JPH07292049A - Cured phenol resin product - Google Patents

Abstract

PURPOSE:To obtain a cured phenol resin product excellent in impact resistance by subjecting phenol and formaldehyde to condensation so as to give a condensate with specified cross-link density and glass transition temperature. CONSTITUTION:The objective cured phenol resin product is a condensate of phenol and formaldehyde, has a logarithm (log rho) of cross-link density rho (mol/ cm<3>) of $1.8 to 1.2 and a glass transition temperature Tg of 170 deg.C or higher, and is produced e.g. by cross-linking a high-molecular prepolymer formed by the condensation of phenol and formaldehyde and thermally treating the cross- linked prepolymer to a suitable degree for obtaining a cross-link density and a glass transition point each in a specified range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cured product of a phenol resin having excellent impact resistance.

[0002]

2. Description of the Related Art Phenolic resins are widely used as industrial materials because they have good heat resistance, flame retardancy, electrical characteristics, and are economical. However, in recent years, the performance requirements for phenolic resins have become more sophisticated, and it has been particularly desired to improve impact resistance.

The brittleness of the cured product of the phenol resin is due to the rigidity of the molecule due to the dense three-dimensional crosslinked structure.
Therefore, it is considered effective to improve the impact resistance by not raising the crosslink density of the cured product so much.

In general, a cured product of a phenol resin is produced by a method of polymerizing a low molecular compound such as resole or novolac and crosslinking the polymer at the same time. In such a production method, as a method for obtaining a cured product without increasing the crosslinking density so much, a method of curing at low temperature with resole or a method of shortening the curing time is considered, and with novolac, the addition amount of the curing agent is reduced. Methods etc. are considered.

However, although the cured product of a low crosslink density phenol resin obtained by such a method is slightly superior in impact resistance to the cured product having a high crosslink density,
The absolute value of impact resistance is still not as high as expected (eg 14 kgf · cm / cm ² or more). Furthermore, the obtained phenol resin cured product has poor heat resistance and low bending strength. This is because in the cross-linking reaction using low molecular compounds such as resole and novolac as reaction raw materials, the entire cured product is not microscopically and uniformly cross-linked, but rather a dense cross-linked microgel and a coarse cross-linked part. Is believed to be formed. That is, when a low cross-linking density cured product is obtained by the method as described above, the coarse portion of the cross-linking in the cured product is particularly increased, so the impact resistance does not increase so much and the heat resistance It is also believed that the bending strength will decrease.

When the low cross-linking density cured product obtained by the above-mentioned method is subjected to heat treatment, the cross-linking density is increased, and there is a tendency that impact resistance is slightly improved together with improvement in heat resistance and bending strength. However, if the heat treatment exceeds a certain level, the rigidity of the molecule increases, and the impact resistance decreases.

[0007]

DISCLOSURE OF THE INVENTION As a result of intensive studies conducted by the present inventors in view of the above-mentioned circumstances, a phenol resin cured product having a specific crosslink density and a specific glass transition point has excellent impact resistance. It was found that the present invention has been completed, and an object of the present invention is to provide a cured phenol resin product having excellent impact resistance.

[0008]

The above object of the present invention is a condensate of phenol and formaldehyde, the crosslink density ρ (mol / cm ³ ) of which has a logarithm (log ρ) of -1.
It is achieved by a phenol resin cured product, which has a glass transition point Tg of 170 ° C. or higher and a glass transition point Tg of 8 to −1.2.

The glass transition point Tg in the present invention is, for example, a phenol measured by using a dynamic viscoelasticity measuring device DMS110 (manufactured by Seiko Denshi Kogyo Co., Ltd.) at a bending mode, a frequency of 1 Hz and a heating rate of 2 ° C./min. It is a value obtained as the temperature at which the loss energy (tan δ) in the temperature dispersion of the dynamic viscoelasticity of the resin cured product becomes maximum.

The crosslink density ρ or its logarithm (logρ) in the present invention is obtained by the following method, and the glass transition point Tg is 200 ° C. or higher or 200 ° C.
The method of obtaining is slightly different depending on whether it is less than.

(1) In the case of a cured product having a glass transition point Tg of less than 200 ° C .: In the temperature dispersion curve of the storage elastic modulus (E ′) obtained by the above dynamic viscoelasticity measurement, the following formula ρ = E ′ / 3φRT [Wherein E ′ is a storage elastic modulus (Pa) at a temperature 30 ° C. higher than the glass transition point, φ is a front coefficient (= 1), R is
Is a gas constant, 8.31 (J / K · mol), and T is a value in which a temperature 30 ° C. higher than the glass transition point is represented by an absolute temperature (K). ] To obtain.

