JPH0674308B2 - Bisphenol A Novolac Resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel bisphenol A novolak resin.

(Prior Art) Conventionally, a novolak resin obtained by dehydration condensation of a phenol compound and formaldehyde in the presence of an acidic catalyst is well known, and a novolak resin obtained by using bisphenol A as the phenol compound is a bisphenol resin. Known as phenol A novolak resin. This is mainly used as a curing agent for an epoxy resin through a prepreg to manufacture a laminated board such as a circuit board.

Conventionally known bisphenol A novolak 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, dicyandiamide predominates as an epoxy resin curing agent in the production of laminates using epoxy resin.

Generally, a laminated board 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. Then, this resin varnish is impregnated into a glass cloth, and the solvent is evaporated in a dryer to form a prepreg. This prepreg is laminated in an appropriate amount, or further laminated with a copper foil and heat-cured under pressure. The laminated plate thus obtained is subjected to processing such as etching and drilling for circuit formation.

Further, in the laminated plate field, curability of the resin, heat resistance of the cured resin, drill workability of the laminated plate, moisture resistance, electrical characteristics and hue stability, stability of the resin varnish, etc. are mentioned as required items.

(Problems to be solved by the invention) When dicyandiamide is used as a curing agent for epoxy resin, the resin curability (high temperature heating is required), the heat resistance of the cured resin, the hue stability of the laminated plate, and the drill workability are improved. Due to its inferior surface, it is expected to use a bisphenol A novolak resin, which has excellent curability, to remedy such drawbacks.

Therefore, as a result of various studies on the bisphenol A novolak resin known by the present inventors, the following was found.

That is, when the conventionally known bisphenol A novolak resin was used, there were no particular problems with respect to drilling workability, hue stability and electrical characteristics of the laminated plate,
(1) Insufficient curability of resin (lower temperature than dicyandiamide, but not sufficient at relatively high temperature), (2) Poor heat resistance of cured resin, (3) Storage stability of resin varnish It has poor properties (short pot life) and (4) poor compatibility with epoxy resin, which leads to whitening of the prepreg and insufficient curing.

(Means for Solving Problems) The present invention provides a novel bisphenol A novolak resin and solves the above problems.

That is, in the present invention, in the bisphenol A novolak resin, the bound formaldehyde is 0.7 to 0.9 mol with respect to 1 mol of bisphenol A, the content of the bisphenol A monomer is 10% by weight or less, and the number average molecular weight is Is 600
A bisphenol A novolak resin represented by the following general formula [I] having a dispersity of 2.2 or less at 2,000.

(In the formula, B is two hydrogens in the ortho position with respect to one hydroxyl group of the bisphenol A monomer, or one hydrogen in the ortho position with respect to both hydroxyl groups, and two hydrogens in total. N represents the number of repeating units, which represents the removed divalent residue, and is an integer selected so that the number average molecular weight of the bisphenol A novolak resin is 600 to 2,000) Bisphenol A novolak according to the present invention The resin has 0.7 to 0.9 mol of bound formaldehyde with respect to 1 mol of the phenol (bisphenol A) component in the resin. 0.7
If it is less than the molar amount, the content of the phenol (bisphenol A) monomer will increase or the number average molecular weight will decrease, so that the curability and heat resistance will decrease. 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 to 1 mole of the phenol (bisphenol A) component is the peak of 1.5 ppm based on the methyl group in the bisphenol A component of the bisphenol A novolak resin nuclear magnetic resonance spectrum and the bisphenol A component. It is calculated from the area intensity ratio of the 3.75 ppm peak based on the methylene group formed by the addition condensation of formaldehyde. The solvent in this measurement, dimethyl sulfoxide (provided that all the hydrogens of the methyl group is deuterium, DMSO-d ₆₎ to use.

The bisphenol A novolak resin according to the present invention has a phenol (bisphenol A) monomer content of 10% by weight or less. If this content exceeds 10% by weight, curability and heat resistance of the cured resin deteriorate.

