a chromatogram. This chromatogram is shown as graph 1 in FIG. In this chromatogram, peaks 2 to 8 are compounds of the following general formula [I] in which n is 0 to 6, respectively, and when n is O, it is a bisphenol A monomer.

0H (7'i:, L, where B is two hydrogens ortho to one hydroxyl group of the bisphenol monomer, or one hydrogen ortho to both hydroxyl groups. indicates a divalent residue excluding a total of two hydrogens, and n is O or 1
(is an integer of ~6) Here, the molecular weight of each compound where n corresponds to 0 to 6 is as follows.

When n is O, 228° . When 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 6, it is 1670.

Next, the elution time (minutes) of each compound was plotted on the horizontal axis and the molecular weight was plotted on a logarithmic scale on the vertical axis, and based on this, a calibration curve was determined as shown in FIG.

As is clear from FIG. 4, the calibration curve shows clear linearity.

Reference example 1 Epicote 828 (trade name of Shell Chemical Company).

Bisphenol Am epoxy resin, epoxy equivalent weight 190
1100 parts by weight, curing agent 6 obtained in Examples or Comparative Examples
After thoroughly mixing 1 part by weight at 130°C, 2-ethyl-
Add 0.5 parts by weight of 4-methylimidazole and heat to 170°C.
It was heated and cured for 2 hours.

A heat resistance test was conducted on the obtained cured product.

The results are shown in Table 2.

As heat resistance tests, glass transition temperature and JISK
The heat distortion temperature was measured based on 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.

Reference Example 2 100 parts by weight of an epoxy resin (epoxy equivalent: 410) obtained by reacting 100 parts by weight of Epicoat 828 and 63 parts by weight of tetrabromobisphenol A in the presence of 0.1 part by weight of tetramethylammonium chloride, resin as a curing agent [A/] or resin CD'131 weight 1m and 1
Pheno was prepared by dissolving 0.7 parts by weight of -cyanoethyl-2-phenymidazole in 120 parts by weight of methyl ethyl ketone. The gel time of this pheno was measured. Measure the gel time immediately after making the phenol or at 23
After one month of storage at 150°C, the time (seconds) until pheno gelatinized on a hot plate at 150°C was measured.

In addition, after making the above-mentioned phenol, glass cloth (glass cloth whose surface is treated with epoxy silane and made of glass fiber),
Thickness 0.18mm, Nitto Boseki G-9020-BZG)
A prepreg was prepared by impregnating 52 parts by weight of pheno as a solid content into 100 parts by weight.

This prepreg was dried for 10 minutes in a drying oven at 70 to 110°C.

The appearance of this dried prepreg was visually observed.

In addition, 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 observed.

Furthermore, the dried prepreg was measured at 150° C. using a differential scanning calorimeter.
The time from the start to the end of heat generation of the dried prepreg was measured when the prepreg was heated to a temperature of 9°C.

Furthermore, 15 sheets of the above dried prepreg and 6 sheets of 35 μm copper foil were laminated for every 3 sheets of prepreg (however, 2 sheets were on the front and back sides), heated at 130°C for 15 minutes, and then heated at 150°C for 15 minutes. A laminate was obtained by press molding for 1 minute at a pressure of 40 kg/a112.

This laminate was left standing in a steam atmosphere at 121°C and a pressure of 2ks/am2 for 6 hours, and the weight increase was measured.
The hygroscopicity of the laminate was investigated.

On the other hand, - the laminate obtained above was drilled with a
Ten thousand holes were drilled, 200 of them were selected, and the smear occurrence rate was examined to determine the drillability.

Note that resin CB) was treated in the same manner as above.

A prepreg was created and its appearance was visually observed.

Table 3 shows the results of the above tests.

Table 3 Characteristics of Fes, Prepreg, and Laminate From the results in Table 3, it is clear that the gel time of Pheno immediately after creation and after storage for one month is higher than that of resin [D] when resin [A] is used as the curing agent. Compared to when it is used as a hardening agent, the change is smaller,
Excellent storage stability.

The fact that the prepreg has a translucent appearance and no whitened areas indicates that the epoxy resin and curing agent have excellent compatibility. In addition, a short time until the end of zero heat generation means that curing is completed in a short time. It can be seen that it is superior in comparison.

Further, from the volume resistance value 9, it can be seen that the laminate obtained using resin [A] as a curing agent has better electrical insulation than the laminate obtained using [in the resin] as a curing agent.

When resin [E] was used as a curing agent, the prepreg turned white. This is because although resin [E] contains 18.2% by weight of residual bisphenol A monomer, its weight average molecular weight is about the same as that of resin CB). This is because a relatively large number of molecular species exceeding 000 are present, resulting in poor compatibility with the epoxy resin.

(Effects of the Invention) The bisphenol A novolak resin according to the present invention is useful as a curing agent for epoxy resins, and has excellent compatibility with epoxy resins, and the cured epoxy resin obtained by using it as a curing agent has excellent heat resistance. The epoxy resin varnish containing this resin as a hardening agent has excellent storage stability and
Also. The prepreg obtained using this varnish has excellent curability and color stability. In addition, the laminate obtained from this prepreg exhibits good volume resistance, moisture absorption resistance, and drilling workability.

[Brief explanation of drawings]

Figure 1 shows the GPC chromatogram of resin CAI obtained in Example 1, Figure 2 shows the nuclear magnetic resonance spectrum of resin [A], and Figure 3 shows the GPC chromatogram of resin CD obtained in Comparative Example 1. 4 shows the GPC chromatogram and calibration curve of resin [C] obtained in Example 3. Explanation of symbols 1... GPC chromatogram of resin [C] 9... Calibration curve

Claims (1)

[Claims] 1. In bisphenol A novolac resin, bound formaldehyde is 0.7 per mole of phenol component.
-0.9 mol and a phenol monomer content of 10% by weight or less. 2. The bisphenol A novolac resin according to claim 1, which has a number average molecular weight of 600 to 2,000. 3. The bisphenol A novolac resin according to claim 1 or 2, which has a degree of dispersion of 2.2 or less.