(2) In the case of a cured product having a glass transition point Tg of 200 ° C. or higher: Tg of 2 is obtained from cured products having different crosslinking densities obtained by changing curing conditions from the same kind of phenol resin.
Select 10 or more of those below 00 ° C, and select T for each cured product.
Plot g against the logarithm of crosslink density (log ρ) (eg, as in FIG. 1). The log ρ is calculated by substituting the Tg of the cured product into the relational expression Tg = K ₁ log ρ + K ₂ obtained by using the least squares method.

The method for calculating the crosslink density in the above (1) is described in a known document (Takashi Kamon, et al .: Polymer Chemistry, 30 , 279 (197).
3)). In addition, (2) above
The theory that the glass transition point Tg and the logarithm of the crosslinking density ρ in the homologous bridged polymer shown in Fig. 3 have a linear relationship is described by Kyoichi Shibayama in the literature (Polymer Chemistry, 18 , 183).
(1961)).

The cured product of the phenol resin of the present invention has a logarithm (log ρ) of the crosslinking density ρ (mol / cm ³ ) of -1.8.
Within the range of -1.2, and the glass transition point is 170.
℃ or above. When the log ρ is smaller than -1.8, the molecular weight is not sufficiently high, so that the impact resistance is low, and when the log ρ is larger than -1.2, the crosslink is dense and the molecular rigidity is high. Impact resistance is reduced.

Further, even if the logarithm (logρ) of the crosslink density ρ (mol / cm ³ ) is within the range of -1.8 to -1.2, the cured product having a glass transition point of less than 170 ° C. has impact resistance The nature is small. It is considered that this is because the uniformity of the crosslink density is low, and the rough portion of the crosslink points becomes a defect to reduce the heat resistance and the impact resistance.

In order to produce the cured product of the phenol resin of the present invention, it is preferable to use a polymer prepolymer which is a condensation product of phenols and aldehyde as the raw material phenol resin. The cured product of the phenol resin of the present invention can be obtained by subjecting the reaction product obtained by cross-linking the polymer prepolymer to an appropriate heat treatment.

Examples of the above-mentioned raw material phenol resin include powdery phenol resin obtained by the method described in Japanese Patent Publication No. 62-30211.
It is not particularly limited to this. The method for producing a powdery phenolic resin disclosed in the above publication is as follows.

That is, (1) the following composition, hydrochloric acid concentration 5 to 28% by weight, formaldehyde concentration 3
In a hydrochloric acid-formaldehyde bath having a total concentration of hydrochloric acid and formaldehyde of 15 to 40% by weight, (2) the following bath ratio = (weight of hydrochloric acid-formaldehyde bath) / weight of phenols (3) contacting the phenols with a hydrochloric acid-formaldehyde bath while maintaining the bath ratio to be at least 8 or more, and making this contact produce cloudiness after the phenols contact with the bath, After that, at least pink granular or powdery solid matter is formed, and the temperature in the reaction system is maintained at 45 ° C. or lower during this contact.

The properties of the powdery phenolic resin obtained by the above method are as follows: (1) the polystyrene reduced weight average molecular weight by GPC is 3000 or more, and (2) the number of methylene bonds per benzene ring is 0.9-1. 2, the number of hydroxymethyl groups per (3) benzene ring is 0.05 to
0.20. As such a thing, what is marketed as brand name Bell Pearl S (made by Kanebo) can be specifically mentioned. This powdery phenolic resin is a polymer compound and has a hydroxymethyl group, which is a crosslinkable functional group, so that it is thermosetting.

The cured product obtained by the crosslinking reaction of the powdery phenolic resin obtained by the above method has a lower crosslinking density than the ordinary phenolic resin cured product formed from resole or novolac.

The crosslink density of the above cured phenol resin is
It can be easily changed by controlling the number of hydroxymethyl groups of the powdery phenolic resin, the temperature and time during curing, or the temperature and time during heat treatment. In particular, the heat treatment conditions have a large influence on controlling both the crosslink density and the glass transition point, so that when the phenol resin cured product is produced, the crosslinking density and the glass transition point of the obtained cured product are the above-mentioned present invention. It is necessary to pay sufficient attention so that it is within the range of.

In order to obtain the cured product of the phenol resin of the present invention, the high molecular weight prepolymer of the phenol resin was used as the reaction raw material in the above-mentioned method. However, when resole or novolak was used as the reaction raw material, the entire cured product was uniform. Is extremely difficult to crosslink, and for example, when the glass transition point is 170 ° C. or higher by heat treatment, log ρ is usually −1.
It will be 1 or more. However, even if a resole or novolak is used, if the entire cured product undergoes a cross-linking reaction extremely uniformly and the cross-linking density and the glass transition point are within the constitutional requirements of the present invention, the same effect as the present invention can be obtained. You should be able to.

The phenol resin cured product of the present invention alone,
Alternatively, it can be used as a molded product having excellent heat resistance and impact resistance by being combined with a reinforcing fiber such as glass fiber or carbon fiber or various inorganic fillers, and is also useful as a coating material or a binder.