In addition, a phenol (bisphenol A) component (including bisphenol A monomer contained in the resin)
The storage stability of the resin varnish is poor unless the number of moles of bound formaldehyde and the content of the phenol (bisphenol A) monomer relative to 1 mole are within the above ranges.

The bisphenol A novolak resin according to the present invention 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 decreases, and when it exceeds 2,000, the compatibility with the epoxy resin deteriorates.

The bisphenol A novolak resin according to the present invention has a dispersity of 2.2 or less. When the dispersity is within this range, it has the effects of preventing a partial progress of the curing reaction during prepreg drying and preventing the coloring of the laminate by lowering the curing temperature. Here, the polydispersity is the ratio of weight average molecular weight / number average molecular weight. In the present invention, the weight average molecular weight and the number average molecular weight are obtained by gel permeation chromatography. The calibration curve shows the compound having 2 to 7 bisphenol A components in the reaction product obtained by reacting bisphenol monomer (molecular weight 228), 1 mol of bisphenol A and 0.4 to 0.8 mol of formaldehyde under an acidic catalyst. Use what you created. The eluent is tetrahydrofuran, the flow rate is 1.7 ml for 1 minute, the temperature is 38 ° C, and the pressure is 48 kg / cm ² .

The bisphenol A novolak resin according to the present invention can be manufactured as follows.

Formaldehyde 0.4-to 1 mol of bisphenol A
0.8 mol is reacted in an aromatic solvent such as benzene, xylene, and toluene in the presence of an acidic catalyst (first step). Then, the obtained resin and charged bisphenol A
25 to 400% by weight of toluene was mixed with the mixture, and the mixture was stirred at a temperature of 80 ° C or higher and below the boiling point of toluene for 0.5 hours or longer.
When it is allowed to stand at that temperature, it is separated into two layers, so that the lower layer (a viscous or slightly viscous liquid containing toluene and bisphenol A novolak resin) is separated, and toluene is removed therefrom (second step). .

Each step will be described in more detail.

In the first step, formaldehyde is 0.4 to 0.8 mol based on 1 mol of bisphenol A. If it is less than 0.4 mol, the amount of unreacted bisphenol A increases, and it becomes difficult to make the bound formaldehyde to be 0.7 mol or more per mol of the bisphenol A component in the finally obtained resin. Also, if it exceeds 0.8 mol%, gelation may occur during the reaction and the molecular species with a molecular weight of more than 20,000 will be generated more often, and the compatibility of the finally obtained resin with the epoxy resin tends to decrease, and This increases the number average molecular weight and the degree of dispersion. Formaldehyde can be used in the form of paraformaldehyde, formalin aqueous solution, α-polyoxymethylene, or the like. The aromatic solvent preferably forms an azeotropic composition with water. The amount used is 20-100% by weight with respect to the charged bisphenol A.
Is preferred. Further, it is preferable to use toluene as the aromatic solvent because the second step can be carried out after the first step. As the acidic catalyst, there can be used those which are usually used for the production of phenol novolak resin such as mineral acids such as sulfuric acid and hydrochloric acid, organic acids such as paratoluenesulfonic acid and oxalic acid, and the amount of the used catalyst is 0.1 to 2% by weight relative to phenol A is preferred. The reaction temperature is 70 to 90 ° C for 1.5 to 4 hours, the addition reaction of formaldehyde to bisphenol A is mainly performed, and then the temperature is raised to 100 ° C or higher to the reflux temperature or lower to perform dehydration condensation. It is preferable to react. In this case, it is preferable that the condensation water is removed while the reaction is continued until no condensation water is produced. This time is usually 3 to 5 hours. After that, an alkali is added to the reaction solution in an amount equivalent to that of the acid catalyst to neutralize the acid catalyst. Examples of the alkali include lithium hydroxide, sodium hydroxide, potassium hydroxide, triethanolamine, morpholine and the like. In this way, the reaction solution obtained in the first step is subjected to the second step after the solvent is removed by distillation or the like (the reaction solution may be left as it is when toluene is used as the solvent).

In the second step, the resin and toluene obtained in the first step are mixed or toluene is added to the reaction solution so that the content of toluene in the charged bisphenol A is 25 to 400% by weight. 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 hour or longer. After that, the resin solution is allowed to stand at the temperature to separate it into upper and lower layers. The lower layer is composed of a viscous or slightly viscous liquid material containing toluene and a bisphenol A novolak resin containing toluene, and the upper layer contains a bisphenol A monomer and a small amount of bisphenol A in a molecule.
This is a toluene solution in which a formaldehyde reaction product having a unit is dissolved. Moreover, this separation can also be forcedly separated using a centrifuge. After separating and collecting the lower layer, the bisphenol A novolak resin according to the present invention can be obtained by removing toluene by distillation. In the second step, if the amount of toluene is less than 25% by weight with respect to the charged bisphenol A, it becomes a viscous substance in which the toluene is absorbed by the bisphenol A novolak resin, and 400% by weight is obtained.
If it exceeds, the relatively low molecular weight molecular species of the bisphenol A novolak resin will be dissolved in the upper layer of toluene, and the yield will be lowered. If the second step is performed once, the bisphenol A according to the present invention is usually used.
Although a novolak resin can be obtained, it may be repeated twice or more depending on the case. In this case, the amount of toluene mentioned above is based on the amount of resin.

By adjusting the treatment conditions in the second step, the number average molecular weight and dispersity of the obtained bisphenol A novolak can be adjusted.

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

The solvent used in the second step is toluene,
For example, other solvents such as benzene and xylene cannot achieve the purpose.

If only bisphenol A novolak resin containing a small amount of bisphenol A monomer is produced, it is possible to mix bisphenol A and formaldehyde in almost equimolar amounts to increase the reaction rate. Since there are four sites of formaldehyde reaction in bisphenol A, it gels during synthesis and cannot be used in practice. Further, even if the reaction is carried out with care so that gelation does not occur, it is not possible to obtain the bisphenol A novolak resin of the present invention that satisfies the essential requirements, and a large amount of molecular species having a molecular weight of more than 20,000 is obtained. It has a poor compatibility with the epoxy resin.

The bisphenol A novolak resin according to the present invention may contain, as its phenol component, phenols other than bisphenol A 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 novolak resin according to the present invention is useful as a curing agent for epoxy resins and is used for manufacturing laminated boards and the like.

(Example) Next, the Example of this invention is shown.

Example 1 Bisphenol A 228 g (1.0 mol), 80% paraformaldehyde 22.5 g was placed in a 1 glass four-necked flask equipped with a Dean-Stark oil / water separator, a thermometer and a stirrer.
(0.6 mol of formaldehyde) and 171 g of toluene were charged and the temperature was raised with stirring. The temperature in the flask is 80
When the temperature reached ℃, 1.5 g of catalyst oxalic acid dihydrate was added, and
Stirring was continued at 0 ° C. for 3 hours. Then, the temperature inside the flask was set to 105 ° C., the toluene was refluxed, and the water azeotropically flowing out was removed to the outside of the system. The toluene reflux was continued until the water flowed out. At this time, the temperature inside the flask was 113 ° C, and the total amount of water removed was 15.7 ml. This amount corresponds to the water content in 80% paraformaldehyde, the water content in oxalic acid dihydrate and the total amount of condensed water to be generated. The reaction solution at this time was a uniform solution.

Then, triethanolamine was added for neutralization, 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, it separates into two layers, a light liquid (upper layer) and a heavy liquid (lower layer). After the temperature was raised, the mixture was stirred for 30 minutes, the stirring was stopped, and the reaction solution was separated into two layers, a light solution and a heavy solution. The light liquid was removed by decantation to obtain a heavy liquid.
To this heavy liquid, 400 g of toluene was added, and the mixture was stirred under reflux of toluene for 30 minutes. After that, the stirring was stopped and the mixture was separated into two layers again. This was a slightly viscous liquid.
From this, toluene was removed by an evaporator to obtain 132 g of a pale yellow resin [A].