[0024]

The present invention will be described in detail below with reference to examples.
In addition, before that, the measuring method of various physical-property values in this specification is described.

<Impact strength> Using a rectangular test piece cut out from a cured product of a phenol resin, according to JIS-K-7111 (No. 1 test piece, notched, flatwise),
It was measured by the Charpy impact test.

<Weight Average Molecular Weight> GPC (Waters)
It was determined by measuring with ALG / GPC 150C, manufactured by the company. THF was used as an eluent, and a molecular weight calibration curve was prepared by measuring polystyrene as a standard substance.

<Bonding and Number of Functional Groups> The amount of methylene bonds and hydroxymethyl groups of the resin was quantified from the ¹ H-NMR spectrum of a sample obtained by acetylating a phenol resin prepolymer with pyridine / acetic anhydride. That is, the number of methylene linkages _{= (S 2/2) /} (S 1/3-S 3 /
2) The number of hydroxymethyl groups _{= (S 3/2-S} 4/2) /
In _{(S 1/3-S 3} /2) Equation, S ₁ is the peak area of the [delta] values 1.80～2.50Ppm (attributable to COC H ₃₎ S ₂ is [delta] value from 3.00 to 4 .10 ppm peak area (attributed to PhC H ₂ Ph) S ₃ has a δ value of 4.65-5.07 ppm peak area (attributed to PhC H ₂ OAc, PhC H ₂ OCH ₂ OAc) S ₄ is δ peak area values 5.07～5.40Ppm (attributable to PhCH ₂ OC H ₂ OAc)

Examples 1 to 20, Comparative Examples 1 to 7 Various powdery phenol resin prepolymers as shown in Table 1 were molded at a molding temperature of 170 ° C. and a molding pressure of 200 kgf / c.
Compression molding was performed under the conditions of m ² and molding time of 20 minutes. The obtained molded product was heat-treated for various times in a hot air dryer adjusted to 180 ° C. to obtain a phenol resin cured product.

[0029]

[Table 1]

In the case of a cured product having a Tg of 200 ° C. or lower, its crosslink density was obtained from the temperature dispersion of the storage elastic modulus obtained from the dynamic viscoelasticity measurement, using the rubber state equation. FIG. 1 shows the Tg of each cured product plotted against the logarithm of the crosslinking density. From these data, using the method of least squares, T
When the relationship between g and the crosslink density is obtained, Tg = 143 × lo
A linear expression of gρ + 428 was obtained.

In the case of a cured product having a Tg of 200 ° C. or higher, each Tg was substituted into this formula to obtain the logarithm log ρ of the crosslinking density.

Crosslink density, glass transition point,
And the impact strength was as shown in Table 2. Further, FIG. 2 is a graph in which the respective impact strengths are plotted against the logarithm of the crosslinking density. The cured product of the phenol resin having a log ρ within the range of −1.8 to −1.2 and a Tg of 170 ° C. or higher had high impact resistance.

[0033]

[Table 2]

Comparative Examples 8 to 10 As a raw material phenol resin, novolak (trade name: resin top PSK2320, manufactured by Gunei Chemical Industry Co., Ltd., weight average molecular weight 1500, 0.8 methylene bonds, 0 hydroxymethyl groups) was used and crosslinked. Hexamethylenetetramine in the amount shown in Table 3 was added as an agent, and the mixture was kneaded with a hot roll and then pulverized to obtain a molding material. These were compression-molded and heat-treated under the same conditions as in the above-mentioned examples to obtain a phenol resin cured product. The characteristic values of these cured products were as shown in Table 3.

[0035]

[Table 3]

Regarding the crosslink density ρ, all cured products have l
Although o g ρ was in the range of −1.8 to −1.2, the glass transition point Tg did not reach 170 ° C., and the impact resistance of the cured product was small.

[0037]

EFFECTS OF THE INVENTION The cured phenol resin product of the present invention has a specific crosslink density and a specific glass transition point, and therefore is crosslinked extremely uniformly. Therefore, the cured phenol resin product of the present invention has excellent heat resistance. At the same time, it has extremely excellent impact resistance that has never been seen before. Further, the phenol resin cured product of the present invention can be used as a molded product having excellent heat resistance and excellent impact resistance by combining with other reinforcing fibers such as carbon fiber and various inorganic fillers, and coating. It is also extremely useful as a material and binder.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between crosslink density (logρ) and glass transition point Tg.

FIG. 2 is a graph showing the relationship between crosslink density (logρ) and impact strength.

Claims (1)

[Claims] 1. A condensate of phenol and formaldehyde, which has a logarithm (l) of a crosslinking density ρ (mol / cm ³ ).
ogρ) is -1.8 to -1.2 and the glass transition point T is
A cured product of a phenol resin, wherein g is 170 ° C. or higher.