The softening point of the obtained resin was determined by the ring and ball method. The residual bisphenol A monomer and the molecular weight contained in the resin were measured using gel permeation chromatography (GPC). GELPACK is used as the separation column at this time.
-R420, R430 and R440 (all are trade names of Hitachi Chemical Co., Ltd., using porous styrene-divinylbenzene copolymer particles as column packing material) are 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 1.75 ml / min. The chromatogram obtained at this time is shown in FIG. The calibration curve used to calculate the molecular weight is shown below.

The bound formaldehyde number f per mol of the 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 the bound formaldehyde appearing at 3.75 ppm, the formula f = (F / 2) / (A / 6).

The above results are shown in Table 1.

Example 2 The reaction was carried out in the same manner as in Example 1 except that the amount of 80% paraformaldehyde used was 30 g (0.8 mol of formaldehyde conversion) and the amount of toluene used was 115 g, and the light liquid was used. A heavy liquid was obtained by removal.

To this heavy liquid, 200 g of toluene was added, and after stirring for 30 minutes under reflux of toluene, the stirring was stopped, the light liquid and the heavy liquid were separated, and the light liquid was removed by decantation to obtain a heavy liquid. Then, this operation was repeated once again.

Toluene was removed from the heavy liquid thus obtained by an evaporator to obtain 178 g of a pale yellow resin [B].

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

Example 3 The reaction was carried out according to Example 1 to obtain a heavy liquid. Then, add 200 g of toluene to the heavy liquid, stir under reflux of toluene for 30 minutes, stop stirring, separate into light liquid and heavy liquid, and remove the light liquid by decantation to obtain heavy liquid. Was repeated 4 times.

Toluene was removed from the thus obtained heavy liquid by an evaporator to obtain 74 g of pale yellow resin [C].

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 from the toluene solution neutralized by adding triethanolamine by an evaporator to obtain 23.1 g of pale yellow resin [D].

Table 1 shows the physical properties of this resin [D] measured in the same manner as in Example 1. The GPC chromatogram of resin [D] is shown in FIG.

Comparative Example 2 The reaction was carried out in the same manner as in Example 1 except that the amount of 80% paraformaldehyde used was 33.8 g (0.90 mol of formaldehyde), and triethanolamine was added to neutralize the reaction. . Toluene was removed from this reaction solution by an evaporator to give 235 g of pale yellow resin [E]
Got

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

[Creation of calibration curve]

A calibration curve for determining the molecular weight by GPC was prepared as follows.

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

(However, in the formula, B is two hydrogens in the ortho position to one hydroxyl group of the bisphenol A monomer, or one hydrogen in the ortho position to both hydroxyl groups, and two hydrogens in total. The divalent residue removed is shown, and n is 0 or an integer of 1 to 6) Here, the molecular weight of each compound in which n corresponds to 0 to 6 is as follows.

n is 0, 228, n is 1, 469, n is 2, 709, n is 3, 949, n is 4, 1190, n is 5, 1430, n is When it is 6, it is 1670.

Then, the elution time (minutes) of each compound was plotted on the horizontal axis and the molecular weight was plotted on the vertical axis on a logarithmic scale. Based on this plot, a calibration curve 9 was obtained as shown in FIG.

As is clear from FIG. 4, the calibration curve 9 shows clear linearity.

Reference Example 1 100 parts by weight of Epicoat 828 (trade name of Ciel Chemical Co., bisphenol A type epoxy resin, epoxy equivalent 190),
After thoroughly mixing 61 parts by weight of the curing agent obtained in the examples or comparative examples at 130 ° C., 2-ethyl-4-methylimidazole.
5 parts by weight was added and heated at 170 ° C. for 2 hours to cure.

A heat resistance test was performed on the obtained cured product. The results are shown in Table 2.

Heat resistance tests include glass transition temperature and JIS K 7207
(1983), the heat distortion temperature was measured. The glass transition point was the temperature at which the coefficient of thermal expansion was measured when the coefficient of thermal expansion was measured using a thermomechanical tester.

Reference Example 2 100 parts by weight of Epikote 828 and 63 parts by weight of tetrabromobisphenol A were mixed with tetramethylammonium chloride 0.1.
100 parts by weight of an epoxy resin (epoxy equivalent 410) obtained by reacting in the presence of parts by weight, 31 parts by weight of resin [A] or resin [D] as a curing agent, and 0.7 part by weight of 1-cyanoethyl-2-phenylimidazole A part was dissolved in 120 parts by weight of methyl ethyl ketone to prepare a varnish. About this varnish,
The gel time was measured. The gel time was measured by measuring the time (seconds) until the varnish gelated on the hot plate at 150 ° C immediately after the varnish was prepared or after being stored at 23 ° C for 1 month.

After the above varnish was prepared, 100 parts by weight of the glass cloth (glass cloth of which the surface was treated with epoxysilane, thickness 0.18 mm, G-9020-BZG, Nitto Boseki Co., Ltd.) was used as a solid content of the varnish. 52 parts by weight was impregnated to prepare a prepreg.

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

The appearance of this dried prepreg was visually observed.

Also, heat and cure the dried prepreg for 2 hours at 170 ℃,
The change in hue of the prepreg at this time was visually examined.

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

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

This laminate was allowed to stand for 6 hours at 121 ° C. in a steam atmosphere having a pressure of 2 kg / cm ² , and the weight increase was measured to examine the hygroscopicity of the laminate.

On the other hand, 10,000 holes were drilled in the laminated plate obtained above with a 1 mmφ drill, 200 of them were selected, the smear occurrence rate was examined, and the drill workability was judged.

For resin [E], a prepreg was prepared in the same manner as above, and the appearance was visually observed.

The results of the above tests are shown in Table 3.

As is clear from the results in Table 3, the gel time immediately after the varnish was prepared and after storage for 1 month was different when the resin [A] was used as the curing agent than when the resin [D] was used as the curing agent. Is small and has excellent storage stability. The semi-transparent appearance of the prepreg and the absence of whitening indicate that the epoxy resin and curing agent have excellent compatibility. Further, the fact that the time until the end of heat generation is short means that the curing is completed in a short time. In this respect, when the resin [A] is used as the curing agent, the resin [D] is used as the curing agent. It turns out that it is superior to the time.

Further, from the volume resistance value, it can be seen that the laminated board obtained by using the resin [A] as a curing agent is superior in electrical insulation property to the laminated board obtained by using the resin [D] as a curing agent.

When the resin [E] was used as the curing agent, the prepreg was whitened. This is because even though the resin [E] contains 18.2% by weight of the residual bisphenol A monomer, the weight average molecular weight is about the same as that of the resin [B]. This is because the compatibility with epoxy resins is poor because there are relatively many molecular species.

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

[Brief description of drawings]

1 is a GPC chromatogram of the resin [A] obtained in Example 1, FIG. 2 is a nuclear magnetic resonance spectrum of the resin [A], and FIG. 3 is a resin [D] obtained in Comparative Example 1. The GPC chromatogram of Fig. 4 and Fig. 4 show the GPC chromatogram and the calibration curve of the resin [C] obtained in Example 3. Explanation of code 1 …… GPC chromatogram of resin [C] 9 …… Calibration curve

Continuation of front page (56) Reference JP-A-58-204015 (JP, A) JP-A-61-138614 (JP, A) JP-A-54-163995 (JP, A)

Claims (1)

[Claims] 1. In the bisphenol A novolak resin, the bound formaldehyde is 0.7 to 0.9 mol per 1 mol of bisphenol A, the content of the bisphenol A monomer is 10% by weight or less, and the number average molecular weight is 600 to. 2,000
And a bisphenol A novolac resin represented by the following general formula [I] having a dispersity of 2.2 or less. (In the formula, B is two hydrogens in the ortho position with respect to one hydroxyl group of the bisphenol A monomer or one hydrogen in the ortho position with respect to both hydroxyl groups, and two hydrogens in total are excluded. Represents a divalent residue, and n, which represents the number of repeating units, is an integer selected so that the number average molecular weight of the bisphenol A novolak resin is 600 to 2,000).